Introduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" This NASA image is a composite of several satellite-based views of Earth. To make the whole-Earth image, NASA scientists combine observations of different parts of the planet. (credit: NASA/GSFC/NOAA/USGS) 

Viewed from space, Earth offers no clues about the diversity of life it harbors. The first forms of life on Earth are thought be microorganisms that existed for billions of years in the ocean before plants and animals appeared. The mammals, birds, and flowers that we see in modern times are mostly recent species, originating 130 to 200 million years ago. In fact, only in the last 200,000 years have humans started looking like we do today. 

Organisms evolve in response to each other. One of the best examples is disease causing organisms, which have to adapt to overcome the defenses of the organisms they infect. One such organism that has evolved to specialize in infection in humans is Plasmodium , the organism that causes malaria. Biologists use the process of science to learn about the world and the organisms living in it. For example, people have suspected for quite some time that people with blood type O are less likely to die from severe malaria. Now, a team of scientists have been able to explain why. By examining data from several experiments, and by using both inductive and deductive reasoning, the scientists concluded that A and B type blood reacts with a protein excreted by Plasmodium . This reaction causes severe illness. However, type O blood does not react with the protein. You can read more about the response of type A and B blood groups to infection by Plasmodium . 

Introduce the concept of unity and diversity of life. There are so many varieties of organisms and, yet, the cell is the basic unit of life. The fundamental structures and life processes of cells are similar; but, how these cells are utilized in different organisms is hugely varied and reflects adaptation of the organism to its environment. The many differences between species accumulated over long periods of time. Students are often unfamiliar with geological time scales. 

The malaria example was chosen because malaria has been one of the most pervasive and widespread human disease. Therefore, through much of human history, malaria has been a strong force of natural selection on humans. Human genetics has evolved in response to this selection pressure, as with the example of resistance among O-type blood groups described in the introduction. Further examples can also be found here .The Science of Biology The Science of Biology 

In this section, you will explore the following questions: What are the characteristics shared by the natural sciences? What are the steps of the scientific method? Connection for AP courses 

Biology is the science that studies living organisms and their interactions with one another and with their environment. The process of science attempts to describe and understand the nature of the universe by rational means. Science has many fields; those fields related to the physical world, including biology, are considered natural sciences. All of the natural sciences follow the laws of chemistry and physics. For example, when studying biology, you must remember living organisms obey the laws of thermodynamics while using free energy and matter from the environment to carry out life processes that are explored in later chapters, such as metabolism and reproduction. 

Two types of logical reasoning are used in science: inductive reasoning and deductive reasoning. Inductive reasoning uses particular results to produce general scientific principles. Deductive reasoning uses logical thinking to predict results by applying scientific principles or practices. The scientific method is a step-by-step process that consists of: making observations, defining a problem, posing hypotheses, testing these hypotheses by designing and conducting investigations, and drawing conclusions from data and results. Scientists then communicate their results to the scientific community. Scientific theories are subject to revision as new information is collected. 

The content presented in this section supports the Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives merge Essential Knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP Exam questions. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models Learning Objectives 2.3 The student is able to predict how changes in free energy availability affect organisms, populations and ecosystems. 

Illustrate uses of the scientific method in class. Divide students in groups of four or five and ask them to design experiments to test the existence of connections they have wondered about. Help them decide if they have a working hypothesis that can be tested and falsified. Give examples of hypotheses that are not falsifiable because they are based on subjective assessments. They are neither observable nor measurable. For example, birds like classical music is based on a subjective assessment. Ask if this hypothesis can be modified to become a testable hypothesis. Stress the need for controls and provide examples such as the use of placebos in pharmacology. 

Biology is not a collection of facts to be memorized. Biological systems follow the law of physics and chemistry. Give as an example gas laws in chemistry and respiration physiology. Many students come with a 19th century view of natural sciences; each discipline is in its own sphere. Give as an example, bioinformatics which uses organism biology, chemistry, and physics to label DNA with light emitting reporter molecules (Next Generation sequencing). These molecules can then be scanned by light-sensing machinery, allowing huge amounts of information to be gathered on their DNA. Bring to their attention the fact that the analysis of these data is an application of mathematics and computer science. 

For more information about next generation sequencing, check out this informative review . Formerly called blue-green algae, these (a) cyanobacteria, shown here at 300x magnification under a light microscope, are some of Earth s oldest life forms. These (b) stromatolites along the shores of Lake Thetis in Western Australia are ancient structures formed by the layering of cyanobacteria in shallow waters. (credit a: modification of work by NASA; credit b: modification of work by Ruth Ellison; scale-bar data from Matt Russell) 

What is biology? In simple terms, biology is the study of living organisms and their interactions with one another and their environments. This is a very broad definition because the scope of biology is vast. Biologists may study anything from the microscopic or submicroscopic view of a cell to ecosystems and the whole living planet ( [link] ). Listening to the daily news, you will quickly realize how many aspects of biology are discussed every day. For example, recent news topics include Escherichia coli ( [link] ) outbreaks in spinach and Salmonella contamination in peanut butter. Other subjects include efforts toward finding a cure for AIDS, Alzheimer s disease, and cancer. On a global scale, many researchers are committed to finding ways to protect the planet, solve environmental issues, and reduce the effects of climate change. All of these diverse endeavors are related to different facets of the discipline of biology. Escherichia coli ( E. coli ) bacteria, seen in this scanning electron micrograph, are normal residents of our digestive tracts that aid in the absorption of vitamin K and other nutrients. However, virulent strains are sometimes responsible for disease outbreaks. (credit: Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU) The Process of Science 

Biology is a science, but what exactly is science? What does the study of biology share with other scientific disciplines? Science (from the Latin scientia , meaning knowledge ) can be defined as knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method. It becomes clear from this definition that the application of the scientific method plays a major role in science. The scientific method is a method of research with defined steps that include experiments and careful observation. 

The steps of the scientific method will be examined in detail later, but one of the most important aspects of this method is the testing of hypotheses by means of repeatable experiments. A hypothesis is a suggested explanation for an event, which can be tested. Although using the scientific method is inherent to science, it is inadequate in determining what science is. This is because it is relatively easy to apply the scientific method to disciplines such as physics and chemistry, but when it comes to disciplines like archaeology, psychology, and geology, the scientific method becomes less applicable as it becomes more difficult to repeat experiments. 

These areas of study are still sciences, however. Consider archeology even though one cannot perform repeatable experiments, hypotheses may still be supported. For instance, an archeologist can hypothesize that an ancient culture existed based on finding a piece of pottery. Further hypotheses could be made about various characteristics of this culture, and these hypotheses may be found to be correct or false through continued support or contradictions from other findings. A hypothesis may become a verified theory. A theory is a tested and confirmed explanation for observations or phenomena. Science may be better defined as fields of study that attempt to comprehend the nature of the universe. Natural Sciences 

What would you expect to see in a museum of natural sciences? Frogs? Plants? Dinosaur skeletons? Exhibits about how the brain functions? A planetarium? Gems and minerals? Or, maybe all of the above? Science includes such diverse fields as astronomy, biology, computer sciences, geology, logic, physics, chemistry, and mathematics ( [link] ). However, those fields of science related to the physical world and its phenomena and processes are considered natural sciences . Thus, a museum of natural sciences might contain any of the items listed above. The diversity of scientific fields includes astronomy, biology, computer science, geology, logic, physics, chemistry, mathematics, and many other fields. (credit: Image Editor /Flickr) 

There is no complete agreement when it comes to defining what the natural sciences include, however. For some experts, the natural sciences are astronomy, biology, chemistry, earth science, and physics. Other scholars choose to divide natural sciences into life sciences , which study living things and include biology, and physical sciences , which study nonliving matter and include astronomy, geology, physics, and chemistry. Some disciplines such as biophysics and biochemistry build on both life and physical sciences and are interdisciplinary. Natural sciences are sometimes referred to as hard science because they rely on the use of quantitative data; social sciences that study society and human behavior are more likely to use qualitative assessments to drive investigations and findings. 

Not surprisingly, the natural science of biology has many branches or subdisciplines. Cell biologists study cell structure and function, while biologists who study anatomy investigate the structure of an entire organism. Those biologists studying physiology, however, focus on the internal functioning of an organism. Some areas of biology focus on only particular types of living things. For example, botanists explore plants, while zoologists specialize in animals. Scientific Reasoning 

One thing is common to all forms of science: an ultimate goal to know. Curiosity and inquiry are the driving forces for the development of science. Scientists seek to understand the world and the way it operates. To do this, they use two methods of logical thinking: inductive reasoning and deductive reasoning. 

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. This type of reasoning is common in descriptive science. A life scientist such as a biologist makes observations and records them. These data can be qualitative or quantitative, and the raw data can be supplemented with drawings, pictures, photos, or videos. From many observations, the scientist can infer conclusions (inductions) based on evidence. Inductive reasoning involves formulating generalizations inferred from careful observation and the analysis of a large amount of data. Brain studies provide an example. In this type of research, many live brains are observed while people are doing a specific activity, such as viewing images of food. The part of the brain that lights up during this activity is then predicted to be the part controlling the response to the selected stimulus, in this case, images of food. The lighting up of the various areas of the brain is caused by excess absorption of radioactive sugar derivatives by active areas of the brain. The resultant increase in radioactivity is observed by a scanner. Then, researchers can stimulate that part of the brain to see if similar responses result. 

Deductive reasoning or deduction is the type of logic used in hypothesis-based science. In deductive reason, the pattern of thinking moves in the opposite direction as compared to inductive reasoning. Deductive reasoning is a form of logical thinking that uses a general principle or law to forecast specific results. From those general principles, a scientist can extrapolate and predict the specific results that would be valid as long as the general principles are valid. Studies in climate change can illustrate this type of reasoning. For example, scientists may predict that if the climate becomes warmer in a particular region, then the distribution of plants and animals should change. These predictions have been made and tested, and many such changes have been found, such as the modification of arable areas for agriculture, with change based on temperature averages. 

Both types of logical thinking are related to the two main pathways of scientific study: descriptive science and hypothesis-based science. Descriptive (or discovery) science , which is usually inductive, aims to observe, explore, and discover, while hypothesis-based science , which is usually deductive, begins with a specific question or problem and a potential answer or solution that can be tested. The boundary between these two forms of study is often blurred, and most scientific endeavors combine both approaches. The fuzzy boundary becomes apparent when thinking about how easily observation can lead to specific questions. For example, a gentleman in the 1940s observed that the burr seeds that stuck to his clothes and his dog s fur had a tiny hook structure. On closer inspection, he discovered that the burrs gripping device was more reliable than a zipper. He eventually developed a company and produced the hook-and-loop fastener popularly known today as Velcro. Descriptive science and hypothesis-based science are in continuous dialogue. The Scientific Method 

Biologists study the living world by posing questions about it and seeking science-based responses. This approach is common to other sciences as well and is often referred to as the scientific method. The scientific method was used even in ancient times, but it was first documented by England s Sir Francis Bacon (1561 1626) ( [link] ), who set up inductive methods for scientific inquiry. The scientific method is not exclusively used by biologists but can be applied to almost all fields of study as a logical, rational problem-solving method. Sir Francis Bacon (1561 1626) is credited with being the first to define the scientific method. (credit: Paul van Somer) 

The scientific process typically starts with an observation (often a problem to be solved) that leads to a question. Let s think about a simple problem that starts with an observation and apply the scientific method to solve the problem. One Monday morning, a student arrives at class and quickly discovers that the classroom is too warm. That is an observation that also describes a problem: the classroom is too warm. The student then asks a question: Why is the classroom so warm? Proposing a Hypothesis 

Recall that a hypothesis is a suggested explanation that can be tested. To solve a problem, several hypotheses may be proposed. For example, one hypothesis might be, The classroom is warm because no one turned on the air conditioning. But there could be other responses to the question, and therefore other hypotheses may be proposed. A second hypothesis might be, The classroom is warm because there is a power failure, and so the air conditioning doesn t work. 

Once a hypothesis has been selected, the student can make a prediction. A prediction is similar to a hypothesis but it typically has the format If . . . then . . . . For example, the prediction for the first hypothesis might be, If the student turns on the air conditioning, then the classroom will no longer be too warm. Testing a Hypothesis 

A valid hypothesis must be testable. It should also be falsifiable , meaning that it can be disproven by experimental results. Importantly, science does not claim to prove anything because scientific understandings are always subject to modification with further information. This step openness to disproving ideas is what distinguishes sciences from non-sciences. The presence of the supernatural, for instance, is neither testable nor falsifiable. To test a hypothesis, a researcher will conduct one or more experiments designed to eliminate one or more of the hypotheses. Each experiment will have one or more variables and one or more controls. A variable is any part of the experiment that can vary or change during the experiment. The control group contains every feature of the experimental group except it is not given the manipulation that is hypothesized about. Therefore, if the results of the experimental group differ from the control group, the difference must be due to the hypothesized manipulation, rather than some outside factor. Look for the variables and controls in the examples that follow. To test the first hypothesis, the student would find out if the air conditioning is on. If the air conditioning is turned on but does not work, there should be another reason, and this hypothesis should be rejected. To test the second hypothesis, the student could check if the lights in the classroom are functional. If so, there is no power failure and this hypothesis should be rejected. Each hypothesis should be tested by carrying out appropriate experiments. Be aware that rejecting one hypothesis does not determine whether or not the other hypotheses can be accepted; it simply eliminates one hypothesis that is not valid ( see this figure ). Using the scientific method, the hypotheses that are inconsistent with experimental data are rejected. 

While this warm classroom example is based on observational results, other hypotheses and experiments might have clearer controls. For instance, a student might attend class on Monday and realize she had difficulty concentrating on the lecture. One observation to explain this occurrence might be, When I eat breakfast before class, I am better able to pay attention. The student could then design an experiment with a control to test this hypothesis. 

In hypothesis-based science, specific results are predicted from a general premise. This type of reasoning is called deductive reasoning: deduction proceeds from the general to the particular. But the reverse of the process is also possible: sometimes, scientists reach a general conclusion from a number of specific observations. This type of reasoning is called inductive reasoning, and it proceeds from the particular to the general. Inductive and deductive reasoning are often used in tandem to advance scientific knowledge ( see this figure ) Think About It 

Almost all plants use water, carbon dioxide, and energy from the sun to make sugars. Think about what would happen to plants that don t have sunlight as an energy source or sufficient water. What would happen to organisms that depend on those plants for their own survival? 

Make a prediction about what would happen to the organisms living in a rain forest if 50% of its trees were destroyed. How would you test your prediction? 

Use this example as a model to make predictions. Emphasize there is no rigid scientific method scheme. Active science is a combination of observations and measurement. Offer the example of ecology where the conventional scientific method is not always applicable because researchers cannot always set experiments in a laboratory and control all the variables. Possible answers: Ask students: What happens to plants if light intensity is low or if it is dark? The answer is that plants will soon die if they cannot have a source of energy. Ask students: What happens if plants have no water? The common answers will vary, from Plants dry out to Plants die which is the same end results. Without plants, what will happen to animals that feed on plants? The possible answers are animals will starve or animals will move away What happens to those animals who feed on the animals that feed on those animals? They will either die or migrate following the food trail. This is a good opportunity to show that the ecosystem is interconnected and extend the concepts to producers (the plants that absorb light energy), the primary consumers (herbivores), and secondary consumers (predators). 

Destruction of the rain forest affects the trees, the animals which feed on the vegetation, take shelter on the trees, and large predators which feed on smaller animals. Furthermore, because the trees positively affect rain through massive evaporation and condensation of water vapor, drought follows deforestation. 

Tell students a similar experiment on a grand scale may have happened in the past and introduce the next activity What killed the dinosaurs? 

Some predictions can be made and later observations can support or disprove the prediction. 

Ask, what killed the dinosaurs? Explain many scientists point to a massive asteroid crashing in the Yucatan peninsula in Mexico. One of the effects was the creation of smoke clouds and debris that blocked the Sun, stamped out many plants and, consequently, brought mass extinction. As is common in the scientific community, many other researchers offer divergent explanations. 

Go to this site for a good example of the complexity of scientific method and scientific debate. 

The scientific method consists of a series of well-defined steps. If a hypothesis is not supported by experimental data, a new hypothesis can be proposed. 

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Scientists use two types of reasoning, inductive and deductive reasoning, to advance scientific knowledge. As is the case in this example, the conclusion from inductive reasoning can often become the premise for inductive reasoning. 

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The scientific method may seem too rigid and structured. It is important to keep in mind that, although scientists often follow this sequence, there is flexibility. Sometimes an experiment leads to conclusions that favor a change in approach; often, an experiment brings entirely new scientific questions to the puzzle. Many times, science does not operate in a linear fashion; instead, scientists continually draw inferences and make generalizations, finding patterns as their research proceeds. Scientific reasoning is more complex than the scientific method alone suggests. Notice, too, that the scientific method can be applied to solving problems that aren t necessarily scientific in nature. Two Types of Science: Basic Science and Applied Science 

The scientific community has been debating for the last few decades about the value of different types of science. Is it valuable to pursue science for the sake of simply gaining knowledge, or does scientific knowledge only have worth if we can apply it to solving a specific problem or to bettering our lives? This question focuses on the differences between two types of science: basic science and applied science. 

Basic science or pure science seeks to expand knowledge regardless of the short-term application of that knowledge. It is not focused on developing a product or a service of immediate public or commercial value. The immediate goal of basic science is knowledge for knowledge s sake, though this does not mean that, in the end, it may not result in a practical application. 

In contrast, applied science or technology, aims to use science to solve real-world problems, making it possible, for example, to improve a crop yield, find a cure for a particular disease, or save animals threatened by a natural disaster ( [link] ). In applied science, the problem is usually defined for the researcher. After Hurricane Ike struck the Gulf Coast in 2008, the U.S. Fish and Wildlife Service rescued this brown pelican. Thanks to applied science, scientists knew how to rehabilitate the bird. (credit: FEMA) 

Some individuals may perceive applied science as useful and basic science as useless. A question these people might pose to a scientist advocating knowledge acquisition would be, What for? A careful look at the history of science, however, reveals that basic knowledge has resulted in many remarkable applications of great value. Many scientists think that a basic understanding of science is necessary before an application is developed; therefore, applied science relies on the results generated through basic science. Other scientists think that it is time to move on from basic science and instead to find solutions to actual problems. Both approaches are valid. It is true that there are problems that demand immediate attention; however, few solutions would be found without the help of the wide knowledge foundation generated through basic science. 

One example of how basic and applied science can work together to solve practical problems occurred after the discovery of DNA structure led to an understanding of the molecular mechanisms governing DNA replication. Strands of DNA, unique in every human, are found in our cells, where they provide the instructions necessary for life. During DNA replication, DNA makes new copies of itself, shortly before a cell divides. Understanding the mechanisms of DNA replication enabled scientists to develop laboratory techniques that are now used to identify genetic diseases, pinpoint individuals who were at a crime scene, and determine paternity. Without basic science, it is unlikely that applied science would exist. 

Another example of the link between basic and applied research is the Human Genome Project, a study in which each human chromosome was analyzed and mapped to determine the precise sequence of DNA subunits and the exact location of each gene. (The gene is the basic unit of heredity; an individual s complete collection of genes is his or her genome.) Other less complex organisms have also been studied as part of this project in order to gain a better understanding of human chromosomes. The Human Genome Project ( [link] ) relied on basic research carried out with simple organisms and, later, with the human genome. An important end goal eventually became using the data for applied research, seeking cures and early diagnoses for genetically related diseases. The Human Genome Project was a 13-year collaborative effort among researchers working in several different fields of science. The project, which sequenced the entire human genome, was completed in 2003. (credit: the U.S. Department of Energy Genome Programs (http://genomics.energy.gov)) 

While research efforts in both basic science and applied science are usually carefully planned, it is important to note that some discoveries are made by serendipity , that is, by means of a fortunate accident or a lucky surprise. Penicillin was discovered when biologist Alexander Fleming accidentally left a petri dish of Staphylococcus bacteria open. An unwanted mold grew on the dish, killing the bacteria. The mold turned out to be Penicillium , and a new antibiotic was discovered. Even in the highly organized world of science, luck when combined with an observant, curious mind can lead to unexpected breakthroughs. Reporting Scientific Work 

Whether scientific research is basic science or applied science, scientists must share their findings in order for other researchers to expand and build upon their discoveries. Collaboration with other scientists when planning, conducting, and analyzing results are all important for scientific research. For this reason, important aspects of a scientist s work are communicating with peers and disseminating results to peers. Scientists can share results by presenting them at a scientific meeting or conference, but this approach can reach only the select few who are present. Instead, most scientists present their results in peer-reviewed manuscripts that are published in scientific journals. Peer-reviewed manuscripts are scientific papers that are reviewed by a scientist s colleagues, or peers. These colleagues are qualified individuals, often experts in the same research area, who judge whether or not the scientist s work is suitable for publication. The process of peer review helps to ensure that the research described in a scientific paper or grant proposal is original, significant, logical, and thorough. Grant proposals, which are requests for research funding, are also subject to peer review. Scientists publish their work so other scientists can reproduce their experiments under similar or different conditions to expand on the findings. The experimental results must be consistent with the findings of other scientists. 

A scientific paper is very different from creative writing. Although creativity is required to design experiments, there are fixed guidelines when it comes to presenting scientific results. First, scientific writing must be brief, concise, and accurate. A scientific paper needs to be succinct but detailed enough to allow peers to reproduce the experiments. 

The scientific paper consists of several specific sections introduction, materials and methods, results, and discussion. This structure is sometimes called the IMRaD format. There are usually acknowledgment and reference sections as well as an abstract (a concise summary) at the beginning of the paper. There might be additional sections depending on the type of paper and the journal where it will be published; for example, some review papers require an outline. 

The introduction starts with brief, but broad, background information about what is known in the field. A good introduction also gives the rationale of the work; it justifies the work carried out and also briefly mentions the end of the paper, where the hypothesis or research question driving the research will be presented. The introduction refers to the published scientific work of others and therefore requires citations following the style of the journal. Using the work or ideas of others without proper citation is considered plagiarism . 

The materials and methods section includes a complete and accurate description of the substances used, and the method and techniques used by the researchers to gather data. The description should be thorough enough to allow another researcher to repeat the experiment and obtain similar results, but it does not have to be verbose. This section will also include information on how measurements were made and what types of calculations and statistical analyses were used to examine raw data. Although the materials and methods section gives an accurate description of the experiments, it does not discuss them. 

Some journals require a results section followed by a discussion section, but it is more common to combine both. If the journal does not allow the combination of both sections, the results section simply narrates the findings without any further interpretation. The results are presented by means of tables or graphs, but no duplicate information should be presented. In the discussion section, the researcher will interpret the results, describe how variables may be related, and attempt to explain the observations. It is indispensable to conduct an extensive literature search to put the results in the context of previously published scientific research. Therefore, proper citations are included in this section as well. 

Finally, the conclusion section summarizes the importance of the experimental findings. While the scientific paper almost certainly answered one or more scientific questions that were stated, any good research should lead to more questions. Therefore, a well-done scientific paper leaves doors open for the researcher and others to continue and expand on the findings. 

Review articles do not follow the IMRAD format because they do not present original scientific findings, or primary literature; instead, they summarize and comment on findings that were published as primary literature and typically include extensive reference sections. Section Summary 

Biology is the science that studies living organisms and their interactions with one another and their environments. Science attempts to describe and understand the nature of the universe in whole or in part by rational means. Science has many fields; those fields related to the physical world and its phenomena are considered natural sciences. 

Science can be basic or applied. The main goal of basic science is to expand knowledge without any expectation of short-term practical application of that knowledge. The primary goal of applied research, however, is to solve practical problems. 

Two types of logical reasoning are used in science. Inductive reasoning uses particular results to produce general scientific principles. Deductive reasoning is a form of logical thinking that predicts results by applying general principles. The common thread throughout scientific research is the use of the scientific method, a step-based process that consists of making observations, defining a problem, posing hypotheses, testing these hypotheses, and drawing one or more conclusions. The testing uses proper controls. Scientists present their results in peer-reviewed scientific papers published in scientific journals. A scientific research paper consists of several well-defined sections: introduction, materials and methods, results, and, finally, a concluding discussion. Review papers summarize the research done in a particular field over a period of time. Review Questions 

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[link] Glossary abstract opening section of a scientific paper that summarizes the research and conclusions applied science form of science that aims to solve real-world problems basic science science that seeks to expand knowledge and understanding regardless of the short-term application of that knowledge biology the study of living organisms and their interactions with one another and their environments conclusion section of a scientific paper that summarizes the importance of the experimental findings control part of an experiment that does not change during the experiment deductive reasoning form of logical thinking that uses a general inclusive statement to forecast specific results descriptive science (also, discovery science) form of science that aims to observe, explore, and investigate discussion section of a scientific paper in which the author interprets experimental results, describes how variables may be related, and attempts to explain the phenomenon in question falsifiable able to be disproven by experimental results hypothesis suggested explanation for an observation, which can be tested hypothesis-based science form of science that begins with a specific question and potential testable answers inductive reasoning form of logical thinking that uses related observations to arrive at a general conclusion introduction opening section of a scientific paper, which provides background information about what was known in the field prior to the research reported in the paper life science field of science, such as biology, that studies living things materials and methods section of a scientific paper that includes a complete description of the substances, methods, and techniques used by the researchers to gather data natural science field of science that is related to the physical world and its phenomena and processes peer-reviewed manuscript scientific paper that is reviewed by a scientist s colleagues who are experts in the field of study physical science field of science, such as geology, astronomy, physics, and chemistry, that studies nonliving matter plagiarism using other people s work or ideas without proper citation, creating the false impression that those are the author s original ideas results section of a scientific paper in which the author narrates the experimental findings and presents relevant figures, pictures, diagrams, graphs, and tables, without any further interpretation review article paper that summarizes and comments on findings that were published as primary literature science knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method scientific method method of research with defined steps that include observation, formulation of a hypothesis, testing, and confirming or falsifying the hypothesis serendipity fortunate accident or a lucky surprise theory tested and confirmed explanation for observations or phenomena variable part of an experiment that the experimenter can vary or changeThemes and Concepts of Biology Themes and Concepts of Biology 

By the end of this section, you will be able to: Identify and describe the properties of life Describe the levels of organization among living things Recognize and interpret a phylogenetic tree Connection for AP Courses 

The AP Biology curriculum is organized around four major themes called the Big Ideas that apply to all levels of biological organization from molecules and cells to populations and ecosystems. Each Big Idea identifies key concepts called Enduring Understandings, and Essential Knowledges, along with supporting examples. Simple descriptions define the focus of each Big Idea: Big Idea 1, Evolution; Big Idea 2, Energy and Homeostasis; Big Idea 3, Information and Communication; and Big Idea 4, Systems and Interactions. Evolution explains both the unity and diversity of life, Big Idea 1, and all organisms require energy and molecules to carry out life functions, such as growth and reproduction, Big Idea 2. Living systems also store, transmit, and respond to information, from DNA sequences to nerve impulses and behaviors, Big Idea 3. All biological systems interact, and these interactions result in emergent properties and characteristics unique to life, Big Idea 4. 

The redesigned AP Biology course also emphasizes the investigative practices that students should master. Scientific inquiry usually uses a series of steps to gain new knowledge. The scientific method begins with an observation and follows with a hypothesis to explain the observation; then experiments are conducted to test the hypothesis, gather results, and draw conclusions from data. The AP program has identified seven major categories of Science Practices, which can be described by short phrases: using representations and models to communicate information and solve problems; using mathematics appropriately; engaging in questioning; planning and implementing data collection strategies; analyzing and evaluating data; justifying scientific explanations; and connecting concepts. A Learning Objective merges content with one or more of the seven Science Practices. 

The information presented and the examples highlighted in this section support concepts and Learning Objectives outlined in Big Idea 1 of the AP Biology Curriculum. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.14 The student is able to pose scientific questions that correctly identify essential properties of share, core life processes that provide insights into the history of life on Earth. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.18 The student is able to evaluate evidence provided by a data set in conjunction with a phylogenetic tree or simply cladogram to determine evolutionary history and speciation. 

Biology is the science that studies life, but what exactly is life? This may sound like a silly question with an obvious response, but it is not always easy to define life. For example, a branch of biology called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they do not meet the criteria that biologists use to define life. Consequently, virologists are not biologists, strictly speaking. Similarly, some biologists study the early molecular evolution that gave rise to life; since the events that preceded life are not biological events, these scientists are also excluded from biology in the strict sense of the term. 

From its earliest beginnings, biology has wrestled with three questions: What are the shared properties that make something alive ? And once we know something is alive, how do we find meaningful levels of organization in its structure? And, finally, when faced with the remarkable diversity of life, how do we organize the different kinds of organisms so that we can better understand them? As new organisms are discovered every day, biologists continue to seek answers to these and other questions. Properties of Life 

All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, adaptation, growth and development, regulation, homeostasis, energy processing, and evolution. When viewed together, these nine characteristics serve to define life. Order A toad represents a highly organized structure consisting of cells, tissues, organs, and organ systems. (credit: Ivengo /Wikimedia Commons) 

Organisms are highly organized, coordinated structures that consist of one or more cells. Even very simple, single-celled organisms are remarkably complex: inside each cell, atoms make up molecules; these in turn make up cell organelles and other cellular inclusions. In multicellular organisms ( [link] ), similar cells form tissues. Tissues, in turn, collaborate to create organs (body structures with a distinct function). Organs work together to form organ systems. Sensitivity or Response to Stimuli The leaves of this sensitive plant ( Mimosa pudica ) will instantly droop and fold when touched. After a few minutes, the plant returns to normal. (credit: Alex Lomas) 

Organisms respond to diverse stimuli. For example, plants can bend toward a source of light, climb on fences and walls, or respond to touch ( [link] ). Even tiny bacteria can move toward or away from chemicals (a process called chemotaxis ) or light ( phototaxis ). Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response. 

Watch this video to see how plants respond to a stimulus from opening to light, to wrapping a tendril around a branch, to capturing prey. 

[link] Reproduction 

Single-celled organisms reproduce by first duplicating their DNA, and then dividing it equally as the cell prepares to divide to form two new cells. Multicellular organisms often produce specialized reproductive germline cells that will form new individuals. When reproduction occurs, genes containing DNA are passed along to an organism s offspring. These genes ensure that the offspring will belong to the same species and will have similar characteristics, such as size and shape. Growth and Development 

Organisms grow and develop following specific instructions coded for by their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species young ( [link] ) will grow up to exhibit many of the same characteristics as its parents. Although no two look alike, these kittens have inherited genes from both parents and share many of the same characteristics. (credit: Rocky Mountain Feline Rescue) Regulation 

Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, and cope with environmental stresses. Two examples of internal functions regulated in an organism are nutrient transport and blood flow. Organs (groups of tissues working together) perform specific functions, such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body. Homeostasis Polar bears ( Ursus maritimus ) and other mammals living in ice-covered regions maintain their body temperature by generating heat and reducing heat loss through thick fur and a dense layer of fat under their skin. (credit: longhorndave /Flickr) 

In order to function properly, cells need to have appropriate conditions such as proper temperature, pH, and appropriate concentration of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through homeostasis (literally, steady state ) the ability of an organism to maintain constant internal conditions. For example, an organism needs to regulate body temperature through a process known as thermoregulation. Organisms that live in cold climates, such as the polar bear ( [link] ), have body structures that help them withstand low temperatures and conserve body heat. Structures that aid in this type of insulation include fur, feathers, blubber, and fat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat. Energy Processing The California condor ( Gymnogyps californianus ) uses chemical energy derived from food to power flight. California condors are an endangered species; this bird has a wing tag that helps biologists identify the individual. (credit: Pacific Southwest Region U.S. Fish and Wildlife Service) 

All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and convert it into chemical energy in food; others use chemical energy in molecules they take in as food ( [link] ). Activity 

Select an ecosystem of your choice, such as a tropical rainforest, desert, or coral reef, and create a representation to show how several organisms found in the ecosystem interact with each other and the environment. Then, using similarities and differences among the organisms make a hypothesis about their relatedness. 

Consider the levels of organization of the biological world and create a diagram to place these items in order from the smallest level of organization to the most encompassing: skin cell, planet Earth, elephant, tropical rainforest, water molecule, liver, wolf pack, and oxygen atom. Justify the reason why you placed the items in the hierarchy that you did. Think About It 

Homeostasis the ability to stay the same is a feature shared by all living organisms. You go for a long walk on a hot day. Describe how homeostasis keeps your body healthy even though you are sweating profusely. Then describe an example of an adaptation that evolved in a desert plant or animal that allows them to survive in extreme temperatures. 

The first activity is an application of Learning Objective 1.16 and Science Practice 6.1 because the student is justifying the claim that organisms share many features that evolved in the past and are found among organisms today. 

The second activity is an application of Learning Objective 1.16 and Science Practice 6.1 because the student is justifying the claim that life on Earth today is organized into a hierarchy of features, from simple to complex, that evolved in the past. 

The Think about it section is an application of Learning Objective 1.14 and Science Practice 7.2 because students are describing an example of a process that is shared by all living organisms, despite the environment in which they are typically found. 

Ecosystems: Each system must have a common thread of producers fixing sun energy or acquiring energy from chemical reactions, feeding first consumers usually herbivores or decomposers, and second consumers that are predators. The ecosystem must provide shelter, access to food and stable environment. Answers will vary. 

Levels of organization from smallest to largest: Teach students to place the obvious answers first: atom as smallest and planet Earth at the top and then fill the gaps. 

From smallest to largest: 

Oxygen atom 

Water molecule 

Skin cell 

Liver 

Elephant 

Wolf pack 

Tropical rain forest 

Planet Earth 

Adaptation to dry conditions: Stress that animals and plants use general mechanisms to preserve water once the transition to dry land was made. Animals adapted to dry climates have thick skin layers to reduce water loss. Their urinary system is also adapted to concentrate urine, reducing water loss. Animals also respond to extreme heat behaviorally by going out at night or when the sun is low. Plants develop thick waxy layers that cover, leaves in the form of thorns and open stomata (pores) at night. 

Many adaptations are due to convergent evolution. The fins of dolphins are not derived from fins of fish. On the other hand, structures that look very different such as our hands and the wings of bats have the same core structure they are limbs with the same number and arrangement of bones but look different because they are adapted for different functions. Levels of Organization of Living Things 

Living things are highly organized and structured, following a hierarchy that can be examined on a scale from small to large. The atom is the smallest and most fundamental unit of matter. It consists of a nucleus surrounded by electrons. Atoms form molecules. A molecule is a chemical structure consisting of at least two atoms held together by one or more chemical bonds. Many molecules that are biologically important are macromolecules , large molecules that are typically formed by polymerization (a polymer is a large molecule that is made by combining smaller units called monomers, which are simpler than macromolecules). An example of a macromolecule is deoxyribonucleic acid (DNA) ( [link] ), which contains the instructions for the structure and functioning of all living organisms. All molecules, including this DNA molecule, are composed of atoms. (credit: brian0918 /Wikimedia Commons) Link to Learning 

Watch this video that animates the three-dimensional structure of the DNA molecule shown in this figure . 

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Some cells contain aggregates of macromolecules surrounded by membranes; these are called organelles . Organelles are small structures that exist within cells. Examples of organelles include mitochondria and chloroplasts, which carry out indispensable functions: mitochondria produce energy to power the cell, while chloroplasts enable green plants to utilize the energy in sunlight to make sugars. All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function in living organisms. (This requirement is why viruses are not considered living: they are not made of cells. To make new viruses, they have to invade and hijack the reproductive mechanism of a living cell; only then can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular. Cells are classified as prokaryotic or eukaryotic. Prokaryotes are single-celled or colonial organisms that do not have membrane-bound nuclei; in contrast, the cells of eukaryotes do have membrane-bound organelles and a membrane-bound nucleus. 

In larger organisms, cells combine to make tissues , which are groups of similar cells carrying out similar or related functions. Organs are collections of tissues grouped together performing a common function. Organs are present not only in animals but also in plants. An organ system is a higher level of organization that consists of functionally related organs. Mammals have many organ systems. For instance, the circulatory system transports blood through the body and to and from the lungs; it includes organs such as the heart and blood vessels. Organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms. 

All the individuals of a species living within a specific area are collectively called a population . For example, a forest may include many pine trees. All of these pine trees represent the population of pine trees in this forest. Different populations may live in the same specific area. For example, the forest with the pine trees includes populations of flowering plants and also insects and microbial populations. A community is the sum of populations inhabiting a particular area. For instance, all of the trees, flowers, insects, and other populations in a forest form the forest s community. The forest itself is an ecosystem. An ecosystem consists of all the living things in a particular area together with the abiotic, non-living parts of that environment such as nitrogen in the soil or rain water. At the highest level of organization ( see this figure ), the biosphere is the collection of all ecosystems, and it represents the zones of life on earth. It includes land, water, and even the atmosphere to a certain extent. The biological levels of organization of living things are shown. From a single organelle to the entire biosphere, living organisms are parts of a highly structured hierarchy. (credit organelles : modification of work by Umberto Salvagnin; credit cells : modification of work by Bruce Wetzel, Harry Schaefer/ National Cancer Institute; credit tissues : modification of work by Kilbad; Fama Clamosa; Mikael H ggstr m; credit organs : modification of work by Mariana Ruiz Villareal; credit organisms : modification of work by "Crystal"/Flickr; credit ecosystems : modification of work by US Fish and Wildlife Service Headquarters; credit biosphere : modification of work by NASA) 

[link] The Diversity of Life 

The fact that biology, as a science, has such a broad scope has to do with the tremendous diversity of life on earth. The source of this diversity is evolution , the process of gradual change during which new species arise from older species. Evolutionary biologists study the evolution of living things in everything from the microscopic world to ecosystems. 

The evolution of various life forms on Earth can be summarized in a phylogenetic tree ( [link] ). A phylogenetic tree is a diagram showing the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both. A phylogenetic tree is composed of nodes and branches. The internal nodes represent ancestors and are points in evolution when, based on scientific evidence, an ancestor is thought to have diverged to form two new species. The length of each branch is proportional to the time elapsed since the split. This phylogenetic tree was constructed by microbiologist Carl Woese using data obtained from sequencing ribosomal RNA genes. The tree shows the separation of living organisms into three domains: Bacteria, Archaea, and Eukarya. Bacteria and Archaea are prokaryotes, single-celled organisms lacking intracellular organelles. (credit: Eric Gaba; NASA Astrobiology Institute) 

Carl Woese and the Phylogenetic Tree In the past, biologists grouped living organisms into five kingdoms: animals, plants, fungi, protists, and bacteria. The organizational scheme was based mainly on physical features, as opposed to physiology, biochemistry, or molecular biology, all of which are used by modern systematics. The pioneering work of American microbiologist Carl Woese in the early 1970s has shown, however, that life on Earth has evolved along three lineages, now called domains Bacteria, Archaea, and Eukarya. The first two are prokaryotic cells with microbes that lack membrane-enclosed nuclei and organelles. The third domain contains the eukaryotes and includes unicellular microorganisms together with the four original kingdoms (excluding bacteria). Woese defined Archaea as a new domain, and this resulted in a new taxonomic tree ( see this figure ). Many organisms belonging to the Archaea domain live under extreme conditions and are called extremophiles. To construct his tree, Woese used genetic relationships rather than similarities based on morphology (shape). 

Woese s tree was constructed from comparative sequencing of the genes that are universally distributed, present in every organism, and conserved (meaning that these genes have remained essentially unchanged throughout evolution). Woese s approach was revolutionary because comparisons of physical features are insufficient to differentiate between the prokaryotes that appear fairly similar in spite of their tremendous biochemical diversity and genetic variability ( [link] ). The comparison of homologous DNA and RNA sequences provided Woese with a sensitive device that revealed the extensive variability of prokaryotes, and which justified the separation of the prokaryotes into two domains: bacteria and archaea. These images represent different domains. The (a) bacteria in this micrograph belong to Domain Bacteria, while the (b) extremophiles (not visible) living in this hot vent belong to Domain Archaea. Both the (c) sunflower and (d) lion are part of Domain Eukarya. (credit a: modification of work by Drew March; credit b: modification of work by Steve Jurvetson; credit c: modification of work by Michael Arrighi; credit d: modification of work by Leszek Leszcynski) 

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Phylogenetic trees can represent traits that are derived or lost due to evolution. One example is the absence of legs in some sea mammals. For example, Cetaceans are marine mammals that include toothed whales, such as dolphins and killer whales, and baleen whales, such as humpback whales. Cetaceans are descended from even-toed ungulates and share a common ancestry with the hippopotamus, cow, sheep, camel, and pig. 

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Use the diagram to ask the following questions: 

Which animal(s) are most closely related to a duck-billed platypus? Give your reasoning. 

Answer 

the American opossum, least number of common ancestors. 

Circle on one main lineage in the diagram the nodes in red, the tip of the trees in blue and the branches in red. 

Once bats were called flying mice. According to the tree, is this a valid characterization? 

Answer 

No, bats are more closely related to shrew and moles. 

Ask students the question, how did reptiles learn how to fly? 

For an exploration of the evolution of flight visit this site . 

Birds are not modern day dinosaurs. Birds evolved from dinosaurs. Many changes took place over time. Branches of Biological Study 

The scope of biology is broad and therefore contains many branches and subdisciplines. Biologists may pursue one of those subdisciplines and work in a more focused field. For instance, molecular biology and biochemistry study biological processes at the molecular and chemical level, including interactions among molecules such as DNA, RNA, and proteins, as well as the way they are regulated. Microbiology , the study of microorganisms, is the study of the structure and function of organisms that cannot be seen with the naked eye. It is quite a broad branch itself, and depending on the subject of study, there are also microbial physiologists, ecologists, and geneticists, among others. Forensic Scientist 

Forensic science is the application of science to answer questions related to the law. Biologists as well as chemists and biochemists can be forensic scientists. Forensic scientists provide scientific evidence for use in courts, and their job involves examining trace materials associated with crimes. Interest in forensic science has increased in the last few years, possibly because of popular television shows that feature forensic scientists on the job. Also, the development of molecular techniques and the establishment of DNA databases have expanded the types of work that forensic scientists can do. Their job activities are primarily related to crimes against people such as murder, rape, and assault. Their work involves analyzing samples such as hair, blood, and other body fluids and also processing DNA ( [link] ) found in many different environments and materials. Forensic scientists also analyze other biological evidence left at crime scenes, such as insect larvae or pollen grains. Students who want to pursue careers in forensic science will most likely be required to take chemistry and biology courses as well as some intensive math courses. This forensic scientist works in a DNA extraction room at the U.S. Army Criminal Investigation Laboratory at Fort Gillem, GA. (credit: United States Army CID Command Public Affairs) 

Another field of biological study, neurobiology , studies the biology of the nervous system, and although it is considered a branch of biology, it is also recognized as an interdisciplinary field of study known as neuroscience. Because of its interdisciplinary nature, this subdiscipline studies different functions of the nervous system using molecular, cellular, developmental, medical, and computational approaches. Researchers work on excavating dinosaur fossils at a site in Castell n, Spain. (credit: Mario Modesto) 

Paleontology , another branch of biology, uses fossils to study life s history ( [link] ). Zoology and botany are the study of animals and plants, respectively. Biologists can also specialize as biotechnologists, ecologists, or physiologists, to name just a few areas. This is just a small sample of the many fields that biologists can pursue. 

Biology is the culmination of the achievements of the natural sciences from their inception to today. Excitingly, it is the cradle of emerging sciences, such as the biology of brain activity, genetic engineering of custom organisms, and the biology of evolution that uses the laboratory tools of molecular biology to retrace the earliest stages of life on earth. A scan of news headlines whether reporting on immunizations, a newly discovered species, sports doping, or a genetically-modified food demonstrates the way biology is active in and important to our everyday world. Section Summary 

Biology is the science of life. All living organisms share several key properties such as order, sensitivity or response to stimuli, reproduction, growth and development, regulation, homeostasis, and energy processing. Living things are highly organized parts of a hierarchy that includes atoms, molecules, organelles, cells, tissues, organs, and organ systems. Organisms, in turn, are grouped as populations, communities, ecosystems, and the biosphere. The great diversity of life today evolved from less-diverse ancestral organisms over billions of years. A diagram called a phylogenetic tree can be used to show evolutionary relationships among organisms. 

Biology is very broad and includes many branches and subdisciplines. Examples include molecular biology, microbiology, neurobiology, zoology, and botany, among others. Review Questions 

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[link] Test Prep for AP Courses 

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[link] Glossary atom smallest and most fundamental unit of matter biochemistry study of the chemistry of biological organisms biosphere collection of all the ecosystems on Earth botany study of plants cell smallest fundamental unit of structure and function in living things community set of populations inhabiting a particular area ecosystem all the living things in a particular area together with the abiotic, nonliving parts of that environment eukaryote organism with cells that have nuclei and membrane-bound organelles evolution process of gradual change during which new species arise from older species and some species become extinct homeostasis ability of an organism to maintain constant internal conditions macromolecule large molecule, typically formed by the joining of smaller molecules microbiology study of the structure and function of microorganisms molecule chemical structure consisting of at least two atoms held together by one or more chemical bonds molecular biology study of biological processes and their regulation at the molecular level, including interactions among molecules such as DNA, RNA, and proteins neurobiology study of the biology of the nervous system organ collection of related tissues grouped together performing a common function organ system level of organization that consists of functionally related interacting organs organelle small structures that exist within cells and carry out cellular functions organism individual living entity paleontology study of life s history by means of fossils phylogenetic tree diagram showing the evolutionary relationships among various biological species based on similarities and differences in genetic or physical traits or both; in essence, a hypothesis concerning evolutionary connections population all of the individuals of a species living within a specific area prokaryote single-celled organism that lacks organelles and does not have nuclei surrounded by a nuclear membrane tissue group of similar cells carrying out related functions zoology study of animalsIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Atoms are the building blocks of molecules found in the universe air, soil, water, rocks . . . and also the cells of all living organisms. In this model of an organic molecule, the atoms of carbon (black), hydrogen (white), nitrogen (blue), oxygen (red), and sulfur (yellow) are shown in proportional atomic size. The silver rods indicate chemical bonds. (credit: modification of work by Christian Guthier) 

All matter, including living things, is made up of various combinations of elements. Some of the most abundant elements in living organisms include carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. These elements form the major biological molecules nucleic acids, proteins, carbohydrates, and lipids that are the fundamental components of living matter. Biologists study these important molecules to understand their unique structures which determine their specialized functions. 

All biological processes follow the laws of physics and chemistry. Therefore, in order to understand how biological systems work, it is important to understand the underlying physics and chemistry. For example, the flow of blood within the circulatory system follows the laws of physics regulating the modes of fluid flow. Chemical laws dictate the breakdown of large, complex food molecules into smaller molecules as well as their conversion to energy stored in adenosine triphosphate (ATP). Polar molecules, the formation of hydrogen bonds, and the resulting properties of water are key to understanding living processes. Recognizing the properties of acids and bases is important to understand various biological processes such as digestion. Therefore, the fundamentals of physics and chemistry are the foundation for gaining insight into biological processes. 

An example of how understanding of chemical processes can give insight to a biological process is recent research on seasonal affective disorder (SAD). This form of depression affects up to 10% of the population in the fall and winter. Symptoms include a tendency to overeat, oversleep, lack of energy, and difficulty concentrating on tasks. Now scientists have found out that not only may SAD be caused by a deficiency in vitamin D, but that it is more common in individuals with darker skin pigmentation. You can read more about it here . 

Before students begin this chapter, it is useful to review these concepts: Atoms consist of protons, neutrons, and electrons; Atoms are most stable when their outermost or valence electron shells contain the maximum number of electrons; Electrons can be transferred, shared, or cause charge disparities between atoms to create bonds, including ionic, covalent, and hydrogen bonds. Demonstrate how electrons can be transferred or shared to create bonds using a chemistry model kit or by drawing the atoms and electrons.Atoms, Isotopes, Ions, and Molecules: The Building Blocks Atoms, Isotopes, Ions, and Molecules: The Building Blocks 

In this section, you will explore the following questions: How does atomic structure determine the properties of elements, molecules, and matter? What are the differences among ionic bonds, covalent bonds, polar covalent bonds, and hydrogen bonds? Connection for AP Courses 

Living systems obey the laws of chemistry and physics. Matter is anything that occupies space and mass. The 92 naturally occurring elements have unique properties, and various combinations of them create molecules, which combine to form organelles, cells, tissues, organ system, and organisms. Atoms , which consist of protons, neutrons, and electrons, are the smallest units of matter that retain all their characteristics and are most stable when their outermost or valence electron shells contain the maximum number of electrons. Electrons can be transferred, shared, or cause charge disparities between atoms to create bonds, including ionic, covalent, and hydrogen bonds, as well as van del Waals interactions. Isotopes are different forms of an element that have different numbers of neutrons while retaining the same number of protons; many isotopes, such as carbon-14, are radioactive. 

The information presented and examples highlighted in this section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 2.8 The student is able to justify the selection of data regarding the types of molecules that an animal, plant, or bacterium will take up as necessary building blocks and excrete as waste products. 

At its most fundamental level, life is made up of matter. Matter is any substance that occupies space and has mass. Elements are unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances by ordinary chemical reactions. There are 118 elements, but only 92 occur naturally. The remaining elements are synthesized in laboratories and are unstable. 

Each element is designated by its chemical symbol, which is a single capital letter or, when the first letter is already taken by another element, a combination of two letters. Some elements follow the English term for the element, such as C for carbon and Ca for calcium. Other elements chemical symbols derive from their Latin names; for example, the symbol for sodium is Na, referring to natrium , the Latin word for sodium. 

The four elements common to all living organisms are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). In the non-living world, elements are found in different proportions, and some elements common to living organisms are relatively rare on the earth as a whole, as shown in [link] . For example, the atmosphere is rich in nitrogen and oxygen but contains little carbon and hydrogen, while the earth s crust, although it contains oxygen and a small amount of hydrogen, has little nitrogen and carbon. In spite of their differences in abundance, all elements and the chemical reactions between them obey the same chemical and physical laws regardless of whether they are a part of the living or non-living world. Approximate Percentage of Elements in Living Organisms (Humans) Compared to the Non-living World Element Life (Humans) Atmosphere Earth s Crust Oxygen (O) 65% 21% 46% Carbon (C) 18% trace trace Hydrogen (H) 10% trace 0.1% Nitrogen (N) 3% 78% trace The Structure of the Atom 

To understand how elements come together, we must first discuss the smallest component or building block of an element, the atom. An atom is the smallest unit of matter that retains all of the chemical properties of an element. For example, one gold atom has all of the properties of gold in that it is a solid metal at room temperature. A gold coin is simply a very large number of gold atoms molded into the shape of a coin and containing small amounts of other elements known as impurities. Gold atoms cannot be broken down into anything smaller while still retaining the properties of gold. 

An atom is composed of two regions: the nucleus , which is in the center of the atom and contains protons and neutrons, and the outermost region of the atom which holds its electrons in orbit around the nucleus, as illustrated in [link] . Atoms contain protons, electrons, and neutrons, among other subatomic particles. The only exception is hydrogen (H), which is made of one proton and one electron with no neutrons. Elements, such as helium, depicted here, are made up of atoms. Atoms are made up of protons and neutrons located within the nucleus, with electrons in orbitals surrounding the nucleus. 

Protons and neutrons have approximately the same mass, about 1.67 10 -24 grams. Scientists arbitrarily define this amount of mass as one atomic mass unit (amu) or one Dalton, as shown in [link] . Although similar in mass, protons and neutrons differ in their electric charge. A proton is positively charged whereas a neutron is uncharged. Therefore, the number of neutrons in an atom contributes significantly to its mass, but not to its charge. Electrons are much smaller in mass than protons, weighing only 9.11 10 -28 grams, or about 1/1800 of an atomic mass unit. Hence, they do not contribute much to an element s overall atomic mass. Therefore, when considering atomic mass, it is customary to ignore the mass of any electrons and calculate the atom s mass based on the number of protons and neutrons alone. Although not significant contributors to mass, electrons do contribute greatly to the atom s charge, as each electron has a negative charge equal to the positive charge of a proton. In uncharged, neutral atoms, the number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus. In these atoms, the positive and negative charges cancel each other out, leading to an atom with no net charge. 

Accounting for the sizes of protons, neutrons, and electrons, most of the volume of an atom greater than 99 percent is, in fact, empty space. With all this empty space, one might ask why so-called solid objects do not just pass through one another. The reason they do not is that the electrons that surround all atoms are negatively charged and negative charges repel each other. Protons, Neutrons, and Electrons Charge Mass (amu) Location Proton +1 1 nucleus Neutron 0 1 nucleus Electron 1 0 orbitals Atomic Number and Mass 

Atoms of each element contain a characteristic number of protons and electrons. The number of protons determines an element s atomic number and is used to distinguish one element from another. The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess. Together, the number of protons and the number of neutrons determine an element s mass number , as illustrated in this figure . Note that the small contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the mass number. Since an element s isotopes will have slightly different mass numbers, scientists also determine the atomic mass , which is the calculated mean of the mass number for its naturally occurring isotopes. Often, the resulting number contains a fraction. For example, the atomic mass of chlorine (Cl) is 35.45 because chlorine is composed of several isotopes, some (the majority) with atomic mass 35 (17 protons and 18 neutrons) and some with atomic mass 37 (17 protons and 20 neutrons). Carbon has an atomic number of six, and two stable isotopes with mass numbers of twelve and thirteen, respectively. Its atomic mass is 12.11. 

[link] Isotopes 

Isotopes are different forms of an element that have the same number of protons but a different number of neutrons. Some elements such as carbon, potassium, and uranium have naturally occurring isotopes. Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 (six protons and six neutrons). Carbon-14 contains six protons, eight neutrons, and six electrons; its atomic mass is 14 (six protons and eight neutrons). These two alternate forms of carbon are isotopes. Some isotopes may emit neutrons, protons, and electrons, and attain a more stable atomic configuration (lower level of potential energy); these are radioactive isotopes, or radioisotopes. Radioactive decay (carbon-14 losing neutrons to eventually become carbon-12) describes the energy loss that occurs when an unstable atom s nucleus releases radiation. 

Carbon Dating Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methane. Carbon-14 ( 14 C) is a naturally occurring radioisotope that is created in the atmosphere from atmospheric 14 N (nitrogen) by the addition of a neutron and the loss of a proton because of cosmic rays. This is a continuous process, so more 14 C is always being created. As a living organism incorporates 14 C initially as carbon dioxide fixed in the process of photosynthesis, the relative amount of 14 C in its body is equal to the concentration of 14 C in the atmosphere. When an organism dies, it is no longer ingesting 14 C, so the ratio between 14 C and 12 C will decline as 14 C decays gradually to 14 N by a process called beta decay the emission of electrons or positrons. This decay gives off energy in a slow process. 

After approximately 5,730 years, half of the starting concentration of 14 C will have been converted back to 14 N. The time it takes for half of the original concentration of an isotope to decay back to its more stable form is called its half-life. Because the half-life of 14 C is long, it is used to date formerly living objects such as old bones or wood. Comparing the ratio of the 14 C concentration found in an object to the amount of 14 C detected in the atmosphere, the amount of the isotope that has not yet decayed can be determined. On the basis of this amount, the age of the material, such as the pygmy mammoth shown in [link] , can be calculated with accuracy if it is not much older than about 50,000 years. Other elements have isotopes with different half lives. For example, 40 K (potassium-40) has a half-life of 1.25 billion years, and 235 U (Uranium 235) has a half-life of about 700 million years. Through the use of radiometric dating, scientists can study the age of fossils or other remains of extinct organisms to understand how organisms have evolved from earlier species. The age of carbon-containing remains less than about 50,000 years old, such as this pygmy mammoth, can be determined using carbon dating. (credit: Bill Faulkner, NPS) 

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To learn more about atoms, isotopes, and how to tell one isotope from another, visit this site and run the simulation. 

[link] The Periodic Table 

The different elements are organized and displayed in the periodic table . Devised by Russian chemist Dmitri Mendeleev (1834 1907) in 1869, the table groups elements that, although unique, share certain chemical properties with other elements. The properties of elements are responsible for their physical state at room temperature: they may be gases, solids, or liquids. Elements also have specific chemical reactivity , the ability to combine and to chemically bond with each other. 

In the periodic table, shown in [link] , the elements are organized and displayed according to their atomic number and are arranged in a series of rows and columns based on shared chemical and physical properties. In addition to providing the atomic number for each element, the periodic table also displays the element s atomic mass. Looking at carbon, for example, its symbol (C) and name appear, as well as its atomic number of six (in the upper left-hand corner) and its atomic mass of 12.11. The periodic table shows the atomic mass and atomic number of each element. The atomic number appears above the symbol for the element and the approximate atomic mass appears below it. 

The periodic table groups elements according to chemical properties. The differences in chemical reactivity between the elements are based on the number and spatial distribution of an atom s electrons. Atoms that chemically react and bond to each other form molecules. Molecules are simply two or more atoms chemically bonded together. Logically, when two atoms chemically bond to form a molecule, their electrons, which form the outermost region of each atom, come together first as the atoms form a chemical bond. Electron Shells and the Bohr Model 

It should be stressed that there is a connection between the number of protons in an element, the atomic number that distinguishes one element from another, and the number of electrons it has. In all electrically neutral atoms, the number of electrons is the same as the number of protons. Thus, each element, at least when electrically neutral, has a characteristic number of electrons equal to its atomic number. 

An early model of the atom was developed in 1913 by Danish scientist Niels Bohr (1885 1962). The Bohr model shows the atom as a central nucleus containing protons and neutrons, with the electrons in circular orbitals at specific distances from the nucleus, as illustrated in [link] . These orbits form electron shells or energy levels, which are a way of visualizing the number of electrons in the outermost shells. These energy levels are designated by a number and the symbol n. For example, 1n represents the first energy level located closest to the nucleus. The Bohr model was developed by Niels Bohrs in 1913. In this model, electrons exist within principal shells. An electron normally exists in the lowest energy shell available, which is the one closest to the nucleus. Energy from a photon of light can bump it up to a higher energy shell, but this situation is unstable, and the electron quickly decays back to the ground state. In the process, a photon of light is released. 

Electrons fill orbitals in a consistent order: they first fill the orbitals closest to the nucleus, then they continue to fill orbitals of increasing energy further from the nucleus. If there are multiple orbitals of equal energy, they will be filled with one electron in each energy level before a second electron is added. The electrons of the outermost energy level determine the energetic stability of the atom and its tendency to form chemical bonds with other atoms to form molecules. 

Under standard conditions, atoms fill the inner shells first, often resulting in a variable number of electrons in the outermost shell. The innermost shell has a maximum of two electrons but the next two electron shells can each have a maximum of eight electrons. This is known as the octet rule , which states, with the exception of the innermost shell, that atoms are more stable energetically when they have eight electrons in their valence shell , the outermost electron shell. Examples of some neutral atoms and their electron configurations are shown in this figure . Notice that in this [link] , helium has a complete outer electron shell, with two electrons filling its first and only shell. Similarly, neon has a complete outer 2n shell containing eight electrons. In contrast, chlorine and sodium have seven and one in their outer shells, respectively, but theoretically they would be more energetically stable if they followed the octet rule and had eight. Visual Connections Bohr diagrams indicate how many electrons fill each principal shell. Group 18 elements (helium, neon, and argon are shown) have a full outer, or valence, shell. A full valence shell is the most stable electron configuration. Elements in other groups have partially filled valence shells and gain or lose electrons to achieve a stable electron configuration. 

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Understanding that the organization of the periodic table is based on the total number of protons (and electrons) helps us know how electrons are distributed among the outer shell. The periodic table is arranged in columns and rows based on the number of electrons and where these electrons are located. Take a closer look at the some of the elements in the table s far right column in the periodic table . The group 18 atoms helium (He), neon (Ne), and argon (Ar) all have filled outer electron shells, making it unnecessary for them to share electrons with other atoms to attain stability; they are highly stable as single atoms. Their non-reactivity has resulted in their being named the inert gases (or noble gases ). Compare this to the group 1 elements in the left-hand column. These elements, including hydrogen (H), lithium (Li), and sodium (Na), all have one electron in their outermost shells. That means that they can achieve a stable configuration and a filled outer shell by donating or sharing one electron with another atom or a molecule such as water. Hydrogen will donate or share its electron to achieve this configuration, while lithium and sodium will donate their electron to become stable. As a result of losing a negatively charged electron, they become positively charged ions . Group 17 elements, including fluorine and chlorine, have seven electrons in their outmost shells, so they tend to fill this shell with an electron from other atoms or molecules, making them negatively charged ions. Group 14 elements, of which carbon is the most important to living systems, have four electrons in their outer shell allowing them to make several covalent bonds (discussed below) with other atoms. Thus, the columns of the periodic table represent the potential shared state of these elements outer electron shells that is responsible for their similar chemical characteristics. Electron Orbitals 

Although useful to explain the reactivity and chemical bonding of certain elements, the Bohr model of the atom does not accurately reflect how electrons are spatially distributed surrounding the nucleus. They do not circle the nucleus like the earth orbits the sun, but are found in electron orbitals . These relatively complex shapes result from the fact that electrons behave not just like particles, but also like waves. Mathematical equations from quantum mechanics known as wave functions can predict within a certain level of probability where an electron might be at any given time. The area where an electron is most likely to be found is called its orbital. 

Recall that the Bohr model depicts an atom s electron shell configuration. Within each electron shell are subshells, and each subshell has a specified number of orbitals containing electrons. While it is impossible to calculate exactly where an electron is located, scientists know that it is most probably located within its orbital path. Subshells are designated by the letter s, p , d , and f . The s subshell is spherical in shape and has one orbital. Principal shell 1n has only a single s orbital, which can hold two electrons. Principal shell 2n has one s and one p subshell, and can hold a total of eight electrons. The p subshell has three dumbbell-shaped orbitals, as illustrated in [link] . Subshells d and f have more complex shapes and contain five and seven orbitals, respectively. These are not shown in the illustration. Principal shell 3n has s , p , and d subshells and can hold 18 electrons. Principal shell 4n has s , p , d and f orbitals and can hold 32 electrons. Moving away from the nucleus, the number of electrons and orbitals found in the energy levels increases. Progressing from one atom to the next in the periodic table, the electron structure can be worked out by fitting an extra electron into the next available orbital. The s subshells are shaped like spheres. Both the 1n and 2n principal shells have an s orbital, but the size of the sphere is larger in the 2n orbital. Each sphere is a single orbital. p subshells are made up of three dumbbell-shaped orbitals. Principal shell 2n has a p subshell, but shell 1 does not. 

The closest orbital to the nucleus, called the 1s orbital, can hold up to two electrons. This orbital is equivalent to the innermost electron shell of the Bohr model of the atom. It is called the 1 s orbital because it is spherical around the nucleus. The 1 s orbital is the closest orbital to the nucleus, and it is always filled first, before any other orbital can be filled. Hydrogen has one electron; therefore, it has only one spot within the 1 s orbital occupied. This is designated as 1 s 1 , where the superscripted 1 refers to the one electron within the 1 s orbital. Helium has two electrons; therefore, it can completely fill the 1 s orbital with its two electrons. This is designated as 1 s 2 , referring to the two electrons of helium in the 1 s orbital. On the periodic table [link] , hydrogen and helium are the only two elements in the first row (period); this is because they only have electrons in their first shell, the 1 s orbital. Hydrogen and helium are the only two elements that have the 1 s and no other electron orbitals in the electrically neutral state. 

The second electron shell may contain eight electrons. This shell contains another spherical s orbital and three dumbbell shaped p orbitals, each of which can hold two electrons, as shown in [link] . After the 1 s orbital is filled, the second electron shell is filled, first filling its 2 s orbital and then its three p orbitals. When filling the p orbitals, each takes a single electron; once each p orbital has an electron, a second may be added. Lithium (Li) contains three electrons that occupy the first and second shells. Two electrons fill the 1 s orbital, and the third electron then fills the 2 s orbital. Its electron configuration is 1 s 2 2 s 1 . Neon (Ne), on the other hand, has a total of ten electrons: two are in its innermost 1 s orbital and eight fill its second shell (two each in the 2 s and three p orbitals); thus, it is an inert gas and energetically stable as a single atom that will rarely form a chemical bond with other atoms. Larger elements have additional orbitals, making up the third electron shell. While the concepts of electron shells and orbitals are closely related, orbitals provide a more accurate depiction of the electron configuration of an atom because the orbital model specifies the different shapes and special orientations of all the places that electrons may occupy. Link to Learning 

Watch this visual animation to see the spatial arrangement of the p and s orbitals. 

[link] Activity 

Create diagrams to show the placement of protons, neutrons, and electrons in an atom of carbon-12 and carbon-14, respectably. Based on their subatomic difference(s), determine which element is an organism more likely to use to synthesize glucose (C 6 H 12 O 6 ) and give a reason for your choice. 

This activity is an application of Learning Objective 2.8 and Science Practice 4.1 because the student is asked to justify which form of carbon is organism is more likely to take up from the environment and use based on the properties of the element(s). 

Answer 

Carbon-12 is a stable isotope because it contains equal numbers of protons and neutrons. Carbon-14 is less stable and undergoes radioactive decay, losing two neutrons to become the more stable carbon-12. Therefore, organisms are more likely to use carbon-12 to synthesize glucose. Chemical Reactions and Molecules 

All elements are most stable when their outermost shell is filled with electrons according to the octet rule. This is because it is energetically favorable for atoms to be in that configuration and it makes them stable. However, since not all elements have enough electrons to fill their outermost shells, atoms form chemical bonds with other atoms thereby obtaining the electrons they need to attain a stable electron configuration. When two or more atoms chemically bond with each other, the resultant chemical structure is a molecule. The familiar water molecule, H 2 O, consists of two hydrogen atoms and one oxygen atom; these bond together to form water, as illustrated in [link] . Atoms can form molecules by donating, accepting, or sharing electrons to fill their outer shells. Two or more atoms may bond with each other to form a molecule. When two hydrogens and an oxygen share electrons via covalent bonds, a water molecule is formed. 

Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart. The substances used in the beginning of a chemical reaction are called the reactants (usually found on the left side of a chemical equation), and the substances found at the end of the reaction are known as the products (usually found on the right side of a chemical equation). An arrow is typically drawn between the reactants and products to indicate the direction of the chemical reaction; this direction is not always a one-way street. For the creation of the water molecule shown above, the chemical equation would be: 2 H + O H 2 O 2 H + O H 2 O 

An example of a simple chemical reaction is the breaking down of hydrogen peroxide molecules, each of which consists of two hydrogen atoms bonded to two oxygen atoms (H 2 O 2 ). The reactant hydrogen peroxide is broken down into water, containing one oxygen atom bound to two hydrogen atoms (H 2 O), and oxygen, which consists of two bonded oxygen atoms (O 2 ). In the equation below, the reaction includes two hydrogen peroxide molecules and two water molecules. This is an example of a balanced chemical equation , wherein the number of atoms of each element is the same on each side of the equation. According to the law of conservation of matter, the number of atoms before and after a chemical reaction should be equal, such that no atoms are, under normal circumstances, created or destroyed. 2H 2 O 2 (hydrogen peroxide) 2H 2 O (water) + O 2 (oxygen) 2H 2 O 2 (hydrogen peroxide) 2H 2 O (water) + O 2 (oxygen) 

Even though all of the reactants and products of this reaction are molecules (each atom remains bonded to at least one other atom), in this reaction only hydrogen peroxide and water are representatives of compounds : they contain atoms of more than one type of element. Molecular oxygen, on the other hand, as shown in [link] ,consists of two doubly bonded oxygen atoms and is not classified as a compound but as a mononuclear molecule. The oxygen atoms in an O 2 molecule are joined by a double bond. 

Some chemical reactions, such as the one shown above, can proceed in one direction until the reactants are all used up. The equations that describe these reactions contain a unidirectional arrow and are irreversible . Reversible reactions are those that can go in either direction. In reversible reactions, reactants are turned into products, but when the concentration of product goes beyond a certain threshold (characteristic of the particular reaction), some of these products will be converted back into reactants; at this point, the designations of products and reactants are reversed. This back and forth continues until a certain relative balance between reactants and products occurs a state called equilibrium . These situations of reversible reactions are often denoted by a chemical equation with a double headed arrow pointing towards both the reactants and products. 

For example, in human blood, excess hydrogen ions (H + ) bind to bicarbonate ions (HCO 3 - ) forming an equilibrium state with carbonic acid (H 2 CO 3 ). If carbonic acid were added to this system, some of it would be converted to bicarbonate and hydrogen ions. HCO + H + H 2 CO 3 HCO + H + H 2 CO 3 

In biological reactions, however, equilibrium is rarely obtained because the concentrations of the reactants or products or both are constantly changing, often with a product of one reaction being a reactant for another. To return to the example of excess hydrogen ions in the blood, the formation of carbonic acid will be the major direction of the reaction. However, the carbonic acid can also leave the body as carbon dioxide gas (via exhalation) instead of being converted back to bicarbonate ion, thus driving the reaction to the right by the chemical law known as law of mass action . These reactions are important for maintaining the homeostasis of our blood. HCO + H + H 2 CO 3 CO 2 + H 2 O HCO + H + H 2 CO 3 CO 2 + H 2 O Ions and Ionic Bonds 

Some atoms are more stable when they gain or lose an electron (or possibly two) and form ions. This fills their outermost electron shell and makes them energetically more stable. Because the number of electrons does not equal the number of protons, each ion has a net charge. Cations are positive ions that are formed by losing electrons. Negative ions are formed by gaining electrons and are called anions. Anions are designated by their elemental name being altered to end in -ide : the anion of chlorine is called chloride, and the anion of sulfur is called sulfide, for example. 

This movement of electrons from one element to another is referred to as electron transfer . As [link] illustrates, sodium (Na) only has one electron in its outer electron shell. It takes less energy for sodium to donate that one electron than it does to accept seven more electrons to fill the outer shell. If sodium loses an electron, it now has 11 protons, 11 neutrons, and only 10 electrons, leaving it with an overall charge of +1. It is now referred to as a sodium ion. Chlorine (Cl) in its lowest energy state (called the ground state) has seven electrons in its outer shell. Again, it is more energy-efficient for chlorine to gain one electron than to lose seven. Therefore, it tends to gain an electron to create an ion with 17 protons, 17 neutrons, and 18 electrons, giving it a net negative ( 1) charge. It is now referred to as a chloride ion. In this example, sodium will donate its one electron to empty its shell, and chlorine will accept that electron to fill its shell. Both ions now satisfy the octet rule and have complete outermost shells. Because the number of electrons is no longer equal to the number of protons, each is now an ion and has a +1 (sodium cation) or 1 (chloride anion) charge. Note that these transactions can normally only take place simultaneously: in order for a sodium atom to lose an electron, it must be in the presence of a suitable recipient like a chlorine atom. In the formation of an ionic compound, metals lose electrons and nonmetals gain electrons to achieve an octet. 

Ionic bonds are formed between ions with opposite charges. For instance, positively charged sodium ions and negatively charged chloride ions bond together to make crystals of sodium chloride, or table salt, creating a crystalline molecule with zero net charge. 

Certain salts are referred to in physiology as electrolytes (including sodium, potassium, and calcium), ions necessary for nerve impulse conduction, muscle contractions and water balance. Many sports drinks and dietary supplements provide these ions to replace those lost from the body via sweating during exercise. Covalent Bonds and Other Bonds and Interactions 

Another way the octet rule can be satisfied is by the sharing of electrons between atoms to form covalent bonds . These bonds are stronger and much more common than ionic bonds in the molecules of living organisms. Covalent bonds are commonly found in carbon-based organic molecules, such as our DNA and proteins. Covalent bonds are also found in inorganic molecules like H 2 O, CO 2 , and O 2 . One, two, or three pairs of electrons may be shared, making single, double, and triple bonds, respectively. The more covalent bonds between two atoms, the stronger their connection. Thus, triple bonds are the strongest. 

The strength of different levels of covalent bonding is one of the main reasons living organisms have a difficult time in acquiring nitrogen for use in constructing their molecules, even though molecular nitrogen, N 2 , is the most abundant gas in the atmosphere. Molecular nitrogen consists of two nitrogen atoms triple bonded to each other and, as with all molecules, the sharing of these three pairs of electrons between the two nitrogen atoms allows for the filling of their outer electron shells, making the molecule more stable than the individual nitrogen atoms. This strong triple bond makes it difficult for living systems to break apart this nitrogen in order to use it as constituents of proteins and DNA. 

The formation of water molecules provides an example of covalent bonding. The hydrogen and oxygen atoms that combine to form water molecules are bound together by covalent bonds, as shown in [link] . The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atoms and the incomplete outer shell of the oxygen atoms. To completely fill the outer shell of oxygen, which has six electrons in its outer shell but which would be more stable with eight, two electrons (one from each hydrogen atom) are needed: hence the well-known formula H 2 O. The electrons are shared between the two elements to fill the outer shell of each, making both elements more stable. Link to Learning 

View this short video to see an animation of ionic and covalent bonding. 

[link] Polar Covalent Bonds 

There are two types of covalent bonds: polar and nonpolar. In a polar covalent bond , shown in this figure , the electrons are unequally shared by the atoms and are attracted more to one nucleus than the other. Because of the unequal distribution of electrons between the atoms of different elements, a slightly positive ( +) or slightly negative ( ) charge develops. This partial charge is an important property of water and accounts for many of its characteristics. 

Water is a polar molecule, with the hydrogen atoms acquiring a partial positive charge and the oxygen a partial negative charge. This occurs because the nucleus of the oxygen atom is more attractive to the electrons of the hydrogen atoms than the hydrogen nucleus is to the oxygen s electrons. Thus oxygen has a higher electronegativity than hydrogen and the shared electrons spend more time in the vicinity of the oxygen nucleus than they do near the nucleus of the hydrogen atoms, giving the atoms of oxygen and hydrogen slightly negative and positive charges, respectively. Another way of stating this is that the probability of finding a shared electron near an oxygen nucleus is more likely than finding it near a hydrogen nucleus. Either way, the atom s relative electronegativity contributes to the development of partial charges whenever one element is significantly more electronegative than the other, and the charges generated by these polar bonds may then be used for the formation of hydrogen bonds based on the attraction of opposite partial charges. (Hydrogen bonds, which are discussed in detail below, are weak bonds between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules.) Since macromolecules often have atoms within them that differ in electronegativity, polar bonds are often present in organic molecules. Nonpolar Covalent Bonds 

Nonpolar covalent bonds form between two atoms of the same element or between different elements that share electrons equally. For example, molecular oxygen (O 2 ) is nonpolar because the electrons will be equally distributed between the two oxygen atoms. 

Another example of a nonpolar covalent bond is methane (CH 4 ), also shown in this figure . Carbon has four electrons in its outermost shell and needs four more to fill it. It gets these four from four hydrogen atoms, each atom providing one, making a stable outer shell of eight electrons. Carbon and hydrogen do not have the same electronegativity but are similar; thus, nonpolar bonds form. The hydrogen atoms each need one electron for their outermost shell, which is filled when it contains two electrons. These elements share the electrons equally among the carbons and the hydrogen atoms, creating a nonpolar covalent molecule. Whether a molecule is polar or nonpolar depends both on bond type and molecular shape. Both water and carbon dioxide have polar covalent bonds, but carbon dioxide is linear, so the partial charges on the molecule cancel each other out. Hydrogen Bonds and Van Der Waals Interactions 

Ionic and covalent bonds between elements require energy to break. Ionic bonds are not as strong as covalent, which determines their behavior in biological systems. However, not all bonds are ionic or covalent bonds. Weaker bonds can also form between molecules. Two weak bonds that occur frequently are hydrogen bonds and van der Waals interactions. Without these two types of bonds, life as we know it would not exist. Hydrogen bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of proteins and DNA, the building block of cells. 

When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly positive charge because hydrogen s electron is pulled more strongly toward the other element and away from the hydrogen. Because the hydrogen is slightly positive, it will be attracted to neighboring negative charges. When this happens, a weak interaction occurs between the + of the hydrogen from one molecule and the charge on the more electronegative atoms of another molecule, usually oxygen or nitrogen, or within the same molecule. This interaction is called a hydrogen bond . This type of bond is common and occurs regularly between water molecules. Individual hydrogen bonds are weak and easily broken; however, they occur in very large numbers in water and in organic polymers, creating a major force in combination. Hydrogen bonds are also responsible for zipping together the DNA double helix. 

Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules. Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom. For these attractions to happen, the molecules need to be very close to one another. These bonds along with ionic, covalent, and hydrogen bonds contribute to the three-dimensional structure of the proteins in our cells that is necessary for their proper function. Pharmaceutical Chemist 

Pharmaceutical chemists are responsible for the development of new drugs and trying to determine the mode of action of both old and new drugs. They are involved in every step of the drug development process. Drugs can be found in the natural environment or can be synthesized in the laboratory. In many cases, potential drugs found in nature are changed chemically in the laboratory to make them safer and more effective, and sometimes synthetic versions of drugs substitute for the version found in nature. 

After the initial discovery or synthesis of a drug, the chemist then develops the drug, perhaps chemically altering it, testing it to see if the drug is toxic, and then designing methods for efficient large-scale production. Then, the process of getting the drug approved for human use begins. In the United States, drug approval is handled by the Food and Drug Administration (FDA) and involves a series of large-scale experiments using human subjects to make sure the drug is not harmful and effectively treats the condition it aims to treat. This process often takes several years and requires the participation of physicians and scientists, in addition to chemists, to complete testing and gain approval. 

An example of a drug that was originally discovered in a living organism is Paclitaxel (Taxol), an anti-cancer drug used to treat breast cancer. This drug was discovered in the bark of the pacific yew tree. Another example is aspirin, originally isolated from willow tree bark. Finding drugs often means testing hundreds of samples of plants, fungi, and other forms of life to see if any biologically active compounds are found within them. Sometimes, traditional medicine can give modern medicine clues to where an active compound can be found. For example, the use of willow bark to make medicine has been known for thousands of years, dating back to ancient Egypt. It was not until the late 1800s, however, that the aspirin molecule, known as acetylsalicylic acid, was purified and marketed for human use. 

Occasionally, drugs developed for one use are found to have unforeseen effects that allow these drugs to be used in other, unrelated ways. For example, the drug minoxidil (Rogaine) was originally developed to treat high blood pressure. When tested on humans, it was noticed that individuals taking the drug would grow new hair. Eventually the drug was marketed to men and women with baldness to restore lost hair. 

The career of the pharmaceutical chemist may involve detective work, experimentation, and drug development, all with the goal of making human beings healthier. Bonds Can Be Flexible 

Proteins are mostly made up of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. The proteins that make up hair contain sulfur bonded to another sulfur, which is called a disulfide bond. These covalent bonds give hair its shape and texture. Heat from a hair straightener breaks the disulfide bonds, which causes the hair to lose its curl. Why do you think this method of hair straightening isn t permanent? 

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Answer 

When hair is straightened the extreme heat causes the disulfide bonds to break. When the hair cools down, the disulfide bonds between the keratin are reformed. Because the keratin molecules are in different positions when the bonds are reformed, the hair stays in the straightened shape. However, these disulfide bonds reform yet again when the hair is exposed to moisture. Section Summary 

Matter is anything that occupies space and has mass. It is made up of elements. All of the 92 elements that occur naturally have unique qualities that allow them to combine in various ways to create molecules, which in turn combine to form cells, tissues, organ systems, and organisms. Atoms, which consist of protons, neutrons, and electrons, are the smallest units of an element that retain all of the properties of that element. Electrons can be transferred, shared, or cause charge disparities between atoms to create bonds, including ionic, covalent, and hydrogen bonds, as well as van der Waals interactions. Review Questions 

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[link] Glossary anion negative ion that is formed by an atom gaining one or more electrons atom the smallest unit of matter that retains all of the chemical properties of an element atomic mass calculated mean of the mass number for an element s isotopes atomic number total number of protons in an atom balanced chemical equation statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants cation positive ion that is formed by an atom losing one or more electrons chemical bond interaction between two or more of the same or different atoms that results in the formation of molecules chemical reaction process leading to the rearrangement of atoms in molecules chemical reactivity the ability to combine and to chemically bond with each other compound substance composed of molecules consisting of atoms of at least two different elements covalent bond type of strong bond formed between two of the same or different elements; forms when electrons are shared between atoms electrolyte ion necessary for nerve impulse conduction, muscle contractions and water balance electron negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of 1 unit electron configuration arrangement of electrons in an atom s electron shell (for example, 1s 2 2s 2 2p 6 ) electron orbital how electrons are spatially distributed surrounding the nucleus; the area where an electron is most likely to be found electron transfer movement of electrons from one element to another; important in creation of ionic bonds electronegativity ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms element one of 118 unique substances that cannot be broken down into smaller substances; each element has unique properties and a specified number of protons equilibrium steady state of relative reactant and product concentration in reversible chemical reactions in a closed system hydrogen bond weak bond between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules inert gas (also, noble gas) element with filled outer electron shell that is unreactive with other atoms ion atom or chemical group that does not contain equal numbers of protons and electrons ionic bond chemical bond that forms between ions with opposite charges (cations and anions) irreversible chemical reaction chemical reaction where reactants proceed uni-directionally to form products isotope one or more forms of an element that have different numbers of neutrons law of mass action chemical law stating that the rate of a reaction is proportional to the concentration of the reacting substances mass number total number of protons and neutrons in an atom matter anything that has mass and occupies space molecule two or more atoms chemically bonded together neutron uncharged particle that resides in the nucleus of an atom; has a mass of one amu noble gas see inert gas nonpolar covalent bond type of covalent bond that forms between atoms when electrons are shared equally between them nucleus core of an atom; contains protons and neutrons octet rule rule that atoms are most stable when they hold eight electrons in their outermost shells orbital region surrounding the nucleus; contains electrons periodic table organizational chart of elements indicating the atomic number and atomic mass of each element; provides key information about the properties of the elements polar covalent bond type of covalent bond that forms as a result of unequal sharing of electrons, resulting in the creation of slightly positive and slightly negative charged regions of the molecule product molecule found on the right side of a chemical equation proton positively charged particle that resides in the nucleus of an atom; has a mass of one amu and a charge of +1 radioisotope isotope that emits radiation composed of subatomic particles to form more stable elements reactant molecule found on the left side of a chemical equation reversible chemical reaction chemical reaction that functions bi-directionally, where products may turn into reactants if their concentration is great enough valence shell outermost shell of an atom van der Waals interaction very weak interaction between molecules due to temporary charges attracting atoms that are very close togetherWater Water 

In this section, you will investigate the following questions: How does the molecular structure of water result in unique properties of water that are critical to maintaining life? What are the role of acids, bases, and buffers in dynamic homeostasis? Connection for AP Courses 

Covalent bonds form between atoms when they share electrons to fill their valence electron shells. When the sharing of electrons between atoms is equal, such as O 2 (oxygen) or CH 4 (methane), the covalent bond is said to be nonpolar . However, when electrons are shared, but not equally due to differences in electronegativity (the tendency to attract electrons), the covalent bond is said to be polar . H 2 O (water) is an example of a polar molecule. Because oxygen is more electronegative than hydrogen, the electrons are drawn toward oxygen and away from the hydrogen atoms; consequently, the oxygen atom acquires a slight negative charge and each hydrogen atoms acquires a slightly positive charge. It is important to remember that the electrons are still shared, just not equally. 

Water s polarity allows for the formation of hydrogen bonds between adjacent water molecules, resulting in many unique properties that are critical to maintaining life. For example, water is an excellent solvent because hydrogen bonds allow ions and other polar molecules to dissolve in water. Water s hydrogen bonds also contribute to its high heat capacity and high heat of vaporization, resulting in greater temperature stability. Hydrogen bond formation makes ice less dense as a solid than as a liquid, insulating aquatic environments. Water s cohesive and adhesive properties are seen as it rises inside capillary tubes or travels up a large tree from roots to leaves. The pH or hydrogen ion concentration of a solution is highly regulated to help organisms maintain homeostasis; for example, as will be explored in later chapters, the enzymes that catalyze most chemical reactions in cells are pH specific. Thus, the properties of water are connected to the biochemical and physical processes performed by living organisms. Life on Earth would be very different if these properties were altered if life could exist at all. 

The information presented and the examples highlighted in this section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 2.8 The student is able to justify the selection of data regarding the types of molecules that an animal, plant, or bacterium will take up as necessary building blocks and excrete as waste products. 

Discuss with students why scientists use the criteria of the presence of liquid water to determine if an environment or planet can support life. More information on this topic is available at this site . 

Have students create visual representations with annotations to explain how water s molecular structure and the resulting polarity results in its unique properties. Have the students describe how these properties are vital to life processes. 

Why do scientists spend time looking for water on other planets? Why is water so important? It is because water is essential to life as we know it. Water is one of the more abundant molecules and the one most critical to life on Earth. Approximately 60 70 percent of the human body is made up of water. Without it, life as we know it simply would not exist. 

The polarity of the water molecule and its resulting hydrogen bonding make water a unique substance with special properties that are intimately tied to the processes of life. Life originally evolved in a watery environment, and most of an organism s cellular chemistry and metabolism occur inside the watery contents of the cell s cytoplasm. Special properties of water are its high heat capacity and heat of vaporization, its ability to dissolve polar molecules, its cohesive and adhesive properties, and its dissociation into ions that leads to the generation of pH. Understanding these characteristics of water helps to elucidate its importance in maintaining life. Water s Polarity 

One of water s important properties is that it is composed of polar molecules: the hydrogen and oxygen within water molecules (H 2 O) form polar covalent bonds. While there is no net charge to a water molecule, the polarity of water creates a slightly positive charge on hydrogen and a slightly negative charge on oxygen, contributing to water s properties of attraction. Water s charges are generated because oxygen is more electronegative than hydrogen, making it more likely that a shared electron would be found near the oxygen nucleus than the hydrogen nucleus, thus generating the partial negative charge near the oxygen. 

As a result of water s polarity, each water molecule attracts other water molecules because of the opposite charges between water molecules, forming hydrogen bonds. Water also attracts or is attracted to other polar molecules and ions. A polar substance that interacts readily with or dissolves in water is referred to as hydrophilic (hydro- = water ; -philic = loving ). In contrast, non-polar molecules such as oils and fats do not interact well with water, as shown in [link] and separate from it rather than dissolve in it, as we see in salad dressings containing oil and vinegar (an acidic water solution). These nonpolar compounds are called hydrophobic (hydro- = water ; -phobic = fearing ). Oil and water do not mix. As this macro image of oil and water shows, oil does not dissolve in water but forms droplets instead. This is due to it being a nonpolar compound. (credit: Gautam Dogra). Water s States: Gas, Liquid, and Solid 

The formation of hydrogen bonds is an important quality of the liquid water that is crucial to life as we know it. As water molecules make hydrogen bonds with each other, water takes on some unique chemical characteristics compared to other liquids and, since living things have a high water content, understanding these chemical features is key to understanding life. In liquid water, hydrogen bonds are constantly formed and broken as the water molecules slide past each other. The breaking of these bonds is caused by the motion (kinetic energy) of the water molecules due to the heat contained in the system. When the heat is raised as water is boiled, the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas (steam or water vapor). On the other hand, when the temperature of water is reduced and water freezes, the water molecules form a crystalline structure maintained by hydrogen bonding (there is not enough energy to break the hydrogen bonds) that makes ice less dense than liquid water, a phenomenon not seen in the solidification of other liquids. 

Water s lower density in its solid form is due to the way hydrogen bonds are oriented as it freezes: the water molecules are pushed farther apart compared to liquid water. With most other liquids, solidification when the temperature drops includes the lowering of kinetic energy between molecules, allowing them to pack even more tightly than in liquid form and giving the solid a greater density than the liquid. 

The lower density of ice, illustrated and pictured in [link] , an anomaly, causes it to float at the surface of liquid water, such as in an iceberg or in the ice cubes in a glass of ice water. In lakes and ponds, ice will form on the surface of the water creating an insulating barrier that protects the animals and plant life in the pond from freezing. Without this layer of insulating ice, plants and animals living in the pond would freeze in the solid block of ice and could not survive. The detrimental effect of freezing on living organisms is caused by the expansion of ice relative to liquid water. The ice crystals that form upon freezing rupture the delicate membranes essential for the function of living cells, irreversibly damaging them. Cells can only survive freezing if the water in them is temporarily replaced by another liquid like glycerol. Hydrogen bonding makes ice less dense than liquid water. The (a) lattice structure of ice makes it less dense than the freely flowing molecules of liquid water, enabling it to (b) float on water. (credit a: modification of work by Jane Whitney, image created using Visual Molecular Dynamics (VMD) software 1 ; credit b: modification of work by Carlos Ponte) 

Click here to see a 3-D animation of the structure of an ice lattice. (Image credit: Jane Whitney. Image created using Visual Molecular Dynamics VMD software. 2 ) 

[link] Water s High Heat Capacity 

Water s high heat capacity is a property caused by hydrogen bonding among water molecules. Water has the highest specific heat capacity of any liquids. Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius. For water, this amount is one calorie . It therefore takes water a long time to heat and long time to cool. In fact, the specific heat capacity of water is about five times more than that of sand. This explains why the land cools faster than the sea. Due to its high heat capacity, water is used by warm blooded animals to more evenly disperse heat in their bodies: it acts in a similar manner to a car s cooling system, transporting heat from warm places to cool places, causing the body to maintain a more even temperature. Water s Heat of Vaporization 

Water also has a high heat of vaporization , the amount of energy required to change one gram of a liquid substance to a gas. A considerable amount of heat energy (586 cal) is required to accomplish this change in water. This process occurs on the surface of water. As liquid water heats up, hydrogen bonding makes it difficult to separate the liquid water molecules from each other, which is required for it to enter its gaseous phase (steam). As a result, water acts as a heat sink or heat reservoir and requires much more heat to boil than does a liquid such as ethanol (grain alcohol), whose hydrogen bonding with other ethanol molecules is weaker than water s hydrogen bonding. Eventually, as water reaches its boiling point of 100 Celsius (212 Fahrenheit), the heat is able to break the hydrogen bonds between the water molecules, and the kinetic energy (motion) between the water molecules allows them to escape from the liquid as a gas. Even when below its boiling point, water s individual molecules acquire enough energy from other water molecules such that some surface water molecules can escape and vaporize: this process is known as evaporation . 

The fact that hydrogen bonds need to be broken for water to evaporate means that a substantial amount of energy is used in the process. As the water evaporates, energy is taken up by the process, cooling the environment where the evaporation is taking place. In many living organisms, including in humans, the evaporation of sweat, which is 90 percent water, allows the organism to cool so that homeostasis of body temperature can be maintained. Water s Solvent Properties 

Since water is a polar molecule with slightly positive and slightly negative charges, ions and polar molecules can readily dissolve in it. Therefore, water is referred to as a solvent , a substance capable of dissolving other polar molecules and ionic compounds. The charges associated with these molecules will form hydrogen bonds with water, surrounding the particle with water molecules. This is referred to as a sphere of hydration , or a hydration shell, as illustrated in [link] and serves to keep the particles separated or dispersed in the water. 

When ionic compounds are added to water, the individual ions react with the polar regions of the water molecules and their ionic bonds are disrupted in the process of dissociation . Dissociation occurs when atoms or groups of atoms break off from molecules and form ions. Consider table salt (NaCl, or sodium chloride): when NaCl crystals are added to water, the molecules of NaCl dissociate into Na + and Cl ions, and spheres of hydration form around the ions, illustrated in [link] . The positively charged sodium ion is surrounded by the partially negative charge of the water molecule s oxygen. The negatively charged chloride ion is surrounded by the partially positive charge of the hydrogen on the water molecule. When table salt (NaCl) is mixed in water, spheres of hydration are formed around the ions. Water s Cohesive and Adhesive Properties 

Have you ever filled a glass of water to the very top and then slowly added a few more drops? Before it overflows, the water forms a dome-like shape above the rim of the glass. This water can stay above the glass because of the property of cohesion . In cohesion, water molecules are attracted to each other (because of hydrogen bonding), keeping the molecules together at the liquid-gas (water-air) interface, although there is no more room in the glass. 

Cohesion allows for the development of surface tension , the capacity of a substance to withstand being ruptured when placed under tension or stress. This is also why water forms droplets when placed on a dry surface rather than being flattened out by gravity. When a small scrap of paper is placed onto the droplet of water, the paper floats on top of the water droplet even though paper is denser (heavier) than the water. Cohesion and surface tension keep the hydrogen bonds of water molecules intact and support the item floating on the top. It s even possible to float a needle on top of a glass of water if it is placed gently without breaking the surface tension, as shown in [link] . The weight of the needle is pulling the surface downward; at the same time, the surface tension is pulling it up, suspending it on the surface of the water and keeping it from sinking. Notice the indentation in the water around the needle. (credit: Cory Zanker) 

These cohesive forces are related to water s property of adhesion , or the attraction between water molecules and other molecules. This attraction is sometimes stronger than water s cohesive forces, especially when the water is exposed to charged surfaces such as those found on the inside of thin glass tubes known as capillary tubes. Adhesion is observed when water climbs up the tube placed in a glass of water: notice that the water appears to be higher on the sides of the tube than in the middle. This is because the water molecules are attracted to the charged glass walls of the capillary more than they are to each other and therefore adhere to it. This type of adhesion is called capillary action , and is illustrated in [link] . Capillary action in a glass tube is caused by the adhesive forces exerted by the internal surface of the glass exceeding the cohesive forces between the water molecules themselves. (credit: modification of work by Pearson-Scott Foresman, donated to the Wikimedia Foundation) 

Why are cohesive and adhesive forces important for life? Cohesive and adhesive forces are important for the transport of water from the roots to the leaves in plants. These forces create a pull on the water column. This pull results from the tendency of water molecules being evaporated on the surface of the plant to stay connected to water molecules below them, and so they are pulled along. Plants use this natural phenomenon to help transport water from their roots to their leaves. Without these properties of water, plants would be unable to receive the water and the dissolved minerals they require. In another example, insects such as the water strider, shown in [link] , use the surface tension of water to stay afloat on the surface layer of water and even mate there. Water s cohesive and adhesive properties allow this water strider ( Gerris sp.) to stay afloat. (credit: Tim Vickers) Activity 

During a process called transpiration, water evaporates through a plant s leaves. Water in the ground travels up from the roots to the leaves. Based on water s molecular properties, create a visual representation (e.g., diagrams or models) with annotations to explain how water travels up a 300-ft. California redwood tree. What other unique properties of water are attributed to its molecular structure, and how are these properties important to life? 

This activity is an application of Learning Objectives 2.8 and Science Practice 4.1 and Learning Objectives 2.9 and Science Practices 1.1 and 1.4 because you are modeling the relationship between water s molecular structure and its unique properties that are essential to maintaining life, including capillary action. pH, Buffers, Acids, and Bases 

The pH of a solution indicates its acidity or alkalinity. H 2 O ( l ) H + ( a q ) + OH - ( a q ) H 2 O ( l ) H + ( a q ) + OH - ( a q ) litmus or pH paper, filter paper that has been treated with a natural water-soluble dye so it can be used as a pH indicator, to test how much acid (acidity) or base (alkalinity) exists in a solution. You might have even used some to test whether the water in a swimming pool is properly treated. In both cases, the pH test measures the concentration of hydrogen ions in a given solution. 

Hydrogen ions are spontaneously generated in pure water by the dissociation (ionization) of a small percentage of water molecules into equal numbers of hydrogen (H + ) ions and hydroxide (OH - ) ions. While the hydroxide ions are kept in solution by their hydrogen bonding with other water molecules, the hydrogen ions, consisting of naked protons, are immediately attracted to un-ionized water molecules, forming hydronium ions (H 3 0 + ). Still, by convention, scientists refer to hydrogen ions and their concentration as if they were free in this state in liquid water. 

The concentration of hydrogen ions dissociating from pure water is 1 10 -7 moles H + ions per liter of water. Moles (mol) are a way to express the amount of a substance (which can be atoms, molecules, ions, etc), with one mole being equal to 6.02 x 10 23 particles of the substance. Therefore, 1 mole of water is equal to 6.02 x 10 23 water molecules. The pH is calculated as the negative of the base 10 logarithm of this concentration. The log10 of 1 10 -7 is -7.0, and the negative of this number (indicated by the p of pH ) yields a pH of 7.0, which is also known as neutral pH. The pH inside of human cells and blood are examples of two areas of the body where near-neutral pH is maintained. 

Non-neutral pH readings result from dissolving acids or bases in water. Using the negative logarithm to generate positive integers, high concentrations of hydrogen ions yield a low pH number, whereas low levels of hydrogen ions result in a high pH. An acid is a substance that increases the concentration of hydrogen ions (H + ) in a solution, usually by having one of its hydrogen atoms dissociate. A base provides either hydroxide ions (OH ) or other negatively charged ions that combine with hydrogen ions, reducing their concentration in the solution and thereby raising the pH. In cases where the base releases hydroxide ions, these ions bind to free hydrogen ions, generating new water molecules. 

The stronger the acid, the more readily it donates H + . For example, hydrochloric acid (HCl) completely dissociates into hydrogen and chloride ions and is highly acidic, whereas the acids in tomato juice or vinegar do not completely dissociate and are considered weak acids. Conversely, strong bases are those substances that readily donate OH or take up hydrogen ions. Sodium hydroxide (NaOH) and many household cleaners are highly alkaline and give up OH rapidly when placed in water, thereby raising the pH. An example of a weak basic solution is seawater, which has a pH near 8.0, close enough to neutral pH that marine organisms adapted to this saline environment are able to thrive in it. 

The pH scale is, as previously mentioned, an inverse logarithm and ranges from 0 to 14 ( [link] ). Anything below 7.0 (ranging from 0.0 to 6.9) is acidic, and anything above 7.0 (from 7.1 to 14.0) is alkaline. Extremes in pH in either direction from 7.0 are usually considered inhospitable to life. The pH inside cells (6.8) and the pH in the blood (7.4) are both very close to neutral. However, the environment in the stomach is highly acidic, with a pH of 1 to 2. So how do the cells of the stomach survive in such an acidic environment? How do they homeostatically maintain the near neutral pH inside them? The answer is that they cannot do it and are constantly dying. New stomach cells are constantly produced to replace dead ones, which are digested by the stomach acids. It is estimated that the lining of the human stomach is completely replaced every seven to ten days. The pH scale measures the concentration of hydrogen ions (H + ) in a solution. (credit: modification of work by Edward Stevens) 

Watch this video for a straightforward explanation of pH and its logarithmic scale. 

[link] 

So how can organisms whose bodies require a near-neutral pH ingest acidic and basic substances (a human drinking orange juice, for example) and survive? Buffers are the key. Buffers readily absorb excess H + or OH , keeping the pH of the body carefully maintained in the narrow range required for survival. Maintaining a constant blood pH is critical to a person s well-being. The buffer maintaining the pH of human blood involves carbonic acid (H 2 CO 3 ), bicarbonate ion (HCO 3 ), and carbon dioxide (CO 2 ). When bicarbonate ions combine with free hydrogen ions and become carbonic acid, hydrogen ions are removed, moderating pH changes. Similarly, as shown in [link] , excess carbonic acid can be converted to carbon dioxide gas and exhaled through the lungs. This prevents too many free hydrogen ions from building up in the blood and dangerously reducing the blood s pH. Likewise, if too much OH is introduced into the system, carbonic acid will combine with it to create bicarbonate, lowering the pH. Without this buffer system, the body s pH would fluctuate enough to put survival in jeopardy. This diagram shows the body s buffering of blood pH levels. The blue arrows show the process of raising pH as more CO 2 is made. The purple arrows indicate the reverse process: the lowering of pH as more bicarbonate is created. 

Other examples of buffers are antacids used to combat excess stomach acid. Many of these over-the-counter medications work in the same way as blood buffers, usually with at least one ion capable of absorbing hydrogen and moderating pH, bringing relief to those that suffer heartburn after eating. The unique properties of water that contribute to this capacity to balance pH as well as water s other characteristics are essential to sustaining life on Earth. 

To learn more about water. Visit the U.S. Geological Survey Water Science for Schools All About Water! website. 

[link] Acid Rain When rain water is too acidic, it can greatly damage living organisms, such as this forest in the Czech Republic. 

[link] Section Summary 

Water has many properties that are critical to maintaining life. It is a polar molecule, allowing for the formation of hydrogen bonds. Hydrogen bonds allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent. The hydrogen bonds between water molecules cause the water to have a high heat capacity, meaning it takes a lot of added heat to raise its temperature. As the temperature rises, the hydrogen bonds between water continually break and form anew. This allows for the overall temperature to remain stable, although energy is added to the system. Water also exhibits a high heat of vaporization, which is key to how organisms cool themselves by the evaporation of sweat. Water s cohesive forces allow for the property of surface tension, whereas its adhesive properties are seen as water rises inside capillary tubes. The pH value is a measure of hydrogen ion concentration in a solution and is one of many chemical characteristics that is highly regulated in living organisms through homeostasis. Acids and bases can change pH values, but buffers tend to moderate the changes they cause. These properties of water are intimately connected to the biochemical and physical processes performed by living organisms, and life would be very different if these properties were altered, if it could exist at all. Review Questions 

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[link] Critical Thinking Questions 

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[link] Test Prep for AP Courses 

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[link] Footnotes 1 W. Humphrey W., A. Dalke, and K. Schulten, VMD Visual Molecular Dynamics, Journal of Molecular Graphics 14 (1996): 33-38. 2 W. Humphrey W., A. Dalke, and K. Schulten, VMD Visual Molecular Dynamics, Journal of Molecular Graphics 14 (1996): 33-38. Glossary acid molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution adhesion attraction between water molecules and other molecules base molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the concentration of hydrogen ions in a solution buffer substance that prevents a change in pH by absorbing or releasing hydrogen or hydroxide ions calorie amount of heat required to change the temperature of one gram of water by one degree Celsius capillary action occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the sides of the tubes cohesion intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension dissociation release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H + and OH - evaporation separation of individual molecules from the surface of a body of water, leaves of a plant, or the skin of an organism heat of vaporization of water high amount of energy required for liquid water to turn into water vapor hydrophilic describes ions or polar molecules that interact well with other polar molecules such as water hydrophobic describes uncharged non-polar molecules that do not interact well with polar molecules such as water litmus paper (also, pH paper) filter paper that has been treated with a natural water-soluble dye that changes its color as the pH of the environment changes so it can be used as a pH indicator pH paper see litmus paper pH scale scale ranging from zero to 14 that is inversely proportional to the concentration of hydrogen ions in a solution solvent substance capable of dissolving another substance specific heat capacity the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius sphere of hydration when a polar water molecule surrounds charged or polar molecules thus keeping them dissolved and in solution surface tension tension at the surface of a body of liquid that prevents the molecules from separating; created by the attractive cohesive forces between the molecules of the liquidCarbon Carbon 

In this section, you will investigate the following questions: Why is carbon important for life? How do functional groups determine the properties of biological molecules? Connection for AP Courses 

The unique properties of carbon make it a central part of biological molecules. With four valence electrons, carbon can covalently bond to oxygen, hydrogen, and nitrogen to form the many molecules important for cellular function. Carbon and hydrogen can form either hydrocarbon chains or rings. Functional groups , such as CH 3 (methyl) and COOH (carboxyl), are groups of atoms that give specific properties to hydrocarbon chains or rings that define their overall chemical characteristics and function. For example, the attachment of a carboxyl group (-COOH) makes a molecule more acidic, whereas the presence of an amine group (NH 2 ) makes a molecule more basic. (As we will explore in the next chapter, amino acids have both a carboxyl group and an amine group.) Isomers are molecules with the same molecular formula (i.e., same kinds and numbers of atoms), but different molecular structures resulting in different properties or functions. (Don t confuse isomer with isotope !) 

The information presented and examples highlighted in this section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 2.8 The student is able to justify the selection of data regarding the types of molecules that an animal, plant, or bacterium will take up as necessary building blocks and excrete as waste products. 

As a class, discuss how important carbon is in life forms. Include in the discussion how proteins, DNA, carbohydrates, biological molecules that distinguish life from inanimate materials, are composed of carbon. You can challenge students to consider a life form based on silicon instead of carbon, using this article as a catalyst. 

Cells are made of many complex molecules called macromolecules, such as proteins, nucleic acids (RNA and DNA), carbohydrates, and lipids. The macromolecules are a subset of organic molecules (any carbon-containing liquid, solid, or gas) that are especially important for life. The fundamental component for all of these macromolecules is carbon. The carbon atom has unique properties that allow it to form covalent bonds to as many as four different atoms, making this versatile element ideal to serve as the basic structural component, or backbone, of the macromolecules. 

Individual carbon atoms have an incomplete outermost electron shell. With an atomic number of 6 (six electrons and six protons), the first two electrons fill the inner shell, leaving four in the second shell. Therefore, carbon atoms can form up to four covalent bonds with other atoms to satisfy the octet rule. The methane molecule provides an example: it has the chemical formula CH 4 . Each of its four hydrogen atoms forms a single covalent bond with the carbon atom by sharing a pair of electrons. This results in a filled outermost shell. Hydrocarbons 

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen, such as methane (CH 4 ) described above. We often use hydrocarbons in our daily lives as fuels like the propane in a gas grill or the butane in a lighter. The many covalent bonds between the atoms in hydrocarbons store a great amount of energy, which is released when these molecules are burned (oxidized). Methane, an excellent fuel, is the simplest hydrocarbon molecule, with a central carbon atom bonded to four different hydrogen atoms, as illustrated in [link] . The geometry of the methane molecule, where the atoms reside in three dimensions, is determined by the shape of its electron orbitals. The carbons and the four hydrogen atoms form a shape known as a tetrahedron, with four triangular faces; for this reason, methane is described as having tetrahedral geometry. Methane has a tetrahedral geometry, with each of the four hydrogen atoms spaced 109.5 apart. 

As the backbone of the large molecules of living things, hydrocarbons may exist as linear carbon chains, carbon rings, or combinations of both. Furthermore, individual carbon-to-carbon bonds may be single, double, or triple covalent bonds, and each type of bond affects the geometry of the molecule in a specific way. This three-dimensional shape or conformation of the large molecules of life (macromolecules) is critical to how they function. Hydrocarbon Chains 

Hydrocarbon chains are formed by successive bonds between carbon atoms and may be branched or unbranched. Furthermore, the overall geometry of the molecule is altered by the different geometries of single, double, and triple covalent bonds, illustrated in [link] . The hydrocarbons ethane, ethene, and ethyne serve as examples of how different carbon-to-carbon bonds affect the geometry of the molecule. The names of all three molecules start with the prefix eth-, which is the prefix for two carbon hydrocarbons. The suffixes -ane, -ene, and -yne refer to the presence of single, double, or triple carbon-carbon bonds, respectively. Thus, propane, propene, and propyne follow the same pattern with three carbon molecules, butane, butane, and butyne for four carbon molecules, and so on. Double and triple bonds change the geometry of the molecule: single bonds allow rotation along the axis of the bond, whereas double bonds lead to a planar configuration and triple bonds to a linear one. These geometries have a significant impact on the shape a particular molecule can assume. When carbon forms single bonds with other atoms, the shape is tetrahedral. When two carbon atoms form a double bond, the shape is planar, or flat. Single bonds, like those found in ethane, are able to rotate. Double bonds, like those found in ethene cannot rotate, so the atoms on either side are locked in place. Hydrocarbon Rings 

So far, the hydrocarbons we have discussed have been aliphatic hydrocarbons , which consist of linear chains of carbon atoms. Another type of hydrocarbon, aromatic hydrocarbons , consists of closed rings of carbon atoms. Ring structures are found in hydrocarbons, sometimes with the presence of double bonds, which can be seen by comparing the structure of cyclohexane to benzene in [link] . Examples of biological molecules that incorporate the benzene ring include some amino acids and cholesterol and its derivatives, including the hormones estrogen and testosterone. The benzene ring is also found in the herbicide 2,4-D. Benzene is a natural component of crude oil and has been classified as a carcinogen. Some hydrocarbons have both aliphatic and aromatic portions; beta-carotene is an example of such a hydrocarbon. Carbon can form five-and six membered rings. Single or double bonds may connect the carbons in the ring, and nitrogen may be substituted for carbon. Isomers 

The three-dimensional placement of atoms and chemical bonds within organic molecules is central to understanding their chemistry. Molecules that share the same chemical formula but differ in the placement (structure) of their atoms and/or chemical bonds are known as isomers. Structural isomers (like butane and isobutene shown in figure a ) differ in the placement of their covalent bonds: both molecules have four carbons and ten hydrogens (C 4 H 10 ), but the different arrangement of the atoms within the molecules leads to differences in their chemical properties. For example, due to their different chemical properties, butane is suited for use as a fuel for cigarette lighters and torches, whereas isobutene is suited for use as a refrigerant and a propellant in spray cans. 

Geometric isomers , on the other hand, have similar placements of their covalent bonds but differ in how these bonds are made to the surrounding atoms, especially in carbon-to-carbon double bonds. In the simple molecule butene (C 4 H 8 ), the two methyl groups (CH 3 ) can be on either side of the double covalent bond central to the molecule, as illustrated in figure b . When the carbons are bound on the same side of the double bond, this is the cis configuration; if they are on opposite sides of the double bond, it is a trans configuration. In the trans configuration, the carbons form a more or less linear structure, whereas the carbons in the cis configuration make a bend (change in direction) of the carbon backbone. Molecules that have the same number and type of atoms arranged differently are called isomers. (a) Structural isomers have a different covalent arrangement of atoms. (b) Geometric isomers have a different arrangement of atoms around a double bond. (c) Enantiomers are mirror images of each other. 

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In triglycerides (fats and oils), long carbon chains known as fatty acids may contain double bonds, which can be in either the cis or trans configuration, illustrated in [link] . Fats with at least one double bond between carbon atoms are unsaturated fats. When some of these bonds are in the cis configuration, the resulting bend in the carbon backbone of the chain means that triglyceride molecules cannot pack tightly, so they remain liquid (oil) at room temperature. On the other hand, triglycerides with trans double bonds (popularly called trans fats), have relatively linear fatty acids that are able to pack tightly together at room temperature and form solid fats. In the human diet, trans fats are linked to an increased risk of cardiovascular disease, so many food manufacturers have reduced or eliminated their use in recent years. In contrast to unsaturated fats, triglycerides without double bonds between carbon atoms are called saturated fats, meaning that they contain all the hydrogen atoms available. Saturated fats are a solid at room temperature and usually of animal origin. These space-filling models show a cis (oleic acid) and a trans (eliadic acid) fatty acid. Notice the bend in the molecule cause by the cis configuration. Enantiomers 

Enantiomers are molecules that share the same chemical structure and chemical bonds but differ in the three-dimensional placement of atoms so that they are mirror images. As shown in [link] , an amino acid alanine example, the two structures are non-superimposable. In nature, only the L-forms of amino acids are used to make proteins. Some D forms of amino acids are seen in the cell walls of bacteria, but never in their proteins. Similarly, the D-form of glucose is the main product of photosynthesis and the L-form of the molecule is rarely seen in nature. D-alanine and L-alanine are examples of enantiomers or mirror images. Only the L-forms of amino acids are used to make proteins. Functional Groups 

Functional groups are groups of atoms that occur within molecules and confer specific chemical properties to those molecules. They are found along the carbon backbone of macromolecules. This carbon backbone is formed by chains and/or rings of carbon atoms with the occasional substitution of an element such as nitrogen or oxygen. Molecules with other elements in their carbon backbone are substituted hydrocarbons . 

The functional groups in a macromolecule are usually attached to the carbon backbone at one or several different places along its chain and/or ring structure. Each of the four types of macromolecules proteins, lipids, carbohydrates, and nucleic acids has its own characteristic set of functional groups that contributes greatly to its differing chemical properties and its function in living organisms. 

A functional group can participate in specific chemical reactions. Some of the important functional groups in biological molecules are shown in [link] ; they include: hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl. These groups play an important role in the formation of molecules like DNA, proteins, carbohydrates, and lipids. Functional groups are usually classified as hydrophobic or hydrophilic depending on their charge or polarity characteristics. An example of a hydrophobic group is the non-polar methane molecule. Among the hydrophilic functional groups is the carboxyl group found in amino acids, some amino acid side chains, and the fatty acids that form triglycerides and phospholipids. This carboxyl group ionizes to release hydrogen ions (H + ) from the COOH group resulting in the negatively charged COO - group; this contributes to the hydrophilic nature of whatever molecule it is found on. Other functional groups, such as the carbonyl group, have a partially negatively charged oxygen atom that may form hydrogen bonds with water molecules, again making the molecule more hydrophilic. The functional groups shown here are found in many different biological molecules. 

Hydrogen bonds between functional groups (within the same molecule or between different molecules) are important to the function of many macromolecules and help them to fold properly into and maintain the appropriate shape for functioning. Hydrogen bonds are also involved in various recognition processes, such as DNA complementary base pairing and the binding of an enzyme to its substrate, as illustrated in [link] . Hydrogen bonds connect two strands of DNA together to create the double-helix structure. Activity 

Carbon forms the backbone of important biological molecules. Create a mini-poster of a simple food chain that shows how carbon enters and exits each organism on the chain. Based on the food chain you created, make a prediction regarding the impact of human activity on the supply of carbon in the food chain. 

This activity is an application of Learning Objectives 2.8 and Science Practice 4.1 because the student is describing the types of molecules that organisms take up as necessary building blocks or excrete as wastes. 

The carbon cycle involves the movement of carbon between the atmosphere, biosphere, and oceans. Human activities have an effect on the carbon cycle, resulting in the rise of carbon dioxide in the atmosphere and acidification of the oceans due to the burning of fossil fuels. Deforestation leads to decreased absorption of carbon dioxide by plants for photosynthesis. Section Summary 

The unique properties of carbon make it a central part of biological molecules. Carbon binds to oxygen, hydrogen, and nitrogen covalently to form the many molecules important for cellular function. Carbon has four electrons in its outermost shell and can form four bonds. Carbon and hydrogen can form hydrocarbon chains or rings. Functional groups are groups of atoms that confer specific properties to hydrocarbon (or substituted hydrocarbon) chains or rings that define their overall chemical characteristics and function. Review Questions 

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[link] Glossary aliphatic hydrocarbon hydrocarbon consisting of a linear chain of carbon atoms aromatic hydrocarbon hydrocarbon consisting of closed rings of carbon atoms enantiomers molecules that share overall structure and bonding patterns, but differ in how the atoms are three dimensionally placed such that they are mirror images of each other functional group group of atoms that provides or imparts a specific function to a carbon skeleton geometric isomer isomer with similar bonding patterns differing in the placement of atoms alongside a double covalent bond hydrocarbon molecule that consists only of carbon and hydrogen isomers molecules that differ from one another even though they share the same chemical formula organic molecule any molecule containing carbon (except carbon dioxide) structural isomers molecules that share a chemical formula but differ in the placement of their chemical bonds substituted hydrocarbon hydrocarbon chain or ring containing an atom of another element in place of one of the backbone carbonsIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Foods such as bread, fruit, and cheese are rich sources of biological macromolecules. (credit: modification of work by Bengt Nyman) 

Food provides the body with the nutrients it needs to survive. Many of these critical nutrients are biological macromolecules, or large molecules, necessary for and built by living things. For example, the amino acids found in protein are needed to build healthy bone and muscle. The body uses fat molecules to build new cells, store energy, and for proper digestion. Carbohydrates are the primary source of the body s energy. Nucleic acids contain genetic information. 

While all living things, including humans, need macromolecules in their daily diet, an imbalance of any one of them can lead to health problems. For example, eating too much fat can lead to cardiovascular problems, and too much protein can lead to problems with the kidneys. Some people think that removing whole grains, such as wheat, from one s diet can be beneficial. However, scientists have found that to not be true for the majority of people. In fact, just the opposite may be true, because whole wheat contains more dietary fiber than other types of grains. The full research review can be found here . 

Stress from the beginning that most chemicals used by the body that are made up of smaller units strung together for specific functions are termed macromolecules. The same methods of combination and separation are used for all of these molecules.Synthesis of Biological Macromolecules Synthesis of Biological Macromolecules 

In this section, you will explore the following questions: How are complex macromolecule polymers synthesized from monomers? What is the difference between dehydration (or condensation) and hydrolysis reactions? Connection for AP Courses 

Living organisms need food to survive as it contains critical nutrients in the form of biological macromolecules. These large molecules are composed mainly of six elements sulfur, phosphorus, oxygen, nitrogen, carbon, and hydrogen (SPONCH) in different quantities and arrangements. Complex polymers are built from combinations of smaller monomers by dehydration synthesis, a chemical reaction in which a molecule of water is removed between two linking monomers. (Think of a train: each boxcar, including the caboose, represents a monomer, and the entire train is a polymer.) During digestion, polymers can be broken down by hydrolysis, or the addition of water. Both dehydration and hydrolysis reactions in cells are catalyzed by specific enzymes. Dehydration reactions typically require an investment of energy for new bond formation, whereas hydrolysis reactions typically release energy that can be used to power cellular processes. The four categories of macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Evidence supports scientists claim that the organic precursors of these biological molecules were present on primitive Earth. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 1 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A learning objective merges required content with one or more of the seven Science Practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life 

Enduring Understanding 1.D The origin of living systems is explained by natural processes. Essential Knowledge 1.D.1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. Science Practice 1.2 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 1.27 The student is able to describe a scientific hypothesis about the origin of life on Earth. Essential Knowledge 1.D.1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. Science Practice 3.3 The student can evaluate scientific questions. Learning Objective 1.28 The student is able to evaluate scientific questions based on hypotheses about the origin of life on Earth. 

Stress to the class that macromolecules are produced through dehydration synthesis and taken apart through hydrolysis. As the names imply, water is involved in both cases. Dehydration Synthesis 

As you ve learned, biological macromolecules are large molecules, necessary for life, that are built from smaller organic molecules. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids); each is an important cell component and performs a wide array of functions. Combined, these molecules make up the majority of a cell s dry mass (recall that water makes up the majority of its complete mass). Biological macromolecules are organic, meaning they contain carbon. In addition, they may contain hydrogen, oxygen, nitrogen, and additional minor elements. 

Most macromolecules are made from single subunits, or building blocks, called monomers . The monomers combine with each other using covalent bonds to form larger molecules known as polymers . In doing so, monomers release water molecules as byproducts. This type of reaction is known as dehydration synthesis , which means to put together while losing water. In the dehydration synthesis reaction depicted above, two molecules of glucose are linked together to form the disaccharide maltose. In the process, a water molecule is formed. 

Explain that when something is dehydrated, water is removed from it. Identify the specific hydrogen and specific hydroxyl group in the models or illustrations that are removed from two monomers to make the water. The remaining oxygen atom is used to link the two monomers together. 

Hydrolysis is the splitting or lysis of a bond between monomers within a polymer, using water. Explain that the two parts of water, the hydrogen atom and hydroxyl group, are added to the monomers after the separation from the polymer, with the result that each has a hydroxyl group where the oxygen molecule linking them was found. 

Ask the students what came first, biological chemicals or intact cells? Then discuss Miller and Urey s experiments. They can attempt to explain how these complex macromolecules could be created in the absence of life. The resulting molecules floated around in the atmosphere and eventually fell into the early oceans, then probably became incorporated into primitive cells. 

In a dehydration synthesis reaction ( [link] ), the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water. At the same time, the monomers share electrons and form covalent bonds. As additional monomers join, this chain of repeating monomers forms a polymer. Different types of monomers can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers: for example, glucose monomers are the constituents of starch, glycogen, and cellulose. Hydrolysis 

Polymers are broken down into monomers in a process known as hydrolysis, which means to split with water. Hydrolysis is a reaction in which a water molecule is used during the breakdown of another compound ( [link] ). During these reactions, the polymer is broken into two components: one part gains a hydrogen atom (H+) and the other gains a hydroxyl molecule (OH ) from a split water molecule. In the hydrolysis reaction shown here, the disaccharide maltose is broken down to form two glucose monomers with the addition of a water molecule. Note that this reaction is the reverse of the synthesis reaction shown in [link] . 

Dehydration and hydrolysis reactions are catalyzed, or sped up, by specific enzymes; dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy. These reactions are similar for most macromolecules, but each monomer and polymer reaction is specific for its class. For example, in our bodies, food is hydrolyzed, or broken down, into smaller molecules by catalytic enzymes in the digestive system. This allows for easy absorption of nutrients by cells in the intestine. Each macromolecule is broken down by a specific enzyme. For instance, carbohydrates are broken down by amylase, sucrase, lactase, or maltase. Proteins are broken down by the enzymes pepsin and peptidase, and by hydrochloric acid. Lipids are broken down by lipases. Breakdown of these macromolecules provides energy for cellular activities. Link to Learning 

Visit this site to see visual representations of dehydration synthesis and hydrolysis. 

[link] Recreating Primordial Earth 

Many people wonder how life formed on Earth. In 1953, Stanley Miller and Harold Urey developed an apparatus like the one shown in [link] to model early conditions on earth. They wanted to test if organic molecules could form from inorganic precursors believed to exist very early in Earth s history. They used boiling water to mimic early Earth s oceans. Steam from the ocean combined with methane, ammonia, and hydrogen gases from the early Earth s atmosphere and was exposed to electrical sparks to act as lightning. As the gas mixture cooled and condensed, it was found to contain organic compounds, such as amino acids and nucleotides. According to the abiogenesis theory, these organic molecules came together to form the earliest form of life about 3.5 billion years ago. (credit: Yassine Mrabet) Think About It 

How does Stanley Miller s and Harold Urey s model support the claim that organic precursors present on early Earth could have assembled into large, complex molecules necessary for life? What chemical ingredients were present on early Earth? 

This question is an application of Learning Objectives 1.27 and Science Practice 1.2 because students are asked to describe how the organic soup model supports the formation of complex polymers from simple organic precursors. Section Summary 

Proteins, carbohydrates, nucleic acids, and lipids are the four major classes of biological macromolecules large molecules necessary for life that are built from smaller organic molecules. Macromolecules are made up of single units known as monomers that are joined by covalent bonds to form larger polymers. The polymer is more than the sum of its parts: it acquires new characteristics, and leads to an osmotic pressure that is much lower than that formed by its ingredients; this is an important advantage in the maintenance of cellular osmotic conditions. A monomer joins with another monomer with the release of a water molecule, leading to the formation of a covalent bond. These types of reactions are known as dehydration or condensation reactions. When polymers are broken down into smaller units (monomers), a molecule of water is used for each bond broken by these reactions; such reactions are known as hydrolysis reactions. Dehydration and hydrolysis reactions are similar for all macromolecules, but each monomer and polymer reaction is specific to its class. Dehydration reactions typically require an investment of energy for new bond formation, while hydrolysis reactions typically release energy by breaking bonds. Review Questions 

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[link] Glossary biological macromolecule large molecule necessary for life that is built from smaller organic molecules dehydration synthesis (also, condensation) reaction that links monomer molecules together, releasing a molecule of water for each bond formed hydrolysis reaction causes breakdown of larger molecules into smaller molecules with the utilization of water monomer smallest unit of larger molecules called polymers polymer chain of monomer residues that is linked by covalent bonds; polymerization is the process of polymer formation from monomers by condensationCarbohydrates Carbohydrates 

By the end of this section, you will be able to: What is the role of carbohydrates in cells and in the extracellular materials of animals and plants? What are the different classifications of carbohydrates? How are monosaccharide building blocks assembled into disaccharides and complex polysaccharides? Connection for AP Courses 

Carbohydrates provide energy for the cell and structural support to plants, fungi, and arthropods such as insects, spiders, and crustaceans. Consisting of carbon, hydrogen, and oxygen in the ratio CH 2 O or carbon hydrated with water, carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides depending on the number of monomers in the macromolecule. Monosaccharides are linked by glycosidic bonds that form as a result of dehydration synthesis. Glucose, galactose, and fructose are common isomeric monosaccharides, whereas sucrose or table sugar is a disaccharide. Examples of polysaccharides include cellulose and starch in plants and glycogen in animals. Although storing glucose in the form of polymers like starch or glycogen makes it less accessible for metabolism, this prevents it from leaking out of cells or creating a high osmotic pressure that could cause excessive water uptake by the cell. Insects have a hard outer skeleton made of chitin, a unique nitrogen-containing polysaccharide. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 4.1 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 4.2 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 6.1 The student can justify claims with evidence. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 4.3 The student is able to use models to predict and justify that changes in the subcomponents of a biological polymer affect the functionality of the molecules. Molecular Structures 

Most people are familiar with carbohydrates, one type of macromolecule, especially when it comes to what we eat. To lose weight, some individuals adhere to low-carb diets. Athletes, in contrast, often carb-load before important competitions to ensure that they have enough energy to compete at a high level. Carbohydrates are, in fact, an essential part of our diet; grains, fruits, and vegetables are all natural sources of carbohydrates. Carbohydrates provide energy to the body, particularly through glucose, a simple sugar that is a component of starch and an ingredient in many staple foods. Carbohydrates also have other important functions in humans, animals, and plants. 

Carbohydrates can be represented by the stoichiometric formula (CH 2 O) n , where n is the number of carbons in the molecule. In other words, the ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. This formula also explains the origin of the term carbohydrate : the components are carbon ( carbo ) and the components of water (hence, hydrate ). Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides. Monosaccharides 

Monosaccharides (mono- = one ; sacchar- = sweet ) are simple sugars, the most common of which is glucose. In monosaccharides, the number of carbons usually ranges from three to seven. Most monosaccharide names end with the suffix -ose. If the sugar has an aldehyde group (the functional group with the structure R-CHO), it is known as an aldose, and if it has a ketone group (the functional group with the structure RC(=O)R'), it is known as a ketose. Depending on the number of carbons in the sugar, they also may be known as trioses (three carbons), pentoses (five carbons), and or hexoses (six carbons). See [link] for an illustration of the monosaccharides. Monosaccharides are classified based on the position of their carbonyl group and the number of carbons in the backbone. Aldoses have a carbonyl group (indicated in green) at the end of the carbon chain, and ketoses have a carbonyl group in the middle of the carbon chain. Trioses, pentoses, and hexoses have three, five, and six carbon backbones, respectively. 

The chemical formula for glucose is C 6 H 12 O 6 . In humans, glucose is an important source of energy. During cellular respiration, energy is released from glucose, and that energy is used to help make adenosine triphosphate (ATP). Plants synthesize glucose using carbon dioxide and water, and glucose in turn is used for energy requirements for the plant. Excess glucose is often stored as starch that is catabolized (the breakdown of larger molecules by cells) by humans and other animals that feed on plants. 

Galactose (part of lactose, or milk sugar) and fructose (found in sucrose, in fruit) are other common monosaccharides. Although glucose, galactose, and fructose all have the same chemical formula (C 6 H 12 O 6 ), they differ structurally and chemically (and are known as isomers) because of the different arrangement of functional groups around the asymmetric carbon; all of these monosaccharides have more than one asymmetric carbon ( (Figure) ). 

Glucose, galactose, and fructose are all hexoses. They are structural isomers, meaning they have the same chemical formula (C 6 H 12 O 6 ) but a different arrangement of atoms. 

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Glucose, galactose, and fructose are isomeric monosaccharides (hexoses), meaning they have the same chemical formula but have slightly different structures. Glucose and galactose are aldoses, and fructose is a ketose. 

Monosaccharides can exist as a linear chain or as ring-shaped molecules; in aqueous solutions they are usually found in ring forms ( [link] ). Glucose in a ring form can have two different arrangements of the hydroxyl group (OH) around the anomeric carbon (carbon 1 that becomes asymmetric in the process of ring formation). If the hydroxyl group is below carbon number 1 in the sugar, it is said to be in the alpha ( ) position, and if it is above the plane, it is said to be in the beta ( ) position. Five and six carbon monosaccharides exist in equilibrium between linear and ring forms. When the ring forms, the side chain it closes on is locked into an or position. Fructose and ribose also form rings, although they form five-membered rings as opposed to the six-membered ring of glucose. Disaccharides 

Disaccharides (di- = two ) form when two monosaccharides undergo a dehydration reaction (also known as a condensation reaction or dehydration synthesis). During this process, the hydroxyl group of one monosaccharide combines with the hydrogen of another monosaccharide, releasing a molecule of water and forming a covalent bond. A covalent bond formed between a carbohydrate molecule and another molecule (in this case, between two monosaccharides) is known as a glycosidic bond ( [link] ). Glycosidic bonds (also called glycosidic linkages) can be of the alpha or the beta type. Sucrose is formed when a monomer of glucose and a monomer of fructose are joined in a dehydration reaction to form a glycosidic bond. In the process, a water molecule is lost. By convention, the carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the carbonyl group. In sucrose, a glycosidic linkage is formed between carbon 1 in glucose and carbon 2 in fructose. 

Common disaccharides include lactose, maltose, and sucrose ( [link] ). Lactose is a disaccharide consisting of the monomers glucose and galactose. It is found naturally in milk. Maltose, or malt sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose. Common disaccharides include maltose (grain sugar), lactose (milk sugar), and sucrose (table sugar). Polysaccharides 

A long chain of monosaccharides linked by glycosidic bonds is known as a polysaccharide (poly- = many ). The chain may be branched or unbranched, and it may contain different types of monosaccharides. The molecular weight may be 100,000 daltons or more depending on the number of monomers joined. Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides. 

Starch is the stored form of sugars in plants and is made up of a mixture of amylose and amylopectin (both polymers of glucose). Plants are able to synthesize glucose, and the excess glucose, beyond the plant s immediate energy needs, is stored as starch in different plant parts, including roots and seeds. The starch in the seeds provides food for the embryo as it germinates and can also act as a source of food for humans and animals. The starch that is consumed by humans is broken down by enzymes, such as salivary amylases, into smaller molecules, such as maltose and glucose. The cells can then absorb the glucose. 

Starch is made up of glucose monomers that are joined by 1-4 or 1-6 glycosidic bonds. The numbers 1-4 and 1-6 refer to the carbon number of the two residues that have joined to form the bond. As illustrated in [link] , amylose is starch formed by unbranched chains of glucose monomers (only 1-4 linkages), whereas amylopectin is a branched polysaccharide ( 1-6 linkages at the branch points). Amylose and amylopectin are two different forms of starch. Amylose is composed of unbranched chains of glucose monomers connected by 1,4 glycosidic linkages. Amylopectin is composed of branched chains of glucose monomers connected by 1,4 and 1,6 glycosidic linkages. Because of the way the subunits are joined, the glucose chains have a helical structure. Glycogen (not shown) is similar in structure to amylopectin but more highly branched. Obtain copies of metabolic charts and use them to illustrate to students the connections between carbohydrate metabolism, lipid and amino acid production and breakdown. Have the students trace a molecule of glucose through its metabolism and identify the linkage points between macromolecule pathways. Ask the students what happens when excess sugar is ingested, at the molecular level. Have the class research the dangers of excess carbohydrate intake, including the health hazards that can result. Suggest that they research a condition relevant to their family. Carbohydrates or sugars include more than just table sugar. All have the basic formula CH 2 O. The ratio of carbon, hydrogen, and oxygen is always the same. The number of carbons determines the category of sugar. Biological sugars are usually pentoses (5 carbon or C 5 H 10 O 5 ) or hexoses (6 carbon or C 6 H 12 O 6 ). Monosaccharides are the building blocks of all sugars. If two are combined, they are disaccharides; if more than two are combined, they make up a large molecule called a polysaccharide. The type of linkage between the monomers determines whether animals can digest them. If the oxygen linking the monomers is oriented down relative to both adjacent carbons, it is called an alpha bond and can be digested. If the oxygen atom orients upward relative to one carbon and downward relative to the next, it is called a beta bond and is not able to be digested by animal digestive enzymes. In the United States, people consume large quantities of carbohydrates, often in the form of sugars. Carbohydrates provide an immediate source of energy when broken down. They are also involved in the metabolism of other types of macromolecules. Sugars can be converted into a number of amino acids, nucleic acids, and fats as needed by the body. 

Glycogen is the storage form of glucose in humans and other vertebrates and is made up of monomers of glucose. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis. 

Cellulose is the most abundant natural biopolymer. The cell wall of plants is mostly made of cellulose; this provides structural support to the cell. Wood and paper are mostly cellulosic in nature. Cellulose is made up of glucose monomers that are linked by 1-4 glycosidic bonds ( [link] ). In cellulose, glucose monomers are linked in unbranched chains by 1-4 glycosidic linkages. Because of the way the glucose subunits are joined, every glucose monomer is flipped relative to the next one resulting in a linear, fibrous structure. 

As shown in [link] , every other glucose monomer in cellulose is flipped over, and the monomers are packed tightly as extended long chains. This gives cellulose its rigidity and high tensile strength which is so important to plant cells. While the 1-4 linkage cannot be broken down by human digestive enzymes, herbivores such as cows, koalas, buffalos, and horses are able, with the help of the specialized flora in their stomach, to digest plant material that is rich in cellulose and use it as a food source. In these animals, certain species of bacteria and protists reside in the rumen (part of the digestive system of herbivores) and secrete the enzyme cellulase. The appendix of grazing animals also contains bacteria that digest cellulose, giving it an important role in the digestive systems of ruminants. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal. Termites are also able to break down cellulose because of the presence of other organisms in their bodies that secrete cellulases. 

Carbohydrates serve various functions in different animals. Arthropods (insects, crustaceans, and others) have an outer skeleton, called the exoskeleton, which protects their internal body parts (as seen in the bee in [link] ). This exoskeleton is made of the biological macromolecule chitin , which is a polysaccharide-containing nitrogen. It is made of repeating units of N-acetyl- -d-glucosamine, a modified sugar. Chitin is also a major component of fungal cell walls; fungi are neither animals nor plants and form a kingdom of their own in the domain Eukarya. Insects have a hard outer exoskeleton made of chitin, a type of polysaccharide. (credit: Louise Docker) Registered Dietitian 

Obesity is a worldwide health concern, and many diseases such as diabetes and heart disease are becoming more prevalent because of obesity. This is one of the reasons why registered dietitians are increasingly sought after for advice. Registered dietitians help plan nutrition programs for individuals in various settings. They often work with patients in health care facilities, designing nutrition plans to treat and prevent diseases. For example, dietitians may teach a patient with diabetes how to manage blood sugar levels by eating the correct types and amounts of carbohydrates. Dietitians may also work in nursing homes, schools, and private practices. 

To become a registered dietitian, one needs to earn at least a bachelor s degree in dietetics, nutrition, food technology, or a related field. In addition, registered dietitians must complete a supervised internship program and pass a national exam. Those who pursue careers in dietetics take courses in nutrition, chemistry, biochemistry, biology, microbiology, and human physiology. Dietitians must become experts in the chemistry and physiology (biological functions) of food (proteins, carbohydrates, and fats). Benefits of Carbohydrates 

Are carbohydrates good for you? People who wish to lose weight are often told that carbohydrates are bad for them and should be avoided. Some diets completely forbid carbohydrate consumption, claiming that a low-carbohydrate diet helps people to lose weight faster. However, carbohydrates have been an important part of the human diet for thousands of years; artifacts from ancient civilizations show the presence of wheat, rice, and corn in our ancestors storage areas. 

Carbohydrates should be supplemented with proteins, vitamins, and fats to be parts of a well-balanced diet. Calorie-wise, a gram of carbohydrate provides 4.3 Kcal. For comparison, fats provide 9 Kcal/g, a less desirable ratio. Carbohydrates contain soluble and insoluble elements; the insoluble part is known as fiber, which is mostly cellulose. Fiber has many uses; it promotes regular bowel movement by adding bulk, and it regulates the rate of consumption of blood glucose. Fiber also helps to remove excess cholesterol from the body: fiber binds to the cholesterol in the small intestine, then attaches to the cholesterol and prevents the cholesterol particles from entering the bloodstream, and then cholesterol exits the body via the feces. Fiber-rich diets also have a protective role in reducing the occurrence of colon cancer. In addition, a meal containing whole grains and vegetables gives a feeling of fullness. As an immediate source of energy, glucose is broken down during the process of cellular respiration, which produces ATP, the energy currency of the cell. Without the consumption of carbohydrates, the availability of instant energy would be reduced. Eliminating carbohydrates from the diet is not the best way to lose weight. A low-calorie diet that is rich in whole grains, fruits, vegetables, and lean meat, together with plenty of exercise and plenty of water, is the more sensible way to lose weight. 

For an additional perspective on carbohydrates, explore Biomolecules: the Carbohydrates through this interactive animation . 

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Use a molecular model kit to construct a polysaccharide from several different monosaccharide monomers. Explain how the structure of the polysaccharide determines its primary function as an energy storage molecule. Then use your model to describe how changes in structure result in changes in function. Think About It Explain why athletes often carb-load before a big game or tournament. Explain why it is difficult for some animals, including humans, to digest cellulose. Describe a structural difference between cellulose and starch, which is easily digested by humans. How are cows and other ruminants able to digest cellulose? 

This activity is an application of Learning Objective 4.1 and Science Practice 7.1 and Learning Objective 4.3 and science practices 6.1 and 6.4 because students first construct a model to show the connection between structure and function at the molecular level and then use the model to predict how changes in structure at the molecular level can affect a molecule s properties and function(s). 

The first Think About It question is an application of Learning Objective 4.1 and Science Practice 7.1 because students are connecting the structure of a molecule to its function. 

The second Think About It question is an application of Learning Objective 4.1 and Science Practice 7.1 and Learning Objective 4.2 and Science Practice 1.3 because students are using representations of the structural features of molecules to explain the relationship between its structure and its properties function(s). Section Summary 

Carbohydrates are a group of macromolecules that are a vital energy source for the cell and provide structural support to plant cells, fungi, and all of the arthropods that include lobsters, crabs, shrimp, insects, and spiders. Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides depending on the number of monomers in the molecule. Monosaccharides are linked by glycosidic bonds that are formed as a result of dehydration reactions, forming disaccharides and polysaccharides with the elimination of a water molecule for each bond formed. Glucose, galactose, and fructose are common monosaccharides, whereas common disaccharides include lactose, maltose, and sucrose. Starch and glycogen, examples of polysaccharides, are the storage forms of glucose in plants and animals, respectively. The long polysaccharide chains may be branched or unbranched. Cellulose is an example of an unbranched polysaccharide, whereas amylopectin, a constituent of starch, is a highly branched molecule. Storage of glucose, in the form of polymers like starch of glycogen, makes it slightly less accessible for metabolism; however, this prevents it from leaking out of the cell or creating a high osmotic pressure that could cause excessive water uptake by the cell. Review Questions 

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[link] Glossary carbohydrate biological macromolecule in which the ratio of carbon to hydrogen and to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells and form the a cellular exoskeleton of arthropods cellulose polysaccharide that makes up the cell wall of plants; provides structural support to the cell chitin type of carbohydrate that forms the outer skeleton of all arthropods that include crustaceans and insects; it also forms the cell walls of fungi disaccharide two sugar monomers that are linked together by a glycosidic bond glycogen storage carbohydrate in animals glycosidic bond bond formed by a dehydration reaction between two monosaccharides with the elimination of a water molecule monosaccharide single unit or monomer of carbohydrates polysaccharide long chain of monosaccharides; may be branched or unbranched starch storage carbohydrate in plantsProteins Proteins 

In this section, you will investigate the following questions: What are functions of proteins in cells and tissues? What is the relationship between amino acids and proteins? What are the four levels of protein organization? What is the relationship between protein shape and function? Connection for AP Courses 

Proteins are long chains of different sequences of the 20 amino acids that each contain an amino group (-NH 2 ), a carboxyl group (-COOH), and a variable group. (Think of how many protein words can be made with 20 amino acid letters ). Each amino acid is linked to its neighbor by a peptide bond formed by a dehydration reaction. A long chain of amino acids is known as a polypeptide. Proteins serve many functions in cells. They act as enzymes that catalyze chemical reactions, provide structural support, regulate the passage of substances across the cell membrane, protect against disease, and coordinate cell signaling pathways. Protein structure is organized at four levels: primary, secondary, tertiary, and quaternary. The primary structure is the unique sequence of amino acids. A change in just one amino acid can change protein structure and function. For example, sickle cell anemia results from just one amino acid substitution in a hemoglobin molecule consisting of 574 amino acids. The secondary structure consists of the local folding of the polypeptide by hydrogen bond formation; leading to the helix and pleated sheet conformations. In the tertiary structure, various interactions, e.g., hydrogen bonds, ionic bonds, disulfide linkages, and hydrophobic interactions between R groups, contribute to the folding of the polypeptide into different three-dimensional configurations. Most enzymes are of tertiary configuration. If a protein is denatured, loses its three-dimensional shape, it may no longer be functional. Environmental conditions such as temperature and pH can denature proteins. Some proteins, such as hemoglobin, are formed from several polypeptides, and the interactions of these subunits form the quaternary structure of proteins. 

Information presented and the examples highlighted in the section, support concepts and Learning Objectives outlined in Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven science practices. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 4.1 The student is able to explain the connection between the sequence and the subcomponents of a biological polymer and its properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 4.2 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 6.1 The student can justify claims with evidence. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 4.3 The student is able to use models to predict and justify that changes in the subcomponents of a biological polymer affect the functionality of the molecules. 

Twenty amino acids can be formed into a nearly limitless number of different proteins. The sequence of the amino acids ultimately determines the final configuration of the protein chain, giving the molecule its specific function. 

Emphasize that proteins have a variety of functions in the body. Table 3.1 contains some examples of these functions. Note that not all enzymes work under the same conditions. Amylase only works in an alkaline medium, such as in saliva, while pepsin works in the acid environment of the stomach. Discuss other materials that can be carried by protein in body fluids in addition to the substances listed for transport in the text. Proteins also carry insoluble lipids in the body and transport charged ions, such as calcium, magnesium, and zinc. Discuss another important structural protein, collagen, as it is found throughout the body, including in most connective tissues. Emphasize that not all hormones are proteins and that steroid based hormones were discussed in the previous section. 

The amino group of an amino acid loses an electron and becomes positively charged. The carboxyl group easily gains an electron, becoming negatively charged. This results in the amphipathic characteristic of amino acids and gives the compounds solubility in water. The presence of both functional groups also allows dehydration synthesis to join the individual amino acids into a peptide chain. 

Protein structure is explained as though it occurs in three to four discrete steps. In reality, the structural changes that result in a functional protein occur on a continuum. As the primary structure is formed off the ribosomes, the polypeptide chain goes through changes until the final configuration is achieved. Have the students imagine a strand of spaghetti as it cooks in a clear pot. Initially, the strand is straight (ignore the stiffness for this example). While it cooks, the strand will bend and twist and (again, for this example), fold itself into a loose ball made up of the strand of pasta. The resulting strand has a particular shape. Ask the students what types of chemical bonds or forces might affect protein structure. These shapes are dictated by the position of amino acids along the strand. Other forces will complete the folding and maintain the structure. Types and Functions of Proteins 

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective; they may serve in transport, storage, or membranes; or they may be toxins or enzymes. Each cell in a living system may contain thousands of proteins, each with a unique function. Their structures, like their functions, vary greatly. They are all, however, polymers of amino acids, arranged in a linear sequence. 

Enzymes , which are produced by living cells, are catalysts in biochemical reactions (like digestion) and are usually complex or conjugated proteins. Each enzyme is specific for the substrate (a reactant that binds to an enzyme) it acts on. The enzyme may help in breakdown, rearrangement, or synthesis reactions. Enzymes that break down their substrates are called catabolic enzymes, enzymes that build more complex molecules from their substrates are called anabolic enzymes, and enzymes that affect the rate of reaction are called catalytic enzymes. It should be noted that all enzymes increase the rate of reaction and, therefore, are considered to be organic catalysts. An example of an enzyme is salivary amylase, which hydrolyzes its substrate amylose, a component of starch. 

Hormones are chemical-signaling molecules, usually small proteins or steroids, secreted by endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction. For example, insulin is a protein hormone that helps to regulate the blood glucose level. The primary types and functions of proteins are listed in [link] . Protein Types and Functions Type Examples Functions Digestive Enzymes Amylase, lipase, pepsin, trypsin Help in digestion of food by catabolizing nutrients into monomeric units Transport Hemoglobin, albumin Carry substances in the blood or lymph throughout the body Structural Actin, tubulin, keratin Construct different structures, like the cytoskeleton Hormones Insulin, thyroxine Coordinate the activity of different body systems Defense Immunoglobulins Protect the body from foreign pathogens Contractile Actin, myosin Effect muscle contraction Storage Legume storage proteins, egg white (albumin) Provide nourishment in early development of the embryo and the seedling 

Proteins have different shapes and molecular weights; some proteins are globular in shape whereas others are fibrous in nature. For example, hemoglobin is a globular protein, but collagen, found in our skin, is a fibrous protein. Protein shape is critical to its function, and this shape is maintained by many different types of chemical bonds. Changes in temperature, pH, and exposure to chemicals may lead to permanent changes in the shape of the protein, leading to loss of function, known as denaturation . All proteins are made up of different arrangements of the same 20 types of amino acids. Amino Acids 

Amino acids are the monomers that make up proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, also known as the alpha ( ) carbon, bonded to an amino group (NH 2 ), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group ( [link] ). Amino acids have a central asymmetric carbon to which an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group) are attached. 

The name "amino acid" is derived from the fact that they contain both amino group and carboxyl-acid-group in their basic structure. As mentioned, there are 20 amino acids present in proteins. Ten of these are considered essential amino acids in humans because the human body cannot produce them and they are obtained from the diet. For each amino acid, the R group (or side chain) is different ( [link] ). 

There are 20 common amino acids commonly found in proteins, each with a different R group (variant group) that determines its chemical nature. 

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The chemical nature of the side chain determines the nature of the amino acid (that is, whether it is acidic, basic, polar, or nonpolar). For example, the amino acid glycine has a hydrogen atom as the R group. Amino acids such as valine, methionine, and alanine are nonpolar or hydrophobic in nature, while amino acids such as serine, threonine, and cysteine are polar and have hydrophilic side chains. The side chains of lysine and arginine are positively charged, and therefore these amino acids are also known as basic amino acids. Proline has an R group that is linked to the amino group, forming a ring-like structure. Proline is an exception to the standard structure of an animo acid since its amino group is not separate from the side chain ( [link] ). 

Amino acids are represented by a single upper case letter or a three-letter abbreviation. For example, valine is known by the letter V or the three-letter symbol val. Just as some fatty acids are essential to a diet, some amino acids are necessary as well. They are known as essential amino acids, and in humans they include isoleucine, leucine, and cysteine. Essential amino acids refer to those necessary for construction of proteins in the body, although not produced by the body; which amino acids are essential varies from organism to organism. 

The sequence and the number of amino acids ultimately determine the protein's shape, size, and function. Each amino acid is attached to another amino acid by a covalent bond, known as a peptide bond , which is formed by a dehydration reaction. The carboxyl group of one amino acid and the amino group of the incoming amino acid combine, releasing a molecule of water. The resulting bond is the peptide bond ( [link] ). Peptide bond formation is a dehydration synthesis reaction. The carboxyl group of one amino acid is linked to the amino group of the incoming amino acid. In the process, a molecule of water is released. 

The products formed by such linkages are called peptides. As more amino acids join to this growing chain, the resulting chain is known as a polypeptide. Each polypeptide has a free amino group at one end. This end is called the N terminal, or the amino terminal, and the other end has a free carboxyl group, also known as the C or carboxyl terminal. While the terms polypeptide and protein are sometimes used interchangeably, a polypeptide is technically a polymer of amino acids, whereas the term protein is used for a polypeptide or polypeptides that have combined together, often have bound non-peptide prosthetic groups, have a distinct shape, and have a unique function. After protein synthesis (translation), most proteins are modified. These are known as post-translational modifications. They may undergo cleavage, phosphorylation, or may require the addition of other chemical groups. Only after these modifications is the protein completely functional. 

Click through the steps of protein synthesis in this interactive tutorial . 

[link] The Evolutionary Significance of Cytochrome c 

Cytochrome c is an important component of the electron transport chain, a part of cellular respiration, and it is normally found in the cellular organelle, the mitochondrion. This protein has a heme prosthetic group, and the central ion of the heme gets alternately reduced and oxidized during electron transfer. Because this essential protein s role in producing cellular energy is crucial, it has changed very little over millions of years. Protein sequencing has shown that there is a considerable amount of cytochrome c amino acid sequence homology among different species; in other words, evolutionary kinship can be assessed by measuring the similarities or differences among various species DNA or protein sequences. 

Scientists have determined that human cytochrome c contains 104 amino acids. For each cytochrome c molecule from different organisms that has been sequenced to date, 37 of these amino acids appear in the same position in all samples of cytochrome c. This indicates that there may have been a common ancestor. On comparing the human and chimpanzee protein sequences, no sequence difference was found. When human and rhesus monkey sequences were compared, the single difference found was in one amino acid. In another comparison, human to yeast sequencing shows a difference in the 44th position. 

[link] Protein Structure 

As discussed earlier, the shape of a protein is critical to its function. For example, an enzyme can bind to a specific substrate at a site known as the active site. If this active site is altered because of local changes or changes in overall protein structure, the enzyme may be unable to bind to the substrate. To understand how the protein gets its final shape or conformation, we need to understand the four levels of protein structure: primary, secondary, tertiary, and quaternary. Primary Structure 

The unique sequence of amino acids in a polypeptide chain is its primary structure . For example, the pancreatic hormone insulin has two polypeptide chains, A and B, and they are linked together by disulfide bonds. The N terminal amino acid of the A chain is glycine, whereas the C terminal amino acid is asparagine ( [link] ). The sequences of amino acids in the A and B chains are unique to insulin. Bovine serum insulin is a protein hormone made of two peptide chains, A (21 amino acids long) and B (30 amino acids long). In each chain, primary structure is indicated by three-letter abbreviations that represent the names of the amino acids in the order they are present. The amino acid cysteine (cys) has a sulfhydryl (SH) group as a side chain. Two sulfhydryl groups can react in the presence of oxygen to form a disulfide (S-S) bond. Two disulfide bonds connect the A and B chains together, and a third helps the A chain fold into the correct shape. Note that all disulfide bonds are the same length, but are drawn different sizes for clarity. 

The unique sequence for every protein is ultimately determined by the gene encoding the protein. A change in nucleotide sequence of the gene s coding region may lead to a different amino acid being added to the growing polypeptide chain, causing a change in protein structure and function. In sickle cell anemia, the hemoglobin chain (a small portion of which is shown in [link] ) has a single amino acid substitution, causing a change in protein structure and function. Specifically, the amino acid glutamic acid is substituted by valine in the chain. What is most remarkable to consider is that a hemoglobin molecule is made up of two alpha chains and two beta chains that each consist of about 150 amino acids. The molecule, therefore, has about 600 amino acids. The structural difference between a normal hemoglobin molecule and a sickle cell molecule which dramatically decreases life expectancy is a single amino acid of the 600. What is even more remarkable is that those 600 amino acids are encoded by three nucleotides each, and the mutation is caused by a single base change (point mutation), 1 in 1800 bases. The beta chain of hemoglobin is 147 residues in length, yet a single amino acid substitution leads to sickle cell anemia. In normal hemoglobin, the amino acid at position seven is glutamate. In sickle cell hemoglobin, this glutamate is replaced by a valine. 

Because of this change of one amino acid in the chain, hemoglobin molecules form long fibers that distort the biconcave, or disc-shaped, red blood cells and assume a crescent or sickle shape, which clogs arteries ( [link] ). This can lead to myriad serious health problems such as breathlessness, dizziness, headaches, and abdominal pain for those affected by this disease. In this blood smear, visualized at 535x magnification using bright field microscopy, sickle cells are crescent shaped, while normal cells are disc-shaped. (credit: modification of work by Ed Uthman; scale-bar data from Matt Russell) Secondary Structure 

The local folding of the polypeptide in some regions gives rise to the secondary structure of the protein. The most common are the -helix and -pleated sheet structures ( [link] ). Both structures are the -helix structure the helix held in shape by hydrogen bonds. The hydrogen bonds form between the oxygen atom in the carbonyl group in one amino acid and another amino acid that is four amino acids farther along the chain. The -helix and -pleated sheet are secondary structures of proteins that form because of hydrogen bonding between carbonyl and amino groups in the peptide backbone. Certain amino acids have a propensity to form an -helix, while others have a propensity to form a -pleated sheet. 

Every helical turn in an alpha helix has 3.6 amino acid residues. The R groups (the variant groups) of the polypeptide protrude out from the -helix chain. In the -pleated sheet, the pleats are formed by hydrogen bonding between atoms on the backbone of the polypeptide chain. The R groups are attached to the carbons and extend above and below the folds of the pleat. The pleated segments align parallel or antiparallel to each other, and hydrogen bonds form between the partially positive nitrogen atom in the amino group and the partially negative oxygen atom in the carbonyl group of the peptide backbone. The -helix and -pleated sheet structures are found in most globular and fibrous proteins and they play an important structural role. Tertiary Structure 

The unique three-dimensional structure of a polypeptide is its tertiary structure ( [link] ). This structure is in part due to chemical interactions at work on the polypeptide chain. Primarily, the interactions among R groups creates the complex three-dimensional tertiary structure of a protein. The nature of the R groups found in the amino acids involved can counteract the formation of the hydrogen bonds described for standard secondary structures. For example, R groups with like charges are repelled by each other and those with unlike charges are attracted to each other (ionic bonds). When protein folding takes place, the hydrophobic R groups of nonpolar amino acids lay in the interior of the protein, whereas the hydrophilic R groups lay on the outside. The former types of interactions are also known as hydrophobic interactions. Interaction between cysteine side chains forms disulfide linkages in the presence of oxygen, the only covalent bond forming during protein folding. The tertiary structure of proteins is determined by a variety of chemical interactions. These include hydrophobic interactions, ionic bonding, hydrogen bonding and disulfide linkages. 

All of these interactions, weak and strong, determine the final three-dimensional shape of the protein. When a protein loses its three-dimensional shape, it may no longer be functional. Quaternary Structure 

In nature, some proteins are formed from several polypeptides, also known as subunits, and the interaction of these subunits forms the quaternary structure . Weak interactions between the subunits help to stabilize the overall structure. For example, insulin (a globular protein) has a combination of hydrogen bonds and disulfide bonds that cause it to be mostly clumped into a ball shape. Insulin starts out as a single polypeptide and loses some internal sequences in the presence of post-translational modification after the formation of the disulfide linkages that hold the remaining chains together. Silk (a fibrous protein), however, has a -pleated sheet structure that is the result of hydrogen bonding between different chains. 

The four levels of protein structure (primary, secondary, tertiary, and quaternary) are illustrated in [link] . The four levels of protein structure can be observed in these illustrations. (credit: modification of work by National Human Genome Research Institute) Denaturation and Protein Folding 

Each protein has its own unique sequence and shape that are held together by chemical interactions. If the protein is subject to changes in temperature, pH, or exposure to chemicals, the protein structure may change, losing its shape without losing its primary sequence in what is known as denaturation. Denaturation is often reversible because the primary structure of the polypeptide is conserved in the process if the denaturing agent is removed, allowing the protein to resume its function. Sometimes denaturation is irreversible, leading to loss of function. One example of irreversible protein denaturation is when an egg is fried. The albumin protein in the liquid egg white is denatured when placed in a hot pan. Not all proteins are denatured at high temperatures; for instance, bacteria that survive in hot springs have proteins that function at temperatures close to boiling. The stomach is also very acidic, has a low pH, and denatures proteins as part of the digestion process; however, the digestive enzymes of the stomach retain their activity under these conditions. 

Protein folding is critical to its function. It was originally thought that the proteins themselves were responsible for the folding process. Only recently was it found that often they receive assistance in the folding process from protein helpers known as chaperones (or chaperonins) that associate with the target protein during the folding process. They act by preventing aggregation of polypeptides that make up the complete protein structure, and they disassociate from the protein once the target protein is folded. 

For an additional perspective on proteins, view this animation called Biomolecules: The Proteins. 

[link] Think About It Predict what happens if even one amino acid is substituted for another in a polypeptide and provide a specific example. What categories of amino acids would you expect to find on the surface of a soluble protein, and which would you expect to find in the interior? What distribution of amino acids would you expect to find in a protein embedded in a lipid bilayer of a plasma cell membrane? Activity 

Folding is an important property of proteins, especially enzymes. Proteins have a narrow range of conditions in which they fold properly; outside that range, proteins can unfold (denature) and often cannot refold and become functional again. Investigate one disease that results from improper folding of a protein. Describe causes of the unfolding and consequences to the molecular structure of the polypeptide that result in the disease. 

The first Think About It question is an application of Learning Objective 4.3 and Science Practices 6.1 and 6.4 because students are predicting how a change in the subcomponents of a molecule can affect the properties of the molecule. 

The second Think About It question is an application of Learning Objective 4.2 and Science Practice 1.3 because students are using representations of molecules along with a model of the cell membrane to describe how the molecular structure of amino acids determines their location with a protein or other structure such as the phospholipid bilayer. 

The activity is an application of Learning Objective 4.1 and Science Practice 7.1, Learning Objective 4.2 and Science Practice 1.3, and Learning Objective 4.3 and Science Practices 6.1 and 6.4 because students are asked to explain how environmental factors can alter the molecular structure of a protein and how this change can result in a change in function, i.e., disease. Section Summary 

Proteins are a class of macromolecules that perform a diverse range of functions for the cell. They help in metabolism by providing structural support and by acting as enzymes, carriers, or hormones. The building blocks of proteins (monomers) are amino acids. Each amino acid has a central carbon that is linked to an amino group, a carboxyl group, a hydrogen atom, and an R group or side chain. There are 20 commonly occurring amino acids, each of which differs in the R group. Each amino acid is linked to its neighbors by a peptide bond. A long chain of amino acids is known as a polypeptide. 

Proteins are organized at four levels: primary, secondary, tertiary, and (optional) quaternary. The primary structure is the unique sequence of amino acids. The local folding of the polypeptide to form structures such as the helix and -pleated sheet constitutes the secondary structure. The overall three-dimensional structure is the tertiary structure. When two or more polypeptides combine to form the complete protein structure, the configuration is known as the quaternary structure of a protein. Protein shape and function are intricately linked; any change in shape caused by changes in temperature or pH may lead to protein denaturation and a loss in function. Review Questions 

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[link] Glossary alpha-helix structure ( -helix) type of secondary structure of proteins formed by folding of the polypeptide into a helix shape with hydrogen bonds stabilizing the structure amino acid monomer of a protein; has a central carbon or alpha carbon to which an amino group, a carboxyl group, a hydrogen, and an R group or side chain is attached; the R group is different for all 20 amino acids beta-pleated sheet ( -pleated) secondary structure found in proteins in which pleats are formed by hydrogen bonding between atoms on the backbone of the polypeptide chain chaperone (also, chaperonin) protein that helps nascent protein in the folding process denaturation loss of shape in a protein as a result of changes in temperature, pH, or exposure to chemicals enzyme catalyst in a biochemical reaction that is usually a complex or conjugated protein hormone chemical signaling molecule, usually protein or steroid, secreted by endocrine cells that act to control or regulate specific physiological processes peptide bond bond formed between two amino acids by a dehydration reaction polypeptide long chain of amino acids linked by peptide bonds primary structure linear sequence of amino acids in a protein protein biological macromolecule composed of one or more chains of amino acids quaternary structure association of discrete polypeptide subunits in a protein secondary structure regular structure formed by proteins by intramolecular hydrogen bonding between the oxygen atom of one amino acid residue and the hydrogen attached to the nitrogen atom of another amino acid residue tertiary structure three-dimensional conformation of a protein, including interactions between secondary structural elements; formed from interactions between amino acid side chainsLipids Lipids 

In this section, you will explore the following questions: What are the four major types of lipids? What are functions of fats in living organisms? What is the difference between saturated and unsaturated fatty acids? What is the molecular structure of phospholipids, and what is the role of phospholipids in cells? What is the basic structure of a steroid, and what are examples of their functions? How does cholesterol help maintain the fluid nature of the plasma membrane of cells? Connection for AP Courses 

Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids. A typical fat consists of three fatty acids bonded to one molecule of glycerol, forming triglycerides or triacylglycerols. The fatty acids may be saturated or unsaturated, depending on the presence or absence of double bonds in the hydrocarbon chain; a saturated fatty acid has the maximum number of hydrogen atoms bonded to carbon and, thus, only single bonds. In general, fats that are liquid at room temperature (e.g., canola oil) tend to be more unsaturated than fats that are solid at room temperature. In the food industry, oils are artificially hydrogenated to make them chemically more appropriate for use in processed foods. During this hydrogenation process, double bonds in the cis- conformation in the hydrocarbon chain may be converted to double bonds in the trans- conformation; unfortunately, trans fats have been shown to contribute to heart disease. Phospholipids are a special type of lipid associated with cell membranes and typically have a glycerol (or sphingosine) backbone to which two fatty acid chains and a phosphate-containing group are attached. As a result, phospholipids are considered amphipathic because they have both hydrophobic and hydrophilic components. (In Chapters 4 and 5 we will explore in more detail how the amphipathic nature of phospholipids in plasma cell membranes helps regulate the passage of substances into and out of the cell.) Although the molecular structures of steroids differ from that of triglycerides and phospholipids, steroids are classified as lipids based on their hydrophobic properties. Cholesterol is a type of steroid in animal cells plasma membrane. Cholesterol is also the precursor of steroid hormones such as testosterone. 

Information presented and the examples highlighted in the section, support concepts outlined in Big Idea 4 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 4.1 The student is able to explain the connection between the sequence and the subcomponents of a biological polymer and its properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 4.2 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 6.1 The student can justify claims with evidence. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 4.3 The student is able to use models to predict and justify that changes in the subcomponents of a biological polymer affect the functionality of the molecules. 

An important misconception to overcome for students is that lipids are not bad for the body. They are absolutely essential to the body s functions, including for growth and survival. 

Another concept to discuss is the insolubility of lipids in water. It is obvious in salad dressing, but why does it occur? If other functional groups are attached to lipids, they may contain some charges and give a degree of solubility to the lipid, but most lipids do not have any charges on the surface of the molecules and are not soluble in water, therefore, lipids are usually described as being hydrophobic. 

Insoluble lipids must be attached to proteins in the body to become soluble in body fluids. Have the class research the proteins that transport and carry lipids. Identify their contributions to health or sickness. Fats and Oils 

Lipids include a diverse group of compounds that are largely nonpolar in nature. This is because they are hydrocarbons that include mostly nonpolar carbon carbon or carbon hydrogen bonds. Non-polar molecules are hydrophobic ( water fearing ), or insoluble in water. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of fats. Lipids also provide insulation from the environment for plants and animals ( [link] ). For example, their water-repellant hydrophobic nature can help keep aquatic birds and mammals dry by forming a protective layer over fur or feathers. Lipids are also the building blocks of many hormones and an important constituent of all cellular membranes. Lipids include fats, waxes, phospholipids, and steroids. 

The difference between a fat and an oil is the state of the compound at room temperature (68 F). A fat is a solid or semisolid material and an oil is a liquid at this temperature. Both fats and oils are made up of glycerol and two or three fatty acid chains attached to its carbons by way of dehydration synthesis. A fatty acid is a chain of carbon atoms with hydrogen atoms attached at the open bonding sites. If the chain is fully saturated with hydrogen atoms, it is termed a saturated fat. This tends to give the compound a relatively stiff configuration and helps it to be a solid. If any of the hydrogen atoms are missing, it is called an unsaturated fat or oil. The absence of hydrogen atoms along the chain causes double bonds to form between adjacent carbon atoms, which results in a bend in the chain. This causes the molecules to push away other molecules near it, preventing the packing of fatty acid chains, and resulting in a liquid at room temperature. Fats tend to contain a high concentration of saturated fatty acids and oils tend to contain more unsaturated fatty acid chains. Both types have an effect on health; a high amount of saturated fats is significantly less healthy than a higher amount of unsaturated lipids. An exception trans fat, an unsaturated fat found in processed foods. Trans fats behave like a saturated lipid. 

Divide the class into three sections: section 1: dairy department; section 2: salad dressings, and section 3: potato chips.. Each section will visit the supermarket and identify which fats or oils are in five items in their category. Then, each section will prepare a chart listing their findings and share it with the class. Hydrophobic lipids in the fur of aquatic mammals, such as this river otter, protect them from the elements. (credit: Ken Bosma) 

A fat molecule consists of two main components glycerol and fatty acids. Glycerol is an organic compound (alcohol) with three carbons, five hydrogens, and three hydroxyl (OH) groups. Fatty acids have a long chain of hydrocarbons to which a carboxyl group is attached, hence the name fatty acid. The number of carbons in the fatty acid may range from 4 to 36; most common are those containing 12 18 carbons. In a fat molecule, the fatty acids are attached to each of the three carbons of the glycerol molecule with an ester bond through an oxygen atom ( [link] ). Triacylglycerol is formed by the joining of three fatty acids to a glycerol backbone in a dehydration reaction. Three molecules of water are released in the process. 

During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid , is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. 

Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid ( [link] ) Stearic acid is a common saturated fatty acid. 

When the hydrocarbon chain contains a double bond, the fatty acid is said to be unsaturated . Oleic acid is an example of an unsaturated fatty acid ( [link] ). Oleic acid is a common unsaturated fatty acid. 

Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). 

When a fatty acid has no double bonds, it is known as a saturated fatty acid because no more hydrogen may be added to the carbon atoms of the chain. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell s volume. In plants, fat or oil is stored in many seeds and is used as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond. If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat . The cis double bond causes a bend or a kink that prevents the fatty acids from packing tightly, keeping them liquid at room temperature ( [link] ). Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries. Saturated fatty acids have hydrocarbon chains connected by single bonds only. Unsaturated fatty acids have one or more double bonds. Each double bond may be in a cis or trans configuration. In the cis configuration, both hydrogens are on the same side of the hydrocarbon chain. In the trans configuration, the hydrogens are on opposite sides. A cis double bond causes a kink in the chain. Trans Fats 

In the food industry, oils are artificially hydrogenated to make them semi-solid and of a consistency desirable for many processed food products. Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis - conformation in the hydrocarbon chain may be converted to double bonds in the trans- conformation. 

Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans fats. Recent studies have shown that an increase in trans fats in the human diet may lead to an increase in levels of low-density lipoproteins (LDL), or bad cholesterol, which in turn may lead to plaque deposition in the arteries, resulting in heart disease. Many fast food restaurants have recently banned the use of trans fats, and food labels are required to display the trans fat content. Omega Fatty Acids 

Essential fatty acids are fatty acids required but not synthesized by the human body. Consequently, they have to be supplemented through ingestion via the diet. Omega -3 fatty acids (like that shown in [link] ) fall into this category and are one of only two known for humans (the other being omega-6 fatty acid). These are polyunsaturated fatty acids and are called omega-3 because the third carbon from the end of the hydrocarbon chain is connected to its neighboring carbon by a double bond. Alpha-linolenic acid is an example of an omega-3 fatty acid. It has three cis double bonds and, as a result, a curved shape. For clarity, the carbons are not shown. Each singly bonded carbon has two hydrogens associated with it, also not shown. 

The farthest carbon away from the carboxyl group is numbered as the omega ( ) carbon, and if the double bond is between the third and fourth carbon from that end, it is known as an omega-3 fatty acid. Nutritionally important because the body does not make them, omega-3 fatty acids include alpha-linoleic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), all of which are polyunsaturated. Salmon, trout, and tuna are good sources of omega-3 fatty acids. Research indicates that omega-3 fatty acids reduce the risk of sudden death from heart attacks, reduce triglycerides in the blood, lower blood pressure, and prevent thrombosis by inhibiting blood clotting. They also reduce inflammation, and may help reduce the risk of some cancers in animals. 

Like carbohydrates, fats have received a lot of bad publicity. It is true that eating an excess of fried foods and other fatty foods leads to weight gain. However, fats do have important functions. Many vitamins are fat soluble, and fats serve as a long-term storage form of fatty acids: a source of energy. They also provide insulation for the body. Therefore, healthy fats in moderate amounts should be consumed on a regular basis. 

This question is an application Learning Objective 4.3 and Science Practices 6.1 and 6.4 because students are predicting how a change in the subcomponents of a molecule can affect the properties of the molecule. 

A phospholipid is made of a phosphate group bonded to a glycerol that is linked to two fatty acid chains. One of the fatty acid chains is saturated and the other unsaturated. The saturated one is straight, while the unsaturated chain contains a bend. Phospholipids make up lipid bilayers, the main component of most plasma membranes and give it a fluid like property, a result of the fatty acid tails creating space between phospholipid molecules. 

The concept of a bent fatty acid tail contributing to the fluidity of a cell membrane can be difficult to visualize. Obtain some old fashioned, wooden clothes-pins. The knob at the top becomes a phosphate molecule. The two prongs of the pins become fatty acids. Both prongs are stiff, so they are saturated fatty acids. There are no unsaturated fatty acids in this demonstration. Hold a number of the pins tightly in your hand and ask a student to remove a pin in the center. They shouldn t be able to, as you are pressing the prongs of all of the pins together. This would be in a cell membrane without any unsaturated fatty acids pushing adjacent chains away, creating spaces that allow the membrane to behave like a fluid. Think About It 

Explain why trans fats have been banned from some restaurants. How are trans fats made, and what effect does a simple chemical change have on the properties of the lipid? Waxes 

Wax covers the feathers of some aquatic birds and the leaf surfaces of some plants. Because of the hydrophobic nature of waxes, they prevent water from sticking on the surface ( [link] ). Waxes are made up of long fatty acid chains esterified to long-chain alcohols. Waxy coverings on some leaves are made of lipids. (credit: Roger Griffith) Phospholipids 

Phospholipids are major constituents of the plasma membrane, the outermost layer of animal cells. Like fats, they are composed of fatty acid chains attached to a glycerol or sphingosine backbone. Instead of three fatty acids attached as in triglycerides, however, there are two fatty acids forming diacylglycerol, and the third carbon of the glycerol backbone is occupied by a modified phosphate group ( [link] ). A phosphate group alone attached to a diaglycerol does not qualify as a phospholipid; it is phosphatidate (diacylglycerol 3-phosphate), the precursor of phospholipids. The phosphate group is modified by an alcohol. Phosphatidylcholine and phosphatidylserine are two important phospholipids that are found in plasma membranes. A phospholipid is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone. The phosphate may be modified by the addition of charged or polar chemical groups. Two chemical groups that may modify the phosphate, choline and serine, are shown here. Both choline and serine attach to the phosphate group at the position labeled R via the hydroxyl group indicated in green. 

A phospholipid is an amphipathic molecule, meaning it has a hydrophobic and a hydrophilic part. The fatty acid chains are hydrophobic and cannot interact with water, whereas the phosphate-containing group is hydrophilic and interacts with water ( [link] ). The phospholipid bilayer is the major component of all cellular membranes. The hydrophilic head groups of the phospholipids face the aqueous solution. The hydrophobic tails are sequestered in the middle of the bilayer. 

The head is the hydrophilic part, and the tail contains the hydrophobic fatty acids. In a membrane, a bilayer of phospholipids forms the matrix of the structure, the fatty acid tails of phospholipids face inside, away from water, whereas the phosphate group faces the outside, aqueous side ( [link] ). 

Phospholipids are responsible for the dynamic nature of the plasma membrane. If a drop of phospholipids is placed in water, it spontaneously forms a structure known as a micelle, where the hydrophilic phosphate heads face the outside and the fatty acids face the interior of this structure. 

Fats are amphiphilic molecules. In other words, the long hydrocarbon tail is hydrophobic, and the glycerol part of the molecule is hydrophilic. When in water, fats will arrange themselves into a ball called a micelle so that the hydrophilic heads are on the outer surface, and the hydrophobic tails are on the inside where they are protected from the surrounding water. 

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The predominant steroid found in the body is cholesterol, which is used variously by the body to form steroidal hormones and give flexibility to cells, such as red blood cells, which must change their shape to get through blood vessels and tissues. Steroids 

Unlike the phospholipids and fats discussed earlier, steroids have a fused ring structure. Although they do not resemble the other lipids, they are grouped with them because they are also hydrophobicand insoluble in water. All steroids have four linked carbon rings and several of them, like cholesterol, have a short tail ( [link] ). Many steroids also have the OH functional group, which puts them in the alcohol classification (sterols). Steroids such as cholesterol and cortisol are composed of four fused hydrocarbon rings. 

Cholesterol is the most common steroid. Cholesterol is mainly synthesized in the liver and is the precursor to many steroid hormones such as testosterone and estradiol, which are secreted by the gonads and endocrine glands. It is also the precursor to Vitamin D. Cholesterol is also the precursor of bile salts, which help in the emulsification of fats and their subsequent absorption by cells. Although cholesterol is often spoken of in negative terms by lay people, it is necessary for proper functioning of the body. It is a component of the plasma membrane of animal cells and is found within the phospholipid bilayer. Being the outermost structure in animal cells, the plasma membrane is responsible for the transport of materials and cellular recognition and it is involved in cell-to-cell communication. 

For an additional perspective on lipids, explore the interactive animation Biomolecules: The Lipids . 

[link] Section Summary 

Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types include fats and oils, waxes, phospholipids, and steroids. Fats are a stored form of energy and are also known as triacylglycerols or triglycerides. Fats are made up of fatty acids and either glycerol or sphingosine. Fatty acids may be unsaturated or saturated, depending on the presence or absence of double bonds in the hydrocarbon chain. If only single bonds are present, they are known as saturated fatty acids. Unsaturated fatty acids may have one or more double bonds in the hydrocarbon chain. Phospholipids make up the matrix of membranes. They have a glycerol or sphingosine backbone to which two fatty acid chains and a phosphate-containing group are attached. Steroids are another class of lipids. Their basic structure has four fused carbon rings. Cholesterol is a type of steroid and is an important constituent of the plasma membrane, where it helps to maintain the fluid nature of the membrane. It is also the precursor of steroid hormones such as testosterone. Review Questions 

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[link] Glossary lipid macromolecule that is nonpolar and insoluble in water omega fat type of polyunsaturated fat that is required by the body; the numbering of the carbon omega starts from the methyl end or the end that is farthest from the carboxylic end phospholipid major constituent of the membranes; composed of two fatty acids and a phosphate-containing group attached to a glycerol backbone saturated fatty acid long-chain of hydrocarbon with single covalent bonds in the carbon chain; the number of hydrogen atoms attached to the carbon skeleton is maximized steroid type of lipid composed of four fused hydrocarbon rings forming a planar structure trans fat fat formed artificially by hydrogenating oils, leading to a different arrangement of double bond(s) than those found in naturally occurring lipids triacylglycerol (also, triglyceride) fat molecule; consists of three fatty acids linked to a glycerol molecule unsaturated fatty acid long-chain hydrocarbon that has one or more double bonds in the hydrocarbon chain wax lipid made of a long-chain fatty acid that is esterified to a long-chain alcohol; serves as a protective coating on some feathers, aquatic mammal fur, and leavesNucleic Acids Nucleic Acids 

In this section, you will investigate the following questions: What are the two types of nucleic acid? What is the structure and role of DNA? What is the structure and roles of RNA? Connection for AP Courses 

Nucleic acids (DNA and RNA) comprise the fourth group of biological macromolecules and contain phosphorus (P) in addition to carbon, hydrogen, oxygen, and nitrogen. Conserved through evolution in all organisms, nucleic acids store and transmit hereditary information. As will be explored in more detail in Chapters 14-17, DNA contains the instructions for the synthesis of proteins by dictating the sequences of amino acids in polypeptides through processes known as transcription and translation. Nucleic acids are made up of nucleotides; in turn, each nucleotide consists of a pentose sugar (deoxyribose in DNA and ribose in RNA), a nitrogenous base (adenine, cytosine, guanine, and thymine or uracil), and a phosphate group. DNA carries the genetic blueprint of the cell that is passed from parent to offspring via cell division. DNA has a double-helical structure with the two strands running in opposite directions (antiparallel), connected by hydrogen bonds and complementary to each other. In DNA, purines pair with pyrimidines: adenine pairs with thymine (A-T), and cytosine pairs with guanine (C-G). In RNA, uracil replaces thymine to pair with adenine (U-A). RNA also differs from DNA in that it is single-stranded and has many forms, such as messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA) that all participate in the synthesis of proteins. MicroRNAs (miRNAs) regulate the use of mRNA. The flow of genetic information is usually DNA RNA protein, also known as the Central Dogma of Life. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 and Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA and, in some cases, that RNA are the primary sources of heritable information. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.6 The student can predict how a change in a specific DNA or RNA sequence can result in changes in gene expression. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 4.1 The student is able to explain the connection between the sequence and the subcomponents of a biological polymer and its properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 4.2 The student is able to refine representations and models to explain how the subcomponents of a biological polymer and their sequence determine the properties of that polymer. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 6.1 The student can justify claims with evidence. 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 4.3 The student is able to use models to predict and justify that changes in the subcomponents of a biological polymer affect the functionality of the molecules. 

Use Table 3.2 to illustrate the major differences between DNA and RNA. 

A polynucleotide is not formed through a traditional dehydration synthesis reaction. Instead of removing the components of water from the monomers, a phosphate group is removed from each to form the linkage. 

The primary functions of nucleic acids is to store genetic information needed to produce proteins and to facilitate the appropriate linkages between amino acids. Another function of nucleic acids is in energy transfer, discussed in a later chapter. 

The concept of the double helix of DNA can be challenging to understand. Ask the students to imagine a rope ladder with the top of the right side labeled 3 and the other end of that side labeled 5. The top of the left side is labeled 5 and the other end 3, so the numbers are going in opposite directions on opposite sides of the ladder, giving the sides of the structure an antiparallel orientation. Now imagine grabbing the ladder from the top and twisting. That is a double helix. It is double because there are two sides to it. You might try to draw a ladder, with its labels; then, ask the students to imagine it twisting. Another possibility is to have students use pipe cleaners to build the double helix. 

RNA usually exists as a single strand. Messenger RNA (mRNA) can be found in the nucleus, where it mirrors the sequence of nucleotides found in DNA, and in the cytoplasm, where it delivers its message to ribosomes for protein assembly. Ribosomes are made of ribosomal RNA (rRNA) and protein. Transfer RNA (tRNA) carries amino acids to the ribosomes for attachment to a developing protein. MicroRNA (miRNA) are the smallest RNA molecules and their role involves the regulation of gene expression by interfering with the expression of certain mRNA. 

Some viruses contain double stranded RNA, but plants and animals do not. DNA and RNA 

Nucleic acids are the most important macromolecules for the continuity of life. They carry the genetic blueprint of a cell and carry instructions for the functioning of the cell. 

The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) . DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope. 

The entire genetic content of a cell is known as its genome, and the study of genomes is genomics. In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. A chromosome may contain tens of thousands of genes. Many genes contain the information to make protein products; other genes code for RNA products. DNA controls all of the cellular activities by turning the genes on or off. 

The other type of nucleic acid, RNA, is mostly involved in protein synthesis. The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. This intermediary is the messenger RNA (mRNA) . Other types of RNA like rRNA, tRNA, and microRNA are involved in protein synthesis and its regulation. 

DNA and RNA are made up of monomers known as nucleotides . The nucleotides combine with each other to form a polynucleotide , DNA or RNA. Each nucleotide is made up of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ( [link] ). Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups. A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Carbon residues in the pentose are numbered 1 through 5 (the prime distinguishes these residues from those in the base, which are numbered without using a prime notation). The base is attached to the 1 position of the ribose, and the phosphate is attached to the 5 position. When a polynucleotide is formed, the 5 phosphate of the incoming nucleotide attaches to the 3 hydroxyl group at the end of the growing chain. Two types of pentose are found in nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). Deoxyribose is similar in structure to ribose, but it has an H instead of an OH at the 2 position. Bases can be divided into two categories: purines and pyrimidines. Purines have a double ring structure, and pyrimidines have a single ring. 

The nitrogenous bases, important components of nucleotides, are organic molecules and are so named because they contain carbon and nitrogen. They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus, decreases the hydrogen ion concentration in its environment, making it more basic. Each nucleotide in DNA contains one of four possible nitrogenous bases: adenine (A), guanine (G) cytosine (C), and thymine (T). 

Adenine and guanine are classified as purines . The primary structure of a purine is two carbon-nitrogen rings. Cytosine, thymine, and uracil are classified as pyrimidines which have a single carbon-nitrogen ring as their primary structure ( [link] ). Each of these basic carbon-nitrogen rings has different functional groups attached to it. In molecular biology shorthand, the nitrogenous bases are simply known by their symbols A, T, G, C, and U. DNA contains A, T, G, and C whereas RNA contains A, U, G, and C. 

The pentose sugar in DNA is deoxyribose, and in RNA, the sugar is ribose ( [link] ). The difference between the sugars is the presence of the hydroxyl group on the second carbon of the ribose and hydrogen on the second carbon of the deoxyribose. The carbon atoms of the sugar molecule are numbered as 1 , 2 , 3 , 4 , and 5 (1 is read as one prime ). The phosphate residue is attached to the hydroxyl group of the 5 carbon of one sugar and the hydroxyl group of the 3 carbon of the sugar of the next nucleotide, which forms a 5 3 phosphodiester linkage. The phosphodiester linkage is not formed by simple dehydration reaction like the other linkages connecting monomers in macromolecules: its formation involves the removal of two phosphate groups. A polynucleotide may have thousands of such phosphodiester linkages. DNA Double-Helix Structure 

DNA has a double-helix structure ( [link] ). The sugar and phosphate lie on the outside of the helix, forming the backbone of the DNA. The nitrogenous bases are stacked in the interior, like the steps of a staircase, in pairs; the pairs are bound to each other by hydrogen bonds. Every base pair in the double helivx is separated from the next base pair by 0.34 nm. The two strands of the helix run in opposite directions, meaning that the 5 carbon end of one strand will face the 3 carbon end of its matching strand. (This is referred to as antiparallel orientation and is important to DNA replication and in many nucleic acid interactions.) Native DNA is an antiparallel double helix. The phosphate backbone (indicated by the curvy lines) is on the outside, and the bases are on the inside. Each base from one strand interacts via hydrogen bonding with a base from the opposing strand. (credit: Jerome Walker/Dennis Myts) 

Only certain types of base pairing are allowed. For example, a certain purine can only pair with a certain pyrimidine. This means A can pair with T, and G can pair with C, as shown in [link] . This is known as the base complementary rule. In other words, the DNA strands are complementary to each other. If the sequence of one strand is AATTGGCC, the complementary strand would have the sequence TTAACCGG. During DNA replication, each strand is copied, resulting in a daughter DNA double helix containing one parental DNA strand and a newly synthesized strand. 

In a double stranded DNA molecule, the two strands run antiparallel to one another so that one strand runs 5 to 3 and the other 3 to 5 . The phosphate backbone is located on the outside, and the bases are in the middle. Adenine forms hydrogen bonds (or base pairs) with thymine, and guanine base pairs with cytosine. 

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Ribonucleic acid, or RNA, is mainly involved in the process of protein synthesis under the direction of DNA. RNA is usually single-stranded and is made of ribonucleotides that are linked by phosphodiester bonds. A ribonucleotide in the RNA chain contains ribose (the pentose sugar), one of the four nitrogenous bases (A, U, G, and C), and the phosphate group. 

There are four major types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), and microRNA (miRNA). The first, mRNA, carries the message from DNA, which controls all of the cellular activities in a cell. If a cell requires a certain protein to be synthesized, the gene for this product is turned on and the messenger RNA is synthesized in the nucleus. The RNA base sequence is complementary to the coding sequence of the DNA from which it has been copied. However, in RNA, the base T is absent and U is present instead. If the DNA strand has a sequence AATTGCGC, the sequence of the complementary RNA is UUAACGCG. In the cytoplasm, the mRNA interacts with ribosomes and other cellular machinery ( [link] ). A ribosome has two parts: a large subunit and a small subunit. The mRNA sits in between the two subunits. A tRNA molecule recognizes a codon on the mRNA, binds to it by complementary base pairing, and adds the correct amino acid to the growing peptide chain. 

The mRNA is read in sets of three bases known as codons. Each codon codes for a single amino acid. In this way, the mRNA is read and the protein product is made. Ribosomal RNA (rRNA) is a major constituent of ribosomes on which the mRNA binds. The rRNA ensures the proper alignment of the mRNA and the ribosomes; the rRNA of the ribosome also has an enzymatic activity (peptidyl transferase) and catalyzes the formation of the peptide bonds between two aligned amino acids. Transfer RNA (tRNA) is one of the smallest of the four types of RNA, usually 70 90 nucleotides long. It carries the correct amino acid to the site of protein synthesis. It is the base pairing between the tRNA and mRNA that allows for the correct amino acid to be inserted in the polypeptide chain. microRNAs are the smallest RNA molecules and their role involves the regulation of gene expression by interfering with the expression of certain mRNA messages. [link] summarizes features of DNA and RNA. Features of DNA and RNA DNA RNA Function Carries genetic information Involved in protein synthesis Location Remains in the nucleus Leaves the nucleus Structure Double helix Usually single-stranded Sugar Deoxyribose Ribose Pyrimidines Cytosine, thymine Cytosine, uracil Purines Adenine, guanine Adenine, guanine 

Even though the RNA is single stranded, most RNA types show extensive intramolecular base pairing between complementary sequences, creating a predictable three-dimensional structure essential for their function. 

As you have learned, information flow in an organism takes place from DNA to RNA to protein. DNA dictates the structure of mRNA in a process known as transcription , and RNA dictates the structure of protein in a process known as translation . This is known as the Central Dogma of Life, which holds true for all organisms; however, exceptions to the rule occur in connection with viral infections. 

To learn more about DNA, explore the Howard Hughes Medical Institute BioInteractive animations on the topic of DNA. 

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Using construction paper, markers, and scissors, construct a model of DNA with at least 8 nucleotides. Then, use the model to distinguish between DNA and RNA and hypothesize how the DNA molecule is replicated during cell division. (Keep your molecule to model the processes of transcription and translation that you will explore in Chapter 15.) Think About It 

A mutation occurs, and cytosine is replaced with adenine. Explain how this affects how the changed strand will base pair with its complimentary strand of DNA. 

This activity is an application of Learning Objective 3.1 and Science Practice 6.5, Learning Objective 4.1 and Science Practice 7.1, and Learning Objective 4.2 and Science Practice 1.3 because students are constructing a model to explain how DNA stores genetic information, to distinguish between DNA and RNA, and to propose a method how DNA is replicated in cell division. 

The Think About It question is an application of Learning Objective 3.6 and Science Practice 6.4 and Learning Objective 4.3 and Science Practices 6.1 and 6.4 because students are predicting how a change in a DNA sequence can affect the genetic information it carries. Section Summary 

Nucleic acids are molecules made up of nucleotides that direct cellular activities such as cell division and protein synthesis. Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. There are two types of nucleic acids: DNA and RNA. DNA carries the genetic blueprint of the cell and is passed on from parents to offspring (in the form of chromosomes). It has a double-helical structure with the two strands running in opposite directions, connected by hydrogen bonds, and complementary to each other. RNA is single-stranded and is made of a pentose sugar (ribose), a nitrogenous base, and a phosphate group. RNA is involved in protein synthesis and its regulation. Messenger RNA (mRNA) is copied from the DNA, is exported from the nucleus to the cytoplasm, and contains information for the construction of proteins. Ribosomal RNA (rRNA) is a part of the ribosomes at the site of protein synthesis, whereas transfer RNA (tRNA) carries the amino acid to the site of protein synthesis. microRNA regulates the use of mRNA for protein synthesis. Review Questions 

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[link] Glossary deoxyribonucleic acid (DNA) double-helical molecule that carries the hereditary information of the cell messenger RNA (mRNA) RNA that carries information from DNA to ribosomes during protein synthesis nucleic acid biological macromolecule that carries the genetic blueprint of a cell and carries instructions for the functioning of the cell nucleotide monomer of nucleic acids; contains a pentose sugar, one or more phosphate groups, and a nitrogenous base phosphodiester linkage covalent chemical bond that holds together the polynucleotide chains with a phosphate group linking two pentose sugars of neighboring nucleotides polynucleotide long chain of nucleotides purine type of nitrogenous base in DNA and RNA; adenine and guanine are purines pyrimidine type of nitrogenous base in DNA and RNA; cytosine, thymine, and uracil are pyrimidines ribonucleic acid (RNA) single-stranded, often internally base paired, molecule that is involved in protein synthesis ribosomal RNA (rRNA) RNA that ensures the proper alignment of the mRNA and the ribosomes during protein synthesis and catalyzes the formation of the peptide linkage transcription process through which messenger RNA forms on a template of DNA transfer RNA (tRNA) RNA that carries activated amino acids to the site of protein synthesis on the ribosome translation process through which RNA directs the formation of proteinIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" (a) Nasal sinus cells (viewed with a light microscope), (b) onion cells (viewed with a light microscope), and (c) Vibrio tasmaniensis bacterial cells (seen through a scanning electron microscope) are from very different organisms, yet all share certain characteristics of basic cell structure. (credit a: modification of work by Ed Uthman, MD; credit b: modification of work by Umberto Salvagnin; credit c: modification of work by Anthony D'Onofrio, William H. Fowle, Eric J. Stewart, and Kim Lewis of the Lewis Lab at Northeastern University; scale-bar data from Matt Russell) 

Close your eyes and picture a brick wall. What is the basic building block of that wall? A single brick, of course. Like a brick wall, your body is composed of basic building blocks called cells. 

Your body has many kinds of cells, each specialized for a specific purpose. Just as a home is made from a variety of building materials, the human body is constructed from many cell types. For example, epithelial cells protect the surface of the body and cover the organs and body cavities within. Bone cells help to support and protect the body. Immune system cells fight invading pathogens. Additionally, blood cells carry nutrients and oxygen throughout the body while removing carbon dioxide and other waste. Each of these cell types plays a vital role during the growth, development, and ongoing maintenance of the body. In spite of their enormous variety, however, cells from all organisms even organisms as diverse as bacteria, onion, and human share certain fundamental characteristics. 

In humans, before a cell develops into its specialized type, it is called a stem cell. A stem cell is a cell that has not undergone the changes involved in specialization. In this state, it may differentiate to become one of many different specialized cells, and it may divide to produce more stem cells. Under normal circumstances, once a cell becomes specialized, it remains that way. However, scientists have been working on coaxing stem cells in the laboratory to become a particular specialization. For example, scientists at the Cincinnati Children s Hospital Medical Center have learned how to use stem cells to grow stomach tissue in plastic cell and tissue culture dishes. This accomplishment will enable researchers to study gastric human diseases, such as stomach cancer. You can read more about it here . 

Stem cells retain the potential to become many different types of cell. Totipotent stem cells such as the zygote and the cells in the very early stages of the dividing embryo can become any cell in the body. By the time the zygote has undergone sufficient division the 16-cell stage, some cells are committed to a particular path and are called pluripotent. Each pluripotent cell has a large potential and can differentiate into many of the types of cells that ultimately make up the adult organism. Multipotent cells are still present in numerous adult tissues such as the bone marrow and the brain and can differentiate into a number of different cell types, albeit within a narrow range. The classic example is seen in the formation of blood cells in the bone marrow. An unspecialized cell in the blood lineage may become a red blood cell or a white blood cell, but not a muscle cell. Further down the path of differentiation, the precursor of a white blood cell lineage has lost the capability to develop into a red blood cell; however, it can still differentiate into one of the several kinds of white blood cells. 

For the most part, differentiated cells retain all of their genetic material, making it a possibility to reverse the differentiation process and turn specialized adult cells into pluripotent stem cells. This is the key to the experiment described in the warm up. 

Ask students what would happen if they chose a career in the future and were never allowed to change their decision (e.g., Once an accountant, always an accountant. ) 

Compare totipotent cells to students in middle school with all possibilities wide open. In high school, some differentiation has taken place by choosing AP classes. As they progress through their studies, some paths may be closing. Ask students to compare differentiation to academic paths. At which stage of their education, are students totipotent? (Possible answers: elementary, middle or high school) When do students become pluripotent? (Possible answers: choice of secondary education, vocational school, college) When do they become multipotent? (Possible answers: choice of major, graduate school) Emphasize that it is easier for a student in one natural science to switch to a different natural science, for example, go from physics to geology. Can you change drastically career at a later stage in life? This is comparable to developing pluripotent adult stem cells. The DNA is still there. 

Embryonic cells cannot become any cell in the body. They are multipotent, not totipotent. Explain that the ability to differentiate pluripotent adult stem cells in organoids is a major breakthrough because it is an alternative to using embryonic tissue.Studying Cells Studying Cells 

In this section, you will explore the following questions: What is the role of cells in organisms? What is the difference between light microscopy and electron microscopy? What is the cell theory? 

An introduction to the principle of microscopy will facilitate the discussion of the various types of instruments. Explain to students the concepts of magnification, resolution, and contrast, which together contribute to the quality of microscopy. In particular, explain that resolution is determined by the smallest wavelength in visible light in the light microscope and the distance separating two atoms in solid material in a transmission electron microscope. 

Review with students the tenets of the cell theory, because the cell, as the fundamental unit of life, is at the foundation of all biological classes. Life cannot be divided into pieces smaller than the cell and still be considered independent life. Therefore, viruses are considered particles, not cells, because viruses, for one, cannot replicate on their own. All living organisms are made of one or more cells. Those cells are similar in size. Why are cells so similar in size, no matter how large the organism itself grows? The main answer lies in how surface area and volume scale with cell radius and how these parameters affect exchange with the environment. This is covered in the next module. 

Beginners consider magnification the most important quality of a microscope. Magnification without resolution yields a very large but blurry image which does not inform the viewer on the nature of the specimen. Illustrate the point by referring to the resolution of a photographic image or a YouTube video with which many students are familiar. Emphasize the importance of contrast. A cell is transparent unless it contains colored components or dense structures. Ask students for examples of such structures. Answers may include chloroplasts, chromoplasts, nuclei or other dense structures. Connection for AP Courses 

A cell is the smallest unit of a living thing. A living thing, whether made of one cell (like bacteria) or many cells (like a human), is called an organism. Thus, cells are the basic building blocks of all organisms. 

Several cells of one kind that interconnect with each other and perform a shared function form tissues, several tissues combine to form an organ (your stomach, heart, or brain), and several organs make up an organ system (such as the digestive system, circulatory system, or nervous system). Several systems that function together form an organism (like a human being). Here, we will examine the structure and function of cells. 

There are many types of cells, all grouped into one of two broad categories: prokaryotic and eukaryotic. For example, both animal and plant cells are classified as eukaryotic cells, whereas bacterial cells are classified as prokaryotic. Before discussing the criteria for determining whether a cell is prokaryotic or eukaryotic, let s first examine how biologists study cells. Microscopy 

Cells vary in size. With few exceptions, individual cells cannot be seen with the naked eye, so scientists use microscopes (micro- = small ; -scope = to look at ) to study them. A microscope is an instrument that magnifies an object. Most photographs of cells are taken with a microscope, and these images can also be called micrographs. 

The optics of a microscope s lenses change the orientation of the image that the user sees. A specimen that is right-side up and facing right on the microscope slide will appear upside-down and facing left when viewed through a microscope, and vice versa. Similarly, if the slide is moved left while looking through the microscope, it will appear to move right, and if moved down, it will seem to move up. This occurs because microscopes use two sets of lenses to magnify the image. Because of the manner by which light travels through the lenses, this system of two lenses produces an inverted image (binocular, or dissecting microscopes, work in a similar manner, but include an additional magnification system that makes the final image appear to be upright). Light Microscopes 

To give you a sense of cell size, a typical human red blood cell is about eight millionths of a meter or eight micrometers (abbreviated as eight m) in diameter; the head of a pin of is about two thousandths of a meter (two mm) in diameter. That means about 250 red blood cells could fit on the head of a pin. 

Most student microscopes are classified as light microscopes ( [link] a ). Visible light passes and is bent through the lens system to enable the user to see the specimen. Light microscopes are advantageous for viewing living organisms, but since individual cells are generally transparent, their components are not distinguishable unless they are colored with special stains. Staining, however, usually kills the cells. 

Light microscopes commonly used in the undergraduate college laboratory magnify up to approximately 400 times. Two parameters that are important in microscopy are magnification and resolving power. Magnification is the process of enlarging an object in appearance. Resolving power is the ability of a microscope to distinguish two adjacent structures as separate: the higher the resolution, the better the clarity and detail of the image. When oil immersion lenses are used for the study of small objects, magnification is usually increased to 1,000 times. In order to gain a better understanding of cellular structure and function, scientists typically use electron microscopes. (a) Most light microscopes used in a college biology lab can magnify cells up to approximately 400 times and have a resolution of about 200 nanometers. (b) Electron microscopes provide a much higher magnification, 100,000x, and a have a resolution of 50 picometers. (credit a: modification of work by "GcG"/Wikimedia Commons; credit b: modification of work by Evan Bench) Electron Microscopes 

In contrast to light microscopes, electron microscopes ( [link] b ) use a beam of electrons instead of a beam of light. Not only does this allow for higher magnification and, thus, more detail ( [link] ), it also provides higher resolving power. The method used to prepare the specimen for viewing with an electron microscope kills the specimen. Electrons have short wavelengths (shorter than photons) that move best in a vacuum, so living cells cannot be viewed with an electron microscope. 

In a scanning electron microscope, a beam of electrons moves back and forth across a cell s surface, creating details of cell surface characteristics. In a transmission electron microscope, the electron beam penetrates the cell and provides details of a cell s internal structures. As you might imagine, electron microscopes are significantly more bulky and expensive than light microscopes. (a) These Salmonella bacteria appear as tiny purple dots when viewed with a light microscope. (b) This scanning electron microscope micrograph shows Salmonella bacteria (in red) invading human cells (yellow). Even though subfigure (b) shows a different Salmonella specimen than subfigure (a), you can still observe the comparative increase in magnification and detail. (credit a: modification of work by CDC/Armed Forces Institute of Pathology, Charles N. Farmer, Rocky Mountain Laboratories; credit b: modification of work by NIAID, NIH; scale-bar data from Matt Russell) 

For another perspective on cell size, try the HowBig interactive at this site . 

[link] Cell Theory 

The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. Despite the limitations of his now-ancient lenses, van Leeuwenhoek observed the movements of protista (a type of single-celled organism) and sperm, which he collectively termed animalcules. 

In a 1665 publication called Micrographia , experimental scientist Robert Hooke coined the term cell for the box-like structures he observed when viewing cork tissue through a lens. In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells. 

By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory , which states that all living things are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory. Cytotechnologist 

Have you ever heard of a medical test called a Pap smear ( [link] )? In this test, a doctor takes a small sample of cells from the uterine cervix of a patient and sends it to a medical lab where a cytotechnologist stains the cells and examines them for any changes that could indicate cervical cancer or a microbial infection. 

Cytotechnologists (cyto- = cell ) are professionals who study cells via microscopic examinations and other laboratory tests. They are trained to determine which cellular changes are within normal limits and which are abnormal. Their focus is not limited to cervical cells; they study cellular specimens that come from all organs. When they notice abnormalities, they consult a pathologist, who is a medical doctor who can make a clinical diagnosis. 

Cytotechnologists play a vital role in saving people s lives. When abnormalities are discovered early, a patient s treatment can begin sooner, which usually increases the chances of a successful outcome. These uterine cervix cells, viewed through a light microscope, were obtained from a Pap smear. Normal cells are on the left. The cells on the right are infected with human papillomavirus (HPV). Notice that the infected cells are larger; also, two of these cells each have two nuclei instead of one, the normal number. (credit: modification of work by Ed Uthman, MD; scale-bar data from Matt Russell) Section Summary 

A cell is the smallest unit of life. Most cells are so tiny that they cannot be seen with the naked eye. Therefore, scientists use microscopes to study cells. Electron microscopes provide higher magnification, higher resolution, and more detail than light microscopes. The unified cell theory states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells. Review Questions 

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[link] Glossary cell theory see unified cell theory electron microscope an instrument that magnifies an object using a beam of electrons passed and bent through a lens system to visualize a specimen light microscope an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen microscope an instrument that magnifies an object unified cell theory a biological concept that states that all organisms are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cellsProkaryotic Cells Prokaryotic Cells 

In this section, you will explore the following questions: What are the major structures of prokaryotic cells? What limits the size of a cell? Connection for AP Courses 

According to the cell theory, all living organisms, from bacteria to humans, are composed of cells, the smallest units of living matter. Often too small to be seen without a microscope, cells come in all sizes and shapes, and their small size allows for a large surface area-to-volume ratio that enables a more efficient exchange of nutrients and wastes with the environment. 

There are three basic types of cells: archaea, bacteria, and eukaryotes. Both archaea and bacteria are classified as prokaryotes, whereas cells of animals, plants, fungi, and protists are eukaryotes. Archaea are a unique group of organisms and likely evolved in the harsh conditions of early Earth and are still prevalent today in extreme environments, such as hot springs and polar regions. All cells share features that reflect their evolution from a common ancestor; these features are 1) a plasma membrane that separates the cell from its environment; 2) cytoplasm comprising the jelly-like cytosol inside the cell; 3) ribosomes that are important for the synthesis of proteins, and 4) DNA to store and transmit hereditary information. 

Prokaryotes may also have a cell wall that acts as an extra layer of protection against the external environment. The term prokaryote means before nucleus, and prokaryotes do not have nuclei. Rather, their DNA exists as a single circular chromosome in the central part of the cell called the nucleoid. Some bacterial cells also have circular DNA plasmids that often carry genes for resistance to antibiotics (Chapter 17). Other common prokaryotic cell features include flagella and pili. 

The content presented in this section supports the learning objectives outlined in Big Idea 1 and Big Idea 2 of the AP Biology Curriculum Framework. The AP Learning Objectives merge essential knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.D The origin of living systems is explained by natural processes. Essential Knowledge 1.D.2 Scientific evidence from many different disciplines supports models of the origin of life. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 1.32 The student is able to justify the selection of geological, physical, chemical, and biological data that reveal early Earth conditions. Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 2.6 The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion. Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.7 The student will be able to explain how cell sizes and shapes affect the overall rate of nutrient intake and the rate of waste elimination. 

The major structures common to all bacteria are depicted in Figure 4.5. The cell wall contains a complex structural component, the peptidoglycan layer, which has yet to be observed in any eukaryotic cell. This peptidoglycan layer is made of a network of alternating modified complex sugar units, the glycans, joined by peptide cross-bridges. This rigid structure contributes to the shape of bacterial cells and protects them against changes in osmotic pressure in the environment. Antibiotics such as penicillin interfere with the synthesis of the peptidoglycan layers and cause bacterial cells to lyse without affecting the human host. 

Many bacterial cells contain plasmids: small, extrachromosomal rings of double-stranded DNA which can replicate independently of the bacterial chromosome and often carry genes which confer resistance to antibiotics. Bacteria readily transfer plasmids to other bacterial cells by a mechanism called horizontal gene transfer, thereby spreading antibiotic resistance. 

Cells at the lower end of the size spectrum are limited on just how small they can be. To illustrate, compare a bacterial cell to a bag packed for camping in the wilderness. In order to make the camping trip possible, the bag must contain a minimum amount of supplies and equipment. Here, introduce the concept of prokaryotes, bacteria and archaea. Prokaryotes are the most successful organisms on the planet. They probably appeared first during evolution and occupy every possible environment. 

Surface area-to-volume ratio limits the maximum size of a cell. Nutrients and intermediates enter the cell by diffusion. As the cell increases in size, the volume increase outpaces the surface area increase, and the cell size exceeds the capacity of the surface area to adequately exchange nutrients and waste with the external environment. 

All bacteria cause disease. This misconception started with the germ theory of disease when it became clear that some of the most feared diseases were caused by microorganisms. In fact, very few microorganisms are actually pathogens. The balance between control of infectious diseases and reasonable sanitary standards is often misunderstood. Excess hygiene is thought to have caused an increase in asthma and other immune system imbalances between a human host and the human microbiome. Ask students if one can be too clean. The notion that improved hygiene has led to increases in the prevalence of allergies and asthma is called the hygiene hypothesis. 

Until recently, surface area-to-volume ratio was considered the main factor in determining the limits of cell sizes. New research opened the possibility that other factors such as avoiding predators, cell division mechanics and environment also contribute to size and shape determination. The topic is reviewed in the following article: 

Young, K. D. (2006). The Selective Value of Bacterial Shape. Microbiology and Molecular Biology Reviews , 70 (3), 660 703. doi:10.1128 /MMBR.00001-06 

Show in class, if possible, the following video from HHMI on the discovery of microbial life by Leeuwenhoek. 

Use the video to discuss what set apart the single lens microscope of Leeuwenhoek. Challenge students by asking them why the rapid development of microbiology, the so-called golden age, happened in the nineteenth century, close to 200 years after the discovery of microbial life. One of the main reasons is the germ theory of disease. Once the connection was made between devastating diseases and microbes, the interest in microorganisms soared. 

Ask students if they can think of ways in which bacteria are beneficial and write them on the board. Include the obvious ones such as probiotics; food and fermentation; and the less obvious ones such as to stimulate the immune system, biofuels, bioremediation (here mention cleaning oil spills), and synthesis of useful products (antibiotics). 

Ask students if a cell in a 30-meter long blue whale is considerably larger than a cell in a tiny water flea at 3 mm long. Record answers on the board. Cells are similar in size because there are constraints on how large and how small they can be and still be functionally independent entities. 

Cells fall into one of two broad categories: prokaryotic and eukaryotic. Only the predominantly single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes (pro- = before ; -kary- = nucleus ). Cells of animals, plants, fungi, and protists are all eukaryotes (ceu- = true ) and are made up of eukaryotic cells. Components of Prokaryotic Cells 

All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, which synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways. 

A prokaryote is a simple, mostly single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in a central part of the cell: the nucleoid ( [link] ). This figure shows the generalized structure of a prokaryotic cell. All prokaryotes have chromosomal DNA localized in a nucleoid, ribosomes, a cell membrane, and a cell wall. The other structures shown are present in some, but not all, bacteria. 

While the Earth is approximately 4.6 billion years old, the earliest fossil evidence for life are of microbial mats that date back to 3.5 billion years. 

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Most prokaryotes have a peptidoglycan cell wall and many have a polysaccharide capsule ( [link] ). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion. Pili are used to exchange genetic material during a type of reproduction called conjugation. Fimbriae are used by bacteria to attach to a host cell. Career Connection 

Microbiologist The most effective action anyone can take to prevent the spread of contagious illnesses is to wash his or her hands. Why? Because microbes (organisms so tiny that they can only be seen with microscopes) are ubiquitous. They live on doorknobs, money, your hands, and many other surfaces. If someone sneezes into his hand and touches a doorknob, and afterwards you touch that same doorknob, the microbes from the sneezer s mucus are now on your hands. If you touch your hands to your mouth, nose, or eyes, those microbes can enter your body and could make you sick. 

However, not all microbes (also called microorganisms) cause disease; most are actually beneficial. You have microbes in your gut that make vitamin K. Other microorganisms are used to ferment beer and wine. 

Microbiologists are scientists who study microbes. Microbiologists can pursue a number of careers. Not only do they work in the food industry, they are also employed in the veterinary and medical fields. They can work in the pharmaceutical sector, serving key roles in research and development by identifying new sources of antibiotics that could be used to treat bacterial infections. 

Environmental microbiologists may look for new ways to use specially selected or genetically engineered microbes for the removal of pollutants from soil or groundwater, as well as hazardous elements from contaminated sites. These uses of microbes are called bioremediation technologies. Microbiologists can also work in the field of bioinformatics, providing specialized knowledge and insight for the design, development, and specificity of computer models of, for example, bacterial epidemics. Cell Size 

At 0.1 to 5.0 m in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10 to 100 m ( [link] ). The small size of prokaryotes allows ions and organic molecules that enter them to quickly diffuse to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly diffuse out. This is not the case in eukaryotic cells, which have developed different structural adaptations to enhance intracellular transport. This figure shows relative sizes of microbes on a logarithmic scale (recall that each unit of increase in a logarithmic scale represents a 10-fold increase in the quantity being measured). 

Small size, in general, is necessary for all cells, whether prokaryotic or eukaryotic. Let s examine why that is so. First, we ll consider the area and volume of a typical cell. Not all cells are spherical in shape, but most tend to approximate a sphere. You may remember from your high school geometry course that the formula for the surface area of a sphere is 4 r 2 , while the formula for its volume is 4 r 3 /3. Thus, as the radius of a cell increases, its surface area increases as the square of its radius, but its volume increases as the cube of its radius (much more rapidly). Therefore, as a cell increases in size, its surface area-to-volume ratio decreases. This same principle would apply if the cell had the shape of a cube ( see this figure ). If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient. One way to become more efficient is to divide; another way is to develop organelles that perform specific tasks. These adaptations lead to the development of more sophisticated cells called eukaryotic cells. Visual Connections 

Notice that as a cell increases in size, its surface area-to-volume ratio decreases. When there is insufficient surface area to support a cell s increasing volume, a cell will either divide or die. The cell on the left has a volume of 1 mm 3 and a surface area of 6 mm 2 , with a surface area-to-volume ratio of 6 to 1, whereas the cell on the right has a volume of 8 mm 3 and a surface area of 24 mm 2 , with a surface area-to-volume ratio of 3 to 1. 

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Create an annotated diagram to explain how approximately 300 million alveoli in a human lung increases surface area for gas exchange to the size of a tennis court. Use the diagram to explain how the cellular structures of alveoli, capillaries, and red blood cells allow for rapid diffusion of O 2 and CO 2 among them. Think About It 

Which of the following cells would likely exchange nutrients and wastes with its environment more efficiently: a spherical cell with a diameter of 5 m or a cubed-shaped cell with a side length of 7 m? Provide a quantitative justification for your answer based on surface area-to-volume ratios. 

This activity is an application of Learning Objective 2.6 and Science Practice 6.2 because students are creating a diagram to explain diffusion rates across membranes. 

The Think about it question is an application of Learning Objective 2.6 and Science Practice 2.2 and Learning Objective 2.7 and Science Practice 2.2 because they need to calculate surface area-to-volume ratios for two different shapes and sizes of cells to predict which one procures nutrients or eliminates wastes more efficiently. 

Cell sizes and shapes can vary. The longest cells are neurons that start at the brain and reach the limbs. Other examples of large cells include bird eggs, skeletal muscle cells, and the marine algae Caulerpa and Acetabularia . These are exceptional cells and have unusual solutions to the surface area-to-volume challenge. 

The main point is that the alveoli cover a large surface because they are essentially very small beads packed in two large bags, the lungs. The sum of the individual surface areas of these microscopic beads is equivalent to the surface of a tennis court (roughly 200 m 2 for singles). The surface area of a sphere is 4 r 2 . If the average diameter of an alveolus is 300 m, which is equal to 0.3mm, the average surface area of an alveolus is 4 ( 0.3 mm 2 ) 2 0 . 3 mm 2 4 ( 0.3 mm 2 ) 2 0 . 3 mm 2 

1mm=10 -3 m 

1mm 2 =1mm*1mm=10 -3 m*10 -3 m=10 -6 m 2 

The surface area of an alveolus in square meters is equal to 0.3 10 -6 m 2 . If there are 300 million (300 10 6 ) alveoli in one lung, the total surface is equal to about 90m 2 which is almost half the area of a tennis court! 

Demonstration 

Take a piece of paper and crumple it to show how a large surface area can fit in a small volume. 

The alveoli are squamous cells, thin and flat; the capillaries have the diameter of a hair (from the Latin capellus , meaning hair ). Oxygen diffuses through very thin barriers only two cell membranes thick. 

Calculate: 

The dimension of the sphere given is the diameter. It must be divided by 2 to obtain the value for the radius. 

D=5 m and r=D/2=2.5 m 

Surface area of sphere: 4 r 2 =78.54 m 2 

Volume: 4/3 r 3 = 65.45 m 3 

Surface area-to-volume ratio=1.2 m -1 

Cube 

Surface area: 6s 2 =294 m 2 

Volume: s 3 = 343 m 3 

Surface area to volume: 294/343 =0.86 m -1 

The sphere has a larger surface area to volume ratio and would exchange chemicals with the environment more efficiently to support its volume, even though the cube has a larger surface area. 

Desai B.V., Harmon, R. M. and Green K. J. (2009). Desmosomes at a glance Journal of Cell Science 122, 4401-4407 Section Summary 

Prokaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Most have peptidoglycan cell walls and many have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1 to 5.0 m. 

As a cell increases in size, its surface area-to-volume ratio decreases. If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. Review Questions 

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[link] Glossary nucleoid central part of a prokaryotic cell in which the chromosome is found prokaryote unicellular organism that lacks a nucleus or any other membrane-bound organelleEukaryotic Cells Eukaryotic Cells 

In this section, you will explore the following questions: How does the structure of the eukaryotic cell resemble as well as differ from the structure of the prokaryotic cell? What are structural differences between animal and plant cells? What are the functions of the major cell structures? Connection for AP Courses 

Eukaryotic cells possess many features that prokaryotic cells lack, including a nucleus with a double membrane that encloses DNA. In addition, eukaryotic cells tend to be larger and have a variety of membrane-bound organelles that perform specific, compartmentalized functions. Evidence supports the hypothesis that eukaryotic cells likely evolved from prokaryotic ancestors; for example, mitochondria and chloroplasts feature characteristics of independently-living prokaryotes. Eukaryotic cells come in all shapes, sizes, and types (e.g. animal cells, plant cells, and different types of cells in the body). (Hint: This a rare instance where you should create a list of organelles and their respective functions because later you will focus on how various organelles work together, similar to how your body s organs work together to keep you healthy.) Like prokaryotes, all eukaryotic cells have a plasma membrane, cytoplasm, ribosomes, and DNA. Many organelles are bound by membranes composed of phospholipid bilayers embedded with proteins to compartmentalize functions such as the storage of hydrolytic enzymes and the synthesis of proteins. The nucleus houses DNA, and the nucleolus within the nucleus is the site of ribosome assembly. Functional ribosomes are found either free in the cytoplasm or attached to the rough endoplasmic reticulum where they perform protein synthesis. The Golgi apparatus receives, modifies, and packages small molecules like lipids and proteins for distribution. Mitochondria and chloroplasts participate in free energy capture and transfer through the processes of cellular respiration and photosynthesis, respectively. Peroxisomes oxidize fatty acids and amino acids, and they are equipped to break down hydrogen peroxide formed from these reactions without letting it into the cytoplasm where it can cause damage. Vesicles and vacuoles store substances, and in plant cells, the central vacuole stores pigments, salts, minerals, nutrients, proteins, and degradation enzymes and helps maintain rigidity. In contrast, animal cells have centrosomes and lysosomes but lack cell walls. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 1, Big Idea 2, and Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domains to generalize or extrapolate in and/or across enduring understandings Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.13 The student is able to explain how internal membranes and organelles contribute to cell functions. Essential Knowledge 2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 2.14 The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.2 The structure and function of subcellular components, and their interactions, provide essential cellular processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 4.5 The student is able to construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions. 

Divide students into groups of 4 5 and assign each group either a bacterial, plant or animal cell and ask each group to draw the cell and its components on a large sheet of paper. Groups will use a separate sheet of paper to list all the structures and their respective functions. Ask each group to present its cell model to the rest of the class. Post the drawings on the wall of the class. Update the models with corrections as needed. 

Many students reason that plant cells do not need mitochondria because the chloroplasts within plant cells convert light energy into chemical energy, and, therefore, mitochondria are not needed. Stress that all eukaryotic cells (with only few exceptions) contain mitochondria. 

Emphasize that the diagrams in the textbook represent generalizations. Cells vary enormously in shapes and functions. Some internal structures may be predominant according to the type of cell. For instance, liver cells that detoxify chemicals and synthesize lipids have an extensive smooth endoplasmic reticulum. 

Have you ever heard the phrase form follows function? It s a philosophy practiced in many industries. In architecture, this means that buildings should be constructed to support the activities that will be carried out inside them. For example, a skyscraper should be built with several elevator banks; a hospital should be built so that its emergency room is easily accessible. 

Our natural world also utilizes the principle of form following function, especially in cell biology, and this will become clear as we explore eukaryotic cells ( [link] ). Unlike prokaryotic cells, eukaryotic cells have: 1) a membrane-bound nucleus; 2) numerous membrane-bound organelles such as the endoplasmic reticulum, Golgi apparatus, chloroplasts, mitochondria, and others; and 3) several, rod-shaped chromosomes. Because a eukaryotic cell s nucleus is surrounded by a membrane, it is often said to have a true nucleus. The word organelle means little organ, and, as already mentioned, organelles have specialized cellular functions, just as the organs of your body have specialized functions. 

At this point, it should be clear to you that eukaryotic cells have a more complex structure than prokaryotic cells. Organelles allow different functions to be compartmentalized in different areas of the cell. Before turning to organelles, let s first examine two important components of the cell: the plasma membrane and the cytoplasm. 

These figures show the major organelles and other cell components of (a) a typical animal cell and (b) a typical eukaryotic plant cell. The plant cell has a cell wall, chloroplasts, plastids, and a central vacuole structures not found in animal cells. Plant cells do not have lysosomes or centrosomes. 

[link] The Plasma Membrane 

Like prokaryotes, eukaryotic cells have a plasma membrane ( [link] ), a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment. A phospholipid is a lipid molecule with two fatty acid chains and a phosphate-containing group. The plasma membrane controls the passage of organic molecules, ions, water, and oxygen into and out of the cell. Wastes (such as carbon dioxide and ammonia) also leave the cell by passing through the plasma membrane. The eukaryotic plasma membrane is a phospholipid bilayer with proteins and cholesterol embedded in it. 

The plasma membranes of cells that specialize in absorption are folded into fingerlike projections called microvilli (singular = microvillus); ( [link] ). Such cells are typically found lining the small intestine, the organ that absorbs nutrients from digested food. This is an excellent example of form following function. People with celiac disease have an immune response to gluten, which is a protein found in wheat, barley, and rye. The immune response damages microvilli, and thus, afflicted individuals cannot absorb nutrients. This leads to malnutrition, cramping, and diarrhea. Patients suffering from celiac disease must follow a gluten-free diet. Microvilli, shown here as they appear on cells lining the small intestine, increase the surface area available for absorption. These microvilli are only found on the area of the plasma membrane that faces the cavity from which substances will be absorbed. (credit "micrograph": modification of work by Louisa Howard) The Cytoplasm 

The cytoplasm is the entire region of a cell between the plasma membrane and the nuclear envelope (a structure to be discussed shortly). It is made up of organelles suspended in the gel-like cytosol , the cytoskeleton, and various chemicals ( [link] ). Even though the cytoplasm consists of 70 to 80 percent water, it has a semi-solid consistency, which comes from the proteins within it. However, proteins are not the only organic molecules found in the cytoplasm. Glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and derivatives of glycerol are found there, too. Ions of sodium, potassium, calcium, and many other elements are also dissolved in the cytoplasm. Many metabolic reactions, including protein synthesis, take place in the cytoplasm. The Nucleus 

Typically, the nucleus is the most prominent organelle in a cell ( [link] ). The nucleus (plural = nuclei) houses the cell s DNA and directs the synthesis of ribosomes and proteins. Let s look at it in more detail ( [link] ). The nucleus stores chromatin (DNA plus proteins) in a gel-like substance called the nucleoplasm. The nucleolus is a condensed region of chromatin where ribosome synthesis occurs. The boundary of the nucleus is called the nuclear envelope. It consists of two phospholipid bilayers: an outer membrane and an inner membrane. The nuclear membrane is continuous with the endoplasmic reticulum. Nuclear pores allow substances to enter and exit the nucleus. The Nuclear Envelope 

The nuclear envelope is a double-membrane structure that constitutes the outermost portion of the nucleus ( [link] ). Both the inner and outer membranes of the nuclear envelope are phospholipid bilayers. 

The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm. The nucleoplasm is the semi-solid fluid inside the nucleus, where we find the chromatin and the nucleolus. Chromatin and Chromosomes 

To understand chromatin, it is helpful to first consider chromosomes. Chromosomes are structures within the nucleus that are made up of DNA, the hereditary material. You may remember that in prokaryotes, DNA is organized into a single circular chromosome. In eukaryotes, chromosomes are linear structures. Every eukaryotic species has a specific number of chromosomes in the nuclei of its body s cells. For example, in humans, the chromosome number is 46, while in fruit flies, it is eight. Chromosomes are only visible and distinguishable from one another when the cell is getting ready to divide. When the cell is in the growth and maintenance phases of its life cycle, proteins are attached to chromosomes, and they resemble an unwound, jumbled bunch of threads. These unwound protein-chromosome complexes are called chromatin ( [link] ); chromatin describes the material that makes up the chromosomes both when condensed and decondensed. (a) This image shows various levels of the organization of chromatin (DNA and protein). (b) This image shows paired chromosomes. (credit b: modification of work by NIH; scale-bar data from Matt Russell) The Nucleolus 

We already know that the nucleus directs the synthesis of ribosomes, but how does it do this? Some chromosomes have sections of DNA that encode ribosomal RNA. A darkly staining area within the nucleus called the nucleolus (plural = nucleoli) aggregates the ribosomal RNA with associated proteins to assemble the ribosomal subunits that are then transported out through the pores in the nuclear envelope to the cytoplasm. Ribosomes 

Ribosomes are the cellular structures responsible for protein synthesis. When viewed through an electron microscope, ribosomes appear either as clusters (polyribosomes) or single, tiny dots that float freely in the cytoplasm. They may be attached to the cytoplasmic side of the plasma membrane or the cytoplasmic side of the endoplasmic reticulum and the outer membrane of the nuclear envelope ( [link] ). Electron microscopy has shown us that ribosomes, which are large complexes of protein and RNA, consist of two subunits, aptly called large and small ( [link] ). Ribosomes receive their orders for protein synthesis from the nucleus where the DNA is transcribed into messenger RNA (mRNA). The mRNA travels to the ribosomes, which translate the code provided by the sequence of the nitrogenous bases in the mRNA into a specific order of amino acids in a protein. Amino acids are the building blocks of proteins. Ribosomes are made up of a large subunit (top) and a small subunit (bottom). During protein synthesis, ribosomes assemble amino acids into proteins. 

Because proteins synthesis is an essential function of all cells (including enzymes, hormones, antibodies, pigments, structural components, and surface receptors), ribosomes are found in practically every cell. Ribosomes are particularly abundant in cells that synthesize large amounts of protein. For example, the pancreas is responsible for creating several digestive enzymes and the cells that produce these enzymes contain many ribosomes. Thus, we see another example of form following function. Mitochondria 

Mitochondria (singular = mitochondrion) are often called the powerhouses or energy factories of a cell because they are responsible for making adenosine triphosphate (ATP), the cell s main energy-carrying molecule. ATP represents the short-term stored energy of the cell. Cellular respiration is the process of making ATP using the chemical energy found in glucose and other nutrients. In mitochondria, this process uses oxygen and produces carbon dioxide as a waste product. In fact, the carbon dioxide that you exhale with every breath comes from the cellular reactions that produce carbon dioxide as a byproduct. 

In keeping with our theme of form following function, it is important to point out that muscle cells have a very high concentration of mitochondria that produce ATP. Your muscle cells need a lot of energy to keep your body moving. When your cells don t get enough oxygen, they do not make a lot of ATP. Instead, the small amount of ATP they make in the absence of oxygen is accompanied by the production of lactic acid. 

Mitochondria are oval-shaped, double membrane organelles ( [link] ) that have their own ribosomes and DNA. Each membrane is a phospholipid bilayer embedded with proteins. The inner layer has folds called cristae. The area surrounded by the folds is called the mitochondrial matrix. The cristae and the matrix have different roles in cellular respiration. This electron micrograph shows a mitochondrion as viewed with a transmission electron microscope. This organelle has an outer membrane and an inner membrane. The inner membrane contains folds, called cristae, which increase its surface area. The space between the two membranes is called the intermembrane space, and the space inside the inner membrane is called the mitochondrial matrix. ATP synthesis takes place on the inner membrane. (credit: modification of work by Matthew Britton; scale-bar data from Matt Russell) Peroxisomes 

Peroxisomes are small, round organelles enclosed by single membranes. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many poisons that may enter the body. (Many of these oxidation reactions release hydrogen peroxide, H 2 O 2 , which would be damaging to cells; however, when these reactions are confined to peroxisomes, enzymes safely break down the H 2 O 2 into oxygen and water.) For example, alcohol is detoxified by peroxisomes in liver cells. Glyoxysomes, which are specialized peroxisomes in plants, are responsible for converting stored fats into sugars. Vesicles and Vacuoles 

Vesicles and vacuoles are membrane-bound sacs that function in storage and transport. Other than the fact that vacuoles are somewhat larger than vesicles, there is a very subtle distinction between them: The membranes of vesicles can fuse with either the plasma membrane or other membrane systems within the cell. Additionally, some agents such as enzymes within plant vacuoles break down macromolecules. The membrane of a vacuole does not fuse with the membranes of other cellular components. Animal Cells versus Plant Cells 

At this point, you know that each eukaryotic cell has a plasma membrane, cytoplasm, a nucleus, ribosomes, mitochondria, peroxisomes, and in some, vacuoles, but there are some striking differences between animal and plant cells. While both animal and plant cells have microtubule organizing centers (MTOCs), animal cells also have centrioles associated with the MTOC: a complex called the centrosome. Animal cells each have a centrosome and lysosomes, whereas plant cells do not. Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole, whereas animal cells do not. The Centrosome 

The centrosome is a microtubule-organizing center found near the nuclei of animal cells. It contains a pair of centrioles, two structures that lie perpendicular to each other ( [link] ). Each centriole is a cylinder of nine triplets of microtubules. The centrosome consists of two centrioles that lie at right angles to each other. Each centriole is a cylinder made up of nine triplets of microtubules. Nontubulin proteins (indicated by the green lines) hold the microtubule triplets together. 

The centrosome (the organelle where all microtubules originate) replicates itself before a cell divides, and the centrioles appear to have some role in pulling the duplicated chromosomes to opposite ends of the dividing cell. However, the exact function of the centrioles in cell division isn t clear, because cells that have had the centrosome removed can still divide, and plant cells, which lack centrosomes, are capable of cell division. Lysosomes 

Animal cells have another set of organelles not found in plant cells: lysosomes. The lysosomes are the cell s garbage disposal. In plant cells, the digestive processes take place in vacuoles. Enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles. These enzymes are active at a much lower pH than that of the cytoplasm. Therefore, the pH within lysosomes is more acidic than the pH of the cytoplasm. Many reactions that take place in the cytoplasm could not occur at a low pH, so again, the advantage of compartmentalizing the eukaryotic cell into organelles is apparent. The Cell Wall 

If you examine [link] b , the diagram of a plant cell, you will see a structure external to the plasma membrane called the cell wall. The cell wall is a rigid covering that protects the cell, provides structural support, and gives shape to the cell. Fungal and protistan cells also have cell walls. While the chief component of prokaryotic cell walls is peptidoglycan, the major organic molecule in the plant cell wall is cellulose ( [link] ), a polysaccharide made up of glucose units. Have you ever noticed that when you bite into a raw vegetable, like celery, it crunches? That s because you are tearing the rigid cell walls of the celery cells with your teeth. Cellulose is a long chain of -glucose molecules connected by a 1-4 linkage. The dashed lines at each end of the figure indicate a series of many more glucose units. The size of the page makes it impossible to portray an entire cellulose molecule. Chloroplasts 

Like the mitochondria, chloroplasts have their own DNA and ribosomes, but chloroplasts have an entirely different function. Chloroplasts are plant cell organelles that carry out photosynthesis. Photosynthesis is the series of reactions that use carbon dioxide, water, and light energy to make glucose and oxygen. This is a major difference between plants and animals; plants (autotrophs) are able to make their own food, like sugars, while animals (heterotrophs) must ingest their food. 

Like mitochondria, chloroplasts have outer and inner membranes, but within the space enclosed by a chloroplast s inner membrane is a set of interconnected and stacked fluid-filled membrane sacs called thylakoids ( [link] ). Each stack of thylakoids is called a granum (plural = grana). The fluid enclosed by the inner membrane that surrounds the grana is called the stroma. The chloroplast has an outer membrane, an inner membrane, and membrane structures called thylakoids that are stacked into grana. The space inside the thylakoid membranes is called the thylakoid space. The light harvesting reactions take place in the thylakoid membranes, and the synthesis of sugar takes place in the fluid inside the inner membrane, which is called the stroma. Chloroplasts also have their own genome, which is contained on a single circular chromosome. 

The chloroplasts contain a green pigment called chlorophyll , which captures the light energy that drives the reactions of photosynthesis. Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle. 

Endosymbiosis We have mentioned that both mitochondria and chloroplasts contain DNA and ribosomes. Have you wondered why? Strong evidence points to endosymbiosis as the explanation. 

Symbiosis is a relationship in which organisms from two separate species depend on each other for their survival. Endosymbiosis (endo- = within ) is a mutually beneficial relationship in which one organism lives inside the other. Endosymbiotic relationships abound in nature. We have already mentioned that microbes that produce vitamin K live inside the human gut. This relationship is beneficial for us because we are unable to synthesize vitamin K. It is also beneficial for the microbes because they are protected from other organisms and from drying out, and they receive abundant food from the environment of the large intestine. 

Scientists have long noticed that bacteria, mitochondria, and chloroplasts are similar in size. We also know that bacteria have DNA and ribosomes, just as mitochondria and chloroplasts do. Scientists believe that host cells and bacteria formed an endosymbiotic relationship when the host cells ingested both aerobic and autotrophic bacteria (cyanobacteria) but did not destroy them. Through many millions of years of evolution, these ingested bacteria became more specialized in their functions, with the aerobic bacteria becoming mitochondria and the autotrophic bacteria becoming chloroplasts. 

[link] The Central Vacuole 

Previously, we mentioned vacuoles as essential components of plant cells. If you look at [link] b , you will see that plant cells each have a large central vacuole that occupies most of the area of the cell. The central vacuole plays a key role in regulating the cell s concentration of water in changing environmental conditions. Have you ever noticed that if you forget to water a plant for a few days, it wilts? That s because as the water concentration in the soil becomes lower than the water concentration in the plant, water moves out of the central vacuoles and cytoplasm. As the central vacuole shrinks, it leaves the cell wall unsupported. This loss of support to the cell walls of plant cells results in the wilted appearance of the plant. 

The central vacuole also supports the expansion of the cell. When the central vacuole holds more water, the cell gets larger without having to invest a lot of energy in synthesizing new cytoplasm. Activity Construct a concept map or Venn diagram to describe the relationships that exist among the three domains of life (Archaea, Bacteria, and Eukarya) based on cellular features. Share your diagram with other students in the class for review and revision. Mystery Cell ID. Using a microscope, identify several types of cells, e.g., prokaryote/eukaryote, plant/animal, based on general features and justify your identification. Ten-Minute Debate. Working in small teams, create a visual representation to support the claim that eukaryotes evolved from symbiotic relationships among groups of prokaryotes. Think About It If the nucleolus were not able to carry out its function, what other cellular organelles would be affected? Would a human liver cell that lacked endoplasmic reticulum be able to metabolize toxins? Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. What part(s) of the bacterial cell do antibiotics target and provide reasoning for your answer. 

The first activity is an application of Learning Objectives 1.15 and Science Practice 7.2 because students are describing features common to all cells that suggest common ancestry. 

The second activity is an application of Learning Objectives 2.14 and Science Practice 1.4 because the students are describing features that typify various cell types based on models presented in the textbook. 

The third activity is an application of Learning Objectives 1.16 and Science Practice 6.1 because the students are describing evidence that supports the claim that eukaryotes evolved from prokaryotes. and following with a question that could be investigated to provide additional support for this claim. 

The first question is an application of Learning Objectives 4.4 and Science Practice 6.4 because the students are asked to make predictions about the functions of cellular organelles. 

The second question is an application of Learning Objectives 2.14 and Science Practice 1.4 because the students are describing differences between prokaryotic and eukaryotic cells based on models of the cell(s). 

Although ribosomes are well-conserved, there are enough differences between prokaryotic and eukaryotic ribosomes that many antibiotics target the prokaryotic ribosomes without affecting the eukaryotic ribosomes. Mention that ribosomes in mitochondria and chloroplasts are very similar to the prokaryotic ribosomes. This is a strong point in support of the endosymbiotic theory. 

Choose a light or electron microscope or set of micrographs to extend the activity. This enables the students to take size into consideration. Use table 4.1 as a guide. Point out that eventually all organelles would be affected by a loss of ribosome function, as protein synthesis shuts down. A human liver cell that lacked the smooth endoplasmic reticulum (SER) would not breakdown toxins, as that is one of the functions of the SER. This is an opportunity to differentiate between RER and SER. All antibiotics inhibit growth either by killing (bactericidal) or by interfering with growth (bacteriostatic). Penicillin and derivatives inhibit the synthesis of peptidoglycans in the cell wall. Without a cell wall, bacterial cells lyse. Section Summary 

Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. The plasma membrane is a phospholipid bilayer embedded with proteins. The nucleus s nucleolus is the site of ribosome assembly. Ribosomes are either found in the cytoplasm or attached to the cytoplasmic side of the plasma membrane or endoplasmic reticulum. They perform protein synthesis. Mitochondria participate in cellular respiration; they are responsible for the majority of ATP produced in the cell. Peroxisomes hydrolyze fatty acids, amino acids, and some toxins. Vesicles and vacuoles are storage and transport compartments. In plant cells, vacuoles also help break down macromolecules. 

Animal cells also have a centrosome and lysosomes. The centrosome has two bodies perpendicular to each other, the centrioles, and has an unknown purpose in cell division. Lysosomes are the digestive organelles of animal cells. 

Plant cells and plant-like cells each have a cell wall, chloroplasts, and a central vacuole. The plant cell wall, whose primary component is cellulose, protects the cell, provides structural support, and gives shape to the cell. Photosynthesis takes place in chloroplasts. The central vacuole can expand without having to produce more cytoplasm. Review Questions 

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[link] Glossary cell wall rigid cell covering made of cellulose that protects the cell, provides structural support, and gives shape to the cell central vacuole large plant cell organelle that regulates the cell s storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation centrosome region in animal cells made of two centrioles chlorophyll green pigment that captures the light energy that drives the light reactions of photosynthesis chloroplast plant cell organelle that carries out photosynthesis chromatin protein-DNA complex that serves as the building material of chromosomes chromosome structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material cytoplasm entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals cytosol gel-like material of the cytoplasm in which cell structures are suspended eukaryotic cell cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs lysosome organelle in an animal cell that functions as the cell s digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles mitochondria (singular = mitochondrion) cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell s main energy-carrying molecule nuclear envelope double-membrane structure that constitutes the outermost portion of the nucleus nucleolus darkly staining body within the nucleus that is responsible for assembling the subunits of the ribosomes nucleoplasm semi-solid fluid inside the nucleus that contains the chromatin and nucleolus nucleus cell organelle that houses the cell s DNA and directs the synthesis of ribosomes and proteins organelle compartment or sac within a cell peroxisome small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons plasma membrane phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the internal content of the cell from its surrounding environment ribosome cellular structure that carries out protein synthesis vacuole membrane-bound sac, somewhat larger than a vesicle, which functions in cellular storage and transport vesicle small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatusThe Endomembrane System and Proteins The Endomembrane System and Proteins 

In this section, you will explore the following questions: What is the relationship between the structure and function of the components of the endomembrane system, especially with regard to the synthesis of proteins? Connection for AP Courses 

In addition to the presence of nuclei, eukaryotic cells are distinguished by an endomembrane system that includes the plasma membrane, nuclear envelope, lysosomes, vesicles, endoplasmic reticulum, and Golgi apparatus. These subcellular components work together to modify, tag, package, and transport proteins and lipids. The rough endoplasmic reticulum (RER) with its attached ribosomes is the site of protein synthesis and modification. The smooth endoplasmic reticulum (SER) synthesizes carbohydrates, lipids including phospholipids and cholesterol, and steroid hormones; engages in the detoxification of medications and poisons; and stores calcium ions. Lysosomes digest macromolecules, recycle worn-out organelles, and destroy pathogens. Just like your body uses different organs that work together, cells use these organelles interact to perform specific functions. For example, proteins that are synthesized in the RER then travel to the Golgi apparatus for modification and packaging for either storage or transport. If these proteins are hydrolytic enzymes, they can be stored in lysosomes. Mitochondria produce the energy needed for these processes. This functional flow through several organelles, a process which is dependent on energy produced by yet another organelle, serves as a hallmark illustration of the cell s complex, interconnected dependence on its organelles. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 and Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.13 The student is able to explain how internal membranes and organelles contribute to cell functions. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.2 The structure and function of subcellular components, and their interactions, provide essential cellular processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 4.5 The student is able to construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions. 

Students will need help in visualizing the endomembrane system. For example, explain how the interior membrane surface of a vesicle will face the outside of the cell, once the vesicle fuses with the plasma membrane. Use rubber bands to simulate vesicles and mark the inside with a sharpie or a pen. Follow the ink marks as the vesicle rubber band fuses with the cell membrane (cut the rubber band to facilitate the fusion being modeled.) 

Students may think that all ribosomes are attached to the rough endoplasmic reticulum. Stress that there are free ribosomes as well. They are found in the cytosol where they are involved in the synthesis of cytosolic proteins, which remain within the cytosol. Free and bound ribosomes are identical in structure . Individual ribosomes cycle between free and membrane-bound positions as needed. 

Mitochondria and chloroplasts also contain ribosomes which resemble those of prokaryotes. This observation is one of the arguments in favor of the endosymbiotic theory. 

Smooth endoplasmic reticulum is not as important as the rough endoplasmic reticulum. No, both endomembrane networks play important roles in the life of a cell. The Endoplasmic Reticulum 

The endomembrane system (endo = within ) is a group of membranes and organelles ( [link] ) in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It includes the nuclear envelope, lysosomes, and vesicles, which we ve already mentioned, and the endoplasmic reticulum and Golgi apparatus, which we will cover shortly. Although not technically within the cell, the plasma membrane is included in the endomembrane system because, as you will see, it interacts with the other endomembranous organelles. The endomembrane system does not include the membranes of either mitochondria or chloroplasts. 

"Membrane and secretory proteins are synthesized in the rough endoplasmic reticulum (RER). The RER also sometimes modifies proteins. In this illustration, a (green) integral membrane protein in the ER is modified by attachment of a (purple) carbohydrate. Vesicles with the integral protein bud from the ER and fuse with the cis face of the Golgi apparatus. As the protein passes along the Golgi s cisternae, it is further modified by the addition of more carbohydrates. After its synthesis is complete, it exits as integral membrane protein of the vesicle that bud from the Golgi s trans face and when the vesicle fuses with the cell membrane the protein becomes integral portion of that cell membrane. (credit: modification of work by Magnus Manske) 

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The endoplasmic reticulum (ER) ( [link] ) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids. However, these two functions are performed in separate areas of the ER: the rough ER and the smooth ER, respectively. 

The hollow portion of the ER tubules is called the lumen or cisternal space. The membrane of the ER, which is a phospholipid bilayer embedded with proteins, is continuous with the nuclear envelope. Rough ER 

The rough endoplasmic reticulum (RER) is so named because the ribosomes attached to its cytoplasmic surface give it a studded appearance when viewed through an electron microscope ( [link] ). This transmission electron micrograph shows the rough endoplasmic reticulum and other organelles in a pancreatic cell. (credit: modification of work by Louisa Howard) 

Ribosomes transfer their newly synthesized proteins into the lumen of the RER where they undergo structural modifications, such as folding or the acquisition of side chains. These modified proteins will be incorporated into cellular membranes the membrane of the ER or those of other organelles or secreted from the cell (such as protein hormones, enzymes). The RER also makes phospholipids for cellular membranes. 

If the phospholipids or modified proteins are not destined to stay in the RER, they will reach their destinations via transport vesicles that bud from the RER s membrane ( [link] ). 

Since the RER is engaged in modifying proteins (such as enzymes, for example) that will be secreted from the cell, you would be correct in assuming that the RER is abundant in cells that secrete proteins. This is the case with cells of the liver, for example. Smooth ER 

The smooth endoplasmic reticulum (SER) is continuous with the RER but has few or no ribosomes on its cytoplasmic surface ( [link] ). Functions of the SER include synthesis of carbohydrates, lipids, and steroid hormones; detoxification of medications and poisons; and storage of calcium ions. 

In muscle cells, a specialized SER called the sarcoplasmic reticulum is responsible for storage of the calcium ions that are needed to trigger the coordinated contractions of the muscle cells. 

You can watch an excellent animation of the endomembrane system here . At the end of the animation, there is a short self-assessment. 

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Cardiologist Heart disease is the leading cause of death in the United States. This is primarily due to our sedentary lifestyle and our high trans-fat diets. 

Heart failure is just one of many disabling heart conditions. Heart failure does not mean that the heart has stopped working. Rather, it means that the heart can t pump with sufficient force to transport oxygenated blood to all the vital organs. Left untreated, heart failure can lead to kidney failure and failure of other organs. 

The wall of the heart is composed of cardiac muscle tissue. Heart failure occurs when the endoplasmic reticula of cardiac muscle cells do not function properly. As a result, an insufficient number of calcium ions are available to trigger a sufficient contractile force. 

Cardiologists (cardi- = heart ; -ologist = one who studies ) are doctors who specialize in treating heart diseases, including heart failure. Cardiologists can make a diagnosis of heart failure via physical examination, results from an electrocardiogram (ECG, a test that measures the electrical activity of the heart), a chest X-ray to see whether the heart is enlarged, and other tests. If heart failure is diagnosed, the cardiologist will typically prescribe appropriate medications and recommend a reduction in table salt intake and a supervised exercise program. The Golgi Apparatus 

We have already mentioned that vesicles can bud from the ER and transport their contents elsewhere, but where do the vesicles go? Before reaching their final destination, the lipids or proteins within the transport vesicles still need to be sorted, packaged, and tagged so that they wind up in the right place. Sorting, tagging, packaging, and distribution of lipids and proteins takes place in the Golgi apparatus (also called the Golgi body), a series of flattened membranes ( [link] ). The Golgi apparatus in this white blood cell is visible as a stack of semicircular, flattened rings in the lower portion of the image. Several vesicles can be seen near the Golgi apparatus. (credit: modification of work by Louisa Howard) 

The receiving side of the Golgi apparatus is called the cis face. The opposite side is called the trans face. The transport vesicles that formed from the ER travel to the cis face, fuse with it, and empty their contents into the lumen of the Golgi apparatus. As the proteins and lipids travel through the Golgi, they undergo further modifications that allow them to be sorted. The most frequent modification is the addition of short chains of sugar molecules. These newly modified proteins and lipids are then tagged with phosphate groups or other small molecules so that they can be routed to their proper destinations. 

Finally, the modified and tagged proteins are packaged into secretory vesicles that bud from the trans face of the Golgi. While some of these vesicles deposit their contents into other parts of the cell where they will be used, other secretory vesicles fuse with the plasma membrane and release their contents outside the cell. 

In another example of form following function, cells that engage in a great deal of secretory activity (such as cells of the salivary glands that secrete digestive enzymes or cells of the immune system that secrete antibodies) have an abundance of Golgi. 

In plant cells, the Golgi apparatus has the additional role of synthesizing polysaccharides, some of which are incorporated into the cell wall and some of which are used in other parts of the cell. Career Connection 

Geneticist Many diseases arise from genetic mutations that prevent the synthesis of critical proteins. One such disease is Lowe disease (also called oculocerebrorenal syndrome, because it affects the eyes, brain, and kidneys). In Lowe disease, there is a deficiency in an enzyme localized to the Golgi apparatus. Children with Lowe disease are born with cataracts, typically develop kidney disease after the first year of life, and may have impaired mental abilities. 

Lowe disease is a genetic disease caused by a mutation on the X chromosome. The X chromosome is one of the two human sex chromosome, as these chromosomes determine a person's sex. Females possess two X chromosomes while males possess one X and one Y chromosome. In females, the genes on only one of the two X chromosomes are expressed. Therefore, females who carry the Lowe disease gene on one of their X chromosomes have a 50/50 chance of having the disease. However, males only have one X chromosome and the genes on this chromosome are always expressed. Therefore, males will always have Lowe disease if their X chromosome carries the Lowe disease gene. The location of the mutated gene, as well as the locations of many other mutations that cause genetic diseases, has now been identified. Through prenatal testing, a woman can find out if the fetus she is carrying may be afflicted with one of several genetic diseases. 

Geneticists analyze the results of prenatal genetic tests and may counsel pregnant women on available options. They may also conduct genetic research that leads to new drugs or foods, or perform DNA analyses that are used in forensic investigations. Lysosomes 

In addition to their role as the digestive component and organelle-recycling facility of animal cells, lysosomes are considered to be parts of the endomembrane system. Lysosomes also use their hydrolytic enzymes to destroy pathogens (disease-causing organisms) that might enter the cell. A good example of this occurs in a group of white blood cells called macrophages, which are part of your body s immune system. In a process known as phagocytosis or endocytosis, a section of the plasma membrane of the macrophage invaginates (folds in) and engulfs a pathogen. The invaginated section, with the pathogen inside, then pinches itself off from the plasma membrane and becomes a vesicle. The vesicle fuses with a lysosome. The lysosome s hydrolytic enzymes then destroy the pathogen ( [link] ). A macrophage has engulfed (phagocytized) a potentially pathogenic bacterium and then fuses with a lysosomes within the cell to destroy the pathogen. Other organelles are present in the cell but for simplicity are not shown. Activity 

Homemade Cell Project. Using inexpensive and common household items, create a model of a specific eukaryotic cell (e.g., neuron, white blood cell, plant root cell, or Paramecium ) that demonstrates how at least three organelles work together to perform a specific function. Think About It 

A certain cell type functions primarily to synthesize proteins for export. What is the most likely route the newly made protein takes through the cell? Justify your prediction. 

The activity is an application of Learning Objective 2.13 and Science Practice 6.2 and Learning Objective 4.6 and Science Practice 1.4 because students are asked to create a model that describes various organelles in a specific cell type and then describe how organelles work together to perform a characteristic function of the cell. 

The Think About It question is an application of Learning Objective 4.4 and Science Practice 6.4 because students are making a prediction about the interactions of subcellular organelles in performing a specific function. 

The path is ribosomes rough ER vesicle Golgi apparatus vesicle and release. Use information in the text. Section Summary 

The endomembrane system includes the nuclear envelope, lysosomes, vesicles, the ER, and Golgi apparatus, as well as the plasma membrane. These cellular components work together to modify, package, tag, and transport proteins and lipids that form the membranes. 

The RER modifies proteins and synthesizes phospholipids used in cell membranes. The SER synthesizes carbohydrates, lipids, and steroid hormones; engages in the detoxification of medications and poisons; and stores calcium ions. Sorting, tagging, packaging, and distribution of lipids and proteins take place in the Golgi apparatus. Lysosomes are created by the budding of the membranes of the RER and Golgi. Lysosomes digest macromolecules, recycle worn-out organelles, and destroy pathogens. Review Questions 

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[link] Glossary endomembrane system group of organelles and membranes in eukaryotic cells that work together modifying, packaging, and transporting lipids and proteins endoplasmic reticulum (ER) series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids Golgi apparatus eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution rough endoplasmic reticulum (RER) region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis smooth endoplasmic reticulum (SER) region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies certain chemicals (like pesticides, preservatives, medications, and environmental pollutants), and stores calcium ionsThe Cytoskeleton The Cytoskeleton 

In this section, you will explore the following questions: How do the various components of the cytoskeleton perform their functions? Connection for AP Courses 

All cells, from simple bacteria to complex eukaryotes, possess a cytoskeleton composed of different types of protein elements, including microfilaments, intermediate filaments, and microtubules. The cytoskeleton serves a variety of purposes: provides rigidity and shape to the cell, facilitates cellular movement, anchors the nucleus and other organelles in place, moves vesicles through the cell, and pulls replicated chromosomes to the poles of a dividing cell. These protein elements are also integral to the movement of centrioles, flagella, and cilia. 

The information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 1 of the AP Biology Curriculum Framework, as shown in the table below. 

The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Describe the cytoskeleton both as a skeleton because it provides the cell with shape and as muscles because it allows cells to move. The subunits of the cytoskeleton assemble and disassemble constantly, which is hard to imagine. Stress the concept of dynamic equilibrium. A vivid animation may illustrate the point better. Another way to demonstrate this is to have a few students stand in a line and then have a pool of students stand nearby. Then, on by one, ask students from the pool to exchange places with a student standing in the line. The line itself can grow and shrink by adding or taking away students in the line, respectively. 

Both prokaryotic and eukaryotic cells possess cytoskeletons involved in cell division and shape maintenance. Although the molecular structures of cytoskeleton proteins are similar between two types of cells, the actual amino acid sequences of these proteins show very low levels of homology between the cytoskeleton proteins in prokaryotes and eukaryotes. 

The two systems are not closely related. 

Although the cytoskeleton of prokaryotes was discovered in the mid 90 s, the misconception that prokaryotes do not have a cytoskeleton is still widespread. Microfilaments 

If you were to remove all the organelles from a cell, would the plasma membrane and the cytoplasm be the only components left? No. Within the cytoplasm, there would still be ions and organic molecules, plus a network of protein fibers that help maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable cells within multicellular organisms to move. Collectively, this network of protein fibers is known as the cytoskeleton . There are three types of fibers within the cytoskeleton: microfilaments, intermediate filaments, and microtubules ( [link] ). Here, we will examine each. Microfilaments thicken the cortex around the inner edge of a cell; like rubber bands, they resist tension. Microtubules are found in the interior of the cell where they maintain cell shape by resisting compressive forces. Intermediate filaments are found throughout the cell and hold organelles in place. 

Of the three types of protein fibers in the cytoskeleton, microfilaments are the narrowest. They function in cellular movement, have a diameter of about 7 nm, and are made of two intertwined strands of a globular protein called actin ( [link] ). For this reason, microfilaments are also known as actin filaments. Microfilaments are made of two intertwined strands of actin. 

Actin is powered by ATP to assemble its filamentous form, which serves as a track for the movement of a motor protein called myosin. This enables actin to engage in cellular events requiring motion, such as cell division in animal cells and cytoplasmic streaming, which is the circular movement of the cell cytoplasm in plant cells. Actin and myosin are plentiful in muscle cells. When your actin and myosin filaments slide past each other, your muscles contract. 

Microfilaments also provide some rigidity and shape to the cell. They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move. White blood cells (your body s infection-fighting cells) make good use of this ability. They can move to the site of an infection and phagocytize the pathogen. 

To see an example of a white blood cell in action, click here and watch a short time-lapse video of the cell capturing two bacteria. It engulfs one and then moves on to the other. 

[link] Intermediate Filaments 

Intermediate filaments are made of several strands of fibrous proteins that are wound together ( [link] ). These elements of the cytoskeleton get their name from the fact that their diameter, 8 to 10 nm, is between those of microfilaments and microtubules. Intermediate filaments consist of several intertwined strands of fibrous proteins. 

Intermediate filaments have no role in cell movement. Their function is purely structural. They bear tension, thus maintaining the shape of the cell, and anchor the nucleus and other organelles in place. [link] shows how intermediate filaments create a supportive scaffolding inside the cell. 

The intermediate filaments are the most diverse group of cytoskeletal elements. Several types of fibrous proteins are found in the intermediate filaments. You are probably most familiar with keratin, the fibrous protein that strengthens your hair, nails, and the epidermis of the skin. Microtubules 

As their name implies, microtubules are small hollow tubes. The walls of the microtubule are made of polymerized dimers of -tubulin and -tubulin, two globular proteins ( [link] ). With a diameter of about 25 nm, microtubules are the widest components of the cytoskeleton. They help the cell resist compression, provide a track along which vesicles move through the cell, and pull replicated chromosomes to opposite ends of a dividing cell. Like microfilaments, microtubules can dissolve and reform quickly. Microtubules are hollow. Their walls consist of 13 polymerized dimers of -tubulin and -tubulin (right image). The left image shows the molecular structure of the tube. 

Microtubules are also the structural elements of flagella, cilia, and centrioles (the latter are the two perpendicular bodies of the centrosome). In fact, in animal cells, the centrosome is the microtubule-organizing center. In eukaryotic cells, flagella and cilia are quite different structurally from their counterparts in prokaryotes, as discussed below. Flagella and Cilia 

To refresh your memory, flagella (singular = flagellum) are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell (for example, sperm, Euglena ). When present, the cell has just one flagellum or a few flagella. When cilia (singular = cilium) are present, however, many of them extend along the entire surface of the plasma membrane. They are short, hair-like structures that are used to move entire cells (such as paramecia) or substances along the outer surface of the cell (for example, the cilia of cells lining the Fallopian tubes that move the ovum toward the uterus, or cilia lining the cells of the respiratory tract that trap particulate matter and move it toward your nostrils.) 

Despite their differences in length and number, flagella and cilia share a common structural arrangement of microtubules called a 9 + 2 array. This is an appropriate name because a single flagellum or cilium is made of a ring of nine microtubule doublets, surrounding a single microtubule doublet in the center ( [link] ). This transmission electron micrograph of two flagella shows the 9 + 2 array of microtubules: nine microtubule doublets surround a single microtubule doublet. (credit: modification of work by Dartmouth Electron Microscope Facility, Dartmouth College; scale-bar data from Matt Russell) Think About It 

The ribosomes in bacterial cells and in human cells are made up of proteins and ribosomal RNA, suggesting that both kinds of cells share a common ancestor cell type. What are examples of other features of cells that provide evidence for common ancestry? 

This question is an application of Learning Objectives 1.15 and Science Practice 7.2 because shared conserved core biological processes and features support the concept of common ancestry for all organisms on Earth. 

In both prokaryotes and eukaryotes, DNA is the hereditary material and has the same structure. 

The cytosol is made of an aqueous gel. The membrane is a fluid bilayer in which proteins are embedded. Do not use the flagellum as an example. It is convergent evolution. 

You have now completed a broad survey of the components of prokaryotic and eukaryotic cells. For a summary of cellular components in prokaryotic and eukaryotic cells, see [link] . Components of Prokaryotic and Eukaryotic Cells Cell Component Function Present in Prokaryotes? Present in Animal Cells? Present in Plant Cells? Plasma membrane Separates cell from external environment; controls passage of organic molecules, ions, water, oxygen, and wastes into and out of cell Yes Yes Yes Cytoplasm Provides turgor pressure to plant cells as fluid inside the central vacuole; site of many metabolic reactions; medium in which organelles are found Yes Yes Yes Nucleolus Darkened area within the nucleus where ribosomal subunits are synthesized. No Yes Yes Nucleus Cell organelle that houses DNA and directs synthesis of ribosomes and proteins No Yes Yes Ribosomes Protein synthesis Yes Yes Yes Mitochondria ATP production/cellular respiration No Yes Yes Peroxisomes Oxidizes and thus breaks down fatty acids and amino acids, and detoxifies poisons No Yes Yes Vesicles and vacuoles Storage and transport; digestive function in plant cells No Yes Yes Centrosome Unspecified role in cell division in animal cells; source of microtubules in animal cells No Yes No Lysosomes Digestion of macromolecules; recycling of worn-out organelles No Yes No Cell wall Protection, structural support and maintenance of cell shape Yes, primarily peptidoglycan No Yes, primarily cellulose Chloroplasts Photosynthesis No No Yes Endoplasmic reticulum Modifies proteins and synthesizes lipids No Yes Yes Golgi apparatus Modifies, sorts, tags, packages, and distributes lipids and proteins No Yes Yes Cytoskeleton Maintains cell s shape, secures organelles in specific positions, allows cytoplasm and vesicles to move within cell, and enables unicellular organisms to move independently Yes Yes Yes Flagella Cellular locomotion Some Some No, except for some plant sperm cells. Cilia Cellular locomotion, movement of particles along extracellular surface of plasma membrane, and filtration Some Some No Section Summary 

The cytoskeleton has three different types of protein elements. From narrowest to widest, they are the microfilaments (actin filaments), intermediate filaments, and microtubules. Microfilaments are often associated with myosin. They provide rigidity and shape to the cell and facilitate cellular movements. Intermediate filaments bear tension and anchor the nucleus and other organelles in place. Microtubules help the cell resist compression, serve as tracks for motor proteins that move vesicles through the cell, and pull replicated chromosomes to opposite ends of a dividing cell. They are also the structural element of centrioles, flagella, and cilia. Review Questions 

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[link] Glossary cilium (plural = cilia) short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell cytoskeleton network of protein fibers that collectively maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently flagellum (plural = flagella) long, hair-like structure that extends from the plasma membrane and is used to move the cell intermediate filament cytoskeletal component, composed of several intertwined strands of fibrous protein, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures microfilament narrowest element of the cytoskeleton system; it provides rigidity and shape to the cell and enables cellular movements microtubule widest element of the cytoskeleton system; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and ciliaConnections between Cells and Cellular Activities Connections between Cells and Cellular Activities 

In this section, you will explore the following questions: What are the components of the extracellular matrix? What are the roles of tight junctions, gap junctions, and plasmodesmata in allowing cells to exchange materials with the environment and communicate with other cells? Connection for AP Courses 

With the exception of gap junctions between animal cells and plasmodesmata between plant cells that facilitate the exchange of substances, the information presented in Section 4.6| Connections between Cells and Cellular Activities is not required for AP . Concepts about cell communication and signaling processes that are required for AP , including the features of cells that make communication possible, are covered in Chapter 9. 

You already know that a group of similar cells working together is called a tissue. As you might expect that, if cells are to work together, they must communicate with one another, just as you need to communicate with others when you work on a group project. Let s take a look at how cells communicate with one another. 

Review the role of the extracellular matrix by comparing it to a scaffold outside of a building that buttresses and supports the main structure. It is an extension of the cell in animal tissues and provides essential functions in mechanical support, cell-cell communication, wound healing, and organism development. 

Cell junctions can be compared to the piecing together of fabric. Pieces of fabric are tightly joined by a seam. Tight junctions similarly glue cells together. Rivets and snaps bind fabric tightly in specific spots as desmosomes form close associations in specific areas. Gap junctions are almost like pins and allow trafficking between the cytoplasm of adjacent cells. 

Cells in tissues are usually inadequately visualized as puzzle pieces that interlock but that are functionally independent. Dispel this notion by stressing the importance of cell junctions. In multicellular organisms, cells interact with their neighboring cells. 

You already know that a group of similar cells working together is called a tissue. As you might expect, if cells are to work together, they must communicate with each other, just as you need to communicate with others if you work on a group project. Let s take a look at how cells communicate with each other. Extracellular Matrix of Animal Cells 

Most animal cells release materials into the extracellular space. The primary components of these materials are proteins, and the most abundant protein is collagen. Collagen fibers are interwoven with carbohydrate-containing protein molecules called proteoglycans. Collectively, these materials are called the extracellular matrix ( [link] ). Not only does the extracellular matrix hold the cells together to form a tissue, but it also allows the cells within the tissue to communicate with each other. How can this happen? The extracellular matrix consists of a network of proteins and carbohydrates. 

Cells have protein receptors on the extracellular surfaces of their plasma membranes. When a molecule within the matrix binds to the receptor, it changes the molecular structure of the receptor. The receptor, in turn, changes the conformation of the microfilaments positioned just inside the plasma membrane. These conformational changes induce chemical signals inside the cell that reach the nucleus and turn on or off the transcription of specific sections of DNA, which affects the production of associated proteins, thus changing the activities within the cell. 

Blood clotting provides an example of the role of the extracellular matrix in cell communication. When the cells lining a blood vessel are damaged, they display a protein receptor called tissue factor. When tissue factor binds with another factor in the extracellular matrix, it causes platelets to adhere to the wall of the damaged blood vessel, stimulates the adjacent smooth muscle cells in the blood vessel to contract (thus constricting the blood vessel), and initiates a series of steps that stimulate the platelets to produce clotting factors. Intercellular Junctions 

Cells can also communicate with each other via direct contact, referred to as intercellular junctions. There are some differences in the ways that plant and animal cells do this. Plasmodesmata are junctions between plant cells, whereas animal cell contacts include tight junctions, gap junctions, and desmosomes. Plasmodesmata 

In general, long stretches of the plasma membranes of neighboring plant cells cannot touch one another because they are separated by the cell wall that surrounds each cell ( see this figure b ). How then, can a plant transfer water and other soil nutrients from its roots, through its stems, and to its leaves? Such transport uses the vascular tissues (xylem and phloem) primarily. There also exist structural modifications called plasmodesmata (singular = plasmodesma), numerous channels that pass between cell walls of adjacent plant cells, connect their cytoplasm, and enable materials to be transported from cell to cell, and thus throughout the plant ( [link] ). A plasmodesma is a channel between the cell walls of two adjacent plant cells. Plasmodesmata allow materials to pass from the cytoplasm of one plant cell to the cytoplasm of an adjacent cell. Tight Junctions 

A tight junction is a watertight seal between two adjacent animal cells ( [link] ). The cells are held tightly against each other by proteins (predominantly two proteins called claudins and occludins). Tight junctions form watertight connections between adjacent animal cells. Proteins create tight junction adherence. (credit: modification of work by Mariana Ruiz Villareal) 

This tight adherence prevents materials from leaking between the cells; tight junctions are typically found in epithelial tissues that line internal organs and cavities, and comprise most of the skin. For example, the tight junctions of the epithelial cells lining your urinary bladder prevent urine from leaking out into the extracellular space. Desmosomes 

Also found only in animal cells are desmosomes , which act like spot welds between adjacent epithelial cells ( [link] ). Short proteins called cadherins in the plasma membrane connect to intermediate filaments to create desmosomes. The cadherins join two adjacent cells together and maintain the cells in a sheet-like formation in organs and tissues that stretch, like the skin, heart, and muscles. A desmosome forms a very strong spot weld between cells. It is created by the linkage of cadherins and intermediate filaments. (credit: modification of work by Mariana Ruiz Villareal) Gap Junctions 

Gap junctions in animal cells are like plasmodesmata in plant cells in that they are channels between adjacent cells that allow for the transport of ions, nutrients, and other substances that enable cells to communicate ( [link] ). Structurally, however, gap junctions and plasmodesmata differ. A gap junction is a protein-lined pore that allows water and small molecules to pass between adjacent animal cells. (credit: modification of work by Mariana Ruiz Villareal) 

Gap junctions develop when a set of six proteins (called connexins) in the plasma membrane arrange themselves in an elongated donut-like configuration called a connexon. When the pores ( doughnut holes ) of connexons in adjacent animal cells align, a channel between the two cells forms. Gap junctions are particularly important in cardiac muscle: The electrical signal for the muscle to contract is passed efficiently through gap junctions, allowing the heart muscle cells to contract in tandem. Link to Learning 

To conduct a virtual microscopy lab and review the parts of a cell, work through the steps of this interactive assignment . 

[link] Section Summary 

Animal cells communicate via their extracellular matrices and are connected to each other via tight junctions, desmosomes, and gap junctions. Plant cells are connected and communicate with each other via plasmodesmata. 

When protein receptors on the surface of the plasma membrane of an animal cell bind to a substance in the extracellular matrix, a chain of reactions begins that changes activities taking place within the cell. Plasmodesmata are channels between adjacent plant cells, while gap junctions are channels between adjacent animal cells. However, their structures are quite different. A tight junction is a watertight seal between two adjacent cells, while a desmosome acts like a spot weld. Review Questions 

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[link] Glossary desmosome linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments extracellular matrix material (primarily collagen, glycoproteins, and proteoglycans) secreted from animal cells that provides mechanical protection and anchoring for the cells in the tissue gap junction channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate plasmodesma (plural = plasmodesmata) channel that passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell tight junction firm seal between two adjacent animal cells created by protein adherenceIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Despite its seeming hustle and bustle, Grand Central Station functions with a high level of organization: People and objects move from one location to another, they cross or are contained within certain boundaries, and they provide a constant flow as part of larger activity. Analogously, a plasma membrane s functions involve movement within the cell and across boundaries in the process of intracellular and intercellular activities. (credit: modification of work by Randy Le Moine) 

The plasma membrane, which is also called the cell membrane, has many functions; but, the most basic one is to define the borders and act as gatekeeper for the cell. The plasma membrane is selectively permeable, meaning some molecules can freely enter or leave the cell. Others require help from specialized structures, other molecules, or require energy in order to cross. One example of a molecule that assists other molecules across the plasma membrane is a protein called NPC1. This protein is involved in moving cholesterol and other types of fats across the plasma membrane. Some people have a genetic condition resulting in improperly functioning NPC1. As a result, excessive cholesterol accumulates within cells causing a condition called NPC Disease. 

Scientists from the Albert Einstein College of Medicine, Harvard Medical School, and the Whitehead Institute for Biomedical Research discovered that the Ebola virus also uses NPC1 to hitch a ride into cells and replicate. The scientists used mice that lacked the NPC1 protein to test this hypothesis. When the scientists tried to infect these mice with Ebola, none of the mice got sick. Then they tried to infect mice with partially functioning NPC1 and found that they got sick, but did not die. In other words, without properly functioning NPC1, the Ebola virus cannot infect a mouse. If this pattern also exists in humans, it means that anyone with NPC Disease and its subsequent problem with high cholesterol may also be protected from Ebola. 

The complete research report can be found here . 

Show students a wilted plant and ask them why the plant has wilted. What is happening on a cellular level regarding movement of molecules? Can the wilting can be reversed? 

Plants have cell walls that surround the plasma membrane and prevent cell lysis in a hypotonic solution. The plasma membrane can only expand to the limit of the cell wall, so the cell will not lyse. In fact, the cytoplasm in plants is always slightly hypertonic to the cellular environment and water will always enter a cell if water is available. This inflow of water produces turgor pressure, which stiffens the cell walls of the plant. In non-woody plants, turgor pressure supports the plant. Conversely, if the plant is not watered, the extracellular fluid will become hypertonic, causing water to leave the cell. In this condition, the cell does not shrink because the cell wall is not flexible. However, the cell membrane detaches from the wall and constricts the cytoplasm. This is called plasmolysis. Plants in this condition lose turgor pressure and wilt. 

Before students begin this chapter, it is useful to review these concepts: Plasma membranes are the membrane boundary of all cells. Eukaryotic cells have a plasma membrane and intracellular membranes: including: a nuclear membrane and membrane-bound organelles (such as mitochondria). In contrast, prokaryotic cells only have a plasma membrane. 

Also, review definitions: intracellular, extracellular, cytosol, and extracellular fluid; cell surface to area rations and rates of diffusion.Components and Structure Components and Structure 

In this section, you will explore the following questions: How does the fluid mosaic model describe the structure and components of the plasma cell membrane? How do the molecular components of the membrane provide fluidity? Connection for AP Courses 

Like an art mosaic, the plasma membrane consists of several different components. Phospholipids (which we studied in previously) form a bilayer; the hydrophobic, fatty acid tails are in contact with each other and hydrophilic portions of the phospholipids are oriented toward the aqueous internal and external environments. Several types of proteins with different functions stud the membrane. Integral proteins often span the membrane and can transport materials into or out of the cells; these embedded proteins can be hydrophilic or hydrophobic, depending on their placement within the membrane. Peripheral proteins found on the exterior and interior surfaces of membranes can serve as enzymes, structural attachments for fibers of the cytoskeleton, and part of a cell s recognition sites. These cell-specific proteins play a vital role in immune function; enable cells of a certain type (e.g., liver cells) to identify each other when forming a tissue; and allow hormones and other molecules to recognize target cells. These proteins float throughout the membrane, constantly in flux. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The learning objectives provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.1 Cell membranes are selectively permeable due to their structure. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.10 The student is able to use representations and models to pose scientific questions about the properties of cell membranes and selective permeability based on molecular structure. Essential Knowledge 2.B.1 Cell membranes are selectively permeable due to their structure. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize and extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 2.11 The student is able to construct models that connect the movement of molecules across membrane with membrane structure and function. 

Educreations is a free iPad app that allows students to build electronic slides with narration. If student have access to an iPad, have students use the app to construct a model of the plasma membrane and its molecular components complete with an audio narrative. For more information, go here . 

Students may think that all cell membranes are identical. Discuss with students not all membranes are identical, and different membranes differ in composition. While all membranes consist of phospholipid bilayers, different membranes will contain unique, proteins that relate to the function of the cell or organelle. In addition, membrane composition can differ depending on how fluid the membrane needs to be. Membranes can differ in saturated fatty acid content (increasing rigidity) versus unsaturated fatty acid content, as well as cholesterol content, which protects the fluidity of the membrane from temperature change. 

The cell membrane has different lipid and protein compositions in distinct types of cells and may have therefore specific names for certain cell types, such as: Sarcolemma in myocytes, Oolemma in oocytes, and Axolemma in neuronal processes axons. 

A cell s plasma membrane defines the cell, outlines its borders, and determines the nature of its interaction with its environment (see [link] for a summary). Cells exclude some substances, take in others, and excrete still others, all in controlled quantities. The plasma membrane must be very flexible to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries. These are the more obvious functions of a plasma membrane. In addition, the surface of the plasma membrane carries markers that allow cells to recognize one another, which is vital for tissue and organ formation during early development, and which later plays a role in the self versus non-self distinction of the immune response. 

Among the most sophisticated functions of the plasma membrane is the ability to transmit signals by means of complex, integral proteins known as receptors. These proteins act both as receivers of extracellular inputs and as activators of intracellular processes. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors, and they activate intracellular response cascades when their effectors are bound. Occasionally, receptors are hijacked by viruses (HIV, human immunodeficiency virus, is one example) that use them to gain entry into cells, and at times, the genes encoding receptors become mutated, causing the process of signal transduction to malfunction with disastrous consequences. Fluid Mosaic Model 

The existence of the plasma membrane was identified in the 1890s, and its chemical components were identified in 1915. The principal components identified at that time were lipids and proteins. The first widely accepted model of the plasma membrane s structure was proposed in 1935 by Hugh Davson and James Danielli; it was based on the railroad track appearance of the plasma membrane in early electron micrographs. They theorized that the structure of the plasma membrane resembles a sandwich, with protein being analogous to the bread, and lipids being analogous to the filling. In the 1950s, advances in microscopy, notably transmission electron microscopy (TEM), allowed researchers to see that the core of the plasma membrane consisted of a double, rather than a single, layer. A new model that better explains both the microscopic observations and the function of that plasma membrane was proposed by S.J. Singer and Garth L. Nicolson in 1972. 

The explanation proposed by Singer and Nicolson is called the fluid mosaic model . The model has evolved somewhat over time, but it still best accounts for the structure and functions of the plasma membrane as we now understand them. The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components including phospholipids, cholesterol, proteins, and carbohydrates that gives the membrane a fluid character. Plasma membranes range from 5 to 10 nm in thickness. For comparison, human red blood cells, visible via light microscopy, are approximately 8 m wide, or approximately 1,000 times wider than a plasma membrane. The membrane does look a bit like a sandwich ( [link] ). The fluid mosaic model of the plasma membrane describes the plasma membrane as a fluid combination of phospholipids, cholesterol, and proteins. Carbohydrates attached to lipids (glycolipids) and to proteins (glycoproteins) extend from the outward-facing surface of the membrane. 

The principal components of a plasma membrane are lipids (phospholipids and cholesterol), proteins, and carbohydrates attached to some of the lipids and some of the proteins. A phospholipid is a molecule consisting of glycerol, two fatty acids, and a phosphate-linked head group. Cholesterol, another lipid composed of four fused carbon rings, is found alongside the phospholipids in the core of the membrane. The proportions of proteins, lipids, and carbohydrates in the plasma membrane vary with cell type, but for a typical human cell, protein accounts for about 50 percent of the composition by mass, lipids (of all types) account for about 40 percent of the composition by mass, with the remaining 10 percent of the composition by mass being carbohydrates. However, the concentration of proteins and lipids varies with different cell membranes. For example, myelin, an outgrowth of the membrane of specialized cells that insulates the axons of the peripheral nerves, contains only 18 percent protein and 76 percent lipid. The mitochondrial inner membrane contains 76 percent protein and only 24 percent lipid. The plasma membrane of human red blood cells is 30 percent lipid. Carbohydrates are present only on the exterior surface of the plasma membrane and are attached to proteins, forming glycoproteins , or attached to lipids, forming glycolipids . Phospholipids 

The main fabric of the membrane is composed of amphiphilic, phospholipid molecules. The hydrophilic or water-loving areas of these molecules (which look like a collection of balls in an artist s rendition of the model) ( [link] ) are in contact with the aqueous fluid both inside and outside the cell. Hydrophobic , or water-hating molecules, tend to be non-polar. They interact with other non-polar molecules in chemical reactions, but generally do not interact with polar molecules. When placed in water, hydrophobic molecules tend to form a ball or cluster. The hydrophilic regions of the phospholipids tend to form hydrogen bonds with water and other polar molecules on both the exterior and interior of the cell. Thus, the membrane surfaces that face the interior and exterior of the cell are hydrophilic. In contrast, the interior of the cell membrane is hydrophobic and will not interact with water. Therefore, phospholipids form an excellent two-layer cell membrane that separates fluid within the cell from the fluid outside of the cell. 

A phospholipid molecule ( [link] ) consists of a three-carbon glycerol backbone with two fatty acid molecules attached to carbons 1 and 2, and a phosphate-containing group attached to the third carbon. This arrangement gives the overall molecule an area described as its head (the phosphate-containing group), which has a polar character or negative charge, and an area called the tail (the fatty acids), which has no charge. The head can form hydrogen bonds, but the tail cannot. A molecule with this arrangement of a positively or negatively charged area and an uncharged, or non-polar, area is referred to as amphiphilic or dual-loving. This phospholipid molecule is composed of a hydrophilic head and two hydrophobic tails. The hydrophilic head group consists of a phosphate-containing group attached to a glycerol molecule. The hydrophobic tails, each containing either a saturated or an unsaturated fatty acid, are long hydrocarbon chains. 

This characteristic is vital to the structure of a plasma membrane because, in water, phospholipids tend to become arranged with their hydrophobic tails facing each other and their hydrophilic heads facing out. In this way, they form a lipid bilayer a barrier composed of a double layer of phospholipids that separates the water and other materials on one side of the barrier from the water and other materials on the other side. In fact, phospholipids heated in an aqueous solution tend to spontaneously form small spheres or droplets (called micelles or liposomes), with their hydrophilic heads forming the exterior and their hydrophobic tails on the inside ( [link] ). In an aqueous solution, phospholipids tend to arrange themselves with their polar heads facing outward and their hydrophobic tails facing inward. (credit: modification of work by Mariana Ruiz Villareal) Proteins 

Proteins make up the second major component of plasma membranes. Integral proteins (some specialized types are called integrins) are, as their name suggests, integrated completely into the membrane structure, and their hydrophobic membrane-spanning regions interact with the hydrophobic region of the the phospholipid bilayer ( [link] ). Single-pass integral membrane proteins usually have a hydrophobic transmembrane segment that consists of 20 25 amino acids. Some span only part of the membrane associating with a single layer while others stretch from one side of the membrane to the other, and are exposed on either side. Some complex proteins are composed of up to 12 segments of a single protein, which are extensively folded and embedded in the membrane ( [link] ). This type of protein has a hydrophilic region or regions, and one or several mildly hydrophobic regions. This arrangement of regions of the protein tends to orient the protein alongside the phospholipids, with the hydrophobic region of the protein adjacent to the tails of the phospholipids and the hydrophilic region or regions of the protein protruding from the membrane and in contact with the cytosol or extracellular fluid. Integral membranes proteins may have one or more alpha-helices that span the membrane (examples 1 and 2), or they may have beta-sheets that span the membrane (example 3). (credit: Foobar /Wikimedia Commons) 

Peripheral proteins are found on the exterior and interior surfaces of membranes, attached either to integral proteins or to phospholipids. Peripheral proteins, along with integral proteins, may serve as enzymes, as structural attachments for the fibers of the cytoskeleton, or as part of the cell s recognition sites. These are sometimes referred to as cell-specific proteins. The body recognizes its own proteins and attacks foreign proteins associated with invasive pathogens. Carbohydrates 

Carbohydrates are the third major component of plasma membranes. They are always found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids) ( [link] ). These carbohydrate chains may consist of 2 60 monosaccharide units and can be either straight or branched. Along with peripheral proteins, carbohydrates form specialized sites on the cell surface that allow cells to recognize each other. These sites have unique patterns that allow the cell to be recognized, much the way that the facial features unique to each person allow him or her to be recognized. This recognition function is very important to cells, as it allows the immune system to differentiate between body cells (called self ) and foreign cells or tissues (called non-self ). Similar types of glycoproteins and glycolipids are found on the surfaces of viruses and may change frequently, preventing immune cells from recognizing and attacking them. 

These carbohydrates on the exterior surface of the cell the carbohydrate components of both glycoproteins and glycolipids are collectively referred to as the glycocalyx (meaning sugar coating ). The glycocalyx is highly hydrophilic and attracts large amounts of water to the surface of the cell. This aids in the interaction of the cell with its watery environment and in the cell s ability to obtain substances dissolved in the water. As discussed above, the glycocalyx is also important for cell identification, self/non-self determination, and embryonic development, and is used in cell-cell attachments to form tissues. 

How Viruses Infect Specific Organs Glycoprotein and glycolipid patterns on the surfaces of cells give many viruses an opportunity for infection. HIV and hepatitis viruses infect only specific organs or cells in the human body. HIV is able to penetrate the plasma membranes of a subtype of lymphocytes called T-helper cells, as well as some monocytes and central nervous system cells. The hepatitis virus attacks liver cells. 

These viruses are able to invade these cells, because the cells have binding sites on their surfaces that are specific to and compatible with certain viruses ( [link] ). Other recognition sites on the virus s surface interact with the human immune system, prompting the body to produce antibodies. Antibodies are made in response to the antigens or proteins associated with invasive pathogens, or in response to foreign cells, such as might occur with an organ transplant. These same sites serve as places for antibodies to attach and either destroy or inhibit the activity of the virus. Unfortunately, these recognition sites on HIV change at a rapid rate because of mutations, making the production of an effective vaccine against the virus very difficult, as the virus evolves and adapts. A person infected with HIV will quickly develop different populations, or variants, of the virus that are distinguished by differences in these recognition sites. This rapid change of surface markers decreases the effectiveness of the person s immune system in attacking the virus, because the antibodies will not recognize the new variations of the surface patterns. In the case of HIV, the problem is compounded by the fact that the virus specifically infects and destroys cells involved in the immune response, further incapacitating the host. HIV binds to the CD4 receptor, a glycoprotein on the surfaces of T cells. (credit: modification of work by NIH, NIAID) 

[link] Membrane Fluidity 

The mosaic characteristic of the membrane, described in the fluid mosaic model, helps to illustrate its nature. The integral proteins and lipids exist in the membrane as separate but loosely attached molecules. These resemble the separate, multicolored tiles of a mosaic picture, and they float, moving somewhat with respect to one another. The membrane is not like a balloon, however, that can expand and contract; rather, it is fairly rigid and can burst if penetrated or if a cell takes in too much water. However, because of its mosaic nature, a very fine needle can easily penetrate a plasma membrane without causing it to burst, and the membrane will flow and self-seal when the needle is extracted. 

The mosaic characteristics of the membrane explain some but not all of its fluidity. There are two other factors that help maintain this fluid characteristic. One factor is the nature of the phospholipids themselves. In their saturated form, the fatty acids in phospholipid tails are saturated with bound hydrogen atoms. There are no double bonds between adjacent carbon atoms. This results in tails that are relatively straight. In contrast, unsaturated fatty acids do not contain a maximal number of hydrogen atoms, but they do contain some double bonds between adjacent carbon atoms; a double bond results in a bend in the string of carbons of approximately 30 degrees ( [link] ). 

Thus, if saturated fatty acids, with their straight tails, are compressed by decreasing temperatures, they press in on each other, making a dense and fairly rigid membrane. If unsaturated fatty acids are compressed, the kinks in their tails elbow adjacent phospholipid molecules away, maintaining some space between the phospholipid molecules. This elbow room helps to maintain fluidity in the membrane at temperatures at which membranes with saturated fatty acid tails in their phospholipids would freeze or solidify. The relative fluidity of the membrane is particularly important in a cold environment. A cold environment tends to compress membranes composed largely of saturated fatty acids, making them less fluid and more susceptible to rupturing. Many organisms (fish are one example) are capable of adapting to cold environments by changing the proportion of unsaturated fatty acids in their membranes in response to the lowering of the temperature. 

Visit this site to see animations of the fluidity and mosaic quality of membranes. 

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Animals have an additional membrane constituent that assists in maintaining fluidity. Cholesterol, which lies alongside the phospholipids in the membrane, tends to dampen the effects of temperature on the membrane. Thus, this lipid functions as a buffer, preventing lower temperatures from inhibiting fluidity and preventing increased temperatures from increasing fluidity too much. Thus, cholesterol extends, in both directions, the range of temperature in which the membrane is appropriately fluid and consequently functional. Cholesterol also serves other functions, such as organizing clusters of transmembrane proteins into lipid rafts. The Components and Functions of the Plasma Membrane Component Location Phospholipid Main fabric of the membrane Cholesterol Attached between phospholipids and between the two phospholipid layers Integral proteins (for example, integrins) Embedded within the phospholipid layer(s). May or may not penetrate through both layers Peripheral proteins On the inner or outer surface of the phospholipid bilayer; not embedded within the phospholipids Carbohydrates (components of glycoproteins and glycolipids) Generally attached to proteins on the outside membrane layer 

Immunologist The variations in peripheral proteins and carbohydrates that affect a cell s recognition sites are of prime interest in immunology. These changes are taken into consideration in vaccine development. Many infectious diseases, such as smallpox, polio, diphtheria, and tetanus, were conquered by the use of vaccines. 

Immunologists are the physicians and scientists who research and develop vaccines, as well as treat and study allergies or other immune problems. Some immunologists study and treat autoimmune problems (diseases in which a person s immune system attacks his or her own cells or tissues, such as lupus) and immunodeficiencies, whether acquired (such as acquired immunodeficiency syndrome, or AIDS) or hereditary (such as severe combined immunodeficiency, or SCID). Immunologists are called in to help treat organ transplantation patients, who must have their immune systems suppressed so that their bodies will not reject a transplanted organ. Some immunologists work to understand natural immunity and the effects of a person s environment on it. Others work on questions about how the immune system affects diseases such as cancer. In the past, the importance of having a healthy immune system in preventing cancer was not at all understood. 

To work as an immunologist, a PhD or MD is required. In addition, immunologists undertake at least 2 3 years of training in an accredited program and must pass an examination given by the American Board of Allergy and Immunology. Immunologists must possess knowledge of the functions of the human body as they relate to issues beyond immunization, and knowledge of pharmacology and medical technology, such as medications, therapies, test materials, and surgical procedures. Activity 

Using appropriate media, construct a model of the plasma membrane and its molecular components. In the next section, you will use the model to demonstrate the movement of different substances across the membrane. Think About It 

What research questions can be asked about plasma membranes? State three questions relating to plasma membranes along with possible solutions to the questions. 

Students can use construction paper, colored pencils or markers, scissors, glue, and other media to construct a model of the plasma cell membrane and its molecular components. 

The model should include a depiction of the phospholipids of the bilayer, as well as carbohydrates, glycoproteins, cholesterol, integral proteins, and peripheral proteins. 

Questions that students may list about plasma membranes are: Why do phospholipids spontaneously form bilayers in aqueous solution? How do phospholipids and proteins contribute to the fluidity of plasma membranes? How does cholesterol affect the fluidity of the phospholipids and proteins? Why is it advantageous for membranes to be fluid? 

Possible solutions to these questions posed by students are: 

Phospholipids spontaneously form various structures in aqueous solution, including lipid bilayers. These are formed because the phospholipid tails are hydrophobic and the head is hydrophilic. This promotes the formation of structures that remove the hydrophobic tail from contact with the aqueous solution. The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist in the membrane as separate, but loosely attached molecules. The plasma membrane must be very flexible to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries. Membrane-dependent functions, such as phagocytosis and cell signaling, can be regulated by the fluidity of the cell membrane. Section Summary 

The modern understanding of the plasma membrane is referred to as the fluid mosaic model. The plasma membrane is composed of a bilayer of phospholipids, with their hydrophobic, fatty acid tails in contact with each other. The landscape of the membrane is studded with proteins, some of which span the membrane. Some of these proteins serve to transport materials into or out of the cell. Carbohydrates are attached to some of the proteins and lipids on the outward-facing surface of the membrane, forming complexes that function to identify the cell to other cells. The fluid nature of the membrane is due to temperature, the configuration of the fatty acid tails (some kinked by double bonds), the presence of cholesterol embedded in the membrane, and the mosaic nature of the proteins and protein-carbohydrate combinations, which are not firmly fixed in place. Plasma membranes enclose and define the borders of cells, but rather than being a static bag, they are dynamic and constantly in flux. Review Questions 

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[link] Glossary amphiphilic molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments fluid mosaic model describes the structure of the plasma membrane as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to proteins or lipids, respectively), resulting in a fluid character (fluidity) glycolipid combination of carbohydrates and lipids glycoprotein combination of carbohydrates and proteins hydrophilic molecule with the ability to bond with water; water-loving hydrophobic molecule that does not have the ability to bond with water; water-hating integral protein protein integrated into the membrane structure that interacts extensively with the hydrocarbon chains of membrane lipids and often spans the membrane; these proteins can be removed only by the disruption of the membrane by detergents peripheral protein protein found at the surface of a plasma membrane either on its exterior or interior side; these proteins can be removed (washed off of the membrane) by a high-salt washPassive Transport Passive Transport 

By the end of this section, you will be able to: Identify and describe the properties of life. Why and how does passive transport occur across membranes? What is tonicity, and how is it relevant to passive transport? Connection for AP Courses 

Preventing dehydration is important for both plants and animals. Water moves across plasma membranes by a specific type of diffusion called osmosis. The concentration gradient of water across a membrane is inversely proportional to the concentration of solutes; that is, water moves through channel proteins called aquaporins from higher water concentration to lower water concentration. Solute concentration outside and inside the cell influences the rate of osmosis. Tonicity describes how the extracellular concentration of solutes can change the volume of a cell by affecting osmosis, often correlating with the osmolarity of the solution, i.e., the total solute concentration of the solution. In a hypotonic situation, because the extracellular fluid has a lower concentration of solutes (lower osmolarity) than the fluid inside the cell, water enters the cell, causing it to swell and possibly burst. The cell walls of plants prevent them from bursting, but animal cells, such as red blood cells, can lyse. When a cell is placed in a hypertonic solution, water leaves the cell because the cell has a higher water potential than the extracellular solution. When the concentrations of solute are equal on both sides of the membrane (isotonic), no net movement of water into or out of the cell occurs. Living organisms have evolved a variety of ways to maintain osmotic balance; for example, marine fish secrete excess salt through the gills to maintain dynamic homeostasis. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.11 The student is able to construct models that connect the movement of molecules across membranes with membrane structure and function. Essential Knowledge 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.12 The student is able to use representations and models to analyze situation or solve problems qualitatively and quantitatively to investigate whether dynamic homeostasis is maintained by the active movement of molecules across membranes. 

Discuss with students what semi permeable membranes are and how artificial membranes can be used to purify water using reverse osmosis. For more information, go here . 

Students may think that diffusion and osmosis are identical and the terms are interchangeable. Discuss with students the difference between diffusion and osmosis. Diffusion is the movement of solutes from an area of high concentration to an area of lower concentration. Osmosis is the movement of water molecules across a semipermeable membrane in a direction to balance the solute concentration. In diffusion, the solutes move. In osmosis, the water moves. In both, the goal is the same: to balance out the solute concentration. 

Plasma membranes must allow certain substances to enter and leave a cell, and prevent some harmful materials from entering and some essential materials from leaving. In other words, plasma membranes are selectively permeable they allow some substances to pass through, but not others. If they were to lose this selectivity, the cell would no longer be able to sustain itself, and it would be destroyed. Some cells require larger amounts of specific substances than do other cells; they must have a way of obtaining these materials from extracellular fluids. This may happen passively, as certain materials move back and forth, or the cell may have special mechanisms that facilitate transport. Some materials are so important to a cell that it spends some of its energy, hydrolyzing adenosine triphosphate (ATP), to obtain these materials. Red blood cells use some of their energy doing just that. All cells spend the majority of their energy to maintain an imbalance of sodium and potassium ions between the interior and exterior of the cell. 

The most direct forms of membrane transport are passive. Passive transport is a naturally occurring phenomenon and does not require the cell to exert any of its energy to accomplish the movement. In passive transport, substances move from an area of higher concentration to an area of lower concentration. A physical space in which there is a range of concentrations of a single substance is said to have a concentration gradient . Selective Permeability 

Plasma membranes are asymmetric: the interior of the membrane is not identical to the exterior of the membrane. In fact, there is a considerable difference between the array of phospholipids and proteins between the two leaflets that form a membrane. On the interior of the membrane, some proteins serve to anchor the membrane to fibers of the cytoskeleton. There are peripheral proteins on the exterior of the membrane that bind elements of the extracellular matrix. Carbohydrates, attached to lipids or proteins, are also found on the exterior surface of the plasma membrane. These carbohydrate complexes help the cell bind substances that the cell needs in the extracellular fluid. This adds considerably to the selective nature of plasma membranes ( [link] ). The exterior surface of the plasma membrane is not identical to the interior surface of the same membrane. 

Recall that plasma membranes are amphiphilic: They have hydrophilic and hydrophobic regions. This characteristic helps the movement of some materials through the membrane and hinders the movement of others. Lipid-soluble material with a low molecular weight can easily slip through the hydrophobic lipid core of the membrane. Substances such as the fat-soluble vitamins A, D, E, and K readily pass through the plasma membranes in the digestive tract and other tissues. Fat-soluble drugs and hormones also gain easy entry into cells and are readily transported into the body s tissues and organs. Molecules of oxygen and carbon dioxide have no charge and so pass through membranes by simple diffusion. 

Polar substances present problems for the membrane. While some polar molecules connect easily with the outside of a cell, they cannot readily pass through the lipid core of the plasma membrane. Additionally, while small ions could easily slip through the spaces in the mosaic of the membrane, their charge prevents them from doing so. Ions such as sodium, potassium, calcium, and chloride must have special means of penetrating plasma membranes. Simple sugars and amino acids also need help with transport across plasma membranes, achieved by various transmembrane proteins (channels). Diffusion 

Diffusion is a passive process of transport. A single substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across a space. You are familiar with diffusion of substances through the air. For example, think about someone opening a bottle of ammonia in a room filled with people. The ammonia gas is at its highest concentration in the bottle; its lowest concentration is at the edges of the room. The ammonia vapor will diffuse, or spread away, from the bottle, and gradually, more and more people will smell the ammonia as it spreads. Materials move within the cell s cytosol by diffusion, and certain materials move through the plasma membrane by diffusion ( [link] ). Diffusion expends no energy. On the contrary, concentration gradients are a form of potential energy, dissipated as the gradient is eliminated. Diffusion through a permeable membrane moves a substance from an area of high concentration (extracellular fluid, in this case) down its concentration gradient (into the cytoplasm). (credit: modification of work by Mariana Ruiz Villareal) 

Each separate substance in a medium, such as the extracellular fluid, has its own concentration gradient, independent of the concentration gradients of other materials. In addition, each substance will diffuse according to that gradient. Within a system, there will be different rates of diffusion of the different substances in the medium. Factors That Affect Diffusion 

Molecules move constantly in a random manner, at a rate that depends on their mass, their environment, and the amount of thermal energy they possess, which in turn is a function of temperature. This movement accounts for the diffusion of molecules through whatever medium in which they are localized. A substance will tend to move into any space available to it until it is evenly distributed throughout it. After a substance has diffused completely through a space, removing its concentration gradient, molecules will still move around in the space, but there will be no net movement of the number of molecules from one area to another. This lack of a concentration gradient in which there is no net movement of a substance is known as dynamic equilibrium. While diffusion will go forward in the presence of a concentration gradient of a substance, several factors affect the rate of diffusion. Extent of the concentration gradient: The greater the difference in concentration, the more rapid the diffusion. The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes. Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly. The reverse is true for lighter molecules. Temperature: Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. Lower temperatures decrease the energy of the molecules, thus decreasing the rate of diffusion. Solvent density: As the density of a solvent increases, the rate of diffusion decreases. The molecules slow down because they have a more difficult time getting through the denser medium. If the medium is less dense, diffusion increases. Because cells primarily use diffusion to move materials within the cytoplasm, any increase in the cytoplasm s density will inhibit the movement of the materials. An example of this is a person experiencing dehydration. As the body s cells lose water, the rate of diffusion decreases in the cytoplasm, and the cells functions deteriorate. Neurons tend to be very sensitive to this effect. Dehydration frequently leads to unconsciousness and possibly coma because of the decrease in diffusion rate within the cells. Solubility: As discussed earlier, nonpolar or lipid-soluble materials pass through plasma membranes more easily than polar materials, allowing a faster rate of diffusion. Surface area and thickness of the plasma membrane: Increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it. Distance travelled: The greater the distance that a substance must travel, the slower the rate of diffusion. This places an upper limitation on cell size. A large, spherical cell will die because nutrients or waste cannot reach or leave the center of the cell, respectively. Therefore, cells must either be small in size, as in the case of many prokaryotes, or be flattened, as with many single-celled eukaryotes. 

A variation of diffusion is the process of filtration. In filtration, material moves according to its concentration gradient through a membrane; sometimes the rate of diffusion is enhanced by pressure, causing the substances to filter more rapidly. This occurs in the kidney, where blood pressure forces large amounts of water and accompanying dissolved substances, or solutes , out of the blood and into the renal tubules. The rate of diffusion in this instance is almost totally dependent on pressure. One of the effects of high blood pressure is the appearance of protein in the urine, which is squeezed through by the abnormally high pressure. Facilitated transport 

In facilitated transport , also called facilitated diffusion, materials diffuse across the plasma membrane with the help of membrane proteins. A concentration gradient exists that would allow these materials to diffuse into the cell without expending cellular energy. However, these materials are ions are polar molecules that are repelled by the hydrophobic parts of the cell membrane. Facilitated transport proteins shield these materials from the repulsive force of the membrane, allowing them to diffuse into the cell. 

The material being transported is first attached to protein or glycoprotein receptors on the exterior surface of the plasma membrane. This allows the material that is needed by the cell to be removed from the extracellular fluid. The substances are then passed to specific integral proteins that facilitate their passage. Some of these integral proteins are collections of beta pleated sheets that form a pore or channel through the phospholipid bilayer. Others are carrier proteins which bind with the substance and aid its diffusion through the membrane. Channels 

The integral proteins involved in facilitated transport are collectively referred to as transport proteins , and they function as either channels for the material or carriers. In both cases, they are transmembrane proteins. Channels are specific for the substance that is being transported. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids; they additionally have a hydrophilic channel through their core that provides a hydrated opening through the membrane layers ( [link] ). Passage through the channel allows polar compounds to avoid the nonpolar central layer of the plasma membrane that would otherwise slow or prevent their entry into the cell. Aquaporins are channel proteins that allow water to pass through the membrane at a very high rate. Facilitated transport moves substances down their concentration gradients. They may cross the plasma membrane with the aid of channel proteins. (credit: modification of work by Mariana Ruiz Villareal) 

Channel proteins are either open at all times or they are gated, which controls the opening of the channel. The attachment of a particular ion to the channel protein may control the opening, or other mechanisms or substances may be involved. In some tissues, sodium and chloride ions pass freely through open channels, whereas in other tissues a gate must be opened to allow passage. An example of this occurs in the kidney, where both forms of channels are found in different parts of the renal tubules. Cells involved in the transmission of electrical impulses, such as nerve and muscle cells, have gated channels for sodium, potassium, and calcium in their membranes. Opening and closing of these channels changes the relative concentrations on opposing sides of the membrane of these ions, resulting in the facilitation of electrical transmission along membranes (in the case of nerve cells) or in muscle contraction (in the case of muscle cells). Carrier Proteins 

Another type of protein embedded in the plasma membrane is a carrier protein . This aptly named protein binds a substance and, in doing so, triggers a change of its own shape, moving the bound molecule from the outside of the cell to its interior ( [link] ); depending on the gradient, the material may move in the opposite direction. Carrier proteins are typically specific for a single substance. This selectivity adds to the overall selectivity of the plasma membrane. The exact mechanism for the change of shape is poorly understood. Proteins can change shape when their hydrogen bonds are affected, but this may not fully explain this mechanism. Each carrier protein is specific to one substance, and there are a finite number of these proteins in any membrane. This can cause problems in transporting enough of the material for the cell to function properly. When all of the proteins are bound to their ligands, they are saturated and the rate of transport is at its maximum. Increasing the concentration gradient at this point will not result in an increased rate of transport. Some substances are able to move down their concentration gradient across the plasma membrane with the aid of carrier proteins. Carrier proteins change shape as they move molecules across the membrane. (credit: modification of work by Mariana Ruiz Villareal) 

An example of this process occurs in the kidney. Glucose, water, salts, ions, and amino acids needed by the body are filtered in one part of the kidney. This filtrate, which includes glucose, is then reabsorbed in another part of the kidney. Because there are only a finite number of carrier proteins for glucose, if more glucose is present than the proteins can handle, the excess is not transported and it is excreted from the body in the urine. In a diabetic individual, this is described as spilling glucose into the urine. A different group of carrier proteins called glucose transport proteins, or GLUTs, are involved in transporting glucose and other hexose sugars through plasma membranes within the body. 

Channel and carrier proteins transport material at different rates. Channel proteins transport much more quickly than do carrier proteins. Channel proteins facilitate diffusion at a rate of tens of millions of molecules per second, whereas carrier proteins work at a rate of a thousand to a million molecules per second. Osmosis 

Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes. While diffusion transports material across membranes and within cells, osmosis transports only water across a membrane and the membrane limits the diffusion of solutes in the water. Not surprisingly, the aquaporins that facilitate water movement play a large role in osmosis, most prominently in red blood cells and the membranes of kidney tubules. Mechanism 

Osmosis is a special case of diffusion. Water, like other substances, moves from an area of high concentration to one of low concentration. An obvious question is what makes water move at all? Imagine a beaker with a semipermeable membrane separating the two sides or halves ( [link] ). On both sides of the membrane the water level is the same, but there are different concentrations of a dissolved substance, or solute , that cannot cross the membrane (otherwise the concentrations on each side would be balanced by the solute crossing the membrane). If the volume of the solution on both sides of the membrane is the same, but the concentrations of solute are different, then there are different amounts of water, the solvent, on either side of the membrane. In osmosis, water always moves from an area of higher water concentration to one of lower concentration. In the diagram shown, the solute cannot pass through the selectively permeable membrane, but the water can. 

To illustrate this, imagine two full glasses of water. One has a single teaspoon of sugar in it, whereas the second one contains one-quarter cup of sugar. If the total volume of the solutions in both cups is the same, which cup contains more water? Because the large amount of sugar in the second cup takes up much more space than the teaspoon of sugar in the first cup, the first cup has more water in it. 

Returning to the beaker example, recall that it has a mixture of solutes on either side of the membrane. A principle of diffusion is that the molecules move around and will spread evenly throughout the medium if they can. However, only the material capable of getting through the membrane will diffuse through it. In this example, the solute cannot diffuse through the membrane, but the water can. Water has a concentration gradient in this system. Thus, water will diffuse down its concentration gradient, crossing the membrane to the side where it is less concentrated. This diffusion of water through the membrane osmosis will continue until the concentration gradient of water goes to zero or until the hydrostatic pressure of the water balances the osmotic pressure. Osmosis proceeds constantly in living systems. Tonicity 

Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis. A solution's tonicity often directly correlates with the osmolarity of the solution. Osmolarity describes the total solute concentration of the solution. A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles. In a situation in which solutions of two different osmolarities are separated by a membrane permeable to water, though not to the solute, water will move from the side of the membrane with lower osmolarity (and more water) to the side with higher osmolarity (and less water). This effect makes sense if you remember that the solute cannot move across the membrane, and thus the only component in the system that can move the water moves along its own concentration gradient. An important distinction that concerns living systems is that osmolarity measures the number of particles (which may be molecules) in a solution. Therefore, a solution that is cloudy with cells may have a lower osmolarity than a solution that is clear, if the second solution contains more dissolved molecules than there are cells. Hypotonic Solutions 

Three terms hypotonic, isotonic, and hypertonic are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo - means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm.) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell. Hypertonic Solutions 

As for a hypertonic solution, the prefix hyper - refers to the extracellular fluid having a higher osmolarity than the cell s cytoplasm; therefore, the fluid contains less water than the cell does. Because the cell has a relatively higher concentration of water, water will leave the cell. Isotonic Solutions 

In an isotonic solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out. Blood cells and plant cells in hypertonic, isotonic, and hypotonic solutions take on characteristic appearances ( [link] ). 

Osmotic pressure changes the shape of red blood cells in hypertonic, isotonic, and hypotonic solutions (credit: Mariana Ruiz Villareal) 

For a video illustrating the process of diffusion in solutions, visit this site . 

[link] Tonicity in Living Systems 

In a hypotonic environment, water enters a cell, and the cell swells. In an isotonic condition, the relative concentrations of solute and solvent are equal on both sides of the membrane. There is no net water movement; therefore, there is no change in the size of the cell. In a hypertonic solution, water leaves a cell and the cell shrinks. If either the hypo- or hyper- condition goes to excess, the cell s functions become compromised, and the cell may be destroyed. 

A red blood cell will burst, or lyse, when it swells beyond the plasma membrane s capability to expand. Remember, the membrane resembles a mosaic, with discrete spaces between the molecules composing it. If the cell swells, and the spaces between the lipids and proteins become too large, the cell will break apart. 

In contrast, when excessive amounts of water leave a red blood cell, the cell shrinks, or crenates. This has the effect of concentrating the solutes left in the cell, making the cytosol denser and interfering with diffusion within the cell. The cell s ability to function will be compromised and may also result in the death of the cell. 

Various living things have ways of controlling the effects of osmosis a mechanism called osmoregulation. Some organisms, such as plants, fungi, bacteria, and some protists, have cell walls that surround the plasma membrane and prevent cell lysis in a hypotonic solution. The plasma membrane can only expand to the limit of the cell wall, so the cell will not lyse. In fact, the cytoplasm in plants is always slightly hypertonic to the cellular environment, and water will always enter a cell if water is available. This inflow of water produces turgor pressure, which stiffens the cell walls of the plant ( [link] ). In nonwoody plants, turgor pressure supports the plant. Conversly, if the plant is not watered, the extracellular fluid will become hypertonic, causing water to leave the cell. In this condition, the cell does not shrink because the cell wall is not flexible. However, the cell membrane detaches from the wall and constricts the cytoplasm. This is called plasmolysis . Plants lose turgor pressure in this condition and wilt ( [link] ). The turgor pressure within a plant cell depends on the tonicity of the solution that it is bathed in. (credit: modification of work by Mariana Ruiz Villareal) Without adequate water, the plant on the left has lost turgor pressure, visible in its wilting; the turgor pressure is restored by watering it (right). (credit: Victor M. Vicente Selvas) 

Tonicity is a concern for all living things. For example, paramecia and amoebas, which are protists that lack cell walls, have contractile vacuoles. This vesicle collects excess water from the cell and pumps it out, keeping the cell from lysing as it takes on water from its environment ( [link] ). A paramecium s contractile vacuole, here visualized using bright field light microscopy at 480x magnification, continuously pumps water out of the organism s body to keep it from bursting in a hypotonic medium. (credit: modification of work by NIH; scale-bar data from Matt Russell) 

Many marine invertebrates have internal salt levels matched to their environments, making them isotonic with the water in which they live. Fish, however, must spend approximately five percent of their metabolic energy maintaining osmotic homeostasis. Freshwater fish live in an environment that is hypotonic to their cells. These fish actively take in salt through their gills and excrete diluted urine to rid themselves of excess water. Saltwater fish live in the reverse environment, which is hypertonic to their cells, and they secrete salt through their gills and excrete highly concentrated urine. 

In vertebrates, the kidneys regulate the amount of water in the body. Osmoreceptors are specialized cells in the brain that monitor the concentration of solutes in the blood. If the levels of solutes increase beyond a certain range, a hormone is released that retards water loss through the kidney and dilutes the blood to safer levels. Animals also have high concentrations of albumin, which is produced by the liver, in their blood. This protein is too large to pass easily through plasma membranes and is a major factor in controlling the osmotic pressures applied to tissues. Activity 

Use the model of the plasma cell membrane you constructed to demonstrate how O 2 and CO 2 , H 2 O, Na + and K + , and glucose are transported across the membrane. Think About It 

Why should farmers consider the salinity of the soil in which they grow crops? 

Answer: Farmers need to consider the salinity of soil, because the movement of water into and out of plant cells depends on the solute concentration of their environment. In soil high in saline, water will be drawn out of root cells causing the cells to shrivel, and the plant to die. Student demonstrations should include the transport of different molecules across plasma membranes, which is shown in the illustration. Molecules of oxygen, carbon dioxide, and water have no charge and so pass through membranes by simple diffusion. Na+ and K+ have a charge and require a transport protein (the sodium potassium pump) in order to move across the plasma membrane via active transport. The College Board presents an expanded diffusion/osmosis activity on which this lab investigation is based. Please see Investigation 4 in the AP Biology Investigative Labs: An Inquiry-Based Approach. 

Observing Osmosis in Model Cells 

Materials: 

3 dialysis bags 

3 medium-sized beakers 

Stock starch solution 

Distilled water 

Iodine dropper bottle 

Thread 

Balance or scale 

Preparation: 

To prepare the percent starch solutions, determine the volume of the solution you wish to use (e.g., 100 ml) and add the mass of solute, in grams, equivalent to the desired percent concentration: 

Percent solution = [Mass of solute (g) / Volume of solution (ml)] 100 Label each dialysis bag with one of the three concentrations: 1%, 25%, and 60%. Then, moisten the dialysis tubing to make it easier to open. Fill each tube with the corresponding solution about three-quarters of the way fill in order to leave space to tie off the top of the bag. Tie the tops of the bags tightly with standard thread. Do not place the bags in the iodine solution yet, as they will first be weighed in front of the students. 

With students present, explain to them the details of the setup and show them how iodine is used as an indicator for the presence of starch. Also explain that dialysis tubing is semipermeable, as it contains pores that permit the passage of small ions and molecules, like water; but will not permit the passage of larger molecules, like proteins. In this way, the dialysis bag models a semipermeable cell membrane. Fill each beaker about three-quarters of the way with distilled water. Add 3 8 drops of iodine, based on the strength of your iodine, and stir so that the solution is yellow in color. Weigh each dialysis bag and record the weights on a chart visible to the class. Ask students: If each dialysis bag were a cell, would it be hypertonic, hypotonic, or isotonic relative to the distilled water? How quickly will water flow into or out of the dialysis bag by osmosis? What will happen if the starch solution comes in contact with the iodine solution? Immerse the dialysis bags in the iodine solution for 45 min to 1 hour. While waiting, ask students to predict how osmosis will affect the weight of the three dialysis bags. Will the weight of the bags increase, decrease, or remain the same? Remove the bags and carefully rinse them under a gentle tap. Pat the bags dry to remove excess water. Weigh each bag and place the results on the board. Ask students: Was both water and starch able to pass through the dialysis tubing? How do you know, based on your results? Did the concentration of the starch solutions affect the rate of osmosis? Why would this occur? 

Results: 

Starch molecules cannot pass through the dialysis tubing. However, the iodine solution can pass from the beaker into the dialysis bag. This turns the starch solution from colorless to purple. The amount of iodine that diffuses into the bag is related to the concentration of each solution. As the starch concentration increases, more iodine solution will diffuse into the bag, causing the bag to increase in weight. 

This lab is an application of Learning Objective 2.4 and Science Practices 1.4 and 3.1 and Learning Objective 2.5 and Science Practice 6.2 because as students collect and analyze data in addition, as part of their experimental design, students draw conclusions from the data. Section Summary 

The passive forms of transport, diffusion and osmosis, move materials of small molecular weight across membranes. Substances diffuse from areas of high concentration to areas of lower concentration, and this process continues until the substance is evenly distributed in a system. In solutions containing more than one substance, each type of molecule diffuses according to its own concentration gradient, independent of the diffusion of other substances. Many factors can affect the rate of diffusion, including concentration gradient, size of the particles that are diffusing, temperature of the system, and so on. 

In living systems, diffusion of substances into and out of cells is mediated by the plasma membrane. Some materials diffuse readily through the membrane, but others are hindered, and their passage is made possible by specialized proteins, such as channels and transporters. The chemistry of living things occurs in aqueous solutions, and balancing the concentrations of those solutions is an ongoing problem. In living systems, diffusion of some substances would be slow or difficult without membrane proteins that facilitate transport. Review Questions 

[link] 

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[link] Critical Thinking Questions 

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[link] Test Prep for AP Courses 

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[link] Glossary aquaporin channel protein that allows water through the membrane at a very high rate carrier protein membrane protein that moves a substance across the plasma membrane by changing its own shape channel protein membrane protein that allows a substance to pass through its hollow core across the plasma membrane concentration gradient area of high concentration adjacent to an area of low concentration diffusion passive process of transport of low-molecular weight material according to its concentration gradient facilitated transport process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins hypertonic situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell hypotonic situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell isotonic situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell, resulting in no net movement of water into or out of the cell osmolarity total amount of substances dissolved in a specific amount of solution osmosis transport of water through a semipermeable membrane according to the concentration gradient of water across the membrane that results from the presence of solute that cannot pass through the membrane passive transport method of transporting material through a membrane that does not require energy plasmolysis detaching of the cell membrane from the cell wall and constriction of the cell membrane when a plant cell is in a hypertonic solution selectively permeable characteristic of a membrane that allows some substances through but not others solute substance dissolved in a liquid to form a solution tonicity amount of solute in a solution transport protein membrane protein that facilitates passage of a substance across a membrane by binding itActive Transport Active Transport 

By the end of this section, you will be able to: How do electrochemical gradients affect the active transport of ions and molecules across membranes? Connection for AP Courses 

If a substance must move into the cell against its concentration gradient, the cell must use free energy, often provided by ATP, and carrier proteins acting as pumps to move the substance. Substances that move across membranes by this mechanism, a process called active transport, include ions, such as Na + and K + . The combined gradients that affect movement of an ion are its concentration gradient and its electrical gradient (the difference in charge across the membrane); together these gradients are called the electrochemical gradient. To move substances against an electrochemical gradient requires free energy. The sodium-potassium pump, which maintains electrochemical gradients across the membranes of nerve cells in animals, is an example of primary active transport. The formation of H + gradients by secondary active transport (co-transport) is important in cellular respiration and photosynthesis and moving glucose into cells. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices (SP). 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 2.12 The student is able to use representations and models to analyze situations or solve problems qualitatively and quantitatively to investigate whether dynamic homeostasis is maintained by the active movement of molecules across membranes. 

Discuss with students the differences between passive and active transport using visuals such as this video . 

Active transport mechanisms require the use of the cell s energy, usually in the form of adenosine triphosphate (ATP). If a substance must move into the cell against its concentration gradient that is, if the concentration of the substance inside the cell is greater than its concentration in the extracellular fluid (and vice versa) the cell must use energy to move the substance. Some active transport mechanisms move small-molecular weight materials, such as ions, through the membrane. Other mechanisms transport much larger molecules. Electrochemical Gradient 

We have discussed simple concentration gradients differential concentrations of a substance across a space or a membrane but in living systems, gradients are more complex. Because ions move into and out of cells and because cells contain proteins that do not move across the membrane and are mostly negatively charged, there is also an electrical gradient, a difference of charge, across the plasma membrane. The interior of living cells is electrically negative with respect to the extracellular fluid in which they are bathed, and at the same time, cells have higher concentrations of potassium (K + ) and lower concentrations of sodium (Na + ) than does the extracellular fluid. So in a living cell, the concentration gradient of Na + tends to drive it into the cell, and the electrical gradient of Na + (a positive ion) also tends to drive it inward to the negatively charged interior. The situation is more complex, however, for other elements such as potassium. The electrical gradient of K + , a positive ion, also tends to drive it into the cell, but the concentration gradient of K + tends to drive K + out of the cell ( [link] ). The combined gradient of concentration and electrical charge that affects an ion is called its electrochemical gradient . 

Electrochemical gradients arise from the combined effects of concentration gradients and electrical gradients. (credit: Synaptitude /Wikimedia Commons) 

[link] Moving Against a Gradient 

To move substances against a concentration or electrochemical gradient, the cell must use energy. This energy is harvested from ATP generated through the cell s metabolism. Active transport mechanisms, collectively called pumps , work against electrochemical gradients. Small substances constantly pass through plasma membranes. Active transport maintains concentrations of ions and other substances needed by living cells in the face of these passive movements. Much of a cell s supply of metabolic energy may be spent maintaining these processes. (Most of a red blood cell s metabolic energy is used to maintain the imbalance between exterior and interior sodium and potassium levels required by the cell.) Because active transport mechanisms depend on a cell s metabolism for energy, they are sensitive to many metabolic poisons that interfere with the supply of ATP. 

Two mechanisms exist for the transport of small-molecular weight material and small molecules. Primary active transport moves ions across a membrane and creates a difference in charge across that membrane, which is directly dependent on ATP. Secondary active transport describes the movement of material that is due to the electrochemical gradient established by primary active transport that does not directly require ATP. Carrier Proteins for Active Transport 

An important membrane adaption for active transport is the presence of specific carrier proteins or pumps to facilitate movement: there are three types of these proteins or transporters ( [link] ). A uniporter carries one specific ion or molecule. A symporter carries two different ions or molecules, both in the same direction. An antiporter also carries two different ions or molecules, but in different directions. All of these transporters can also transport small, uncharged organic molecules like glucose. These three types of carrier proteins are also found in facilitated diffusion, but they do not require ATP to work in that process. Some examples of pumps for active transport are Na + -K + ATPase, which carries sodium and potassium ions, and H + -K + ATPase, which carries hydrogen and potassium ions. Both of these are antiporter carrier proteins. Two other carrier proteins are Ca 2+ ATPase and H + ATPase, which carry only calcium and only hydrogen ions, respectively. Both are pumps. A uniporter carries one molecule or ion. A symporter carries two different molecules or ions, both in the same direction. An antiporter also carries two different molecules or ions, but in different directions. (credit: modification of work by Lupask /Wikimedia Commons) 

The primary active transport that functions with the active transport of sodium and potassium allows secondary active transport to occur. The second transport method is still considered active because it depends on the use of energy as does primary transport (illustrative example). Primary active transport moves ions across a membrane, creating an electrochemical gradient (electrogenic transport). (credit: modification of work by Mariana Ruiz Villareal) 

One of the most important pumps in animal cells is the sodium-potassium pump (Na + -K + ATPase), which maintains the electrochemical gradient (and the correct concentrations of Na + and K + ) in living cells. The sodium-potassium pump moves K + into the cell while moving Na + out at the same time, at a ratio of three Na + for every two K + ions moved in. The Na + -K + ATPase exists in two forms, depending on its orientation to the interior or exterior of the cell and its affinity for either sodium or potassium ions. The process consists of the following six steps: With the enzyme oriented towards the interior of the cell, the carrier has a high affinity for sodium ions. Three ions bind to the protein. The protein carrier hydrolyzes ATP and a low-energy phosphate group attaches to it. As a result, the carrier changes shape and re-orients itself towards the exterior of the membrane. The protein s affinity for sodium decreases and the three sodium ions leave the carrier. The shape change increases the carrier s affinity for potassium ions, and two such ions attach to the protein. Subsequently, the low-energy phosphate group detaches from the carrier. With the phosphate group removed and potassium ions attached, the carrier protein repositions itself towards the interior of the cell. The carrier protein, in its new configuration, has a decreased affinity for potassium, and the two ions are released into the cytoplasm. The protein now has a higher affinity for sodium ions, and the process starts again. 

Several things have happened as a result of this process. At this point, there are more sodium ions outside of the cell than inside and more potassium ions inside than out. For every three ions of sodium that move out, two ions of potassium move in. This results in the interior being slightly more negative relative to the exterior. This difference in charge is important to creating the conditions necessary for the secondary process. Therefore, the sodium-potassium pump is an electrogenic pump (a pump that creates a charge imbalance) contributing to the membrane potential. 

[link] 

Visit the site to see a simulation of active transport in a sodium-potassium ATPase. 

[link] Activity 

Create a representation/diagram (or use the model you constructed of the plasma cell membrane) to explain how the sodium-potassium pump contributes to the net negative change of the interior of an animal nerve cell. Think About It 

If the pH outside the cell decreases, would you expect the amount of amino acids and glucose transported into the cell to increase or decrease? Justify your reasoning. The Na + -K + ATPase pump uses energy to move 3 Na + ions out of a neuron for every 2 K + ions moved into a neuron, which contributes to the net negative change of the interior of an animal nerve cell. Student models of the sodium-potassium pump in nerve cells should look similar to this illustration . Answer to Think About It question: A decrease in pH means an increase in positively charged H+ ions, and an increase in the electrical gradient across the membrane. The transport of amino acids into the cell will increase. Secondary Active Transport (Co-transport) 

Secondary active transport brings sodium ions, and possibly other compounds, into the cell. As sodium ion concentrations build outside of the plasma membrane because of the action of the primary active transport process, an electrochemical gradient is created. If a channel protein exists and is open, the sodium ions will be pulled through the membrane. This movement is used to transport other substances that can attach themselves to the transport protein through the membrane ( [link] ). Many amino acids, as well as glucose, enter a cell this way. This secondary process is also used to store high-energy hydrogen ions in the mitochondria of plant and animal cells for the production of ATP. The potential energy that accumulates in the stored hydrogen ions is translated into kinetic energy as the ions surge through the channel protein ATP synthase, and that energy is used to convert ADP into ATP. Visual Connections 

An electrochemical gradient, created by primary active transport, can move other substances against their concentration gradients, a process called co-transport or secondary active transport. (credit: modification of work by Mariana Ruiz Villareal) 

[link] Section Summary 

The combined gradient that affects an ion includes its concentration gradient and its electrical gradient. A positive ion, for example, might tend to diffuse into a new area, down its concentration gradient, but if it is diffusing into an area of net positive charge, its diffusion will be hampered by its electrical gradient. When dealing with ions in aqueous solutions, a combination of the electrochemical and concentration gradients, rather than just the concentration gradient alone, must be considered. Living cells need certain substances that exist inside the cell in concentrations greater than they exist in the extracellular space. Moving substances up their electrochemical gradients requires energy from the cell. Active transport uses energy stored in ATP to fuel this transport. Active transport of small molecular-sized materials uses integral proteins in the cell membrane to move the materials: These proteins are analogous to pumps. Some pumps, which carry out primary active transport, couple directly with ATP to drive their action. In co-transport (or secondary active transport), energy from primary transport can be used to move another substance into the cell and up its concentration gradient. Review Questions 

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[link] Critical Thinking Questions 

[link] Glossary active transport method of transporting material that requires energy antiporter transporter that carries two ions or small molecules in different directions electrochemical gradient gradient produced by the combined forces of an electrical gradient and a chemical gradient electrogenic pump pump that creates a charge imbalance primary active transport active transport that moves ions or small molecules across a membrane and may create a difference in charge across that membrane pump active transport mechanism that works against electrochemical gradients secondary active transport movement of material that is due to the electrochemical gradient established by primary active transport symporter transporter that carries two different ions or small molecules, both in the same direction transporter specific carrier proteins or pumps that facilitate movement uniporter transporter that carries one specific ion or moleculeBulk Transport Bulk Transport 

By the end of this section, you will be able to: What are the differences among the different types of endocytosis: (phagocytosis, pinocytosis, and receptor-mediated endocytosis) and exocytosis? Connection for AP Courses 

Diffusion, osmosis, and active transport are used to transport fairly small molecules across plasma cell membranes. However, sometimes large particles, such as macromolecules, parts of cells, or even unicellular microorganisms, can be engulfed by other cells in a process called phagocytosis or cell eating. In this form of endocytosis, the cell membrane surrounds the particle, pinches off, and brings the particle into the cell. For example, when bacteria invade the human body, a type of white blood cell called a neutrophil will remove the invaders by this process. Similarly, in pinocytosis or cell drinking, the cell takes in droplets of liquid. In receptor-mediated endocytosis, uptake of substances by the cell is targeted to a single type of substance that binds to a specific receptor protein on the external surface of the cell membrane (e.g., hormones and their target cells) before under going endocytosis. Some human diseases, such as familial hypercholesterolemia, are caused by the failure of receptor-mediated endocytosis. Exocytosis is the process of exporting material out of the cell; vesicles containing substances fuse with the plasma membrane and the contents are released to the exterior of the cell. The secretion of neurotransmitters at synapses between neurons is an example of exocytosis. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.B Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential Knowledge 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 2.12 The student is able to use representations and models to analyze situations or solve problems qualitatively and quantitatively to investigate whether dynamic homeostasis is maintained by the active movement of molecules across membranes. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system are influenced by changes in the system s environment. Essential Knowledge 2.D.4 Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 2.30 The student can create representations or models to describe nonspecific immune defenses in plants and animals. 

Ask students to consider how large polar molecules required by cells, such as proteins and polysaccharides, can enter cells when they are unable to cross cell membranes. These molecules enter cells through the active transport mechanism of endocytosis. This video on endocytosis and exocytosis can be used to demonstrate this information. 

In addition to moving small ions and molecules through the membrane, cells also need to remove and take in larger molecules and particles (see [link] for examples). Some cells are even capable of engulfing entire unicellular microorganisms. You might have correctly hypothesized that the uptake and release of large particles by the cell requires energy. A large particle, however, cannot pass through the membrane, even with energy supplied by the cell. Endocytosis 

Endocytosis is a type of active transport that moves particles, such as large molecules, parts of cells, and even whole cells, into a cell. There are different variations of endocytosis, but all share a common characteristic: The plasma membrane of the cell invaginates, forming a pocket around the target particle. The pocket pinches off, resulting in the particle being contained in a newly created intracellular vesicle formed from the plasma membrane. Phagocytosis 

Phagocytosis (the condition of cell eating ) is the process by which large particles, such as cells or relatively large particles, are taken in by a cell. For example, when microorganisms invade the human body, a type of white blood cell called a neutrophil will remove the invaders through this process, surrounding and engulfing the microorganism, which is then destroyed by the neutrophil ( [link] ). In phagocytosis, the cell membrane surrounds the particle and engulfs it. (credit: Mariana Ruiz Villareal) 

In preparation for phagocytosis, a portion of the inward-facing surface of the plasma membrane becomes coated with a protein called clathrin , which stabilizes this section of the membrane. The coated portion of the membrane then extends from the body of the cell and surrounds the particle, eventually enclosing it. Once the vesicle containing the particle is enclosed within the cell, the clathrin disengages from the membrane and the vesicle merges with a lysosome for the breakdown of the material in the newly formed compartment (endosome). When accessible nutrients from the degradation of the vesicular contents have been extracted, the newly formed endosome merges with the plasma membrane and releases its contents into the extracellular fluid. The endosomal membrane again becomes part of the plasma membrane. Activity 

Create a representation/diagram to describe how a neutrophil, a type of human white blood cell, attacks and destroys an invading bacterium. What cellular organelles are involved in this process? 

Student diagrams should show receptors in the neutrophil that bind to the bacteria and the plasma membrane of the neutrophil surrounding the bacteria. The diagram should also show a lysosome merging with vesicle containing the bacteria, and breakdown of the bacteria by the lysosome. Pinocytosis 

A variation of endocytosis is called pinocytosis . This literally means cell drinking and was named at a time when the assumption was that the cell was purposefully taking in extracellular fluid. In reality, this is a process that takes in molecules, including water, which the cell needs from the extracellular fluid. Pinocytosis results in a much smaller vesicle than does phagocytosis, and the vesicle does not need to merge with a lysosome ( [link] ). In pinocytosis, the cell membrane invaginates, surrounds a small volume of fluid, and pinches off. (credit: Mariana Ruiz Villareal) 

A variation of pinocytosis is called potocytosis . This process uses a coating protein, called caveolin , on the cytoplasmic side of the plasma membrane, which performs a similar function to clathrin. The cavities in the plasma membrane that form the vacuoles have membrane receptors and lipid rafts in addition to caveolin. The vacuoles or vesicles formed in caveolae (singular caveola) are smaller than those in pinocytosis. Potocytosis is used to bring small molecules into the cell and to transport these molecules through the cell for their release on the other side of the cell, a process called transcytosis. Receptor-mediated Endocytosis 

A targeted variation of endocytosis employs receptor proteins in the plasma membrane that have a specific binding affinity for certain substances ( [link] ). In receptor-mediated endocytosis, uptake of substances by the cell is targeted to a single type of substance that binds to the receptor on the external surface of the cell membrane. (credit: modification of work by Mariana Ruiz Villareal) 

In receptor-mediated endocytosis , as in phagocytosis, clathrin is attached to the cytoplasmic side of the plasma membrane. If uptake of a compound is dependent on receptor-mediated endocytosis and the process is ineffective, the material will not be removed from the tissue fluids or blood. Instead, it will stay in those fluids and increase in concentration. Some human diseases are caused by the failure of receptor-mediated endocytosis. For example, the form of cholesterol termed low-density lipoprotein or LDL (also referred to as bad cholesterol) is removed from the blood by receptor-mediated endocytosis. In the human genetic disease familial hypercholesterolemia, the LDL receptors are defective or missing entirely. People with this condition have life-threatening levels of cholesterol in their blood, because their cells cannot clear LDL particles from their blood. 

Although receptor-mediated endocytosis is designed to bring specific substances that are normally found in the extracellular fluid into the cell, other substances may gain entry into the cell at the same site. Flu viruses, diphtheria, and cholera toxin all have sites that cross-react with normal receptor-binding sites and gain entry into cells. 

See receptor-mediated endocytosis in action, and click on different parts for a focused animation. 

[link] Exocytosis 

The reverse process of moving material into a cell is the process of exocytosis. Exocytosis is the opposite of the processes discussed above in that its purpose is to expel material from the cell into the extracellular fluid. Waste material is enveloped in a membrane and fuses with the interior of the plasma membrane. This fusion opens the membranous envelope on the exterior of the cell, and the waste material is expelled into the extracellular space ( [link] ). Other examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles. In exocytosis, vesicles containing substances fuse with the plasma membrane. The contents are then released to the exterior of the cell. (credit: modification of work by Mariana Ruiz Villareal) Methods of Transport, Energy Requirements, and Types of Material Transported Transport Method Active/Passive Material Transported Diffusion Passive Small-molecular weight material Osmosis Passive Water Facilitated transport/diffusion Passive Sodium, potassium, calcium, glucose Primary active transport Active Sodium, potassium, calcium Secondary active transport Active Amino acids, lactose Phagocytosis Active Large macromolecules, whole cells, or cellular structures Pinocytosis and potocytosis Active Small molecules (liquids/water) Receptor-mediated endocytosis Active Large quantities of macromolecules Section Summary 

Active transport methods require the direct use of ATP to fuel the transport. Large particles, such as macromolecules, parts of cells, or whole cells, can be engulfed by other cells in a process called phagocytosis. In phagocytosis, a portion of the membrane invaginates and flows around the particle, eventually pinching off and leaving the particle entirely enclosed by an envelope of plasma membrane. Vesicle contents are broken down by the cell, with the particles either used as food or dispatched. Pinocytosis is a similar process on a smaller scale. The plasma membrane invaginates and pinches off, producing a small envelope of fluid from outside the cell. Pinocytosis imports substances that the cell needs from the extracellular fluid. The cell expels waste in a similar but reverse manner: it pushes a membranous vacuole to the plasma membrane, allowing the vacuole to fuse with the membrane and incorporate itself into the membrane structure, releasing its contents to the exterior. Review Questions 

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[link] Critical Thinking Questions 

[link] Test Prep for AP Courses 

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[link] Glossary caveolin protein that coats the cytoplasmic side of the plasma membrane and participates in the process of liquid update by potocytosis clathrin protein that coats the inward-facing surface of the plasma membrane and assists in the formation of specialized structures, like coated pits, for phagocytosis endocytosis type of active transport that moves substances, including fluids and particles, into a cell exocytosis process of passing bulk material out of a cell pinocytosis a variation of endocytosis that imports macromolecules that the cell needs from the extracellular fluid potocytosis variation of pinocytosis that uses a different coating protein (caveolin) on the cytoplasmic side of the plasma membrane receptor-mediated endocytosis variation of endocytosis that involves the use of specific binding proteins in the plasma membrane for specific molecules or particles, and clathrin-coated pits that become clathrin-coated vesiclesIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" A hummingbird needs energy to maintain prolonged periods of flight. The bird obtains its energy from taking in food and transforming the nutrients into energy through a series of biochemical reactions. The flight muscles in birds are extremely efficient in energy production. (credit: modification of work by Cory Zanker) 

Virtually every task performed by living organisms requires energy. Energy is needed to perform heavy labor and exercise. Humans also use a great deal of energy while thinking and even during sleep. In fact, the living cells of every organism constantly use energy. Nutrients and other molecules are imported, metabolized (broken down), synthesized into new molecules, modified if needed, transported around the cell, and, in some cases, distributed to the entire organism. For example, the large proteins that make up muscles are actively built from smaller molecules. Complex carbohydrates are broken down into simple sugars that the cell uses for energy. Just as energy is required to both build and demolish a building, energy is required for both the synthesis and breakdown of molecules. Additionally, signaling molecules such as hormones and neurotransmitters are actively transported between cells. Pathogenic bacteria and viruses are ingested and broken down by cells. Cells must also export waste and toxins to stay healthy. Many cells swim or move surrounding materials via the beating motion of cellular appendages such as cilia and flagella. 

All of the cellular processes listed above require a steady supply of energy. From where, and in what form, does this energy come? How do living cells obtain energy and how do they use it? This chapter will discuss different forms of energy and the physical laws that govern energy transfer. 

How enzymes lower the activation energy required to begin a chemical reaction in the body will also be discussed in this chapter. Enzymes are crucial for life; without them the chemical reactions required to survive would not happen fast enough for an organism to survive. For example, in an individual who lacks one of the enzymes needed to break down a type of carbohydrate known as a mucopolysaccharide, waste products accumulate in the cells and cause progressive brain damage. This deadly genetic disease is called Sanfilippo Syndrome type B or Mucopolysaccharidosis III. Previously incurable, scientists have now discovered a way to replace the missing enzyme in the brain of mice. Read more about the scientists research here . 

Metabolism encompasses a wide range of cellular activities, including the need for energy and the elimination of wastes from cells, tissues, and organs.Energy and Metabolism Energy and Metabolism 

In this section, you will explore the following questions: What are metabolic pathways? What are the differences between anabolic and catabolic pathways? How do chemical reactions play a role in energy transfer? Connection for AP Courses 

All living systems, from simple cells to complex ecosystems, require free energy to conduct cell processes such as growth and reproduction. 

Organisms have evolved various strategies to capture, store, transform, and transfer free energy. A cell s metabolism refers to the chemical reactions that occur within it. Some metabolic reactions involve the breaking down of complex molecules into simpler ones with a release of energy (catabolism), whereas other metabolic reactions require energy to build complex molecules (anabolism). A central example of these pathways is the synthesis and breakdown of glucose. 

The content presented in this section supports the Learning Objectives outlined in Big Idea 1 and Big Idea 2 of the AP Biology Curriculum Framework listed below. The AP Learning Objectives merge Essential Knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.14 The student is able to pose scientific questions that correctly identify essential properties of shared, core life processes that provide insight into the history of life on Earth. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 1.16 The student is able to justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction, and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require a constant input of free energy. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.1 The student is able to explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow and to reproduce. 

Starting with the definition of metabolism as the total chemical activity of an organism, ask students for examples of processes that fit. Tally the examples on a board or screen and expand on them as appropriate. 

The concepts of anabolism and catabolism may be difficult to keep straight. Use the example of anabolic steroids as a way (inappropriate and dangerous) to build up the body, therefore, any anabolic process builds macromolecules and the opposite, catabolic, breaks them down. 

Scientists use the term bioenergetics to discuss the concept of energy flow ( [link] ) through living systems, such as cells. Cellular processes such as the building and breaking down of complex molecules occur through stepwise chemical reactions. Some of these chemical reactions are spontaneous and release energy, whereas others require energy to proceed. Just as living things must continually consume food to replenish what has been used, cells must continually produce more energy to replenish that used by the many energy-requiring chemical reactions that constantly take place. All of the chemical reactions that take place inside cells, including those that use energy and those that release energy, are the cell s metabolism . Most life forms on earth get their energy from the sun. Plants use photosynthesis to capture sunlight, and herbivores eat those plants to obtain energy. Carnivores eat the herbivores, and decomposers digest plant and animal matter. Metabolism of Carbohydrates 

The metabolism of sugar (a simple carbohydrate) is a classic example of the many cellular processes that use and produce energy. Living things consume sugar as a major energy source, because sugar molecules have a great deal of energy stored within their bonds. The breakdown of glucose, a simple sugar, is described by the equation: C 6 H 12 O 6 + 6O 2 6 CO 2 + 6H 2 O + energy C 6 H 12 O 6 + 6O 2 6 CO 2 + 6H 2 O + energy size 12{C rSub { size 8{6} } H rSub { size 8{12} } O rSub { size 8{2} } } {} 

Carbohydrates that are consumed have their origins in photosynthesizing organisms like plants ( [link] ). During photosynthesis, plants use the energy of sunlight to convert carbon dioxide gas (CO 2 ) into sugar molecules, like glucose (C 6 H 12 O 6 ). Because this process involves synthesizing a larger, energy-storing molecule, it requires an input of energy to proceed. The synthesis of glucose is described by this equation (notice that it is the reverse of the previous equation): 6CO 2 + 6H 2 O + energy C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy C 6 H 12 O 6 + 6O 2 size 12{C rSub { size 8{6} } H rSub { size 8{12} } O rSub { size 8{2} } } {} 

During the chemical reactions of photosynthesis, energy is provided in the form of a very high-energy molecule called ATP, or adenosine triphosphate, which is the primary energy currency of all cells. Just as the dollar is used as currency to buy goods, cells use molecules of ATP as energy currency to perform immediate work. The sugar (glucose) is stored as starch or glycogen. Energy-storing polymers like these are broken down into glucose to supply molecules of ATP. 

Solar energy is required to synthesize a molecule of glucose during the reactions of photosynthesis. In photosynthesis, light energy from the sun is initially transformed into chemical energy that is temporally stored in the energy carrier molecules ATP and NADPH (nicotinamide adenine dinucleotide phosphate). The stored energy in ATP and NADPH is then used later in photosynthesis to build one molecule of glucose from six molecules of CO 2 . This process is analogous to eating breakfast in the morning to acquire energy for your body that can be used later in the day. Under ideal conditions, energy from 18 molecules of ATP is required to synthesize one molecule of glucose during the reactions of photosynthesis. Glucose molecules can also be combined with and converted into other types of sugars. When sugars are consumed, molecules of glucose eventually make their way into each living cell of the organism. Inside the cell, each sugar molecule is broken down through a complex series of chemical reactions. The goal of these reactions is to harvest the energy stored inside the sugar molecules. The harvested energy is used to make high-energy ATP molecules, which can be used to perform work, powering many chemical reactions in the cell. The amount of energy needed to make one molecule of glucose from six molecules of carbon dioxide is 18 molecules of ATP and 12 molecules of NADPH (each one of which is energetically equivalent to three molecules of ATP), or a total of 54 ATP molecule equivalents required for the synthesis of one molecule of glucose. This process is a fundamental and efficient way for cells to generate the molecular energy that they require. Plants, like this oak tree, use energy from sunlight to make sugar and other organic molecules. Both plants and animals, like this squirrel, use cellular respiration to derive energy from the organic molecules originally produced by plants. 

Ask the students where the energy used for metabolism comes from. Have them trace the energy back to the plants and light energy that the plants convert to sugars. Begin to introduce the interactions between carbohydrate metabolism, lipids, and proteins. Ask them what the ultimate end of the energy is (heat). Metabolic Pathways 

The processes of making and breaking down sugar molecules illustrate two types of metabolic pathways. A metabolic pathway is a series of interconnected biochemical reactions that convert a substrate molecule or molecules, step-by-step, through a series of metabolic intermediates, eventually yielding a final product or products. In the case of sugar metabolism, the first metabolic pathway synthesized sugar from smaller molecules, and the other pathway broke sugar down into smaller molecules. These two opposite processes the first requiring energy and the second producing energy are referred to as anabolic (building) and catabolic (breaking down) pathways, respectively. Consequently, metabolism is composed of building (anabolism) and degradation (catabolism). 

Discuss the evolution of metabolic pathways as they probably developed on Earth. Using the Miller Urey experiment discussed in Chapter 3, ask why there was no free oxygen in an early atmosphere. What pathways could develop under these conditions? How did this limit the development of organisms? What pathway created free oxygen as a waste that could permeate the atmosphere? Is this really a good idea for the organisms that existed? Why? 

This tree shows the evolution of the various branches of life. The vertical dimension is time. Early life forms, in blue, used anaerobic metabolism to obtain energy from their surroundings. 

Evolution of Metabolic Pathways There is more to the complexity of metabolism than understanding the metabolic pathways alone. Metabolic complexity varies from organism to organism. Photosynthesis is the primary pathway in which photosynthetic organisms like plants (the majority of global synthesis is done by planktonic algae) harvest the sun s energy and convert it into carbohydrates. The by-product of photosynthesis is oxygen, required by some cells to carry out cellular respiration. During cellular respiration, oxygen aids in the catabolic breakdown of carbon compounds, like carbohydrates. Among the products of this catabolism are CO 2 and ATP. In addition, some eukaryotes perform catabolic processes without oxygen (fermentation); that is, they perform or use anaerobic metabolism. 

Organisms probably evolved anaerobic metabolism to survive (living organisms came into existence about 3.8 billion years ago, when the atmosphere lacked oxygen). Despite the differences between organisms and the complexity of metabolism, researchers have found that all branches of life share some of the same metabolic pathways, suggesting that all organisms evolved from the same ancient common ancestor ( [link] ). Evidence indicates that over time, the pathways diverged, adding specialized enzymes to allow organisms to better adapt to their environment, thus increasing their chance to survive. However, the underlying principle remains that all organisms must harvest energy from their environment and convert it to ATP to carry out cellular functions. 

[link] Anabolic and Catabolic Pathways 

Anabolic pathways require an input of energy to synthesize complex molecules from simpler ones. Synthesizing sugar from CO 2 is one example. Other examples are the synthesis of large proteins from amino acid building blocks, and the synthesis of new DNA strands from nucleic acid building blocks. These biosynthetic processes are critical to the life of the cell, take place constantly, and demand energy provided by ATP and other high-energy molecules like NADH (nicotinamide adenine dinucleotide) and NADPH ( [link] ). 

ATP is an important molecule for cells to have in sufficient supply at all times. The breakdown of sugars illustrates how a single molecule of glucose can store enough energy to make a great deal of ATP, 36 to 38 molecules. This is a catabolic pathway. Catabolic pathways involve the degradation (or breakdown) of complex molecules into simpler ones. Molecular energy stored in the bonds of complex molecules is released in catabolic pathways and harvested in such a way that it can be used to produce ATP. Other energy-storing molecules, such as fats, are also broken down through similar catabolic reactions to release energy and make ATP ( [link] ). 

It is important to know that the chemical reactions of metabolic pathways don t take place spontaneously. Each reaction step is facilitated, or catalyzed, by a protein called an enzyme. Enzymes are important for catalyzing all types of biological reactions those that require energy as well as those that release energy. Anabolic pathways are those that require energy to synthesize larger molecules. Catabolic pathways are those that generate energy by breaking down larger molecules. Both types of pathways are required for maintaining the cell s energy balance. Think About It 

Describe two different cellular functions in different organisms that require energy that parallel human energy-requiring functions such as physical exercise. 

This question is an application of Learning Objectives1.15 and Science Practice 7.2 because the student is describing how similar energy pathways among different organisms reflect common ancestry. Possible answer: 

Muscles contain the contractile proteins actin and myosin. When these proteins shorten, movement occurs. The same proteins are found in unicellular amoebas that cause the movement of the organism. 

The active transport of sodium and potassium across cell membranes occurs in all multi-celled organisms, including all of the precursors to humans on the evolutionary ladder. Section Summary 

Cells perform the functions of life through various chemical reactions. A cell s metabolism refers to the chemical reactions that take place within it. There are metabolic reactions that involve the breaking down of complex chemicals into simpler ones, such as the breakdown of large macromolecules. This process is referred to as catabolism, and such reactions are associated with a release of energy. On the other end of the spectrum, anabolism refers to metabolic processes that build complex molecules out of simpler ones, such as the synthesis of macromolecules. Anabolic processes require energy. Glucose synthesis and glucose breakdown are examples of anabolic and catabolic pathways, respectively. Review Questions 

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[link] Glossary anabolic (also, anabolism) pathways that require an input of energy to synthesize complex molecules from simpler ones bioenergetics study of energy flowing through living systems catabolic (also, catabolism) pathways in which complex molecules are broken down into simpler ones metabolism all the chemical reactions that take place inside cells, including anabolism and catabolismPotential, Kinetic, Free, and Activation Energy Potential, Kinetic, Free, and Activation Energy 

In this section, you will explore the following questions: What is energy ? What is the difference between kinetic and potential energy? What is free energy, and how does free energy related to activation energy? What is the difference between endergonic and exergonic reactions? Connection for AP Courses 

Although cells and organisms require free energy to survive, they cannot spontaneously create energy, as stated in the Law of Conservation of Energy. Energy is available in different forms. For example, objects in motion possess kinetic energy, whereas objects that are not in motion possess potential energy. The chemical energy in molecules, such as glucose, is potential energy because when bonds break in chemical reactions, free energy is released. Free energy is a measure of energy that is available to do work. The free energy of a system changes during energy transfers such as chemical reactions, and this change is referred to as G or Gibbs free energy. The G of a reaction can be negative or positive, depending on whether the reaction releases energy (exergonic) or requires energy input (endergonic). All reactions require an input of energy called activation energy in order to reach the transition state at which they will proceed. (In another section, we will explore how enzymes speed up chemical reactions by lowering activation energy barriers.) 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A All living systems require constant input of free energy. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.1 The student is able to explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow, and to reproduce. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.2 The student can justify claims with evidence. Learning Objective 2.2 The student is able to justify a scientific claim that free energy is required for living systems to maintain organization, to grow or to reproduce, but that multiple strategies exist in different living systems. 

Energy is defined as the ability to do work. As you ve learned, energy exists in different forms. For example, electrical energy, light energy, and heat energy are all different types of energy. While these are all familiar types of energy that one can see or feel, there is another type of energy that is much less tangible. This energy is associated with something as simple as an object held above the ground. In order to appreciate the way energy flows into and out of biological systems, it is important to understand more about the different types of energy that exist in the physical world. Types of Energy 

When an object is in motion, there is energy associated with that object. In the example of an airplane in flight, there is a great deal of energy associated with the motion of the airplane. This is because moving objects are capable of enacting a change, or doing work. Think of a wrecking ball. Even a slow-moving wrecking ball can do a great deal of damage to other objects. However, a wrecking ball that is not in motion is incapable of performing work. Energy associated with objects in motion is called kinetic energy . A speeding bullet, a walking person, the rapid movement of molecules in the air (which produces heat), and electromagnetic radiation like light all have kinetic energy. 

Now what if that same motionless wrecking ball is lifted two stories above a car with a crane? If the suspended wrecking ball is unmoving, is there energy associated with it? The answer is yes. The suspended wrecking ball has energy associated with it that is fundamentally different from the kinetic energy of objects in motion. This form of energy results from the fact that there is the potential for the wrecking ball to do work. If it is released, indeed it would do work. Because this type of energy refers to the potential to do work, it is called potential energy . Objects transfer their energy between kinetic and potential in the following way: As the wrecking ball hangs motionless, it has 0 kinetic and 100 percent potential energy. Once it is released, its kinetic energy begins to increase because it builds speed due to gravity. At the same time, as it nears the ground, it loses potential energy. Somewhere mid-fall it has 50 percent kinetic and 50 percent potential energy. Just before it hits the ground, the ball has nearly lost its potential energy and has near-maximal kinetic energy. Other examples of potential energy include the energy of water held behind a dam ( [link] ), or a person about to skydive out of an airplane. Water behind a dam has potential energy. Moving water, such as in a waterfall or a rapidly flowing river, has kinetic energy. (credit dam : modification of work by "Pascal"/Flickr; credit waterfall : modification of work by Frank Gualtieri) 

Potential energy is not only associated with the location of matter (such as a child sitting on a tree branch), but also with the structure of matter. A spring on the ground has potential energy if it is compressed; so does a rubber band that is pulled taut. The very existence of living cells relies heavily on structural potential energy. On a chemical level, the bonds that hold the atoms of molecules together have potential energy. Remember that anabolic cellular pathways require energy to synthesize complex molecules from simpler ones, and catabolic pathways release energy when complex molecules are broken down. The fact that energy can be released by the breakdown of certain chemical bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the bonds of all the food molecules we eat, which is eventually harnessed for use. This is because these bonds can release energy when broken. The type of potential energy that exists within chemical bonds, and is released when those bonds are broken, is called chemical energy ( [link] ). Chemical energy is responsible for providing living cells with energy from food. The release of energy is brought about by breaking the molecular bonds within fuel molecules. The molecules in gasoline (octane, the chemical formula shown) contain chemical energy within the chemical bonds. This energy is transformed into kinetic energy that allows a car to race on a racetrack. (credit car : modification of work by Russell Trow) 

Draw examples from the class of potential vs. kinetic energy. Have several prepared before hand. If there are only a few examples given, ask the students which category your examples fall into. Include examples of chemical energy, such as the hand warmers that depend on chemical release of heat, gasoline, and gunpowder. End with the chemical energy in ATP, emphasizing it is a type of potential energy, and its role in metabolism. 

Visit this site and select A simple pendulum on the menu (under Harmonic Motion ) to see the shifting kinetic (K) and potential energy (U) of a pendulum in motion. 

[link] Free Energy 

After learning that chemical reactions release energy when energy-storing bonds are broken, an important next question is how is the energy associated with chemical reactions quantified and expressed? How can the energy released from one reaction be compared to that of another reaction? A measurement of free energy is used to quantitate these energy transfers. Free energy is called Gibbs free energy (abbreviated with the letter G) after Josiah Willard Gibbs, the scientist who developed the measurement. Recall that according to the second law of thermodynamics, all energy transfers involve the loss of some amount of energy in an unusable form such as heat, resulting in entropy. Gibbs free energy specifically refers to the energy associated with a chemical reaction that is available after entropy is accounted for. In other words, Gibbs free energy is usable energy, or energy that is available to do work. 

Every chemical reaction involves a change in free energy, called delta G ( G). The change in free energy can be calculated for any system that undergoes such a change, such as a chemical reaction. To calculate G, subtract the amount of energy lost to entropy (denoted as S) from the total energy change of the system. This total energy change in the system is called enthalpy and is denoted as H . The formula for calculating G is as follows, where the symbol T refers to absolute temperature in Kelvin (degrees Celsius + 273): G = H T S G = H T S 

The standard free energy change of a chemical reaction is expressed as an amount of energy per mole of the reaction product (either in kilojoules or kilocalories, kJ/mol or kcal/mol; 1 kJ = 0.239 kcal) under standard pH, temperature, and pressure conditions. Standard pH, temperature, and pressure conditions are generally calculated at pH 7.0 in biological systems, 25 degrees Celsius, and 100 kilopascals (1 atm pressure), respectively. It is important to note that cellular conditions vary considerably from these standard conditions, and so standard calculated G values for biological reactions will be different inside the cell. Endergonic Reactions and Exergonic Reactions 

If energy is released during a chemical reaction, then the resulting value from the above equation will be a negative number. In other words, reactions that release energy have a G 0. A negative G also means that the products of the reaction have less free energy than the reactants, because they gave off some free energy during the reaction. Reactions that have a negative G and consequently release free energy are called exergonic reactions . Think: ex ergonic means energy is ex iting the system. These reactions are also referred to as spontaneous reactions, because they can occur without the addition of energy into the system. Understanding which chemical reactions are spontaneous and release free energy is extremely useful for biologists, because these reactions can be harnessed to perform work inside the cell. An important distinction must be drawn between the term spontaneous and the idea of a chemical reaction that occurs immediately. Contrary to the everyday use of the term, a spontaneous reaction is not one that suddenly or quickly occurs. The rusting of iron is an example of a spontaneous reaction that occurs slowly, little by little, over time. 

If a chemical reaction requires an input of energy rather than releasing energy, then the G for that reaction will be a positive value. In this case, the products have more free energy than the reactants. Thus, the products of these reactions can be thought of as energy-storing molecules. These chemical reactions are called endergonic reactions , and they are non-spontaneous. An endergonic reaction will not take place on its own without the addition of free energy. 

Let s revisit the example of the synthesis and breakdown of the food molecule, glucose. Remember that the building of complex molecules, such as sugars, from simpler ones is an anabolic process and requires energy. Therefore, the chemical reactions involved in anabolic processes are endergonic reactions. On the other hand, the catabolic process of breaking sugar down into simpler molecules releases energy in a series of exergonic reactions. Like the example of rust above, the breakdown of sugar involves spontaneous reactions, but these reactions don t occur instantaneously. [link] shows some other examples of endergonic and exergonic reactions. Later sections will provide more information about what else is required to make even spontaneous reactions happen more efficiently. 

Shown are some examples of endergonic processes (ones that require energy) and exergonic processes (ones that release energy). These include (a) a compost pile decomposing, (b) a chick hatching from a fertilized egg, (c) sand art being destroyed, and (d) a ball rolling down a hill. (credit a: modification of work by Natalie Maynor; credit b: modification of work by USDA; credit c: modification of work by Athlex /Flickr; credit d: modification of work by Harry Malsch) 

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An important concept in the study of metabolism and energy is that of chemical equilibrium. Most chemical reactions are reversible. They can proceed in both directions, releasing energy into their environment in one direction, and absorbing it from the environment in the other direction ( [link] ). The same is true for the chemical reactions involved in cell metabolism, such as the breaking down and building up of proteins into and from individual amino acids, respectively. Reactants within a closed system will undergo chemical reactions in both directions until a state of equilibrium is reached. This state of equilibrium is one of the lowest possible free energy and a state of maximal entropy. Energy must be put into the system to push the reactants and products away from a state of equilibrium. Either reactants or products must be added, removed, or changed. If a cell were a closed system, its chemical reactions would reach equilibrium, and it would die because there would be insufficient free energy left to perform the work needed to maintain life. In a living cell, chemical reactions are constantly moving towards equilibrium, but never reach it. This is because a living cell is an open system. Materials pass in and out, the cell recycles the products of certain chemical reactions into other reactions, and chemical equilibrium is never reached. In this way, living organisms are in a constant energy-requiring, uphill battle against equilibrium and entropy. This constant supply of energy ultimately comes from sunlight, which is used to produce nutrients in the process of photosynthesis. Exergonic and endergonic reactions result in changes in Gibbs free energy. Exergonic reactions release energy; endergonic reactions require energy to proceed. 

The concept or entropy can be difficult. Have the students survey their neighborhood for houses, sheds, store fronts, any structures that are deteriorating due to lack of maintenance. Also have them identify older homes, buildings that are in good shape and are actively maintained. Activation Energy 

There is another important concept that must be considered regarding endergonic and exergonic reactions. Even exergonic reactions require a small amount of energy input to get going before they can proceed with their energy-releasing steps. These reactions have a net release of energy, but still require some energy in the beginning. This small amount of energy input necessary for all chemical reactions to occur is called the activation energy (or free energy of activation) and is abbreviated E A ( [link] ). 

Why would an energy-releasing, negative G reaction actually require some energy to proceed? The reason lies in the steps that take place during a chemical reaction. During chemical reactions, certain chemical bonds are broken and new ones are formed. For example, when a glucose molecule is broken down, bonds between the carbon atoms of the molecule are broken. Since these are energy-storing bonds, they release energy when broken. However, to get them into a state that allows the bonds to break, the molecule must be somewhat contorted. A small energy input is required to achieve this contorted state. This contorted state is called the transition state , and it is a high-energy, unstable state. For this reason, reactant molecules don t last long in their transition state, but very quickly proceed to the next steps of the chemical reaction. Free energy diagrams illustrate the energy profiles for a given reaction. Whether the reaction is exergonic or endergonic determines whether the products in the diagram will exist at a lower or higher energy state than both the reactants and the products. However, regardless of this measure, the transition state of the reaction exists at a higher energy state than the reactants, and thus, E A is always positive. 

Watch an animation of the move from free energy to transition state at this site. 

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Where does the activation energy required by chemical reactants come from? The source of the activation energy needed to push reactions forward is typically heat energy from the surroundings. Heat energy (the total bond energy of reactants or products in a chemical reaction) speeds up the motion of molecules, increasing the frequency and force with which they collide; it also moves atoms and bonds within the molecule slightly, helping them reach their transition state. For this reason, heating up a system will cause chemical reactants within that system to react more frequently. Increasing the pressure on a system has the same effect. Once reactants have absorbed enough heat energy from their surroundings to reach the transition state, the reaction will proceed. 

The activation energy of a particular reaction determines the rate at which it will proceed. The higher the activation energy, the slower the chemical reaction will be. The example of iron rusting illustrates an inherently slow reaction. This reaction occurs slowly over time because of its high E A . Additionally, the burning of many fuels, which is strongly exergonic, will take place at a negligible rate unless their activation energy is overcome by sufficient heat from a spark. Once they begin to burn, however, the chemical reactions release enough heat to continue the burning process, supplying the activation energy for surrounding fuel molecules. Like these reactions outside of cells, the activation energy for most cellular reactions is too high for heat energy to overcome at efficient rates. In other words, in order for important cellular reactions to occur at appreciable rates (number of reactions per unit time), their activation energies must be lowered ( [link] ); this is referred to as catalysis. This is a very good thing as far as living cells are concerned. Important macromolecules, such as proteins, DNA, and RNA, store considerable energy, and their breakdown is exergonic. If cellular temperatures alone provided enough heat energy for these exergonic reactions to overcome their activation barriers, the essential components of a cell would disintegrate. 

Clearly explain the significance of the activation energy needed for chemical reactions, even with exergonic reactions. Use the figure of exergonic reactions with a delta G less than zero to show that though the change in energy is negative, there still is a need for activation energy. Include examples of ways that enzymes lower the activation energy needed. Emphasize that this is the way enzymes speed up reactions, they make it easier for the reactions to occur. 

Activation energy is the energy required for a reaction to proceed, and it is lower if the reaction is catalyzed. The horizontal axis of this diagram describes the sequence of events in time. 

[link] Think About It 

All plants use water, carbon dioxide, and energy from the sun to make sugars. Think about what would happen to plants that do not have sunlight as an energy source or sufficient water. What would happen to organisms that depend on those plants for their own survival? How does depletion or destruction of forests by human activity affect free energy availability to organisms living in the rain forest? What measures can be taken to try and restore the free energy to an acceptable level? 

This is an application of LO 2.3 and Science Practice 6.4 because students are asked to make a prediction about how a change in free energy availability can affect organisms, populations, and ecosystems. Possible answer: Initially, the loss of trees increases the amount of sunlight available to plants at the ground level. This would increase the amount of free energy available at ground level. The rates of growth of plants would increase due to the increase in free energy available. The increased metabolic rates of plants would eventually deplete soil nutrients leading to a decrease in the number and quality of plants in the area. This would lead to a decrease in free energy as vegetation decreased in both quantity and quality. Section Summary 

Energy comes in many different forms. Objects in motion do physical work, and kinetic energy is the energy of objects in motion. Objects that are not in motion may have the potential to do work, and thus, have potential energy. Molecules also have potential energy because the breaking of molecular bonds has the potential to release energy. Living cells depend on the harvesting of potential energy from molecular bonds to perform work. Free energy is a measure of energy that is available to do work. The free energy of a system changes during energy transfers such as chemical reactions, and this change is referred to as G. 

The G of a reaction can be negative or positive, meaning that the reaction releases energy or consumes energy, respectively. A reaction with a negative G that gives off energy is called an exergonic reaction. One with a positive G that requires energy input is called an endergonic reaction. Exergonic reactions are said to be spontaneous, because their products have less energy than their reactants. The products of endergonic reactions have a higher energy state than the reactants, and so these are nonspontaneous reactions. However, all reactions (including spontaneous G reactions) require an initial input of energy in order to reach the transition state, at which they ll proceed. This initial input of energy is called the activation energy. Review Questions 

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[link] Glossary activation energy energy necessary for reactions to occur chemical energy potential energy in chemical bonds that is released when those bonds are broken endergonic describes chemical reactions that require energy input enthalpy total energy of a system exergonic describes chemical reactions that release free energy free energy Gibbs free energy is the usable energy, or energy that is available to do work. heat energy total bond energy of reactants or products in a chemical reaction kinetic energy type of energy associated with objects or particles in motion potential energy type of energy that has the potential to do work; stored energy transition state high-energy, unstable state (an intermediate form between the substrate and the product) occurring during a chemical reactionThe Laws of Thermodynamics The Laws of Thermodynamics 

In this section, you will explore the following questions: What is entropy? What is the difference between the first and second laws of thermodynamics? Connection for AP Courses 

In studying energy, scientists use the term system to refer to the matter and its environment involved in energy transfers, such as an ecosystem. Even single cells are biological systems and all systems require energy to maintain order. The more ordered a system is, the lower its entropy. Entropy is a measure of the disorder of the system. (Think of your bedroom as a system. On Sunday evening, you throw dirty clothes in the laundry basket, put books back on the shelves, and return dirty dishes to the kitchen. Cleaning your room requires an input of energy. What gradually happens as the week progresses? You guessed it: entropy.) All biological systems obey the laws of chemistry and physics, including the laws of thermodynamics that describe the properties and processes of energy transfer in systems. The first law states that the total amount of energy in the universe is constant; energy cannot be created or destroyed, but it can be transformed and transferred. The second law states that every energy transfer involves some loss of energy in an unusable form, such as heat energy, resulting in a more disordered system (e.g., your bedroom over the course of a week). Thus, no energy transfer is completely efficient. (We will explore how free energy is stored, transferred, and used in more detail when we study photosynthesis and cellular respiration.) 

Information presented and the examples highlighted in the section, support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.1 The student is able to explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow, and to reproduce. 

Use the survey that the students conducted previously of their neighborhoods, or town and have them determine the amount of energy (expressed as cost) it would take to repair one example, or bring it back to order . The money is the energy going into the repairs, the materials are what will go directly into the repair and the overhead can be analogous to money that is lost in the process. In a chemical reaction with energy transfer, this overhead is the lost energy expressed as heat. 

Thermodynamics refers to the study of energy and energy transfer involving physical matter. The matter and its environment relevant to a particular case of energy transfer are classified as a system, and everything outside of that system is called the surroundings. For instance, when heating a pot of water on the stove, the system includes the stove, the pot, and the water. Energy is transferred within the system (between the stove, pot, and water). There are two types of systems: open and closed. An open system is one in which energy can be transferred between the system and its surroundings. The stovetop system is open because heat can be lost into the air. A closed system is one that cannot transfer energy to its surroundings. 

Biological organisms are open systems. Energy is exchanged between them and their surroundings, as they consume energy-storing molecules and release energy to the environment by doing work. Like all things in the physical world, energy is subject to the laws of physics. The laws of thermodynamics govern the transfer of energy in and among all systems in the universe. The First Law of Thermodynamics 

The first law of thermodynamics deals with the total amount of energy in the universe. It states that this total amount of energy is constant. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight into the chemical energy stored within organic molecules, as shown in this figure . Some examples of energy transformations are shown in [link] . 

The challenge for all living organisms is to obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work. Living cells have evolved to meet this challenge very well. Chemical energy stored within organic molecules such as sugars and fats is transformed through a series of cellular chemical reactions into energy within molecules of ATP. Energy in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do include building complex molecules, transporting materials, powering the beating motion of cilia or flagella, contracting muscle fibers to create movement, and reproduction. Shown are two examples of energy being transferred from one system to another and transformed from one form to another. Humans can convert the chemical energy in food, like this ice cream cone, into kinetic energy (the energy of movement to ride a bicycle). Plants can convert electromagnetic radiation (light energy) from the sun into chemical energy. (credit ice cream : modification of work by D. Sharon Pruitt; credit kids on bikes : modification of work by Michelle Riggen-Ransom; credit leaf : modification of work by Cory Zanker) The Second Law of Thermodynamics 

A living cell s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers we ve discussed, along with all energy transfers and transformations in the universe, is completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that is not doing work. For example, when an airplane flies through the air, some of the energy of the flying plane is lost as heat energy due to friction with the surrounding air. This friction actually heats the air by temporarily increasing the speed of air molecules. Likewise, some energy is lost as heat energy during cellular metabolic reactions. This is good for warm-blooded creatures like us, because heat energy helps to maintain our body temperature. Strictly speaking, no energy transfer is completely efficient, because some energy is lost in an unusable form. 

An important concept in physical systems is that of order and disorder (also known as randomness). The more energy that is lost by a system to its surroundings, the less ordered and more random the system is. Scientists refer to the measure of randomness or disorder within a system as entropy . High entropy means high disorder and low energy ( [link] ). To better understand entropy, think of a student s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be put into the system, in the form of the student doing work and putting everything away, in order to bring the room back to a state of cleanliness and order. This state is one of low entropy. Similarly, a car or house must be constantly maintained with work in order to keep it in an ordered state. Left alone, the entropy of the house or car gradually increases through rust and degradation. Molecules and chemical reactions have varying amounts of entropy as well. For example, as chemical reactions reach a state of equilibrium, entropy increases, and as molecules at a high concentration in one place diffuse and spread out, entropy also increases. Scientific Connection Transfer of Energy and the Resulting Entropy 

Set up a simple experiment to understand how energy is transferred and how a change in entropy results. Take a block of ice. This is water in solid form, so it has a high structural order. This means that the molecules cannot move very much and are in a fixed position. The temperature of the ice is 0 C. As a result, the entropy of the system is low. Allow the ice to melt at room temperature. What is the state of molecules in the liquid water now? How did the energy transfer take place? Is the entropy of the system higher or lower? Why? Heat the water to its boiling point. What happens to the entropy of the system when the water is heated? 

All physical systems can be thought of in this way: Living things are highly ordered, requiring constant energy input to be maintained in a state of low entropy. As living systems take in energy-storing molecules and transform them through chemical reactions, they lose some amount of usable energy in the process, because no reaction is completely efficient. They also produce waste and by-products that aren t useful energy sources. This process increases the entropy of the system s surroundings. Since all energy transfers result in the loss of some usable energy, the second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe. Even though living things are highly ordered and maintain a state of low entropy, the entropy of the universe in total is constantly increasing due to the loss of usable energy with each energy transfer that occurs. Essentially, living things are in a continuous uphill battle against this constant increase in universal entropy. Entropy is a measure of randomness or disorder in a system. Gases have higher entropy than liquids, and liquids have higher entropy than solids. Think About It Imagine a large ant colony with an elaborate nest, containing many tunnels and passageways. Now imagine that an earthquake shakes the ground and demolishes the nest. Did the ant nest have higher entropy before or after the earthquake? What can the ants do to restore their nest to close to its original amount of entropy? Explain your answers. Energy transfers take place constantly in everyday activities. Think of two scenarios: cooking on a stove and driving a car. Explain how the second law of thermodynamics applies to these two scenarios. 

Both questions below are an application of Learning Objectives 2.1 and science practice 6.2 because students are explaining how systems use free energy and how entropy reduces the amount of energy available to the system. Possible answers: 

The ant farm is in a state of higher entropy or disorder after the earthquake. The tunnels have been destroyed and energy must be spent to rebuild them. 

Energy transfers take place constantly in everyday activities. Think of two scenarios: cooking on a stove and driving a car. Explain how the second law of thermodynamics applies to these two scenarios. 

In both examples there is an input of energy that results in work being done, cooking and moving the car, and the loss of heat as a result. The heat loss travels into the room on cooking and into the metal of the engine on gasoline combustion. Energy must be continuously put into the systems in order to maintain the activities. Run out of natural gas or propane and the cooking stops. Run out of gasoline and the car stops. Section Summary 

In studying energy, scientists use the term system to refer to the matter and its environment involved in energy transfers. Everything outside of the system is called the surroundings. Single cells are biological systems. Systems can be thought of as having a certain amount of order. It takes energy to make a system more ordered. The more ordered a system is, the lower its entropy. Entropy is a measure of the disorder of a system. As a system becomes more disordered, the lower its energy and the higher its entropy become. 

A series of laws, called the laws of thermodynamics, describe the properties and processes of energy transfer. The first law states that the total amount of energy in the universe is constant. This means that energy can t be created or destroyed, only transferred or transformed. The second law of thermodynamics states that every energy transfer involves some loss of energy in an unusable form, such as heat energy, resulting in a more disordered system. In other words, no energy transfer is completely efficient and tends toward disorder. Review Questions 

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[link] Glossary entropy (S) measure of randomness or disorder within a system heat energy energy transferred from one system to another that is not work (energy of the motion of molecules or particles) thermodynamics study of energy and energy transfer involving physical matterATP: Adenosine Triphosphate ATP: Adenosine Triphosphate 

In this section, you will explore the following questions: Why is ATP considered the energy currency of the cell? How is energy released through the hydrolysis of ATP? Connection for AP Courses 

Adenosine triphosphate or ATP is the energy currency or carrier of the cell. When cells require an input of energy, they use ATP. An ATP nucleotide molecule consists of a five-carbon sugar, the nitrogenous base adenine, and three phosphate groups. (Do not confuse ATP with the nucleotides of DNA and RNA, although they have structural similarities.) The bonds that connect the phosphate have high-energy content, and the energy released from the hydrolysis of ATP to ADP + P i (Adenosine Diphosphate + Pyrophosphate) is used to perform cellular work, such as contracting a muscle or pumping a solute across a cell membrane in active transport. Cells use ATP by coupling the exergonic reaction of ATP hydrolysis with endergonic reactions, with ATP donating its phosphate group to another molecule via a process called phosphorylation. The phosphorylated molecule is at a higher energy state and is less stable than its unphosphorylated form and free energy is released to substrates to perform work during this process. Phosphorylation is an example of energy transfer between molecules. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.1 The student is able to explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow, and to reproduce. 

It is easy to say that ATP carries energy and transfers it to chemicals to fuel reactions. The hard part is in answering the question, how? All three phosphates are negatively charged and naturally repel each other. Energy is needed to keep them together. Line them up and the repelling forces increase and makes it difficult to get the third phosphate attached. This requires much more energy and creates an unstable bond. Energy is stored in this easily broken bond and can be passed on when the third phosphate is used to phosphorylate another compound. It brings the energy with it and losses some in the transfer, creating wasted energy as heat. 

Even exergonic, energy-releasing reactions require a small amount of activation energy in order to proceed. However, consider endergonic reactions, which require much more energy input, because their products have more free energy than their reactants. Within the cell, where does energy to power such reactions come from? The answer lies with an energy-supplying molecule called adenosine triphosphate , or ATP . ATP is a small, relatively simple molecule ( [link] ), but within some of its bonds, it contains the potential for a quick burst of energy that can be harnessed to perform cellular work. This molecule can be thought of as the primary energy currency of cells in much the same way that money is the currency that people exchange for things they need. ATP is used to power the majority of energy-requiring cellular reactions. ATP is the primary energy currency of the cell. It has an adenosine backbone with three phosphate groups attached. 

[link] is useful in illustrating the structure of ATP and why it is easy to detach the gamma phosphate that is hanging out at the end of the structure. [link] is useful in illustrating the use of ATP in the sodium-potassium pump that is in every cell membrane. 

As its name suggests, adenosine triphosphate is comprised of adenosine bound to three phosphate groups ( [link] ). Adenosine is a nucleoside consisting of the nitrogenous base adenine and a five-carbon sugar, ribose. The three phosphate groups, in order of closest to furthest from the ribose sugar, are labeled alpha, beta, and gamma. Together, these chemical groups constitute an energy powerhouse. However, not all bonds within this molecule exist in a particularly high-energy state. Both bonds that link the phosphates are equally high-energy bonds ( phosphoanhydride bonds ) that, when broken, release sufficient energy to power a variety of cellular reactions and processes. These high-energy bonds are the bonds between the second and third (or beta and gamma) phosphate groups and between the first and second phosphate groups. The reason that these bonds are considered high-energy is because the products of such bond breaking adenosine diphosphate (ADP) and one inorganic phosphate group (P i ) have considerably lower free energy than the reactants: ATP and a water molecule. Because this reaction takes place with the use of a water molecule, it is considered a hydrolysis reaction. In other words, ATP is hydrolyzed into ADP in the following reaction: ATP + H 2 O ADP + P i + free energy ATP + H 2 O ADP + P i + free energy size 12{{ATP} + H rSub { size 8{2} } O ADP + P rSub { size 8{i}} + {free energy} } {} 

Like most chemical reactions, the hydrolysis of ATP to ADP is reversible. The reverse reaction regenerates ATP from ADP + P i . Indeed, cells rely on the regeneration of ATP just as people rely on the regeneration of spent money through some sort of income. Since ATP hydrolysis releases energy, ATP regeneration must require an input of free energy. The formation of ATP is expressed in this equation: ADP + P i + free energy ATP + H 2 O ADP + P i + free energy ATP + H 2 O size 12{{ATP} + H rSub { size 8{2} } O ADP + P rSub { size 8{i}} + {free energy} } {} 

Two prominent questions remain with regard to the use of ATP as an energy source. Exactly how much free energy is released with the hydrolysis of ATP, and how is that free energy used to do cellular work? The calculated G for the hydrolysis of one mole of ATP into ADP and P i is 7.3 kcal/mole ( 30.5 kJ/mol). Since this calculation is true under standard conditions, it would be expected that a different value exists under cellular conditions. In fact, the G for the hydrolysis of one mole of ATP in a living cell is almost double the value at standard conditions: 14 kcal/mol ( 57 kJ/mol). 

ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP + P i , and the free energy released during this process is lost as heat. The second question posed above, that is, how the energy released by ATP hydrolysis is used to perform work inside the cell, depends on a strategy called energy coupling. Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions, allowing them to proceed. One example of energy coupling using ATP involves a transmembrane ion pump that is extremely important for cellular function. This sodium-potassium pump (Na + /K + pump) drives sodium out of the cell and potassium into the cell ( [link] ). A large percentage of a cell s ATP is spent powering this pump, because cellular processes bring a great deal of sodium into the cell and potassium out of the cell. The pump works constantly to stabilize cellular concentrations of sodium and potassium. In order for the pump to turn one cycle (exporting three Na+ ions and importing two K + ions), one molecule of ATP must be hydrolyzed. When ATP is hydrolyzed, its gamma phosphate doesn t simply float away, but is actually transferred onto the pump protein. This process of a phosphate group binding to a molecule is called phosphorylation. As with most cases of ATP hydrolysis, a phosphate from ATP is transferred onto another molecule. In a phosphorylated state, the Na + /K + pump has more free energy and is triggered to undergo a conformational change. This change allows it to release Na + to the outside of the cell. It then binds extracellular K + , which, through another conformational change, causes the phosphate to detach from the pump. This release of phosphate triggers the K + to be released to the inside of the cell. Essentially, the energy released from the hydrolysis of ATP is coupled with the energy required to power the pump and transport Na + and K + ions. ATP performs cellular work using this basic form of energy coupling through phosphorylation. 

The sodium-potassium pump is an example of energy coupling. The energy derived from exergonic ATP hydrolysis is used to pump sodium and potassium ions across the cell membrane. 

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Often during cellular metabolic reactions, such as the synthesis and breakdown of nutrients, certain molecules must be altered slightly in their conformation to become substrates for the next step in the reaction series. One example is during the very first steps of cellular respiration, when a molecule of the sugar glucose is broken down in the process of glycolysis. In the first step of this process, ATP is required for the phosphorylation of glucose, creating a high-energy but unstable intermediate. This phosphorylation reaction powers a conformational change that allows the phosphorylated glucose molecule to be converted to the phosphorylated sugar fructose. Fructose is a necessary intermediate for glycolysis to move forward. Here, the exergonic reaction of ATP hydrolysis is coupled with the endergonic reaction of converting glucose into a phosphorylated intermediate in the pathway. Once again, the energy released by breaking a phosphate bond within ATP was used for the phosphorylation of another molecule, creating an unstable intermediate and powering an important conformational change. 

See an interactive animation of the ATP-producing glycolysis process at this site . 

[link] Think About It 

The hydrolysis of one ATP molecules releases 7.3 kcal/mol of energy ( G = 7.3 kcal/mol energy). If it takes 2.1 kcal/mol of energy to move one Na + across the membrane ( G = +2.1 kcal/mol of energy), how many sodium ions could be moved by the hydrolysis of one ATP molecule? 

This question is an application of Learning Objective 2.1 and Science Practice 6.2 because students are explaining how a biological system uses free energy. The question also allows you to apply quantitative skills. Possible answer: 7.3 divided by 2.1 equals 3.476, so three sodium ions can be moved across the membrane with a loss of 0.476 kcal/mol of energy. Section Summary 

ATP is the primary energy-supplying molecule for living cells. ATP is made up of a nucleotide, a five-carbon sugar, and three phosphate groups. The bonds that connect the phosphates (phosphoanhydride bonds) have high-energy content. The energy released from the hydrolysis of ATP into ADP + P i is used to perform cellular work. Cells use ATP to perform work by coupling the exergonic reaction of ATP hydrolysis with endergonic reactions. ATP donates its phosphate group to another molecule via a process known as phosphorylation. The phosphorylated molecule is at a higher-energy state and is less stable than its unphosphorylated form, and this added energy from the addition of the phosphate allows the molecule to undergo its endergonic reaction. Review Questions 

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[link] Glossary ATP adenosine triphosphate, the cell s energy currency phosphoanhydride bond bond that connects phosphates in an ATP moleculeEnzymes Enzymes 

In this section, you will explore the following questions: What is the role of enzymes in metabolic pathways? How do enzymes function as molecular catalysts? Connection for AP Courses 

Many chemical reactions in cells occur spontaneously, but happen too slowly to meet the needs of a cell. For example, a teaspoon of sucrose (table sugar), a disaccharide, in a glass of iced tea will take time to break down into two monosaccharides, glucose and fructose; however, if you add a small amount of the enzyme sucrase to the tea, sucrose breaks down almost immediately. Sucrase is an example of an enzyme, a type of biological catalyst. Enzymes are macromolecules most often proteins that speed up chemical reactions by lowering activation energy barriers. Enzymes are very specific for the reactions they catalyze; because they are polypeptides, enzymes can have a variety of shapes attributed to interactions among amino acid R-groups. One part of the enzyme, the active site, interacts with the substrate via the induced fit model of interaction. Substrate binding alters the shape of the enzyme to facilitate the chemical reaction in several different ways, including bringing substrates together in an optimal orientation. After the reaction finishes, the product(s) are released, and the active site returns to its original shape. 

Enzyme activity, and thus the rate of an enzyme-catalyzed reaction, is regulated by environmental conditions, including the amount of substrate, temperature, pH, and the presence of coenzymes, cofactors, activators, and inhibitors. Inhibitors, coenzymes, and cofactors can act competitively by binding to the enzyme s active site, or noncompetitively by binding to the enzyme s allosteric site. An allosteric site is an alternate part of the enzyme that can bind to non substrate molecules. Enzymes work most efficiently under optimal conditions that are specific to the enzyme. For example, trypsin, an enzyme in the human small intestine, works most efficiently at pH 8, whereas pepsin in the stomach works best under acidic conditions. Sometimes environmental factors, especially low pH and high temperatures, alter the shape of the active site; if the shape cannot be restored, the enzyme denatures. The most common method of enzyme regulation in metabolic pathways is via feedback inhibition. 

How can various factors, such as feedback inhibition, regulate enzyme activity? 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 4 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven science practices. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.B Competition and cooperation are important aspects of biological systems. Essential Knowledge 4.B.1 Interactions between molecules affect their structure and function. Science Practice 5.1 The student can analyze data to identify patterns or relationships. Learning Objective 4.17 The student is able to analyze data to identify how molecular interactions affect structure and function. 

The idea that enzymes help chemical reactions to occur, but do not take part in the chemical reaction and are not changed by it can be confusing. Stress that an enzyme and substrate do not covalently bind to each other and the association is temporary. [link] is useful in illustrating enzyme function. If two compounds are to be joined into one during the reaction, and they would anyway if left alone long enough, the enzyme molecule brings them close enough for the reaction to occur faster. If a large molecule is to be split into smaller units, the enzyme stresses the molecule and makes it easier for the covalent bonds holding the molecule to break. In both cases, the enzyme molecule subtlety changes its shape after attaching to the substrate (s). This creates an intermediate phase of the reaction and an enzyme-substrate complex. When the reaction is complete and the product(s) disassociate, the enzyme returns to its original shape. 

A substance that helps a chemical reaction to occur is a catalyst, and the special molecules that catalyze biochemical reactions are called enzymes. Almost all enzymes are proteins, made up of chains of amino acids, and they perform the critical task of lowering the activation energies of chemical reactions inside the cell. Enzymes do this by binding to the reactant molecules, and holding them in such a way as to make the chemical bond-breaking and bond-forming processes take place more readily. It is important to remember that enzymes don t change the G of a reaction. In other words, they don t change whether a reaction is exergonic (spontaneous) or endergonic. This is because they don t change the free energy of the reactants or products. They only reduce the activation energy required to reach the transition state ( [link] ). Enzymes lower the activation energy of the reaction but do not change the free energy of the reaction. Enzyme Active Site and Substrate Specificity 

The chemical reactants to which an enzyme binds are the enzyme s substrates . There may be one or more substrates, depending on the particular chemical reaction. In some reactions, a single-reactant substrate is broken down into multiple products. In others, two substrates may come together to create one larger molecule. Two reactants might also enter a reaction, both become modified, and leave the reaction as two products. The location within the enzyme where the substrate binds is called the enzyme s active site . The active site is where the action happens, so to speak. Since enzymes are proteins, there is a unique combination of amino acid residues (also called side chains, or R groups) within the active site. Each residue is characterized by different properties. Residues can be large or small, weakly acidic or basic, hydrophilic or hydrophobic, positively or negatively charged, or neutral. The unique combination of amino acid residues, their positions, sequences, structures, and properties, creates a very specific chemical environment within the active site. This specific environment is suited to bind, albeit briefly, to a specific chemical substrate (or substrates). Due to this jigsaw puzzle-like match between an enzyme and its substrates (which adapts to find the best fit between the transition state and the active site), enzymes are known for their specificity. The best fit results from the shape and the amino acid functional group s attraction to the substrate. There is a specifically matched enzyme for each substrate and, thus, for each chemical reaction; however, there is flexibility as well. 

The fact that active sites are so perfectly suited to provide specific environmental conditions also means that they are subject to influences by the local environment. It is true that increasing the environmental temperature generally increases reaction rates, enzyme-catalyzed or otherwise. However, increasing or decreasing the temperature outside of an optimal range can affect chemical bonds within the active site in such a way that they are less well suited to bind substrates. High temperatures will eventually cause enzymes, like other biological molecules, to denature , a process that changes the natural properties of a substance. Likewise, the pH of the local environment can also affect enzyme function. Active site amino acid residues have their own acidic or basic properties that are optimal for catalysis. These residues are sensitive to changes in pH that can impair the way substrate molecules bind. Enzymes are suited to function best within a certain pH range, and, as with temperature, extreme pH values (acidic or basic) of the environment can cause enzymes to denature. Induced Fit and Enzyme Function 

For many years, scientists thought that enzyme-substrate binding took place in a simple lock-and-key fashion. This model asserted that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view called induced fit ( [link] ). The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild shift in the enzyme s structure that confirms an ideal binding arrangement between the enzyme and the transition state of the substrate. This ideal binding maximizes the enzyme s ability to catalyze its reaction. 

View an animation of induced fit at this website . 

[link] 

When an enzyme binds its substrate, an enzyme-substrate complex is formed. This complex lowers the activation energy of the reaction and promotes its rapid progression in one of many ways. On a basic level, enzymes promote chemical reactions that involve more than one substrate by bringing the substrates together in an optimal orientation. The appropriate region (atoms and bonds) of one molecule is juxtaposed to the appropriate region of the other molecule with which it must react. Another way in which enzymes promote the reaction of their substrates is by creating an optimal environment within the active site for the reaction to occur. Certain chemical reactions might proceed best in a slightly acidic or non-polar environment. The chemical properties that emerge from the particular arrangement of amino acid residues within an active site create the perfect environment for an enzyme s specific substrates to react. 

You ve learned that the activation energy required for many reactions includes the energy involved in manipulating or slightly contorting chemical bonds so that they can easily break and allow others to reform. Enzymatic action can aid this process. The enzyme-substrate complex can lower the activation energy by contorting substrate molecules in such a way as to facilitate bond-breaking, helping to reach the transition state. Finally, enzymes can also lower activation energies by taking part in the chemical reaction itself. The amino acid residues can provide certain ions or chemical groups that actually form covalent bonds with substrate molecules as a necessary step of the reaction process. In these cases, it is important to remember that the enzyme will always return to its original state at the completion of the reaction. One of the hallmark properties of enzymes is that they remain ultimately unchanged by the reactions they catalyze. After an enzyme is done catalyzing a reaction, it releases its product(s). According to the induced-fit model, both enzyme and substrate undergo dynamic conformational changes upon binding. The enzyme contorts the substrate into its transition state, thereby increasing the rate of the reaction. Activity 

AP Biology Investigation 13: Enzyme Activity. This investigation allows you to design and conduct experiments to explore the effects of environmental variables, such as temperature and pH, on the rates of enzymatic reactions. 

This lab investigation is an application of LO 4.17 and Science Practice 5.1 because you will analyze experimental data to determine how various environment conditions affect enzyme structure and function and, thus, the rate of enzyme-catalyzed reactions. 

An expanded lab investigation for enzymes, involving determining the effect of pH on the action of turnip peroxidase, is available from the College Board s AP Biology Investigative Labs: An Inquiry-Based Approach , Investigation 13 . Control of Metabolism Through Enzyme Regulation 

It would seem ideal to have a scenario in which all of the enzymes encoded in an organism s genome existed in abundant supply and functioned optimally under all cellular conditions, in all cells, at all times. In reality, this is far from the case. A variety of mechanisms ensure that this does not happen. Cellular needs and conditions vary from cell to cell, and change within individual cells over time. The required enzymes and energetic demands of stomach cells are different from those of fat storage cells, skin cells, blood cells, and nerve cells. Furthermore, a digestive cell works much harder to process and break down nutrients during the time that closely follows a meal compared with many hours after a meal. As these cellular demands and conditions vary, so do the amounts and functionality of different enzymes. 

Since the rates of biochemical reactions are controlled by activation energy, and enzymes lower and determine activation energies for chemical reactions, the relative amounts and functioning of the variety of enzymes within a cell ultimately determine which reactions will proceed and at which rates. This determination is tightly controlled. In certain cellular environments, enzyme activity is partly controlled by environmental factors, like pH and temperature. There are other mechanisms through which cells control the activity of enzymes and determine the rates at which various biochemical reactions will occur. Regulation of Enzymes by Molecules 

Enzymes can be regulated in ways that either promote or reduce their activity. There are many different kinds of molecules that inhibit or promote enzyme function, and various mechanisms exist for doing so. In some cases of enzyme inhibition, for example, an inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding. When this happens, the enzyme is inhibited through competitive inhibition , because an inhibitor molecule competes with the substrate for active site binding ( [link] ). On the other hand, in noncompetitive inhibition, an inhibitor molecule binds to the enzyme in a location other than an allosteric site and still manages to block substrate binding to the active site. Competitive and noncompetitive inhibition affect the rate of reaction differently. Competitive inhibitors affect the initial rate but do not affect the maximal rate, whereas noncompetitive inhibitors affect the maximal rate. 

Some inhibitor molecules bind to enzymes in a location where their binding induces a conformational change that reduces the affinity of the enzyme for its substrate. This type of inhibition is called allosteric inhibition ( [link] ). Most allosterically regulated enzymes are made up of more than one polypeptide, meaning that they have more than one protein subunit. When an allosteric inhibitor binds to an enzyme, all active sites on the protein subunits are changed slightly such that they bind their substrates with less efficiency. There are allosteric activators as well as inhibitors. Allosteric activators bind to locations on an enzyme away from the active site, inducing a conformational change that increases the affinity of the enzyme s active site(s) for its substrate(s). Allosteric inhibitors modify the active site of the enzyme so that substrate binding is reduced or prevented. In contrast, allosteric activators modify the active site of the enzyme so that the affinity for the substrate increases. Have you ever wondered how pharmaceutical drugs are developed? (credit: Deborah Austin) 

Drug Discovery by Looking for Inhibitors of Key Enzymes in Specific Pathways Enzymes are key components of metabolic pathways. Understanding how enzymes work and how they can be regulated is a key principle behind the development of many of the pharmaceutical drugs ( [link] ) on the market today. Biologists working in this field collaborate with other scientists, usually chemists, to design drugs. 

Consider statins for example which is the name given to the class of drugs that reduces cholesterol levels. These compounds are essentially inhibitors of the enzyme HMG-CoA reductase. HMG-CoA reductase is the enzyme that synthesizes cholesterol from lipids in the body. By inhibiting this enzyme, the levels of cholesterol synthesized in the body can be reduced. Similarly, acetaminophen, popularly marketed under the brand name Tylenol, is an inhibitor of the enzyme cyclooxygenase. While it is effective in providing relief from fever and inflammation (pain), its mechanism of action is still not completely understood. 

How are drugs developed? One of the first challenges in drug development is identifying the specific molecule that the drug is intended to target. In the case of statins, HMG-CoA reductase is the drug target. Drug targets are identified through painstaking research in the laboratory. Identifying the target alone is not sufficient; scientists also need to know how the target acts inside the cell and which reactions go awry in the case of disease. Once the target and the pathway are identified, then the actual process of drug design begins. During this stage, chemists and biologists work together to design and synthesize molecules that can either block or activate a particular reaction. However, this is only the beginning: both if and when a drug prototype is successful in performing its function, then it must undergo many tests from in vitro experiments to clinical trials before it can get FDA approval to be on the market. 

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Many enzymes don t work optimally, or even at all, unless bound to other specific non-protein helper molecules, either temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds. Two types of helper molecules are cofactors and coenzymes . Binding to these molecules promotes optimal conformation and function for their respective enzymes. Cofactors are inorganic ions such as iron (Fe++) and magnesium (Mg++). One example of an enzyme that requires a metal ion as a cofactor is the enzyme that builds DNA molecules, DNA polymerase, which requires bound zinc ion (Zn++) to function. Coenzymes are organic helper molecules, with a basic atomic structure made up of carbon and hydrogen, which are required for enzyme action. The most common sources of coenzymes are dietary vitamins ( [link] ). Some vitamins are precursors to coenzymes and others act directly as coenzymes. Vitamin C is a coenzyme for multiple enzymes that take part in building the important connective tissue component, collagen. An important step in the breakdown of glucose to yield energy is catalysis by a multi-enzyme complex called pyruvate dehydrogenase. Pyruvate dehydrogenase is a complex of several enzymes that actually requires one cofactor (a magnesium ion) and five different organic coenzymes to catalyze its specific chemical reaction. Therefore, enzyme function is, in part, regulated by an abundance of various cofactors and coenzymes, which are supplied primarily by the diets of most organisms. Vitamins are important coenzymes or precursors of coenzymes, and are required for enzymes to function properly. Multivitamin capsules usually contain mixtures of all the vitamins at different percentages. Enzyme Compartmentalization 

In eukaryotic cells, molecules such as enzymes are usually compartmentalized into different organelles. This allows for yet another level of regulation of enzyme activity. Enzymes required only for certain cellular processes can be housed separately along with their substrates, allowing for more efficient chemical reactions. Examples of this sort of enzyme regulation based on location and proximity include the enzymes involved in the latter stages of cellular respiration, which take place exclusively in the mitochondria, and the enzymes involved in the digestion of cellular debris and foreign materials, located within lysosomes. Feedback Inhibition in Metabolic Pathways 

Molecules can regulate enzyme function in many ways. A major question remains, however: What are these molecules and where do they come from? Some are cofactors and coenzymes, ions, and organic molecules, as you ve learned. What other molecules in the cell provide enzymatic regulation, such as allosteric modulation, and competitive and noncompetitive inhibition? The answer is that a wide variety of molecules can perform these roles. Some of these molecules include pharmaceutical and non-pharmaceutical drugs, toxins, and poisons from the environment. Perhaps the most relevant sources of enzyme regulatory molecules, with respect to cellular metabolism, are the products of the cellular metabolic reactions themselves. In a most efficient and elegant way, cells have evolved to use the products of their own reactions for feedback inhibition of enzyme activity. Feedback inhibition involves the use of a reaction product to regulate its own further production ( [link] ). The cell responds to the abundance of specific products by slowing down production during anabolic or catabolic reactions. Such reaction products may inhibit the enzymes that catalyzed their production through the mechanisms described above. Metabolic pathways are a series of reactions catalyzed by multiple enzymes. Feedback inhibition, where the end product of the pathway inhibits an upstream step, is an important regulatory mechanism in cells. 

The production of both amino acids and nucleotides is controlled through feedback inhibition. Additionally, ATP is an allosteric regulator of some of the enzymes involved in the catabolic breakdown of sugar, the process that produces ATP. In this way, when ATP is abundant, the cell can prevent its further production. Remember that ATP is an unstable molecule that can spontaneously dissociate into ADP. If too much ATP were present in a cell, much of it would go to waste. On the other hand, ADP serves as a positive allosteric regulator (an allosteric activator) for some of the same enzymes that are inhibited by ATP. Thus, when relative levels of ADP are high compared to ATP, the cell is triggered to produce more ATP through the catabolism of sugar. 

Ask students which inhibition is more effective at slowing or limiting the reaction? Relate this to the examples available and discuss why these would be used in specific instances. 

Have the class research antimicrobial treatments that are based on enzyme inhibition, not on the administration of traditional antibiotics. 

Enzymes are not changed by the chemicals they facilitate; therefore, they can be used repeatedly. Yet, how do you keep them from catalyzing reactions when you do not need or want them to react anymore? If enzymes could not be controlled, the reactions would continue until the substrates were depleted, which is not a good situation for a living organism. Competitive and noncompetitive inhibition explains the control of enzyme activity. Research several examples of both in living organisms and explain why they are necessary. Amino acid production is one useful example. Amino acids are required for protein production, but too high a level of any amino acid is toxic, so the pathways must be controlled. Use the feedback inhibition of several pathways as examples. Section Summary 

Enzymes are chemical catalysts that accelerate chemical reactions at physiological temperatures by lowering their activation energy. Enzymes are usually proteins consisting of one or more polypeptide chains. Enzymes have an active site that provides a unique chemical environment, made up of certain amino acid R groups (residues). This unique environment is perfectly suited to convert particular chemical reactants for that enzyme, called substrates, into unstable intermediates called transition states. Enzymes and substrates are thought to bind with an induced fit, which means that enzymes undergo slight conformational adjustments upon substrate contact, leading to full, optimal binding. Enzymes bind to substrates and catalyze reactions in four different ways: bringing substrates together in an optimal orientation, compromising the bond structures of substrates so that bonds can be more easily broken, providing optimal environmental conditions for a reaction to occur, or participating directly in their chemical reaction by forming transient covalent bonds with the substrates. 

Enzyme action must be regulated so that in a given cell at a given time, the desired reactions are being catalyzed and the undesired reactions are not. Enzymes are regulated by cellular conditions, such as temperature and pH. They are also regulated through their location within a cell, sometimes being compartmentalized so that they can only catalyze reactions under certain circumstances. Inhibition and activation of enzymes via other molecules are other important ways that enzymes are regulated. Inhibitors can act competitively, noncompetitively, or allosterically; noncompetitive inhibitors are usually allosteric. Activators can also enhance the function of enzymes allosterically. The most common method by which cells regulate the enzymes in metabolic pathways is through feedback inhibition. During feedback inhibition, the products of a metabolic pathway serve as inhibitors (usually allosteric) of one or more of the enzymes (usually the first committed enzyme of the pathway) involved in the pathway that produces them. Review Questions 

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[link] Glossary active site specific region of the enzyme to which the substrate binds allosteric inhibition inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the affinity of the enzyme for its substrate coenzyme small organic molecule, such as a vitamin or its derivative, which is required to enhance the activity of an enzyme cofactor inorganic ion, such as iron and magnesium ions, required for optimal regulation of enzyme activity competitive inhibition type of inhibition in which the inhibitor competes with the substrate molecule by binding to the active site of the enzyme denature process that changes the natural properties of a substance feedback inhibition effect of a product of a reaction sequence to decrease its further production by inhibiting the activity of the first enzyme in the pathway that produces it induced fit dynamic fit between the enzyme and its substrate, in which both components modify their structures to allow for ideal binding substrate molecule on which the enzyme actsIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" This geothermal energy plant transforms thermal energy from deep in the ground into electrical energy, which can be easily used. (credit: modification of work by the U.S. Department of Defense) 

The electrical energy plant in [link] converts energy from one form to another form that can be more easily used. This type of generating plant starts with underground thermal energy (heat) and transforms it into electrical energy that will be transported to homes and factories. Like a generating plant, plants and animals also must take in energy from the environment and convert it into a form that their cells can use. Energy enters an organism s body in one form and is converted into another form that can fuel the organism s life functions. In the process of photosynthesis, plants and other photosynthetic producers take in energy in the form of light (solar energy) and convert it into chemical energy, glucose, which stores this energy in its chemical bonds. Then, a series of metabolic pathways, collectively called cellular respiration, extract the energy from the carbon carbon bonds of glucose and convert it into a form that all living things can use both producers, such as plants, and consumers, such as animals. 

Nearly all organisms perform glycolysis, the first part of both aerobic and anaerobic respiration. One of the key enzymes of glycolysis is pyruvate kinase. Without this enzyme, an organism will die because it is unable to convert nutrients into the energy it needs for survival. Scientists have taken advantage of that fact by blocking pyruvate kinase in some deadly parasites, such as the ones that cause African Sleeping Sickness and Chagas disease. Read more about this research here . 

Before students begin this chapter, it is useful to review these concepts: Cell structure including mitochondria structure; structure of macromolecules including glucose, lipids, and proteins; transport of molecules across membranes including diffusion and facilitated transport.Energy in Living Systems Energy in Living Systems 

In this section, you will explore the following questions: What is the importance of electrons for the transfer of energy in living systems? How is ATP used by the cell as an energy source? Connection for AP Courses 

As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 and Big Idea 4 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Ask students what happens when they eat a candy bar. How is the energy extracted? What do we mean when we say our bodies burn the sugar in food for energy? How are cellular respiration and combustion alike? They are both redox reactions that generate energy from the reaction of fuel (glucose in cellular respiration) with oxygen. However, our bodies need to control the release of this energy, so that cells can capture the free energy released to do useful work. 

Energy production within a cell involves many coordinated chemical pathways. Most of these pathways are combinations of oxidation and reduction reactions. Oxidation and reduction occur in tandem. An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation and reduction usually occur together, these pairs of reactions are called oxidation reduction reactions, or redox reactions . Electrons and Energy 

The removal of an electron from a molecule, oxidizing it, results in a decrease in potential energy in the oxidized compound. The electron (sometimes as part of a hydrogen atom), does not remain unbonded, however, in the cytoplasm of a cell. Rather, the electron is shifted to a second compound, reducing the second compound. The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound). The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. The transfer of energy in the form of electrons allows the cell to transfer and use energy in an incremental fashion in small packages rather than in a single, destructive burst. This chapter focuses on the extraction of energy from food; you will see that as you track the path of the transfers, you are tracking the path of electrons moving through metabolic pathways. Electron Carriers 

In living systems, a small class of compounds functions as electron shuttles: They bind and carry high-energy electrons between compounds in pathways. The principal electron carriers we will consider are derived from the B vitamin group and are derivatives of nucleotides. These compounds can be easily reduced (that is, they accept electrons) or oxidized (they lose electrons). Nicotinamide adenine dinucleotide (NAD) ( [link] ) is derived from vitamin B3, niacin. NAD + is the oxidized form of the molecule; NADH is the reduced form of the molecule after it has accepted two electrons and a proton (which together are the equivalent of a hydrogen atom with an extra electron). 

NAD + can accept electrons from an organic molecule according to the general equation: RH Reducing agent + NAD + Oxidizing agent NADH Reduced + R Oxidized RH Reducing agent + NAD + Oxidizing agent NADH Reduced + R Oxidized 

When electrons are added to a compound, they are reduced. A compound that reduces another is called a reducing agent. In the above equation, RH is a reducing agent, and NAD + is reduced to NADH. When electrons are removed from compound, it is oxidized. A compound that oxidizes another is called an oxidizing agent. In the above equation, NAD + is an oxidizing agent, and RH is oxidized to R. 

Similarly, flavin adenine dinucleotide (FAD + ) is derived from vitamin B 2 , also called riboflavin. Its reduced form is FADH 2 . A second variation of NAD, NADP, contains an extra phosphate group. Both NAD + and FAD + are extensively used in energy extraction from sugars, and NADP plays an important role in anabolic reactions and photosynthesis. The oxidized form of the electron carrier (NAD + ) is shown on the left and the reduced form (NADH) is shown on the right. The nitrogenous base in NADH has one more hydrogen ion and two more electrons than in NAD + . ATP in Living Systems 

A living cell cannot store significant amounts of free energy. Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion that could damage and then destroy the cell. Rather, a cell must be able to handle that energy in a way that enables the cell to store energy safely and release it for use only as needed. Living cells accomplish this by using the compound adenosine triphosphate (ATP). ATP is often called the energy currency of the cell, and, like currency, this versatile compound can be used to fill any energy need of the cell. How? It functions similarly to a rechargeable battery. 

When ATP is broken down, usually by the removal of its terminal phosphate group, energy is released. The energy is used to do work by the cell, usually by the released phosphate binding to another molecule, activating it. For example, in the mechanical work of muscle contraction, ATP supplies the energy to move the contractile muscle proteins. Recall the active transport work of the sodium-potassium pump in cell membranes. ATP alters the structure of the integral protein that functions as the pump, changing its affinity for sodium and potassium. In this way, the cell performs work, pumping ions against their electrochemical gradients. ATP Structure and Function 

At the heart of ATP is a molecule of adenosine monophosphate (AMP), which is composed of an adenine molecule bonded to a ribose molecule and to a single phosphate group ( [link] ). Ribose is a five-carbon sugar found in RNA, and AMP is one of the nucleotides in RNA. The addition of a second phosphate group to this core molecule results in the formation of adenosine di phosphate (ADP); the addition of a third phosphate group forms adenosine tri phosphate (ATP). ATP (adenosine triphosphate) has three phosphate groups that can be removed by hydrolysis to form ADP (adenosine diphosphate) or AMP (adenosine monophosphate).The negative charges on the phosphate group naturally repel each other, requiring energy to bond them together and releasing energy when these bonds are broken. 

The addition of a phosphate group to a molecule requires energy. Phosphate groups are negatively charged and thus repel one another when they are arranged in series, as they are in ADP and ATP. This repulsion makes the ADP and ATP molecules inherently unstable. The release of one or two phosphate groups from ATP, a process called dephosphorylation , releases energy. Energy from ATP 

Hydrolysis is the process of breaking complex macromolecules apart. During hydrolysis, water is split, or lysed, and the resulting hydrogen atom (H + ) and a hydroxyl group (OH - ) are added to the larger molecule. The hydrolysis of ATP produces ADP, together with an inorganic phosphate ion (P i ), and the release of free energy. To carry out life processes, ATP is continuously broken down into ADP, and like a rechargeable battery, ADP is continuously regenerated into ATP by the reattachment of a third phosphate group. Water, which was broken down into its hydrogen atom and hydroxyl group during ATP hydrolysis, is regenerated when a third phosphate is added to the ADP molecule, reforming ATP. 

Obviously, energy must be infused into the system to regenerate ATP. Where does this energy come from? In nearly every living thing on earth, the energy comes from the metabolism of glucose. In this way, ATP is a direct link between the limited set of exergonic pathways of glucose catabolism and the multitude of endergonic pathways that power living cells. Phosphorylation 

Recall that, in some chemical reactions, enzymes may bind to several substrates that react with each other on the enzyme, forming an intermediate complex. An intermediate complex is a temporary structure, and it allows one of the substrates (such as ATP) and reactants to more readily react with each other; in reactions involving ATP, ATP is one of the substrates and ADP is a product. During an endergonic chemical reaction, ATP forms an intermediate complex with the substrate and enzyme in the reaction. This intermediate complex allows the ATP to transfer its third phosphate group, with its energy, to the substrate, a process called phosphorylation. Phosphorylation refers to the addition of the phosphate (~P). This is illustrated by the following generic reaction: A + enzyme + ATP [ A enzyme P ] B + enzyme + ADP + phosphate ion A + enzyme + ATP [ A enzyme P ] B + enzyme + ADP + phosphate ion 

When the intermediate complex breaks apart, the energy is used to modify the substrate and convert it into a product of the reaction. The ADP molecule and a free phosphate ion are released into the medium and are available for recycling through cell metabolism. Substrate Phosphorylation 

ATP is generated through two mechanisms during the breakdown of glucose. A few ATP molecules are generated (that is, regenerated from ADP) as a direct result of the chemical reactions that occur in the catabolic pathways. A phosphate group is removed from an intermediate reactant in the pathway, and the free energy of the reaction is used to add the third phosphate to an available ADP molecule, producing ATP ( [link] ). This very direct method of phosphorylation is called substrate-level phosphorylation . In phosphorylation reactions, the gamma phosphate of ATP is attached to a protein. Oxidative Phosphorylation 

Most of the ATP generated during glucose catabolism, however, is derived from a much more complex process, chemiosmosis, which takes place in mitochondria ( [link] ) within a eukaryotic cell or the plasma membrane of a prokaryotic cell. Chemiosmosis , a process of ATP production in cellular metabolism, is used to generate 90 percent of the ATP made during glucose catabolism and is also the method used in the light reactions of photosynthesis to harness the energy of sunlight. The production of ATP using the process of chemiosmosis is called oxidative phosphorylation because of the involvement of oxygen in the process. In eukaryotes, oxidative phosphorylation takes place in mitochondria. In prokaryotes, this process takes place in the plasma membrane. (Credit: modification of work by Mariana Ruiz Villareal) Think About It 

Explain why it is more metabolically efficient for cells to extract energy from ATP rather than from the bonds of carbohydrates directly. 

This question is an application of Learning Objective 2.5 and Science Practice 6.2 because students are asked to explain why ATP is considered the energy currency of the cell. Possible answer : The catabolism of carbohydrates or other molecules produces free energy which cannot be stored. Excess free energy would result in an increase of heat in the cell, which would destroy it. Free energy can be stored in the phosphate bonds of ATP, which releases the energy when needed through the removal of a phosphate group. Mitochondrial Disease Physician 

What happens when the critical reactions of cellular respiration do not proceed correctly? Mitochondrial diseases are genetic disorders of metabolism. Mitochondrial disorders can arise from mutations in nuclear or mitochondrial DNA, and they result in the production of less energy than is normal in body cells. In type 2 diabetes, for instance, the oxidation efficiency of NADH is reduced, impacting oxidative phosphorylation but not the other steps of respiration. Symptoms of mitochondrial diseases can include muscle weakness, lack of coordination, stroke-like episodes, and loss of vision and hearing. Most affected people are diagnosed in childhood, although there are some adult-onset diseases. Identifying and treating mitochondrial disorders is a specialized medical field. The educational preparation for this profession requires a college education, followed by medical school with a specialization in medical genetics. Medical geneticists can be board certified by the American Board of Medical Genetics and go on to become associated with professional organizations devoted to the study of mitochondrial diseases, such as the Mitochondrial Medicine Society and the Society for Inherited Metabolic Disease. Section Summary 

ATP functions as the energy currency for cells. It allows the cell to store energy briefly and transport it within the cell to support endergonic chemical reactions. The structure of ATP is that of an RNA nucleotide with three phosphates attached. As ATP is used for energy, a phosphate group or two are detached, and either ADP or AMP is produced. Energy derived from glucose catabolism is used to convert ADP into ATP. When ATP is used in a reaction, the third phosphate is temporarily attached to a substrate in a process called phosphorylation. The two processes of ATP regeneration that are used in conjunction with glucose catabolism are substrate-level phosphorylation and oxidative phosphorylation through the process of chemiosmosis. Review Questions 

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[link] Glossary chemiosmosis process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane dephosphorylation removal of a phosphate group from a molecule oxidative phosphorylation production of ATP using the process of chemiosmosis and oxygen phosphorylation addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP redox reaction chemical reaction that consists of the coupling of an oxidation reaction and a reduction reaction substrate-level phosphorylation production of ATP from ADP using the excess energy from a chemical reaction and a phosphate group from a reactantGlycolysis Glycolysis 

In this section, you will explore the following question: What is the overall result, in terms of molecules produced, in the breakdown of glucose by glycolysis? Connection for AP Courses 

All organisms, from simple bacteria and yeast to complex plants and animals, carry out some form of cellular respiration to capture and supply free energy for cellular processes. Although cellular respiration and photosynthesis evolved as independent processes, today they are interdependent. The products of photosynthesis, carbohydrates and oxygen gas, are used during cellular respiration. Likewise, the byproduct of cellular respiration, CO 2 gas, is used during photosynthesis. Glycolysis is the first pathway used in the breakdown of glucose to extract free energy. Used by nearly all organisms on earth today, glycolysis likely evolved as one of the first metabolic pathways. It is important to note that glycolysis occurs in the cytoplasm of both prokaryotic and eukaryotic cells. (Remember that only eukaryotic cells have mitochondria.) 

Like all metabolic pathways, glycolysis occurs in steps or stages. In the first stage, the six-carbon ring of glucose is prepared for cleavage ( splitting ) into two three-carbon molecules by investing two molecules of ATP to energize the separation. (Don t worry; the cell will get the investment of ATP back. It s like the stock market: You have to invest money to, hopefully, make money!) As glucose is metabolized further, bonds are rearranged through a series of enzyme-catalyzed steps, and free energy is released to form ATP from ADP and free phosphate molecules. The availability of enzymes can affect the rate of glucose metabolism. Two molecules of pyruvate are ultimately produced. High-energy electrons and hydrogen atoms pass to NAD + , reducing it to NADH. Although two molecules of ATP were invested to destabilize glucose at the beginning of the process, four molecules of ATP are formed by substrate-level phosphorylation, resulting in a net gain of two ATP and two NADH molecules for the cell. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 1 and Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A All living systems require constant input of free energy. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Discuss with students how glycolysis is considered to be the oldest and most conserved metabolic pathway. Discuss with students how this process is found in all domains of life. Glycolysis is an anaerobic process, and the early atmosphere of Earth had very little oxygen. This means that glycolysis could have taken place in early prokaryotes because it does not require oxygen. Glycolysis takes place in the cell cytosol, and not the mitochondrial membrane. Prokaryotes, which don t have membrane bound organelles, can carry out glycolysis. 

Introduce the process of glycolysis using visuals such as this video . 

You have read that nearly all of the energy used by living cells comes to them in the bonds of the sugar, glucose. Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic . Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells. Glucose enters heterotrophic cells in two ways. One method is through secondary active transport in which the transport takes place against the glucose concentration gradient. The other mechanism uses a group of integral proteins called GLUT proteins, also known as glucose transporter proteins. These transporters assist in the facilitated diffusion of glucose. 

Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate . Glycolysis consists of two distinct phases. The first part of the glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. The second part of glycolysis extracts energy from the molecules and stores it in the form of ATP and NADH, the reduced form of NAD + . First Half of Glycolysis (Energy-Requiring Steps) 

Step 1. The first step in glycolysis ( [link] ) is catalyzed by hexokinase, an enzyme with broad specificity that catalyzes the phosphorylation of six-carbon sugars. Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose. This reaction prevents the phosphorylated glucose molecule from continuing to interact with the GLUT proteins, and it can no longer leave the cell because the negatively charged phosphate will not allow it to cross the hydrophobic interior of the plasma membrane. 

Step 2. In the second step of glycolysis, an isomerase converts glucose-6-phosphate into one of its isomers, fructose-6-phosphate. An isomerase is an enzyme that catalyzes the conversion of a molecule into one of its isomers. (This change from phosphoglucose to phosphofructose allows the eventual split of the sugar into two three-carbon molecules.). 

Step 3. The third step is the phosphorylation of fructose-6-phosphate, catalyzed by the enzyme phosphofructokinase. A second ATP molecule donates a high-energy phosphate to fructose-6-phosphate, producing fructose-1,6- bi sphosphate. In this pathway, phosphofructokinase is a rate-limiting enzyme. It is active when the concentration of ADP is high; it is less active when ADP levels are low and the concentration of ATP is high. Thus, if there is sufficient ATP in the system, the pathway slows down. This is a type of end product inhibition, since ATP is the end product of glucose catabolism. 

Step 4. The newly added high-energy phosphates further destabilize fructose-1,6-bisphosphate. The fourth step in glycolysis employs an enzyme, aldolase, to cleave 1,6-bisphosphate into two three-carbon isomers: dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate. 

Step 5. In the fifth step, an isomerase transforms the dihydroxyacetone-phosphate into its isomer, glyceraldehyde-3-phosphate. Thus, the pathway will continue with two molecules of a single isomer. At this point in the pathway, there is a net investment of energy from two ATP molecules in the breakdown of one glucose molecule. The first half of glycolysis uses two ATP molecules in the phosphorylation of glucose, which is then split into two three-carbon molecules. Second Half of Glycolysis (Energy-Releasing Steps) 

So far, glycolysis has cost the cell two ATP molecules and produced two small, three-carbon sugar molecules. Both of these molecules will proceed through the second half of the pathway, and sufficient energy will be extracted to pay back the two ATP molecules used as an initial investment and produce a profit for the cell of two additional ATP molecules and two even higher-energy NADH molecules. 

Step 6. The sixth step in glycolysis ( [link] ) oxidizes the sugar (glyceraldehyde-3-phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD + , producing NADH. The sugar is then phosphorylated by the addition of a second phosphate group, producing 1,3-bisphosphoglycerate. Note that the second phosphate group does not require another ATP molecule. The second half of glycolysis involves phosphorylation without ATP investment (step 6) and produces two NADH and four ATP molecules per glucose. 

Here again is a potential limiting factor for this pathway. The continuation of the reaction depends upon the availability of the oxidized form of the electron carrier, NAD + . Thus, NADH must be continuously oxidized back into NAD + in order to keep this step going. If NAD + is not available, the second half of glycolysis slows down or stops. If oxygen is available in the system, the NADH will be oxidized readily, though indirectly, and the high-energy electrons from the hydrogen released in this process will be used to produce ATP. In an environment without oxygen, an alternate pathway (fermentation) can provide the oxidation of NADH to NAD + . 

Step 7. In the seventh step, catalyzed by phosphoglycerate kinase (an enzyme named for the reverse reaction), 1,3-bisphosphoglycerate donates a high-energy phosphate to ADP, forming one molecule of ATP. (This is an example of substrate-level phosphorylation.) A carbonyl group on the 1,3-bisphosphoglycerate is oxidized to a carboxyl group, and 3-phosphoglycerate is formed. 

Step 8. In the eighth step, the remaining phosphate group in 3-phosphoglycerate moves from the third carbon to the second carbon, producing 2-phosphoglycerate (an isomer of 3-phosphoglycerate). The enzyme catalyzing this step is a mutase (isomerase). 

Step 9. Enolase catalyzes the ninth step. This enzyme causes 2-phosphoglycerate to lose water from its structure; this is a dehydration reaction, resulting in the formation of a double bond that increases the potential energy in the remaining phosphate bond and produces phosphoenolpyruvate (PEP). 

Step 10. The last step in glycolysis is catalyzed by the enzyme pyruvate kinase (the enzyme in this case is named for the reverse reaction of pyruvate s conversion into PEP) and results in the production of a second ATP molecule by substrate-level phosphorylation and the compound pyruvic acid (or its salt form, pyruvate). Many enzymes in enzymatic pathways are named for the reverse reactions, since the enzyme can catalyze both forward and reverse reactions (these may have been described initially by the reverse reaction that takes place in vitro, under non-physiological conditions). 

Gain a better understanding of the breakdown of glucose by glycolysis by visiting this site to see the process in action. 

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Glycolysis occurs in the cytoplasm of nearly every cell. Organisms, from the small, circular colonies of bacteria pictured here to the human holding the petri dish, perform glycolysis using the same ten enzymes. Because of this, it is thought that glycolysis must have evolved in the very earliest forms of life. 

[link] Outcomes of Glycolysis 

Glycolysis starts with glucose and ends with two pyruvate molecules, a total of four ATP molecules and two molecules of NADH. Two ATP molecules were used in the first half of the pathway to prepare the six-carbon ring for cleavage, so the cell has a net gain of two ATP molecules and 2 NADH molecules for its use. If the cell cannot catabolize the pyruvate molecules further, it will harvest only two ATP molecules from one molecule of glucose. Mature mammalian red blood cells are not capable of aerobic respiration the process in which organisms convert energy in the presence of oxygen and glycolysis is their sole source of ATP. If glycolysis is interrupted, these cells lose their ability to maintain their sodium-potassium pumps, and eventually, they die. 

The last step in glycolysis will not occur if pyruvate kinase, the enzyme that catalyzes the formation of pyruvate, is not available in sufficient quantities. In this situation, the entire glycolysis pathway will proceed, but only two ATP molecules will be made in the second half. Thus, pyruvate kinase is a rate-limiting enzyme for glycolysis. Think About It Nearly all organisms on Earth carry out some form of glycolysis. How does that fact support or not support the assertion that glycolysis is one of the oldest metabolic pathways? Justify your answer. Human red blood cells do not perform aerobic respiration, but they do perform glycolysis. What might happen if glycolysis were blocked in a red blood cell? Could red blood cells tap into other sources of free energy needed for their functions? 

The first Think About It question is an application of Learning Objective 1.15 and Science Practice 7.2 because metabolic pathways are examples of conserved core processes shared by all organisms. 

The second Think About It question is an application of Learning Objective 2.4 and Science Practices 1.4 and 3.1 because students are addressing questions about how the features of cells can affect the cell s ability to harvest free energy from different sources. Possible answers: If glycolysis evolved relatively late, it likely would not be as universal in organisms as it is. It probably evolved in very primitive organisms and persisted, even when additional pathways of carbohydrate metabolism evolved later. All cells must consume energy in order to carry out basic functions, such as pumping ions across membranes. A red blood cell would lose its membrane potential if glycolysis was blocked, and it would eventually die. Mature mammalian red blood cells are not capable of aerobic respiration the process in which organisms convert energy in the presence of oxygen and glycolysis is their sole source of ATP. If glycolysis is interrupted, these cells lose their ability to maintain their sodium-potassium pumps, and eventually, they die. Section Summary 

Glycolysis is the first pathway used in the breakdown of glucose to extract energy. It was probably one of the earliest metabolic pathways to evolve and is used by nearly all of the organisms on earth. Glycolysis consists of two parts: The first part prepares the six-carbon ring of glucose for cleavage into two three-carbon sugars. ATP is invested in the process during this half to energize the separation. The second half of glycolysis extracts ATP and high-energy electrons from hydrogen atoms and attaches them to NAD + . Two ATP molecules are invested in the first half and four ATP molecules are formed by substrate phosphorylation during the second half. This produces a net gain of two ATP and two NADH molecules for the cell. Review Questions 

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[link] Glossary aerobic respiration process in which organisms convert energy in the presence of oxygen anaerobic process that does not use oxygen glycolysis process of breaking glucose into two three-carbon molecules with the production of ATP and NADH isomerase enzyme that converts a molecule into its isomer pyruvate three-carbon sugar that can be decarboxylated and oxidized to make acetyl CoA, which enters the citric acid cycle under aerobic conditions; the end product of glycolysisOxidation of Pyruvate and the Citric Acid Cycle Oxidation of Pyruvate and the Citric Acid Cycle 

In this section, you will explore the following question: How is pyruvate, the product of glycolysis, prepared for entry into the citric acid cycle? What are the products of the citric acid cycle? Connection for AP Courses 

In the next stage of cellular respiration and in the presence of oxygen pyruvate produced in glycolysis is transformed into an acetyl group attached to a carrier molecule of coenzyme A. The resulting acetyl CoA is usually delivered from the cytoplasm to the mitochondria, a process that uses some ATP. In the mitochondria, acetyl CoA continues on to the citric acid cycle. The citric acid cycle (CAC or TCA- tricarboxylic acid cycle) is also known as the Krebs cycle. During the conversion of pyruvate into the acetyl group, a molecule of CO 2 and two high-energy electrons are removed. (Remember that glycolysis produces two molecules of pyruvate, and each can attach to a molecule of CoA and then enter the citric acid cycle. (A simple rule is to count the carbons. Because matter and energy cannot be created or destroyed, we must account for everything.) The electrons are picked up by NAD + , and NADH carries the electrons to a later pathway (the electron transport chain described below) for ATP production. The glucose molecule that originally entered cellular respiration in glycolysis has been completely oxidized. Chemical potential energy stored within the glucose molecules has been transferred to NADH or has been used to synthesize ATP molecules. 

The citric acid cycle occurs in the mitochondrial matrix and involves a series of redox and decarboxylation reactions that again remove high energy electrons and produce CO 2 . These electrons are carried by NADH and FADH 2 to the electron transport chain located in the cristae of the mitochondrion. (You do not need to memorize the steps in the citric acid cycle, but if provided with a diagram of the cycle, you should be able to interpret the steps.) During the cycle, ATP is synthesized from ADP and inorganic phosphate by substrate-level phosphorylation. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.2 The structure and function of subcellular components, and their interactions, provide essential cellular processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 4.6 The student is able to use representations and models to analyze situations qualitatively to describe how interactions of subcellular structures, which possess specialized functions, provide essential functions. 

Introduce the citric acid cycle using visuals such as this video . 

If oxygen is available, aerobic respiration will go forward. In eukaryotic cells, the pyruvate molecules produced at the end of glycolysis are transported into mitochondria. There, pyruvate will be transformed into an acetyl group that will be picked up and activated by a carrier compound called coenzyme A (CoA). The resulting compound is called acetyl CoA . CoA is made from vitamin B5, pantothenic acid. Acetyl CoA can be used in a variety of ways by the cell, but its major function is to deliver the acetyl group derived from pyruvate to the next stage of the pathway in glucose catabolism. Breakdown of Pyruvate 

In order for pyruvate, the product of glycolysis, to enter the next pathway, it must undergo several changes. The conversion is a three-step process ( [link] ). 

Step 1. A carboxyl group is removed from pyruvate, releasing a molecule of carbon dioxide into the surrounding medium. The result of this step is a two-carbon hydroxyethyl group bound to the enzyme (pyruvate dehydrogenase). This is the first of the six carbons from the original glucose molecule to be removed. This step proceeds twice (remember: there are two pyruvate molecules produced at the end of glycolsis) for every molecule of glucose metabolized; thus, two of the six carbons will have been removed at the end of both steps. 

Step 2. The hydroxyethyl group is oxidized to an acetyl group, and the electrons are picked up by NAD + , forming NADH. The high-energy electrons from NADH will be used later to generate ATP. 

Step 3. The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl CoA. Upon entering the mitochondrial matrix, a multi-enzyme complex converts pyruvate into acetyl CoA. In the process, carbon dioxide is released and one molecule of NADH is formed. 

Note that during the second stage of glucose metabolism, whenever a carbon atom is removed, it is bound to two oxygen atoms, producing carbon dioxide, one of the major end products of cellular respiration. Acetyl CoA to CO 2 

In the presence of oxygen, acetyl CoA delivers its acetyl group to a four-carbon molecule, oxaloacetate, to form citrate, a six-carbon molecule with three carboxyl groups; this pathway will harvest the remainder of the extractable energy from what began as a glucose molecule. This single pathway is called by different names: the citric acid cycle (for the first intermediate formed citric acid, or citrate when acetate joins to the oxaloacetate), the TCA cycle (since citric acid or citrate and isocitrate are tricarboxylic acids), and the Krebs cycle , after Hans Krebs, who first identified the steps in the pathway in the 1930s in pigeon flight muscles. Citric Acid Cycle 

Like the conversion of pyruvate to acetyl CoA, the citric acid cycle takes place in the matrix of mitochondria. Almost all of the enzymes of the citric acid cycle are soluble, with the single exception of the enzyme succinate dehydrogenase, which is embedded in the inner membrane of the mitochondrion. Unlike glycolysis, the citric acid cycle is a closed loop: The last part of the pathway regenerates the compound used in the first step. The eight steps of the cycle are a series of redox, dehydration, hydration, and decarboxylation reactions that produce two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH 2 ( [link] ). This is considered an aerobic pathway because the NADH and FADH 2 produced must transfer their electrons to the next pathway in the system, which will use oxygen. If this transfer does not occur, the oxidation steps of the citric acid cycle also do not occur. Note that the citric acid cycle produces very little ATP directly and does not directly consume oxygen. In the citric acid cycle, the acetyl group from acetyl CoA is attached to a four-carbon oxaloacetate molecule to form a six-carbon citrate molecule. Through a series of steps, citrate is oxidized, releasing two carbon dioxide molecules for each acetyl group fed into the cycle. In the process, three NAD + molecules are reduced to NADH, one FAD molecule is reduced to FADH 2 , and one ATP or GTP (depending on the cell type) is produced (by substrate-level phosphorylation). Because the final product of the citric acid cycle is also the first reactant, the cycle runs continuously in the presence of sufficient reactants. (credit: modification of work by Yikrazuul /Wikimedia Commons) Steps in the Citric Acid Cycle 

Step 1. Prior to the start of the first step, a transitional phase occurs during which pyruvic acid is converted to acetyl CoA. Then, the first step of the cycle begins: This is a condensation step, combining the two-carbon acetyl group with a four-carbon oxaloacetate molecule to form a six-carbon molecule of citrate. CoA is bound to a sulfhydryl group (-SH) and diffuses away to eventually combine with another acetyl group. This step is irreversible because it is highly exergonic. The rate of this reaction is controlled by negative feedback and the amount of ATP available. If ATP levels increase, the rate of this reaction decreases. If ATP is in short supply, the rate increases. 

Step 2. In step two, citrate loses one water molecule and gains another as citrate is converted into its isomer, isocitrate. 

Step 3. In step three, isocitrate is oxidized, producing a five-carbon molecule, -ketoglutarate, together with a molecule of CO 2 and two electrons, which reduce NAD + to NADH. This step is also regulated by negative feedback from ATP and NADH, and a positive effect of ADP. 

Steps 3 and 4. Steps three and four are both oxidation and decarboxylation steps, which release electrons that reduce NAD + to NADH and release carboxyl groups that form CO 2 molecules. -Ketoglutarate is the product of step three, and a succinyl group is the product of step four. CoA binds the succinyl group to form succinyl CoA. The enzyme that catalyzes step four is regulated by feedback inhibition of ATP, succinyl CoA, and NADH. 

Step 5. In step five, a phosphate group is substituted for coenzyme A, and a high-energy bond is formed. This energy is used in substrate-level phosphorylation (during the conversion of the succinyl group to succinate) to form either guanine triphosphate (GTP) or ATP. There are two forms of the enzyme, called isoenzymes, for this step, depending upon the type of animal tissue in which they are found. One form is found in tissues that use large amounts of ATP, such as heart and skeletal muscle. This form produces ATP. The second form of the enzyme is found in tissues that have a high number of anabolic pathways, such as liver tissues. This form produces GTP. GTP is energetically equivalent to ATP; however, its use is more restricted. In particular, protein synthesis primarily uses GTP. 

Step 6. Step six is a dehydration process that converts succinate into fumarate. Two hydrogen atoms are transferred to FAD, producing FADH 2 . The energy contained in the electrons of these atoms is insufficient to reduce NAD + but adequate to reduce FAD. Unlike NADH, this carrier remains attached to the enzyme and transfers the electrons to the electron transport chain directly. This process is made possible by the localization of the enzyme catalyzing this step inside the inner membrane of the mitochondrion. 

Step 7. Water is added to fumarate during step seven, and malate is produced. The last step in the citric acid cycle regenerates oxaloacetate by oxidizing malate. Another molecule of NADH is produced in the process. 

Click through each step of the citric acid cycle here . 

[link] Products of the Citric Acid Cycle 

Two carbon atoms come into the citric acid cycle from each acetyl group, representing four out of the six carbons of one glucose molecule. Two carbon dioxide molecules are released on each turn of the cycle; however, these do not necessarily contain the most recently added carbon atoms. The two acetyl carbon atoms will eventually be released on later turns of the cycle; thus, all six carbon atoms from the original glucose molecule are eventually incorporated into carbon dioxide. Each turn of the cycle forms three NADH molecules and one FADH 2 molecule. These carriers will connect with the last portion of aerobic respiration to produce ATP molecules. One GTP or ATP is also made in each cycle. Several of the intermediate compounds in the citric acid cycle can be used in synthesizing non-essential amino acids; therefore, the cycle is amphibolic (both catabolic and anabolic). Think About It 

Explain how citrate from the citric acid cycle might affect glycolysis. What other factors might affect the efficiency of the citric acid cycle and its products? 

This question is an application of Learning Objective 2.4 and Science Practice 6.2 because students are asked to explain the links between glycolysis and the citric acid cycle and factors that might affect the efficiency of these processes. Possible answer : High levels of citric acid inhibit glycolysis rate. Step one of the citric acid cycle is controlled by negative feedback and the amount of ATP available. If ATP levels increase, the rate of this reaction decreases. If ATP is in short supply, the rate increases. Section Summary 

In the presence of oxygen, pyruvate is transformed into an acetyl group attached to a carrier molecule of coenzyme A. The resulting acetyl CoA can enter several pathways, but most often, the acetyl group is delivered to the citric acid cycle for further catabolism. During the conversion of pyruvate into the acetyl group, a molecule of carbon dioxide and two high-energy electrons are removed. The carbon dioxide accounts for two (conversion of two pyruvate molecules) of the six carbons of the original glucose molecule. The electrons are picked up by NAD + , and the NADH carries the electrons to a later pathway for ATP production. At this point, the glucose molecule that originally entered cellular respiration has been completely oxidized. Chemical potential energy stored within the glucose molecule has been transferred to electron carriers or has been used to synthesize a few ATPs. 

The citric acid cycle is a series of redox and decarboxylation reactions that remove high-energy electrons and carbon dioxide. The electrons temporarily stored in molecules of NADH and FADH 2 are used to generate ATP in a subsequent pathway. One molecule of either GTP or ATP is produced by substrate-level phosphorylation on each turn of the cycle. There is no comparison of the cyclic pathway with a linear one. Review Questions 

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[link] Glossary acetyl CoA combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B-group vitamin) citric acid cycle (also, Krebs cycle) series of enzyme-catalyzed chemical reactions of central importance in all living cells Krebs cycle (also, citric acid cycle) alternate name for the citric acid cycle, named after Hans Krebs who first identified the steps in the pathway in the 1930s in pigeon flight muscles; see citric acid cycle TCA cycle (also, citric acid cycle) alternate name for the citric acid cycle, named after the group name for citric acid, tricarboxylic acid (TCA); see citric acid cycleOxidative Phosphorylation Oxidative Phosphorylation 

In this section, you will explore the following questions: How do electrons move through the electron transport chain and what happens to their energy levels? How is a proton (H + ) gradient established and maintained by the electron transport chain and how many ATP molecules are produced by chemiosmosis? Connection for AP Courses 

The electron transport chain (ETC) is the stage of aerobic respiration that uses free oxygen as the final electron acceptor of the electrons removed during glucose metabolism in glycolysis and the citric acid cycle. The ETC is located in membrane of the mitochondrial cristae, an area with many folds that increase the surface area available for chemical reactions. Electrons carried by NADH and FADH 2 are delivered to electron acceptor proteins embedded in the membrane as they move toward the final electron acceptor, O 2 , forming water. The electrons pass through a series of redox reactions, using free energy at three points to transport hydrogen ions across the membrane. This process contributes to the formation of the H + gradient used in chemiosmosis. As the protons are driven down their concentration gradient through ATP synthase, ATP is generated from ADP and inorganic phosphate. Under aerobic conditions, the stages of cellular respiration can generate 36-38 ATP. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. As shown in the table, concepts covered in this section also align to the Learning Objectives listed in the Curriculum Framework that provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Introduce oxidative phosphorylation using visuals such as this video . 

Have students create a visual representation that shows an overview of glycolysis and the citric acid cycle and how the cycles relate to one another. 

An example is illustrated here . 

You have just read about two pathways Introduce glucose catabolism glycolysis and the citric acid cycle that generate ATP. Most of the ATP generated during the aerobic catabolism of glucose, however, is not generated directly from these pathways. Rather, it is derived from a process that begins with moving electrons through a series of electron transporters that undergo redox reactions. This causes hydrogen ions to accumulate within the matrix space. Therefore, a concentration gradient forms in which hydrogen ions diffuse out of the matrix space by passing through ATP synthase. The current of hydrogen ions powers the catalytic action of ATP synthase, which phosphorylates ADP, producing ATP. Electron Transport Chain 

The electron transport chain ( [link] ) is the last component of aerobic respiration and is the only part of glucose metabolism that uses atmospheric oxygen. Oxygen continuously diffuses into plants; in animals, it enters the body through the respiratory system. Electron transport is a series of redox reactions that resemble a relay race or bucket brigade in that electrons are passed rapidly from one component to the next, to the endpoint of the chain where the electrons reduce molecular oxygen, producing water. There are four complexes composed of proteins, labeled I through IV in [link] , and the aggregation of these four complexes, together with associated mobile, accessory electron carriers, is called the electron transport chain. The electron transport chain is present in multiple copies in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes. The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH 2 to molecular oxygen. In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water. Complex I 

To start, two electrons are carried to the first complex aboard NADH. This complex, labeled I, is composed of flavin mononucleotide (FMN) and an iron-sulfur (Fe-S)-containing protein. FMN, which is derived from vitamin B 2, also called riboflavin, is one of several prosthetic groups or co-factors in the electron transport chain. A prosthetic group is a non-protein molecule required for the activity of a protein. Prosthetic groups are organic or inorganic, non-peptide molecules bound to a protein that facilitate its function; prosthetic groups include co-enzymes, which are the prosthetic groups of enzymes. The enzyme in complex I is NADH dehydrogenase and is a very large protein, containing 45 amino acid chains. Complex I can pump four hydrogen ions across the membrane from the matrix into the intermembrane space, and it is in this way that the hydrogen ion gradient is established and maintained between the two compartments separated by the inner mitochondrial membrane. Q and Complex II 

Complex II directly receives FADH 2 , which does not pass through complex I. The compound connecting the first and second complexes to the third is ubiquinone (Q). The Q molecule is lipid soluble and freely moves through the hydrophobic core of the membrane. Once it is reduced, (QH 2 ), ubiquinone delivers its electrons to the next complex in the electron transport chain. Q receives the electrons derived from NADH from complex I and the electrons derived from FADH 2 from complex II, including succinate dehydrogenase. This enzyme and FADH 2 form a small complex that delivers electrons directly to the electron transport chain, bypassing the first complex. Since these electrons bypass and thus do not energize the proton pump in the first complex, fewer ATP molecules are made from the FADH 2 electrons. The number of ATP molecules ultimately obtained is directly proportional to the number of protons pumped across the inner mitochondrial membrane. Complex III 

The third complex is composed of cytochrome b, another Fe-S protein, Rieske center (2Fe-2S center), and cytochrome c proteins; this complex is also called cytochrome oxidoreductase. Cytochrome proteins have a prosthetic group of heme. The heme molecule is similar to the heme in hemoglobin, but it carries electrons, not oxygen. As a result, the iron ion at its core is reduced and oxidized as it passes the electrons, fluctuating between different oxidation states: Fe ++ (reduced) and Fe +++ (oxidized). The heme molecules in the cytochromes have slightly different characteristics due to the effects of the different proteins binding them, giving slightly different characteristics to each complex. Complex III pumps protons through the membrane and passes its electrons to cytochrome c for transport to the fourth complex of proteins and enzymes (cytochrome c is the acceptor of electrons from Q; however, whereas Q carries pairs of electrons, cytochrome c can accept only one at a time). Complex IV 

The fourth complex is composed of cytochrome proteins c, a, and a 3 . This complex contains two heme groups (one in each of the two cytochromes, a, and a 3 ) and three copper ions (a pair of Cu A and one Cu B in cytochrome a 3 ). The cytochromes hold an oxygen molecule very tightly between the iron and copper ions until the oxygen is completely reduced. The reduced oxygen then picks up two hydrogen ions from the surrounding medium to make water (H 2 O). The removal of the hydrogen ions from the system contributes to the ion gradient used in the process of chemiosmosis. Chemiosmosis 

In chemiosmosis, the free energy from the series of redox reactions just described is used to pump hydrogen ions (protons) across the membrane. The uneven distribution of H + ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient), owing to the hydrogen ions positive charge and their aggregation on one side of the membrane. 

If the membrane were open to diffusion by the hydrogen ions, the ions would tend to diffuse back across into the matrix, driven by their electrochemical gradient. Recall that many ions cannot diffuse through the nonpolar regions of phospholipid membranes without the aid of ion channels. Similarly, hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through an integral membrane protein called ATP synthase ( [link] ). This complex protein acts as a tiny generator, turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient. The turning of parts of this molecular machine facilitates the addition of a phosphate to ADP, forming ATP, using the potential energy of the hydrogen ion gradient. 

ATP synthase is a complex, molecular machine that uses a proton (H + ) gradient to form ATP from ADP and inorganic phosphate (Pi). (Credit: modification of work by Klaus Hoffmeier) 

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Chemiosmosis ( [link] ) is used to generate 90 percent of the ATP made during aerobic glucose catabolism; it is also the method used in the light reactions of photosynthesis to harness the energy of sunlight in the process of photophosphorylation. Recall that the production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation. The overall result of these reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms. These atoms were originally part of a glucose molecule. At the end of the pathway, the electrons are used to reduce an oxygen molecule to oxygen ions. The extra electrons on the oxygen attract hydrogen ions (protons) from the surrounding medium, and water is formed. 

In oxidative phosphorylation, the pH gradient formed by the electron transport chain is used by ATP synthase to form ATP. 

[link] ATP Yield 

The number of ATP molecules generated from the catabolism of glucose varies. For example, the number of hydrogen ions that the electron transport chain complexes can pump through the membrane varies between species. Another source of variance stems from the shuttle of electrons across the membranes of the mitochondria. (The NADH generated from glycolysis cannot easily enter mitochondria.) Thus, electrons are picked up on the inside of mitochondria by either NAD + or FAD + . As you have learned earlier, these FAD + molecules can transport fewer ions; consequently, fewer ATP molecules are generated when FAD + acts as a carrier. NAD + is used as the electron transporter in the liver and FAD + acts in the brain. 

Another factor that affects the yield of ATP molecules generated from glucose is the fact that intermediate compounds in these pathways are used for other purposes. Glucose catabolism connects with the pathways that build or break down all other biochemical compounds in cells, and the result is somewhat messier than the ideal situations described thus far. For example, sugars other than glucose are fed into the glycolytic pathway for energy extraction. Moreover, the five-carbon sugars that form nucleic acids are made from intermediates in glycolysis. Certain nonessential amino acids can be made from intermediates of both glycolysis and the citric acid cycle. Lipids, such as cholesterol and triglycerides, are also made from intermediates in these pathways, and both amino acids and triglycerides are broken down for energy through these pathways. Overall, in living systems, these pathways of glucose catabolism extract about 34 percent of the energy contained in glucose. Activity 

Use construction paper and other art materials to create your own diagram of the electron transport chain (ETC). Be sure to include all parts of the electron transport chain, as well as the electrons themselves, NAD+ and NADH, and oxygen. On your diagram, label all parts of the ETC that transfers the free energy from electrons to another form. Then, use your model to make predictions about each of the following. Then, share your answers with the class. What would happen to free energy release if a cytochrome failed to undergo one of the redox reactions involved in the electron transport chain? What ultimately happens to the free energy in the electrons that travel down the ETC? Did you remember to have a pair of electrons travel down the ETC? What would happen if only one electron reached oxygen? Think About It Dinitrophenol (DNP) is an uncoupler that makes the inner mitochondrial membrane leaky to protons. It was used until 1938 as a weight loss drug. What effect would DNP have on the change in pH across the inner mitochondrial membrane and the overall process of cellular respiration? Why do you think DNP might be an effective weight-loss drug? Why is DNP no longer used? Cyanide inhibits cytochrome c oxidase, a component of the electron transport chain. If cyanide poisoning occurs, would you expect the pH of the intermembrane space to increase or decrease? Explain the effect of cyanide on ATP synthesis. 

This activity is an application of Learning Objective 2.4 and Science Practices 1.4 and 3.1 and Learning Objective 2.5 and Science Practice 6.2 because students will have the opportunity to create a model of the electron transport chain, allowing students to study and discuss the components of the electron transport chain that allow organisms to capture, store, and use free energy. 

An extended lab investigation on cellular respiration is available from the College Board . This activity involves respirometry of plant seeds. It is available from the College Board s AP Biology Investigative Labs: An Inquiry-Based Approach , Investigation 6 . 

The Think About It questions are applications of Learning Objective 2.4 and Science Practices 1.4 and 3.1 and Learning Objective 2.5 and Science Practice 6.2 because students are provided with situations that raise questions about cellular respiration and are then asked to explain the effects of factors that affect the process. Students are also connecting the structure of the mitochondrion to its role in cellular respiration. Possible answers to Activity: If a cytochrome failed to perform a redox reaction, the electrons could not travel to the next cytochrome, and possibly not reach the proton pumps. Even if they did reach the pumps, the ETC could not offload the electrons into oxygen, preventing any additional electrons from travelling down the ETC and also preventing any further ATP production. The free energy in the electrons is transferred to the proton pumps, allowing them to pump protons. Some is also lost as heat and the rest is transferred to oxygen at the end of the ETC. If only one electron reached oxygen, water would not form at the end of the electron transport chain until another electron travelled through the chain. Possible answers to Think About It questions: In living cells, DNP acts as an agent that can directly shuttle protons across biological membranes. Therefore, it weakens the proton concentration gradient that drives protons to pass through ATP synthase. After DNP poisoning, the electron transport chain can no longer form a proton gradient, and ATP synthase can no longer make ATP. DNP is an effective diet drug because it uncouples ATP synthesis; in other words, after taking it, a person obtains less energy out of the food he or she eats. Interestingly, one of the worst side effects of this drug is hyperthermia, or overheating of the body. Since ATP cannot be formed, the energy from electron transport is lost as heat. After cyanide poisoning, the electron transport chain can no longer pump protons into the intermembrane space. The pH of the intermembrane space would increase, the pH gradient would decrease, and ATP synthesis would stop. Section Summary 

The electron transport chain is the portion of aerobic respiration that uses free oxygen as the final electron acceptor of the electrons removed from the intermediate compounds in glucose catabolism. The electron transport chain is composed of four large, multiprotein complexes embedded in the inner mitochondrial membrane and two small diffusible electron carriers shuttling electrons between them. The electrons are passed through a series of redox reactions, with a small amount of free energy used at three points to transport hydrogen ions across a membrane. This process contributes to the gradient used in chemiosmosis. The electrons passing through the electron transport chain gradually lose energy, High-energy electrons donated to the chain by either NADH or FADH 2 complete the chain, as low-energy electrons reduce oxygen molecules and form water. The level of free energy of the electrons drops from about 60 kcal/mol in NADH or 45 kcal/mol in FADH 2 to about 0 kcal/mol in water. The end products of the electron transport chain are water and ATP. A number of intermediate compounds of the citric acid cycle can be diverted into the anabolism of other biochemical molecules, such as nonessential amino acids, sugars, and lipids. These same molecules can serve as energy sources for the glucose pathways. Review Questions 

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[link] Glossary ATP synthase (also, F1F0 ATP synthase) membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it prosthetic group (also, prosthetic cofactor) molecule bound to a protein that facilitates the function of the protein ubiquinone soluble electron transporter in the electron transport chain that connects the first or second complex to the thirdMetabolism without Oxygen Metabolism without Oxygen 

In this section, you will explore the following question: What is the fundamental difference between anaerobic cellular respiration and the different types of fermentation? Connection for AP Courses 

As was previously stated, under aerobic conditions cellular respiration can yield 36-38 ATP molecules. If oxygen is not present, ATP is only produced by substrate-level phosphorylation. Without oxygen, organisms must use another electron acceptor. Most organisms will use some form of fermentation to accomplish the regeneration of NAD + to ensure the continuation of glycolysis. In alcohol fermentation, pyruvate from glycolysis is converted to ethyl alcohol; during lactic acid fermentation, pyruvate is reduced to form lactate as an end-product. Without fermentation and anaerobic respiration, we wouldn t have yogurt or soy sauce. Nor would our muscle cells cramp from the buildup of lactate when we exercise vigorously and oxygen is scarce. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction, and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Organisms capture and store free energy for use in biological processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Discuss with students the role of fermentation in processes such as the production of bread, yogurt, alcohol, and fuels. For example as discussed in this video . 

Students may not realize that fermentation functions to regenerate NAD + ; students may think that fermentation only functions to produce additional ATP. Fermentation can produce ATP as long as there is enough NAD + to accept electrons. Without NAD + regeneration from NADH, glycolysis will deplete NAD + and come to a stop. 

In aerobic respiration, the final electron acceptor is an oxygen molecule, O 2 . If aerobic respiration occurs, then ATP will be produced using the energy of high-energy electrons carried by NADH or FADH 2 to the electron transport chain. If aerobic respiration does not occur, NADH must be reoxidized to NAD + for reuse as an electron carrier for the glycolytic pathway to continue. How is this done? Some living systems use an organic molecule as the final electron acceptor. Processes that use an organic molecule to regenerate NAD + from NADH are collectively referred to as fermentation . In contrast, some living systems use an inorganic molecule as a final electron acceptor. Both methods are called anaerobic cellular respiration in which organisms convert energy for their use in the absence of oxygen. Anaerobic Cellular Respiration 

Certain prokaryotes, including some species of bacteria and Archaea, use anaerobic respiration. For example, the group of Archaea called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms are found in soil and in the digestive tracts of ruminants, such as cows and sheep. Similarly, sulfate-reducing bacteria and Archaea, most of which are anaerobic ( [link] ), reduce sulfate to hydrogen sulfide to regenerate NAD + from NADH. The green color seen in these coastal waters is from an eruption of hydrogen sulfide-producing bacteria. These anaerobic, sulfate-reducing bacteria release hydrogen sulfide gas as they decompose algae in the water. (credit: modification of work by NASA/Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC, Visible Earth Catalog of NASA images) 

Visit this site to see anaerobic cellular respiration in action. 

[link] Lactic Acid Fermentation 

The fermentation method used by animals and certain bacteria, like those in yogurt, is lactic acid fermentation ( [link] ). This type of fermentation is used routinely in mammalian red blood cells and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid accumulation must be removed by the blood circulation and the lactate brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following: Pyruvic acid + NADH lactic acid + NAD + Pyruvic acid + NADH lactic acid + NAD + 

The enzyme used in this reaction is lactate dehydrogenase (LDH). The reaction can proceed in either direction, but the reaction from left to right is inhibited by acidic conditions. Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis. Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy. 

Lactic acid fermentation is common in muscle cells that have run out of oxygen. 

Tremetol, a metabolic poison found in the white snake root plant, prevents the metabolism of lactate. When cows eat this plant, it is concentrated in the milk they produce. Humans who consume the milk become ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case? 

[link] Alcohol Fermentation 

Another familiar fermentation process is alcohol fermentation ( [link] ) that produces ethanol, an alcohol. The first chemical reaction of alcohol fermentation is the following (CO 2 does not participate in the second reaction): Pyruvic acid CO 2 + acetaldehyde + NADH ethanol + NAD + Pyruvic acid CO 2 + acetaldehyde + NADH ethanol + NAD + 

The first reaction is catalyzed by pyruvate decarboxylase, a cytoplasmic enzyme, with a coenzyme of thiamine pyrophosphate (TPP, derived from vitamin B 1 and also called thiamine). A carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas. The loss of carbon dioxide reduces the size of the molecule by one carbon, making acetaldehyde. The second reaction is catalyzed by alcohol dehydrogenase to oxidize NADH to NAD + and reduce acetaldehyde to ethanol. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages. Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions. Fermentation of grape juice into wine produces CO 2 as a byproduct. Fermentation tanks have valves so that the pressure inside the tanks created by the carbon dioxide produced can be released. Other Types of Fermentation 

Other fermentation methods occur in bacteria. Many prokaryotes are facultatively anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen. Certain prokaryotes, like Clostridia , are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them on exposure. It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria. Various methods of fermentation are used by assorted organisms to ensure an adequate supply of NAD + for the sixth step in glycolysis. Without these pathways, that step would not occur and no ATP would be harvested from the breakdown of glucose. Lab Investigation 

Lab Investigation: Respiration of Sugars by Yeast. You are given the opportunity to design and conduct experiments to investigate whether yeasts are able to metabolize a variety of sugars, using gas pressure sensors or other means to measure CO 2 production. Think About It 

Tremetol, a metabolic poison found in the white snake plant root, prevents the metabolism of lactate. When female cows eat this plant, tremetol becomes concentrated in their milk. Humans who consume the milk become ill. Explain why the symptoms of this disease, which include vomiting, abdominal pain, and tremors, becomes worse after exercise. 

This investigation is an application of Learning Objective 2.5 and Science Practice 6.2 because in the course of their investigation, students will collect data and based on the results explain if different sugars can be metabolized in fermentation. 

Lab investigation: This lab can be done in one of several ways. A common one involves attaching a balloon to a chamber in which fermentation is occurring, allowing the carbon dioxide to gradually fill up the balloon. Please see this detailed lab description . 

The Think About It question is an application of Learning Objective 2.5 and Science Practice 6.2 because students are asked to explain how an environmental variable can interfere with the fermentation pathway. Possible answer: The illness is caused by lactate accumulation. Lactate levels rise after exercise, making the symptoms worse. Milk sickness is rare today, but was common in the Midwestern United States in the early 1800s. Section Summary 

If NADH cannot be oxidized through aerobic respiration, another electron acceptor is used. Most organisms will use some form of fermentation to accomplish the regeneration of NAD + , ensuring the continuation of glycolysis. The regeneration of NAD + in fermentation is not accompanied by ATP production; therefore, the potential of NADH to produce ATP using an electron transport chain is not utilized. Review Questions 

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[link] Glossary anaerobic cellular respiration process in which organisms convert energy for their use in the absence of oxygen fermentation process of regenerating NAD + with either an inorganic or organic compound serving as the final electron acceptor, occurs in the absence; occurs in the absence of oxygenConnections of Carbohydrate, Protein, and Lipid Metabolic Pathways Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways 

In this section, you will explore the following question: How do carbohydrate metabolic pathways, glycolysis, and the citric acid cycle interrelate with protein and lipid metabolism pathways? Connection for AP Courses 

The breakdown and synthesis of carbohydrates, proteins, lipids, and nucleic acids connect with the metabolic pathways of glycolysis and the citric acid cycle but enter the pathways at different points. Thus, these macromolecules can be used as sources of free energy. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.1 All living systems require constant input of free energy. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 2.2 The student is able to justify a scientific claim that free energy is required for living systems to maintain organization, to grow or to reproduce, but that multiple strategies exist in different living systems. 

Discuss with students how metabolic reactions include both the breakdown of molecules and the synthesis of larger molecules. For example as discussed in Anatomy and Physiology here . 

Metabolic processes are constantly taking place in the body. Metabolism is the sum of all of the chemical reactions that are involved in catabolism and anabolism. The reactions governing the breakdown of food to obtain energy are called catabolic reactions. Conversely, anabolic reactions use the energy produced by catabolic reactions to synthesize larger molecules from smaller ones, such as when the body forms proteins by stringing together amino acids. Both sets of reactions are critical to maintaining life. 

Because catabolic reactions produce energy and anabolic reactions use energy, ideally, energy usage would balance the energy produced. If the net energy change is positive (catabolic reactions release more energy than the anabolic reactions use), then the body stores the excess energy by building fat molecules for long-term storage. On the other hand, if the net energy change is negative (catabolic reactions release less energy than anabolic reactions use), the body uses stored energy to compensate for the deficiency of energy released by catabolism. 

Have students create a visual representation of the interaction of various metabolic pathways. For example: 

You have learned about the catabolism of glucose, which provides energy to living cells. But living things consume more than glucose for food. How does a turkey sandwich end up as ATP in your cells? This happens because all of the catabolic pathways for carbohydrates, proteins, and lipids eventually connect into glycolysis and the citric acid cycle pathways (see [link] ). Metabolic pathways should be thought of as porous that is, substances enter from other pathways, and intermediates leave for other pathways. These pathways are not closed systems. Many of the substrates, intermediates, and products in a particular pathway are reactants in other pathways. Connections of Other Sugars to Glucose Metabolism 

Glycogen, a polymer of glucose, is an energy storage molecule in animals. When there is adequate ATP present, excess glucose is shunted into glycogen for storage. Glycogen is made and stored in both liver and muscle. The glycogen will be hydrolyzed into glucose monomers (G-1-P) if blood sugar levels drop. The presence of glycogen as a source of glucose allows ATP to be produced for a longer period of time during exercise. Glycogen is broken down into G-1-P and converted into G-6-P in both muscle and liver cells, and this product enters the glycolytic pathway. 

Sucrose is a disaccharide with a molecule of glucose and a molecule of fructose bonded together with a glycosidic linkage. Fructose is one of the three dietary monosaccharides, along with glucose and galactose (which is part of the milk sugar, the disaccharide lactose), which are absorbed directly into the bloodstream during digestion. The catabolism of both fructose and galactose produces the same number of ATP molecules as glucose. Connections of Proteins to Glucose Metabolism 

Proteins are hydrolyzed by a variety of enzymes in cells. Most of the time, the amino acids are recycled into the synthesis of new proteins. If there are excess amino acids, however, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism ( [link] ). Each amino acid must have its amino group removed prior to entry into these pathways. The amino group is converted into ammonia. In mammals, the liver synthesizes urea from two ammonia molecules and a carbon dioxide molecule. Thus, urea is the principal waste product in mammals produced from the nitrogen originating in amino acids, and it leaves the body in urine. The carbon skeletons of certain amino acids (indicated in boxes) derived from proteins can feed into the citric acid cycle. (credit: modification of work by Mikael H ggstr m) Connections of Lipid and Glucose Metabolisms 

The lipids that are connected to the glucose pathways are cholesterol and triglycerides. Cholesterol is a lipid that contributes to cell membrane flexibility and is a precursor of steroid hormones. The synthesis of cholesterol starts with acetyl groups and proceeds in only one direction. The process cannot be reversed. 

Triglycerides are a form of long-term energy storage in animals. Triglycerides are made of glycerol and three fatty acids. Animals can make most of the fatty acids they need. Triglycerides can be both made and broken down through parts of the glucose catabolism pathways. Glycerol can be phosphorylated to glycerol-3-phosphate, which continues through glycolysis. Fatty acids are catabolized in a process called beta-oxidation that takes place in the matrix of the mitochondria and converts their fatty acid chains into two carbon units of acetyl groups. The acetyl groups are picked up by CoA to form acetyl CoA that proceeds into the citric acid cycle. Glycogen from the liver and muscles, hydrolyzed into glucose-1-phosphate, together with fats and proteins, can feed into the catabolic pathways for carbohydrates. 

Pathways of Photosynthesis and Cellular Metabolism The processes of photosynthesis and cellular metabolism consist of several very complex pathways. It is generally thought that the first cells arose in an aqueous environment a soup of nutrients probably on the surface of some porous clays. If these cells reproduced successfully and their numbers climbed steadily, it follows that the cells would begin to deplete the nutrients from the medium in which they lived as they shifted the nutrients into the components of their own bodies. This hypothetical situation would have resulted in natural selection favoring those organisms that could exist by using the nutrients that remained in their environment and by manipulating these nutrients into materials upon which they could survive. Selection would favor those organisms that could extract maximal value from the nutrients to which they had access. 

An early form of photosynthesis developed that harnessed the sun s energy using water as a source of hydrogen atoms, but this pathway did not produce free oxygen (anoxygenic photosynthesis). (Early photosynthesis did not produce free oxygen because it did not use water as the source of hydrogen ions; instead, it used materials like hydrogen sulfide and consequently produced sulfur). It is thought that glycolysis developed at this time and could take advantage of the simple sugars being produced, but these reactions were unable to fully extract the energy stored in the carbohydrates. The development of glycolysis probably predated the evolution of photosynthesis, as it was well suited to extract energy from materials spontaneously accumulating in the primeval soup. A later form of photosynthesis used water as a source of electrons and hydrogen, and generated free oxygen. Over time, the atmosphere became oxygenated, but not before the oxygen released oxidized metals in the ocean and created a rust layer in the sediment, permitting the dating of the rise of the first oxygenic photosynthesizers. Living things adapted to exploit this new atmosphere that allowed aerobic respiration as we know it to evolve. When the full process of oxygenic photosynthesis developed and the atmosphere became oxygenated, cells were finally able to use the oxygen expelled by photosynthesis to extract considerably more energy from the sugar molecules using the citric acid cycle and oxidative phosphorylation. 

[link] Think About It 

Explain how free energy can be obtained from the metabolism of carbohydrates, proteins, lipids, and even nucleic acids. Which of these molecules provides the largest amount of free energy? Justify your answer. 

This question is an application of Learning Objective 2.2 and Science Practice 6.1 because students are asked to justify the claim that organisms have multiple strategies to obtain free energy necessary to power cellular processes. Possible answer: Fatty acids and some amino acids contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle; carbohydrates, some amino acids and glycerol can enter glycolysis. Fats provide the most energy per molecule. Fats are broken down into fatty acids and glycerol. Glycerol is converted into glyceraldehyde phosphate, an intermediate of glycolysis. Also, the process of beta oxidation breaks fatty acids into two-carbon fragments, which enter the citric acid cycle as acetyl CoA. Section Summary 

The breakdown and synthesis of carbohydrates, proteins, and lipids connect with the pathways of glucose catabolism. The simple sugars are galactose, fructose, glycogen, and pentose. These are catabolized during glycolysis. The amino acids from proteins connect with glucose catabolism through pyruvate, acetyl CoA, and components of the citric acid cycle. Cholesterol synthesis starts with acetyl groups, and the components of triglycerides come from glycerol-3-phosphate from glycolysis and acetyl groups produced in the mitochondria from pyruvate. Review Questions 

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[link]Regulation of Cellular Respiration Regulation of Cellular Respiration 

In this section, you will explore the following question: What mechanisms control cellular respiration? Connection for AP Courses 

Cellular respiration is controlled by a variety of means. For example, the entry of glucose into a cell is controlled by the transport proteins that aid glucose passage through the cell membrane. However, most of the control of the respiration processes is accomplished through negative feedback inhibition of specific enzymes that respond to the intracellular concentrations of ATP, ADP, NAD + , and FAD, etc. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.C Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. Essential Knowledge 2.C.1 Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 2.16 The student is able to connect how organisms use negative feedback to maintain their internal environments. Essential Knowledge 2.C.1 Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 2.17 The student is able to evaluate data that show the effect(s) of changes in concentration of key molecules on negative feedback mechanisms. 

Cellular respiration must be regulated in order to provide balanced amounts of energy in the form of ATP. The cell also must generate a number of intermediate compounds that are used in the anabolism and catabolism of macromolecules. Without controls, metabolic reactions would quickly come to a stand-still as the forward and backward reactions reached a state of equilibrium. Resources would be used inappropriately. A cell does not need the maximum amount of ATP that it can make all the time: At times, the cell needs to shunt some of the intermediates to pathways for amino acid, protein, glycogen, lipid, and nucleic acid production. In short, the cell needs to control its metabolism. Regulatory Mechanisms 

A variety of mechanisms is used to control cellular respiration. Some type of control exists at each stage of glucose metabolism. Access of glucose to the cell can be regulated using the GLUT proteins that transport glucose ( [link] ). Different forms of the GLUT protein control passage of glucose into the cells of specific tissues. GLUT4 is a glucose transporter that is stored in vesicles. A cascade of events that occurs upon insulin binding to a receptor in the plasma membrane causes GLUT4-containing vesicles to fuse with the plasma membrane so that glucose may be transported into the cell. 

Some reactions are controlled by having two different enzymes one each for the two directions of a reversible reaction. Reactions that are catalyzed by only one enzyme can go to equilibrium, stalling the reaction. In contrast, if two different enzymes (each specific for a given direction) are necessary for a reversible reaction, the opportunity to control the rate of the reaction increases, and equilibrium is not reached. 

A number of enzymes involved in each of the pathways in particular, the enzyme catalyzing the first committed reaction of the pathway are controlled by attachment of a molecule to an allosteric site on the protein. The molecules most commonly used in this capacity are the nucleotides ATP, ADP, AMP, NAD + , and NADH. These regulators, allosteric effectors, may increase or decrease enzyme activity, depending on the prevailing conditions. The allosteric effector alters the steric structure of the enzyme, usually affecting the configuration of the active site. This alteration of the protein s (the enzyme s) structure either increases or decreases its affinity for its substrate, with the effect of increasing or decreasing the rate of the reaction. The attachment signals to the enzyme. This binding can increase or decrease the enzyme s activity, providing feedback. This feedback type of control is effective as long as the chemical affecting it is attached to the enzyme. Once the overall concentration of the chemical decreases, it will diffuse away from the protein, and the control is relaxed. Control of Catabolic Pathways 

Enzymes, proteins, electron carriers, and pumps that play roles in glycolysis, the citric acid cycle, and the electron transport chain tend to catalyze non-reversible reactions. In other words, if the initial reaction takes place, the pathway is committed to proceeding with the remaining reactions. Whether a particular enzyme activity is released depends upon the energy needs of the cell (as reflected by the levels of ATP, ADP, and AMP). Glycolysis 

The control of glycolysis begins with the first enzyme in the pathway, hexokinase ( [link] ). This enzyme catalyzes the phosphorylation of glucose, which helps to prepare the compound for cleavage in a later step. The presence of the negatively charged phosphate in the molecule also prevents the sugar from leaving the cell. When hexokinase is inhibited, glucose diffuses out of the cell and does not become a substrate for the respiration pathways in that tissue. The product of the hexokinase reaction is glucose-6-phosphate, which accumulates when a later enzyme, phosphofructokinase, is inhibited. The glycolysis pathway is primarily regulated at the three key enzymatic steps (1, 2, and 7) as indicated. Note that the first two steps that are regulated occur early in the pathway and involve hydrolysis of ATP. 

Phosphofructokinase is the main enzyme controlled in glycolysis. High levels of ATP, citrate, or a lower, more acidic pH decrease the enzyme s activity. An increase in citrate concentration can occur because of a blockage in the citric acid cycle. Fermentation, with its production of organic acids like lactic acid, frequently accounts for the increased acidity in a cell; however, the products of fermentation do not typically accumulate in cells. 

The last step in glycolysis is catalyzed by pyruvate kinase. The pyruvate produced can proceed to be catabolized or converted into the amino acid alanine. If no more energy is needed and alanine is in adequate supply, the enzyme is inhibited. The enzyme s activity is increased when fructose-1,6-bisphosphate levels increase. (Recall that fructose-1,6-bisphosphate is an intermediate in the first half of glycolysis.) The regulation of pyruvate kinase involves phosphorylation by a kinase (pyruvate kinase kinase), resulting in a less-active enzyme. Dephosphorylation by a phosphatase reactivates it. Pyruvate kinase is also regulated by ATP (a negative allosteric effect). 

If more energy is needed, more pyruvate will be converted into acetyl CoA through the action of pyruvate dehydrogenase. If either acetyl groups or NADH accumulate, there is less need for the reaction and the rate decreases. Pyruvate dehydrogenase is also regulated by phosphorylation: A kinase phosphorylates it to form an inactive enzyme, and a phosphatase reactivates it. The kinase and the phosphatase are also regulated. Citric Acid Cycle 

The citric acid cycle is controlled through the enzymes that catalyze the reactions that make the first two molecules of NADH ( [link] ). These enzymes are isocitrate dehydrogenase and ketoglutarate dehydrogenase. When adequate ATP and NADH levels are available, the rates of these reactions decrease. When more ATP is needed, as reflected in rising ADP levels, the rate increases. -ketoglutarate dehydrogenase will also be affected by the levels of succinyl CoA a subsequent intermediate in the cycle causing a decrease in activity. A decrease in the rate of operation of the pathway at this point is not necessarily negative, as the increased levels of the -ketoglutarate not used by the citric acid cycle can be used by the cell for amino acid (glutamate) synthesis. Electron Transport Chain 

Specific enzymes of the electron transport chain are unaffected by feedback inhibition, but the rate of electron transport through the pathway is affected by the levels of ADP and ATP. Greater ATP consumption by a cell is indicated by a buildup of ADP. As ATP usage decreases, the concentration of ADP decreases, and now, ATP begins to build up in the cell. This change is the relative concentration of ADP to ATP triggers the cell to slow down the electron transport chain. 

Visit this site to see an animation of the electron transport chain and ATP synthesis. 

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For a summary of feedback controls in cellular respiration, see [link] . Summary of Feedback Controls in Cellular Respiration Pathway Enzyme affected Elevated levels of effector Effect on pathway activity glycolysis hexokinase glucose-6-phosphate decrease phosphofructokinase low-energy charge (ATP, AMP), fructose-6-phosphate via fructose-2,6-bisphosphate increase high-energy charge (ATP, AMP), citrate, acidic pH decrease pyruvate kinase fructose-1,6-bisphosphate increase high-energy charge (ATP, AMP), alanine decrease pyruvate to acetyl CoA conversion pyruvate dehydrogenase ADP, pyruvate increase acetyl CoA, ATP, NADH decrease citric acid cycle isocitrate dehydrogenase ADP increase ATP, NADH decrease -ketoglutarate dehydrogenase Calcium ions, ADP increase ATP, NADH, succinyl CoA decrease electron transport chain ADP increase ATP decrease Think About It 

Phosphofructokinase is a key enzyme in glycolysis. High levels of ATP or citrate or low pH can decrease the enzyme s activity. Explain why this is beneficial to the cell. 

This question is an application of Learning Objective 2.16 and Science Practice 7.1 and Learning Objective 2.17 and Science Practice 5.3 because students are connecting changes in concentrations of key molecules (ATP and citrate) and a change in an environmental variable (pH) to the regulation of glycolysis via negative feedback. Possible answer: Elevated levels of ATP, citrate, or a more acidic pH indicate a state of high cellular energy. Thus, phosphofructokinase activity is lowered to reduce the concentration of intracellular glucose in order to slow down cellular respiration and allow the cell to use the energy it has already captured. Section Summary 

Cellular respiration is controlled by a variety of means. The entry of glucose into a cell is controlled by the transport proteins that aid glucose passage through the cell membrane. Most of the control of the respiration processes is accomplished through the control of specific enzymes in the pathways. This is a type of negative feedback, turning the enzymes off. The enzymes respond most often to the levels of the available nucleosides ATP, ADP, AMP, NAD + , and FAD. Other intermediates of the pathway also affect certain enzymes in the systems. Review Questions 

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[link] Glossary GLUT protein integral membrane protein that transports glucoseIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" This world map shows Earth s distribution of photosynthesis as seen via chlorophyll a concentrations. On land, this is evident via terrestrial plants, and in oceanic zones, via phytoplankton. (credit: modification of work by SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE) 

All biological processes require energy. To get this energy, many organisms access stored energy by eating, that is, by ingesting other organisms. But where does the stored energy in food originate? Almost all of this energy can be traced back to photosynthesis. 

Photosynthetic organisms are the basis for almost all of the food webs on the planet. For example, the Indian River Lagoon, a 156 mile mixture of fresh and salt water along the eastern coast of Florida, depends on its sea grass for the survival of its marine life. Unfortunately, when certain algal phytoplankton species grow in overabundance, it destroys the sea grass. Scientists conducted a 16 year study of algal blooms and found that extreme climate conditions, such as cold weather and low rainfall, change which particular species of phytoplankton is more likely to bloom, resulting in a die-off of sea grass, decrease in other marine life, and changes in salinity. The research study can be found here . 

Having studied the laws of thermodynamics in a previous chapter, it should be no surprise that the sun is a source of all the energy used by living organisms, that this energy can be converted, stored, and used, and that there is an interdependence between organisms with regard to that energy.Overview of Photosynthesis Overview of Photosynthesis 

In this section, you will explore the following questions: What is the relevance of photosynthesis to living organisms? What are the main cellular structures involved in photosynthesis? What are the substrates and products of photosynthesis? Connection for AP Courses 

As we learned in Chapter 7, all living organisms, from simple bacteria to complex plants and animals, require free energy to carry out cellular processes, such as growth and reproduction. Organisms use various strategies to capture, store, transform, and transfer free energy, including photosynthesis. Photosynthesis allows organisms to access enormous amounts of free energy from the sun and transform it to the chemical energy of sugars. Although all organisms carry out some form of cellular respiration, only certain organisms, called photoautotrophs, can perform photosynthesis. Examples of photoautotrophs include plants, algae, some unicellular eukaryotes, and cyanobacteria. They require the presence of chlorophyll, a specialized pigment that absorbs certain wavelengths of the visible light spectrum to harness free energy from the sun. Photosynthesis is a process where components of water and carbon dioxide are used to assemble carbohydrate molecules and where oxygen waste products are released into the atmosphere. In eukaryotes, the reactions of photosynthesis occur in chloroplasts; in prokaryotes, such as cyanobacteria, the reactions are less localized and occur within membranes and in the cytoplasm. (The structural features of the chloroplast that participate in photosynthesis will be explored in more detail later in The Light-Dependent Reactions of Photosynthesis and Using Light Energy to Make Organic Molecules.) Although photosynthesis and cellular respiration evolved as independent processes with photosynthesis creating an oxidizing atmosphere early in Earth s history today they are interdependent. As we studied in Cellular Respiration, aerobic cellular respiration taps into the oxidizing ability of oxygen to synthesize the organic compounds that are used to power cellular processes. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 1 and Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Structural and functional evidence supports the relatedness of all domains, with organisms shared many conserved core processes. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains s or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.2 Organisms use various strategies to capture and store free energy for use in biological processes. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Organisms use various strategies to capture and store free energy for use in biological processes. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Use this first part of the chapter to present an overview that will be filled out and completed in the later two portions. This will introduce the students to the biochemistry that they need to know and give them a chance to build up their understanding of the material. Importance of Photosynthesis 

Use this section to stress the importance of the interdependence between different species and the role played by photosynthesis in bringing energy to the living organisms. A number of terms, such as photoautotroph, heterotrophy, and chemoautotroph will be introduced here. 

Photosynthesis is essential to all life on earth; both plants and animals depend on it. It is the only biological process that can capture energy that originates in outer space (sunlight) and convert it into chemical compounds (carbohydrates) that every organism uses to power its metabolism. In brief, the energy of sunlight is captured and used to energize electrons, which are then stored in the covalent bonds of sugar molecules. How long lasting and stable are those covalent bonds? The energy extracted today by the burning of coal and petroleum products represents sunlight energy captured and stored by photosynthesis almost 200 million years ago. 

Plants, algae, and a group of bacteria called cyanobacteria are the only organisms capable of performing photosynthesis ( [link] ). Because they use light to manufacture their own food, they are called photoautotrophs (literally, self-feeders using light ). Other organisms, such as animals, fungi, and most other bacteria, are termed heterotrophs ( other feeders ), because they must rely on the sugars produced by photosynthetic organisms for their energy needs. A third very interesting group of bacteria synthesize sugars, not by using sunlight s energy, but by extracting energy from inorganic chemical compounds; hence, they are referred to as chemoautotrophs . Photoautotrophs including (a) plants, (b) algae, and (c) cyanobacteria synthesize their organic compounds via photosynthesis using sunlight as an energy source. Cyanobacteria and planktonic algae can grow over enormous areas in water, at times completely covering the surface. In a (d) deep sea vent, chemoautotrophs, such as these (e) thermophilic bacteria, capture energy from inorganic compounds to produce organic compounds. The ecosystem surrounding the vents has a diverse array of animals, such as tubeworms, crustaceans, and octopi that derive energy from the bacteria. (credit a: modification of work by Steve Hillebrand, U.S. Fish and Wildlife Service; credit b: modification of work by "eutrophication hypoxia"/Flickr; credit c: modification of work by NASA; credit d: University of Washington, NOAA; credit e: modification of work by Mark Amend, West Coast and Polar Regions Undersea Research Center, UAF, NOAA) 

The importance of photosynthesis is not just that it can capture sunlight s energy. A lizard sunning itself on a cold day can use the sun s energy to warm up. Photosynthesis is vital because it evolved as a way to store the energy in solar radiation (the photo- part) as high-energy electrons in the carbon-carbon bonds of carbohydrate molecules (the -synthesis part). Those carbohydrates are the energy source that heterotrophs use to power the synthesis of ATP via respiration. Therefore, photosynthesis powers 99 percent of Earth s ecosystems. When a top predator, such as a wolf, preys on a deer ( [link] ), the wolf is at the end of an energy path that went from nuclear reactions on the surface of the sun, to light, to photosynthesis, to vegetation, to deer, and finally to wolf. The energy stored in carbohydrate molecules from photosynthesis passes through the food chain. The predator that eats these deer receives a portion of the energy that originated in the photosynthetic vegetation that the deer consumed. (credit: modification of work by Steve VanRiper, U.S. Fish and Wildlife Service) Think About It Why do scientists think that photosynthesis evolved before aerobic cellular respiration? Why do carnivores, such as lions, depend on photosynthesis to survive? What evidence supports the claim that photosynthesis and cellular respiration are interdependent processes? The first Think About It question is an application of Learning Objective 1.15 and Science Practice 7.2 because students are describing the evolution of two energy-procuring processes that today are present in different organisms. The second Think About It question is an application of Learning Objective 2.5 and Science Practice 6.2 because you are explaining how the interdependent processes of photosynthesis and cellular respiration allow organisms to capture, store, and use free energy. Possible answers: Aerobic cellular respiration requires free oxygen, which was not available in the Earth s atmosphere until photosynthetic organisms produced enough oxygen as waste to support developing aerobic respiration. Carnivores at the top of the food chain eat herbivores that eat photoautotrophs. So no matter where you are in the food chain, every species depends on photosynthesis to convert light energy to chemical energy. In ecosystems that lack photosynthetic organisms (such as by forests burned by forest fire), organisms on all levels of the food chain die off. 

The structures, substrates and products of photosynthesis are introduced in this section. Remind them that [link] can also be read from right to left, if cellular respiration is the subject. This should help the students to connect the two pathways of photosynthesis and cellular respiration. 

Obtain diagrams of leaf structures to illustrate the content of this section. Try to bring in some leaves for students to look at. They have all seen lots of leaves, but probably never examined them for structural detail. A simple magnifying glass should allow them to see the inner structures discussed in this section. Main Structures and Summary of Photosynthesis 

Photosynthesis is a multi-step process that requires sunlight, carbon dioxide (which is low in energy), and water as substrates ( [link] ). After the process is complete, it releases oxygen and produces glyceraldehyde-3-phosphate (GA3P), simple carbohydrate molecules (which are high in energy) that can subsequently be converted into glucose, sucrose, or any of dozens of other sugar molecules. These sugar molecules contain energy and the energized carbon that all living things need to survive. Photosynthesis uses solar energy, carbon dioxide, and water to produce energy-storing carbohydrates. Oxygen is generated as a waste product of photosynthesis. 

The following is the chemical equation for photosynthesis ( [link] ): The basic equation for photosynthesis is deceptively simple. In reality, the process takes place in many steps involving intermediate reactants and products. Glucose, the primary energy source in cells, is made from two three-carbon GA3Ps. 

Although the equation looks simple, the many steps that take place during photosynthesis are actually quite complex. Before learning the details of how photoautotrophs turn sunlight into food, it is important to become familiar with the structures involved. 

In plants, photosynthesis generally takes place in leaves, which consist of several layers of cells. The process of photosynthesis occurs in a middle layer called the mesophyll . The gas exchange of carbon dioxide and oxygen occurs through small, regulated openings called stomata (singular: stoma), which also play roles in the regulation of gas exchange and water balance. The stomata are typically located on the underside of the leaf, which helps to minimize water loss. Each stoma is flanked by guard cells that regulate the opening and closing of the stomata by swelling or shrinking in response to osmotic changes. 

In all autotrophic eukaryotes, photosynthesis takes place inside an organelle called a chloroplast . For plants, chloroplast-containing cells exist in the mesophyll. Chloroplasts have a double membrane envelope (composed of an outer membrane and an inner membrane). Within the chloroplast are stacked, disc-shaped structures called thylakoids . Embedded in the thylakoid membrane is chlorophyll, a pigment (molecule that absorbs light) responsible for the initial interaction between light and plant material, and numerous proteins that make up the electron transport chain. The thylakoid membrane encloses an internal space called the thylakoid lumen . As shown in [link] , a stack of thylakoids is called a granum , and the liquid-filled space surrounding the granum is called stroma or bed (not to be confused with stoma or mouth, an opening on the leaf epidermis). 

Photosynthesis takes place in chloroplasts, which have an outer membrane and an inner membrane. Stacks of thylakoids called grana form a third membrane layer. 

[link] The Two Parts of Photosynthesis 

There are different terms that have been used for these reactions. Go over each pair of terms and discuss how they apply to the pathways. 

Photosynthesis takes place in two sequential stages: the light-dependent reactions and the light independent-reactions. In the light-dependent reactions , energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy. In the light-independent reactions , the chemical energy harvested during the light-dependent reactions drive the assembly of sugar molecules from carbon dioxide. Therefore, although the light-independent reactions do not use light as a reactant, they require the products of the light-dependent reactions to function. In addition, several enzymes of the light-independent reactions are activated by light. The light-dependent reactions utilize certain molecules to temporarily store the energy: These are referred to as energy carriers. The energy carriers that move energy from light-dependent reactions to light-independent reactions can be thought of as full because they are rich in energy. After the energy is released, the empty energy carriers return to the light-dependent reaction to obtain more energy. [link] illustrates the components inside the chloroplast where the light-dependent and light-independent reactions take place. Photosynthesis takes place in two stages: light dependent reactions and the Calvin cycle. Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH. The Calvin cycle, which takes place in the stroma, uses energy derived from these compounds to make GA3P from CO 2 . 

Click the link to learn more about photosynthesis. 

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Photosynthesis at the Grocery Store Foods that humans consume originate from photosynthesis. (credit: Associa o Brasileira de Supermercados) 

Major grocery stores in the United States are organized into departments, such as dairy, meats, produce, bread, cereals, and so forth. Each aisle ( [link] ) contains hundreds, if not thousands, of different products for customers to buy and consume. 

Although there is a large variety, each item links back to photosynthesis. Meats and dairy link, because the animals were fed plant-based foods. The breads, cereals, and pastas come largely from starchy grains, which are the seeds of photosynthesis-dependent plants. What about desserts and drinks? All of these products contain sugar sucrose is a plant product, a disaccharide, a carbohydrate molecule, which is built directly from photosynthesis. Moreover, many items are less obviously derived from plants: For instance, paper goods are generally plant products, and many plastics (abundant as products and packaging) are derived from algae. Virtually every spice and flavoring in the spice aisle was produced by a plant as a leaf, root, bark, flower, fruit, or stem. Ultimately, photosynthesis connects to every meal and every food a person consumes. 

[link] Section Summary 

The process of photosynthesis transformed life on Earth. By harnessing energy from the sun, photosynthesis evolved to allow living things access to enormous amounts of energy. Because of photosynthesis, living things gained access to sufficient energy that allowed them to build new structures and achieve the biodiversity evident today. 

Only certain organisms, called photoautotrophs, can perform photosynthesis; they require the presence of chlorophyll, a specialized pigment that absorbs certain portions of the visible spectrum and can capture energy from sunlight. Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates. In prokaryotes, such as cyanobacteria, the process is less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm. Review Questions 

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[link] Glossary chemoautotroph organism that can build organic molecules using energy derived from inorganic chemicals instead of sunlight chloroplast organelle in which photosynthesis takes place granum stack of thylakoids located inside a chloroplast heterotroph organism that consumes organic substances or other organisms for food light-dependent reaction first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH) light-independent reaction second stage of photosynthesis, though which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH mesophyll middle layer of chlorophyll-rich cells in a leaf photoautotroph organism capable of producing its own organic compounds from sunlight pigment molecule that is capable of absorbing certain wavelengths of light and reflecting others (which accounts for its color) stoma opening that regulates gas exchange and water evaporation between leaves and the environment, typically situated on the underside of leaves stroma fluid-filled space surrounding the grana inside a chloroplast where the light-independent reactions of photosynthesis take place thylakoid disc-shaped, membrane-bound structure inside a chloroplast where the light-dependent reactions of photosynthesis take place; stacks of thylakoids are called grana thylakoid lumen aqueous space bound by a thylakoid membrane where protons accumulate during light-driven electron transportThe Light-Dependent Reactions of Photosynthesis The Light-Dependent Reactions of Photosynthesis 

In this section, you will explore the following questions: How do plants absorb energy from sunlight? What are the differences between short and long wavelengths of light? What wavelengths are used in photosynthesis? How and where does photosynthesis occur within a plant? Connection for AP Courses 

Photosynthesis consists of two stages: the light-dependent reactions and the light-independent reactions or Calvin cycle. The light-dependent reactions occur when light is available. The overall equation for photosynthesis shows that is it a redox reaction; carbon dioxide is reduced and water is oxidized to produce oxygen: Energy + 6CO 2 + H 2 O C 6 H 12 O 6 + 6O 2 Energy + 6CO 2 + H 2 O C 6 H 12 O 6 + 6O 2 

The light-dependent reactions occur in the thylakoid membranes of chloroplasts, whereas the Calvin cycle occurs in the stroma of chloroplasts. Embedded in the thylakoid membranes are two photosystems (PS I and PS II), which are complexes of pigments that capture solar energy. Chlorophylls a and b absorb violet, blue, and red wavelengths from the visible light spectrum and reflect green. The carotenoid pigments absorb violet-blue-green light and reflect yellow-to-orange light. Environmental factors such as day length and temperature influence which pigments predominant at certain times of the year. Although the two photosystems run simultaneously, it is easier to explore them separately. Let s begin with photosystem II. 

A photon of light strikes the antenna pigments of PS II to initiate photosynthesis. In the noncyclic pathway, PS II captures photons at a slightly higher energy level than PS I. (Remember that shorter wavelengths of light carry more energy.) The absorbed energy travels to the reaction center of the antenna pigment that contains chlorophyll a and boosts chlorophyll a electrons to a higher energy level. The electrons are accepted by a primary electron acceptor protein and then pass to the electron transport chain also embedded in the thylakoid membrane. The energy absorbed in PS II is enough to oxidize (split) water, releasing oxygen into the atmosphere; the electrons released from the oxidation of water replace the electrons that were boosted from the reaction center chlorophyll. As the electrons from the reaction center chlorophyll pass through the series of electron carrier proteins, hydrogen ions (H + ) are pumped across the membrane via chemiosmosis into the interior of the thylakoid. (If this sounds familiar, it should. We studied chemiosmosis in our exploration of cellular respiration in Cellular Respiration.) This action builds up a high concentration of H+ ions, and as they flow through ATP synthase, molecules of ATP are formed. These molecules of ATP will be used to provide free energy for the synthesis of carbohydrate in the Calvin cycle, the second stage of photosynthesis. The electron transport chain connects PS II and PS I. Similar to the events occurring in PS II, this second photosystem absorbs a second photon of light, resulting in the formation of a molecule of NADPH from NADP + . The energy carried in NADPH also is used to power the chemical reactions of the Calvin cycle. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A All living systems require constant input of free energy. Essential Knowledge 2.A.2 The light-independent reactions of photosynthesis in eukaryotes involve a series of reactions that capture free energy present in light. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 3.1 The student can pose scientific questions. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 The light-independent reactions of photosynthesis in eukaryotes involve a series of reactions that capture free energy present in light. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.2 Chloroplasts are specialized organelles that capture energy through photosynthesis. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 4.4 The student is able to make a prediction about the interactions of subcellular organelles. Essential Knowledge 4.A.2 Chloroplasts are specialized organelles that capture energy through photosynthesis. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 4.5 The student is able to construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions. Essential Knowledge 4.A.2 Chloroplasts are specialized organelles that capture energy through photosynthesis. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 4.6 The student is able to use representations and models to analyze situations qualitatively to describe how interactions of subcellular structures, which possess specialized functions, provide essential functions. 

This section deals with the first half of photosynthesis. These reactions capture light energy and store it in chemicals for short periods of time to fuel the second half of photosynthesis. This is also where free oxygen can be released, but carbon dioxide is not captured or fixed. 

How can light be used to make food? When a person turns on a lamp, electrical energy becomes light energy. Like all other forms of kinetic energy, light can travel, change form, and be harnessed to do work. In the case of photosynthesis, light energy is converted into chemical energy, which photoautotrophs use to build carbohydrate molecules ( [link] ). However, autotrophs only use a few specific components of sunlight. Photoautotrophs can capture light energy from the sun, converting it into the chemical energy used to build food molecules. (credit: Gerry Atwell) What Is Light Energy? 

Everybody knows what a rainbow is, but some students may not be able to connect it to actual light sources. Obtain some way of refracting light, such as a prism, and use it to separate the components of several light sources, such as an older, incandescent light bulb, a new fluorescent type of light bulb and actual sunlight. 

When discussing the electromagnetic spectrum, include the fact that when someone sets a radio station to its number, such as 92.1 or 1450 on the dial, they are really setting the radio to the specific wavelength of spectrum used by the station. 

The sun emits an enormous amount of electromagnetic radiation (solar energy). Humans can see only a fraction of this energy, which portion is therefore referred to as visible light. The manner in which solar energy travels is described as waves. Scientists can determine the amount of energy of a wave by measuring its wavelength , the distance between consecutive points of a wave. A single wave is measured from two consecutive points, such as from crest to crest or from trough to trough ( [link] ). The wavelength of a single wave is the distance between two consecutive points of similar position (two crests or two troughs) along the wave. 

Visible light constitutes only one of many types of electromagnetic radiation emitted from the sun and other stars. Scientists differentiate the various types of radiant energy from the sun within the electromagnetic spectrum. The electromagnetic spectrum is the range of all possible frequencies of radiation ( [link] ). The difference between wavelengths relates to the amount of energy carried by them. The sun emits energy in the form of electromagnetic radiation. This radiation exists at different wavelengths, each of which has its own characteristic energy. All electromagnetic radiation, including visible light, is characterized by its wavelength. 

Each type of electromagnetic radiation travels at a particular wavelength. The longer the wavelength (or the more stretched out it appears in the diagram), the less energy is carried. Short, tight waves carry the most energy. This may seem illogical, but think of it in terms of a piece of moving a heavy rope. It takes little effort by a person to move a rope in long, wide waves. To make a rope move in short, tight waves, a person would need to apply significantly more energy. 

The electromagnetic spectrum ( [link] ) shows several types of electromagnetic radiation originating from the sun, including X-rays and ultraviolet (UV) rays. The higher-energy waves can penetrate tissues and damage cells and DNA, explaining why both X-rays and UV rays can be harmful to living organisms. Absorption of Light 

Stress the differences in the amount of energy at each wavelength, and the usefulness of the wavelengths for energy capture. Discuss what is in a grow light (artificial light source for plants grown indoors). 

Light energy initiates the process of photosynthesis when pigments absorb the light. Organic pigments, whether in the human retina or the chloroplast thylakoid, have a narrow range of energy levels that they can absorb. Energy levels lower than those represented by red light are insufficient to raise an orbital electron to a populatable, excited (quantum) state. Energy levels higher than those in blue light will physically tear the molecules apart, called bleaching. So retinal pigments can only see (absorb) 700 nm to 400 nm light, which is therefore called visible light. For the same reasons, plants pigment molecules absorb only light in the wavelength range of 700 nm to 400 nm; plant physiologists refer to this range for plants as photosynthetically active radiation. 

The visible light seen by humans as white light actually exists in a rainbow of colors. Certain objects, such as a prism or a drop of water, disperse white light to reveal the colors to the human eye. The visible light portion of the electromagnetic spectrum shows the rainbow of colors, with violet and blue having shorter wavelengths, and therefore higher energy. At the other end of the spectrum toward red, the wavelengths are longer and have lower energy ( [link] ). The colors of visible light do not carry the same amount of energy. Violet has the shortest wavelength and therefore carries the most energy, whereas red has the longest wavelength and carries the least amount of energy. (credit: modification of work by NASA) Understanding Pigments 

Concentrate on the types and functions of chlorophylls and carotenoids that are found in leaves. Discuss how all of them are always there even though they are not visible in the summer. They are visible in the fall. 

Ask the class what color coats people tend to wear in the summer and in the winter. Discuss why they do this. 

Different kinds of pigments exist, and each has evolved to absorb only certain wavelengths (colors) of visible light. Pigments reflect or transmit the wavelengths they cannot absorb, making them appear in the corresponding color. 

Chlorophylls and carotenoids are the two major classes of photosynthetic pigments found in plants and algae; each class has multiple types of pigment molecules. There are five major chlorophylls: a , b , c and d and a related molecule found in prokaryotes called bacteriochlorophyll. Chlorophyll a and chlorophyll b are found in higher plant chloroplasts and will be the focus of the following discussion. 

With dozens of different forms, carotenoids are a much larger group of pigments. The carotenoids found in fruit such as the red of tomato (lycopene), the yellow of corn seeds (zeaxanthin), or the orange of an orange peel ( -carotene) are used as advertisements to attract seed dispersers. In photosynthesis, carotenoids function as photosynthetic pigments that are very efficient molecules for the disposal of excess energy. When a leaf is exposed to full sun, the light-dependent reactions are required to process an enormous amount of energy; if that energy is not handled properly, it can do significant damage. Therefore, many carotenoids reside in the thylakoid membrane, absorb excess energy, and safely dissipate that energy as heat. 

Each type of pigment can be identified by the specific pattern of wavelengths it absorbs from visible light, which is the absorption spectrum . The graph in [link] shows the absorption spectra for chlorophyll a , chlorophyll b , and a type of carotenoid pigment called -carotene (which absorbs blue and green light). Notice how each pigment has a distinct set of peaks and troughs, revealing a highly specific pattern of absorption. Chlorophyll a absorbs wavelengths from either end of the visible spectrum (blue and red), but not green. Because green is reflected or transmitted, chlorophyll appears green. Carotenoids absorb in the short-wavelength blue region, and reflect the longer yellow, red, and orange wavelengths. (a) Chlorophyll a , (b) chlorophyll b , and (c) -carotene are hydrophobic organic pigments found in the thylakoid membrane. Chlorophyll a and b , which are identical except for the part indicated in the red box, are responsible for the green color of leaves. -carotene is responsible for the orange color in carrots. Each pigment has (d) a unique absorbance spectrum. 

Many photosynthetic organisms have a mixture of pigments; using them, the organism can absorb energy from a wider range of wavelengths. Not all photosynthetic organisms have full access to sunlight. Some organisms grow underwater where light intensity and quality decrease and change with depth. Other organisms grow in competition for light. Plants on the rainforest floor must be able to absorb any bit of light that comes through, because the taller trees absorb most of the sunlight and scatter the remaining solar radiation ( [link] ). Plants that commonly grow in the shade have adapted to low levels of light by changing the relative concentrations of their chlorophyll pigments. (credit: Jason Hollinger) 

When studying a photosynthetic organism, scientists can determine the types of pigments present by generating absorption spectra. An instrument called a spectrophotometer can differentiate which wavelengths of light a substance can absorb. Spectrophotometers measure transmitted light and compute from it the absorption. By extracting pigments from leaves and placing these samples into a spectrophotometer, scientists can identify which wavelengths of light an organism can absorb. Additional methods for the identification of plant pigments include various types of chromatography that separate the pigments by their relative affinities to solid and mobile phases. How Light-Dependent Reactions Work 

Photosystems I and II can be confusing. Obtain diagrams of both systems and use them to go through the steps of the pathways. Discuss why some plants use the cyclic form of the systems and some the linear form. Discuss why oxygen is released during one pathway, but not the other. 

The overall function of light-dependent reactions is to convert solar energy into chemical energy in the form of NADPH and ATP. This chemical energy supports the light-independent reactions and fuels the assembly of sugar molecules. The light-dependent reactions are depicted in [link] . Protein complexes and pigment molecules work together to produce NADPH and ATP. A photosystem consists of a light-harvesting complex and a reaction center. Pigments in the light-harvesting complex pass light energy to two special chlorophyll a molecules in the reaction center. The light excites an electron from the chlorophyll a pair, which passes to the primary electron acceptor. The excited electron must then be replaced. In (a) photosystem II, the electron comes from the splitting of water, which releases oxygen as a waste product. In (b) photosystem I, the electron comes from the chloroplast electron transport chain discussed below. 

The actual step that converts light energy into chemical energy takes place in a multiprotein complex called a photosystem , two types of which are found embedded in the thylakoid membrane, photosystem II (PSII) and photosystem I (PSI) ( [link] ). The two complexes differ on the basis of what they oxidize (that is, the source of the low-energy electron supply) and what they reduce (the place to which they deliver their energized electrons). 

Both photosystems have the same basic structure; a number of antenna proteins to which the chlorophyll molecules are bound surround the reaction center where the photochemistry takes place. Each photosystem is serviced by the light-harvesting complex , which passes energy from sunlight to the reaction center; it consists of multiple antenna proteins that contain a mixture of 300 400 chlorophyll a and b molecules as well as other pigments like carotenoids. The absorption of a single photon or distinct quantity or packet of light by any of the chlorophylls pushes that molecule into an excited state. In short, the light energy has now been captured by biological molecules but is not stored in any useful form yet. The energy is transferred from chlorophyll to chlorophyll until eventually (after about a millionth of a second), it is delivered to the reaction center. Up to this point, only energy has been transferred between molecules, not electrons. 

In the photosystem II (PSII) reaction center, energy from sunlight is used to extract electrons from water. The electrons travel through the chloroplast electron transport chain to photosystem I (PSI), which reduces NADP + to NADPH. The electron transport chain moves protons across the thylakoid membrane into the lumen. At the same time, splitting of water adds protons to the lumen, and reduction of NADPH removes protons from the stroma. The net result is a low pH in the thylakoid lumen, and a high pH in the stroma. ATP synthase uses this electrochemical gradient to make ATP. 

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The reaction center contains a pair of chlorophyll a molecules with a special property. Those two chlorophylls can undergo oxidation upon excitation; they can actually give up an electron in a process called a photoact . It is at this step in the reaction center, this step in photosynthesis, that light energy is converted into an excited electron. All of the subsequent steps involve getting that electron onto the energy carrier NADPH for delivery to the Calvin cycle where the electron is deposited onto carbon for long-term storage in the form of a carbohydrate.PSII and PSI are two major components of the photosynthetic electron transport chain , which also includes the cytochrome complex . The cytochrome complex, an enzyme composed of two protein complexes, transfers the electrons from the carrier molecule plastoquinone (Pq) to the protein plastocyanin (Pc), thus enabling both the transfer of protons across the thylakoid membrane and the transfer of electrons from PSII to PSI. 

The reaction center of PSII (called P680 ) delivers its high-energy electrons, one at the time, to the primary electron acceptor , and through the electron transport chain (Pq to cytochrome complex to plastocyanine) to PSI. P680 s missing electron is replaced by extracting a low-energy electron from water; thus, water is split and PSII is re-reduced after every photoact. Splitting one H 2 O molecule releases two electrons, two hydrogen atoms, and one atom of oxygen. Splitting two molecules is required to form one molecule of diatomic O 2 gas. About 10 percent of the oxygen is used by mitochondria in the leaf to support oxidative phosphorylation. The remainder escapes to the atmosphere where it is used by aerobic organisms to support respiration. 

As electrons move through the proteins that reside between PSII and PSI, they lose energy. That energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen. Those hydrogen atoms, plus the ones produced by splitting water, accumulate in the thylakoid lumen and will be used synthesize ATP in a later step. Because the electrons have lost energy prior to their arrival at PSI, they must be re-energized by PSI, hence, another photon is absorbed by the PSI antenna. That energy is relayed to the PSI reaction center (called P700 ). P700 is oxidized and sends a high-energy electron to NADP + to form NADPH. Thus, PSII captures the energy to create proton gradients to make ATP, and PSI captures the energy to reduce NADP + into NADPH. The two photosystems work in concert, in part, to guarantee that the production of NADPH will roughly equal the production of ATP. Other mechanisms exist to fine tune that ratio to exactly match the chloroplast s constantly changing energy needs. Generating an Energy Carrier: ATP 

Discuss the similarities between ATP production in the light dependent reactions and in cellular respiration. 

As in the intermembrane space of the mitochondria during cellular respiration, the buildup of hydrogen ions inside the thylakoid lumen creates a concentration gradient. The passive diffusion of hydrogen ions from high concentration (in the thylakoid lumen) to low concentration (in the stroma) is harnessed to create ATP, just as in the electron transport chain of cellular respiration. The ions build up energy because of diffusion and because they all have the same electrical charge, repelling each other. 

To release this energy, hydrogen ions will rush through any opening, similar to water jetting through a hole in a dam. In the thylakoid, that opening is a passage through a specialized protein channel called the ATP synthase. The energy released by the hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms a molecule of ATP ( [link] ). The flow of hydrogen ions through ATP synthase is called chemiosmosis because the ions move from an area of high to an area of low concentration through a semi-permeable structure. 

Visit this site and click through the animation to view the process of photosynthesis within a leaf. 

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The anatomy of a leaf. The cuticle and epidermis are the outer layers of the leaf and protect it from drying out. Chloroplasts are found in the mesophyll cells and are where photosynthesis occurs. Gas is exchanged through pores called stomata, which are opened and closed by the guard cells. Legend: 1) cuticle 2) upper epidermis 3) palisade mesophyll 4) spongy mesophyll 5) lower epidermis 6) stoma 7) guard cells 8) xylem 9) phloem 10) vascular bundle. 

[link] Think About It 

On a hot, dry day, plants close their stomata to conserve water. Predict the impact of this on photosynthesis and justify your prediction. 

The Think About It question is an application of Learning Objective 4.4 and Science Practice 6.4 because students are making a prediction about how interactions of cellular organelles and structures affect the rate of photosynthesis. Possible answer: When the stomata are closed, carbon dioxide cannot enter the leaves to form glucose in the light independent reactions. When the light independent reactions are not occurring, energy stored in ATP and NADPH cannot be transferred to carbon-carbon bonds and so eventually the light-dependent reactions will run out of ADP and NADP to accept electrons. As a result, photosynthesis will slow. Section Summary 

The pigments of the first part of photosynthesis, the light-dependent reactions, absorb energy from sunlight. A photon strikes the antenna pigments of photosystem II to initiate photosynthesis. The energy travels to the reaction center that contains chlorophyll a to the electron transport chain, which pumps hydrogen ions into the thylakoid interior. This action builds up a high concentration of ions. The ions flow through ATP synthase via chemiosmosis to form molecules of ATP, which are used for the formation of sugar molecules in the second stage of photosynthesis. Photosystem I absorbs a second photon, which results in the formation of an NADPH molecule, another energy and reducing power carrier for the light-independent reactions. Review Questions 

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[link] Glossary absorption spectrum range of wavelengths of electromagnetic radiation absorbed by a given substance antenna protein pigment molecule that directly absorbs light and transfers the energy absorbed to other pigment molecules carotenoid photosynthetic pigment that functions to dispose of excess energy chlorophyll a form of chlorophyll that absorbs violet-blue and red light and consequently has a bluish-green color; the only pigment molecule that performs the photochemistry by getting excited and losing an electron to the electron transport chain chlorophyll b accessory pigment that absorbs blue and red-orange light and consequently has a yellowish-green tint cytochrome complex group of reversibly oxidizable and reducible proteins that forms part of the electron transport chain between photosystem II and photosystem I electromagnetic spectrum range of all possible frequencies of radiation electron transport chain group of proteins between PSII and PSI that pass energized electrons and use the energy released by the electrons to move hydrogen ions against their concentration gradient into the thylakoid lumen light harvesting complex complex that passes energy from sunlight to the reaction center in each photosystem; it consists of multiple antenna proteins that contain a mixture of 300 400 chlorophyll a and b molecules as well as other pigments like carotenoids P680 reaction center of photosystem II P700 reaction center of photosystem I photoact ejection of an electron from a reaction center using the energy of an absorbed photon photon distinct quantity or packet of light energy photosystem group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy photosystem I integral pigment and protein complex in thylakoid membranes that uses light energy to transport electrons from plastocyanin to NADP + (which becomes reduced to NADPH in the process) photosystem II integral protein and pigment complex in thylakoid membranes that transports electrons from water to the electron transport chain; oxygen is a product of PSII primary electron acceptor pigment or other organic molecule in the reaction center that accepts an energized electron from the reaction center reaction center complex of chlorophyll molecules and other organic molecules that is assembled around a special pair of chlorophyll molecules and a primary electron acceptor; capable of undergoing oxidation and reduction spectrophotometer instrument that can measure transmitted light and compute the absorption wavelength distance between consecutive points of equal position (two crests or two troughs) of a wave in a graphic representation; inversely proportional to the energy of the radiationUsing Light Energy to Make Organic Molecules Using Light Energy to Make Organic Molecules 

In this section, you will explore the following questions: What are the reactions in the Calvin cycle described as the light-independent reactions? Why does the term carbon fixation describe the products of the Calvin cycle? What is the role of photosynthesis in the energy cycle of all living organisms? Connection for AP Courses 

The free energy stored in ATP and NADPH produced in the light-dependent reactions is used to power the chemical reactions of the light-independent reactions or Calvin cycle, which can occur during both the day and night. In the Calvin cycle, an enzyme called ribulose biphosphate carboxylase (RuBisCO), catalyzes a reaction with CO 2 and another molecule called ribulose biphosphate (RuBP) that is regenerated from a previous Calvin cycle. After a series of chemical reactions, the carbon from carbon dioxide in the atmosphere is fixed into carbohydrates, specifically a three-carbon molecule called glyceraldehydes-3-phosphate (G3P). (Again, count the carbons as we explore the Calvin cycle.) After three turns of the cycle, a three-carbon molecule of G3P leaves the cycle to become part of a carbohydrate molecule. The remaining G3P molecules stay in the cycle to be regenerated into RuBP, which is then ready to react with more incoming CO 2 . In other words, the cell generates a stockpile of G3P to be assembled into organic molecules, including carbohydrates. Each step of the Calvin cycle is catalyzed by specific enzymes. (You do not have to memorize the reactions of the Calvin cycle; however, if provided with a diagram of the cycle, you should be able to interpret it.) Some plants evolved chemical modifications to more efficiently trap CO 2 if environmental conditions limit its availability. For example, when it s hot outside, plants tend to keep their stomata closed to prevent excessive water loss; when the outside temperature cools, stomata open and plants take in CO 2 and use a more efficient system to feed it into the Calvin cycle. 

As we explored in Overview of Photosynthesis, photosynthesis forms an energy link with cellular respiration. Plants need both photosynthesis and respiration in order to conduct metabolic processes during both light and dark times. Therefore, plant cells contain both chloroplasts and mitochondria. 

Information presented and the examples highlighted in the section, support concepts and learning objectives outlined in Big Idea 2 of the AP Biology Curriculum Framework, as shown in the table. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2.A.2 Light energy captured in photosynthesis is stored in carbohydrates produced during the Calvin cycle. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store, and use free energy. Essential Knowledge 2.A.2 Light energy captured in photosynthesis is stored in carbohydrates produced during the Calvin cycle Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store, or use free energy. 

As with the light dependent reactions, obtain detailed diagrams of the Calvin cycle, such as Figure 8.18 and walk the students through it. Emphasize the roles of ATP and NADPH and where they enter and leave the pathway. Explain why the Calvin Cycle makes lots of G3P, but not all of it is used to make other carbohydrates. What happens to the rest? Why are all three stages of the cycle necessary? 

This is a good time to discuss the evolution of photosynthesis. Ask if it is possible to have the capture of energy without the release of oxygen? Could this have happened on Earth? Why would the release of oxygen be beneficial to organisms? Was it a good idea for all of the organisms living at that time? 

The light-independent reactions or Calvin cycle are not really independent of light. They depend on the earlier reactions to supply ATP and NADPH in order to proceed. This pathway makes the storage and transport form of energy used by nearly every living organism, sugars. It does not make glucose directly, but a chemical that is also an intermediate in cellular respiration, glyceraldehyde-3-phosphate (G3P). This can be used to make a variety of biologically important compounds, including glucose. The Calvin Cycle 

After the energy from the sun is converted into chemical energy and temporarily stored in ATP and NADPH molecules, the cell has the fuel needed to build carbohydrate molecules for long-term energy storage. The products of the light-dependent reactions, ATP and NADPH, have lifespans in the range of millionths of seconds, whereas the products of the light-independent reactions (carbohydrates and other forms of reduced carbon) can survive for hundreds of millions of years. The carbohydrate molecules made will have a backbone of carbon atoms. Where does the carbon come from? It comes from carbon dioxide, the gas that is a waste product of respiration in microbes, fungi, plants, and animals. 

In plants, carbon dioxide (CO 2 ) enters the leaves through stomata, where it diffuses over short distances through intercellular spaces until it reaches the mesophyll cells. Once in the mesophyll cells, CO 2 diffuses into the stroma of the chloroplast the site of light-independent reactions of photosynthesis. These reactions actually have several names associated with them. Another term, the Calvin cycle , is named for the man who discovered it, and because these reactions function as a cycle. Others call it the Calvin-Benson cycle to include the name of another scientist involved in its discovery. The most outdated name is dark reactions, because light is not directly required ( [link] ). However, the term dark reaction can be misleading because it implies incorrectly that the reaction only occurs at night or is independent of light, which is why most scientists and instructors no longer use it. Light reactions harness energy from the sun to produce chemical bonds, ATP, and NADPH. These energy-carrying molecules are made in the stroma where carbon fixation takes place. 

The light-independent reactions of the Calvin cycle can be organized into three basic stages: fixation, reduction, and regeneration. Stage 1: Fixation 

In the stroma, in addition to CO 2 , two other components are present to initiate the light-independent reactions: an enzyme called ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), and three molecules of ribulose bisphosphate (RuBP), as shown in [link] . RuBP has five atoms of carbon, flanked by two phosphates. 

The Calvin cycle has three stages. In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule, 3-PGA. In stage 2, the organic molecule is reduced using electrons supplied by NADPH. In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue. Only one carbon dioxide molecule is incorporated at a time, so the cycle must be completed three times to produce a single three-carbon GA3P molecule, and six times to produce a six-carbon glucose molecule. 

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RuBisCO catalyzes a reaction between CO 2 and RuBP. For each CO 2 molecule that reacts with one RuBP, two molecules of another compound (3-PGA) form. PGA has three carbons and one phosphate. Each turn of the cycle involves only one RuBP and one carbon dioxide and forms two molecules of 3-PGA. The number of carbon atoms remains the same, as the atoms move to form new bonds during the reactions (3 atoms from 3CO 2 + 15 atoms from 3RuBP = 18 atoms in 3 atoms of 3-PGA). This process is called carbon fixation , because CO 2 is fixed from an inorganic form into organic molecules. Stage 2: Reduction 

ATP and NADPH are used to convert the six molecules of 3-PGA into six molecules of a chemical called glyceraldehyde 3-phosphate (G3P). That is a reduction reaction because it involves the gain of electrons by 3-PGA. Recall that a reduction is the gain of an electron by an atom or molecule. Six molecules of both ATP and NADPH are used. For ATP, energy is released with the loss of the terminal phosphate atom, converting it into ADP; for NADPH, both energy and a hydrogen atom are lost, converting it into NADP + . Both of these molecules return to the nearby light-dependent reactions to be reused and reenergized. Stage 3: Regeneration 

Interestingly, at this point, only one of the G3P molecules leaves the Calvin cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three turns of the Calvin cycle to fix enough net carbon to export one G3P. But each turn makes two G3Ps, thus three turns make six G3Ps. One is exported while the remaining five G3P molecules remain in the cycle and are used to regenerate RuBP, which enables the system to prepare for more CO 2 to be fixed. Three more molecules of ATP are used in these regeneration reactions. 

This link leads to an animation of the Calvin cycle. Click stage 1, stage 2, and then stage 3 to see G3P and ATP regenerate to form RuBP. 

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The harsh conditions of the desert have led plants like these cacti to evolve variations of the light-independent reactions of photosynthesis. These variations increase the efficiency of water usage, helping to conserve water and energy. (credit: Piotr Wojtkowski) 

[link] The Energy Cycle 

Whether the organism is a bacterium, plant, or animal, all living things access energy by breaking down carbohydrate molecules. But if plants make carbohydrate molecules, why would they need to break them down, especially when it has been shown that the gas organisms release as a waste product (CO 2 ) acts as a substrate for the formation of more food in photosynthesis? Remember, living things need energy to perform life functions. In addition, an organism can either make its own food or eat another organism either way, the food still needs to be broken down. Finally, in the process of breaking down food, called cellular respiration, heterotrophs release needed energy and produce waste in the form of CO 2 gas. 

In nature, there is no such thing as waste. Every single atom of matter and energy is conserved, recycling over and over infinitely. Substances change form or move from one type of molecule to another, but their constituent atoms never disappear. ( Figure 1.21 is an illustrative example of this process.) 

CO 2 is no more a form of waste than oxygen is wasteful to photosynthesis. Both are byproducts of reactions that move on to other reactions. Photosynthesis absorbs light energy to build carbohydrates in chloroplasts, and aerobic cellular respiration releases energy by using oxygen to metabolize carbohydrates in the cytoplasm and mitochondria. Both processes use electron transport chains to capture the energy necessary to drive other reactions. These two powerhouse processes, photosynthesis and cellular respiration, function in biological, cyclical harmony to allow organisms to access life-sustaining energy that originates millions of miles away in a burning star humans call the sun. Photosynthesis consumes carbon dioxide and produces oxygen. Aerobic respiration consumes oxygen and produces carbon dioxide. These two processes play an important role in the carbon cycle. (credit: modification of work by Stuart Bassil) 

Photosynthesis and aerobic respiration are interrelated in important ways. During photosynthesis, plants take in carbon dioxide and water. The water molecule is split, the oxygen is released into the atmosphere, and the carbon dioxide is used to build carbohydrates. During aerobic respiration, organisms take in water and oxygen for respiration and produce carbon dioxide. 

[link] Activity 

Create a model or diagram to show the links between photosynthesis and cellular respiration. Think About It 

What cellular features and processes are similar in both respiration and photosynthesis? 

This activity and question are applications of Learning Objective 2.4 and science practices 1.4 and 3.1 because students are creating and using a representation to explore the link between photosynthesis and cellular respiration, two processes that organisms use to capture, store, and use free energy. Additional information for students can be found here : Possible answer: Search for free images that show what the model or diagram should look like here , here , or here . Both cellular respiration and photosynthesis occur in/on double-membrane organelles in the cell. Both processes use electron carriers to shuttle electrons to and between membrane proteins that pump protons. The pumping of protons creates an electrochemical gradient that drives the synthesis of ATP. Section Summary 

Using the energy carriers formed in the first steps of photosynthesis, the light-independent reactions, or the Calvin cycle, take in CO 2 from the environment. An enzyme, RuBisCO, catalyzes a reaction with CO 2 and another molecule, RuBP. After three cycles, a three-carbon molecule of G3P leaves the cycle to become part of a carbohydrate molecule. The remaining G3P molecules stay in the cycle to be regenerated into RuBP, which is then ready to react with more CO 2 . Photosynthesis forms an energy cycle with the process of cellular respiration. Plants need both photosynthesis and respiration for their ability to function in both the light and dark, and to be able to interconvert essential metabolites. Therefore, plants contain both chloroplasts and mitochondria. Review Questions 

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[link] Glossary Calvin cycle light-independent reactions of photosynthesis that convert carbon dioxide from the atmosphere into carbohydrates using the energy and reducing power of ATP and NADPH carbon fixation process of converting inorganic CO 2 gas into organic compounds reduction gain of electron(s) by an atom or moleculeIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Have you ever become separated from a friend while in a crowd? If so, you know the challenge of searching for someone when surrounded by thousands of other people. If you and your friend have cell phones, your chances of finding each other are good. A cell phone s ability to send and receive messages makes it an ideal communication device. (credit: modification of work by Vincent and Bella Productions) 

Imagine what life would be like if you and the people around you could not communicate. You would not be able to express your wishes, nor could you ask questions to find out more about your environment. Social organization is dependent on communication between the individuals; without communication, society would fall apart. 

As with people, it is vital for a cell to interact with its environment. This is true whether it is a unicellular organism or one of many cells forming a larger organism. In order to respond to external stimuli, cells have developed complex mechanisms of communication that can receive a message, transfer the information across the plasma membrane, and produce changes within the cell in response to the message. In multicellular organisms, cells send and receive chemical messages constantly to coordinate the actions of distant organs, tissues, and cells. 

While the necessity for cellular communication in larger organisms seems obvious, even single-celled organisms communicate with each other. Yeast cells signal each other to aid in mating. Some forms of bacteria coordinate their actions in order to form large complexes called biofilms (Figure 9.18) or to organize the production of toxins to remove competing organisms. The ability of cells to communicate through chemical signals originated in single cells and was essential for the evolution of multicellular organisms. 

Cell signaling is vital to the survival of organisms. For example, chemical signals tell cells when to make hormones such as insulin. Cell division also depends on chemical signals. When the chemical signals do not function properly, cells can divide uncontrollably, forming cancerous tumors. Scientists recently discovered a cell signaling pathway that protects cancer cells from being killed by the body s immune system. The hope is to use this knowledge to create treatments that target this cell signaling pathway so that the cancer cells self destruct. More about that can be found here : Scientists pinpoint a new line of defense used by cancer cells. 

Ask students to think about how a cell phone works. Draw on the board the sequence: signal, phone hardware, sound. What happens after the call? Immediate action if it is urgent, delayed action if not, or simply ignore and delete if the message is deemed irrelevant. Cells function similarly. The body is abuzz with messages. Not all cells can receive all messages, and the response to the same message can and should be different depending on the type of targeted cell.Signaling Molecules and Cellular Receptors Signaling Molecules and Cellular Receptors 

In this section, you will explore the following questions: What are the four types of signaling that are found in multicellular organisms? What are the differences between internal receptors and cell-surface receptors? What is the relationship between a ligand s structure and its mechanism of action? Connection for AP Courses 

Just like you communicate with your classmates face-to-face, using your phone, or via e-mail, cells communicate with each other by both inter and intracellular signaling. Cells detect and respond to changes in the environment using signaling pathways. Signaling pathways enable organisms to coordinate cellular activities and metabolic processes. Errors in these pathways can cause disease. Signaling cells secrete molecules called ligands that bind to target cells and initiate a chain of events within the target cell. For example, when epinephrine is released, binding to target cells, those cells respond by converting glycogen to glucose. Cell communication can happen over short distances. For example, neurotransmitters are released across a synapse to transfer messages between neurons Figure 1.3 . Gap junctions and plasmodesmata allow small molecules, including signaling molecules, to flow between neighboring cells. Cell communication can also happen over long distances using. For example, hormones released from endocrine cells travel to target cells in multiple body systems. How does a ligand such as a hormone traveling through the bloodstream know when it has reached its target organ to initiate a cellular response? Nearly all cell signaling pathways involve three stages: reception, signal transduction, and cellular response. 

Cell signaling pathways begin when the ligand binds to a receptor, a protein that is embedded in the plasma membrane of the target cell or found in the cell cytoplasm. The receptors are very specific, and each ligand is recognized by a different one. This stage of the pathway is called reception. Molecules that are nonpolar, such as steroids, diffuse across the cell membrane and bind to internal receptors. In turn, the receptor-ligand complex moves to the nucleus and interacts with cellular DNA. This changes how a gene is expressed. Polar ligands, on the other hand, interact with membrane receptor protein. Some membrane receptors work by changing conformation so that certain ions, such as Na + and K + , can pass through the plasma membrane. Other membrane receptors interact with a G-protein on the cytoplasmic side of the plasma membrane, which causes a series of reactions inside the cell. Disruptions to this process are linked to several diseases, including cholera. 

It is important to keep in mind that each cell has a variety of receptors, allowing it to respond to a variety of stimuli. Some receptors can bind several different ligands; for example, odorant molecules/receptors associated with the sense of smell in animals. Once the signaling molecule and receptor interact, a cascade of events called signal transduction usually amplifies the signal inside the cell. 

The content presented in this section supports the Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework listed. The AP Learning Objectives merge Essential knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP Exam questions. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals. Essential Knowledge 3.D.3 Signal transduction pathways link signal reception with cellular response. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.34 The student is able to construct explanations of cell communication through cell-to-cell direct contact or through chemical signaling. Essential Knowledge 3.D.3 Signal transduction pathways link signal reception with cellular response. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.35 The student is able to create representations that depict how cell-to-cell communication occurs by direct contact or from a distance through chemical signaling. 

Go back to the comparison to the phone. The signal is an incoming phone call and it must be directed to a specific phone number. That is the signaling molecule. It must reach the dialed phone number, not a wrong number. A signal targets a specific receptor. Ask students if they know the physical nature of a cell phone signal. It is an electromagnetic wave, a radio wave. Then discuss the nature of the signal sent and recognized by cells. Though most are chemical signals, mention the body receives other signals. Ask students to make a list: light, sound, pressure, temperature are all signals. 

When the signal is received by the phone, it is processed. Some calls are ignored, result in delayed action or are acted upon immediately depending on the originator and content. In the same way, cells prioritize signals or ignore them if not significant. For example, the strength of a signal must cross a threshold to cause a nerve response. 

The distance traveled by signals matches the intended response. Autocrine signals result in amplification because a cell responds to its own signal, proliferates, and increases the output of signal. For example, the activation of B-cells in the immune system is caused by signals from the helper T-cells. Paracrine signals, such as nerve impulses, are best for signaling between neighboring cells and often have fast responses. Some neurotransmitters which have delayed and long lasting effects use G-protein-linked receptors, not ligand-gated receptors. Long distance messages can integrate the body response by reaching several target tissues at once. The fight-or-flight response requires glucose for skeletal muscles, faster heartbeat, dilating bronchi, all geared towards the same goal. [link] summarizes this information. Signal Effect Examples Autocrine Amplification of signal by acting on self; increased output Bacterial autoinducers; T-helper cells response to cytokines Paracrine Affect only neighboring cells, localized effect Neurotransmitters; immune cells Endocrine Integration of response targeting several cells or organs at once; affect remote locations Hypothalamus-Pituitary-organ axis; Inflammatory mediators secreted by macrophages 

Ask students if all nervous system signaling should be mediated by ligand-gated receptors, which render a rapid and short duration response. Skeletal muscles use ligand-gated receptors, which give rapid and time-limited responses. Some situations require a lasting effect. Smooth muscles carry G-protein-linked receptors because smooth muscle responses, bladder, intestine, etc., have prolonged action. This is an example of the same ligand, acetylcholine, binding to two different types of receptors. 

Distribute large sheets of paper and markers. Divide the class in groups and assign each group a specific type of receptor: ion channel-linked receptors (gated ion channels), G-protein-linked receptors, receptor tyrosine kinases, and internal (intracellular) receptors. More than one group of students may work on the same receptor. Ask students to set up a concept map starting with signal types: water soluble molecules or lipophilic molecules for each receptor molecule. For each receptor type, diagram the second messenger and amplification scheme. Allow enough time to create the posters and ask each group to present the receptor to the class. Here the goal is to divide and conquer the receptors because cellular signaling is confusing. Show this animation from Davidson College in class or provide a link for later view by students. 

There are two kinds of communication in the world of living cells. Communication between cells is called intercellular signaling , and communication within a cell is called intracellular signaling . An easy way to remember the distinction is by understanding the Latin origin of the prefixes: inter- means "between" (for example, intersecting lines are those that cross each other) and intra- means "inside" (like intravenous). 

Chemical signals are released by signaling cells in the form of small, usually volatile or soluble molecules called ligands. A ligand is a molecule that binds another specific molecule, in some cases, delivering a signal in the process. Ligands can thus be thought of as signaling molecules. Ligands interact with proteins in target cells , which are cells that are affected by chemical signals; these proteins are also called receptors . Ligands and receptors exist in several varieties; however, a specific ligand will have a specific receptor that typically binds only that ligand. Forms of Signaling 

There are four categories of chemical signaling found in multicellular organisms: paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions ( [link] ). The main difference between the different categories of signaling is the distance that the signal travels through the organism to reach the target cell. Not all cells are affected by the same signals. In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling). Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell. Signaling via gap junctions involves signaling molecules moving directly between adjacent cells. Paracrine Signaling 

Signals that act locally between cells that are close together are called paracrine signals . Paracrine signals move by diffusion through the extracellular matrix. These types of signals usually elicit quick responses that last only a short amount of time. In order to keep the response localized, paracrine ligand molecules are normally quickly degraded by enzymes or removed by neighboring cells. Removing the signals will reestablish the concentration gradient for the signal, allowing them to quickly diffuse through the intracellular space if released again. 

One example of paracrine signaling is the transfer of signals across synapses between nerve cells. A nerve cell consists of a cell body, several short, branched extensions called dendrites that receive stimuli, and a long extension called an axon, which transmits signals to other nerve cells or muscle cells. The junction between nerve cells where signal transmission occurs is called a synapse. A synaptic signal is a chemical signal that travels between nerve cells. Signals within the nerve cells are propagated by fast-moving electrical impulses. When these impulses reach the end of the axon, the signal continues on to a dendrite of the next cell by the release of chemical ligands called neurotransmitters by the presynaptic cell (the cell emitting the signal). The neurotransmitters are transported across the very small distances between nerve cells, which are called chemical synapses ( [link] ). The small distance between nerve cells allows the signal to travel quickly; this enables an immediate response, such as, Take your hand off the stove! 

When the neurotransmitter binds the receptor on the surface of the postsynaptic cell, the electrochemical potential of the target cell changes, and the next electrical impulse is launched. The neurotransmitters that are released into the chemical synapse are degraded quickly or get reabsorbed by the presynaptic cell so that the recipient nerve cell can recover quickly and be prepared to respond rapidly to the next synaptic signal. The distance between the presynaptic cell and the postsynaptic cell called the synaptic gap is very small and allows for rapid diffusion of the neurotransmitter. Enzymes in the synapatic cleft degrade some types of neurotransmitters to terminate the signal. Endocrine Signaling 

Signals from distant cells are called endocrine signals , and they originate from endocrine cells . (In the body, many endocrine cells are located in endocrine glands, such as the thyroid gland, the hypothalamus, and the pituitary gland.) These types of signals usually produce a slower response but have a longer-lasting effect. The ligands released in endocrine signaling are called hormones, signaling molecules that are produced in one part of the body but affect other body regions some distance away. 

Hormones travel the large distances between endocrine cells and their target cells via the bloodstream, which is a relatively slow way to move throughout the body. Because of their form of transport, hormones get diluted and are present in low concentrations when they act on their target cells. This is different from paracrine signaling, in which local concentrations of ligands can be very high. Autocrine Signaling 

Autocrine signals are produced by signaling cells that can also bind to the ligand that is released. This means the signaling cell and the target cell can be the same or a similar cell (the prefix auto- means self, a reminder that the signaling cell sends a signal to itself). This type of signaling often occurs during the early development of an organism to ensure that cells develop into the correct tissues and take on the proper function. Autocrine signaling also regulates pain sensation and inflammatory responses. Further, if a cell is infected with a virus, the cell can signal itself to undergo programmed cell death, killing the virus in the process. In some cases, neighboring cells of the same type are also influenced by the released ligand. In embryological development, this process of stimulating a group of neighboring cells may help to direct the differentiation of identical cells into the same cell type, thus ensuring the proper developmental outcome. Direct Signaling Across Gap Junctions 

Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells. These water-filled channels allow small signaling molecules, called intracellular mediators , to diffuse between the two cells. Small molecules, such as calcium ions (Ca 2+ ), are able to move between cells, but large molecules like proteins and DNA cannot fit through the channels. The specificity of the channels ensures that the cells remain independent but can quickly and easily transmit signals. The transfer of signaling molecules communicates the current state of the cell that is directly next to the target cell; this allows a group of cells to coordinate their response to a signal that only one of them may have received. In plants, plasmodesmata are ubiquitous, making the entire plant into a giant, communication network. Types of Receptors 

Receptors are protein molecules in the target cell or on its surface that bind ligand. There are two types of receptors, internal receptors and cell-surface receptors. Internal receptors 

Internal receptors , also known as intracellular or cytoplasmic receptors, are found in the cytoplasm of the cell and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane. Once inside the cell, many of these molecules bind to proteins that act as regulators of mRNA synthesis (transcription) to mediate gene expression. Gene expression is the cellular process of transforming the information in a cell's DNA into a sequence of amino acids, which ultimately forms a protein. When the ligand binds to the internal receptor, a conformational change is triggered that exposes a DNA-binding site on the protein. The ligand-receptor complex moves into the nucleus, then binds to specific regulatory regions of the chromosomal DNA and promotes the initiation of transcription ( [link] ). Transcription is the process of copying the information in a cells DNA into a special form of RNA called messenger RNA (mRNA); the cell uses information in the mRNA (which moves out into the cytoplasm and associates with ribosomes) to link specific amino acids in the correct order, producing a protein. Internal receptors can directly influence gene expression without having to pass the signal on to other receptors or messengers. Hydrophobic signaling molecules typically diffuse across the plasma membrane and interact with intracellular receptors in the cytoplasm. Many intracellular receptors are transcription factors that interact with DNA in the nucleus and regulate gene expression. Cell-Surface Receptors 

Cell-surface receptors , also known as transmembrane receptors, are cell surface, membrane-anchored (integral) proteins that bind to external ligand molecules. This type of receptor spans the plasma membrane and performs signal transduction, in which an extracellular signal is converted into an intercellular signal. Ligands that interact with cell-surface receptors do not have to enter the cell that they affect. Cell-surface receptors are also called cell-specific proteins or markers because they are specific to individual cell types. 

Because cell-surface receptor proteins are fundamental to normal cell functioning, it should come as no surprise that a malfunction in any one of these proteins could have severe consequences. Errors in the protein structures of certain receptor molecules have been shown to play a role in hypertension (high blood pressure), asthma, heart disease, and cancer. 

Each cell-surface receptor has three main components: an external ligand-binding domain, a hydrophobic membrane-spanning region, and an intracellular domain inside the cell. The ligand-binding domain is also called the extracellular domain . The size and extent of each of these domains vary widely, depending on the type of receptor. 

How Viruses Recognize a Host Unlike living cells, many viruses do not have a plasma membrane or any of the structures necessary to sustain life. Some viruses are simply composed of an inert protein shell containing DNA or RNA. To reproduce, viruses must invade a living cell, which serves as a host, and then take over the hosts cellular apparatus. But how does a virus recognize its host? 

Viruses often bind to cell-surface receptors on the host cell. For example, the virus that causes human influenza (flu) binds specifically to receptors on membranes of cells of the respiratory system. Chemical differences in the cell-surface receptors among hosts mean that a virus that infects a specific species (for example, humans) cannot infect another species (for example, chickens). 

However, viruses have very small amounts of DNA or RNA compared to humans, and, as a result, viral reproduction can occur rapidly. Viral reproduction invariably produces errors that can lead to changes in newly produced viruses; these changes mean that the viral proteins that interact with cell-surface receptors may evolve in such a way that they can bind to receptors in a new host. Such changes happen randomly and quite often in the reproductive cycle of a virus, but the changes only matter if a virus with new binding properties comes into contact with a suitable host. In the case of influenza, this situation can occur in settings where animals and people are in close contact, such as poultry and swine farms. 1 Once a virus jumps to a new host, it can spread quickly. Scientists watch newly appearing viruses (called emerging viruses) closely in the hope that such monitoring can reduce the likelihood of global viral epidemics. 

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Cell-surface receptors are involved in most of the signaling in multicellular organisms. There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors. 

Ion channel-linked receptors bind a ligand and open a channel through the membrane that allows specific ions to pass through. To form a channel, this type of cell-surface receptor has an extensive membrane-spanning region. In order to interact with the phospholipid fatty acid tails that form the center of the plasma membrane, many of the amino acids in the membrane-spanning region are hydrophobic in nature. Conversely, the amino acids that line the inside of the channel are hydrophilic to allow for the passage of water or ions. When a ligand binds to the extracellular region of the channel, there is a conformational change in the proteins structure that allows ions such as sodium, calcium, magnesium, and hydrogen to pass through ( [link] ). Gated ion channels form a pore through the plasma membrane that opens when the signaling molecule binds. The open pore then allows ions to flow into or out of the cell. 

G-protein-linked receptors bind a ligand and activate a membrane protein called a G-protein. The activated G-protein then interacts with either an ion channel or an enzyme in the membrane ( [link] ). All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site. 

Cell signaling using G-protein-linked receptors occurs as a cyclic series of events. Before the ligand binds, the inactive G-protein can bind to a newly revealed site on the receptor specific for its binding. Once the G-protein binds to the receptor, the resultant shape change activates the G-protein, which releases GDP and picks up GTP. The subunits of the G-protein then split into the subunit and the subunit. One or both of these G-protein fragments may be able to activate other proteins as a result. After awhile, the GTP on the active subunit of the G-protein is hydrolyzed to GDP and the subunit is deactivated. The subunits reassociate to form the inactive G-protein and the cycle begins anew. Heterotrimeric G proteins have three subunits: , , and . When a signaling molecule binds to a G-protein-coupled receptor in the plasma membrane, a GDP molecule associated with the subunit is exchanged for GTP. The and subunits dissociate from the subunit, and a cellular response is triggered either by the subunit or the dissociated pair. Hydrolysis of GTP to GDP terminates the signal. 

G-protein-linked receptors have been extensively studied and much has been learned about their roles in maintaining health. Bacteria that are pathogenic to humans can release poisons that interrupt specific G-protein-linked receptor function, leading to illnesses such as pertussis, botulism, and cholera. In cholera ( [link] ), for example, the water-borne bacterium Vibrio cholerae produces a toxin, choleragen, that binds to cells lining the small intestine. The toxin then enters these intestinal cells, where it modifies a G-protein that controls the opening of a chloride channel and causes it to remain continuously active, resulting in large losses of fluids from the body and potentially fatal dehydration as a result. Transmitted primarily through contaminated drinking water, cholera is a major cause of death in the developing world and in areas where natural disasters interrupt the availability of clean water. The cholera bacterium, Vibrio cholerae , creates a toxin that modifies G-protein-mediated cell signaling pathways in the intestines. Modern sanitation eliminates the threat of cholera outbreaks, such as the one that swept through New York City in 1866. This poster from that era shows how, at that time, the way that the disease was transmitted was not understood. (credit: New York City Sanitary Commission) 

Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme. In some cases, the intracellular domain of the receptor itself is an enzyme. Other enzyme-linked receptors have a small intracellular domain that interacts directly with an enzyme. The enzyme-linked receptors normally have large extracellular and intracellular domains, but the membrane-spanning region consists of a single alpha-helical region of the peptide strand. When a ligand binds to the extracellular domain, a signal is transferred through the membrane, activating the enzyme. Activation of the enzyme sets off a chain of events within the cell that eventually leads to a response. One example of this type of enzyme-linked receptor is the tyrosine kinase receptor ( [link] ). A kinase is an enzyme that transfers phosphate groups from ATP to another protein. The tyrosine kinase receptor transfers phosphate groups to tyrosine molecules (tyrosine residues). First, signaling molecules bind to the extracellular domain of two nearby tyrosine kinase receptors. The two neighboring receptors then bond together, or dimerize. Phosphates are then added to tyrosine residues on the intracellular domain of the receptors (phosphorylation). The phosphorylated residues can then transmit the signal to the next messenger within the cytoplasm. 

A receptor tyrosine kinase is an enzyme-linked receptor with a single transmembrane region, and extracellular and intracellular domains. Binding of a signaling molecule to the extracellular domain causes the receptor to dimerize. Tyrosine residues on the intracellular domain are then autophosphorylated, triggering a downstream cellular response. The signal is terminated by a phosphatase that removes the phosphates from the phosphotyrosine residues. 

[link] Signaling Molecules 

Produced by signaling cells and the subsequent binding to receptors in target cells, ligands act as chemical signals that travel to the target cells to coordinate responses. The types of molecules that serve as ligands are incredibly varied and range from small proteins to small ions like calcium (Ca 2+ ). Small Hydrophobic Ligands 

Small hydrophobic ligands can directly diffuse through the plasma membrane and interact with internal receptors. Important members of this class of ligands are the steroid hormones. Steroids are lipids that have a hydrocarbon skeleton with four fused rings; different steroids have different functional groups attached to the carbon skeleton. Steroid hormones include the female sex hormone, estradiol, which is a type of estrogen; the male sex hormone, testosterone; and cholesterol, which is an important structural component of biological membranes and a precursor of steriod hormones ( [link] ). Other hydrophobic hormones include thyroid hormones and vitamin D. In order to be soluble in blood, hydrophobic ligands must bind to carrier proteins while they are being transported through the bloodstream. Steroid hormones have similar chemical structures to their precursor, cholesterol. Because these molecules are small and hydrophobic, they can diffuse directly across the plasma membrane into the cell, where they interact with internal receptors. Water-Soluble Ligands 

Water-soluble ligands are polar and therefore cannot pass through the plasma membrane unaided; sometimes, they are too large to pass through the membrane at all. Instead, most water-soluble ligands bind to the extracellular domain of cell-surface receptors. This group of ligands is quite diverse and includes small molecules, peptides, and proteins. Other Ligands 

Nitric oxide (NO) is a gas that also acts as a ligand. It is able to diffuse directly across the plasma membrane, and one of its roles is to interact with receptors in smooth muscle and induce relaxation of the tissue. NO has a very short half-life and therefore only functions over short distances. Nitroglycerin, a treatment for heart disease, acts by triggering the release of NO, which causes blood vessels to dilate (expand), thus restoring blood flow to the heart. NO has become better known recently because the pathway that it affects is targeted by prescription medications for erectile dysfunction, such as Viagra (erection involves dilated blood vessels). Think About It Cells grown in the laboratory are placed in a solution containing a dye that is unable to pass through the plasma membrane. If a ligand is then added to the solution, observations show that the dye enters the cell. Describe the type of receptor the ligand most likely binds to and explain your reasoning. HER2 is a receptor tyrosine kinase. In 30 percent of human breast cancers, HER2 is permanently activated, resulting in unregulated cell division. Lapatinib, a drug used to treat breast cancer, inhibits HER2 receptor tyrosine kinase autophosphorylation (the process by which the receptor adds phosphate onto itself), thus reducing tumor growth. Besides autophosphorylation, explain another feature of the cell signaling pathway that can be affected by Lapatinib. In certain cancers, the GTPase activity of RAS G-protein in inhibited. This means that the RAS G-protein can no longer hydrolyze GTP into GDP. Explain what effect this would have on downstream cellular events. 

The first question is an application of Learning Objective 3.34 and Science Practice 6.3 because students are explaining how cells communicate through signaling pathways, beginning with the interaction between a signal molecule and receptor protein. 

The second and third questions are applications of Learning Objective 3.34 and Science Practice 6.3 because students are explaining how disruptions in cell signaling pathways can affect a cell s normal function. Answers: Presumably the dye is a large molecule, most likely hydrophilic. The ligand may change the permeability of the cell membrane; for example, it binds to gated channels that allow passage of the dye. Give acetylcholine binding to its receptor and allowing the passage of Na + as an example. In both cases the answer is the same; all the reactions downstream of phosphorylation do not take place because they depend on the first reaction. The last step, transcription and translation of proteins needed for cell division, does not take place and cell proliferation is inhibited. Section Summary 

Cells communicate by both inter- and intracellular signaling. Signaling cells secrete ligands that bind to target cells and initiate a chain of events within the target cell. The four categories of signaling in multicellular organisms are paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions. Paracrine signaling takes place over short distances. Endocrine signals are carried long distances through the bloodstream by hormones, and autocrine signals are received by the same cell that sent the signal or other nearby cells of the same kind. Gap junctions allow small molecules, including signaling molecules, to flow between neighboring cells. 

Internal receptors are found in the cell cytoplasm. Here, they bind ligand molecules that cross the plasma membrane; these receptor-ligand complexes move to the nucleus and interact directly with cellular DNA. Cell-surface receptors transmit a signal from outside the cell to the cytoplasm. Ion channel-linked receptors, when bound to their ligands, form a pore through the plasma membrane through which certain ions can pass. G-protein-linked receptors interact with a G-protein on the cytoplasmic side of the plasma membrane, promoting the exchange of bound GDP for GTP and interacting with other enzymes or ion channels to transmit a signal. Enzyme-linked receptors transmit a signal from outside the cell to an intracellular domain of a membrane-bound enzyme. Ligand binding causes activation of the enzyme. Small hydrophobic ligands (like steroids) are able to penetrate the plasma membrane and bind to internal receptors. Water-soluble hydrophilic ligands are unable to pass through the membrane; instead, they bind to cell-surface receptors, which transmit the signal to the inside of the cell. Review Questions 

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A. B. Sigalov, The School of Nature. IV. Learning from Viruses, Self/Nonself 1, no. 4 (2010): 282-298. Y. Cao, X. Koh, L. Dong, X. Du, A. Wu, X. Ding, H. Deng, Y. Shu, J. Chen, T. Jiang, Rapid Estimation of Binding Activity of Influenza Virus Hemagglutinin to Human and Avian Receptors, PLoS One 6, no. 4 (2011): e18664. Glossary autocrine signal signal that is sent and received by the same or similar nearby cells cell-surface receptor cell-surface protein that transmits a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell chemical synapse small space between axon terminals and dendrites of nerve cells where neurotransmitters function endocrine cell cell that releases ligands involved in endocrine signaling (hormones) endocrine signal long-distance signal that is delivered by ligands (hormones) traveling through an organisms circulatory system from the signaling cell to the target cell enzyme-linked receptor cell-surface receptor with intracellular domains that are associated with membrane-bound enzymes extracellular domain region of a cell-surface receptor that is located on the cell surface G-protein-linked receptor cell-surface receptor that activates membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components intercellular signaling communication between cells internal receptor (also, intracellular receptor) receptor protein that is located in the cytosol of a cell and binds to ligands that pass through the plasma membrane intracellular mediator (also, second messenger) small molecule that transmits signals within a cell intracellular signaling communication within cells ion channel-linked receptor cell-surface receptor that forms a plasma membrane channel, which opens when a ligand binds to the extracellular domain (ligand-gated channels) ligand molecule produced by a signaling cell that binds with a specific receptor, delivering a signal in the process neurotransmitter chemical ligand that carries a signal from one nerve cell to the next paracrine signal signal between nearby cells that is delivered by ligands traveling in the liquid medium in the space between the cells receptor protein in or on a target cell that bind to ligands signaling cell cell that releases signal molecules that allow communication with another cell synaptic signal chemical signal (neurotransmitter) that travels between nerve cells target cell cell that has a receptor for a signal or ligand from a signaling cellPropagation of the Signal Propagation of the Signal 

In this section, you will explore the following questions: How does the binding of a ligand initiate signal transduction throughout a cell? What is the role of second messengers in signal transduction? Connection for AP Courses 

During signal transduction, a series of relay proteins inside the cytoplasm of the target cell activate target proteins, resulting in a cellular response. These cascades are complex because of the interplay between proteins. A significant contributor to cell signaling cascades is the phosphorylation of molecules by enzymes known as kinases. (Substrate level phosphorylation was studied when you learned about glycolysis.) By adding a phosphate group, phosphorylation changes the shapes of proteins. This change in shape activates or inactivates them. Second messengers, e.g., cAMP and Ca 2+ , are often used to transmit signals within a cell. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals. Essential Knowledge 3.D.3 Signal transduction pathways link signal reception with cellular response. Science Practice 1.5 The student can re-express key elements of natural phenomena across multiple representations in the domain. Learning Objective 3.36 The student is able to describe a model that expresses the key elements of signal transduction pathways by which a signal is converted to a cellular response. 

Ask students what would happen if suddenly the fire alarm went off. It should trigger the fight-or-flight response. Some organs must be activated for the response: skeletal muscle, heart, and the release of glucose from liver. Other organs have their activities dampened: the stomach halts digestion and salivary glands stop production. 

Ask students what happens if they get a loud alarm sound while eating. The likely response is that nauseous feeling and digestion cut short, courtesy of our sympathetic system. The same signal that activates all the systems needed for survival also shuts down the systems which are not essential for the rapid reaction needed to escape danger. An animation of fight-or-flight response can be seen here . 

Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm. Continuation of a signal in this manner is called signal transduction . Signal transduction only occurs with cell-surface receptors because internal receptors are able to interact directly with DNA in the nucleus to initiate protein synthesis. 

When a ligand binds to its receptor, conformational changes occur that affect the receptor s intracellular domain. Conformational changes of the extracellular domain upon ligand binding can propagate through the membrane region of the receptor and lead to activation of the intracellular domain or its associated proteins. In some cases, binding of the ligand causes dimerization of the receptor, which means that two receptors bind to each other to form a stable complex called a dimer. A dimer is a chemical compound formed when two molecules (often identical) join together. The binding of the receptors in this manner enables their intracellular domains to come into close contact and activate each other. Binding Initiates a Signaling Pathway 

After the ligand binds to the cell-surface receptor, the activation of the receptor s intracellular components sets off a chain of events that is called a signaling pathway or a signaling cascade. In a signaling pathway, second messengers, enzymes, and activated proteins interact with specific proteins, which are in turn activated in a chain reaction that eventually leads to a change in the cell s environment ( [link] ). The events in the cascade occur in a series, much like a current flows in a river. Interactions that occur before a certain point are defined as upstream events, and events after that point are called downstream events. 

The epidermal growth factor (EGF) receptor (EGFR) is a receptor tyrosine kinase involved in the regulation of cell growth, wound healing, and tissue repair. When EGF binds to the EGFR, a cascade of downstream events causes the cell to grow and divide. If EGFR is activated at inappropriate times, uncontrolled cell growth (cancer) may occur. 

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Signaling pathways can get very complicated very quickly because most cellular proteins can affect different downstream events, depending on the conditions within the cell. A single pathway can branch off toward different endpoints based on the interplay between two or more signaling pathways, and the same ligands are often used to initiate different signals in different cell types. This variation in response is due to differences in protein expression in different cell types. Another complicating element is signal integration of the pathways, in which signals from two or more different cell-surface receptors merge to activate the same response in the cell. This process can ensure that multiple external requirements are met before a cell commits to a specific response. 

The effects of extracellular signals can also be amplified by enzymatic cascades. At the initiation of the signal, a single ligand binds to a single receptor. However, activation of a receptor-linked enzyme can activate many copies of a component of the signaling cascade, which amplifies the signal. Methods of Intracellular Signaling 

The induction of a signaling pathway depends on the modification of a cellular component by an enzyme. There are numerous enzymatic modifications that can occur, and they are recognized in turn by the next component downstream. The following are some of the more common events in intracellular signaling. 

Observe an animation of cell signaling at this site . 

[link] Phosphorylation 

One of the most common chemical modifications that occurs in signaling pathways is the addition of a phosphate group (PO 4 3 ) to a molecule such as a protein in a process called phosphorylation. The phosphate can be added to a nucleotide such as GMP to form GDP or GTP. Phosphates are also often added to serine, threonine, and tyrosine residues of proteins, where they replace the hydroxyl group of the amino acid ( [link] ). The transfer of the phosphate is catalyzed by an enzyme called a kinase . Various kinases are named for the substrate they phosphorylate. Phosphorylation of serine and threonine residues often activates enzymes. Phosphorylation of tyrosine residues can either affect the activity of an enzyme or create a binding site that interacts with downstream components in the signaling cascade. Phosphorylation may activate or inactivate enzymes, and the reversal of phosphorylation, dephosphorylation by a phosphatase, will reverse the effect. In protein phosphorylation, a phosphate group (PO 4 -3 ) is added to residues of the amino acids serine, threonine, and tyrosine. Second Messengers 

Second messengers are small molecules that propagate a signal after it has been initiated by the binding of the signaling molecule to the receptor. These molecules help to spread a signal through the cytoplasm by altering the behavior of certain cellular proteins. 

Calcium ion is a widely used second messenger. The free concentration of calcium ions (Ca 2+ ) within a cell is very low because ion pumps in the plasma membrane continuously use adenosine-5'-triphosphate (ATP) to remove it. For signaling purposes, Ca 2+ is stored in cytoplasmic vesicles, such as the endoplasmic reticulum, or accessed from outside the cell. When signaling occurs, ligand-gated calcium ion channels allow the higher levels of Ca 2+ that are present outside the cell (or in intracellular storage compartments) to flow into the cytoplasm, which raises the concentration of cytoplasmic Ca 2+ . The response to the increase in Ca 2+ varies, depending on the cell type involved. For example, in the -cells of the pancreas, Ca 2+ signaling leads to the release of insulin, and in muscle cells, an increase in Ca 2+ leads to muscle contractions. 

Another second messenger utilized in many different cell types is cyclic AMP (cAMP) . Cyclic AMP is synthesized by the enzyme adenylyl cyclase from ATP ( [link] ). The main role of cAMP in cells is to bind to and activate an enzyme called cAMP-dependent kinase (A-kinase) . A-kinase regulates many vital metabolic pathways: It phosphorylates serine and threonine residues of its target proteins, activating them in the process. A-kinase is found in many different types of cells, and the target proteins in each kind of cell are different. Differences give rise to the variation of the responses to cAMP in different cells. This diagram shows the mechanism for the formation of cyclic AMP (cAMP). cAMP serves as a second messenger to activate or inactivate proteins within the cell. Termination of the signal occurs when an enzyme called phosphodiesterase converts cAMP into AMP. 

Present in small concentrations in the plasma membrane, inositol phospholipids are lipids that can also be converted into second messengers. Because these molecules are membrane components, they are located near membrane-bound receptors and can easily interact with them. Phosphatidylinositol (PI) is the main phospholipid that plays a role in cellular signaling. Enzymes known as kinases phosphorylate PI to form PI-phosphate (PIP) and PI-bisphosphate (PIP 2 ). 

The enzyme phospholipase C cleaves PIP 2 to form diacylglycerol (DAG) and inositol triphosphate (IP 3 ) ( [link] ). These products of the cleavage of PIP 2 serve as second messengers. Diacylglycerol (DAG) remains in the plasma membrane and activates protein kinase C (PKC), which then phosphorylates serine and threonine residues in its target proteins. IP 3 diffuses into the cytoplasm and binds to ligand-gated calcium channels in the endoplasmic reticulum to release Ca 2+ that continues the signal cascade. The enzyme phospholipase C breaks down PIP 2 into IP 3 and DAG, both of which serve as second messengers. Think About It 

The same second messengers are used in many different cells, but the response to second messengers is different in each cell. How is this possible? 

This question is an application of Learning Objective 3.36 and Science Practice 1.5 because students are using a model of a cell signaling pathway to describe how signal transduction is converted to a cellular response. Answer: The second messenger interacts with protein targets and these proteins vary according to the cell. Review Questions 

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Ligand binding to the receptor allows for signal transduction through the cell. The chain of events that conveys the signal through the cell is called a signaling pathway or cascade. Signaling pathways are often very complex because of the interplay between different proteins. A major component of cell signaling cascades is the phosphorylation of molecules by enzymes known as kinases. Phosphorylation adds a phosphate group to serine, threonine, and tyrosine residues in a protein, changing their shapes, and activating or inactivating the protein. Small molecules like nucleotides can also be phosphorylated. Second messengers are small, non-protein molecules that are used to transmit a signal within a cell. Some examples of second messengers are calcium ions (Ca 2+ ), cyclic AMP (cAMP), diacylglycerol (DAG), and inositol triphosphate (IP 3 ). Glossary cyclic AMP (cAMP) second messenger that is derived from ATP cyclic AMP-dependent kinase (also, protein kinase A, or PKA) kinase that is activated by binding to cAMP diacylglycerol (DAG) cleavage product of PIP 2 that is used for signaling within the plasma membrane dimer chemical compound formed when two molecules join together dimerization (of receptor proteins) interaction of two receptor proteins to form a functional complex called a dimer inositol phospholipid lipid present at small concentrations in the plasma membrane that is converted into a second messenger; it has inositol (a carbohydrate) as its hydrophilic head group inositol triphosphate (IP 3 ) cleavage product of PIP 2 that is used for signaling within the cell kinase enzyme that catalyzes the transfer of a phosphate group from ATP to another molecule second messenger small, non-protein molecule that propagates a signal within the cell after activation of a receptor causes its release signal integration interaction of signals from two or more different cell-surface receptors that merge to activate the same response in the cell signal transduction propagation of the signal through the cytoplasm (and sometimes also the nucleus) of the cell signaling pathway (also signaling cascade) chain of events that occurs in the cytoplasm of the cell to propagate the signal from the plasma membrane to produce a responseResponse to the Signal Response to the Signal 

In this section you will explore the following questions: How do signaling pathways direct protein expression, cellular metabolism, and cell growth? What is the role of apoptosis in the development and maintenance of a healthy organism? Connection for AP Courses 

The initiation of a signaling pathway results in a cellular response to changes in the external environment. This response can take many different forms, including protein synthesis, a change in cell metabolism, cell division and growth, or even cell death. As we will explore in more detail in later chapters, some pathways activate enzymes that interact within DNA transcription factors to promote gene expression, others can cause cells to store energy as glycogen as fat, or result in free energy availability in the form of glucose. Cell division and growth are almost always stimulated by external signals called growth factors; left unregulated, cell growth leads to cancer. Programmed cell death, or apoptosis, removes damaged or unnecessary cells and plays a vital role in development, including morphogenesis of fingers and toes. Termination of the cell signaling cascade is important to ensure that the response to a signal is appropriate in timing and intensity. Degradation of signaling molecules and dephosphorylation of intermediates of the pathway are two ways signals are terminated within cells. Conditions where signaling pathways are blocked or defective can be deleterious, preventative, or prophylactic; examples include diabetes, heart disease, autoimmune disease, toxins, anesthetics, and birth control pills. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 3 and Big Idea 2 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals. Essential Knowledge 3.D.4 Changes in signal transduction pathways can alter cellular response. Science Practice 1.5 The student can re-express key elements of natural phenomena across multiple representations in the domain. Learning Objective 3.36 The student is able to describe a model that expresses the key elements of signal transduction pathways by which a signal is converted to a cellular response. Essential Knowledge 3.D.4 Changes in signal transduction pathways can alter cellular response. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 3.37 The student is able to justify claims based on scientific evidence that changes in signal transduction pathways can alter cellular response. Essential Knowledge 3.D.4 Changes in signal transduction pathways can alter cellular response. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.39 The student is able to construct an explanation of how certain drugs affect signal reception and, consequently, signal transduction pathways. 

Big Idea 2 Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 

Enduring Understanding 2.E Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Essential Knowledge 2.E.1 Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 2.34 The student is able to describe the role of programmed cell death in development and differentiation, the reuse of molecules, and the maintenance of dynamic homeostasis. 

Remind students that response to the environment is one of the characteristics of life. Organisms must be able to perceive changes in the environment in order to survive. Ask students to make a list of which changes an organism should perceive to survive. The list may include availability of nutrients, changes in physical conditions, perception of noxious chemicals and the presence of predators. Multicellular organisms must be able to coordinate the responses of their cells. The integration of responses first requires signal transmission, then reception and transduction. The signaling pathways can easily confuse students. Many enzymes and other proteins are involved in cascading reactions. This website offers clear explanations of signal transduction and a number of activities to engage students using the flight-or-flight response as an example. The activity, Dealing Signals, can help students understand signaling pathways asks them to act as the components of a signaling pathway by taking cues from cell communication cards. Students mimic signaling pathways by running in place, interacting with specific classmates by either bumping into them or holding them, and leaning or lifting arms to simulate conformational changes. Further information about his activity can be found here . 

Inside the cell, ligands bind to their internal receptors, allowing them to directly affect the cell s DNA and protein-producing machinery. Using signal transduction pathways, receptors in the plasma membrane produce a variety of effects on the cell. The results of signaling pathways are extremely varied and depend on the type of cell involved as well as the external and internal conditions. A small sampling of responses is described below. Gene Expression 

Some signal transduction pathways regulate the transcription of RNA. Others regulate the translation of proteins from mRNA. An example of a protein that regulates translation in the nucleus is the MAP kinase ERK. ERK is activated in a phosphorylation cascade when epidermal growth factor (EGF) binds the EGF receptor (see [link] ). Upon phosphorylation, ERK enters the nucleus and activates a protein kinase that, in turn, regulates protein translation ( [link] ). ERK is a MAP kinase that activates translation when it is phosphorylated. ERK phosphorylates MNK1, which in turn phosphorylates eIF-4E, an elongation initiation factor that, with other initiation factors, is associated with mRNA. When eIF-4E becomes phosphorylated, the mRNA unfolds, allowing protein synthesis in the nucleus to begin. (See [link] for the phosphorylation pathway that activates ERK.) 

The second kind of protein with which PKC can interact is a protein that acts as an inhibitor. An inhibitor is a molecule that binds to a protein and prevents it from functioning or reduces its function. In this case, the inhibitor is a protein called I -B, which binds to the regulatory protein NF- B. (The symbol represents the Greek letter kappa.) When I -B is bound to NF- B, the complex cannot enter the nucleus of the cell, but when I -B is phosphorylated by PKC, it can no longer bind NF- B, and NF- B (a transcription factor) can enter the nucleus and initiate RNA transcription. In this case, the effect of phosphorylation is to inactivate an inhibitor and thereby activate the process of transcription. Increase in Cellular Metabolism 

The result of another signaling pathway affects muscle cells. The activation of -adrenergic receptors in muscle cells by adrenaline leads to an increase in cyclic AMP (cAMP) inside the cell. Also known as epinephrine, adrenaline is a hormone (produced by the adrenal gland attached to the kidney) that readies the body for short-term emergencies. Cyclic AMP activates PKA (protein kinase A), which in turn phosphorylates two enzymes. The first enzyme promotes the degradation of glycogen by activating intermediate glycogen phosphorylase kinase (GPK) that in turn activates glycogen phosphorylase (GP) that catabolizes glycogen into glucose. (Recall that your body converts excess glucose to glycogen for short-term storage. When energy is needed, glycogen is quickly reconverted to glucose.) Phosphorylation of the second enzyme, glycogen synthase (GS), inhibits its ability to form glycogen from glucose. In this manner, a muscle cell obtains a ready pool of glucose by activating its formation via glycogen degradation and by inhibiting the use of glucose to form glycogen, thus preventing a futile cycle of glycogen degradation and synthesis. The glucose is then available for use by the muscle cell in response to a sudden surge of adrenaline the fight or flight reflex. Cell Growth 

Cell signaling pathways also play a major role in cell division. Cells do not normally divide unless they are stimulated by signals from other cells. The ligands that promote cell growth are called growth factors . Most growth factors bind to cell-surface receptors that are linked to tyrosine kinases. These cell-surface receptors are called receptor tyrosine kinases (RTKs). Activation of RTKs initiates a signaling pathway that includes a G-protein called RAS, which activates the MAP kinase pathway described earlier. The enzyme MAP kinase then stimulates the expression of proteins that interact with other cellular components to initiate cell division. Cancer Biologist 

Cancer biologists study the molecular origins of cancer with the goal of developing new prevention methods and treatment strategies that will inhibit the growth of tumors without harming the normal cells of the body. As mentioned earlier, signaling pathways control cell growth. These signaling pathways are controlled by signaling proteins, which are, in turn, expressed by genes. Mutations in these genes can result in malfunctioning signaling proteins. This prevents the cell from regulating its cell cycle, triggering unrestricted cell division and cancer. The genes that regulate the signaling proteins are one type of oncogene which is a gene that has the potential to cause cancer. The gene encoding RAS is an oncogene that was originally discovered when mutations in the RAS protein were linked to cancer. Further studies have indicated that 30 percent of cancer cells have a mutation in the RAS gene that leads to uncontrolled growth. If left unchecked, uncontrolled cell division can lead tumor formation and metastasis, the growth of cancer cells in new locations in the body. 

Cancer biologists have been able to identify many other oncogenes that contribute to the development of cancer. For example, HER2 is a cell-surface receptor that is present in excessive amounts in 20 percent of human breast cancers. Cancer biologists realized that gene duplication led to HER2 overexpression in 25 percent of breast cancer patients and developed a drug called Herceptin (trastuzumab). Herceptin is a monoclonal antibody that targets HER2 for removal by the immune system. Herceptin therapy helps to control signaling through HER2. The use of Herceptin in combination with chemotherapy has helped to increase the overall survival rate of patients with metastatic breast cancer. 

More information on cancer biology research can be found at the National Cancer Institute website . Cell Death 

When a cell is damaged, superfluous, or potentially dangerous to an organism, a cell can initiate a mechanism to trigger programmed cell death, or apoptosis . Apoptosis allows a cell to die in a controlled manner that prevents the release of potentially damaging molecules from inside the cell. There are many internal checkpoints that monitor a cell s health; if abnormalities are observed, a cell can spontaneously initiate the process of apoptosis. However, in some cases, such as a viral infection or uncontrolled cell division due to cancer, the cell s normal checks and balances fail. External signaling can also initiate apoptosis. For example, most normal animal cells have receptors that interact with the extracellular matrix, a network of glycoproteins that provides structural support for cells in an organism. The binding of cellular receptors to the extracellular matrix initiates a signaling cascade within the cell. However, if the cell moves away from the extracellular matrix, the signaling ceases, and the cell undergoes apoptosis. This system keeps cells from traveling through the body and proliferating out of control, as happens with tumor cells that metastasize. 

Another example of external signaling that leads to apoptosis occurs in T-cell development. T-cells are immune cells that bind to foreign macromolecules and particles, and target them for destruction by the immune system. Normally, T-cells do not target self proteins (those of their own organism), a process that can lead to autoimmune diseases. In order to develop the ability to discriminate between self and non-self, immature T-cells undergo screening to determine whether they bind to so-called self proteins. If the T-cell receptor binds to self proteins, the cell initiates apoptosis to remove the potentially dangerous cell. 

Apoptosis is also essential for normal embryological development. In vertebrates, for example, early stages of development include the formation of web-like tissue between individual fingers and toes ( [link] ). During the course of normal development, these unneeded cells must be eliminated, enabling fully separated fingers and toes to form. A cell signaling mechanism triggers apoptosis, which destroys the cells between the developing digits. The histological section of a foot of a 15-day-old mouse embryo, visualized using light microscopy, reveals areas of tissue between the toes, which apoptosis will eliminate before the mouse reaches its full gestational age at 27 days. (credit: modification of work by Michal Ma as) Termination of the Signal Cascade 

The aberrant signaling often seen in tumor cells is proof that the termination of a signal at the appropriate time can be just as important as the initiation of a signal. One method of stopping a specific signal is to degrade the ligand or remove it so that it can no longer access its receptor. One reason that hydrophobic hormones like estrogen and testosterone trigger long-lasting events is because they bind carrier proteins. These proteins allow the insoluble molecules to be soluble in blood, but they also protect the hormones from degradation by circulating enzymes. 

Inside the cell, many different enzymes reverse the cellular modifications that result from signaling cascades. For example, phosphatases are enzymes that remove the phosphate group attached to proteins by kinases in a process called dephosphorylation. Cyclic AMP (cAMP) is degraded into AMP by phosphodiesterase , and the release of calcium stores is reversed by the Ca 2+ pumps that are located in the external and internal membranes of the cell. Activity 

Explain the mechanism by which a specific disease is caused by a defective signaling pathway. Then, investigate online how a specific drug works by blocking a signaling pathway. 

This activity is an application of Learning Objective 3.37, Science Practice 6.1, Learning Objective 3.39, and Science Practice 6.2 because the students are asked to justify the claim based on evidence that changes in signaling pathways can alter cellular response and cause disease, and explain how a specific drug can affect a signaling pathway. 

Another example is Parkinson s disease, in which the brain cells that make dopamine slowly die. Without dopamine, the cells that control movement cannot send messages to the muscles. The primary treatment helps increase dopamine levels in the brain by supplementing with L-dopa, a drug that converts to dopamine in the brain, or drugs that mimic dopamine and bind to the receptor. Like dopamine, serotonin is a neurotransmitter. It is linked to positive mood, emotion, and sleep. Most antidepressants block the reuptake or breakdown of serotonin and are called selective serotonin reuptake inhibitors (SSRIs). 

Stopping uncontrolled cell division is a major cancer research goal. The MAP kinase pathway stimulates the expression of proteins that interact with other cellular components to initiate cell division. By attacking proteins acting downstream in the MAP kinase, or MAPK pathway, cell division can be stopped or slowed down. One such protein is MEK. The Food and Drug Administration (FDA) recently approved one MEK inhibitor, trametinib (Mekinist ), for the treatment of certain patients with advanced melanoma. Section Summary 

The initiation of a signaling pathway is a response to external stimuli. This response can take many different forms, including protein synthesis, a change in the cell s metabolism, cell growth, or even cell death. Many pathways influence the cell by initiating gene expression, and the methods utilized are quite numerous. Some pathways activate enzymes that interact with DNA transcription factors. Others modify proteins and induce them to change their location in the cell. Depending on the status of the organism, cells can respond by storing energy as glycogen or fat, or making it available in the form of glucose. A signal transduction pathway allows muscle cells to respond to immediate requirements for energy in the form of glucose. Cell growth is almost always stimulated by external signals called growth factors. Uncontrolled cell growth leads to cancer, and mutations in the genes encoding protein components of signaling pathways are often found in tumor cells. Programmed cell death, or apoptosis, is important for removing damaged or unnecessary cells. The use of cellular signaling to organize the dismantling of a cell ensures that harmful molecules from the cytoplasm are not released into the spaces between cells, as they are in uncontrolled death, necrosis. Apoptosis also ensures the efficient recycling of the components of the dead cell. Termination of the cellular signaling cascade is very important so that the response to a signal is appropriate in both timing and intensity. Degradation of signaling molecules and dephosphorylation of phosphorylated intermediates of the pathway by phosphatases are two ways to terminate signals within the cell. Review Questions 

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[link] Glossary apoptosis programmed cell death growth factor ligand that binds to cell-surface receptors and stimulates cell growth inhibitor molecule that binds to a protein (usually an enzyme) and keeps it from functioning phosphatase enzyme that removes the phosphate group from a molecule that has been previously phosphorylated phosphodiesterase enzyme that degrades cAMP, producing AMP, to terminate signalingSignaling in Single-Celled Organisms Signaling in Single-Celled Organisms 

In this section, you will explore the following questions: How do single-celled yeasts use cell signaling to communicate with each other? How does quorum sensing allow some bacteria to form biofilms? Connection for AP Courses 

Cell signaling allows bacteria to respond to environmental cues, such as nutrient levels and quorum sensing (cell density). Yeasts are eukaryotes (fungi), and the components and processes found in yeast signals are similar to those of cell-surface receptor signals in multicellular organisms. For example, budding yeasts often release mating factors that enable them to participate in a process that is similar to sexual reproduction. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals. Essential Knowledge 3.D.1 Cell communication processes share common features that reflect a shared evolutionary history. Science Practice 1.5 The student can re-express key elements of natural phenomena across multiple representations in the domain. Learning Objective 3.36 The student is able to describe a model that expresses the key elements of signal transduction pathways by which a signal is converted to a cellular response. Essential Knowledge 3.D.1 Cell communication processes share common features that reflect a shared evolutionary history. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 3.37 The student is able to justify claims based on scientific evidence that changes in signal transduction pathways can alter cellular response. 

Unicellular organisms were assumed to communicate at a very primitive level, but current research reveals the existence more complex signaling systems. Examples of these forms of communication are the formation of biofilms and quorum sensing. Biofilms have received the attention of researchers only recently for several historical and technical reasons. Since the germ theory of disease was established, the interest had been to isolate and characterize pathogens, not to study microorganisms as a community. 

It is much easier to grow bacteria as pure cultures than replicate mixed populations biofilms, making the latter difficult to study in the laboratory setting. Such slime layers, previously considered haphazard assemblies of microorganisms, have been found to be highly organized ecosystems. The slime layer is made of extracellular polymers crisscrossed with channels for gases, nutrients, waste exchanges. Microbes attach to the solid substrate in a succession of populations. 

Quorum sensing exists both within a same species and across species. It allows microbes to behave as multicellular populations and coordinate responses. One such example is the expression of genes encoding toxins in Staphylococcus aureus . Dr. Bonnie Bassler presents quorum sensing communication in Vibrio harveyi in this Ted Talk . Her enthusiasm and clear explanations make this video a thoroughly engaging experience. This is an opportunity to show a strong female role model in science. 

Also available is this video clip : Quorum sensing molecules presented by Dr. Bonnie Bassler: 

And an animation on quorum sensing in Vibrio harveyi can be found here . 

Further reading: Painter, Kimberley L. et al. (2014). What role does the quorum-sensing accessory gene regulator system play during Staphylococcus aureus bacteremia? Trends in Microbiology 22:676 685 

Within-cell signaling allows bacteria to respond to environmental cues, such as nutrient levels, some single-celled organisms also release molecules to signal to each other. Signaling in Yeast 

Yeasts are eukaryotes (fungi), and the components and processes found in yeast signals are similar to those of cell-surface receptor signals in multicellular organisms. Budding yeasts ( [link] ) are able to participate in a process that is similar to sexual reproduction that entails two haploid cells (cells with one-half the normal number of chromosomes) combining to form a diploid cell (a cell with two sets of each chromosome, which is what normal body cells contain). In order to find another haploid yeast cell that is prepared to mate, budding yeasts secrete a signaling molecule called mating factor . When mating factor binds to cell-surface receptors in other yeast cells that are nearby, they stop their normal growth cycles and initiate a cell signaling cascade that includes protein kinases and GTP-binding proteins that are similar to G-proteins. Budding Saccharomyces cerevisiae yeast cells can communicate by releasing a signaling molecule called mating factor. In this micrograph, they are visualized using differential interference contrast microscopy, a light microscopy technique that enhances the contrast of the sample. Signaling in Bacteria 

Signaling in bacteria enables bacteria to monitor extracellular conditions, ensure that there are sufficient amounts of nutrients, and ensure that hazardous situations are avoided. There are circumstances, however, when bacteria communicate with each other. 

The first evidence of bacterial communication was observed in a bacterium that has a symbiotic relationship with Hawaiian bobtail squid. When the population density of the bacteria reaches a certain level, specific gene expression is initiated, and the bacteria produce bioluminescent proteins that emit light. Because the number of cells present in the environment (cell density) is the determining factor for signaling, bacterial signaling was named quorum sensing . In politics and business, a quorum is the minimum number of members required to be present to vote on an issue. 

Quorum sensing uses autoinducers as signaling molecules. Autoinducers are signaling molecules secreted by bacteria to communicate with other bacteria of the same kind. The secreted autoinducers can be small, hydrophobic molecules such as acyl-homoserine lactone, (AHL) or larger peptide-based molecules; each type of molecule has a different mode of action. When AHL enters target bacteria, it binds to transcription factors, which then switch gene expression on or off ( [link] ). The peptide autoinducers stimulate more complicated signaling pathways that include bacterial kinases. The changes in bacteria following exposure to autoinducers can be quite extensive. The pathogenic bacterium Pseudomonas aeruginosa has 616 different genes that respond to autoinducers. 

Autoinducers are small molecules or proteins produced by bacteria that regulate gene expression. 

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Some species of bacteria that use quorum sensing form biofilms, complex colonies of bacteria (often containing several species) that exchange chemical signals to coordinate the release of toxins that will attack the host. Bacterial biofilms ( [link] ) can sometimes be found on medical equipment; when biofilms invade implants such as hip or knee replacements or heart pacemakers, they can cause life-threatening infections. Think About It 

Why is signaling in multicellular organisms more complicated than signaling in single-celled organisms such as microbes? 

This question is an application of LO 3.36 and Science Practice 1.5 because students are describing and comparing models of signaling pathways in different types of organisms. Presumably, unicellular organisms do not need to coordinate the response of many tissue types and organs. Point out to students that the study of cell-to-cell communication in microorganisms is only beginning. Assuming that multicellular organisms have more complicated signaling may well be a premature conclusion. 

Cell-cell communication enables these (a) Staphylococcus aureus bacteria to work together to form a biofilm inside a hospital patient s catheter, seen here via scanning electron microscopy. S. aureus is the main cause of hospital-acquired infections. (b) Hawaiian bobtail squid have a symbiotic relationship with the bioluminescent bacteria Vibrio fischeri . The luminescence makes it difficult to see the squid from below because it effectively eliminates its shadow. In return for camouflage, the squid provides food for the bacteria. Free-living V. fischeri do not produce luciferase, the enzyme responsible for luminescence, but V. fischeri living in a symbiotic relationship with the squid do. Quorum sensing determines whether the bacteria should produce the luciferase enzyme. (credit a: modifications of work by CDC/Janice Carr; credit b: modifications of work by Cliff1066/Flickr) 

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Research on the details of quorum sensing has led to advances in growing bacteria for industrial purposes. Recent discoveries suggest that it may be possible to exploit bacterial signaling pathways to control bacterial growth; this process could replace or supplement antibiotics that are no longer effective in certain situations. 

Watch geneticist Bonnie Bassler discuss her discovery of quorum sensing in biofilm bacteria in squid. 

[link] Cellular Communication in Yeasts 

The first life on our planet consisted of single-celled prokaryotic organisms that had limited interaction with each other. While some external signaling occurs between different species of single-celled organisms, the majority of signaling within bacteria and yeasts concerns only other members of the same species. The evolution of cellular communication is an absolute necessity for the development of multicellular organisms, and this innovation is thought to have required approximately 2.5 billion years to appear in early life forms. 

Yeasts are single-celled eukaryotes, and therefore have a nucleus and organelles characteristic of more complex life forms. Comparisons of the genomes of yeasts, nematode worms, fruit flies, and humans illustrate the evolution of increasingly complex signaling systems that allow for the efficient inner workings that keep humans and other complex life forms functioning correctly. 

Kinases are a major component of cellular communication, and studies of these enzymes illustrate the evolutionary connectivity of different species. Yeasts have 130 types of kinases. More complex organisms such as nematode worms and fruit flies have 454 and 239 kinases, respectively. Of the 130 kinase types in yeast, 97 belong to the 55 subfamilies of kinases that are found in other eukaryotic organisms. The only obvious deficiency seen in yeasts is the complete absence of tyrosine kinases. It is hypothesized that phosphorylation of tyrosine residues is needed to control the more sophisticated functions of development, differentiation, and cellular communication used in multicellular organisms. 

Because yeasts contain many of the same classes of signaling proteins as humans, these organisms are ideal for studying signaling cascades. Yeasts multiply quickly and are much simpler organisms than humans or other multicellular animals. Therefore, the signaling cascades are also simpler and easier to study, although they contain similar counterparts to human signaling. 1 

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Watch this collection of interview clips with biofilm researchers in What Are Bacterial Biofilms? 

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Yeasts and multicellular organisms have similar signaling mechanisms. Yeasts use cell-surface receptors and signaling cascades to communicate information on mating with other yeast cells. The signaling molecule secreted by yeasts is called mating factor. 

Bacterial signaling is called quorum sensing. Bacteria secrete signaling molecules called autoinducers that are either small, hydrophobic molecules or peptide-based signals. The hydrophobic autoinducers, such as AHL, bind transcription factors and directly affect gene expression. The peptide-based molecules bind kinases and initiate signaling cascades in the cells. Review Questions 

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G. Manning, G.D. Plowman, T. Hunter, S. Sudarsanam, Evolution of Protein Kinase Signaling from Yeast to Man, Trends in Biochemical Sciences 27, no. 10 (2002): 514 520. Glossary autoinducer signaling molecule secreted by bacteria to communicate with other bacteria of its kind and others mating factor signaling molecule secreted by yeast cells to communicate to nearby yeast cells that they are available to mate and communicating their mating orientation quorum sensing method of cellular communication used by bacteria that informs them of the abundance of similar (or different) bacteria in the environmentIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for sup AP #174; /sup Courses" A sea urchin begins life as a single cell that (a) divides to form two cells, visible by scanning electron microscopy. After four rounds of cell division, (b) there are 16 cells, as seen in this SEM image. After many rounds of cell division, the individual develops into a complex, multicellular organism, as seen in this (c) mature sea urchin. (credit a: modification of work by Evelyn Spiegel, Louisa Howard; credit b: modification of work by Evelyn Spiegel, Louisa Howard; credit c: modification of work by Marco Busdraghi; scale-bar data from Matt Russell) 

A human, as well as every sexually reproducing organism, begins life as a fertilized egg (embryo) or zygote. Trillions of cell divisions subsequently occur in a controlled manner to produce a complex, multicellular human. In other words, that original single cell is the ancestor of every other cell in the body. Once a being is fully grown, cell reproduction is still necessary to repair or regenerate tissues. For example, new blood and skin cells are constantly being produced. All multicellular organisms use cell division for growth, maintenance, and repair of tissues. Cell division is tightly regulated, and the occasional failure of regulation can have life-threatening consequences. Single-celled organisms use cell division as their method of reproduction. 

Not all cells in the body reproduce to repair tissues. Most nerve tissues, for example, are not capable of regeneration. This means people who have damaged their nerves or nervous system are often left paralyzed. 

However, this may change in the future; scientists have discovered a new drug called intracellular signal peptide (ISP), which helps nerve cells regenerate in rats. It works by blocking an enzyme that causes scar tissue in damaged nerve cells allowing the nervous system a chance to repair itself. The full research study is located here . 

Before students begin this chapter, it is useful to review these concepts: the differences between prokaryotes and eukaryotes; cell structure; cell signaling; cell growth and cell death.Cell Division Cell Division 

In this section, you will explore the following question: What is the relationship between chromosomes, genes, and traits in prokaryotes and eukaryotes? Connection for AP Courses 

All organisms, from bacteria to complex animals, must be able to store, retrieve, and transmit genetic information to continue life. In later chapters, we will explore how a cell s genetic information encoded in DNA, its genome, is replicated and passed to the next generation to direct the production of proteins, determining an organism s traits. Prokaryotes have single circular chromosome of DNA, whereas eukaryotes have multiple, linear chromosomes composed of chromatin (DNA wrapped around a histone protein) surrounded by a nuclear membrane. Cell division involves both mitosis, the division of the chromosomes, and cytokinesis, the division of the cytoplasm. Human somatic cells consist of 46 chromosomes 22 pairs of autosomal chromosomes and a pair of sex chromosomes. Prior to mitosis, each chromosome is duplicated to ensure that daughter cells receive the full amount of hereditary material contributed by both parents. The total number of autosomal chromosomes is referred to as the diploid (2 n ) number. (In the next chapter, we will study meiosis, the second type of cell division in sexually reproducing organisms.) 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA, and in some cases, RNA are the primary sources of heritable information. 

Ask students to bring in a picture of themselves as a baby, and a current picture. Ask them how do we change from a baby to an adult? What process is required to generate new cells? 

The continuity of life from one cell to another has its foundation in the reproduction of cells by way of the cell cycle. The cell cycle is an orderly sequence of events that describes the stages of a cell s life from the division of a single parent cell to the production of two new daughter cells. The mechanisms involved in the cell cycle are highly regulated. Genomic DNA 

Before discussing the steps a cell must undertake to replicate, a deeper understanding of the structure and function of a cell s genetic information is necessary. A cell s DNA, packaged as a double-stranded DNA molecule, is called its genome . In prokaryotes, the genome is composed of a single, double-stranded DNA molecule in the form of a loop or circle ( [link] ). The region in the cell containing this genetic material is called a nucleoid. Some prokaryotes also have smaller loops of DNA called plasmids that are not essential for normal growth. Bacteria can exchange these plasmids with other bacteria, sometimes receiving beneficial new genes that the recipient can add to their chromosomal DNA. Antibiotic resistance is one trait that often spreads through a bacterial colony through plasmid exchange. Prokaryotes, including bacteria and archaea, have a single, circular chromosome located in a central region called the nucleoid. 

In eukaryotes, the genome consists of several double-stranded linear DNA molecules ( [link] ). Each species of eukaryotes has a characteristic number of chromosomes in the nuclei of its cells. Human body cells have 46 chromosomes, while human gametes (sperm or eggs) have 23 chromosomes each. A typical body cell, or somatic cell, contains two matched sets of chromosomes, a configuration known as diploid . The letter n is used to represent a single set of chromosomes; therefore, a diploid organism is designated 2 n . Human cells that contain one set of chromosomes are called gametes, or sex cells; these are eggs and sperm, and are designated 1n , or haploid . There are 23 pairs of homologous chromosomes in a female human somatic cell. The condensed chromosomes are viewed within the nucleus (top), removed from a cell in mitosis and spread out on a slide (right), and artificially arranged according to length (left); an arrangement like this is called a karyotype. In this image, the chromosomes were exposed to fluorescent stains for differentiation of the different chromosomes. A method of staining called chromosome painting employs fluorescent dyes that highlight chromosomes in different colors. (credit: National Human Genome Project/NIH) 

Matched pairs of chromosomes in a diploid organism are called homologous ( same knowledge ) chromosomes . Homologous chromosomes are the same length and have specific nucleotide segments called genes in exactly the same location, or locus . Genes, the functional units of chromosomes, determine specific characteristics by coding for specific proteins. Traits are the variations of those characteristics. For example, hair color is a characteristic with traits that are blonde, brown, or black. 

Each copy of a homologous pair of chromosomes originates from a different parent; therefore, the genes themselves are not identical. The variation of individuals within a species is due to the specific combination of the genes inherited from both parents. Even a slightly altered sequence of nucleotides within a gene can result in an alternative trait. For example, there are three possible gene sequences on the human chromosome that code for blood type: sequence A, sequence B, and sequence O. Because all diploid human cells have two copies of the chromosome that determines blood type, the blood type (the trait) is determined by which two versions of the marker gene are inherited. It is possible to have two copies of the same gene sequence on both homologous chromosomes, with one on each (for example, AA, BB, or OO), or two different sequences, such as AB. 

Minor variations of traits, such as blood type, eye color, and handedness, contribute to the natural variation found within a species. However, if the entire DNA sequence from any pair of human homologous chromosomes is compared, the difference is less than one percent. The sex chromosomes, X and Y, are the single exception to the rule of homologous chromosome uniformity: Other than a small amount of homology that is necessary to accurately produce gametes, the genes found on the X and Y chromosomes are different. Eukaryotic Chromosomal Structure and Compaction 

If the DNA from all 46 chromosomes in a human cell nucleus was laid out end to end, it would measure approximately two meters; however, its diameter would be only 2 nm. Considering that the size of a typical human cell is about 10 m (100,000 cells lined up to equal one meter), DNA must be tightly packaged to fit in the cell s nucleus. At the same time, it must also be readily accessible for the genes to be expressed. During some stages of the cell cycle, the long strands of DNA are condensed into compact chromosomes. There are a number of ways that chromosomes are compacted. 

In the first level of compaction, short stretches of the DNA double helix wrap around a core of eight histone proteins at regular intervals along the entire length of the chromosome ( [link] ). The DNA-histone complex is called chromatin. The beadlike, histone DNA complex is called a nucleosome , and DNA connecting the nucleosomes is called linker DNA. A DNA molecule in this form is about seven times shorter than the double helix without the histones, and the beads are about 10 nm in diameter, in contrast with the 2-nm diameter of a DNA double helix. The next level of compaction occurs as the nucleosomes and the linker DNA between them are coiled into a 30-nm chromatin fiber. This coiling further shortens the chromosome so that it is now about 50 times shorter than the extended form. In the third level of packing, a variety of fibrous proteins is used to pack the chromatin. These fibrous proteins also ensure that each chromosome in a non-dividing cell occupies a particular area of the nucleus that does not overlap with that of any other chromosome (see the top image in [link] ). Double-stranded DNA wraps around histone proteins to form nucleosomes that have the appearance of beads on a string. The nucleosomes are coiled into a 30-nm chromatin fiber. When a cell undergoes mitosis, the chromosomes condense even further. 

DNA replicates in the S phase of interphase. After replication, the chromosomes are composed of two linked sister chromatids . When fully compact, the pairs of identically packed chromosomes are bound to each other by cohesin proteins. The connection between the sister chromatids is closest in a region called the centromere . The conjoined sister chromatids, with a diameter of about 1 m, are visible under a light microscope. The centromeric region is highly condensed and thus will appear as a constricted area. 

This animation illustrates the different levels of chromosome packing. 

[link] Think About It 

What is the relationship between a genome and chromosomes? 

This question is an application of Learning Objective 3.1 and Science Practice 6.5 because the student is explaining the link between chromosomes and DNA as the source of hereditary information. 

Answer 

The genome consists of the sum total of an organism s chromosomes. Each chromosome contains hundreds and sometimes thousands of genes, segments of DNA that code for a polypeptide or RNA, and a large amount of DNA with no known function. This noncoding DNA, in the past called junk DNA, accounts for approximately 98% of the human genome. Noncoding DNA includes introns. Some noncoding DNA controls the expression of nearby genes, but most of it has unknown functions yet to be discovered. Section Summary 

Prokaryotes have a single circular chromosome composed of double-stranded DNA, whereas eukaryotes have multiple, linear chromosomes composed of chromatin surrounded by a nuclear membrane. The 46 chromosomes of human somatic cells are composed of 22 pairs of autosomes (matched pairs) and a pair of sex chromosomes, which may or may not be matched. This is the 2 n or diploid state. Human gametes have 23 chromosomes or one complete set of chromosomes; a set of chromosomes is complete with either one of the sex chromosomes. This is the n or haploid state. Genes are segments of DNA that code for a specific protein. An organism s traits are determined by the genes inherited from each parent. Duplicated chromosomes are composed of two sister chromatids. Chromosomes are compacted using a variety of mechanisms during certain stages of the cell cycle. Several classes of protein are involved in the organization and packing of the chromosomal DNA into a highly condensed structure. The condensing complex compacts chromosomes, and the resulting condensed structure is necessary for chromosomal segregation during mitosis. Review Questions 

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[link] Glossary cell cycle ordered sequence of events that a cell passes through between one cell division and the next centromere region at which sister chromatids are bound together; a constricted area in condensed chromosomes chromatid single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere diploid cell, nucleus, or organism containing two sets of chromosomes (2 n ) gamete haploid reproductive cell or sex cell (sperm, pollen grain, or egg) gene physical and functional unit of heredity, a sequence of DNA that codes for a protein. genome total genetic information of a cell or organism haploid cell, nucleus, or organism containing one set of chromosomes ( n ) histone one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes homologous chromosomes chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent locus position of a gene on a chromosome nucleosome subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteinsThe Cell Cycle The Cell Cycle 

In this section, you will explore the following questions: What processes occur during the three stages of interphase? How do the chromosomes behave during the mitotic phase? Connection for AP Courses 

The cell cycle describes an orderly sequence of events that are highly regulated. In eukaryotes, the cell cycle consists of a long preparatory period (interphase) followed by mitosis and cytokinesis. Interphase is divided into three phases: Gap 1 (G 1 ), DNA synthesis (S), and Gap 2 (G 2 ). Interphase represents the portion of the cell cycle between nuclear divisions. During this phase, preparations are made for division that include growth, duplication of most cellular contents, and replication of DNA. The cell s DNA is replicated during the S stage. (We will study the details of DNA replication in the chapter on DNA structure and function.) Following the G 2 stage of interphase, the cell begins mitosis, the process of active division by which duplicated chromosomes (chromatids) attach to spindle fibers, align themselves along the equator of the cell, and then separate from each other. 

Following mitosis, the cell undergoes cytokinesis, the splitting of the parent cell into two daughter cells, complete with a full complement of genetic material. In animal cells, daughter cells are separated by an actin ring, whereas plant cells are separated by the cell plate, which will grow into a new cell wall. Sometimes cells enter a Gap zero (G 0 ) phase, during which they do not actively prepare to divide; the G 0 phase can be temporary until triggered by an external signal to enter G 1 , or permanent, such as mature cardiac muscle cells and nerve cells. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework, as shown in the tables. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.7 The student can make predictions about natural phenomena occurring during the cell cycle. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.8 The student can describe the events that occur in the cell cycle. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.3 The student can articulate the reasons that scientific explanations and theories are refined or replaced. Learning Objective 3.9 The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 3.11 The student is able to evaluate evidence provided by data sets to support the claim that heritable information is passed from one generation to another generation through mitosis. 

Discuss with students the difference between diploid and haploid cells. Show students a graphic of the difference. 

Discuss with students how in mitosis, the ploidy of the cell remains constant. In a cell culture of human somatic cells, all of the cells will be diploid. In contrast the DNA content, the amount of DNA in a cell culture will change as the cells replicate (undergo S-phase and replicate their DNA). In relative amounts, the initial amount of DNA is considered to be 1x, after S-phase it will be 2x, and so on. More information on the methods used by scientists to track ploidy can be found here . 

Introduce mitosis using visuals such as this video . 

Show Crash Course or Bozeman Videos such as Cell Cycle, Mitosis Meiosis , Development: Timing Coordination , Mechanisms of Timing Control , DNA, Hot Pockets, The Longest Word Ever: Crash Course Biology #11 , and HHMI: Mix 1 

Students may think that interphase is a resting phase, where no events occur. Remind students that cells are metabolically active in this phase. Cells in G 0 phase are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle. Some cells enter G 0 temporarily until an external signal triggers the onset of G 1 . Other cells that never or rarely divide, such as mature cardiac muscle and nerve cells, remain in G 0 permanently. 

In addition, students may not realize that the events of mitosis are continuous, and the organization into discrete stages is for convenience. Show students a time lapse video to illustrate this, such as found here . 

The stages of the cell cycle can be taught using the images available here . 

The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produces two identical (clone) cells. The cell cycle has two major phases: interphase and the mitotic phase ( [link] ). During interphase , the cell grows and DNA is replicated. During the mitotic phase , the replicated DNA and cytoplasmic contents are separated, and the cell divides. The cell cycle consists of interphase and the mitotic phase. During interphase, the cell grows and the nuclear DNA is duplicated. Interphase is followed by the mitotic phase. During the mitotic phase, the duplicated chromosomes are segregated and distributed into daughter nuclei. The cytoplasm is usually divided as well, resulting in two daughter cells. Interphase 

During interphase, the cell undergoes normal growth processes while also preparing for cell division. In order for a cell to move from interphase into the mitotic phase, many internal and external conditions must be met. The three stages of interphase are called G 1 , S, and G 2 . G 1 Phase (First Gap) 

The first stage of interphase is called the G 1 phase (first gap) because, from a microscopic aspect, little change is visible. However, during the G 1 stage, the cell is quite active at the biochemical level. The cell is accumulating the building blocks of chromosomal DNA and the associated proteins as well as accumulating sufficient energy reserves to complete the task of replicating each chromosome in the nucleus. S Phase (Synthesis of DNA) 

Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase , DNA replication can proceed through the mechanisms that result in the formation of identical pairs of DNA molecules sister chromatids that are firmly attached to the centromeric region. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle , the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the centrioles , which are at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of other eukaryotic species, such as plants and most fungi. G 2 Phase (Second Gap) 

In the G 2 phase , the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. There may be additional cell growth during G 2 . The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis. The Mitotic Phase 

The mitotic phase is a multistep process during which the duplicated chromosomes are aligned, separated, and move into two new, identical daughter cells. The first portion of the mitotic phase is called karyokinesis , or nuclear division. The second portion of the mitotic phase, called cytokinesis, is the physical separation of the cytoplasmic components into the two daughter cells. 

Revisit the stages of mitosis at this site . 

[link] Karyokinesis (Mitosis) 

Karyokinesis, also known as mitosis , is divided into a series of phases prophase, prometaphase, metaphase, anaphase, and telophase that result in the division of the cell nucleus ( [link] ). Karyokinesis is also called mitosis. 

These budding plants demonstrate asexual reproduction, one of the main purposes of mitosis. The other two purposes are growth and repair. 

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Karyokinesis (or mitosis) is divided into five stages prophase, prometaphase, metaphase, anaphase, and telophase. The pictures at the bottom were taken by fluorescence microscopy (hence, the black background) of cells artificially stained by fluorescent dyes: blue fluorescence indicates DNA (chromosomes) and green fluorescence indicates microtubules (spindle apparatus). (credit mitosis drawings : modification of work by Mariana Ruiz Villareal; credit micrographs : modification of work by Roy van Heesbeen; credit cytokinesis micrograph : Wadsworth Center/New York State Department of Health; scale-bar data from Matt Russell) 

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During prophase , the first phase, the nuclear envelope starts to dissociate into small vesicles, and the membranous organelles (such as the Golgi complex or Golgi apparatus, and endoplasmic reticulum), fragment and disperse toward the periphery of the cell. The nucleolus disappears (disperses). The centrosomes begin to move to opposite poles of the cell. Microtubules that will form the mitotic spindle extend between the centrosomes, pushing them farther apart as the microtubule fibers lengthen. The sister chromatids begin to coil more tightly with the aid of condensin proteins and become visible under a light microscope. 

During prometaphase , the first change phase, many processes that were begun in prophase continue to advance. The remnants of the nuclear envelope fragment. The mitotic spindle continues to develop as more microtubules assemble and stretch across the length of the former nuclear area. Chromosomes become more condensed and discrete. Each sister chromatid develops a protein structure called a kinetochore in the centromeric region ( [link] ). The proteins of the kinetochore attract and bind mitotic spindle microtubules. As the spindle microtubules extend from the centrosomes, some of these microtubules come into contact with and firmly bind to the kinetochores. Once a mitotic fiber attaches to a chromosome, the chromosome will be oriented until the kinetochores of sister chromatids face the opposite poles. Eventually, all the sister chromatids will be attached via their kinetochores to microtubules from opposing poles. Spindle microtubules that do not engage the chromosomes are called polar microtubules. These microtubules overlap each other midway between the two poles and contribute to cell elongation. Astral microtubules are located near the poles, aid in spindle orientation, and are required for the regulation of mitosis. During prometaphase, mitotic spindle microtubules from opposite poles attach to each sister chromatid at the kinetochore. In anaphase, the connection between the sister chromatids breaks down, and the microtubules pull the chromosomes toward opposite poles. 

During metaphase , the change phase, all the chromosomes are aligned in a plane called the metaphase plate , or the equatorial plane, midway between the two poles of the cell. The sister chromatids are still tightly attached to each other by cohesin proteins. At this time, the chromosomes are maximally condensed. 

During anaphase , the upward phase, the cohesin proteins degrade, and the sister chromatids separate at the centromere. Each chromatid, now called a chromosome, is pulled rapidly toward the centrosome to which its microtubule is attached. The cell becomes visibly elongated (oval shaped) as the polar microtubules slide against each other at the metaphase plate where they overlap. 

During telophase , the distance phase, the chromosomes reach the opposite poles and begin to decondense (unravel), relaxing into a chromatin configuration. The mitotic spindles are depolymerized into tubulin monomers that will be used to assemble cytoskeletal components for each daughter cell. Nuclear envelopes form around the chromosomes, and nucleosomes appear within the nuclear area. Cytokinesis 

Cytokinesis , or cell motion, is the second main stage of the mitotic phase during which cell division is completed via the physical separation of the cytoplasmic components into two daughter cells. Division is not complete until the cell components have been apportioned and completely separated into the two daughter cells. Although the stages of mitosis are similar for most eukaryotes, the process of cytokinesis is quite different for eukaryotes that have cell walls, such as plant cells. 

In cells such as animal cells that lack cell walls, cytokinesis follows the onset of anaphase. A contractile ring composed of actin filaments forms just inside the plasma membrane at the former metaphase plate. The actin filaments pull the equator of the cell inward, forming a fissure. This fissure, or crack, is called the cleavage furrow . The furrow deepens as the actin ring contracts, and eventually the membrane is cleaved in two ( [link] ). 

In plant cells, a new cell wall must form between the daughter cells. During interphase, the Golgi apparatus accumulates enzymes, structural proteins, and glucose molecules prior to breaking into vesicles and dispersing throughout the dividing cell. During telophase, these Golgi vesicles are transported on microtubules to form a phragmoplast (a vesicular structure) at the metaphase plate. There, the vesicles fuse and coalesce from the center toward the cell walls; this structure is called a cell plate . As more vesicles fuse, the cell plate enlarges until it merges with the cell walls at the periphery of the cell. Enzymes use the glucose that has accumulated between the membrane layers to build a new cell wall. The Golgi membranes become parts of the plasma membrane on either side of the new cell wall ( [link] ). During cytokinesis in animal cells, a ring of actin filaments forms at the metaphase plate. The ring contracts, forming a cleavage furrow, which divides the cell in two. In plant cells, Golgi vesicles coalesce at the former metaphase plate, forming a phragmoplast. A cell plate formed by the fusion of the vesicles of the phragmoplast grows from the center toward the cell walls, and the membranes of the vesicles fuse to form a plasma membrane that divides the cell in two. Activity Use a set of pipe cleaners (or other materials as directed by your teacher) that you can use to model chromosomes during mitosis and meiosis: Each of the pipe cleaners represents a single, unreplicated chromosome. Each chromosome should differ in size, as they do in most organisms. Assume that your dividing cell contains 3 chromosomes: numbered chromosome 1, 2, and 3. Using both members of each homologous pair for chromosomes 1 3, model how the chromosomes would appear in a cell that had just finished the S phase of the cell cycle. Once your teacher has approved your model, have one member of your group document the model by photographing or drawing it. Now, repeat step 2 but show the cell at metaphase during mitosis. Finally, model the two daughter cells that will result from mitosis. Again, have one member of your group document the model. Repeat steps 2 5 for both meiosis I and meiosis II. Remember that you should have four daughter cells at the end of meiosis II. Also remember to ask your teacher for approval and document your model before moving on to the next phase of meiosis. Exchange/ copy all of the drawings or photographs that your group took of your models. As a group or individually (as directed by your teacher) create a report to turn in that labels and explain each picture of your model. An organism s ploidy count is the total number of chromosome sets contained in each body cell. Most organisms have a ploidy level of 2, meaning that they have two sets of chromosomes due to presence of homologous pairs. However, some plants are multiploid, meaning they can have ploidy levels greater than 2. The table shows possible multiploid levels of some common crop plants. Common name Multiploid chromosome count Normal chromosome count Bananas 33 11 Potatoes 48 12 Wheat 42 7 Sugar cane 80 10 

Analyze the data with a partner of in a group as directed by your teacher. On a separate sheet of paper, answer the following questions. How does the multiploid count of the crop plants relate to their normal chromosome count? Explain the basis for the relationship you described in part a, in terms of what occurs to chromosomes during replication and meiosis. Give one additional example of a possible multiploid chromosome count for each species in the table above. Think About It 

Chemotherapy drugs such as vincristine and colchicines disrupt mitosis by binding to tubulin (the subunit of microtubules) and interfering with microtubule assembly and disassembly. What mitotic structure is targeted by these drugs, and what effect would this have on cell division? 

The first activity is an application of Learning Objective 3.8 and Science Practice 1.2 because students are modelling steps of the cell cycle, including mitosis and meiosis. A variety of materials can be used to represent chromosomes in the model as long as the students can easily distinguish between the three chromosomes (such as by having different-sized pipe cleaners) as well as distinguish between homologs (such as by using two colors of pipe cleaner). Be sure to provide enough chromosomes to represent sister chromatids in both the mitosis and meiosis models. The critical point to stress is that, in modelling mitosis, students should place homologous chromosomes (each with a sister chromatid) above and below each other during metaphase, ensuring a sister chromosome from each homolog enters each daughter cell. Conversely, in metaphase I of meiosis, the homologous chromosomes (each with a sister chromatid) will pair together side-by-side so that each cell only receives one of the two homologs. 

The second activity is an application of Learning Objective 3.11 and Science Practice 5.3 because students are using their knowledge of meiosis to explain and predict possible ploidy levels in crop plants. Students should work in pairs or as a group. 

An expanded lab investigation for mitosis and meiosis, involving studying onion cells undergoing mitosis (part 2), and karyotype analysis (part 3) is available from the College Board s AP Biology Investigative Labs: An Inquiry-Based Approach in Investigation 7 . Possible Answer The multiploid count is always a whole-number multiple of the normal chromosome count. Before meiosis (and mitosis) all of an organism s chromosomes are replicated before any segregation takes place. Therefore, ploidy levels will always involve whole-number multiples of the original chromosome levels. Answers will vary but all answers should be whole-number multiples of the normal chromosome numbers. 

The Think About It question is an application of Learning Objective 3.7 and Science Practice 6.4 because the student must be able to describe the events that occur in the cell cycle before you can make a prediction about the effects of a disruption in mitosis. Possible Answer 

The mitotic spindle is formed of microtubules. Microtubules are polymers of the protein tubulin; therefore, it is the mitotic spindle that is disrupted by these drugs. Without a functional mitotic spindle, the chromosomes will not be sorted or separated during mitosis. The cell will arrest in mitosis and die. G 0 Phase 

Not all cells adhere to the classic cell cycle pattern in which a newly formed daughter cell immediately enters the preparatory phases of interphase, closely followed by the mitotic phase. Cells in G 0 phase are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle. Some cells enter G 0 temporarily until an external signal triggers the onset of G 1 . Other cells that never or rarely divide, such as mature cardiac muscle and nerve cells, remain in G 0 permanently. 

Determine the Time Spent in Cell Cycle Stages 

Problem : How long does a cell spend in interphase compared to each stage of mitosis? 

Background : A prepared microscope slide of blastula cross-sections will show cells arrested in various stages of the cell cycle. It is not visually possible to separate the stages of interphase from each other, but the mitotic stages are readily identifiable. If 100 cells are examined, the number of cells in each identifiable cell cycle stage will give an estimate of the time it takes for the cell to complete that stage. 

Problem Statement : Given the events included in all of interphase and those that take place in each stage of mitosis, estimate the length of each stage based on a 24-hour cell cycle. Before proceeding, state your hypothesis. 

Test your hypothesis : Test your hypothesis by doing the following: Place a fixed and stained microscope slide of whitefish blastula cross-sections under the scanning objective of a light microscope. Locate and focus on one of the sections using the scanning objective of your microscope. Notice that the section is a circle composed of dozens of closely packed individual cells. Switch to the low-power objective and refocus. With this objective, individual cells are visible. 

Switch to the high-power objective and slowly move the slide left to right, and up and down to view all the cells in the section ( [link] ). As you scan, you will notice that most of the cells are not undergoing mitosis but are in the interphase period of the cell cycle. 

Slowly scan whitefish blastula cells with the high-power objective as illustrated in image (a) to identify their mitotic stage. (b) A microscopic image of the scanned cells is shown. (credit micrograph : modification of work by Linda Flora; scale-bar data from Matt Russell) Practice identifying the various stages of the cell cycle, using the drawings of the stages as a guide ( [link] ). Once you are confident about your identification, begin to record the stage of each cell you encounter as you scan left to right, and top to bottom across the blastula section. Keep a tally of your observations and stop when you reach 100 cells identified. The larger the sample size (total number of cells counted), the more accurate the results. If possible, gather and record group data prior to calculating percentages and making estimates. 

Record your observations : Make a table similar to [link] in which you record your observations. Results of Cell Stage Identification Phase or Stage Individual Totals Group Totals Percent Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Totals 100 100 100 percent 

Analyze your data/report your results : To find the length of time whitefish blastula cells spend in each stage, multiply the percent (recorded as a decimal) by 24 hours. Make a table similar to [link] to illustrate your data. Estimate of Cell Stage Length Phase or Stage Percent (as Decimal) Time in Hours Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Section Summary 

The cell cycle is an orderly sequence of events. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages. In eukaryotes, the cell cycle consists of a long preparatory period, called interphase. Interphase is divided into G 1 , S, and G 2 phases. The mitotic phase begins with karyokinesis (mitosis), which consists of five stages: prophase, prometaphase, metaphase, anaphase, and telophase. The final stage of the mitotic phase is cytokinesis, during which the cytoplasmic components of the daughter cells are separated either by an actin ring (animal cells) or by cell plate formation (plant cells). Review Questions 

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[link] Glossary anaphase stage of mitosis during which sister chromatids are separated from each other cell cycle ordered series of events involving cell growth and cell division that produces two new daughter cells cell plate structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells centriole rod-like structure constructed of microtubules at the center of each animal cell centrosome cleavage furrow constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division condensin proteins that help sister chromatids coil during prophase cytokinesis division of the cytoplasm following mitosis that forms two daughter cells. G 0 phase distinct from the G 1 phase of interphase; a cell in G 0 is not preparing to divide G 1 phase (also, first gap) first phase of interphase centered on cell growth during mitosis G 2 phase (also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis interphase period of the cell cycle leading up to mitosis; includes G 1 , S, and G 2 phases (the interim period between two consecutive cell divisions karyokinesis mitotic nuclear division kinetochore protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase metaphase plate equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase metaphase stage of mitosis during which chromosomes are aligned at the metaphase plate mitosis (also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase mitotic phase period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis mitotic spindle apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis prometaphase stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores prophase stage of mitosis during which chromosomes condense and the mitotic spindle begins to form quiescent refers to a cell that is performing normal cell functions and has not initiated preparations for cell division S phase second, or synthesis, stage of interphase during which DNA replication occurs telophase stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelopeControl of the Cell Cycle Control of the Cell Cycle 

In this section, you will explore the following questions: What are examples of internal and external mechanisms that control the cell cycle? What molecules are involved in controlling the cell cycle through positive and negative regulation? Connection for AP Courses 

Each step of the cell cycle is closely monitored by external signals and internal controls called checkpoints. There are three major checkpoints in the cell cycle: one near the end of G 1 , a second at the G 2 /M transition, and the third during metaphase. Growth factor proteins arriving at the dividing cell s plasma membrane can trigger the cell to begin dividing. Cyclins and cyclin-dependent kinases (Cdks) are internal molecular signals that regulate cell transitions through the various checkpoints. Passage through the G 1 checkpoint makes sure that the cell is ready for DNA replication in the S stage of interphase; passage through the G 2 checkpoint triggers the separation of chromatids during mitosis. Positive regulator molecules like the cyclins and Cdks allow the cell cycle to advance to the next stage; negative regulator molecules, such as tumor suppressor proteins, monitor cellular conditions and can halt the cycle until specific requirements are met. Errors in the regulation of the cell cycle can cause cancer, which is characterized by uncontrolled cell division. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework, as shown in the tables. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.7 The student can make predictions about natural phenomena occurring during the cell cycle. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.8 The student can describe the events that occur in the cell cycle. 

Introduce the topic of control of the cell cycle using visuals such as this video . 

The length of the cell cycle is highly variable, even within the cells of a single organism. In humans, the frequency of cell turnover ranges from a few hours in early embryonic development, to an average of two to five days for epithelial cells, and to an entire human lifetime spent in G 0 by specialized cells, such as cortical neurons or cardiac muscle cells. There is also variation in the time that a cell spends in each phase of the cell cycle. When fast-dividing mammalian cells are grown in culture (outside the body under optimal growing conditions), the length of the cycle is about 24 hours. In rapidly dividing human cells with a 24-hour cell cycle, the G 1 phase lasts approximately nine hours, the S phase lasts 10 hours, the G 2 phase lasts about four and one-half hours, and the M phase lasts approximately one-half hour. In early embryos of fruit flies, the cell cycle is completed in about eight minutes. The timing of events in the cell cycle is controlled by mechanisms that are both internal and external to the cell. Regulation of the Cell Cycle by External Events 

Both the initiation and inhibition of cell division are triggered by events external to the cell when it is about to begin the replication process. An event may be as simple as the death of a nearby cell or as sweeping as the release of growth-promoting hormones, such as human growth hormone (HGH). A lack of HGH can inhibit cell division, resulting in dwarfism, whereas too much HGH can result in gigantism. Crowding of cells can also inhibit cell division. Another factor that can initiate cell division is the size of the cell; as a cell grows, it becomes inefficient due to its decreasing surface-to-volume ratio. The solution to this problem is to divide. 

Whatever the source of the message, the cell receives the signal, and a series of events within the cell allows it to proceed into interphase. Moving forward from this initiation point, every parameter required during each cell cycle phase must be met or the cycle cannot progress. Regulation at Internal Checkpoints 

It is essential that the daughter cells produced be exact duplicates of the parent cell. Mistakes in the duplication or distribution of the chromosomes lead to mutations that may be passed forward to every new cell produced from an abnormal cell. To prevent a compromised cell from continuing to divide, there are internal control mechanisms that operate at three main cell cycle checkpoints . A checkpoint is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable. These checkpoints occur near the end of G 1 , at the G 2 /M transition, and during metaphase ( [link] ). The cell cycle is controlled at three checkpoints. The integrity of the DNA is assessed at the G 1 checkpoint. Proper chromosome duplication is assessed at the G 2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint. The G 1 Checkpoint 

The G 1 checkpoint determines whether all conditions are favorable for cell division to proceed. The G 1 checkpoint, also called the restriction point (in yeast), is a point at which the cell irreversibly commits to the cell division process. External influences, such as growth factors, play a large role in carrying the cell past the G 1 checkpoint. In addition to adequate reserves and cell size, there is a check for genomic DNA damage at the G 1 checkpoint. A cell that does not meet all the requirements will not be allowed to progress into the S phase. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into G 0 and await further signals when conditions improve. The G 2 Checkpoint 

The G 2 checkpoint bars entry into the mitotic phase if certain conditions are not met. As at the G 1 checkpoint, cell size and protein reserves are assessed. However, the most important role of the G 2 checkpoint is to ensure that all of the chromosomes have been replicated and that the replicated DNA is not damaged. If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA. The M Checkpoint 

The M checkpoint occurs near the end of the metaphase stage of karyokinesis. The M checkpoint is also known as the spindle checkpoint, because it determines whether all the sister chromatids are correctly attached to the spindle microtubules. Because the separation of the sister chromatids during anaphase is an irreversible step, the cycle will not proceed until the kinetochores of each pair of sister chromatids are firmly anchored to at least two spindle fibers arising from opposite poles of the cell. 

Watch what occurs at the G 1 , G 2 , and M checkpoints by visiting this website to see an animation of the cell cycle. 

[link] Regulator Molecules of the Cell Cycle 

In addition to the internally controlled checkpoints, there are two groups of intracellular molecules that regulate the cell cycle. These regulatory molecules either promote progress of the cell to the next phase (positive regulation) or halt the cycle (negative regulation). Regulator molecules may act individually, or they can influence the activity or production of other regulatory proteins. Therefore, the failure of a single regulator may have almost no effect on the cell cycle, especially if more than one mechanism controls the same event. Conversely, the effect of a deficient or non-functioning regulator can be wide-ranging and possibly fatal to the cell if multiple processes are affected. Positive Regulation of the Cell Cycle 

Two groups of proteins, called cyclins and cyclin-dependent kinases (Cdks), are responsible for the progress of the cell through the various checkpoints. The levels of the four cyclin proteins fluctuate throughout the cell cycle in a predictable pattern ( [link] ). Increases in the concentration of cyclin proteins are triggered by both external and internal signals. After the cell moves to the next stage of the cell cycle, the cyclins that were active in the previous stage are degraded. The concentrations of cyclin proteins change throughout the cell cycle. There is a direct correlation between cyclin accumulation and the three major cell cycle checkpoints. Also note the sharp decline of cyclin levels following each checkpoint (the transition between phases of the cell cycle), as cyclin is degraded by cytoplasmic enzymes. (credit: modification of work by "WikiMiMa"/Wikimedia Commons) 

Cyclins regulate the cell cycle only when they are tightly bound to Cdks. To be fully active, the Cdk/cyclin complex must also be phosphorylated in specific locations. Like all kinases, Cdks are enzymes (kinases) that phosphorylate other proteins. Phosphorylation activates the protein by changing its shape. The proteins phosphorylated by Cdks are involved in advancing the cell to the next phase. ( [link] ). The levels of Cdk proteins are relatively stable throughout the cell cycle; however, the concentrations of cyclin fluctuate and determine when Cdk/cyclin complexes form. The different cyclins and Cdks bind at specific points in the cell cycle and thus regulate different checkpoints. Cyclin-dependent kinases (Cdks) are protein kinases that, when fully activated, can phosphorylate and thus activate other proteins that advance the cell cycle past a checkpoint. To become fully activated, a Cdk must bind to a cyclin protein and then be phosphorylated by another kinase. 

Since the cyclic fluctuations of cyclin levels are based on the timing of the cell cycle and not on specific events, regulation of the cell cycle usually occurs by either the Cdk molecules alone or the Cdk/cyclin complexes. Without a specific concentration of fully activated cyclin/Cdk complexes, the cell cycle cannot proceed through the checkpoints. 

Although the cyclins are the main regulatory molecules that determine the forward momentum of the cell cycle, there are several other mechanisms that fine-tune the progress of the cycle with negative, rather than positive, effects. These mechanisms essentially block the progression of the cell cycle until problematic conditions are resolved. Molecules that prevent the full activation of Cdks are called Cdk inhibitors. Many of these inhibitor molecules directly or indirectly monitor a particular cell cycle event. The block placed on Cdks by inhibitor molecules will not be removed until the specific event that the inhibitor monitors is completed. Negative Regulation of the Cell Cycle 

The second group of cell cycle regulatory molecules are negative regulators. Negative regulators halt the cell cycle. Remember that in positive regulation, active molecules cause the cycle to progress. 

The best understood negative regulatory molecules are retinoblastoma protein (Rb) , p53 , and p21 . Retinoblastoma proteins are a group of tumor-suppressor proteins common in many cells. The 53 and 21 designations refer to the functional molecular masses of the proteins (p) in kilodaltons. Much of what is known about cell cycle regulation comes from research conducted with cells that have lost regulatory control. All three of these regulatory proteins were discovered to be damaged or non-functional in cells that had begun to replicate uncontrollably (became cancerous). In each case, the main cause of the unchecked progress through the cell cycle was a faulty copy of the regulatory protein. 

Rb, p53, and p21 act primarily at the G 1 checkpoint. p53 is a multi-functional protein that has a major impact on the commitment of a cell to division because it acts when there is damaged DNA in cells that are undergoing the preparatory processes during G 1 . If damaged DNA is detected, p53 halts the cell cycle and recruits enzymes to repair the DNA. If the DNA cannot be repaired, p53 can trigger apoptosis, or cell suicide, to prevent the duplication of damaged chromosomes. As p53 levels rise, the production of p21 is triggered. p21 enforces the halt in the cycle dictated by p53 by binding to and inhibiting the activity of the Cdk/cyclin complexes. As a cell is exposed to more stress, higher levels of p53 and p21 accumulate, making it less likely that the cell will move into the S phase. 

Rb exerts its regulatory influence on other positive regulator proteins. Chiefly, Rb monitors cell size. In the active, dephosphorylated state, Rb binds to proteins called transcription factors, most commonly, E2F ( [link] ). Transcription factors turn on specific genes, allowing the production of proteins encoded by that gene. When Rb is bound to E2F, production of proteins necessary for the G 1 /S transition is blocked. As the cell increases in size, Rb is slowly phosphorylated until it becomes inactivated. Rb releases E2F, which can now turn on the gene that produces the transition protein, and this particular block is removed. For the cell to move past each of the checkpoints, all positive regulators must be turned on, and all negative regulators must be turned off. 

Rb halts the cell cycle and releases its hold in response to cell growth. 

[link] Rb is a negative regulator that blocks the cell cycle at the G 1 checkpoint until the cell achieves a requisite size. What is the most likely mechanism that Rb employs to halt the cell cycle? A cell has a mutation that results in the production of an abnormal cyclin-dependent kinase at the G 2 /M checkpoint. What is a likely consequence of the mutation on the cell cycle? 

The Think About It questions are applications of Learning Objective 3.7 and Science Practice 6.4 and Learning Objective 3.8 and Science Practice 1.2 because the students are making predictions based on their understanding of the events occurring during the cell cycle. 

Answers Rb is active when it is dephosphorylated. In this state, Rb binds to E2F, which is a transcription factor required for the transcription and eventual translation of molecules required for the G 1 /S transition. E2F cannot transcribe certain genes when it is bound to Rb. As the cell increases in size, Rb becomes phosphorylated, inactivated, and releases E2F. E2F can then promote the transcription of the genes it controls, and the transition proteins will be produced. Cyclins and cyclin-dependent kinases (Cdks), are responsible for the progress of the cell through the various checkpoints including the G 2 /M checkpoint. Without a specific concentration of fully activated cyclin/Cdk complexes, or if an abnormal cdk is produced, the cell cycle cannot proceed through the checkpoint and will arrest at the G 2 /M checkpoint. Section Summary 

Each step of the cell cycle is monitored by internal controls called checkpoints. There are three major checkpoints in the cell cycle: one near the end of G 1 , a second at the G 2 /M transition, and the third during metaphase. Positive regulator molecules allow the cell cycle to advance to the next stage. Negative regulator molecules monitor cellular conditions and can halt the cycle until specific requirements are met. Review Questions 

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[link] Glossary cell cycle checkpoint mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages cyclin one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle cyclin-dependent kinase one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation p21 cell cycle regulatory protein that inhibits the cell cycle; its levels are controlled by p53 p53 cell cycle regulatory protein that regulates cell growth and monitors DNA damage; it halts the progression of the cell cycle in cases of DNA damage and may induce apoptosis retinoblastoma protein (Rb) regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F)Cancer and the Cell Cycle Cancer and the Cell Cycle 

In this section, you will explore the following question: What causes uncontrolled cell growth, and why does it often cause cancer? Connection for AP Courses 

Cancer results from unchecked cell division caused by a breakdown of the mechanisms that regulate the cell cycle. The loss of control begins with a change in the DNA sequence of a gene that codes for one of the regulatory molecules. Faulty instructions lead to a protein that does not function as it should. One culprit that has been identified is the p53 protein (coded for by the p53 gene), a major regulator at the G 1 checkpoint. Normally, p53 proteins monitor DNA. If they find cells with damaged DNA, p53 will trigger repair mechanisms or destroy the cells, thus suppressing the formation of a tumor. However, mutations in p53 can result in abnormal p53 proteins that fail to stop cell division if the cell s DNA is damaged. This results in an increased number of mutations, leading to abnormal daughter cells. Eventually, all checkpoints in the cell become nonfunctional, and the abnormal cells can crowd out normal cells. 

Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework, as shown in the table. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.7 The student can make predictions about natural phenomena occurring during the cell cycle. 

This chapter reviews the fidelity with which undamaged and damaged DNA is copied. Students who want more background on how gene mutations can occur maybe interested in reading the review The fidelity of DNA synthesis by eukaryotic replicative and translation synthesis polymerases here . 

Introduce the topic of loss of control of the cell cycle using visuals such as these videos: The Eukaryotic Cell Cycle and Cancer , Tumor Suppressor Genes , Click and Learn: p53 Gene and Cancer , and Using p53 to Fight Cancer . 

Students may believe that the presence of a mutation in p53 or any of the tumor suppressor genes or proto-oncogenes leads to the formation of cancer in every case. However, the development of cancer is a complex process. The presence of a gene mutation does not in and of itself mean cancer will develop. Three main factors can cause cancer: environmental factors, carcinogens, viruses, and genetics. Additional overview of the development of cancer can be given to students in this video . 

Cancer comprises many different diseases caused by a common mechanism: uncontrolled cell growth. Despite the redundancy and overlapping levels of cell cycle control, errors do occur. One of the critical processes monitored by the cell cycle checkpoint surveillance mechanism is the proper replication of DNA during the S phase. Even when all of the cell cycle controls are fully functional, a small percentage of replication errors (mutations) will be passed on to the daughter cells. If changes to the DNA nucleotide sequence occur within a coding portion of a gene and are not corrected, a gene mutation results. All cancers start when a gene mutation gives rise to a faulty protein that plays a key role in cell reproduction. The change in the cell that results from the malformed protein may be minor: perhaps a slight delay in the binding of Cdk to cyclin or an Rb protein that detaches from its target DNA while still phosphorylated. Even minor mistakes, however, may allow subsequent mistakes to occur more readily. Over and over, small uncorrected errors are passed from the parent cell to the daughter cells and amplified as each generation produces more non-functional proteins from uncorrected DNA damage. Eventually, the pace of the cell cycle speeds up as the effectiveness of the control and repair mechanisms decreases. Uncontrolled growth of the mutated cells outpaces the growth of normal cells in the area, and a tumor ( -oma ) can result. Proto-oncogenes 

The genes that code for the positive cell cycle regulators are called proto-oncogenes . Proto-oncogenes are normal genes that, when mutated in certain ways, become oncogenes , genes that cause a cell to become cancerous. Consider what might happen to the cell cycle in a cell with a recently acquired oncogene. In most instances, the alteration of the DNA sequence will result in a less functional (or non-functional) protein. The result is detrimental to the cell and will likely prevent the cell from completing the cell cycle; however, the organism is not harmed because the mutation will not be carried forward. If a cell cannot reproduce, the mutation is not propagated and the damage is minimal. Occasionally, however, a gene mutation causes a change that increases the activity of a positive regulator. For example, a mutation that allows Cdk to be activated without being partnered with cyclin could push the cell cycle past a checkpoint before all of the required conditions are met. If the resulting daughter cells are too damaged to undergo further cell divisions, the mutation would not be propagated and no harm would come to the organism. However, if the atypical daughter cells are able to undergo further cell divisions, subsequent generations of cells will probably accumulate even more mutations, some possibly in additional genes that regulate the cell cycle. 

The Cdk gene in the above example is only one of many genes that are considered proto-oncogenes. In addition to the cell cycle regulatory proteins, any protein that influences the cycle can be altered in such a way as to override cell cycle checkpoints. An oncogene is any gene that, when altered, leads to an increase in the rate of cell cycle progression. Tumor Suppressor Genes 

Like proto-oncogenes, many of the negative cell cycle regulatory proteins were discovered in cells that had become cancerous. Tumor suppressor genes are segments of DNA that code for negative regulator proteins, the type of regulators that, when activated, can prevent the cell from undergoing uncontrolled division. The collective function of the best-understood tumor suppressor gene proteins, Rb, p53, and p21, is to put up a roadblock to cell cycle progression until certain events are completed. A cell that carries a mutated form of a negative regulator might not be able to halt the cell cycle if there is a problem. Tumor suppressors are similar to brakes in a vehicle: Malfunctioning brakes can contribute to a car crash. 

Mutated p53 genes have been identified in more than one-half of all human tumor cells. This discovery is not surprising in light of the multiple roles that the p53 protein plays at the G 1 checkpoint. A cell with a faulty p53 may fail to detect errors present in the genomic DNA ( [link] ). Even if a partially functional p53 does identify the mutations, it may no longer be able to signal the necessary DNA repair enzymes. Either way, damaged DNA will remain uncorrected. At this point, a functional p53 will deem the cell unsalvageable and trigger programmed cell death (apoptosis). The damaged version of p53 found in cancer cells, however, cannot trigger apoptosis. 

The role of normal p53 is to monitor DNA and the supply of oxygen (hypoxia is a condition of reduced oxygen supply). If damage is detected, p53 triggers repair mechanisms. If repairs are unsuccessful, p53 signals apoptosis. A cell with an abnormal p53 protein cannot repair damaged DNA and thus cannot signal apoptosis. Cells with abnormal p53 can become cancerous. (credit: modification of work by Thierry Soussi) 

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The loss of p53 function has other repercussions for the cell cycle. Mutated p53 might lose its ability to trigger p21 production. Without adequate levels of p21, there is no effective block on Cdk activation. Essentially, without a fully functional p53, the G 1 checkpoint is severely compromised and the cell proceeds directly from G 1 to S regardless of internal and external conditions. At the completion of this shortened cell cycle, two daughter cells are produced that have inherited the mutated p53 gene. Given the non-optimal conditions under which the parent cell reproduced, it is likely that the daughter cells will have acquired other mutations in addition to the faulty tumor suppressor gene. Cells such as these daughter cells quickly accumulate both oncogenes and non-functional tumor suppressor genes. Again, the result is tumor growth. 

Go to this website to watch an animation of how cancer results from errors in the cell cycle. 

[link] Think About It 

Human papillomavirus (HPV) can cause cervical cancer. The virus encodes E6, a protein that binds p53. Predict the most likely effect of E6 binding on p53 activity, and explain the basis for your prediction. 

This question is an application of Learning Objectives 3.7 and Science Practice 7.4 because the students are predicting how a change in regulation of the cell cycle can result in cancer. Answer 

The role of normal p53 is to monitor DNA for damage. If damage is detected, p53 triggers repair mechanisms. If repairs are unsuccessful, p53 signals apoptosis. A cell with an abnormal p53 protein cannot repair damaged DNA or signal apoptosis. Cells with abnormal p53 can become cancerous. Because E6 leads to the development of cancer, it must bind p53 is such a way that p53 cannot monitor DNA for damage, cannot trigger a repair mechanism, or signal apoptosis. Section Summary 

Cancer is the result of unchecked cell division caused by a breakdown of the mechanisms that regulate the cell cycle. The loss of control begins with a change in the DNA sequence of a gene that codes for one of the regulatory molecules. Faulty instructions lead to a protein that does not function as it should. Any disruption of the monitoring system can allow other mistakes to be passed on to the daughter cells. Each successive cell division will give rise to daughter cells with even more accumulated damage. Eventually, all checkpoints become nonfunctional, and rapidly reproducing cells crowd out normal cells, resulting in a tumor or leukemia (blood cancer). Review Questions 

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[link] Glossary oncogene mutated version of a normal gene involved in the positive regulation of the cell cycle proto-oncogene normal gene that when mutated becomes an oncogene tumor suppressor gene segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled divisionProkaryotic Cell Division Prokaryotic Cell Division 

In this section, you will explore the following question: How does the process of binary fission in prokaryotes differ from cell division in eukaryotes? 

Prokaryotes, such as bacteria, propagate by binary fission. For unicellular organisms, cell division is the only method to produce new individuals. In both prokaryotic and eukaryotic cells, the outcome of cell reproduction is a pair of daughter cells that are genetically identical to the parent cell. In unicellular organisms, daughter cells are individuals. 

To achieve the outcome of cloned offspring, certain steps are essential. The genomic DNA must be replicated and then allocated into the daughter cells; the cytoplasmic contents must also be divided to give both new cells the machinery to sustain life. In bacterial cells, the genome consists of a single, circular DNA chromosome; therefore, the process of cell division is simplified. Karyokinesis is unnecessary because there is no nucleus and thus no need to direct one copy of the multiple chromosomes into each daughter cell. This type of cell division is called binary (prokaryotic) fission . Binary Fission 

Due to the relative simplicity of the prokaryotes, the cell division process, called binary fission, is a less complicated and much more rapid process than cell division in eukaryotes. The single, circular DNA chromosome of bacteria is not enclosed in a nucleus, but instead occupies a specific location, the nucleoid, within the cell ( [link] ). Although the DNA of the nucleoid is associated with proteins that aid in packaging the molecule into a compact size, there are no histone proteins and thus no nucleosomes in prokaryotes. The packing proteins of bacteria are, however, related to the cohesin and condensin proteins involved in the chromosome compaction of eukaryotes. 

The bacterial chromosome is attached to the plasma membrane at about the midpoint of the cell. The starting point of replication, the origin , is close to the binding site of the chromosome to the plasma membrane ( [link] ). Replication of the DNA is bidirectional, moving away from the origin on both strands of the loop simultaneously. As the new double strands are formed, each origin point moves away from the cell wall attachment toward the opposite ends of the cell. As the cell elongates, the growing membrane aids in the transport of the chromosomes. After the chromosomes have cleared the midpoint of the elongated cell, cytoplasmic separation begins. The formation of a ring composed of repeating units of a protein called FtsZ directs the partition between the nucleoids. Formation of the FtsZ ring triggers the accumulation of other proteins that work together to recruit new membrane and cell wall materials to the site. A septum is formed between the nucleoids, extending gradually from the periphery toward the center of the cell. When the new cell walls are in place, the daughter cells separate. These images show the steps of binary fission in prokaryotes. (credit: modification of work by Mcstrother /Wikimedia Commons) Mitotic Spindle Apparatus 

The precise timing and formation of the mitotic spindle is critical to the success of eukaryotic cell division. Prokaryotic cells, on the other hand, do not undergo karyokinesis and therefore have no need for a mitotic spindle. However, the FtsZ protein that plays such a vital role in prokaryotic cytokinesis is structurally and functionally very similar to tubulin, the building block of the microtubules that make up the mitotic spindle fibers that are necessary for eukaryotes. FtsZ proteins can form filaments, rings, and other three-dimensional structures that resemble the way tubulin forms microtubules, centrioles, and various cytoskeletal components. In addition, both FtsZ and tubulin employ the same energy source, GTP (guanosine triphosphate), to rapidly assemble and disassemble complex structures. 

FtsZ and tubulin are homologous structures derived from common evolutionary origins. In this example, FtsZ is the ancestor protein to tubulin (a modern protein). While both proteins are found in extant organisms, tubulin function has evolved and diversified tremendously since evolving from its FtsZ prokaryotic origin. A survey of mitotic assembly components found in present-day unicellular eukaryotes reveals crucial intermediary steps to the complex membrane-enclosed genomes of multicellular eukaryotes ( [link] ). Cell Division Apparatus among Various Organisms Structure of genetic material Division of nuclear material Separation of daughter cells Prokaryotes There is no nucleus. The single, circular chromosome exists in a region of cytoplasm called the nucleoid. Occurs through binary fission. As the chromosome is replicated, the two copies move to opposite ends of the cell by an unknown mechanism. FtsZ proteins assemble into a ring that pinches the cell in two. Some protists Linear chromosomes exist in the nucleus. Chromosomes attach to the nuclear envelope, which remains intact. The mitotic spindle passes through the envelope and elongates the cell. No centrioles exist. Microfilaments form a cleavage furrow that pinches the cell in two. Other protists Linear chromosomes exist in the nucleus. A mitotic spindle forms from the centrioles and passes through the nuclear membrane, which remains intact. Chromosomes attach to the mitotic spindle, which separates the chromosomes and elongates the cell. Microfilaments form a cleavage furrow that pinches the cell in two. Animal cells Linear chromosomes exist in the nucleus. A mitotic spindle forms from the centrosomes. The nuclear envelope dissolves. Chromosomes attach to the mitotic spindle, which separates the chromosomes and elongates the cell. Microfilaments form a cleavage furrow that pinches the cell in two. 

[link] Section Summary 

In both prokaryotic and eukaryotic cell division, the genomic DNA is replicated and then each copy is allocated into a daughter cell. In addition, the cytoplasmic contents are divided evenly and distributed to the new cells. However, there are many differences between prokaryotic and eukaryotic cell division. Bacteria have a single, circular DNA chromosome but no nucleus. Therefore, mitosis is not necessary in bacterial cell division. Bacterial cytokinesis is directed by a ring composed of a protein called FtsZ. Ingrowth of membrane and cell wall material from the periphery of the cells results in the formation of a septum that eventually constructs the separate cell walls of the daughter cells. Review Questions 

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[link] Glossary binary fission prokaryotic cell division process FtsZ tubulin-like protein component of the prokaryotic cytoskeleton that is important in prokaryotic cytokinesis (name origin: F ilamenting t emperature- s ensitive mutant Z ) origin (also, ORI) region of the prokaryotic chromosome where replication begins (origin of replication) septum structure formed in a bacterial cell as a precursor to the separation of the cell into two daughter cellsIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP #174; Courses" Each of us, like these other large multicellular organisms, begins life as a fertilized egg. After trillions of cell divisions, each of us develops into a complex, multicellular organism. (credit a: modification of work by Frank Wouters; credit b: modification of work by Ken Cole, USGS; credit c: modification of work by Martin Pettitt) 

The ability to reproduce in kind is a basic characteristic of all living things. In kind means that the offspring of an organism closely resembles its parent or parents. Hippopotamuses give birth to hippopotamus calves, Joshua trees produce Joshua tree seedlings, and flamingos lay eggs that hatch into flamingo chicks. In kind can mean exactly the same. Many unicellular organisms, such as yeast, and a few multicellular organisms, such as sponges, can produce genetically identical clones of themselves through cell division. However, many single-celled organisms and most multicellular organisms reproduce regularly using a method requiring two parents. Sexual reproduction occurs through the production by each parent of a haploid cell (containing one half of an offspring s required genetic material) and the fusion of these two haploid cells to form a single, unique diploid cell with a complete set of genetic information. In most plants and animals, through multiple rounds of mitotic cell division, this diploid cell will develop into an adult organism. Haploid cells that are necessary for sexual reproduction are produced by a type of cell division called meiosis. Sexual reproduction, specifically meiosis and fertilization, introduces variation into offspring. Variation is an important component of a species evolutionary success. The vast majority of eukaryotic organisms employs some form of meiosis and fertilization to reproduce. 

Not all sexually reproducing eukaryotes reproduce solely by sexual reproduction. For example, an Asian termite species, Reticulitermes speratus , can reproduce sexually or asexually. In a young colony, a single termite pair the king and queen produce worker offspring sexually by the union of haploid cells. However, after several years, as the queen begins to age, she produces some offspring asexually in a process called parthenogenesis. These offspring, which are destined to become new queens, are not fertilized by the king. They are genetic clones of the queen. More information about parthenogenesis in these termites can be found at this article . 

It is important to stress how critical sexual reproduction is for the adaptation and survival of many species. Natural selection works only because there are variations in genes, and genetic variations are a natural result of sexual reproduction.The Process of Meiosis The Process of Meiosis 

In this section, you will explore the following questions: How do chromosomes behave during meiosis? What cellular events occur during meiosis? What are the similarities and differences between meiosis and mitosis? How can the process of meiosis generate genetic variation? Connection for AP Courses 

As we explored the cell cycle and mitosis in a previous chapter, we learned that cells divide to grow, replace other cells, and reproduce asexually. Without mutation, or changes in the DNA, the daughter cells produced by mitosis receive a set of genetic instructions that is identical to that of the parent cell. Because changes in genes drive both the unity and diversity of life, organisms without genetic variation cannot evolve through natural selection. Evolution occurs only because organisms have developed ways to vary their genetic material. This occurs through mutations in DNA, recombination of genes during meiosis, and meiosis followed by fertilization in sexually reproducing organisms. 

Sexual reproduction requires that diploid (2 n ) organisms produce haploid (1 n ) cells through meiosis and that these haploid cells fuse to form new, diploid offspring. The union of these two haploid cells, one from each parent, is fertilization. Although the processes of meiosis and mitosis share similarities, their end products are different. Recall that eukaryotic DNA is contained in chromosomes, and that chromosomes occur in homologous pairs (homologues). At fertilization, the male parent contributes one member of each homologous pair to the offspring, and the female parent contributes the other. With the exception of the sex chromosomes, homologous chromosomes contain the same genes, but these genes can have different variations, called alleles. (For example, you might have inherited an allele for brown eyes from your father and an allele for blue eyes from your mother.) As in mitosis, homologous chromosomes are duplicated during the S-stage (synthesis) of interphase. However, unlike mitosis, in which there is just one nuclear division, meiosis has two complete rounds of nuclear division meiosis I and meiosis II. These result in four nuclei and (usually) four daughter cells, each with half the number of chromosomes as the parent cell (1 n ). The first division, meiosis I, separates homologous chromosomes, and the second division, meiosis II, separates chromatids. (Remember: during meiosis, DNA replicates ONCE but divides TWICE, whereas in mitosis, DNA replicates ONCE but divides only ONCE.). 

Although mitosis and meiosis are similar in many ways, they have different outcomes. The main difference is in the type of cell produced: mitosis produces identical cells, allowing growth or repair of tissues; meiosis generates reproductive cells, or gametes. Gametes, often called sex cells, unite with other sex cells to produce new, unique organisms. 

Genetic variation occurs during meiosis I, in which homologous chromosomes pair and exchange non-sister chromatid segments (crossover). Here the homologous chromosomes separate into different nuclei, causing a reduction in ploidy. During meiosis II which is more similar to a mitotic division the chromatids separate and segregate into four haploid sex cells. However, because of crossover, the resultant daughter cells do not contain identical genomes. As in mitosis, external factors and internal signals regulate the meiotic cell cycle. As we will explore in more detail in a later chapter, errors in meiosis can cause genetic disorders, such as Down syndrome. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.9 The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 3.10 The student is able to represent the connection between meiosis and increased genetic diversity necessary for evolution. 

The process of meiosis can be confusing, especially if it is taught as just a series of steps. Initially, discuss the goal of the process. Explain that meiosis serves to produce reproductive cells with exactly half the number of chromosomes, and that once these haploid cells are fused during fertilization, a complete set of genetic instructions for a new individual is formed. Meiosis starts in a cell with chromosomes in pairs. Each chromosome has already been duplicated and the two sister strands are held together. Therefore, each pair consists of four chromatids. Because students have already learned about mitosis (the process whereby chromosomes are sorted and allocated to daughter cells), it might be helpful to teach meiosis as a special case of mitosis. The first division separates the pairs of chromosomes, reducing the number of duplicated chromosomes in the daughter cells by half. The second division separates the chromatids, creating daughter cells that each has one half of the total number of chromosomes of the original cell. An added benefit to an organism using meiosis is the increase in genetic variation that occurs during the process. Each individual born as a result of sexual reproduction truly has a unique assortment of genes. 

You read that fertilization is the union of two sex cells from two individual organisms. If these two cells each contain one set of chromosomes, the resulting fertilized cell contains two sets of chromosomes. Haploid cells contain one set of chromosomes. Cells containing two sets of chromosomes are called diploid. The number of sets of chromosomes in a cell is called its ploidy level. If the reproductive cycle is to continue, a diploid cell must reduce the number of its chromosome sets before fertilization can occur again. Otherwise, the number of chromosome sets would double, and continue to double in every generation. So, in addition to fertilization, sexual reproduction includes a nuclear division that reduces the number of chromosome sets. 

Most animals and plants are diploid, containing two sets of chromosomes. In an organism s somatic cells , sometimes referred to as body cells (all cells of a multicellular organism except the reproductive cells), the nucleus contains two copies of each chromosome, called homologous chromosomes. Homologous chromosomes are matched pairs containing the same genes in identical locations along their length. Diploid organisms inherit one copy of each homologous chromosome from each parent; all together, they are considered a full set of chromosomes. Haploid cells, containing a single copy of each homologous chromosome, are found only within an organism s reproductive structures, such as the ovaries and testes. Haploid cells can be either gametes or spores. Male gametes are sperm and female gametes are eggs. All animals and most plants produce gametes. Spores are haploid cells that can produce a haploid organism or can fuse with another spore to form a diploid cell. Some plants and all fungi produce spores. 

As you have learned, the nuclear division that forms haploid cells meiosis is closely related to mitosis. Mitosis is the part of a cell reproduction cycle that results in identical daughter nuclei that are also genetically identical to the original parent nucleus. In mitosis, both the parent and the daughter nuclei are at the same ploidy level diploid for most plants and animals. Meiosis employs many of the same mechanisms as mitosis. However, the starting nucleus is always diploid and the nuclei that result at the end of a meiotic cell division are haploid. To achieve this reduction in chromosome number, meiosis consists of one round of chromosome duplication and two rounds of nuclear division. Because the events that occur during each of the division stages are analogous to the events of mitosis, the same stage names are assigned. However, because there are two rounds of division, the major process and the stages are designated with a I or a II. Thus, meiosis I is the first round of meiotic division and consists of prophase I, prometaphase I, and so on. Meiosis II , in which the second round of meiotic division takes place, includes prophase II, prometaphase II, and so on. 

Meiosis I has the same steps as mitosis, with the exception that the chromosome pairs, not the chromatids, are separated at anaphase I. Two other events occur during the first cell division to produce the genetic variation that results. In prophase I, when the pairs of chromosomes condense and tentatively join, parts of the arms and legs of the chromosomes can crossover, or exchange places, with corresponding parts on the other homologous chromosome. The resulting pair now has a configuration that was not present initially. The pairs line up in a double line during metaphase I, but the distribution of the pairs at the equator is random. Half of the original chromosomes came from one parent, half from the other. As the chromosomes line up and are pulled apart during anaphase I, each daughter cell will receive a chromosome mixture that was not present in the original germ cells. [link] illustrates crossing over and [link] illustrates the random distribution of pairs of chromosomes. Also use the Link to Learning: Meiosis: An Interactive Animation. Meiosis II finishes the process and closely resembles mitosis, except for the number of chromosomes present, as compared to somatic cells. 

Comparing meiosis and mitosis should be a review of the two processes, with a reinforcement of the similarities and differences. Meiosis I 

Meiosis is preceded by an interphase consisting of the G 1 , S, and G 2 phases, which are nearly identical to the phases preceding mitosis. The G 1 phase, which is also called the first gap phase, is the first phase of the interphase and is focused on cell growth. The S phase is the second phase of interphase, during which the DNA of the chromosomes is replicated. Finally, the G 2 phase, also called the second gap phase, is the third and final phase of interphase; in this phase, the cell undergoes the final preparations for meiosis. 

During DNA duplication in the S phase, each chromosome is replicated to produce two identical copies, called sister chromatids, that are held together at the centromere by cohesin proteins. Cohesin holds the chromatids together until anaphase II. The centrosomes, which are the structures that organize the microtubules of the meiotic spindle, also replicate. This prepares the cell to enter prophase I, the first meiotic phase. Prophase I 

Early in prophase I, before the chromosomes can be seen clearly microscopically, the homologous chromosomes are attached at their tips to the nuclear envelope by proteins. As the nuclear envelope begins to break down, the proteins associated with homologous chromosomes bring the pair close to each other. Recall that, in mitosis, homologous chromosomes do not pair together. In mitosis, homologous chromosomes line up end-to-end so that when they divide, each daughter cell receives a sister chromatid from both members of the homologous pair. The synaptonemal complex , a lattice of proteins between the homologous chromosomes, first forms at specific locations and then spreads to cover the entire length of the chromosomes. The tight pairing of the homologous chromosomes is called synapsis . In synapsis, the genes on the chromatids of the homologous chromosomes are aligned precisely with each other. The synaptonemal complex supports the exchange of chromosomal segments between non-sister homologous chromatids, a process called crossing over. Crossing over can be observed visually after the exchange as chiasmata (singular = chiasma) ( [link] ). 

In species such as humans, even though the X and Y sex chromosomes are not homologous (most of their genes differ), they have a small region of homology that allows the X and Y chromosomes to pair up during prophase I. A partial synaptonemal complex develops only between the regions of homology. Early in prophase I, homologous chromosomes come together to form a synapse. The chromosomes are bound tightly together and in perfect alignment by a protein lattice called a synaptonemal complex and by cohesin proteins at the centromere. 

Located at intervals along the synaptonemal complex are large protein assemblies called recombination nodules . These assemblies mark the points of later chiasmata and mediate the multistep process of crossover or genetic recombination between the non-sister chromatids. Near the recombination nodule on each chromatid, the double-stranded DNA is cleaved, the cut ends are modified, and a new connection is made between the non-sister chromatids. As prophase I progresses, the synaptonemal complex begins to break down and the chromosomes begin to condense. When the synaptonemal complex is gone, the homologous chromosomes remain attached to each other at the centromere and at chiasmata. The chiasmata remain until anaphase I. The number of chiasmata varies according to the species and the length of the chromosome. There must be at least one chiasma per chromosome for proper separation of homologous chromosomes during meiosis I, but there may be as many as 25. Following crossover, the synaptonemal complex breaks down and the cohesin connection between homologous pairs is also removed. At the end of prophase I, the pairs are held together only at the chiasmata ( [link] ) and are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. 

The crossover events are the first source of genetic variation in the nuclei produced by meiosis. A single crossover event between homologous non-sister chromatids leads to a reciprocal exchange of equivalent DNA between a maternal chromosome and a paternal chromosome. Now, when that sister chromatid is moved into a gamete cell it will carry some DNA from one parent of the individual and some DNA from the other parent. The sister recombinant chromatid has a combination of maternal and paternal genes that did not exist before the crossover. Multiple crossovers in an arm of the chromosome have the same effect, exchanging segments of DNA to create recombinant chromosomes. Crossover occurs between non-sister chromatids of homologous chromosomes. The result is an exchange of genetic material between homologous chromosomes. Prometaphase I 

The key event in prometaphase I is the attachment of the spindle fiber microtubules to the kinetochore proteins at the centromeres. Kinetochore proteins are multiprotein complexes that bind the centromeres of a chromosome to the microtubules of the mitotic spindle. Microtubules grow from centrosomes placed at opposite poles of the cell. The microtubules move toward the middle of the cell and attach to one of the two fused homologous chromosomes. The microtubules attach at each chromosomes' kinetochores. With each member of the homologous pair attached to opposite poles of the cell, in the next phase, the microtubules can pull the homologous pair apart. A spindle fiber that has attached to a kinetochore is called a kinetochore microtubule. At the end of prometaphase I, each tetrad is attached to microtubules from both poles, with one homologous chromosome facing each pole. The homologous chromosomes are still held together at chiasmata. In addition, the nuclear membrane has broken down entirely. Metaphase I 

During metaphase I, the homologous chromosomes are arranged in the center of the cell with the kinetochores facing opposite poles. The homologous pairs orient themselves randomly at the equator. For example, if the two homologous members of chromosome 1 are labeled a and b, then the chromosomes could line up a-b, or b-a. This is important in determining the genes carried by a gamete, as each will only receive one of the two homologous chromosomes. Recall that homologous chromosomes are not identical. They contain slight differences in their genetic information, causing each gamete to have a unique genetic makeup. 

This randomness is the physical basis for the creation of the second form of genetic variation in offspring. Consider that the homologous chromosomes of a sexually reproducing organism are originally inherited as two separate sets, one from each parent. Using humans as an example, one set of 23 chromosomes is present in the egg donated by the mother. The father provides the other set of 23 chromosomes in the sperm that fertilizes the egg. Every cell of the multicellular offspring has copies of the original two sets of homologous chromosomes. In prophase I of meiosis, the homologous chromosomes form the tetrads. In metaphase I, these pairs line up at the midway point between the two poles of the cell to form the metaphase plate. Because there is an equal chance that a microtubule fiber will encounter a maternally or paternally inherited chromosome, the arrangement of the tetrads at the metaphase plate is random. Any maternally inherited chromosome may face either pole. Any paternally inherited chromosome may also face either pole. The orientation of each tetrad is independent of the orientation of the other 22 tetrads. 

This event the random (or independent) assortment of homologous chromosomes at the metaphase plate is the second mechanism that introduces variation into the gametes or spores. In each cell that undergoes meiosis, the arrangement of the tetrads is different. The number of variations is dependent on the number of chromosomes making up a set. There are two possibilities for orientation at the metaphase plate; the possible number of alignments therefore equals 2 n , where n is the number of chromosomes per set. Humans have 23 chromosome pairs, which results in over eight million (2 23 ) possible genetically-distinct gametes. This number does not include the variability that was previously created in the sister chromatids by crossover. Given these two mechanisms, it is highly unlikely that any two haploid cells resulting from meiosis will have the same genetic composition ( [link] ). 

To summarize the genetic consequences of meiosis I, the maternal and paternal genes are recombined by crossover events that occur between each homologous pair during prophase I. In addition, the random assortment of tetrads on the metaphase plate produces a unique combination of maternal and paternal chromosomes that will make their way into the gametes. Random, independent assortment during metaphase I can be demonstrated by considering a cell with a set of two chromosomes ( n = 2). In this case, there are two possible arrangements at the equatorial plane in metaphase I. The total possible number of different gametes is 2 n , where n equals the number of chromosomes in a set. In this example, there are four possible genetic combinations for the gametes. With n = 23 in human cells, there are over 8 million possible combinations of paternal and maternal chromosomes. Anaphase I 

In anaphase I, the microtubules pull the linked chromosomes apart. The sister chromatids remain tightly bound together at the centromere. The chiasmata are broken in anaphase I as the microtubules attached to the fused kinetochores pull the homologous chromosomes apart ( [link] ). Telophase I and Cytokinesis 

In telophase, the separated chromosomes arrive at opposite poles. The remainder of the typical telophase events may or may not occur, depending on the species. In some organisms, the chromosomes decondense and nuclear envelopes form around the chromatids in telophase I. In other organisms, cytokinesis the physical separation of the cytoplasmic components into two daughter cells occurs without reformation of the nuclei. In nearly all species of animals and some fungi, cytokinesis separates the cell contents via a cleavage furrow (constriction of the actin ring that leads to cytoplasmic division). In plants, a cell plate is formed during cell cytokinesis by Golgi vesicles fusing at the metaphase plate. This cell plate will ultimately lead to the formation of cell walls that separate the two daughter cells. 

Two haploid cells are the end result of the first meiotic division. The cells are haploid because at each pole, there is just one of each pair of the homologous chromosomes. Therefore, only one full set of the chromosomes is present. This is why the cells are considered haploid there is only one chromosome set, even though each homolog still consists of two sister chromatids. Recall that sister chromatids are merely duplicates of one of the two homologous chromosomes (except for changes that occurred during crossing over). In meiosis II, these two sister chromatids will separate, creating four haploid daughter cells. 

Review the process of meiosis, observing how chromosomes align and migrate, at Meiosis: An Interactive Animation . 

[link] Meiosis II 

In some species, cells enter a brief interphase, or interkinesis , before entering meiosis II. Interkinesis lacks an S phase, so chromosomes are not duplicated. The two cells produced in meiosis I go through the events of meiosis II in synchrony. During meiosis II, the sister chromatids within the two daughter cells separate, forming four new haploid gametes. The mechanics of meiosis II is similar to mitosis, except that each dividing cell has only one set of homologous chromosomes. Therefore, each cell has half the number of sister chromatids to separate out as a diploid cell undergoing mitosis. Prophase II 

If the chromosomes decondensed in telophase I, they condense again. If nuclear envelopes were formed, they fragment into vesicles. The centrosomes that were duplicated during interkinesis move away from each other toward opposite poles, and new spindles are formed. Prometaphase II 

The nuclear envelopes are completely broken down, and the spindle is fully formed. Each sister chromatid forms an individual kinetochore that attaches to microtubules from opposite poles. Metaphase II 

The sister chromatids are maximally condensed and aligned at the equator of the cell. Anaphase II 

The sister chromatids are pulled apart by the kinetochore microtubules and move toward opposite poles. Non-kinetochore microtubules elongate the cell. The process of chromosome alignment differs between meiosis I and meiosis II. In prometaphase I, microtubules attach to the fused kinetochores of homologous chromosomes, and the homologous chromosomes are arranged at the midpoint of the cell in metaphase I. In anaphase I, the homologous chromosomes are separated. In prometaphase II, microtubules attach to the kinetochores of sister chromatids, and the sister chromatids are arranged at the midpoint of the cells in metaphase II. In anaphase II, the sister chromatids are separated. Telophase II and Cytokinesis 

The chromosomes arrive at opposite poles and begin to decondense. Nuclear envelopes form around the chromosomes. Cytokinesis separates the two cells into four unique haploid cells. At this point, the newly formed nuclei are both haploid. The cells produced are genetically unique because of the random assortment of paternal and maternal homologs and because of the recombining of maternal and paternal segments of chromosomes (with their sets of genes) that occurs during crossover. The entire process of meiosis is outlined in [link] . An animal cell with a diploid number of four (2 n = 4) proceeds through the stages of meiosis to form four haploid daughter cells. Comparing Meiosis and Mitosis 

Mitosis and meiosis are both forms of division of the nucleus in eukaryotic cells. They share some similarities, but also exhibit distinct differences that lead to very different outcomes ( [link] ). Mitosis is a single nuclear division that results in two nuclei that are usually partitioned into two new cells. The nuclei resulting from a mitotic division are genetically identical to the original nucleus. They have the same number of sets of chromosomes, one set in the case of haploid cells and two sets in the case of diploid cells. In most plants and all animal species, it is typically diploid cells that undergo mitosis to form new diploid cells. In contrast, meiosis consists of two nuclear divisions resulting in four nuclei that are usually partitioned into four new cells. The nuclei resulting from meiosis are not genetically identical and they contain one chromosome set only. This is half the number of chromosome sets in the original cell, which is diploid. 

The main differences between mitosis and meiosis occur in meiosis I, which is a very different nuclear division than mitosis. In meiosis I, the homologous chromosome pairs become associated with each other, are bound together with the synaptonemal complex, develop chiasmata and undergo crossover between sister chromatids, and line up along the metaphase plate in tetrads with kinetochore fibers from opposite spindle poles attached to each kinetochore of a homolog in a tetrad. All of these events occur only in meiosis I. 

When the chiasmata resolve and the tetrad is broken up with the homologs moving to one pole or another, the ploidy level the number of sets of chromosomes in each future nucleus has been reduced from two to one. For this reason, meiosis I is referred to as a reduction division . There is no such reduction in ploidy level during mitosis. 

Meiosis II is much more analogous to a mitotic division. In this case, the duplicated chromosomes (only one set of them) line up on the metaphase plate with divided kinetochores attached to kinetochore fibers from opposite poles. During anaphase II, as in mitotic anaphase, the kinetochores divide and one sister chromatid now referred to as a chromosome is pulled to one pole while the other sister chromatid is pulled to the other pole. If it were not for the fact that there had been crossover, the two products of each individual meiosis II division would be identical (like in mitosis). Instead, they are different because there has always been at least one crossover per chromosome. Meiosis II is not a reduction division because although there are fewer copies of the genome in the resulting cells, there is still one set of chromosomes, as there was at the end of meiosis I. Meiosis and mitosis are both preceded by one round of DNA replication; however, meiosis includes two nuclear divisions. The four daughter cells resulting from meiosis are haploid and genetically distinct. The daughter cells resulting from mitosis are diploid and identical to the parent cell. 

The Mystery of the Evolution of Meiosis Some characteristics of organisms are so widespread and fundamental that it is sometimes difficult to remember that they evolved like other simpler traits. Meiosis is such an extraordinarily complex series of cellular events that biologists have had trouble hypothesizing and testing how it may have evolved. Although meiosis is inextricably entwined with sexual reproduction and its advantages and disadvantages, it is important to separate the questions of the evolution of meiosis and the evolution of sex, because early meiosis may have been advantageous for different reasons than it is now. Thinking outside the box and imagining what the early benefits from meiosis might have been is one approach to uncovering how it may have evolved. 

Meiosis and mitosis share obvious cellular processes and it makes sense that meiosis evolved from mitosis. The difficulty lies in the clear differences between meiosis I and mitosis. Adam Wilkins and Robin Holliday 1 summarized the unique events that needed to occur for the evolution of meiosis from mitosis. These steps are homologous chromosome pairing, crossover exchanges, sister chromatids remaining attached during anaphase, and suppression of DNA replication in interphase. They argue that the first step is the hardest and most important, and that understanding how it evolved would make the evolutionary process clearer. They suggest genetic experiments that might shed light on the evolution of synapsis. 

There are other approaches to understanding the evolution of meiosis in progress. Different forms of meiosis exist in single-celled protists. Some appear to be simpler or more primitive forms of meiosis. Comparing the meiotic divisions of different protists may shed light on the evolution of meiosis. Marilee Ramesh and colleagues 2 compared the genes involved in meiosis in protists to understand when and where meiosis might have evolved. Although research is still ongoing, recent scholarship into meiosis in protists suggests that some aspects of meiosis may have evolved later than others. This kind of genetic comparison can tell us what aspects of meiosis are the oldest and what cellular processes they may have borrowed from in earlier cells. 

[link] 

Click through the steps of this interactive animation to compare the meiotic process of cell division to that of mitosis: How Cells Divide . 

[link] Activity 

Create a series of diagrams with annotations to compare and contrast the processes of mitosis and meiosis in an organism with a haploid number of six. Then, using specific examples, explain how meiosis followed by fertilization increases genetic variation in a family of organisms. 

This activity is an application of Learning Objectives 3.9 and science practice 6.2, Learning Objectives 3.10 and science practice 7.1, and Learning Objectives 3.28 and science practice 6.2 because students are creating a visual representation to show how DNA is transmitted to the next generation by mitosis and meiosis followed by fertilization and then are using the representation to explain how meiosis increases genetic variation. Section Summary 

Sexual reproduction requires that diploid organisms produce haploid cells that can fuse during fertilization to form diploid offspring. As with mitosis, DNA replication occurs prior to meiosis during the S-phase of the cell cycle. Meiosis is a series of events that arrange and separate chromosomes and chromatids into daughter cells. During the interphases of meiosis, each chromosome is duplicated. In meiosis, there are two rounds of nuclear division resulting in four nuclei and usually four daughter cells, each with half the number of chromosomes as the parent cell. The first separates homologs, and the second like mitosis separates chromatids into individual chromosomes. During meiosis, variation in the daughter nuclei is introduced because of crossover in prophase I and random alignment of tetrads at metaphase I. The cells that are produced by meiosis are genetically unique. 

Meiosis and mitosis share similarities, but have distinct outcomes. Mitotic divisions are single nuclear divisions that produce daughter nuclei that are genetically identical and have the same number of chromosome sets as the original cell. Meiotic divisions include two nuclear divisions that produce four daughter nuclei that are genetically different and have one chromosome set instead of the two sets of chromosomes in the parent cell. The main differences between the processes occur in the first division of meiosis, in which homologous chromosomes are paired and exchange non-sister chromatid segments. The homologous chromosomes separate into different nuclei during meiosis I, causing a reduction of ploidy level in the first division. The second division of meiosis is more similar to a mitotic division, except that the daughter cells do not contain identical genomes because of crossover. Review Questions 

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[link] Footnotes 1 

Adam S. Wilkins and Robin Holliday, The Evolution of Meiosis from Mitosis, Genetics 181 (2009): 3 12. 2 

Marilee A. Ramesh, Shehre-Banoo Malik and John M. Logsdon, Jr, A Phylogenetic Inventory of Meiotic Genes: Evidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis, Current Biology 15 (2005):185 91. Glossary chiasmata (singular, chiasma ) the structure that forms at the crossover points after genetic material is exchanged cohesin proteins that form a complex that seals sister chromatids together at their centromeres until anaphase II of meiosis crossover exchange of genetic material between non-sister chromatids resulting in chromosomes that incorporate genes from both parents of the organism fertilization union of two haploid cells from two individual organisms interkinesis (also, interphase II ) brief period of rest between meiosis I and meiosis II meiosis a nuclear division process that results in four haploid cells meiosis I first round of meiotic cell division; referred to as reduction division because the ploidy level is reduced from diploid to haploid meiosis II second round of meiotic cell division following meiosis I; sister chromatids are separated into individual chromosomes, and the result is four unique haploid cells recombination nodules protein assemblies formed on the synaptonemal complex that mark the points of crossover events and mediate the multistep process of genetic recombination between non-sister chromatids reduction division nuclear division that produces daughter nuclei each having one-half as many chromosome sets as the parental nucleus; meiosis I is a reduction division somatic cell all the cells of a multicellular organism except the gametes or reproductive cells spore haploid cell that can produce a haploid multicellular organism or can fuse with another spore to form a diploid cell synapsis formation of a close association between homologous chromosomes during prophase I synaptonemal complex protein lattice that forms between homologous chromosomes during prophase I, supporting crossover tetrad two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase ISexual Reproduction Sexual Reproduction 

In this section, you will explore the following questions: Why are meiosis and sexual reproduction considered evolved traits? Why is variation among offspring a potential evolutionary advantage to sexual reproduction? What are the three different life-cycles among sexual multicellular organisms and their commonalities? Connection for AP Courses 

Nearly all eukaryotes undergo sexual reproduction. The variation introduced into the reproductive cells (gametes or spores) by meiosis is advantageous for evolution via natural selection. Meiosis and fertilization alternate as the organisms pass through the haploid and diploid stages of their life cycles. In most animals, the diploid stage dominates, whereas in fungi, the haploid stage dominates. Identifying the haploid and diploid stages within the life cycles of different organisms is vital in understanding how organisms reproduce and in determining when mitosis and meiosis occur. 

Information presented and the examples highlighted in the section support concepts and learning objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.C.2 Biological systems have multiple processes that increase genetic variation. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.27 The student is able to compare and contrast processes by which genetic variation is produced and maintained in organisms from multiple domains. 

Sexual reproduction in this chapter deals with sexual life cycles of animals, plants, fungi, and algae. Divide the class into small groups of 4 5 students and assign each group one of these categories. The students are to identify at least three examples of life cycles among organisms in their group s category. Have each group report back to the class with its findings, explaining the reproductive cycles it has identified (with real life examples, if possible). 

Sexual reproduction was an early evolutionary innovation after the appearance of eukaryotic cells. It appears to have been very successful because most eukaryotes are able to reproduce sexually, and in many animals, it is the only mode of reproduction. And yet, scientists recognize some real disadvantages to sexual reproduction. On the surface, creating offspring that are genetic clones of the parent appears to be a better system. If the parent organism is successfully occupying a habitat, offspring with the same traits would be similarly successful. There is also the obvious benefit to an organism that can produce offspring whenever circumstances are favorable by asexual budding, fragmentation, or asexual eggs. These methods of reproduction do not require another organism of the opposite sex. Indeed, some organisms that lead a solitary lifestyle have retained the ability to reproduce asexually. In addition, in asexual populations, every individual is capable of reproduction. In sexual populations, the males are not producing the offspring themselves, so in theory an asexual population could grow twice as fast. 

However, multicellular organisms that exclusively depend on asexual reproduction are exceedingly rare. Why is sexuality (and meiosis) so common? This is one of the important unanswered questions in biology and has been the focus of much research beginning in the latter half of the twentieth century. There are several possible explanations, one of which is that the variation that sexual reproduction creates among offspring is very important to the survival and reproduction of the population. Thus, on average, a sexually reproducing population will leave more descendants than an otherwise similar asexually reproducing population. The only source of variation in asexual organisms is mutation. This is the ultimate source of variation in sexual organisms, but in addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes and the genes are mixed into different combinations by crossovers during prophase I and random assortment at metaphase I. 

The Red Queen Hypothesis It is not in dispute that sexual reproduction provides evolutionary advantages to organisms that employ this mechanism to produce offspring. But why, even in the face of fairly stable conditions, does sexual reproduction persist when it is more difficult and costly for individual organisms? Variation is the outcome of sexual reproduction, but why are ongoing variations necessary? Enter the Red Queen hypothesis, first proposed by Leigh Van Valen in 1973. 1 The concept was named in reference to the Red Queen's race in Lewis Carroll's book, Through the Looking-Glass . 

All species co-evolve with other organisms; for example predators evolve with their prey, and parasites evolve with their hosts. Each tiny advantage gained by favorable variation gives a species an edge over close competitors, predators, parasites, or even prey. The only method that will allow a co-evolving species to maintain its own share of the resources is to also continually improve its fitness. As one species gains an advantage, this increases selection on the other species; they must also develop an advantage or they will be outcompeted. No single species progresses too far ahead because genetic variation among the progeny of sexual reproduction provides all species with a mechanism to improve rapidly. Species that cannot keep up become extinct. The Red Queen s catchphrase was, It takes all the running you can do to stay in the same place. This is an apt description of co-evolution between competing species. 

[link] Life Cycles of Sexually Reproducing Organisms 

Fertilization and meiosis alternate in sexual life cycles . What happens between these two events depends on the organism. The process of meiosis reduces the chromosome number by half. Fertilization, the joining of two haploid gametes, restores the diploid condition. There are three main categories of life cycles in multicellular organisms: diploid-dominant , in which the multicellular diploid stage is the most obvious life stage, such as with most animals including humans; haploid-dominant , in which the multicellular haploid stage is the most obvious life stage, such as with all fungi and some algae; and alternation of generations , in which the two stages are apparent to different degrees depending on the group, as with plants and some algae. Diploid-Dominant Life Cycle 

Nearly all animals employ a diploid-dominant life-cycle strategy in which the only haploid cells produced by the organism are the gametes. Early in the development of the embryo, specialized diploid cells, called germ cells , are produced within the gonads, such as the testes and ovaries. Germ cells are capable of mitosis to perpetuate the cell line and meiosis to produce gametes. Once the haploid gametes are formed, they lose the ability to divide again. There is no multicellular haploid life stage. Fertilization occurs with the fusion of two gametes, usually from different individuals, restoring the diploid state ( [link] ). In animals, sexually reproducing adults form haploid gametes from diploid germ cells. Fusion of the gametes gives rise to a fertilized egg cell, or zygote. The zygote will undergo multiple rounds of mitosis to produce a multicellular offspring. The germ cells are generated early in the development of the zygote. Haploid-Dominant Life Cycle 

Most fungi and algae employ a life-cycle type in which the body of the organism the ecologically important part of the life cycle is haploid. The haploid cells that make up the tissues of the dominant multicellular stage are formed by mitosis. During sexual reproduction, specialized haploid cells from two individuals, designated the (+) and ( ) mating types, join to form a diploid zygote. The zygote immediately undergoes meiosis to form four haploid cells called spores. Although haploid like the parents, these spores contain a new genetic combination from two parents. The spores can remain dormant for various time periods. Eventually, when conditions are conducive, the spores form multicellular haploid structures by many rounds of mitosis ( [link] ). 

Fungi, such as black bread mold ( Rhizopus nigricans ), have haploid-dominant life cycles. The haploid multicellular stage produces specialized haploid cells by mitosis that fuse to form a diploid zygote. The zygote undergoes meiosis to produce haploid spores. Each spore gives rise to a multicellular haploid organism by mitosis. (credit zygomycota micrograph: modification of work by Fanaberka /Wikimedia Commons) 

[link] Alternation of Generations 

The third life-cycle type, employed by some algae and all plants, is a blend of the haploid-dominant and diploid-dominant extremes. Species with alternation of generations have both haploid and diploid multicellular organisms as part of their life cycle. The haploid multicellular plants are called gametophytes , because they produce gametes from specialized cells. Meiosis is not directly involved in the production of gametes in this case, because the organism that produces the gametes is already a haploid. Fertilization between the gametes forms a diploid zygote. The zygote will undergo many rounds of mitosis and give rise to a diploid multicellular plant called a sporophyte . Specialized cells of the sporophyte will undergo meiosis and produce haploid spores. The spores will subsequently develop into the gametophytes ( [link] ). Plants have a life cycle that alternates between a multicellular haploid organism and a multicellular diploid organism. In some plants, such as ferns, both the haploid and diploid plant stages are free-living. The diploid plant is called a sporophyte because it produces haploid spores by meiosis. The spores develop into multicellular, haploid plants called gametophytes because they produce gametes. The gametes of two individuals will fuse to form a diploid zygote that becomes the sporophyte. (credit fern : modification of work by Cory Zanker; credit sporangia : modification of work by "Obsidian Soul"/Wikimedia Commons; credit gametophyte and sporophyte : modification of work by Vlmastra /Wikimedia Commons) 

Although all plants utilize some version of the alternation of generations, the relative size of the sporophyte and the gametophyte and the relationship between them vary greatly. In plants such as moss, the gametophyte organism is the free-living plant, and the sporophyte is physically dependent on the gametophyte. In other plants, such as ferns, both the gametophyte and sporophyte plants are free-living; however, the sporophyte is much larger. In seed plants, such as magnolia trees and daisies, the gametophyte is composed of only a few cells and, in the case of the female gametophyte, is completely retained within the sporophyte. 

Sexual reproduction takes many forms in multicellular organisms. However, at some point in each type of life cycle, meiosis produces haploid cells that will fuse with the haploid cell of another organism. The mechanisms of variation crossover, random assortment of homologous chromosomes, and random fertilization are present in all versions of sexual reproduction. The fact that nearly every multicellular organism on Earth employs sexual reproduction is strong evidence for the benefits of producing offspring with unique gene combinations, though there are other possible benefits as well. Think About It 

Compare and contrast the three main types of life cycles in multicellular organisms and give an example of an organism that employs each. 

This question is an application of learning objective 3.27 and science practice 7.2 because students are comparing processes by which genetic variation is produced and maintained in different types of organisms. 

Describe in simple terms the three main types of life cycles in multicellular organisms and give an example of an organism that employs each. Possible Answer 

1. diploid-dominant, in which the multicellular diploid stage is dominant; examples are most animals, including humans 

2. haploid-dominant, in which the multicellular haploid stage is dominant; examples are all fungi and some algae 

3. alternation of generations, in which two stages are apparent to different degrees depending on the group; examples are plants and some algae Section Summary 

Nearly all eukaryotes undergo sexual reproduction. The variation introduced into the reproductive cells by meiosis appears to be one of the advantages of sexual reproduction that has made it so successful. Meiosis and fertilization alternate in sexual life cycles. The process of meiosis produces unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition. Thus, sexually reproducing organisms alternate between haploid and diploid stages. However, the ways in which reproductive cells are produced and the timing between meiosis and fertilization vary greatly. There are three main categories of life cycles: diploid-dominant, demonstrated by most animals; haploid-dominant, demonstrated by all fungi and some algae; and the alternation of generations, demonstrated by plants and some algae. Review Questions 

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Leigh Van Valen, A New Evolutionary Law, Evolutionary Theory 1 (1973): 1 30 Glossary alternation of generations life-cycle type in which the diploid and haploid stages alternate diploid-dominant life-cycle type in which the multicellular diploid stage is prevalent haploid-dominant life-cycle type in which the multicellular haploid stage is prevalent gametophyte a multicellular haploid life-cycle stage that produces gametes germ cells specialized cell line that produces gametes, such as eggs or sperm life cycle the sequence of events in the development of an organism and the production of cells that produce offspring sporophyte a multicellular diploid life-cycle stage that produces haploid spores by meiosisIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Experimenting with thousands of garden peas, Mendel uncovered the fundamentals of genetics. (credit: modification of work by Jerry Kirkhart) 

During the 19 th century, long before chromosomes or genes had been identified, Johann Gregor Mendel set the framework for genetics by studying a simple biological system, the garden pea. He conducted methodical, quantitative analyses using large sample sizes. Mendel s work laid the foundation for the fundamental principles of heredity. We now know that genes, carried on chromosomes, are the basic functional units of heredity with the capacity to be replicated, expressed, repressed, modified and mutated. Today, the postulates put forth by Mendel form the basis of classical, or Mendelian, genetics. Genes do not all obey the tenets of Mendelian genetics, but Mendel s experiments serve as an excellent starting point for thinking about inheritance. 

An understanding of genetic inheritance enables scientists to study and explain complex phenomena. For example, scientists studied the remains of 84 ancient dogs from North and South America. They found that some of the dogs had greater genetic diversity, indicating that these dogs might have interbred with American wolves. Other dogs in their sample had low diversity, indicating that ancient humans were purposely breeding dogs. The study also found that dogs migrated to the Americas with humans only about 10,000 years ago. You can read more about this fascinating story here . 

Introduce the topic of genetics to the students. Ask them what they think genetics is about. Can it explain why children resemble their parents? This warm up is a good opportunity to assess how familiar students are with the topic, which is very often front page news and usually poorly explained or misunderstood. Present the warm up topic of dogs interbreeding with wolves and the concepts of humans breeding animals and plants. It will be an opportunity to remind students that genetically modified organisms are not a new concept. What is new is the modification of traits at the molecular level. 

Ask students if they like Brussels sprouts or broccoli. Usually there is a diversity of responses. Some truly hate them while other students will insist that they are very good. Tell them that their genes can contribute to their like or dislike of these vegetables. Ask students to look at their hairlines and compare. The widow s peak is considered dominant and, for simplification purposes, a monogenic trait.Mendel s Experiments and the Laws of Probability Mendel s Experiments and the Laws of Probability 

In this section, you will explore the following questions: Why was Mendel s experimental work so successful? How do the sum and product rules of probability predict the outcomes of monohybrid crosses involving dominant and recessive alleles? Connection for AP Courses 

Genetics is the science of heredity. Austrian monk Gregor Mendel set the framework for genetics long before chromosomes or genes had been identified, at a time when meiosis was not well understood. Working with garden peas, Mendel found that crosses between true-breading parents (P) that differed in one trait (e.g., color: green peas versus yellow peas) produced first generation (F1) offspring that all expressed the trait of one parent (e.g., all green or all yellow). Mendel used the term dominant to refer to the trait that was observed, and recessive to denote that non-expressed trait, or the trait that had disappeared in this first generation. When the F1 offspring were crossed with each other, the F2 offspring exhibited both traits in a 3:1 ratio. Other crosses (e.g., height: tall plants versus short plants) generated the same 3:1 ratio (in this example, tall to short) in the F2 offspring. By mathematically examining sample sizes, Mendel showed that genetic crosses behaved according to the laws of probability, and that the traits were inherited as independent events. In other words, Mendel used statistical methods to build his model of inheritance. 

As you have likely noticed, the AP Biology course emphasizes the application of mathematics. Two rules of probability can be used to find the expected proportions of different traits in offspring from different crosses. To find the probability of two or more independent events (events where the outcome of one event has no influence on the outcome of the other event) occurring together, apply the product rule and multiply the probabilities of the individual events. To find the probability that one of two or more events occur, apply the sum rule and add their probabilities together. 

The content presented in this section supports the learning objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The AP learning objectives merge essential knowledge content with one or more of the seven science practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.3 The chromosomal basis of inheritance proposed by Mendel provides an understanding of the pattern of passage of genes from parent to offspring. Science Practice 3.1 The student can pose scientific questions. Learning Objective 3.13 The student is able to pose questions about ethical, social, or medical issues surrounding human genetic disorders. Essential Knowledge 3.A.3 The chromosomal basis of inheritance proposed by Mendel provides an understanding of the pattern of passage of genes from parent to offspring. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 3.14 The student is able to apply mathematical routines to determine Mendelian patterns of inheritance provided by data sets. 

Two rules of probability are used in solving genetics problems: the rule of multiplication and the rule of addition. The probability that independent events will occur simultaneously is the product of their individual probabilities. If two dices are tossed, what is the probability of landing two ones? A die has 6 faces, and assuming the die is not loaded, each face has the same probability of outcome. The probability of obtaining the number 1 is equal to the number on the die divided by the total number of sides: 1 6 1 6 . The probability of rolling two ones is equal to 1 6 1 6 = 1 36 1 6 1 6 = 1 36 . 

The probability that any one of a set of mutually exclusive events will occur is the sum of their individual probabilities. The probability of rolling a 1 or a 2 is equal to 1 6 + 1 6 = 1 3 1 6 + 1 6 = 1 3 because the two outcomes are mutually exclusive. If we roll a 1, it cannot be a 2. 

Tell students that Gregor Mendel was a monk who had received a solid scientific education and had excelled at mathematics. He brought this knowledge of science into his experiments with peas. 

Engage students in describing what makes a good organism to study genetics. One approach is to ask the class if they would use elephants to study genetics. The disadvantages of using elephants actually highlight the advantages of using peas, corn, fruit flies, or mice for genetics studies: short life cycle, easy to maintain and handle, large number of offspring for statistical analysis, etc. 

The concepts of statistics are not intuitive. Practice with dice and coins. Explain that the probability ratios are achieved with large numbers of trials. 

Dominant traits are the ones expressed in a dominant/recessive situation. They do not usually repress the recessive trait. A dominant trait is not necessarily the most common trait in a population. For example, type O blood is a recessive trait, but it is the most frequent blood group in many ethnic groups. A dominant trait can be lethal. A dominant allele is not better than the recessive allele. Whether a trait is beneficial depends on the environment. Give the example of wing color in moths. Dark pigmentation is beneficial in a polluted environment where predators would not pick up the moths on dark tree barks. For example, the population peppered moths in 19th century London shifted so that their wing colors were darker to blend in with the soot of the Industrial Revolution. After pollution levels dropped, light pigmentation became more prevalent because it helped the moths to escape notice. Johann Gregor Mendel is considered the father of genetics. 

Johann Gregor Mendel (1822 1884) ( [link] ) was a lifelong learner, teacher, scientist, and man of faith. As a young adult, he joined the Augustinian Abbey of St. Thomas in Brno in what is now the Czech Republic. Supported by the monastery, he taught physics, botany, and natural science courses at the secondary and university levels. In 1856, he began a decade-long research pursuit involving inheritance patterns in honeybees and plants, ultimately settling on pea plants as his primary model system (a system with convenient characteristics used to study a specific biological phenomenon to be applied to other systems). In 1865, Mendel presented the results of his experiments with nearly 30,000 pea plants to the local Natural History Society. He demonstrated that traits are transmitted faithfully from parents to offspring independently of other traits and in dominant and recessive patterns. In 1866, he published his work, Experiments in Plant Hybridization, 1 in the proceedings of the Natural History Society of Br nn. 

Mendel s work went virtually unnoticed by the scientific community that believed, incorrectly, that the process of inheritance involved a blending of parental traits that produced an intermediate physical appearance in offspring; this hypothetical process appeared to be correct because of what we know now as continuous variation. Continuous variation results from the action of many genes to determine a characteristic like human height. Offspring appear to be a blend of their parents traits when we look at characteristics that exhibit continuous variation. The blending theory of inheritance asserted that the original parental traits were lost or absorbed by the blending in the offspring, but we now know that this is not the case. Mendel was the first researcher to see it. Instead of continuous characteristics, Mendel worked with traits that were inherited in distinct classes (specifically, violet versus white flowers); this is referred to as discontinuous variation . Mendel s choice of these kinds of traits allowed him to see experimentally that the traits were not blended in the offspring, nor were they absorbed, but rather that they kept their distinctness and could be passed on. In 1868, Mendel became abbot of the monastery and exchanged his scientific pursuits for his pastoral duties. He was not recognized for his extraordinary scientific contributions during his lifetime. In fact, it was not until 1900 that his work was rediscovered, reproduced, and revitalized by scientists on the brink of discovering the chromosomal basis of heredity. Mendel s Model System 

Mendel s seminal work was accomplished using the garden pea, Pisum sativum , to study inheritance. This species naturally self-fertilizes, such that pollen encounters ova within individual flowers. The flower petals remain sealed tightly until after pollination, preventing pollination from other plants. The result is highly inbred, or true-breeding, pea plants. These are plants that always produce offspring that look like the parent. By experimenting with true-breeding pea plants, Mendel avoided the appearance of unexpected traits in offspring that might occur if the plants were not true breeding. The garden pea also grows to maturity within one season, meaning that several generations could be evaluated over a relatively short time. Finally, large quantities of garden peas could be cultivated simultaneously, allowing Mendel to conclude that his results did not come about simply by chance. Mendelian Crosses 

Mendel performed hybridizations , which involve mating two true-breeding individuals that have different traits. In the pea, which is naturally self-pollinating, this is done by manually transferring pollen from the anther of a mature pea plant of one variety to the stigma of a separate mature pea plant of the second variety. In plants, pollen carries the male gametes (sperm) to the stigma, a sticky organ that traps pollen and allows the sperm to move down the pistil to the female gametes (ova) below. To prevent the pea plant that was receiving pollen from self-fertilizing and confounding his results, Mendel painstakingly removed all of the anthers from the plant s flowers before they had a chance to mature. 

Plants used in first-generation crosses were called P 0 , or parental generation one, plants ( [link] ). Mendel collected the seeds belonging to the P 0 plants that resulted from each cross and grew them the following season. These offspring were called the F 1 , or the first filial ( filial = offspring, daughter or son), generation. Once Mendel examined the characteristics in the F 1 generation of plants, he allowed them to self-fertilize naturally. He then collected and grew the seeds from the F 1 plants to produce the F 2 , or second filial, generation. Mendel s experiments extended beyond the F 2 generation to the F 3 and F 4 generations, and so on, but it was the ratio of characteristics in the P 0 F 1 F 2 generations that were the most intriguing and became the basis for Mendel s postulates. In one of his experiments on inheritance patterns, Mendel crossed plants that were true-breeding for violet flower color with plants true-breeding for white flower color (the P generation). The resulting hybrids in the F 1 generation all had violet flowers. In the F 2 generation, approximately three quarters of the plants had violet flowers, and one quarter had white flowers. Garden Pea Characteristics Revealed the Basics of Heredity 

In his 1865 publication, Mendel reported the results of his crosses involving seven different characteristics, each with two contrasting traits. A trait is defined as a variation in the physical appearance of a heritable characteristic. The characteristics included plant height, seed texture, seed color, flower color, pea pod size, pea pod color, and flower position. For the characteristic of flower color, for example, the two contrasting traits were white versus violet. To fully examine each characteristic, Mendel generated large numbers of F 1 and F 2 plants, reporting results from 19,959 F 2 plants alone. His findings were consistent. 

What results did Mendel find in his crosses for flower color? First, Mendel confirmed that he had plants that bred true for white or violet flower color. Regardless of how many generations Mendel examined, all self-crossed offspring of parents with white flowers had white flowers, and all self-crossed offspring of parents with violet flowers had violet flowers. In addition, Mendel confirmed that, other than flower color, the pea plants were physically identical. 

Once these validations were complete, Mendel applied the pollen from a plant with violet flowers to the stigma of a plant with white flowers. After gathering and sowing the seeds that resulted from this cross, Mendel found that 100 percent of the F 1 hybrid generation had violet flowers. Conventional wisdom at that time would have predicted the hybrid flowers to be pale violet or for hybrid plants to have equal numbers of white and violet flowers. In other words, the contrasting parental traits were expected to blend in the offspring. Instead, Mendel s results demonstrated that the white flower trait in the F 1 generation had completely disappeared. 

Importantly, Mendel did not stop his experimentation there. He allowed the F 1 plants to self-fertilize and found that, of F 2 -generation plants, 705 had violet flowers and 224 had white flowers. This was a ratio of 3.15 violet flowers per one white flower, or approximately 3:1. When Mendel transferred pollen from a plant with violet flowers to the stigma of a plant with white flowers and vice versa, he obtained about the same ratio regardless of which parent, male or female, contributed which trait. This is called a reciprocal cross a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross. For the other six characteristics Mendel examined, the F 1 and F 2 generations behaved in the same way as they had for flower color. One of the two traits would disappear completely from the F 1 generation only to reappear in the F 2 generation at a ratio of approximately 3:1 ( [link] ). The Results of Mendel s Garden Pea Hybridizations Characteristic Contrasting P 0 Traits F 1 Offspring Traits F 2 Offspring Traits F 2 Trait Ratios Flower color Violet vs. white 100 percent violet 705 violet 224 white 3.15:1 Flower position Axial vs. terminal 100 percent axial 651 axial 207 terminal 3.14:1 Plant height Tall vs. dwarf 100 percent tall 787 tall 277 dwarf 2.84:1 Seed texture Round vs. wrinkled 100 percent round 5,474 round 1,850 wrinkled 2.96:1 Seed color Yellow vs. green 100 percent yellow 6,022 yellow 2,001 green 3.01:1 Pea pod texture Inflated vs. constricted 100 percent inflated 882 inflated 299 constricted 2.95:1 Pea pod color Green vs. yellow 100 percent green 428 green 152 yellow 2.82:1 

Upon compiling his results for many thousands of plants, Mendel concluded that the characteristics could be divided into expressed and latent traits. He called these, respectively, dominant and recessive traits. Dominant traits are those that are inherited unchanged in a hybridization. Recessive traits become latent, or disappear, in the offspring of a hybridization. The recessive trait does, however, reappear in the progeny of the hybrid offspring. An example of a dominant trait is the violet-flower trait. For this same characteristic (flower color), white-colored flowers are a recessive trait. The fact that the recessive trait reappeared in the F 2 generation meant that the traits remained separate (not blended) in the plants of the F 1 generation. Mendel also proposed that plants possessed two copies of the trait for the flower-color characteristic, and that each parent transmitted one of its two copies to its offspring, where they came together. Moreover, the physical observation of a dominant trait could mean that the genetic composition of the organism included two dominant versions of the characteristic or that it included one dominant and one recessive version. Conversely, the observation of a recessive trait meant that the organism lacked any dominant versions of this characteristic. 

So why did Mendel repeatedly obtain 3:1 ratios in his crosses? To understand how Mendel deduced the basic mechanisms of inheritance that lead to such ratios, we must first review the laws of probability. Think About It 

Students are performing a cross involving seed color in garden pea plants. Yellow seed color is dominant to green seed color. What F1 offspring would be expected when cross true-breeding plants with green seeds with true-breading plants with yellow seeds? Express the answer(s) as percentage. 

This question is an application of Learning Objectives 3.14 and Science Practice 2.2 because students are applying a mathematical routine (probability) to determine a Mendelian pattern of inheritance. Possible answer: 100% would be yellow seeds. The dominant trait is the only one displayed in F1. Probability Basics 

Probabilities are mathematical measures of likelihood. The empirical probability of an event is calculated by dividing the number of times the event occurs by the total number of opportunities for the event to occur. It is also possible to calculate theoretical probabilities by dividing the number of times that an event is expected to occur by the number of times that it could occur. Empirical probabilities come from observations, like those of Mendel. Theoretical probabilities come from knowing how the events are produced and assuming that the probabilities of individual outcomes are equal. A probability of one for some event indicates that it is guaranteed to occur, whereas a probability of zero indicates that it is guaranteed not to occur. An example of a genetic event is a round seed produced by a pea plant. In his experiment, Mendel demonstrated that the probability of the event round seed occurring was one in the F 1 offspring of true-breeding parents, one of which has round seeds and one of which has wrinkled seeds. When the F 1 plants were subsequently self-crossed, the probability of any given F 2 offspring having round seeds was now three out of four. In other words, in a large population of F 2 offspring chosen at random, 75 percent were expected to have round seeds, whereas 25 percent were expected to have wrinkled seeds. Using large numbers of crosses, Mendel was able to calculate probabilities and use these to predict the outcomes of other crosses. The Product Rule and Sum Rule 

Mendel demonstrated that the pea-plant characteristics he studied were transmitted as discrete units from parent to offspring. As will be discussed, Mendel also determined that different characteristics, like seed color and seed texture, were transmitted independently of one another and could be considered in separate probability analyses. For instance, performing a cross between a plant with green, wrinkled seeds and a plant with yellow, round seeds still produced offspring that had a 3:1 ratio of green:yellow seeds (ignoring seed texture) and a 3:1 ratio of round:wrinkled seeds (ignoring seed color). The characteristics of color and texture did not influence each other. 

The product rule of probability can be applied to this phenomenon of the independent transmission of characteristics. The product rule states that the probability of two independent events occurring together can be calculated by multiplying the individual probabilities of each event occurring alone. To demonstrate the product rule, imagine that you are rolling a six-sided die (D) and flipping a penny (P) at the same time. The die may roll any number from 1 6 (D # ), whereas the penny may turn up heads (P H ) or tails (P T ). The outcome of rolling the die has no effect on the outcome of flipping the penny and vice versa. There are 12 possible outcomes of this action ( [link] ), and each event is expected to occur with equal probability. Twelve Equally Likely Outcomes of Rolling a Die and Flipping a Penny Rolling Die Flipping Penny D 1 P H D 1 P T D 2 P H D 2 P T D 3 P H D 3 P T D 4 P H D 4 P T D 5 P H D 5 P T D 6 P H D 6 P T 

Of the 12 possible outcomes, the die has a 2/12 (or 1/6) probability of rolling a two, and the penny has a 6/12 (or 1/2) probability of coming up heads. By the product rule, the probability that you will obtain the combined outcome 2 and heads is: (D 2 ) x (P H ) = (1/6) x (1/2) or 1/12 ( [link] ). Notice the word and in the description of the probability. The and is a signal to apply the product rule. For example, consider how the product rule is applied to the dihybrid cross: the probability of having both dominant traits in the F 2 progeny is the product of the probabilities of having the dominant trait for each characteristic, as shown here: 3 4 3 4 = 9 16 3 4 3 4 = 9 16 

On the other hand, the sum rule of probability is applied when considering two mutually exclusive outcomes that can come about by more than one pathway. The sum rule states that the probability of the occurrence of one event or the other event, of two mutually exclusive events, is the sum of their individual probabilities. Notice the word or in the description of the probability. The or indicates that you should apply the sum rule. In this case, let s imagine you are flipping a penny (P) and a quarter (Q). What is the probability of one coin coming up heads and one coin coming up tails? This outcome can be achieved by two cases: the penny may be heads (P H ) and the quarter may be tails (Q T ), or the quarter may be heads (Q H ) and the penny may be tails (P T ). Either case fulfills the outcome. By the sum rule, we calculate the probability of obtaining one head and one tail as [(P H ) (Q T )] + [(Q H ) (P T )] = [(1/2) (1/2)] + [(1/2) (1/2)] = 1/2 ( [link] ). You should also notice that we used the product rule to calculate the probability of P H and Q T , and also the probability of P T and Q H , before we summed them. Again, the sum rule can be applied to show the probability of having just one dominant trait in the F 2 generation of a dihybrid cross: 3 16 + 3 4 = 15 16 3 16 + 3 4 = 15 16 The Product Rule and Sum Rule Product Rule Sum Rule For independent events A and B, the probability (P) of them both occurring (A and B) is (P A P B ) For mutually exclusive events A and B, the probability (P) that at least one occurs (A or B) is (P A + P B ) 

To use probability laws in practice, it is necessary to work with large sample sizes because small sample sizes are prone to deviations caused by chance. The large quantities of pea plants that Mendel examined allowed him calculate the probabilities of the traits appearing in his F 2 generation. As you will learn, this discovery meant that when parental traits were known, the offspring s traits could be predicted accurately even before fertilization. Section Summary 

Working with garden pea plants, Mendel found that crosses between parents that differed by one trait produced F 1 offspring that all expressed the traits of one parent. Observable traits are referred to as dominant, and non-expressed traits are described as recessive. When the offspring in Mendel s experiment were self-crossed, the F 2 offspring exhibited the dominant trait or the recessive trait in a 3:1 ratio, confirming that the recessive trait had been transmitted faithfully from the original P 0 parent. Reciprocal crosses generated identical F 1 and F 2 offspring ratios. By examining sample sizes, Mendel showed that his crosses behaved reproducibly according to the laws of probability, and that the traits were inherited as independent events. 

Two rules in probability can be used to find the expected proportions of offspring of different traits from different crosses. To find the probability of two or more independent events occurring together, apply the product rule and multiply the probabilities of the individual events. The use of the word and suggests the appropriate application of the product rule. To find the probability of two or more events occurring in combination, apply the sum rule and add their individual probabilities together. The use of the word or suggests the appropriate application of the sum rule. Review Questions 

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Johann Gregor Mendel, Versuche ber Pflanzenhybriden Verhandlungen des naturforschenden Vereines in Br nn, Bd. IV f r das Jahr , 1865 Abhandlungen, 3 47. [go here for the English translation here ] Glossary blending theory of inheritance hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance continuous variation inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them discontinuous variation inheritance pattern in which traits are distinct and are transmitted independently of one another dominant trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait F 1 first filial generation in a cross; the offspring of the parental generation F 2 second filial generation produced when F 1 individuals are self-crossed or fertilized with each other hybridization process of mating two individuals that differ with the goal of achieving a certain characteristic in their offspring model system species or biological system used to study a specific biological phenomenon to be applied to other different species P 0 parental generation in a cross product rule probability of two independent events occurring simultaneously can be calculated by multiplying the individual probabilities of each event occurring alone recessive trait that appears latent or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed reciprocal cross paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross sum rule probability of the occurrence of at least one of two mutually exclusive events is the sum of their individual probabilities trait variation in the physical appearance of a heritable characteristicCharacteristics and Traits Characteristics and Traits 

In this section, you will explore the following questions: What is the relationship between genotypes and phenotypes in dominant and recessive gene systems? How can a Punnett square be used to calculate expected proportions of genotypes and phenotypes in a monohybrid cross? How do phenomena such as incomplete dominance, codominance, recessive lethals, multiple alleles, and sex linkage explain deviations from Mendel s model of inheritance? Connection for AP Courses 

The characteristics that Mendel evaluated in his pea plants were each expressed as one of two versions, or traits (e.g., green peas versus yellow peas). As we will explore in more detail in later chapters, the physical expression of characteristics is accomplished through the expression of genes (sequences of DNA), carried on chromosomes. The genetic makeup of peas consists of two similar, or homologous (remember this term from Chapter 11), copies of each chromosome, one from each parent. Through meiosis, diploid organisms utilize meiosis to produce haploid (1 n ) gametes that participate in fertilization. For cases in which a single gene controls a single characteristic, such as pea color, a diploid organism has genetic copies that may or may not encode the same version of the characteristic. These gene variations (e.g., green peas versus yellow peas) are called alleles. 

Different alleles for a given gene in a diploid organism interact to express physical characteristics such as pea color in plants or hairline appearance in humans. The observable traits of an organism are referred to as its phenotype. The organism s underlying genetic makeup, i.e., the combination of alleles, is called its genotype. When diploid organisms carry the same alleles for a given trait, they are said to be homozygous for the genotype; when they carry different alleles, they are said to be heterozygous. For a gene whose expression is Mendelian (Section 12.1), homozygous dominant and heterozygous organisms will look identical; that is, they will have different genotypes but the same phenotype. The recessive allele will only be observed in homozygous recessive individuals. 

However, alleles do not always behave in dominant and recessive patterns. In other words, there are exceptions to Mendel s model of inheritance. For example, incomplete dominance describes situation in which the heterozygote exhibits a phenotype that is intermediate between the homozygous phenotypes (e.g., a pink-flowered offspring is produced from a cross between a red-flowered parent and a white-flowered parent). Codominance describes the simultaneous expression of both of the alleles in the heterozygote (e.g., human blood types). It is also common for more than two alleles of a gene to exist in a population (e.g., variations in sizes of pumpkins). In humans, as in many animals and some plants, females have two X chromosomes, and males have one X chromosome and one Y chromosome. Genes on the X chromosome are X-linked, and males inherit and express only one allele for the gene (e.g., hemophilia, color-blindness). Some alleles can also be lethal, so their phenotype will never be observed. 

Many human genetic disorders, including albinism, cystic fibrosis, and Huntington s disease can be explained on the basis of simple Mendelian inheritance patterns created by pedigree analysis. (In later Chapters we will learn how DNA analysis can be used to diagnose genetic disorders). Punnett squares are useful tools that apply the rules of probability and meiosis to predict the possible outcomes of genetic crosses. Test crosses are done to determine whether or not an individual is homozygous or heterozygous by crossing the individual with a homozygous recessive. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives (LO) listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices (SP). 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.3 The chromosomal basis of inheritance proposed by Mendel provides an understanding of the pattern of passage of genes from parent to offspring. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.12 The student is able to construct a representation (e.g., Punnett square) that connects the process of meiosis to the passage of traits from parent to offspring. Essential Knowledge 3.A.3 The chromosomal basis of inheritance proposed by Mendel provides an understanding of the pattern of passage of genes from parent to offspring. Science Practice 3.1 The student can pose scientific questions. Learning Objective 3.13 The student is able to pose questions about ethical, social or medical issues surrounding human genetic disorders. Essential Knowledge 3.A.3 The chromosomal basis of inheritance proposed by Mendel provides an understanding of the pattern of passage of genes from parent to offspring. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 3.14 The student is able to apply mathematical routines to determine Mendelian patterns of inheritance provided by data sets. Essential Knowledge 3.A.4 The inheritance patterns of many traits cannot be explained by simple Mendelian genetics. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.15 The student is able to explain deviations from Mendel s model of the inheritance of traits. Essential Knowledge 3.A.4 The inheritance patterns of many traits cannot be explained by simple Mendelian genetics. Science Practice 6.3 The student can articulate the reasons that scientific explanations and theories are refined or replaced. Learning Objective 3.16 The student is able to explain how the inheritance pattern of many traits cannot be accounted for by Mendelian genetics. Essential Knowledge 3.A.4 The inheritance patterns of many traits cannot be explained by simple Mendelian genetics. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.17 The student is able to describe representations of an appropriate example of inheritance patterns that cannot be explained by Mendel s model of the inheritance of traits. 

Emphasize to the class the importance of using a Punnett s square rather than guessing the right answer. Students should show their reasoning to solve Mendelian genetics problems. This site contains a wealth of problems. Ask students to answer questions after designing a Punnett s square. 

It is recommended to work through all problems and assessments before assigning them to students. Verify that there is only one correct answer or alert students that there might be several correct answers. 

Choose easily observable traits such as widow s peak or attached ear lobe. Divide the class into groups of 5 6 students. Each group will draw possible Punnett squares for the traits of students in their group. Because the students can only observe their phenotype, each student may have several possible Punnett squares, depending on his/her parent s genotypes. 

Another exercise to be performed by the students is measuring the distribution of tasters and non-tasters of the bitter chemical phenylthiocarbamide (PTC). Paper strips impregnated with PTC are available from scientific suppliers and can be used to survey the class. Ask students to put a strip of paper on their tongue and record the taste. Some individuals can react strongly to an intensely bitter taste, other can detect a bitter taste, and, for some, it is just insipid paper. The ability to taste PTC is controlled by the gene TAS2R38 whose taster allele is dominant over the non-taster allele. 

Detailed worksheets available at: A Tree of Genetic Traits . 

For more information, go here this site . You may also find worksheets here . For resources on human genetics visit the Online Mendelian Inheritance in Man Online Mendelian Inheritance in Man and the Genetics Home References . 

The seven characteristics that Mendel evaluated in his pea plants were each expressed as one of two versions, or traits. The physical expression of characteristics is accomplished through the expression of genes carried on chromosomes. The genetic makeup of peas consists of two similar or homologous copies of each chromosome, one from each parent. Each pair of homologous chromosomes has the same linear order of genes. In other words, peas are diploid organisms in that they have two copies of each chromosome. The same is true for many other plants and for virtually all animals. Diploid organisms utilize meiosis to produce haploid gametes, which contain one copy of each homologous chromosome that unite at fertilization to create a diploid zygote. 

For cases in which a single gene controls a single characteristic, a diploid organism has two genetic copies that may or may not encode the same version of that characteristic. Gene variants that arise by mutation and exist at the same relative locations on homologous chromosomes are called alleles . Mendel examined the inheritance of genes with just two allele forms, but it is common to encounter more than two alleles for any given gene in a natural population. Phenotypes and Genotypes 

Two alleles for a given gene in a diploid organism are expressed and interact to produce physical characteristics. The observable traits expressed by an organism are referred to as its phenotype . An organism s underlying genetic makeup, consisting of both physically visible and non-expressed alleles, is called its genotype . Mendel s hybridization experiments demonstrate the difference between phenotype and genotype. When true-breeding plants in which one parent had yellow pods and one had green pods were cross-fertilized, all of the F 1 hybrid offspring had yellow pods. That is, the hybrid offspring were phenotypically identical to the true-breeding parent with yellow pods. However, we know that the allele donated by the parent with green pods was not simply lost because it reappeared in some of the F 2 offspring. Therefore, the F 1 plants must have been genotypically different from the parent with yellow pods. 

The P 1 plants that Mendel used in his experiments were each homozygous for the trait he was studying. Diploid organisms that are homozygous at a given gene, or locus, have two identical alleles for that gene on their homologous chromosomes. Mendel s parental pea plants always bred true because both of the gametes produced carried the same trait. When P 1 plants with contrasting traits were cross-fertilized, all of the offspring were heterozygous for the contrasting trait, meaning that their genotype reflected that they had different alleles for the gene being examined. Dominant and Recessive Alleles 

Our discussion of homozygous and heterozygous organisms brings us to why the F 1 heterozygous offspring were identical to one of the parents, rather than expressing both alleles. In all seven pea-plant characteristics, one of the two contrasting alleles was dominant, and the other was recessive. Mendel called the dominant allele the expressed unit factor; the recessive allele was referred to as the latent unit factor. We now know that these so-called unit factors are actually genes on homologous chromosome pairs. For a gene that is expressed in a dominant and recessive pattern, homozygous dominant and heterozygous organisms will look identical (that is, they will have different genotypes but the same phenotype). The recessive allele will only be observed in homozygous recessive individuals ( [link] ). Human Inheritance in Dominant and Recessive Patterns Dominant Traits Recessive Traits Achondroplasia Albinism Brachydactyly Cystic fibrosis Huntington s disease Duchenne muscular dystrophy Marfan syndrome Galactosemia Neurofibromatosis Phenylketonuria Widow s peak Sickle-cell anemia Wooly hair Tay-Sachs disease 

Several conventions exist for referring to genes and alleles. For the purposes of this chapter, we will abbreviate genes using the first letter of the gene s corresponding dominant trait. For example, violet is the dominant trait for a pea plant s flower color, so the flower-color gene would be abbreviated as V (note that it is customary to italicize gene designations). Furthermore, we will use uppercase and lowercase letters to represent dominant and recessive alleles, respectively. Therefore, we would refer to the genotype of a homozygous dominant pea plant with violet flowers as VV , a homozygous recessive pea plant with white flowers as vv , and a heterozygous pea plant with violet flowers as Vv . The Punnett Square Approach for a Monohybrid Cross 

When fertilization occurs between two true-breeding parents that differ in only one characteristic, the process is called a monohybrid cross, and the resulting offspring are monohybrids. Mendel performed seven monohybrid crosses involving contrasting traits for each characteristic. On the basis of his results in F 1 and F 2 generations, Mendel postulated that each parent in the monohybrid cross contributed one of two paired unit factors to each offspring, and every possible combination of unit factors was equally likely. 

To demonstrate a monohybrid cross, consider the case of true-breeding pea plants with yellow versus green pea seeds. The dominant seed color is yellow; therefore, the parental genotypes were YY for the plants with yellow seeds and yy for the plants with green seeds, respectively. A Punnett square , devised by the British geneticist Reginald Punnett, can be drawn that applies the rules of probability to predict the possible outcomes of a genetic cross or mating and their expected frequencies. To prepare a Punnett square, all possible combinations of the parental alleles are listed along the top (for one parent) and side (for the other parent) of a grid, representing their meiotic segregation into haploid gametes. Then the combinations of egg and sperm are made in the boxes in the table to show which alleles are combining. Each box then represents the diploid genotype of a zygote, or fertilized egg, that could result from this mating. Because each possibility is equally likely, genotypic ratios can be determined from a Punnett square. If the pattern of inheritance (dominant or recessive) is known, the phenotypic ratios can be inferred as well. For a monohybrid cross of two true-breeding parents, each parent contributes one type of allele. In this case, only one genotype is possible. All offspring are Yy and have yellow seeds ( [link] ). In the P generation, pea plants that are true-breeding for the dominant yellow phenotype are crossed with plants with the recessive green phenotype. This cross produces F 1 heterozygotes with a yellow phenotype. Punnett square analysis can be used to predict the genotypes of the F 2 generation. 

A self-cross of one of the Yy heterozygous offspring can be represented in a 2 2 Punnett square because each parent can donate one of two different alleles. Therefore, the offspring can potentially have one of four allele combinations: YY , Yy , yY , or yy ( [link] ). Notice that there are two ways to obtain the Yy genotype: a Y from the egg and a y from the sperm, or a y from the egg and a Y from the sperm. Both of these possibilities must be counted. Recall that Mendel s pea-plant characteristics behaved in the same way in reciprocal crosses. Therefore, the two possible heterozygous combinations produce offspring that are genotypically and phenotypically identical despite their dominant and recessive alleles deriving from different parents. They are grouped together. Because fertilization is a random event, we expect each combination to be equally likely and for the offspring to exhibit a ratio of YY : Yy : yy genotypes of 1:2:1 ( [link] ). Furthermore, because the YY and Yy offspring have yellow seeds and are phenotypically identical, applying the sum rule of probability, we expect the offspring to exhibit a phenotypic ratio of 3 yellow:1 green. Indeed, working with large sample sizes, Mendel observed approximately this ratio in every F 2 generation resulting from crosses for individual traits. 

Mendel validated these results by performing an F 3 cross in which he self-crossed the dominant- and recessive-expressing F 2 plants. When he self-crossed the plants expressing green seeds, all of the offspring had green seeds, confirming that all green seeds had homozygous genotypes of yy . When he self-crossed the F 2 plants expressing yellow seeds, he found that one-third of the plants bred true, and two-thirds of the plants segregated at a 3:1 ratio of yellow:green seeds. In this case, the true-breeding plants had homozygous ( YY ) genotypes, whereas the segregating plants corresponded to the heterozygous ( Yy ) genotype. When these plants self-fertilized, the outcome was just like the F 1 self-fertilizing cross. The Test Cross Distinguishes the Dominant Phenotype 

Beyond predicting the offspring of a cross between known homozygous or heterozygous parents, Mendel also developed a way to determine whether an organism that expressed a dominant trait was a heterozygote or a homozygote. Called the test cross , this technique is still used by plant and animal breeders. In a test cross, the dominant-expressing organism is crossed with an organism that is homozygous recessive for the same characteristic. If the dominant-expressing organism is a homozygote, then all F 1 offspring will be heterozygotes expressing the dominant trait ( [link] ). Alternatively, if the dominant expressing organism is a heterozygote, the F 1 offspring will exhibit a 1:1 ratio of heterozygotes and recessive homozygotes ( [link] ). The test cross further validates Mendel s postulate that pairs of unit factors segregate equally. 

A test cross can be performed to determine whether an organism expressing a dominant trait is a homozygote or a heterozygote. 

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Many human diseases are genetically inherited. A healthy person in a family in which some members suffer from a recessive genetic disorder may want to know if he or she has the disease-causing gene and what risk exists of passing the disorder on to his or her offspring. Of course, doing a test cross in humans is unethical and impractical. Instead, geneticists use pedigree analysis to study the inheritance pattern of human genetic diseases ( [link] ). 

Alkaptonuria is a recessive genetic disorder in which two amino acids, phenylalanine and tyrosine, are not properly metabolized. Affected individuals may have darkened skin and brown urine, and may suffer joint damage and other complications. In this pedigree, individuals with the disorder are indicated in blue and have the genotype aa . Unaffected individuals are indicated in yellow and have the genotype AA or Aa . Note that it is often possible to determine a person s genotype from the genotype of their offspring. For example, if neither parent has the disorder but their child does, they must be heterozygous. Two individuals on the pedigree have an unaffected phenotype but unknown genotype. Because they do not have the disorder, they must have at least one normal allele, so their genotype gets the A? designation. 

[link] Alternatives to Dominance and Recessiveness 

Mendel s experiments with pea plants suggested that: (1) two units or alleles exist for every gene; (2) alleles maintain their integrity in each generation (no blending); and (3) in the presence of the dominant allele, the recessive allele is hidden and makes no contribution to the phenotype. Therefore, recessive alleles can be carried and not expressed by individuals. Such heterozygous individuals are sometimes referred to as carriers. Further genetic studies in other plants and animals have shown that much more complexity exists, but that the fundamental principles of Mendelian genetics still hold true. In the sections to follow, we consider some of the extensions of Mendelism. If Mendel had chosen an experimental system that exhibited these genetic complexities, it s possible that he would not have understood what his results meant. Incomplete Dominance 

Mendel s results, that traits are inherited as dominant and recessive pairs, contradicted the view at that time that offspring exhibited a blend of their parents traits. However, the heterozygote phenotype occasionally does appear to be intermediate between the two parents. For example, in the snapdragon, Antirrhinum majus ( [link] ), a cross between a homozygous parent with white flowers ( C W C W ) and a homozygous parent with red flowers ( C R C R ) will produce offspring with pink flowers ( C R C W ). (Note that different genotypic abbreviations are used for Mendelian extensions to distinguish these patterns from simple dominance and recessiveness.) This pattern of inheritance is described as incomplete dominance , denoting the expression of two contrasting alleles such that the individual displays an intermediate phenotype. The allele for red flowers is incompletely dominant over the allele for white flowers. However, the results of a heterozygote self-cross can still be predicted, just as with Mendelian dominant and recessive crosses. In this case, the genotypic ratio would be 1 C R C R :2 C R C W :1 C W C W , and the phenotypic ratio would be 1:2:1 for red:pink:white. These pink flowers of a heterozygote snapdragon result from incomplete dominance. (credit: storebukkebruse /Flickr) Codominance 

A variation on incomplete dominance is codominance , in which both alleles for the same characteristic are simultaneously expressed in the heterozygote. An example of codominance is the MN blood groups of humans. The M and N alleles are expressed in the form of an M or N antigen present on the surface of red blood cells. Homozygotes ( L M L M and L N L N ) express either the M or the N allele, and heterozygotes ( L M L N ) express both alleles equally. In a self-cross between heterozygotes expressing a codominant trait, the three possible offspring genotypes are phenotypically distinct. However, the 1:2:1 genotypic ratio characteristic of a Mendelian monohybrid cross still applies. Multiple Alleles 

Mendel implied that only two alleles, one dominant and one recessive, could exist for a given gene. We now know that this is an oversimplification. Although individual humans (and all diploid organisms) can only have two alleles for a given gene, multiple alleles may exist at the population level such that many combinations of two alleles are observed. Note that when many alleles exist for the same gene, the convention is to denote the most common phenotype or genotype among wild animals as the wild type (often abbreviated + ); this is considered the standard or norm. All other phenotypes or genotypes are considered variants of this standard, meaning that they deviate from the wild type. The variant may be recessive or dominant to the wild-type allele. 

An example of multiple alleles is coat color in rabbits ( [link] ). Here, four alleles exist for the c gene. The wild-type version, C + C + , is expressed as brown fur. The chinchilla phenotype, c ch c ch , is expressed as black-tipped white fur. The Himalayan phenotype, c h c h , has black fur on the extremities and white fur elsewhere. Finally, the albino, or colorless phenotype, cc , is expressed as white fur. In cases of multiple alleles, dominance hierarchies can exist. In this case, the wild-type allele is dominant over all the others, chinchilla is incompletely dominant over Himalayan and albino, and Himalayan is dominant over albino. This hierarchy, or allelic series, was revealed by observing the phenotypes of each possible heterozygote offspring. Four different alleles exist for the rabbit coat color ( C ) gene. 

The complete dominance of a wild-type phenotype over all other mutants often occurs as an effect of dosage of a specific gene product, such that the wild-type allele supplies the correct amount of gene product whereas the mutant alleles cannot. For the allelic series in rabbits, the wild-type allele may supply a given dosage of fur pigment, whereas the mutants supply a lesser dosage or none at all. Interestingly, the Himalayan phenotype is the result of an allele that produces a temperature-sensitive gene product that only produces pigment in the cooler extremities of the rabbit s body. 

Alternatively, one mutant allele can be dominant over all other phenotypes, including the wild type. This may occur when the mutant allele somehow interferes with the genetic message so that even a heterozygote with one wild-type allele copy expresses the mutant phenotype. One way in which the mutant allele can interfere is by enhancing the function of the wild-type gene product or changing its distribution in the body. One example of this is the Antennapedia mutation in Drosophila ( [link] ). In this case, the mutant allele expands the distribution of the gene product, and as a result, the Antennapedia heterozygote develops legs on its head where its antennae should be. As seen in comparing the wild-type Drosophila (left) and the Antennapedia mutant (right), the Antennapedia mutant has legs on its head in place of antennae. 

Multiple Alleles Confer Drug Resistance in the Malaria Parasite Malaria is a parasitic disease in humans that is transmitted by infected female mosquitoes, including Anopheles gambiae ( [link] a ), and is characterized by cyclic high fevers, chills, flu-like symptoms, and severe anemia. Plasmodium falciparum and P. vivax are the most common causative agents of malaria, and P. falciparum is the most deadly ( [link] b ) . When promptly and correctly treated, P. falciparum malaria has a mortality rate of 0.1 percent. However, in some parts of the world, the parasite has evolved resistance to commonly used malaria treatments, so the most effective malarial treatments can vary by geographic region. The (a) Anopheles gambiae , or African malaria mosquito, acts as a vector in the transmission to humans of the malaria-causing parasite (b) Plasmodium falciparum , here visualized using false-color transmission electron microscopy. (credit a: James D. Gathany; credit b: Ute Frevert; false color by Margaret Shear; scale-bar data from Matt Russell) 

In Southeast Asia, Africa, and South America, P. falciparum has developed resistance to the anti-malarial drugs chloroquine, mefloquine, and sulfadoxine-pyrimethamine. P. falciparum , which is haploid during the life stage in which it is infectious to humans, has evolved multiple drug-resistant mutant alleles of the dhps gene. Varying degrees of sulfadoxine resistance are associated with each of these alleles. Being haploid, P. falciparum needs only one drug-resistant allele to express this trait. 

In Southeast Asia, different sulfadoxine-resistant alleles of the dhps gene are localized to different geographic regions. This is a common evolutionary phenomenon that occurs because drug-resistant mutants arise in a population and interbreed with other P. falciparum isolates in close proximity. Sulfadoxine-resistant parasites cause considerable human hardship in regions where this drug is widely used as an over-the-counter malaria remedy. As is common with pathogens that multiply to large numbers within an infection cycle, P. falciparum evolves relatively rapidly (over a decade or so) in response to the selective pressure of commonly used anti-malarial drugs. For this reason, scientists must constantly work to develop new drugs or drug combinations to combat the worldwide malaria burden. 1 

[link] X-Linked Traits 

In humans, as well as in many other animals and some plants, the sex of the individual is determined by sex chromosomes. The sex chromosomes are one pair of non-homologous chromosomes. Until now, we have only considered inheritance patterns among non-sex chromosomes, or autosomes . In addition to 22 homologous pairs of autosomes, human females have a homologous pair of X chromosomes, whereas human males have an XY chromosome pair. Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains many fewer genes. When a gene being examined is present on the X chromosome, but not on the Y chromosome, it is said to be X-linked . 

Eye color in Drosophila was one of the first X-linked traits to be identified. Thomas Hunt Morgan mapped this trait to the X chromosome in 1910. Like humans, Drosophila males have an XY chromosome pair, and females are XX. In flies, the wild-type eye color is red (X W ) and it is dominant to white eye color (X w ) ( [link] ). Because of the location of the eye-color gene, reciprocal crosses do not produce the same offspring ratios. Males are said to be hemizygous , because they have only one allele for any X-linked characteristic. Hemizygosity makes the descriptions of dominance and recessiveness irrelevant for XY males. Drosophila males lack a second allele copy on the Y chromosome; that is, their genotype can only be X W Y or X w Y. In contrast, females have two allele copies of this gene and can be X W X W , X W X w , or X w X w . In Drosophila , the gene for eye color is located on the X chromosome. Clockwise from top left are brown, cinnabar, sepia, vermilion, white, and red. Red eye color is wild-type and is dominant to white eye color. 

In an X-linked cross, the genotypes of F 1 and F 2 offspring depend on whether the recessive trait was expressed by the male or the female in the P 1 generation. With regard to Drosophila eye color, when the P 1 male expresses the white-eye phenotype and the female is homozygous red-eyed, all members of the F 1 generation exhibit red eyes ( [link] ). The F 1 females are heterozygous (X W X w ), and the males are all X W Y, having received their X chromosome from the homozygous dominant P 1 female and their Y chromosome from the P 1 male. A subsequent cross between the X W X w female and the X W Y male would produce only red-eyed females (with X W X W or X W X w genotypes) and both red- and white-eyed males (with X W Y or X w Y genotypes). Now, consider a cross between a homozygous white-eyed female and a male with red eyes. The F 1 generation would exhibit only heterozygous red-eyed females (X W X w ) and only white-eyed males (X w Y). Half of the F 2 females would be red-eyed (X W X w ) and half would be white-eyed (X w X w ). Similarly, half of the F 2 males would be red-eyed (X W Y) and half would be white-eyed (X w Y). 

Punnett square analysis is used to determine the ratio of offspring from a cross between a red-eyed male fruit fly and a white-eyed female fruit fly. 

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Discoveries in fruit fly genetics can be applied to human genetics. When a female parent is homozygous for a recessive X-linked trait, she will pass the trait on to 100 percent of her offspring. Her male offspring are, therefore, destined to express the trait, as they will inherit their father's Y chromosome. In humans, the alleles for certain conditions (some forms of color blindness, hemophilia, and muscular dystrophy) are X-linked. Females who are heterozygous for these diseases are said to be carriers and may not exhibit any phenotypic effects. These females will pass the disease to half of their sons and will pass carrier status to half of their daughters; therefore, recessive X-linked traits appear more frequently in males than females. 

In some groups of organisms with sex chromosomes, the gender with the non-homologous sex chromosomes is the female rather than the male. This is the case for all birds. In this case, sex-linked traits will be more likely to appear in the female, in which they are hemizygous. Human Sex-linked Disorders 

Sex-linkage studies in Morgan s laboratory provided the fundamentals for understanding X-linked recessive disorders in humans, which include red-green color blindness, and Types A and B hemophilia. Because human males need to inherit only one recessive mutant X allele to be affected, X-linked disorders are disproportionately observed in males. Females must inherit recessive X-linked alleles from both of their parents in order to express the trait. When they inherit one recessive X-linked mutant allele and one dominant X-linked wild-type allele, they are carriers of the trait and are typically unaffected. Carrier females can manifest mild forms of the trait due to the inactivation of the dominant allele located on one of the X chromosomes. However, female carriers can contribute the trait to their sons, resulting in the son exhibiting the trait, or they can contribute the recessive allele to their daughters, resulting in the daughters being carriers of the trait ( [link] ). Although some Y-linked recessive disorders exist, typically they are associated with infertility in males and are therefore not transmitted to subsequent generations. The son of a woman who is a carrier of a recessive X-linked disorder will have a 50 percent chance of being affected. A daughter will not be affected, but she will have a 50 percent chance of being a carrier like her mother. 

Watch this video to learn more about sex-linked traits. 

[link] Lethality 

A large proportion of genes in an individual s genome are essential for survival. Occasionally, a nonfunctional allele for an essential gene can arise by mutation and be transmitted in a population as long as individuals with this allele also have a wild-type, functional copy. The wild-type allele functions at a capacity sufficient to sustain life and is therefore considered to be dominant over the nonfunctional allele. However, consider two heterozygous parents that have a genotype of wild-type/nonfunctional mutant for a hypothetical essential gene. In one quarter of their offspring, we would expect to observe individuals that are homozygous recessive for the nonfunctional allele. Because the gene is essential, these individuals might fail to develop past fertilization, die in utero , or die later in life, depending on what life stage requires this gene. An inheritance pattern in which an allele is only lethal in the homozygous form and in which the heterozygote may be normal or have some altered non-lethal phenotype is referred to as recessive lethal . 

For crosses between heterozygous individuals with a recessive lethal allele that causes death before birth when homozygous, only wild-type homozygotes and heterozygotes would be observed. The genotypic ratio would therefore be 2:1. In other instances, the recessive lethal allele might also exhibit a dominant (but not lethal) phenotype in the heterozygote. For instance, the recessive lethal Curly allele in Drosophila affects wing shape in the heterozygote form but is lethal in the homozygote. 

A single copy of the wild-type allele is not always sufficient for normal functioning or even survival. The dominant lethal inheritance pattern is one in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age. Individuals with mutations that result in dominant lethal alleles fail to survive even in the heterozygote form. Dominant lethal alleles are very rare because, as you might expect, the allele only lasts one generation and is not transmitted. However, just as the recessive lethal allele might not immediately manifest the phenotype of death, dominant lethal alleles also might not be expressed until adulthood. Once the individual reaches reproductive age, the allele may be unknowingly passed on, resulting in a delayed death in both generations. An example of this in humans is Huntington s disease, in which the nervous system gradually wastes away ( [link] ). People who are heterozygous for the dominant Huntington allele ( Hh ) will inevitably develop the fatal disease. However, the onset of Huntington s disease may not occur until age 40, at which point the afflicted persons may have already passed the allele to 50 percent of their offspring. The neuron in the center of this micrograph (yellow) has nuclear inclusions characteristic of Huntington s disease (orange area in the center of the neuron). Huntington s disease occurs when an abnormal dominant allele for the Huntington gene is present. (credit: Dr. Steven Finkbeiner, Gladstone Institute of Neurological Disease, The Taube-Koret Center for Huntington's Disease Research, and the University of California San Francisco/Wikimedia) Activity 

This section includes descriptions of genetically-inherited human diseases, such as sickle cell anemia, alkaptonuria, hemophilia, color blindness and Huntington s disease. One issue surrounding genetic disorders is the right to privacy. Can you think of other examples of ethical, social, or medical issue surrounding human genetic disorders? Lab Investigation 

Investigate inheritance patterns in an organism of choice, such as Wisconsin Fast Plants or Drosophila melanogaster , by performing several genetic crosses and comparing expected and observed phenotypic ratios. Virtual labs exploring Mendelian inheritance patterns are also available online. Think About It In pea plants, round peas ( R ) are dominant to wrinkles peas ( r ) ( [link] ). You do a test cross between a pea plant with wrinkled peas (genotype rr ) and a plant of unknown genotype that has round peas (genotype either RR or Rr ). You end up with three offspring plants, all which have round peas. Based on the phenotype of the offspring plants, can you deduce the genotype of the round pea parent plant? If the round pea parent plant is heterozygous, calculate the probability that a random sample of 3 progeny peas will all be round. Can a human male be a carrier of red-green color blindness? Justify your answer. In pea plants, violet flowers ( V ) are dominant to white flowers ( v ). What are the possible genotypes and phenotypes for a cross between Vv and vv pea plants? Use a Punnett square to show all work. The activity is an application of Learning Objective 3.13 and SP 3.1 because students are exploring issues that surround human genetic disorders. This lab investigation is an application of Learning Objective 3.12 and Science Practices 1.1 and 7.2 because students will connect the process of meiosis to the passage of traits from parent to offspring to make predictions about expected phenotypic ratios resulting from genetic crosses. Students will also apply Learning Objective 3.14 and Science Practice 2.2 because they will use mathematical routine to determine inheritance patterns provided by experimental data. The first Think About It question is an application of Learning Objective 3.12 and Science Practices 1.1 and 7.2 because students will use Punnett squares to connect the process of meiosis to the passage of traits from parent to offspring. In addition, students will use probability, a mathematical routine, to explain the inheritance pattern provided by data. The second Think About It question is an application of Learning Objective 3.15 and Science Practice 6.5 and Learning Objective 3.27 and Science Practice 1.2 because students are asked to explain an appropriate example of an inheritance pattern that deviates from Mendel s model. The third Think About It question is an application of Learning Objective 3.12 and Science Practices 1.1 and 7.2 because students will use Punnett squares to connect the process of meiosis to the passage of traits from parent to offspring. In addition, students will use probability, a mathematical routine, to explain the inheritance pattern provided by data. Possible answer to activity: Other issues might be insurance concerns, employment, and personal relationships. On the other hand, by knowing one s genetic predispositions to certain diseases, life style adjustments and treatments can be started early. There are no simple, one-size fits all answers. Be prepared for heated discussions. Possible answers to Think About It: You cannot be sure if the plant is homozygous or heterozygous as the data set is too small; by random chance, all three plants might have inherited only the dominant gene even if the recessive one is present. If the round pea parent is heterozygous, there is a one-eighth probability that a random sample of three progeny peas will all be round. No, color blindness is X-linked. A male has only one X chromosome, so red-green blindness is not masked by the normal allele. 

Violet flowers 1/2 

White flowers: 1/2 Section Summary 

When true-breeding or homozygous individuals that differ for a certain trait are crossed, all of the offspring will be heterozygotes for that trait. If the traits are inherited as dominant and recessive, the F 1 offspring will all exhibit the same phenotype as the parent homozygous for the dominant trait. If these heterozygous offspring are self-crossed, the resulting F 2 offspring will be equally likely to inherit gametes carrying the dominant or recessive trait, giving rise to offspring of which one quarter are homozygous dominant, half are heterozygous, and one quarter are homozygous recessive. Because homozygous dominant and heterozygous individuals are phenotypically identical, the observed traits in the F 2 offspring will exhibit a ratio of three dominant to one recessive. 

Alleles do not always behave in dominant and recessive patterns. Incomplete dominance describes situations in which the heterozygote exhibits a phenotype that is intermediate between the homozygous phenotypes. Codominance describes the simultaneous expression of both of the alleles in the heterozygote. Although diploid organisms can only have two alleles for any given gene, it is common for more than two alleles of a gene to exist in a population. In humans, as in many animals and some plants, females have two X chromosomes and males have one X and one Y chromosome. Genes that are present on the X but not the Y chromosome are said to be X-linked, such that males only inherit one allele for the gene, and females inherit two. Finally, some alleles can be lethal. Recessive lethal alleles are only lethal in homozygotes, but dominant lethal alleles are fatal in heterozygotes as well. Review Questions 

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Sumiti Vinayak, et al., Origin and Evolution of Sulfadoxine Resistant Plasmodium falciparum , Public Library of Science Pathogens 6, no. 3 (2010): e1000830, doi:10.1371/journal.ppat.1000830. Glossary allele gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes autosomes any of the non-sex chromosomes codominance in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic dominant lethal inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age genotype underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism hemizygous presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant heterozygous having two different alleles for a given gene on the homologous chromosome homozygous having two identical alleles for a given gene on the homologous chromosome incomplete dominance in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype monohybrid result of a cross between two true-breeding parents that express different traits for only one characteristic phenotype observable traits expressed by an organism Punnett square visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid recessive lethal inheritance pattern in which an allele is only lethal in the homozygous form; the heterozygote may be normal or have some altered, non-lethal phenotype sex-linked any gene on a sex chromosome test cross cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait X-linked gene present on the X, but not the Y chromosomeLaws of Inheritance Laws of Inheritance 

In this section, you will explore the following questions: What is the relationship between Mendel s law of segregation and independent assortment in terms of genetics and the events of meiosis? How can the forked-lined method and probability rules be used to calculate the probability of genotypes and phenotypes from multiple gene crosses? How do linkage, cross-over, epistasis, and recombination violate Mendel s laws of inheritance? Connection for AP Courses 

As was described previously, Mendel proposed that genes are inherited as pairs of alleles that behave in a dominant and recessive pattern. During meiosis, alleles segregate, or separate, such that each gamete is equally likely to receive either one of the two alleles present in the diploid individual. Mendel called this phenomenon the law of segregation, which can be demonstrated in a monohybrid cross. In addition, genes carried on different chromosomes sort into gametes independently of one another. This is Mendel s law of independent assortment. This law can be demonstrated in a dihybrid cross involving two different traits located on different chromosomes. Punnett squares can be used to predict genotypes and phenotypes of offspring involving one or two genes. 

Although chromosomes sort independently into gametes during meiosis, Mendel s law of independent assortment refers to genes, not chromosomes. In humans, single chromosomes may carry more than 1,000 genes. Genes located close together on the same chromosome are said to be linked genes. When genes are located in close proximity on the same chromosome, their alleles tend to be inherited together unless recombination occurs. This results in offspring ratios that violate Mendel s law of independent assortment. Genes that are located far apart on the same chromosome are likely to assort independently. The rules of probability can help to sort this out (pun intended). The law states that alleles of different genes assort independently of one another during gamete formation. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.3 The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 3.14 The student is able to apply mathematical routines to determine Mendelian patterns of inheritance provided by data. Essential Knowledge 3.A.4 The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.15 The student is able to explain deviations from Mendel s model of the inheritance of traits. Essential Knowledge 3.A.4 The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Science Practice 6.3 The student can articulate the reasons that scientific explanations and theories are refined or replaced. Learning Objective 3.16 The student is able to explain how the inheritance patterns of many traits cannot be accounted for by Mendelian genetics. Essential Knowledge 3.A.4 The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.17 The student is able to describe representations of an appropriate example of inheritance patterns that cannot be explained by Mendel s model of the inheritance of traits. 

Emphasize that very few traits depend on a single genes. Multiallelic traits are much more common but are much more difficult to study because of the complexity of multi-gene interactions. Cite height, skin and eye pigmentation. Also introduce the concept of environmental effects on the expression of traits (i.e. nature versus nurture). 

A good example of environmental effect is the color of petals in hydrangeas. The enzyme that converts the pigment from pink to blue requires aluminum ions as cofactors. The uptake of aluminum ions is inhibited in neutral or alkaline soils, and the blooms appear pink. Gardeners can amend acidic soil with lime to neutralize the pH. The blooms will turn to pink once the soil reaches a neutral to alkaline pH. 

Many students think that lethal or rare traits in human are always recessive. This is not the case. Huntington disease, which is fully expressed when people reach middle age, is a dominant trait. Dwarfism and polydactyly are examples of dominant traits that are not frequent in the population. 

Many students also think that genetics is as simple as the examples we use to teach Mendelian genetics. In fact, most traits diverge from Mendelian genetics. 

Mendel generalized the results of his pea-plant experiments into four postulates, some of which are sometimes called laws, that describe the basis of dominant and recessive inheritance in diploid organisms. As you have learned, more complex extensions of Mendelism exist that do not exhibit the same F 2 phenotypic ratios (3:1). Nevertheless, these laws summarize the basics of classical genetics. Pairs of Unit Factors, or Genes 

Mendel proposed first that paired unit factors of heredity were transmitted faithfully from generation to generation by the dissociation and reassociation of paired factors during gametogenesis and fertilization, respectively. After he crossed peas with contrasting traits and found that the recessive trait resurfaced in the F 2 generation, Mendel deduced that hereditary factors must be inherited as discrete units. This finding contradicted the belief at that time that parental traits were blended in the offspring. Alleles Can Be Dominant or Recessive 

Mendel s law of dominance states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. Rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively. The recessive allele will remain latent but will be transmitted to offspring by the same manner in which the dominant allele is transmitted. The recessive trait will only be expressed by offspring that have two copies of this allele ( [link] ), and these offspring will breed true when self-crossed. 

Since Mendel s experiments with pea plants, other researchers have found that the law of dominance does not always hold true. Instead, several different patterns of inheritance have been found to exist. The child in the photo expresses albinism, a recessive trait. Equal Segregation of Alleles 

Observing that true-breeding pea plants with contrasting traits gave rise to F 1 generations that all expressed the dominant trait and F 2 generations that expressed the dominant and recessive traits in a 3:1 ratio, Mendel proposed the law of segregation . This law states that paired unit factors (genes) must segregate equally into gametes such that offspring have an equal likelihood of inheriting either factor. For the F 2 generation of a monohybrid cross, the following three possible combinations of genotypes could result: homozygous dominant, heterozygous, or homozygous recessive. Because heterozygotes could arise from two different pathways (receiving one dominant and one recessive allele from either parent), and because heterozygotes and homozygous dominant individuals are phenotypically identical, the law supports Mendel s observed 3:1 phenotypic ratio. The equal segregation of alleles is the reason we can apply the Punnett square to accurately predict the offspring of parents with known genotypes. The physical basis of Mendel s law of segregation is the first division of meiosis, in which the homologous chromosomes with their different versions of each gene are segregated into daughter nuclei. The role of the meiotic segregation of chromosomes in sexual reproduction was not understood by the scientific community during Mendel s lifetime. Independent Assortment 

Mendel s law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes, and every possible combination of alleles for every gene is equally likely to occur. The independent assortment of genes can be illustrated by the dihybrid cross, a cross between two true-breeding parents that express different traits for two characteristics. Consider the characteristics of seed color and seed texture for two pea plants, one that has green, wrinkled seeds ( yyrr ) and another that has yellow, round seeds ( YYRR ). Because each parent is homozygous, the law of segregation indicates that the gametes for the green/wrinkled plant all are yr , and the gametes for the yellow/round plant are all YR . Therefore, the F 1 generation of offspring all are YyRr ( [link] ). 

This dihybrid cross of pea plants involves the genes for seed color and texture. 

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For the F2 generation, the law of segregation requires that each gamete receive either an R allele or an r allele along with either a Y allele or a y allele. The law of independent assortment states that a gamete into which an r allele sorted would be equally likely to contain either a Y allele or a y allele. Thus, there are four equally likely gametes that can be formed when the YyRr heterozygote is self-crossed, as follows: YR , Yr , yR , and yr . Arranging these gametes along the top and left of a 4 4 Punnett square ( [link] ) gives us 16 equally likely genotypic combinations. From these genotypes, we infer a phenotypic ratio of 9 round/yellow:3 round/green:3 wrinkled/yellow:1 wrinkled/green ( [link] ). These are the offspring ratios we would expect, assuming we performed the crosses with a large enough sample size. 

Because of independent assortment and dominance, the 9:3:3:1 dihybrid phenotypic ratio can be collapsed into two 3:1 ratios, characteristic of any monohybrid cross that follows a dominant and recessive pattern. Ignoring seed color and considering only seed texture in the above dihybrid cross, we would expect that three quarters of the F 2 generation offspring would be round, and one quarter would be wrinkled. Similarly, isolating only seed color, we would assume that three quarters of the F 2 offspring would be yellow and one quarter would be green. The sorting of alleles for texture and color are independent events, so we can apply the product rule. Therefore, the proportion of round and yellow F 2 offspring is expected to be (3/4) (3/4) = 9/16, and the proportion of wrinkled and green offspring is expected to be (1/4) (1/4) = 1/16. These proportions are identical to those obtained using a Punnett square. Round, green and wrinkled, yellow offspring can also be calculated using the product rule, as each of these genotypes includes one dominant and one recessive phenotype. Therefore, the proportion of each is calculated as (3/4) (1/4) = 3/16. 

The law of independent assortment also indicates that a cross between yellow, wrinkled ( YYrr ) and green, round ( yyRR ) parents would yield the same F 1 and F 2 offspring as in the YYRR x yyrr cross. 

The physical basis for the law of independent assortment also lies in meiosis I, in which the different homologous pairs line up in random orientations. Each gamete can contain any combination of paternal and maternal chromosomes (and therefore the genes on them) because the orientation of tetrads on the metaphase plane is random. Forked-Line Method 

When more than two genes are being considered, the Punnett-square method becomes unwieldy. For instance, examining a cross involving four genes would require a 16 16 grid containing 256 boxes. It would be extremely cumbersome to manually enter each genotype. For more complex crosses, the forked-line and probability methods are preferred. 

To prepare a forked-line diagram for a cross between F 1 heterozygotes resulting from a cross between AABBCC and aabbcc parents, we first create rows equal to the number of genes being considered, and then segregate the alleles in each row on forked lines according to the probabilities for individual monohybrid crosses ( [link] ). We then multiply the values along each forked path to obtain the F 2 offspring probabilities. Note that this process is a diagrammatic version of the product rule. The values along each forked pathway can be multiplied because each gene assorts independently. For a trihybrid cross, the F 2 phenotypic ratio is 27:9:9:9:3:3:3:1. The forked-line method can be used to analyze a trihybrid cross. Here, the probability for color in the F 2 generation occupies the top row (3 yellow:1 green). The probability for shape occupies the second row (3 round:1 wrinked), and the probability for height occupies the third row (3 tall:1 dwarf). The probability for each possible combination of traits is calculated by multiplying the probability for each individual trait. Thus, the probability of F 2 offspring having yellow, round, and tall traits is 3 3 3, or 27. Probability Method 

While the forked-line method is a diagrammatic approach to keeping track of probabilities in a cross, the probability method gives the proportions of offspring expected to exhibit each phenotype (or genotype) without the added visual assistance. Both methods make use of the product rule and consider the alleles for each gene separately. Earlier, we examined the phenotypic proportions for a trihybrid cross using the forked-line method; now we will use the probability method to examine the genotypic proportions for a cross with even more genes. 

For a trihybrid cross, writing out the forked-line method is tedious, albeit not as tedious as using the Punnett-square method. To fully demonstrate the power of the probability method, however, we can consider specific genetic calculations. For instance, for a tetrahybrid cross between individuals that are heterozygotes for all four genes, and in which all four genes are sorting independently and in a dominant and recessive pattern, what proportion of the offspring will be expected to be homozygous recessive for all four alleles? Rather than writing out every possible genotype, we can use the probability method. We know that for each gene, the fraction of homozygous recessive offspring will be 1/4. Therefore, multiplying this fraction for each of the four genes, (1/4) (1/4) (1/4) (1/4), we determine that 1/256 of the offspring will be quadruply homozygous recessive. 

For the same tetrahybrid cross, what is the expected proportion of offspring that have the dominant phenotype at all four loci? We can answer this question using phenotypic proportions, but let s do it the hard way using genotypic proportions. The question asks for the proportion of offspring that are 1) homozygous dominant at A or heterozygous at A, and 2) homozygous at B or heterozygous at B , and so on. Noting the or and and in each circumstance makes clear where to apply the sum and product rules. The probability of a homozygous dominant at A is 1/4 and the probability of a heterozygote at A is 1/2. The probability of the homozygote or the heterozygote is 1/4 + 1/2 = 3/4 using the sum rule. The same probability can be obtained in the same way for each of the other genes, so that the probability of a dominant phenotype at A and B and C and D is, using the product rule, equal to 3/4 3/4 3/4 3/4, or 27/64. If you are ever unsure about how to combine probabilities, returning to the forked-line method should make it clear. Rules for Multihybrid Fertilization 

Predicting the genotypes and phenotypes of offspring from given crosses is the best way to test your knowledge of Mendelian genetics. Given a multihybrid cross that obeys independent assortment and follows a dominant and recessive pattern, several generalized rules exist; you can use these rules to check your results as you work through genetics calculations ( [link] ). To apply these rules, first you must determine n , the number of heterozygous gene pairs (the number of genes segregating two alleles each). For example, a cross between AaBb and AaBb heterozygotes has an n of 2. In contrast, a cross between AABb and AABb has an n of 1 because A is not heterozygous. General Rules for Multihybrid Crosses General Rule Number of Heterozygous Gene Pairs Number of different F 1 gametes 2 n Number of different F 2 genotypes 3 n Given dominant and recessive inheritance, the number of different F 2 phenotypes 2 n Linked Genes Violate the Law of Independent Assortment 

Although all of Mendel s pea characteristics behaved according to the law of independent assortment, we now know that some allele combinations are not inherited independently of each other. Genes that are located on separate non-homologous chromosomes will always sort independently. However, each chromosome contains hundreds or thousands of genes, organized linearly on chromosomes like beads on a string. The segregation of alleles into gametes can be influenced by linkage , in which genes that are located physically close to each other on the same chromosome are more likely to be inherited as a pair. However, because of the process of recombination, or crossover, it is possible for two genes on the same chromosome to behave independently, or as if they are not linked. To understand this, let s consider the biological basis of gene linkage and recombination. 

Homologous chromosomes possess the same genes in the same linear order. The alleles may differ on homologous chromosome pairs, but the genes to which they correspond do not. In preparation for the first division of meiosis, homologous chromosomes replicate and synapse. Like genes on the homologs align with each other. At this stage, segments of homologous chromosomes exchange linear segments of genetic material ( [link] ). This process is called recombination, or crossover, and it is a common genetic process. Because the genes are aligned during recombination, the gene order is not altered. Instead, the result of recombination is that maternal and paternal alleles are combined onto the same chromosome. Across a given chromosome, several recombination events may occur, causing extensive shuffling of alleles. The process of crossover, or recombination, occurs when two homologous chromosomes align during meiosis and exchange a segment of genetic material. Here, the alleles for gene C were exchanged. The result is two recombinant and two non-recombinant chromosomes. 

When two genes are located in close proximity on the same chromosome, they are considered linked, and their alleles tend to be transmitted through meiosis together. To exemplify this, imagine a dihybrid cross involving flower color and plant height in which the genes are next to each other on the chromosome. If one homologous chromosome has alleles for tall plants and red flowers, and the other chromosome has genes for short plants and yellow flowers, then when the gametes are formed, the tall and red alleles will go together into a gamete and the short and yellow alleles will go into other gametes. These are called the parental genotypes because they have been inherited intact from the parents of the individual producing gametes. But unlike if the genes were on different chromosomes, there will be no gametes with tall and yellow alleles and no gametes with short and red alleles. If you create the Punnett square with these gametes, you will see that the classical Mendelian prediction of a 9:3:3:1 outcome of a dihybrid cross would not apply. As the distance between two genes increases, the probability of one or more crossovers between them increases, and the genes behave more like they are on separate chromosomes. Geneticists have used the proportion of recombinant gametes (the ones not like the parents) as a measure of how far apart genes are on a chromosome. Using this information, they have constructed elaborate maps of genes on chromosomes for well-studied organisms, including humans. 

Mendel s seminal publication makes no mention of linkage, and many researchers have questioned whether he encountered linkage but chose not to publish those crosses out of concern that they would invalidate his independent assortment postulate. The garden pea has seven chromosomes, and some have suggested that his choice of seven characteristics was not a coincidence. However, even if the genes he examined were not located on separate chromosomes, it is possible that he simply did not observe linkage because of the extensive shuffling effects of recombination. 

Testing the Hypothesis of Independent Assortment To better appreciate the amount of labor and ingenuity that went into Mendel s experiments, proceed through one of Mendel s dihybrid crosses. 

Question : What will be the offspring of a dihybrid cross? 

Background : Consider that pea plants mature in one growing season, and you have access to a large garden in which you can cultivate thousands of pea plants. There are several true-breeding plants with the following pairs of traits: tall plants with inflated pods, and dwarf plants with constricted pods. Before the plants have matured, you remove the pollen-producing organs from the tall/inflated plants in your crosses to prevent self-fertilization. Upon plant maturation, the plants are manually crossed by transferring pollen from the dwarf/constricted plants to the stigmata of the tall/inflated plants. 

Hypothesis : Both trait pairs will sort independently according to Mendelian laws. When the true-breeding parents are crossed, all of the F 1 offspring are tall and have inflated pods, which indicates that the tall and inflated traits are dominant over the dwarf and constricted traits, respectively. A self-cross of the F 1 heterozygotes results in 2,000 F 2 progeny. 

Test the hypothesis : Because each trait pair sorts independently, the ratios of tall:dwarf and inflated:constricted are each expected to be 3:1. The tall/dwarf trait pair is called T/t , and the inflated/constricted trait pair is designated I/i . Each member of the F 1 generation therefore has a genotype of TtIi . Construct a grid analogous to [link] , in which you cross two TtIi individuals. Each individual can donate four combinations of two traits: TI , Ti , tI , or ti , meaning that there are 16 possibilities of offspring genotypes. Because the T and I alleles are dominant, any individual having one or two of those alleles will express the tall or inflated phenotypes, respectively, regardless if they also have a t or i allele. Only individuals that are tt or ii will express the dwarf and constricted alleles, respectively. As shown in [link] , you predict that you will observe the following offspring proportions: tall/inflated:tall/constricted:dwarf/inflated:dwarf/constricted in a 9:3:3:1 ratio. Notice from the grid that when considering the tall/dwarf and inflated/constricted trait pairs in isolation, they are each inherited in 3:1 ratios. This figure shows all possible combinations of offspring resulting from a dihybrid cross of pea plants that are heterozygous for the tall/dwarf and inflated/constricted alleles. 

Test the hypothesis : You cross the dwarf and tall plants and then self-cross the offspring. For best results, this is repeated with hundreds or even thousands of pea plants. What special precautions should be taken in the crosses and in growing the plants? 

Analyze your data : You observe the following plant phenotypes in the F 2 generation: 2706 tall/inflated, 930 tall/constricted, 888 dwarf/inflated, and 300 dwarf/constricted. Reduce these findings to a ratio and determine if they are consistent with Mendelian laws. 

Form a conclusion : Were the results close to the expected 9:3:3:1 phenotypic ratio? Do the results support the prediction? What might be observed if far fewer plants were used, given that alleles segregate randomly into gametes? Try to imagine growing that many pea plants, and consider the potential for experimental error. For instance, what would happen if it was extremely windy one day? Think About It 

In the shepherd s-purse plant ( Capsella bursa-pastoris ), seed shape is controlled by two genes, A and B . When both the A and B loci are homozygous recessive ( aabb ), the seeds are ovoid. However, if the dominant allele for either or both of these genes is present, the seeds are triangular. Based on this information, what are the expected phenotypic ratios for a cross between plants that are heterozygous for both traits? 

What is the expected ratio of phenotypes from a dihybrid cross? How do you explain the difference between the expected dihybrid cross ratio and ratio observed in the shepherd s-purse plant? 

This question is an application of Learning Objectives 3.14, 3.15, 3.16, and 3.17 and Science Practices 2.2, 6.5, 6.3, 1.2, and 6.2 because students are applying mathematical routines to analyze data to explain deviations from Mendel s model of inheritance. (Note: The data in this question can be analyzed for statistical difference using Chi-square.) 

Possible answers: The ratios from the shepherd s-purse plant is 15 triangular seeds to 1 ovoid seed. The reason this diverges from the expected 9:3:3:1 ratio is because the genes A and B express the same phenotype. One copy is sufficient for the dominant trait to be expressed. It is an example of dominant epistasis. Epistasis 

Mendel s studies in pea plants implied that the sum of an individual s phenotype was controlled by genes (or as he called them, unit factors), such that every characteristic was distinctly and completely controlled by a single gene. In fact, single observable characteristics are almost always under the influence of multiple genes (each with two or more alleles) acting in unison. For example, at least eight genes contribute to eye color in humans. 

Eye color in humans is determined by multiple genes. Use the Eye Color Calculator to predict the eye color of children from parental eye color. 

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In some cases, several genes can contribute to aspects of a common phenotype without their gene products ever directly interacting. In the case of organ development, for instance, genes may be expressed sequentially, with each gene adding to the complexity and specificity of the organ. Genes may function in complementary or synergistic fashions, such that two or more genes need to be expressed simultaneously to affect a phenotype. Genes may also oppose each other, with one gene modifying the expression of another. 

In epistasis , the interaction between genes is antagonistic, such that one gene masks or interferes with the expression of another. Epistasis is a word composed of Greek roots that mean standing upon. The alleles that are being masked or silenced are said to be hypostatic to the epistatic alleles that are doing the masking. Often the biochemical basis of epistasis is a gene pathway in which the expression of one gene is dependent on the function of a gene that precedes or follows it in the pathway. 

An example of epistasis is pigmentation in mice. The wild-type coat color, agouti ( AA ), is dominant to solid-colored fur ( aa ). However, a separate gene ( C ) is necessary for pigment production. A mouse with a recessive c allele at this locus is unable to produce pigment and is albino regardless of the allele present at locus A ( [link] ). Therefore, the genotypes AAcc , Aacc , and aacc all produce the same albino phenotype. A cross between heterozygotes for both genes ( AaCc x AaCc ) would generate offspring with a phenotypic ratio of 9 agouti:3 solid color:4 albino ( [link] ). In this case, the C gene is epistatic to the A gene. In mice, the mottled agouti coat color ( A ) is dominant to a solid coloration, such as black or gray. A gene at a separate locus ( C ) is responsible for pigment production. The recessive c allele does not produce pigment, and a mouse with the homozygous recessive cc genotype is albino regardless of the allele present at the A locus. Thus, the C gene is epistatic to the A gene. 

Epistasis can also occur when a dominant allele masks expression at a separate gene. Fruit color in summer squash is expressed in this way. Homozygous recessive expression of the W gene ( ww ) coupled with homozygous dominant or heterozygous expression of the Y gene ( YY or Yy ) generates yellow fruit, and the wwyy genotype produces green fruit. However, if a dominant copy of the W gene is present in the homozygous or heterozygous form, the summer squash will produce white fruit regardless of the Y alleles. A cross between white heterozygotes for both genes ( WwYy WwYy ) would produce offspring with a phenotypic ratio of 12 white:3 yellow:1 green. 

Finally, epistasis can be reciprocal such that either gene, when present in the dominant (or recessive) form, expresses the same phenotype. In the shepherd s purse plant ( Capsella bursa-pastoris ), the characteristic of seed shape is controlled by two genes in a dominant epistatic relationship. When the genes A and B are both homozygous recessive ( aabb ), the seeds are ovoid. If the dominant allele for either of these genes is present, the result is triangular seeds. That is, every possible genotype other than aabb results in triangular seeds, and a cross between heterozygotes for both genes ( AaBb x AaBb ) would yield offspring with a phenotypic ratio of 15 triangular:1 ovoid. 

As you work through genetics problems, keep in mind that any single characteristic that results in a phenotypic ratio that totals 16 is typical of a two-gene interaction. Recall the phenotypic inheritance pattern for Mendel s dihybrid cross, which considered two non-interacting genes 9:3:3:1. Similarly, we would expect interacting gene pairs to also exhibit ratios expressed as 16 parts. Note that we are assuming the interacting genes are not linked; they are still assorting independently into gametes. 

For an excellent review of Mendel s experiments and to perform your own crosses and identify patterns of inheritance, visit the Mendel s Peas web lab. 

[link] Section Summary 

Mendel postulated that genes (characteristics) are inherited as pairs of alleles (traits) that behave in a dominant and recessive pattern. Alleles segregate into gametes such that each gamete is equally likely to receive either one of the two alleles present in a diploid individual. In addition, genes are assorted into gametes independently of one another. That is, alleles are generally not more likely to segregate into a gamete with a particular allele of another gene. A dihybrid cross demonstrates independent assortment when the genes in question are on different chromosomes or distant from each other on the same chromosome. For crosses involving more than two genes, use the forked line or probability methods to predict offspring genotypes and phenotypes rather than a Punnett square. 

Although chromosomes sort independently into gametes during meiosis, Mendel s law of independent assortment refers to genes, not chromosomes, and a single chromosome may carry more than 1,000 genes. When genes are located in close proximity on the same chromosome, their alleles tend to be inherited together. This results in offspring ratios that violate Mendel's law of independent assortment. However, recombination serves to exchange genetic material on homologous chromosomes such that maternal and paternal alleles may be recombined on the same chromosome. This is why alleles on a given chromosome are not always inherited together. Recombination is a random event occurring anywhere on a chromosome. Therefore, genes that are far apart on the same chromosome are likely to still assort independently because of recombination events that occurred in the intervening chromosomal space. 

Whether or not they are sorting independently, genes may interact at the level of gene products such that the expression of an allele for one gene masks or modifies the expression of an allele for a different gene. This is called epistasis. Review Questions 

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[link] Glossary dihybrid result of a cross between two true-breeding parents that express different traits for two characteristics epistasis antagonistic interaction between genes such that one gene masks or interferes with the expression of another law of dominance in a heterozygote, one trait will conceal the presence of another trait for the same characteristic law of independent assortment genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur law of segregation paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors linkage phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited togetherIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Chromosomes are threadlike nuclear structures consisting of DNA and proteins that serve as the repositories for genetic information. The chromosomes depicted here were isolated from a fruit fly s salivary gland, stained with dye, and visualized under a microscope. Akin to miniature bar codes, chromosomes absorb different dyes to produce characteristic banding patterns, which allows for their routine identification. (credit: modification of work by LPLT /Wikimedia Commons; scale-bar data from Matt Russell) 

According to the United Nations Office on Drugs and Crime, approximately 95% of those who commit homicide are men. While behavior is shaped by the environment one grows up and lives in, genetics also play a role. For example, scientists have discovered genes that appear to increase one s tendency to exhibit aggressive behavior. One of the genes, called MAOA, is located on the X chromosome. In one recent study involving a group of male prisoners in Finland, scientists found that the prisoners who inherited a variant of this gene were between 5% and 10% more likely to have committed a violent crime. Men only have one copy of the gene, since men only have one X chromosome. Women, however, have two copies of the X chromosome and therefore two copies of the gene. Therefore, women who inherit the variant allele will most likely also have a normal allele to counteract its effects. It is important to note that many men inherit the variant copy of MAOA and only some commit violent crimes. The environment seems to play a much more critical role. You can read more about nature/nurture roles in crime in this article . 

Before students begin this chapter, it is useful to review these concepts: DNA and chromosome structure; relationships among DNA, genes, and chromosomes; overview of the steps of mitosis and meiosis; overview of independent assortment; ploidy (haploid versus diploid).Chromosomal Theory and Genetic Linkage Chromosomal Theory and Genetic Linkage 

In this section, you will explore the following question: What is the relationship among genetic linkage, crossing over, and genetic variation? Connection for AP Courses 

Proposed independently by Sutton and Boveri in the early 1900s, the Chromosomal Theory of Inheritance states that chromosomes are vehicles of genetic heredity. As we have discovered, patterns of inheritance are more complex than Mendel could have imagined. Mendel was investigating the behavior of genes. He was fortunate in choosing traits coded by genes that happened to be on different chromosomes or far apart on the same chromosome. When genes are linked or near each other on the same chromosome, patterns of segregation and independent assortment change. In 1913, Sturtevant devised a method to assess recombination frequency and infer the relative positions and distances of linked genes on a chromosome based on the average number of crossovers between them during meiosis. 

The content presented in this section supports the Learning Objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The AP Learning Objectives merge essential knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 3.10 The student is able to represent the connection between meiosis and increased genetic diversity necessary for evolution. Essential Knowledge 3.A.3 The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.12 The student is able to construct a representation that connects the process of meiosis to the passage of traits from parent to offspring. 

Introduce genetic linkage using visuals such as this video . 

Students can read about corn genetics in this review article . 

Students can read about linked genes and Mendel s work in this article . 

Have students work through inheritance scenarios where genes are linked and where they are on different chromosomes using the following activity sheet . 

Teacher preparation notes for this activity are available here . 

Long before chromosomes were visualized under a microscope, the father of modern genetics, Gregor Mendel, began studying heredity in 1843. With the improvement of microscopic techniques during the late 1800s, cell biologists could stain and visualize subcellular structures with dyes and observe their actions during cell division and meiosis. With each mitotic division, chromosomes replicated, condensed from an amorphous (no constant shape) nuclear mass into distinct X-shaped bodies (pairs of identical sister chromatids), and migrated to separate cellular poles. Chromosomal Theory of Inheritance 

The speculation that chromosomes might be the key to understanding heredity led several scientists to examine Mendel s publications and re-evaluate his model in terms of the behavior of chromosomes during mitosis and meiosis. In 1902, Theodor Boveri observed that proper embryonic development of sea urchins does not occur unless chromosomes are present. That same year, Walter Sutton observed the separation of chromosomes into daughter cells during meiosis ( [link] ). Together, these observations led to the development of the Chromosomal Theory of Inheritance , which identified chromosomes as the genetic material responsible for Mendelian inheritance. (a) Walter Sutton and (b) Theodor Boveri are credited with developing the Chromosomal Theory of Inheritance, which states that chromosomes carry the unit of heredity (genes). 

The Chromosomal Theory of Inheritance was consistent with Mendel s laws and was supported by the following observations: During meiosis, homologous chromosome pairs migrate as discrete structures that are independent of other chromosome pairs. The sorting of chromosomes from each homologous pair into pre-gametes appears to be random. Each parent synthesizes gametes that contain only half of their chromosomal complement. Even though male and female gametes (sperm and egg) differ in size and morphology, they have the same number of chromosomes, suggesting equal genetic contributions from each parent. The gametic chromosomes combine during fertilization to produce offspring with the same chromosome number as their parents. 

Despite compelling correlations between the behavior of chromosomes during meiosis and Mendel s abstract laws, the Chromosomal Theory of Inheritance was proposed long before there was any direct evidence that traits were carried on chromosomes. Critics pointed out that individuals had far more independently segregating traits than they had chromosomes. It was only after several years of carrying out crosses with the fruit fly, Drosophila melanogaster , that Thomas Hunt Morgan provided experimental evidence to support the Chromosomal Theory of Inheritance. Genetic Linkage and Distances 

Mendel s work suggested that traits are inherited independently of each other. Morgan identified a 1:1 correspondence between a segregating trait and the X chromosome, suggesting that the random segregation of chromosomes was the physical basis of Mendel s model. This also demonstrated that linked genes disrupt Mendel s predicted outcomes. The fact that each chromosome can carry many linked genes explains how individuals can have many more traits than they have chromosomes. However, observations by researchers in Morgan s laboratory suggested that alleles positioned on the same chromosome were not always inherited together. During meiosis, linked genes somehow became unlinked. Homologous Recombination 

In 1909, Frans Janssen observed chiasmata the point at which chromatids are in contact with each other and may exchange segments prior to the first division of meiosis. He suggested that alleles become unlinked and chromosomes physically exchange segments. As chromosomes condensed and paired with their homologs, they appeared to interact at distinct points. Janssen suggested that these points corresponded to regions in which chromosome segments were exchanged. It is now known that the pairing and interaction between homologous chromosomes, known as synapsis, does more than simply organize the homologs for migration to separate daughter cells. When synapsed, homologous chromosomes undergo reciprocal physical exchanges at their arms in a process called homologous recombination , or more simply, crossing over. 

To better understand the type of experimental results that researchers were obtaining at this time, consider a heterozygous individual that inherited dominant maternal alleles for two genes on the same chromosome (such as AB ) and two recessive paternal alleles for those same genes (such as ab ). If the genes are linked, one would expect this individual to produce gametes that are either AB or ab with a 1:1 ratio. If the genes are unlinked, the individual should produce AB , Ab , aB , and ab gametes with equal frequencies, according to the Mendelian concept of independent assortment. Because they correspond to new allele combinations, the genotypes Ab and aB are nonparental types that result from homologous recombination during meiosis. Parental types are progeny that exhibit the same allelic combination as their parents. Morgan and his colleagues, however, found that when such heterozygous individuals were test crossed to a homozygous recessive parent ( AaBb aabb ), both parental and nonparental cases occurred. For example, 950 offspring might be recovered that were either AaBb or aabb , but 50 offspring would also be obtained that were either Aabb or aaBb . These results suggested that linkage occurred most often, but a significant minority of offspring were the products of recombination. 

Inheritance patterns of unlinked and linked genes are shown. In (a), two genes are located on different chromosomes so independent assortment occurs during meiosis. The offspring have an equal chance of being the parental type (inheriting the same combination of traits as the parents) or a nonparental type (inheriting a different combination of traits than the parents). In (b), two genes are very close together on the same chromosome so that no crossing over occurs between them. The genes are therefore always inherited together and all of the offspring are the parental type. In (c), two genes are far apart on the chromosome such that crossing over occurs during every meiotic event. The recombination frequency will be the same as if the genes were on separate chromosomes. (d) The actual recombination frequency of fruit fly wing length and body color that Thomas Morgan observed in 1912 was 17 percent. A crossover frequency between 0 percent and 50 percent indicates that the genes are on the same chromosome and crossover occurs some of the time. 

[link] Think About It 

A test cross involving F 1 dihybrid flies produces more parental-type offspring than recombinant-type offspring. How can you explain these observed results? 

The question is an application of Learning Objective 3.12 and Science Practices 1.1 and 7.2, and Learning Objective 3.10 and Science Practice 7.1 because students are explaining how meiosis can result in gametes with genetic variation; in turn, these gametes can introduce variation in offspring. Answer 

More parental type offspring are produced because the genes that are being examined in the dihybrid cross are linked. Genes whose loci are nearer to each other are less likely to be separated onto different chromatids during meiosis as a result of chromosomal crossover. Therefore, there will be more offspring with the parental phenotype than the recombinant phenotype. 

More information about linked genes can be found at the following resources: 

Linked genes: Youtube video 

Chromosomal inheritance: Youtube video 

Genetic Markers for Cancers 

Scientists have used genetic linkage to discover the location in the human genome of many genes that cause disease. They locate disease genes by tracking inheritance of traits through generations of families and creating linkage maps that measure recombination among groups of genetic markers. The two BRCA genes, mutations which can lead to breast and ovarian cancers, were some of the first genes discovered by genetic mapping. Women who have family histories of these cancers can now be screened to determine if one or both of these genes carry a mutation. If so, they can opt to have their breasts and ovaries surgically removed. This decreases their chances of getting cancer later in life. The actress Angelia Jolie brought this to the public s attention when she opted for surgery in 2014 and again in 2015 after doctors found she carried a mutated BRCA1 gene. 

[link] Genetic Maps 

Janssen did not have the technology to demonstrate crossing over so it remained an abstract idea that was not widely accepted. Scientists thought chiasmata were a variation on synapsis and could not understand how chromosomes could break and rejoin. Yet, the data were clear that linkage did not always occur. Ultimately, it took a young undergraduate student and an all-nighter to mathematically elucidate the problem of linkage and recombination. 

In 1913, Alfred Sturtevant, a student in Morgan s laboratory, gathered results from researchers in the laboratory, and took them home one night to mull them over. By the next morning, he had created the first chromosome map, a linear representation of gene order and relative distance on a chromosome ( [link] ). 

This genetic map orders Drosophila genes on the basis of recombination frequency. 

[link] 

As shown in [link] , by using recombination frequency to predict genetic distance, the relative order of genes on chromosome 2 could be inferred. The values shown represent map distances in centimorgans (cM), which correspond to recombination frequencies (in percent). Therefore, the genes for body color and wing size were 65.5 48.5 = 17 cM apart, indicating that the maternal and paternal alleles for these genes recombine in 17 percent of offspring, on average. 

To construct a chromosome map, Sturtevant assumed that genes were ordered serially on threadlike chromosomes. He also assumed that the incidence of recombination between two homologous chromosomes could occur with equal likelihood anywhere along the length of the chromosome. Operating under these assumptions, Sturtevant postulated that alleles that were far apart on a chromosome were more likely to dissociate during meiosis simply because there was a larger region over which recombination could occur. Conversely, alleles that were close to each other on the chromosome were likely to be inherited together. The average number of crossovers between two alleles that is, their recombination frequency correlated with their genetic distance from each other, relative to the locations of other genes on that chromosome. Considering the example cross between AaBb and aabb above, the frequency of recombination could be calculated as 50/1000 = 0.05. That is, the likelihood of a crossover between genes A/a and B/b was 0.05, or 5 percent. Such a result would indicate that the genes were definitively linked, but that they were far enough apart for crossovers to occasionally occur. Sturtevant divided his genetic map into map units, or centimorgans (cM) , in which a recombination frequency of 0.01 corresponds to 1 cM. 

By representing alleles in a linear map, Sturtevant suggested that genes can range from being perfectly linked (recombination frequency = 0) to being perfectly unlinked (recombination frequency = 0.5) when genes are on different chromosomes or genes are separated very far apart on the same chromosome. Perfectly unlinked genes correspond to the frequencies predicted by Mendel to assort independently in a dihybrid cross. A recombination frequency of 0.5 indicates that 50 percent of offspring are recombinants and the other 50 percent are parental types. That is, every type of allele combination is represented with equal frequency. This representation allowed Sturtevant to additively calculate distances between several genes on the same chromosome. However, as the genetic distances approached 0.50, his predictions became less accurate because it was not clear whether the genes were very far apart on the same chromosome or on different chromosomes. 

In 1931, Barbara McClintock and Harriet Creighton demonstrated the crossover of homologous chromosomes in corn plants. Weeks later, homologous recombination in Drosophila was demonstrated microscopically by Curt Stern. Stern observed several X-linked phenotypes that were associated with a structurally unusual and dissimilar X chromosome pair in which one X was missing a small terminal segment, and the other X was fused to a piece of the Y chromosome. By crossing flies, observing their offspring, and then visualizing the offspring s chromosomes, Stern demonstrated that every time the offspring allele combination deviated from either of the parental combinations, there was a corresponding exchange of an X chromosome segment. Using mutant flies with structurally distinct X chromosomes was the key to observing the products of recombination because DNA sequencing and other molecular tools were not yet available. It is now known that homologous chromosomes regularly exchange segments in meiosis by reciprocally breaking and rejoining their DNA at precise locations. 

Review Sturtevant s process to create a genetic map on the basis of recombination frequencies here . 

[link] Mendel s Mapped Traits 

Homologous recombination is a common genetic process, yet Mendel never observed it. Had he investigated both linked and unlinked genes, it would have been much more difficult for him to create a unified model of his data on the basis of probabilistic calculations. Researchers who have since mapped the seven traits investigated by Mendel onto the seven chromosomes of the pea plant genome have confirmed that all of the genes he examined are either on separate chromosomes or are sufficiently far apart as to be statistically unlinked. Some have suggested that Mendel was enormously lucky to select only unlinked genes, whereas others question whether Mendel discarded any data suggesting linkage. In any case, Mendel consistently observed independent assortment because he examined genes that were effectively unlinked. Section Summary 

The Chromosomal Theory of inheritance, proposed by Sutton and Boveri, states that chromosomes are the vehicles of genetic heredity. Neither Mendelian genetics nor gene linkage is perfectly accurate; instead, chromosome behavior involves segregation, independent assortment, and occasionally, linkage. Sturtevant devised a method to assess recombination frequency and infer the relative positions and distances of linked genes on a chromosome on the basis of the average number of crossovers in the intervening region between the genes. Sturtevant correctly presumed that genes are arranged in serial order on chromosomes and that recombination between homologs can occur anywhere on a chromosome with equal likelihood. Whereas linkage causes alleles on the same chromosome to be inherited together, homologous recombination biases alleles toward an inheritance pattern of independent assortment. Review Questions 

[link] 

[link] Critical Thinking Questions 

[link] Test Prep for AP Courses 

[link] 

[link] Glossary centimorgan (cM) (also, map unit) relative distance that corresponds to a recombination frequency of 0.01 Chromosomal Theory of Inheritance theory proposing that chromosomes are the vehicles of genes and that their behavior during meiosis is the physical basis of the inheritance patterns that Mendel observed homologous recombination process by which homologous chromosomes undergo reciprocal physical exchanges at their arms, also known as crossing over nonparental (recombinant) type progeny resulting from homologous recombination that exhibits a different allele combination compared with its parents parental types progeny that exhibits the same allelic combination as its parents recombination frequency average number of crossovers between two alleles; observed as the number of nonparental types in a population of progenyChromosomal Basis of Inherited Disorders Chromosomal Basis of Inherited Disorders 

In this section, you will explore the following question: What are the genetic consequences that result from nondisjunction and errors in chromosome structure through inversions and translocations? Connection for AP Courses 

The number, size, shape, and banding patterns of chromosomes make them easily identifiable in a karyogram and allows for the assessment of many chromosomal abnormalities. Although the cell cycle, mitosis, and meiosis are highly regulated to prevent errors, the processes are not perfect. One example is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis I or meiosis II (a phenomenon referred to as nondisjunction). This results in gametes with too many or too few chromosomes. Disorders in chromosome number (aneuploidy) are typically lethal to the embryo, although a few trisomic genotypes are viable (e.g., Down syndrome). Because of X inactivation, aberrations in sex chromosomes typically have milder phenotypic effects (e.g., Turner syndrome) than aneuploidy. Sometimes segments of chromosome are duplicated, deleted, or rearranged by inversion or translocation. These aberrations can result in problematic phenotypic effects. Diagnostic testing can detect many of these chromosomal disorders in individuals well before birth, resulting in medical, ethical, and civic issues, such as the right to privacy. 

A condition in which an organism has more than the normal number of chromosome sets (two for diploid species) is called polyploidy. Polyploidy resulting in odd numbers of chromosomes is rare because it results in sterile organisms. One set of chromosomes has no pair so meiosis cannot proceed normally. In contrast, polyploidy resulting in even chromosome numbers is very common in the plant kingdom. Polyploid plants tend to be larger and more robust than individuals with the normal number of chromosomes. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.9 The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization. Essential Knowledge 3.A.3 The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. Science Practice 3.1 The student can pose scientific questions. Learning Objective 3.13 The student is able to pose questions about ethical, social or medical issues surrounding human genetic disorders. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.A.3 Changes in genotype can result in changes in phenotype. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. 

Introduce karyotyping using this activity, which has students create a karyotype by matching chromosomes, this activity or this activity . 

Background information on karyotyping is available at this site . 

Some students have difficulties connecting the idea of chromosome structure with inheritance, as discussed in this paper . 

Students may therefore have trouble understanding the role of chromosomal abnormalities in inherited disorders. It may help students to review meiosis, using videos such as this . 

Inherited disorders can arise when chromosomes behave abnormally during meiosis. Chromosome disorders can be divided into two categories: abnormalities in chromosome number and chromosomal structural rearrangements. Because even small segments of chromosomes can span many genes, chromosomal disorders are characteristically dramatic and often fatal. Identification of Chromosomes 

The isolation and microscopic observation of chromosomes forms the basis of cytogenetics and is the primary method by which clinicians detect chromosomal abnormalities in humans. A karyotype is the number and appearance of chromosomes, and includes their length, banding pattern, and centromere position. To obtain a view of an individual s karyotype, cytologists photograph the chromosomes and then cut and paste each chromosome into a chart, or karyogram , also known as an ideogram ( [link] ). This karyotype is of a female human. Notice that homologous chromosomes are the same size, and have the same centromere positions and banding patterns. A human male would have an XY chromosome pair instead of the XX pair shown. (credit: Andreas Blozer et al) 

In a given species, chromosomes can be identified by their number, size, centromere position, and banding pattern. In a human karyotype, autosomes or body chromosomes (all of the non sex chromosomes) are generally organized in order of size from largest (chromosome 1) to smallest (chromosome 22). (The X and Y chromosomes, the 23 rd pair, are not autosomes.) However, chromosome 21 is actually shorter than chromosome 22. This was discovered after the naming of Down syndrome as trisomy 21, reflecting how this disease results from possessing one extra chromosome 21 (three total). Not wanting to change the name of this disease, scientists retained the original numbering system. The chromosome arms projecting from either end of the centromere may be designated as short or long, depending on their relative lengths. The short arm is abbreviated p (for petite ), whereas the long arm is abbreviated q (because it follows p alphabetically). Each arm is further subdivided and denoted by a number. For example, locus 3 on the short arm of chromosome 21 is denoted 21p3. Using this naming system, locations on chromosomes can be described consistently in the scientific literature. 

Geneticists Use Karyograms to Identify Chromosomal Aberrations Although Mendel is referred to as the father of modern genetics, he performed his experiments with none of the tools that the geneticists of today routinely employ. One such powerful cytological technique is karyotyping, a method in which traits characterized by chromosomal abnormalities can be identified from a single cell. To observe an individual s karyotype, a person s cells (like white blood cells) are first collected from a blood sample or other tissue. In the laboratory, the isolated cells are stimulated to begin actively dividing. A chemical called colchicine is then applied to cells to arrest condensed chromosomes in metaphase. Cells are then made to swell using a hypotonic solution so the chromosomes spread apart. Finally, the sample is preserved in a fixative and applied to a slide. 

The geneticist then stains chromosomes with one of several dyes to better visualize the distinct and reproducible banding patterns of each chromosome pair. Following staining, the chromosomes are viewed using bright-field microscopy. A common stain choice is the Giemsa stain. Giemsa staining results in approximately 400 800 bands (of tightly coiled DNA and condensed proteins) arranged along all of the 23 chromosome pairs; an experienced geneticist can identify each band. In addition to the banding patterns, chromosomes are further identified on the basis of size and centromere location. To obtain the classic depiction of the karyotype in which homologous pairs of chromosomes are aligned in numerical order from longest to shortest, the geneticist obtains a digital image, identifies each chromosome, and manually arranges the chromosomes into this pattern ( [link] ). 

At its most basic, the karyogram may reveal genetic abnormalities in which an individual has too many or too few chromosomes per cell. Examples of this are Down Syndrome, which is identified by a third copy of chromosome 21, and Turner Syndrome, which is characterized by the presence of only one X chromosome in women instead of the normal two. Geneticists can also identify large deletions or insertions of DNA. For instance, Jacobsen Syndrome which involves distinctive facial features as well as heart and bleeding defects is identified by a deletion on chromosome 11. Finally, the karyotype can pinpoint translocations , which occur when a segment of genetic material breaks from one chromosome and reattaches to another chromosome or to a different part of the same chromosome. Translocations are implicated in certain cancers, including chronic myelogenous leukemia. 

During Mendel s lifetime, inheritance was an abstract concept that could only be inferred by performing crosses and observing the traits expressed by offspring. By observing a karyogram, today s geneticists can actually visualize the chromosomal composition of an individual to confirm or predict genetic abnormalities in offspring, even before birth. Disorders in Chromosome Number 

Of all of the chromosomal disorders, abnormalities in chromosome number are the most obviously identifiable from a karyogram. Disorders of chromosome number include the duplication or loss of entire chromosomes, as well as changes in the number of complete sets of chromosomes. They are caused by nondisjunction , which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. Misaligned or incomplete synapsis, or a dysfunction of the spindle apparatus that facilitates chromosome migration, can cause nondisjunction. The risk of nondisjunction occurring increases with the age of the parents. 

Nondisjunction can occur during either meiosis I or II, with differing results ( [link] ). If homologous chromosomes fail to separate during meiosis I, the result is two gametes that lack that particular chromosome and two gametes with two copies of the chromosome. If sister chromatids fail to separate during meiosis II, the result is one gamete that lacks that chromosome, two normal gametes with one copy of the chromosome, and one gamete with two copies of the chromosome. 

Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number. Nondisjunction may occur during meiosis I or meiosis II. 

[link] Aneuploidy 

An individual with the appropriate number of chromosomes for their species is called euploid ; in humans, euploidy corresponds to 22 pairs of autosomes and one pair of sex chromosomes. An individual with an error in chromosome number is described as aneuploid , a term that includes monosomy (loss of one chromosome) or trisomy (gain of an extraneous chromosome). Monosomic human zygotes missing any one copy of an autosome invariably fail to develop to birth because they lack essential genes. This underscores the importance of gene dosage in humans. Most autosomal trisomies also fail to develop to birth; however, duplications of some of the smaller chromosomes (13, 15, 18, 21, or 22) can result in offspring that survive for several weeks to many years. Trisomic individuals suffer from a different type of genetic imbalance: an excess in gene dose. Individuals with an extra chromosome may synthesize an abundance of the gene products encoded by that chromosome. This extra dose (150 percent) of specific genes can lead to a number of functional challenges and often precludes development. The most common trisomy among viable births is that of chromosome 21, which corresponds to Down Syndrome. Individuals with this inherited disorder are characterized by short stature and stunted digits, facial distinctions that include a broad skull and large tongue, and significant developmental delays. The incidence of Down syndrome is correlated with maternal age; older women are more likely to become pregnant with fetuses carrying the trisomy 21 genotype ( [link] ). The incidence of having a fetus with trisomy 21 increases dramatically with maternal age. 

Visualize the addition of a chromosome that leads to Down syndrome in this video simulation . 

[link] Polyploidy 

An individual with more than the correct number of chromosome sets (two for diploid species) is called polyploid . For instance, fertilization of an abnormal diploid egg with a normal haploid sperm would yield a triploid zygote. Polyploid animals are extremely rare, with only a few examples among the flatworms, crustaceans, amphibians, fish, and lizards. Polyploid animals are sterile because meiosis cannot proceed normally and instead produces mostly aneuploid daughter cells that cannot yield viable zygotes. Rarely, polyploid animals can reproduce asexually by haplodiploidy, in which an unfertilized egg divides mitotically to produce offspring. In contrast, polyploidy is very common in the plant kingdom, and polyploid plants tend to be larger and more robust than euploids of their species ( [link] ). As with many polyploid plants, this triploid orange daylily ( Hemerocallis fulva ) is particularly large and robust, and grows flowers with triple the number of petals of its diploid counterparts. (credit: Steve Karg) Sex Chromosome Nondisjunction in Humans 

Humans display dramatic deleterious effects with autosomal trisomies and monosomies. Therefore, it may seem counterintuitive that human females and males can function normally, despite carrying different numbers of the X chromosome. Rather than a gain or loss of autosomes, variations in the number of sex chromosomes are associated with relatively mild effects. In part, this occurs because of a molecular process called X inactivation . Early in development, when female mammalian embryos consist of just a few thousand cells (relative to trillions in the newborn), one X chromosome in each cell inactivates by tightly condensing into a quiescent (dormant) structure called a Barr body. The chance that an X chromosome (maternally or paternally derived) is inactivated in each cell is random, but once the inactivation occurs, all cells derived from that one will have the same inactive X chromosome or Barr body. By this process, females compensate for their double genetic dose of X chromosome. In so-called tortoiseshell cats, embryonic X inactivation is observed as color variegation ( [link] ). Females that are heterozygous for an X-linked coat color gene will express one of two different coat colors over different regions of their body, corresponding to whichever X chromosome is inactivated in the embryonic cell progenitor of that region. In cats, the gene for coat color is located on the X chromosome. In the embryonic development of female cats, one of the two X chromosomes is randomly inactivated in each cell, resulting in a tortoiseshell pattern if the cat has two different alleles for coat color. Male cats, having only one X chromosome, never exhibit a tortoiseshell coat color. (credit: Michael Bodega) 

An individual carrying an abnormal number of X chromosomes will inactivate all but one X chromosome in each of her cells. However, even inactivated X chromosomes continue to express a few genes, and X chromosomes must reactivate for the proper maturation of female ovaries. As a result, X-chromosomal abnormalities are typically associated with mild mental and physical defects, as well as sterility. If the X chromosome is absent altogether, the individual will not develop in utero. 

Several errors in sex chromosome number have been characterized. Individuals with three X chromosomes, called triplo-X, are phenotypically female but express developmental delays and reduced fertility. The XXY genotype, corresponding to one type of Klinefelter syndrome, corresponds to phenotypically male individuals with small testes, enlarged breasts, and reduced body hair. More complex types of Klinefelter syndrome exist in which the individual has as many as five X chromosomes. In all types, every X chromosome except one undergoes inactivation to compensate for the excess genetic dosage. This can be seen as several Barr bodies in each cell nucleus. Turner syndrome, characterized as an X0 genotype (i.e., only a single sex chromosome), corresponds to a phenotypically female individual with short stature, webbed skin in the neck region, hearing and cardiac impairments, and sterility. Duplications and Deletions 

In addition to the loss or gain of an entire chromosome, a chromosomal segment may be duplicated or lost. Duplications and deletions often produce offspring that survive but exhibit physical and mental abnormalities. Duplicated chromosomal segments may fuse to existing chromosomes or may be free in the nucleus. Cri-du-chat (from the French for cry of the cat ) is a syndrome associated with nervous system abnormalities and identifiable physical features that result from a deletion of most of 5p (the small arm of chromosome 5) ( [link] ). Infants with this genotype emit a characteristic high-pitched cry on which the disorder s name is based. This individual with cri-du-chat syndrome is shown at two, four, nine, and 12 years of age. (credit: Paola Cerruti Mainardi) Chromosomal Structural Rearrangements 

Cytologists have characterized numerous structural rearrangements in chromosomes, but chromosome inversions and translocations are the most common. Both are identified during meiosis by the adaptive pairing of rearranged chromosomes with their former homologs to maintain appropriate gene alignment. If the genes carried on two homologs are not oriented correctly, a recombination event could result in the loss of genes from one chromosome and the gain of genes on the other. This would produce aneuploid gametes. Chromosome Inversions 

A chromosome inversion is the detachment, 180 rotation, and reinsertion of part of a chromosome. Inversions may occur in nature as a result of mechanical shear, or from the action of transposable elements (special DNA sequences capable of facilitating the rearrangement of chromosome segments with the help of enzymes that cut and paste DNA sequences). Unless they disrupt a gene sequence, inversions only change the orientation of genes and are likely to have more mild effects than aneuploid errors. However, altered gene orientation can result in functional changes because regulators of gene expression could be moved out of position with respect to their targets, causing aberrant levels of gene products. 

An inversion can be pericentric and include the centromere, or paracentric and occur outside of the centromere ( [link] ). A pericentric inversion that is asymmetric about the centromere can change the relative lengths of the chromosome arms, making these inversions easily identifiable. Pericentric inversions include the centromere, and paracentric inversions do not. A pericentric inversion can change the relative lengths of the chromosome arms; a paracentric inversion cannot. 

When one homologous chromosome undergoes an inversion but the other does not, the individual is described as an inversion heterozygote. To maintain point-for-point synapsis during meiosis, one homolog must form a loop, and the other homolog must mold around it. Although this topology can ensure that the genes are correctly aligned, it also forces the homologs to stretch and can be associated with regions of imprecise synapsis ( [link] ). When one chromosome undergoes an inversion but the other does not, one chromosome must form an inverted loop to retain point-for-point interaction during synapsis. This inversion pairing is essential to maintaining gene alignment during meiosis and to allow for recombination. 

The Chromosome 18 Inversion Not all structural rearrangements of chromosomes produce nonviable, impaired, or infertile individuals. In rare instances, such a change can result in the evolution of a new species. In fact, a pericentric inversion in chromosome 18 appears to have contributed to the evolution of humans. This inversion is not present in our closest genetic relatives, the chimpanzees. Humans and chimpanzees differ cytogenetically by pericentric inversions on several chromosomes and by the fusion of two separate chromosomes in chimpanzees that correspond to chromosome two in humans. 

The pericentric chromosome 18 inversion is believed to have occurred in early humans following their divergence from a common ancestor with chimpanzees approximately five million years ago. Researchers characterizing this inversion have suggested that approximately 19,000 nucleotide bases were duplicated on 18p, and the duplicated region inverted and reinserted on chromosome 18 of an ancestral human. 

A comparison of human and chimpanzee genes in the region of this inversion indicates that two genes ROCK1 and USP14 that are adjacent on chimpanzee chromosome 17 (which corresponds to human chromosome 18) are more distantly positioned on human chromosome 18. This suggests that one of the inversion breakpoints occurred between these two genes. Interestingly, humans and chimpanzees express USP14 at distinct levels in specific cell types, including cortical cells and fibroblasts. Perhaps the chromosome 18 inversion in an ancestral human repositioned specific genes and reset their expression levels in a useful way. Because both ROCK1 and USP14 encode cellular enzymes, a change in their expression could alter cellular function. It is not known how this inversion contributed to hominid evolution, but it appears to be a significant factor in the divergence of humans from other primates. 1 

[link] Translocations 

A translocation occurs when a segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome. Translocations can be benign or have devastating effects depending on how the positions of genes are altered with respect to regulatory sequences. Notably, specific translocations have been associated with several cancers and with schizophrenia. Reciprocal translocations result from the exchange of chromosome segments between two nonhomologous chromosomes such that there is no gain or loss of genetic information ( [link] ). A reciprocal translocation occurs when a segment of DNA is transferred from one chromosome to another, nonhomologous chromosome. (credit: modification of work by National Human Genome Research/USA) Activity 

A Day in the Life . Compose a short story, PowerPoint presentation, video, poem, or significant piece of art to describe a day in the life of a teenager afflicted with a single gene disorder or chromosomal abnormality. You need to include the causes and effects of the disorder and pose a question about a social, medical, or ethical issue(s) associated with human genetic disorders. Think About It 

Create a series of representations to show how nondisjunction can result in a trisomic zygote from a cell with 2n = 4. 

The activity is an application of Learning Objective 3.24 and Science Practices 6.4 and 7.2, and Learning Objective 3.13 and Science Practice 3.1 because students are asked to show how a change in a human genotype, either by a single gene mutation or a chromosomal abnormality, can produce a change in phenotype; then students pose a question about an ethical, social, or medical issue surrounding human genetic disorders in general. 

The Think About It question is an application of Learning Objective 3.9 and Science Practice 6.2 because students are creating a diagram to explain how errors in meiosis can result in an abnormal zygote following fertilization. Answer Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number. Nondisjunction may occur during meiosis I or meiosis II. Section Summary 

The number, size, shape, and banding pattern of chromosomes make them easily identifiable in a karyogram and allows for the assessment of many chromosomal abnormalities. Disorders in chromosome number, or aneuploidies, are typically lethal to the embryo, although a few trisomic genotypes are viable. Because of X inactivation, aberrations in sex chromosomes typically have milder phenotypic effects. Aneuploidies also include instances in which segments of a chromosome are duplicated or deleted. Chromosome structures may also be rearranged, for example by inversion or translocation. Both of these aberrations can result in problematic phenotypic effects. Because they force chromosomes to assume unnatural topologies during meiosis, inversions and translocations are often associated with reduced fertility because of the likelihood of nondisjunction. Review Questions 

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Violaine Goidts et al., Segmental duplication associated with the human-specific inversion of chromosome 18: a further example of the impact of segmental duplications on karyotype and genome evolution in primates, Human Genetics . 115 (2004):116-122 Glossary aneuploid individual with an error in chromosome number; includes deletions and duplications of chromosome segments autosome any of the non-sex chromosomes chromosome inversion detachment, 180 rotation, and reinsertion of a chromosome arm euploid individual with the appropriate number of chromosomes for their species karyogram photographic image of a karyotype karyotype number and appearance of an individuals chromosomes; includes the size, banding patterns, and centromere position monosomy otherwise diploid genotype in which one chromosome is missing nondisjunction failure of synapsed homologs to completely separate and migrate to separate poles during the first cell division of meiosis paracentric inversion that occurs outside of the centromere pericentric inversion that involves the centromere polyploid individual with an incorrect number of chromosome sets translocation process by which one segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome trisomy otherwise diploid genotype in which one entire chromosome is duplicated X inactivation condensation of X chromosomes into Barr bodies during embryonic development in females to compensate for the double genetic doseIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Michael Morton went to jail in 1986 for the murder of this wife. Twenty-five years later, in 2011, he was exonerated of her murder by DNA evidence. (credit: Lauren Gerson) 

Each person s DNA is unique, and it is possible to detect differences among individuals within a species on the basis of these unique features. DNA analysis has many practical applications, including identifying criminals (forensics), determining paternity, tracing genealogy, identifying pathogens, researching archeological finds, tracing disease outbreaks, and studying human migration patterns. In the medical field, DNA is used in diagnostics, new vaccine development, and cancer therapy. It is often possible to determine predisposition to diseases by sequencing genes. 

Sometimes an innocent person is erroneously convicted of a crime and sent to jail. Between 2000 and 2015, evidence from DNA was used to exonerate over 250 innocent people. Twenty of those people were on death row after being convicted of a murder they didn t commit. To learn more about the intense scientific and legal processes used to exonerate those wrongfully convicted, go to The Innocence Project website here . 

Determination of DNA patterns has many uses. In criminal proceedings, DNA analysis has become almost routine and many juries depend on it. However, DNA samples for analysis may not be available in all cases, or DNA might be contaminated. Occasionally, DNA preserved from a crime committed before DNA analysis was available is used as evidence at a retrial.Historical Basis of Modern Understanding Historical Basis of Modern Understanding 

In this section, you will explore the following questions: What is transformation of DNA? How do Griffith s experiments in 1928 relate to our modern understanding of DNA and how it works? What are key historic experiments that helped identify DNA as the genetic material? What are Chargaff s rules of nitrogenous base pairing? Connection for AP Courses 

Today the three letters DNA have become synonymous with crime solving, paternity testing, human identification, and genetic testing. All of these procedures are possible because of the discovery, in the middle of the twentieth century, that DNA is the genetic material. The results of several classic experiments set the stage for an explosion of our knowledge about DNA and how it stores and transmits genetic information. DNA was first isolated from white blood cells by Miescher in the 1860s. Over fifty years later, Griffith s work transforming strains of the bacterium Streptococcus pneumoniae provided the first clue that DNA and not protein (as others argued) is the universal molecule of heredity. Griffith s conclusions were later supported by Avery, MacLeod, and McCarty. 

Subsequent experiments by Hershey and Chase using the bacteriophage T2 proved decisively that DNA is the genetic material. Shortly thereafter, Chargaff determined the ratios of adenine, thymine, cytosine, and guanine in DNA, suggesting paired relationships (A = T and C = G). He also found that the percentages of A, T, C, and G are different for different species. All of these historically important experiments shaped our current understanding of DNA. 

The content presented in this section supports the learning objectives outlined in Big Ideas 3 and 4 of the AP Biology Curriculum Framework. The AP learning objectives merge essential knowledge content with one or more of the seven science practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA to support the claim that DNA is the primary source of heritable information. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 3.2 The student is able to justify the selection of data from historical investigations that support the claim that DNA is the source of heritable information. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.1 The subcomponents of biological molecules and their sequence determine the properties of that molecule. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 4.1 The student is able to explain the connection between the sequence and the subcomponents of a biological polymer and its properties. 

Stress to students that while DNA was discovered in the 1860s, the understanding that DNA is the genetic material came only in the middle of the 20 th century. Prior to that time, most scientists thought that genetic information was transmitted by proteins. There were good reasons for this belief. Scientists had observed that there were many more proteins in cells than there were DNA molecules. They also observed that the chromosomes in eukaryotic cells were packed with large protein complexes. Today scientists call those chromosomal protein complexes histones. Histones play no role in transmitting genetic information. Instead, they help package and order the chromosomes in a cell s nucleus. 

Explain the experiments demonstrating DNA s structure and function and focus on the logic behind the findings. Ask students if they can think of alternative methods to illustrate the same findings based on what they know today. 

Modern understandings of DNA have evolved from the discovery of nucleic acid to the development of the double-helix model. In the 1860s, Friedrich Miescher ( [link] ), a physician by profession, was the first person to isolate phosphate-rich chemicals from white blood cells or leukocytes. He named these chemicals (which would eventually be known as RNA and DNA) nuclein because they were isolated from the nuclei of the cells. Friedrich Miescher (1844 1895) discovered nucleic acids. 

To see Miescher conduct an experiment step-by-step, click through this review of how he discovered the key role of DNA and proteins in the nucleus. 

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A half century later, British bacteriologist Frederick Griffith was perhaps the first person to show that hereditary information could be transferred from one cell to another horizontally, rather than by descent. In 1928, he reported the first demonstration of bacterial transformation , a process in which external DNA is taken up by a cell, thereby changing morphology and physiology. He was working with Streptococcus pneumoniae, the bacterium that causes pneumonia. Griffith worked with two strains, rough (R) and smooth (S). The R strain is non-pathogenic (does not cause disease) and is called rough because its outer surface is a cell wall and lacks a capsule; as a result, the cell surface appears uneven under the microscope. The S strain is pathogenic (disease-causing) and has a capsule outside its cell wall. As a result, it has a smooth appearance under the microscope. Griffith injected the live R strain into mice and they survived. In another experiment, when he injected mice with the heat-killed S strain, they also survived. In a third set of experiments, a mixture of live R strain and heat-killed S strain were injected into mice, and to his surprise the mice died. Upon isolating the live bacteria from the dead mouse, only the S strain of bacteria was recovered. When this isolated S strain was injected into fresh mice, the mice died. Griffith concluded that something had passed from the heat-killed S strain into the live R strain and transformed it into the pathogenic S strain, and he called this the transforming principle ( [link] ). These experiments are now famously known as Griffith's transformation experiments. Two strains of S. pneumoniae were used in Griffith s transformation experiments. The R strain is non-pathogenic. The S strain is pathogenic and causes death. When Griffith injected a mouse with the heat-killed S strain and a live R strain, the mouse died. The S strain was recovered from the dead mouse. Thus, Griffith concluded that something had passed from the heat-killed S strain to the R strain, transforming the R strain into S strain in the process. (credit "living mouse": modification of work by NIH; credit "dead mouse": modification of work by Sarah Marriage) 

Scientists Oswald Avery, Colin MacLeod, and Maclyn McCarty (1944) were interested in exploring this transforming principle further. They isolated the S strain from the dead mice and isolated the proteins and nucleic acids, namely RNA and DNA, as these were possible candidates for the molecule of heredity. They conducted a systematic elimination study. They used enzymes that specifically degraded each component and then used each mixture separately to transform the R strain. They found that when DNA was degraded, the resulting mixture was no longer able to transform the bacteria, whereas all of the other combinations were able to transform the bacteria. This led them to conclude that DNA was the transforming principle. 

Forensic Scientists and DNA Analysis DNA evidence was used for the first time to solve an immigration case. The story started with a teenage boy returning to London from Ghana to be with his mother. Immigration authorities at the airport were suspicious of him, thinking that he was traveling on a forged passport. After much persuasion, he was allowed to go live with his mother, but the immigration authorities did not drop the case against him. All types of evidence, including photographs, were provided to the authorities, but deportation proceedings were started nevertheless. Around the same time, Dr. Alec Jeffreys of Leicester University in the United Kingdom had invented a technique known as DNA fingerprinting. The immigration authorities approached Dr. Jeffreys for help. He took DNA samples from the mother and three of her children, plus an unrelated mother, and compared the samples with the boy s DNA. Because the biological father was not in the picture, DNA from the three children was compared with the boy s DNA. He found a match in the boy s DNA for both the mother and his three siblings. He concluded that the boy was indeed the mother s son. 

Forensic scientists analyze many items, including documents, handwriting, firearms, and biological samples. They analyze the DNA content of hair, semen, saliva, and blood, and compare it with a database of DNA profiles of known criminals. Analysis includes DNA isolation, sequencing, and sequence analysis; most forensic DNA analysis involves polymerase chain reaction (PCR) amplification of short tandem repeat (STR) loci and electrophoresis to determine the length of the PCR-amplified fragment. Only mitochondrial DNA is sequenced for forensics. Forensic scientists are expected to appear at court hearings to present their findings. They are usually employed in crime labs of city and state government agencies. Geneticists experimenting with DNA techniques also work for scientific and research organizations, pharmaceutical industries, and college and university labs. Students wishing to pursue a career as a forensic scientist should have at least a bachelor's degree in chemistry, biology, or physics, and preferably some experience working in a laboratory. Activity DNA Necklace. 

1) Using a molecular modeling kit (or an online virtual kit such as jmol), create a model of each of the 4 nucleotides in DNA, based on structural diagrams found in this chapter or elsewhere online. 

2) Identify where each nucleotide hydrogen-bonds with its complementary base. Add these bonds to secure the two pairs of nucleotides together. How does the hydrogen bonding differ between the two pairs of complementary bases? 

3) Now look at a structural diagram of a complete DNA molecule. Based on the diagram, connect your two pairs of nucleotides together along your DNA s sugar-phosphate backbone (depending on your model kit, you may have to first disconnect the hydrogen bonds between the complementary bases). Which atoms and molecules did you have to remove and add to create the sugar-phosphate backbone? Think About It 

Explain why radioactive sulfur and phosphorus were used to label T2 bacteriophages in the Hershey-Chase experiments. How did the results of these experiments contribute to the identification of DNA as the genetic material? 

The activity is an application of Learning Objective 4.1 and Science Practice 7.1 because students are examining the spatial relationships among the components of a DNA strand and explaining the connections between the sequence and subcomponents of the nucleotides. 

An expanded lab investigation for DNA, involving restriction enzyme analysis, is available from the College Board's AP Biology Investigative Labs: An Inquiry-Based Approach in Investigation 9 . 

1) Group size is dependent on the availability of molecular model kits. Please note that extra carbon and hydrogen bonds are likely needed for students to make all 4 nucleotides. Groups could also be assigned to make one of the two pairs of nucleotides, after which the groups can combine the molecules into DNA in step 3. Jmol is available for download here . 

2) Note: some molecular model kits have special bonds to use for hydrogen bonds. If these bonds are not used, the students may not be able to connect the nucleotides together. Sample answer: One notable difference is that thymine and adenine bond with two hydrogen bonds while cytosine and guanine bond using three hydrogen bonds. 

3) To bond two nucleotides along the sugar-phosphate backbone of DNA, we removed one H from carbon 3 of deoxyribose. We then bonded carbon 3 to one of the single-bonded O atoms on the phosphate ion. Next, we removed the OH group from the CH 2 group on the deoxyribose. The carbon on this CH 2 group was then bonded to the other single-bonded O on the phosphate ion. 

The Think About It question is an application of Learning Objective 3.2 and Science Practice 4.1 because students are asked to justify that the Hershey-Chase experiments supported the identification of DNA as the carrier of genetic information. It is also an application of Learning Objective 3.1 and Science Practice 6.5 because students will evaluate researchers claims that DNA is found in cells and is the primary source of heritable information. Answer: Hershey and Chase used radioactive sulfur because sulfur is not found in DNA but is present in T2 s protein coat. They used radioactive phosphorus because phosphorus is not found in protein but is present in DNA. When they observed the infected bacterial cells they found them to contain radioactive phosphorus but no radioactive sulfur. Therefore, Hershey and Chase knew that the DNA was the infectious agent and, thus, the transmitter of genetic information. 

Experiments conducted by Martha Chase and Alfred Hershey in 1952 provided confirmatory evidence that DNA was the genetic material and not proteins. Chase and Hershey were studying a bacteriophage, which is a virus that infects bacteria. Viruses typically have a simple structure: a protein coat, called the capsid, and a nucleic acid core that contains the genetic material, either DNA or RNA. The bacteriophage infects the host bacterial cell by attaching to its surface, and then it injects its nucleic acids inside the cell. The phage DNA makes multiple copies of itself using the host machinery, and eventually the host cell bursts, releasing a large number of bacteriophages. Hershey and Chase labeled one batch of phage with radioactive sulfur, 35 S, to label the protein coat. Another batch of phage were labeled with radioactive phosphorus, 32 P. Because phosphorous is found in DNA, but not protein, the DNA and not the protein would be tagged with radioactive phosphorus. 

Each batch of phage was allowed to infect the cells separately. After infection, the phage bacterial suspension was put in a blender, which caused the phage coat to be detached from the host cell. The phage and bacterial suspension was spun down in a centrifuge. The heavier bacterial cells settled down and formed a pellet, whereas the lighter phage particles stayed in the supernatant. In the tube that contained phage labeled with 35 S, the supernatant contained the radioactively labeled phage, whereas no radioactivity was detected in the pellet. In the tube that contained the phage labeled with 32 P, the radioactivity was detected in the pellet that contained the heavier bacterial cells, and no radioactivity was detected in the supernatant. Hershey and Chase concluded that it was the phage DNA that was injected into the cell and carried information to produce more phage particles, thus providing evidence that DNA was the genetic material and not proteins ( [link] ). In Hershey and Chase's experiments, bacteria were infected with phage radiolabeled with either 35 S, which labels protein, or 32 P, which labels DNA. Only 32 P entered the bacterial cells, indicating that DNA is the genetic material. 

Around this same time, Austrian biochemist Erwin Chargaff examined the content of DNA in different species and found that the amounts of adenine, thymine, guanine, and cytosine were not found in equal quantities, and that it varied from species to species, but not between individuals of the same species. He found that the amount of adenine equals the amount of thymine, and the amount of cytosine equals the amount of guanine, or A = T and G = C. This is also known as Chargaff s rules. This finding proved immensely useful when Watson and Crick were getting ready to propose their DNA double helix model. Section Summary 

DNA was first isolated from white blood cells by Friedrich Miescher, who called it nuclein because it was isolated from nuclei. Frederick Griffith's experiments with strains of Streptococcus pneumoniae provided the first hint that DNA may be the transforming principle. Avery, MacLeod, and McCarty proved that DNA is required for the transformation of bacteria. Later experiments by Hershey and Chase using bacteriophage T2 proved that DNA is the genetic material. Chargaff found that the ratio of A = T and C = G, and that the percentage content of A, T, G, and C is different for different species. Review Questions 

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[link] Glossary transformation process in which external DNA is taken up by a cellDNA Structure and Sequencing DNA Structure and Sequencing 

In this section, you will explore the following questions: What is the molecular structure of DNA? What is the Sanger method of DNA sequencing? What is an application of DNA sequencing? What are the similarities and differences between eukaryotic and prokaryotic DNA? Connection for AP Courses 

The currently accepted model of the structure of DNA was proposed in 1953 by Watson and Crick, who made their model after seeing a photograph of DNA that Franklin had taken using X-ray crystallography. The photo showed the molecule s double-helix shape and dimensions. The two strands that make up the double helix are complementary and anti-parallel in nature. That is, one strand runs in the 5' to 3' direction, whereas the complementary strand runs in the 3' to 5' direction. (The significance of directionality will be important when we explore how DNA copies itself.) DNA is a polymer of nucleotides that consists of deoxyribose sugar, a phosphate group, and one of four nitrogenous bases A, T, C, and G with a purine always pairing with a pyrimidine (as Chargaff found). The genetic language of DNA is found in sequences of the nucleotides. During cell division each daughter cell receives a copy of DNA in a process called replication. In the years since the discovery of the structure of DNA, many technologies, including DNA sequencing, have been developed that enable us to better understand DNA and its role in our genomes. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA to support the claim that DNA is the primary source of heritable information. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 3.2 The student is able to justify the selection of data from historical investigations that support the claim that DNA is the source of heritable information. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.5 The student can justify the claim that humans can manipulate heritable information by identifying at least two commonly used technologies. 

Franklin s X-ray diffraction pictures helped lead to the discovery of the structure of DNA, but Watson and Crick did not mention Franklin in their seminal 1953 paper, which can be found here . This paper includes annotations that help place the work in historical context. Students might be interested to learn how Watson and Crick discovered the structure of DNA. Details can be found at this PBS website . If possible, find a copy of the announcement of the discovery as it appeared in The New York Times . The wording is interesting and the significance of the discovery is understated. 

The building blocks of DNA are nucleotides. The important components of the nucleotide are a nitrogenous base, deoxyribose (5-carbon sugar), and a phosphate group ( [link] ). The nucleotide is named depending on the nitrogenous base. The nitrogenous base can be a purine such as adenine (A) and guanine (G), or a pyrimidine such as cytosine (C) and thymine (T). Each nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base. The sugar is deoxyribose in DNA and ribose in RNA. 

The nucleotides combine with each other by covalent bonds known as phosphodiester bonds or linkages. The purines have a double ring structure with a six-membered ring fused to a five-membered ring. Pyrimidines are smaller in size; they have a single six-membered ring structure. The carbon atoms of the five-carbon sugar are numbered 1', 2', 3', 4', and 5' (1' is read as one prime ). The phosphate residue is attached to the hydroxyl group of the 5' carbon of one sugar of one nucleotide and the hydroxyl group of the 3' carbon of the sugar of the next nucleotide, thereby forming a 5'-3' phosphodiester bond. 

In the 1950s, Francis Crick and James Watson worked together to determine the structure of DNA at the University of Cambridge, England. Other scientists like Linus Pauling and Maurice Wilkins were also actively exploring this field. Pauling had discovered the secondary structure of proteins using X-ray crystallography. In Wilkins lab, researcher Rosalind Franklin was using X-ray diffraction methods to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule on the basis of Franklin's data because Crick had also studied X-ray diffraction ( [link] ). In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine. Unfortunately, by then Franklin had died, and Nobel prizes are not awarded posthumously. The work of pioneering scientists (a) James Watson, Francis Crick, and Maclyn McCarty led to our present day understanding of DNA. Scientist Rosalind Franklin discovered (b) the X-ray diffraction pattern of DNA, which helped to elucidate its double helix structure. (credit a: modification of work by Marjorie McCarty, Public Library of Science) 

Watson and Crick proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. Base pairing takes place between a purine and pyrimidine; namely, A pairs with T and G pairs with C. Adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs. The base pairs are stabilized by hydrogen bonds; adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two strands are anti-parallel in nature; that is, the 3' end of one strand faces the 5' end of the other strand. The sugar and phosphate of the nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside. Each base pair is separated from the other base pair by a distance of 0.34 nm, and each turn of the helix measures 3.4 nm. Therefore, ten base pairs are present per turn of the helix. The diameter of the DNA double helix is 2 nm, and it is uniform throughout. Only the pairing between a purine and pyrimidine can explain the uniform diameter. The twisting of the two strands around each other results in the formation of uniformly spaced major and minor grooves ( [link] ). DNA has (a) a double helix structure and (b) phosphodiester bonds. The (c) major and minor grooves are binding sites for DNA binding proteins during processes such as transcription (the copying of RNA from DNA) and replication. Activity 

Read Watson and Crick s original Nature article, Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid, How did Watson and Crick s model build on the findings of Rosalind Franklin? How did their model of DNA build on the findings of Hershey and Chase, and others, showing that DNA can encode and pass information on to the next generation? Think About It 

Watson and Crick s work determined the structure of DNA. However, it was still relatively unknown how DNA encoded information into genes. Select one modern form of biotechnology and research its basic methods online. Examples include gene sequencing, DNA fingerprinting, PCR (polymerase chain reaction), genetically-modified food, etc. Briefly describe your chosen technology, and what benefits it provides us. Then describe how Watson and Crick s findings were vital to the development of your chosen technology. 

The activity is an application of Learning Objective 3.1 and Science Practice 6.5 because students are analyzing Watson and Crick s model of DNA relative to the findings of other DNA researchers who determined that DNA is the molecule of heredity. The activity is also an application of Learning Objective 3.2 and Science Practice 4.1 because students are analyzing the historic published results of Watson and Crick and selecting evidence that Watson and Crick used to create their model of DNA and further show that DNA is the molecule of heredity. Possible answer: Watson and Crick s model built on Franklin s findings that DNA has the structure of a double helix. The finding that DNA can pass information on to the next generation by Hershey and Chase was further evidenced by Watson and Crick s model, which showed that DNA could encode information using the sequence of its four nucleotides. 

The Think About It question is an application of Learning Objective 3.5 and Science Practice 6.4 because students are researching the methods by which humans can manipulate heritable information and describing how those methods were based on the scientific theories and models of Watson and Crick. Possible answer: PCR allows us to make many copies of DNA for research or other applications. PCR involves separating out the two strands of DNA and adding nucleotides to the specific regions one wishes to amplify. Attaching nucleotide primers allows one to create many copies of only the desired sequences of the DNA. The ability to separate DNA and amplify select regions depends on the knowledge of nucleotide bonding within the DNA molecule described in the Watson and Crick model. DNA Sequencing Techniques 

Until the 1990s, the sequencing of DNA (reading the sequence of DNA) was a relatively expensive and long process. Using radiolabeled nucleotides also compounded the problem through safety concerns. With currently available technology and automated machines, the process is cheap, safer, and can be completed in a matter of hours. Fred Sanger developed the sequencing method used for the human genome sequencing project, which is widely used today ( [link] ). 

Visit this site to watch a video explaining the DNA sequence reading technique that resulted from Sanger s work. 

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The method is known as the dideoxy chain termination method. The sequencing method is based on the use of chain terminators, the dideoxynucleotides (ddNTPs). The dideoxynucleotides, or ddNTPSs, differ from the deoxynucleotides by the lack of a free 3' OH group on the five-carbon sugar. If a ddNTP is added to a growing a DNA strand, the chain is not extended any further because the free 3' OH group needed to add another nucleotide is not available. By using a predetermined ratio of deoxyribonucleotides to dideoxynucleotides, it is possible to generate DNA fragments of different sizes. In Frederick Sanger's dideoxy chain termination method, dye-labeled dideoxynucleotides are used to generate DNA fragments that terminate at different points. The DNA is separated by capillary electrophoresis on the basis of size, and from the order of fragments formed, the DNA sequence can be read. The DNA sequence readout is shown on an electropherogram that is generated by a laser scanner. 

The DNA sample to be sequenced is denatured or separated into two strands by heating it to high temperatures. The DNA is divided into four tubes in which a primer, DNA polymerase, and all four nucleotides (A, T, G, and C) are added. In addition to each of the four tubes, limited quantities of one of the four dideoxynucleotides are added to each tube respectively. The tubes are labeled as A, T, G, and C according to the ddNTP added. For detection purposes, each of the four dideoxynucleotides carries a different fluorescent label. Chain elongation continues until a fluorescent dideoxy nucleotide is incorporated, after which no further elongation takes place. After the reaction is over, electrophoresis is performed. Even a difference in length of a single base can be detected. The sequence is read from a laser scanner. For his work on DNA sequencing, Sanger received a Nobel Prize in chemistry in 1980. 

Sanger s genome sequencing has led to a race to sequence human genomes at a rapid speed and low cost, often referred to as the $1000 in one day sequence. Learn more by selecting the Sequencing at Speed animation here . 

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Gel electrophoresis is a technique used to separate DNA fragments of different sizes. Usually the gel is made of a chemical called agarose. Agarose powder is added to a buffer and heated. After cooling, the gel solution is poured into a casting tray. Once the gel has solidified, the DNA is loaded on the gel and electric current is applied. The DNA has a net negative charge and moves from the negative electrode toward the positive electrode. The electric current is applied for sufficient time to let the DNA separate according to size; the smallest fragments will be farthest from the well (where the DNA was loaded), and the heavier molecular weight fragments will be closest to the well. Once the DNA is separated, the gel is stained with a DNA-specific dye for viewing it ( [link] ). DNA can be separated on the basis of size using gel electrophoresis. (credit: James Jacob, Tompkins Cortland Community College) 

Neanderthal Genome: How Are We Related? The first draft sequence of the Neanderthal genome was recently published by Richard E. Green et al. in 2010. 1 Neanderthals are the closest ancestors of present-day humans. They were known to have lived in Europe and Western Asia before they disappeared from fossil records approximately 30,000 years ago. Green s team studied almost 40,000-year-old fossil remains that were selected from sites across the world. Extremely sophisticated means of sample preparation and DNA sequencing were employed because of the fragile nature of the bones and heavy microbial contamination. In their study, the scientists were able to sequence some four billion base pairs. The Neanderthal sequence was compared with that of present-day humans from across the world. After comparing the sequences, the researchers found that the Neanderthal genome had 2 to 3 percent greater similarity to people living outside Africa than to people in Africa. While current theories have suggested that all present-day humans can be traced to a small ancestral population in Africa, the data from the Neanderthal genome may contradict this view. Green and his colleagues also discovered DNA segments among people in Europe and Asia that are more similar to Neanderthal sequences than to other contemporary human sequences. Another interesting observation was that Neanderthals are as closely related to people from Papua New Guinea as to those from China or France. This is surprising because Neanderthal fossil remains have been located only in Europe and West Asia. Most likely, genetic exchange took place between Neanderthals and modern humans as modern humans emerged out of Africa, before the divergence of Europeans, East Asians, and Papua New Guineans. 

Several genes seem to have undergone changes from Neanderthals during the evolution of present-day humans. These genes are involved in cranial structure, metabolism, skin morphology, and cognitive development. One of the genes that is of particular interest is RUNX2 , which is different in modern day humans and Neanderthals. This gene is responsible for the prominent frontal bone, bell-shaped rib cage, and dental differences seen in Neanderthals. It is speculated that an evolutionary change in RUNX2 was important in the origin of modern-day humans, and this affected the cranium and the upper body. 

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Watch Svante P bo s talk explaining the Neanderthal genome research at the 2011 annual TED (Technology, Entertainment, Design) conference. 

[link] DNA Packaging in Cells 

When comparing prokaryotic cells to eukaryotic cells, prokaryotes are much simpler than eukaryotes in many of their features ( [link] ). Most prokaryotes contain a single, circular chromosome that is found in an area of the cytoplasm called the nucleoid. 

A eukaryote contains a well-defined nucleus, whereas in prokaryotes, the chromosome lies in the cytoplasm in an area called the nucleoid. 

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The size of the genome in one of the most well-studied prokaryotes, E.coli, is 4.6 million base pairs (approximately 1.1 mm, if cut and stretched out). So how does this fit inside a small bacterial cell? The DNA is twisted by what is known as supercoiling. Supercoiling means that DNA is either under-wound (less than one turn of the helix per 10 base pairs) or over-wound (more than 1 turn per 10 base pairs) from its normal relaxed state. Some proteins are known to be involved in the supercoiling; other proteins and enzymes such as DNA gyrase help in maintaining the supercoiled structure. 

Eukaryotes, whose chromosomes each consist of a linear DNA molecule, employ a different type of packing strategy to fit their DNA inside the nucleus ( [link] ). At the most basic level, DNA is wrapped around proteins known as histones to form structures called nucleosomes. The histones are evolutionarily conserved proteins that are rich in basic amino acids and form an octamer. The DNA (which is negatively charged because of the phosphate groups) is wrapped tightly around the histone core. This nucleosome is linked to the next one with the help of a linker DNA. This is also known as the beads on a string structure. This is further compacted into a 30 nm fiber, which is the diameter of the structure. At the metaphase stage, the chromosomes are at their most compact, are approximately 700 nm in width, and are found in association with scaffold proteins. 

In interphase, eukaryotic chromosomes have two distinct regions that can be distinguished by staining. The tightly packaged region is known as heterochromatin, and the less dense region is known as euchromatin. Heterochromatin usually contains genes that are not expressed, and is found in the regions of the centromere and telomeres. The euchromatin usually contains genes that are transcribed, with DNA packaged around nucleosomes but not further compacted. These figures illustrate the compaction of the eukaryotic chromosome. Section Summary 

The currently accepted model of the double-helix structure of DNA was proposed by Watson and Crick. Some of the salient features are that the two strands that make up the double helix are complementary and anti-parallel in nature. Deoxyribose sugars and phosphates form the backbone of the structure, and the nitrogenous bases are stacked inside. The diameter of the double helix, 2 nm, is uniform throughout. A purine always pairs with a pyrimidine; A pairs with T, and G pairs with C. One turn of the helix has ten base pairs. During cell division, each daughter cell receives a copy of the DNA by a process known as DNA replication. Prokaryotes are much simpler than eukaryotes in many of their features. Most prokaryotes contain a single, circular chromosome. In general, eukaryotic chromosomes contain a linear DNA molecule packaged into nucleosomes, and have two distinct regions that can be distinguished by staining, reflecting different states of packaging and compaction. Review Questions 

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Richard E. Green et al., A Draft Sequence of the Neandertal Genome, Science 328 (2010): 710-22. Glossary electrophoresis technique used to separate DNA fragments according to sizeBasics of DNA Replication Basics of DNA Replication 

In this section, you will explore the following questions: How does the structure of DNA provide for the process of replication? How did the Meselson and Stahl experiments support the semi-conservative nature of replication? Connection for AP Courses 

The Watson and Crick model suggested a way in which DNA could be replicated during cell division. Basically, the two strands unwind and separate where the hydrogen bonds connect the nucleotides. Each parental strand then serves as a template for a new, complementary daughter strand. Replication is said to be semi-conservative because the original information encoded in each parental strand is conserved (kept) in the daughter molecules. Thus, a newly replicated molecule of DNA consists of one old strand and one new strand. Meselson and Stahl used density differences in nitrogen isotopes to investigate replication, and their experiments supported the semi-conservative model. However, the process of replication is more complex than their model s simple description. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 and Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.3 The student is able to describe representations and models that illustrate how genetic information is copied for transmission between generations. 

Before the Meselson and Stahl experiment in 1958, scientists did not know how chromosomes replicated. Watson and Crick had suggested that replication was semi-conservative, but other scientists favored one of two other hypotheses, shown in [link] . The Meselson and Stahl experiment can be confusing. Take time to walk students through the process. 

Take some time to trace a mythical family tree, assume no recombination over time and illustrate how a chromosome from a distant ancestor might have ended up in a modern-day person. 

The elucidation of the structure of the double helix provided a hint as to how DNA divides and makes copies of itself. This model suggests that the two strands of the double helix separate during replication, and each strand serves as a template from which the new complementary strand is copied. What was not clear was how the replication took place. There were three models suggested ( [link] ): conservative, semi-conservative, and dispersive. The three suggested models of DNA replication. Grey indicates the original DNA strands, and blue indicates newly synthesized DNA. 

In conservative replication, the parental DNA remains together, and the newly formed daughter strands are together. The semi-conservative method suggests that each of the two parental DNA strands act as a template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or old strand and one new strand. In the dispersive model, both copies of DNA have double-stranded segments of parental DNA and newly synthesized DNA interspersed. 

Meselson and Stahl were interested in understanding how DNA replicates. They grew E. coli for several generations in a medium containing a heavy isotope of nitrogen ( 15 N) that gets incorporated into nitrogenous bases, and eventually into the DNA ( [link] ). Meselson and Stahl experimented with E. coli grown first in heavy nitrogen ( 15 N) then in 14 N. DNA grown in 15 N (red band) is heavier than DNA grown in 14 N (orange band), and sediments to a lower level in cesium chloride solution in an ultracentrifuge. When DNA grown in 15 N is switched to media containing 14 N, after one round of cell division the DNA sediments halfway between the 15 N and 14 N levels, indicating that it now contains fifty percent 14 N. In subsequent cell divisions, an increasing amount of DNA contains 14 N only. This data supports the semi-conservative replication model. (credit: modification of work by Mariana Ruiz Villareal) 

The E. coli culture was then shifted into medium containing 14 N and allowed to grow for one generation. The cells were harvested and the DNA was isolated. The DNA was centrifuged at high speeds in an ultracentrifuge. Some cells were allowed to grow for one more life cycle in 14 N and spun again. During the density gradient centrifugation, the DNA is loaded into a gradient (typically a salt such as cesium chloride or sucrose) and spun at high speeds of 50,000 to 60,000 rpm. Under these circumstances, the DNA will form a band according to its density in the gradient. DNA grown in 15 N will band at a higher density position than that grown in 14 N. Meselson and Stahl noted that after one generation of growth in 14 N after they had been shifted from 15 N, the single band observed was intermediate in position in between DNA of cells grown exclusively in 15 N and 14 N. This suggested either a semi-conservative or dispersive mode of replication. The DNA harvested from cells grown for two generations in 14 N formed two bands: one DNA band was at the intermediate position between 15 N and 14 N, and the other corresponded to the band of 14 N DNA. These results could only be explained if DNA replicates in a semi-conservative manner. Therefore, the other two modes were ruled out. 

During DNA replication, each of the two strands that make up the double helix serves as a template from which new strands are copied. The new strand will be complementary to the parental or old strand. When two daughter DNA copies are formed, they have the same sequence and are divided equally into the two daughter cells. 

Click through this tutorial on DNA replication. 

[link] Activity 

Design (but do not implement) an experiment to test the three models of DNA replication. Summarize the results you would expect if each of the three models of DNA replication were correct. Assume you have access in a laboratory to the following: an experimental organism such as E. coli , an unlimited variety of isotopes, test tube and centrifuge, and organic growth media. 

This activity is an application of Learning Objective 3.3 and Science Practice 1.2 because by designing an experiment, students are describing the three models that were proposed to illustrate how genetic information is copied. Section Summary 

The model for DNA replication suggests that the two strands of the double helix separate during replication, and each strand serves as a template from which the new complementary strand is copied. In conservative replication, the parental DNA is conserved, and the daughter DNA is newly synthesized. The semi-conservative method suggests that each of the two parental DNA strands acts as template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or old strand and one new strand. The dispersive mode suggested that the two copies of the DNA would have segments of parental DNA and newly synthesized DNA. Review Questions 

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[link]DNA Replication in Prokaryotes DNA Replication in Prokaryotes 

In this section, you will explore the following questions: How is DNA replicated in prokaryotes, and what are the roles of the leading and lagging strands and Okazaki fragments in the process? What is the role of DNA polymerase and other enzymes and proteins in supporting replication? Connection for AP Courses 

As was stated previously, DNA replication is more complex than simply unzipping the double helix and making new complementary strands. Replication in prokaryotes starts from a sequence of nucleotides on the chromosome called the origin of replication the point at which the DNA opens up or unzips. The enzyme helicase opens up the DNA at the point where hydrogen bonds connect the strands, resulting in the formation of a Y-shaped replication fork. Single-strand binding proteins keep the fork open. The enzyme primase synthesizes RNA primers to initiate DNA synthesis by DNA polymerase, which can add nucleotides only in the 5' to 3' direction. DNA polymerase recognizes the 3'-OH end as its landing site; thus, polymerase reads the template strand in the 3' to 5' direction and builds the complementary DNA polymer in the 5' to 3' direction. One strand called the leading strand is synthesized continuously in the direction of the replication fork (the direction in which helicase is separating the two strands), with polymerase adding new nucleotides one-by-one. However, replication of the other strand called the lagging strand occurs in a direction away from the replication fork, in short stretches of DNA known as Okazaki fragments. (Think of the activities on the lagging strand as analogous to trying to walk on a moving sidewalk that is moving in the opposite direction.) The RNA primers are replaced by DNA nucleotides, and ligase seals the DNA, creating phosphodiester bonds between the 3'-OH of one end and the 5'-phosphate of the other strand. The replicated DNA molecules now consist of one original template strand and one newly synthesized strand. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.3 The student is able to describe representations and models that illustrate how genetic information is copied for transmission between generations. 

Use the ten steps summarizing the process of DNA replication listed just prior to [link] in the text as an outline for discussing DNA replication in prokaryotes. 

DNA replication has been extremely well studied in prokaryotes primarily because of the small size of the genome and the mutants that are available. E. coli has 4.6 million base pairs in a single circular chromosome and all of it gets replicated in approximately 42 minutes, starting from a single origin of replication and proceeding around the circle in both directions. This means that approximately 1000 nucleotides are added per second. The process is quite rapid and occurs without many mistakes. 

DNA replication employs a large number of proteins and enzymes, each of which plays a critical role during the process. One of the key players is the enzyme DNA polymerase, also known as DNA pol, which adds nucleotides one by one to the growing DNA chain that are complementary to the template strand. The addition of nucleotides requires energy; this energy is obtained from the nucleotides that have three phosphates attached to them, similar to ATP which has three phosphate groups attached. When the bond between the phosphates is broken, the energy released is used to form the phosphodiester bond between the incoming nucleotide and the growing chain. In prokaryotes, three main types of polymerases are known: DNA pol I, DNA pol II, and DNA pol III. It is now known that DNA pol III is the enzyme required for DNA synthesis; DNA pol I and DNA pol II are primarily required for repair. 

How does the replication machinery know where to begin? It turns out that there are specific nucleotide sequences called origins of replication where replication begins. In E. coli, which has a single origin of replication on its one chromosome (as do most prokaryotes), it is approximately 245 base pairs long and is rich in AT sequences. The origin of replication is recognized by certain proteins that bind to this site. An enzyme called helicase unwinds the DNA by breaking the hydrogen bonds between the nitrogenous base pairs. ATP hydrolysis is required for this process. As the DNA opens up, Y-shaped structures called replication forks are formed. Two replication forks are formed at the origin of replication and these get extended bi- directionally as replication proceeds. Single-strand binding proteins coat the single strands of DNA near the replication fork to prevent the single-stranded DNA from winding back into a double helix. DNA polymerase is able to add nucleotides only in the 5' to 3' direction (a new DNA strand can be only extended in this direction). It also requires a free 3'-OH group to which it can add nucleotides by forming a phosphodiester bond between the 3'-OH end and the 5' phosphate of the next nucleotide. This essentially means that it cannot add nucleotides if a free 3'-OH group is not available. Then how does it add the first nucleotide? The problem is solved with the help of a primer that provides the free 3'-OH end. Another enzyme, RNA primase , synthesizes an RNA primer that is about five to ten nucleotides long and complementary to the DNA. Because this sequence primes the DNA synthesis, it is appropriately called the primer . DNA polymerase can now extend this RNA primer, adding nucleotides one by one that are complementary to the template strand ( [link] ). 

A replication fork is formed when helicase separates the DNA strands at the origin of replication. The DNA tends to become more highly coiled ahead of the replication fork. Topoisomerase breaks and reforms DNA s phosphate backbone ahead of the replication fork, thereby relieving the pressure that results from this supercoiling. Single-strand binding proteins bind to the single-stranded DNA to prevent the helix from re-forming. Primase synthesizes an RNA primer. DNA polymerase III uses this primer to synthesize the daughter DNA strand. On the leading strand, DNA is synthesized continuously, whereas on the lagging strand, DNA is synthesized in short stretches called Okazaki fragments. DNA polymerase I replaces the RNA primer with DNA. DNA ligase seals the gaps between the Okazaki fragments, joining the fragments into a single DNA molecule. (credit: modification of work by Mariana Ruiz Villareal) 

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The replication fork moves at the rate of 1000 nucleotides per second. DNA polymerase can only extend in the 5' to 3' direction, which poses a slight problem at the replication fork. As we know, the DNA double helix is anti-parallel; that is, one strand is in the 5' to 3' direction and the other is oriented in the 3' to 5' direction. One strand, which is complementary to the 3' to 5' parental DNA strand, is synthesized continuously towards the replication fork because the polymerase can add nucleotides in this direction. This continuously synthesized strand is known as the leading strand . The other strand, complementary to the 5' to 3' parental DNA, is extended away from the replication fork, in small fragments known as Okazaki fragments , each requiring a primer to start the synthesis. Okazaki fragments are named after the Japanese scientist who first discovered them. The strand with the Okazaki fragments is known as the lagging strand . 

The leading strand can be extended by one primer alone, whereas the lagging strand needs a new primer for each of the short Okazaki fragments. The overall direction of the lagging strand will be 3' to 5', and that of the leading strand 5' to 3'. A protein called the sliding clamp holds the DNA polymerase in place as it continues to add nucleotides. The sliding clamp is a ring-shaped protein that binds to the DNA and holds the polymerase in place. Topoisomerase prevents the over-winding of the DNA double helix ahead of the replication fork as the DNA is opening up; it does so by causing temporary nicks in the DNA helix and then resealing it. As synthesis proceeds, the RNA primers are replaced by DNA. The primers are removed by the exonuclease activity of DNA pol I, and the gaps are filled in by deoxyribonucleotides. The nicks that remain between the newly synthesized DNA (that replaced the RNA primer) and the previously synthesized DNA are sealed by the enzyme DNA ligase that catalyzes the formation of phosphodiester linkage between the 3'-OH end of one nucleotide and the 5' phosphate end of the other fragment. 

Once the chromosome has been completely replicated, the two DNA copies move into two different cells during cell division. The process of DNA replication can be summarized as follows: DNA unwinds at the origin of replication. Helicase opens up the DNA-forming replication forks; these are extended bidirectionally. Single-strand binding proteins coat the DNA around the replication fork to prevent rewinding of the DNA. Topoisomerase binds at the region ahead of the replication fork to prevent supercoiling. Primase synthesizes RNA primers complementary to the DNA strand. DNA polymerase starts adding nucleotides to the 3'-OH end of the primer. Elongation of both the lagging and the leading strand continues. RNA primers are removed by exonuclease activity. Gaps are filled by DNA pol by adding dNTPs. The gap between the two DNA fragments is sealed by DNA ligase, which helps in the formation of phosphodiester bonds. 



[link] summarizes the enzymes involved in prokaryotic DNA replication and the functions of each. Prokaryotic DNA Replication: Enzymes and Their Functions Enzyme/protein Specific Function DNA pol I Exonuclease activity removes RNA primer and replaces with newly synthesized DNA DNA pol II Repair function DNA pol III Main enzyme that adds nucleotides in the 5'-3' direction Helicase Opens the DNA helix by breaking hydrogen bonds between the nitrogenous bases Ligase Seals the gaps between the Okazaki fragments to create one continuous DNA strand Primase Synthesizes RNA primers needed to start replication Sliding Clamp Helps to hold the DNA polymerase in place when nucleotides are being added Topoisomerase Helps relieve the stress on DNA when unwinding by causing breaks and then resealing the DNA Single-strand binding proteins (SSB) Binds to single-stranded DNA to avoid DNA rewinding back. 

Review the full process of DNA replication here . 

[link] Activity 

Use the model of DNA you constructed in Section 14.2 to demonstrate the process of replication in prokaryotes, showing how the activities differ on the leading and lagging strands. You need to add to your model by including enzymes and other proteins involved in the replication process. Think About It 

You isolate a DNA strand in which the joining together of Okazaki fragments is impaired and suspect that a mutation has occurred in an enzyme found at the replication fork. Which enzyme is most likely mutated? 

The activity is an application of Learning Objective 3.3 and Science Practice 1.2 because students are describing the process of replication using a model of DNA. 

The Think About It question is an application of Learning Objective 3.3 and Science Practice 1.2 because students are describing the role of a particular enzyme in the process of DNA replication. Answer: The enzyme likely to be mutated is DNA ligase, which seals the gaps between the Okazaki fragments. Section Summary 

Replication in prokaryotes starts from a sequence found on the chromosome called the origin of replication the point at which the DNA opens up. Helicase opens up the DNA double helix, resulting in the formation of the replication fork. Single-strand binding proteins bind to the single-stranded DNA near the replication fork to keep the fork open. Primase synthesizes an RNA primer to initiate synthesis by DNA polymerase, which can add nucleotides only in the 5' to 3' direction. One strand is synthesized continuously in the direction of the replication fork; this is called the leading strand. The other strand is synthesized in a direction away from the replication fork, in short stretches of DNA known as Okazaki fragments. This strand is known as the lagging strand. Once replication is completed, the RNA primers are replaced by DNA nucleotides and the DNA is sealed with DNA ligase, which creates phosphodiester bonds between the 3'-OH of one end and the 5' phosphate of the other strand. Review Questions 

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[link] Glossary helicase during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds lagging strand during replication, the strand that is replicated in short fragments and away from the replication fork leading strand strand that is synthesized continuously in the 5'-3' direction which is synthesized in the direction of the replication fork ligase enzyme that catalyzes the formation of a phosphodiester linkage between the 3' OH and 5' phosphate ends of the DNA Okazaki fragment DNA fragment that is synthesized in short stretches on the lagging strand primase enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand primer short stretch of nucleotides that is required to initiate replication; in the case of replication, the primer has RNA nucleotides replication fork Y-shaped structure formed during initiation of replication single-strand binding protein during replication, protein that binds to the single-stranded DNA; this helps in keeping the two strands of DNA apart so that they may serve as templates sliding clamp ring-shaped protein that holds the DNA pol on the DNA strand topoisomerase enzyme that causes underwinding or overwinding of DNA when DNA replication is taking placeDNA Replication in Eukaryotes DNA Replication in Eukaryotes 

In this section, you will explore the following questions: What are the similarities and differences between DNA replication in eukaryotes and prokaryotes? What is the role of telomerase in DNA replication? Connection for AP Courses 

Concepts and examples described in this section are not in scope for AP. However, the roles of telomeres and telomerase in aging and cancer are informative and build on your knowledge of DNA replication in prokaryotes. 

Contrast eukaryotic DNA replication with prokaryotic replication. [link] is useful. Obtain illustrations of the process in eukaryotic cells that allow students to view the details. 

Combine these topics in a discussion of telomeres, aging, and cancer. Students might think that telomere length explains differences in life spans among different animals, such as humans and dogs. Explain that this might be a tempting conclusion, but some long-lived species, such as humans, have shorter telomeres than mice, which live only a few years. 

Eukaryotic genomes are much more complex and larger in size than prokaryotic genomes. The human genome has three billion base pairs per haploid set of chromosomes, and 6 billion base pairs are replicated during the S phase of the cell cycle. There are multiple origins of replication on the eukaryotic chromosome; humans can have up to 100,000 origins of replication. The rate of replication is approximately 100 nucleotides per second, much slower than prokaryotic replication. In yeast, which is a eukaryote, special sequences known as Autonomously Replicating Sequences (ARS) are found on the chromosomes. These are equivalent to the origin of replication in E. coli . 

The number of DNA polymerases in eukaryotes is much more than prokaryotes: 14 are known, of which five are known to have major roles during replication and have been well studied. They are known as pol , pol , pol , pol , and pol . 

The essential steps of replication are the same as in prokaryotes. Before replication can start, the DNA has to be made available as template. Eukaryotic DNA is bound to basic proteins known as histones to form structures called nucleosomes. The chromatin (the complex between DNA and proteins) may undergo some chemical modifications, so that the DNA may be able to slide off the proteins or be accessible to the enzymes of the DNA replication machinery. At the origin of replication, a pre-replication complex is made with other initiator proteins. Other proteins are then recruited to start the replication process ( [link] ). 

A helicase using the energy from ATP hydrolysis opens up the DNA helix. Replication forks are formed at each replication origin as the DNA unwinds. The opening of the double helix causes over-winding, or supercoiling, in the DNA ahead of the replication fork. These are resolved with the action of topoisomerases. Primers are formed by the enzyme primase, and using the primer, DNA pol can start synthesis. While the leading strand is continuously synthesized by the enzyme pol , the lagging strand is synthesized by pol . A sliding clamp protein known as PCNA (Proliferating Cell Nuclear Antigen) holds the DNA pol in place so that it does not slide off the DNA. RNase H removes the RNA primer, which is then replaced with DNA nucleotides. The Okazaki fragments in the lagging strand are joined together after the replacement of the RNA primers with DNA. The gaps that remain are sealed by DNA ligase, which forms the phosphodiester bond. Telomere Replication 

Unlike prokaryotic chromosomes, eukaryotic chromosomes are linear. As you ve learned, the enzyme DNA pol can add nucleotides only in the 5' to 3' direction. In the leading strand, synthesis continues until the end of the chromosome is reached. On the lagging strand, DNA is synthesized in short stretches, each of which is initiated by a separate primer. When the replication fork reaches the end of the linear chromosome, there is no place for a primer to be made for the DNA fragment to be copied at the end of the chromosome. These ends thus remain unpaired, and over time these ends may get progressively shorter as cells continue to divide. 

The ends of the linear chromosomes are known as telomeres , which have repetitive sequences that code for no particular gene. In a way, these telomeres protect the genes from getting deleted as cells continue to divide. In humans, a six base pair sequence, TTAGGG, is repeated 100 to 1000 times. The discovery of the enzyme telomerase ( [link] ) helped in the understanding of how chromosome ends are maintained. The telomerase enzyme contains a catalytic part and a built-in RNA template. It attaches to the end of the chromosome, and complementary bases to the RNA template are added on the 3' end of the DNA strand. Once the 3' end of the lagging strand template is sufficiently elongated, DNA polymerase can add the nucleotides complementary to the ends of the chromosomes. Thus, the ends of the chromosomes are replicated. The ends of linear chromosomes are maintained by the action of the telomerase enzyme. 

Telomerase is typically active in germ cells and adult stem cells. It is not active in adult somatic cells. For her discovery of telomerase and its action, Elizabeth Blackburn ( [link] ) received the Nobel Prize for Medicine and Physiology in 2009. Elizabeth Blackburn, 2009 Nobel Laureate, is the scientist who discovered how telomerase works. (credit: US Embassy Sweden) Telomerase and Aging 

Cells that undergo cell division continue to have their telomeres shortened because most somatic cells do not make telomerase. This essentially means that telomere shortening is associated with aging. With the advent of modern medicine, preventative health care, and healthier lifestyles, the human life span has increased, and there is an increasing demand for people to look younger and have a better quality of life as they grow older. 

In 2010, scientists found that telomerase can reverse some age-related conditions in mice. This may have potential in regenerative medicine. 1 Telomerase-deficient mice were used in these studies; these mice have tissue atrophy, stem cell depletion, organ system failure, and impaired tissue injury responses. Telomerase reactivation in these mice caused extension of telomeres, reduced DNA damage, reversed neurodegeneration, and improved the function of the testes, spleen, and intestines. Thus, telomere reactivation may have potential for treating age-related diseases in humans. 

Cancer is characterized by uncontrolled cell division of abnormal cells. The cells accumulate mutations, proliferate uncontrollably, and can migrate to different parts of the body through a process called metastasis. Scientists have observed that cancerous cells have considerably shortened telomeres and that telomerase is active in these cells. Interestingly, only after the telomeres were shortened in the cancer cells did the telomerase become active. If the action of telomerase in these cells can be inhibited by drugs during cancer therapy, then the cancerous cells could potentially be stopped from further division. Difference between Prokaryotic and Eukaryotic Replication Property Prokaryotes Eukaryotes Origin of replication Single Multiple Rate of replication 1000 nucleotides/s 50 to 100 nucleotides/s DNA polymerase types 5 14 Telomerase Not present Present RNA primer removal DNA pol I RNase H Strand elongation DNA pol III Pol , pol Sliding clamp Sliding clamp PCNA Section Summary 

Replication in eukaryotes starts at multiple origins of replication. The mechanism is quite similar to prokaryotes. A primer is required to initiate synthesis, which is then extended by DNA polymerase as it adds nucleotides one by one to the growing chain. The leading strand is synthesized continuously, whereas the lagging strand is synthesized in short stretches called Okazaki fragments. The RNA primers are replaced with DNA nucleotides; the DNA remains one continuous strand by linking the DNA fragments with DNA ligase. The ends of the chromosomes pose a problem as polymerase is unable to extend them without a primer. Telomerase, an enzyme with an inbuilt RNA template, extends the ends by copying the RNA template and extending one end of the chromosome. DNA polymerase can then extend the DNA using the primer. In this way, the ends of the chromosomes are protected. Review Questions 

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[link] Footnotes 1 Jaskelioff et al., Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice, Nature 469 (2011): 102-7. Glossary telomerase enzyme that contains a catalytic part and an inbuilt RNA template; it functions to maintain telomeres at chromosome ends telomere DNA at the end of linear chromosomesDNA Repair DNA Repair 

In this section, you will explore the following questions: What are different types of mutations in DNA and the significance of mutations? What are examples of mechanisms that repair mutations in DNA? Connection for AP Courses 

DNA polymerase is an efficient enzyme but it can make mistakes while adding nucleotides during replication. It edits the DNA by proofreading every newly added base. An incorrect base is removed and replaced by the correct base. If a base remains mismatched, special repair enzymes can often recognize the wrongly incorporated base, excise it from the DNA, and replace it with the correct base. Most mistakes are corrected, but if they are not they may result in a mutation, which is defined as a permanent change in a DNA sequence. A mutation can be passed to daughter cells through DNA replication and cell division. There are several types of DNA mutations, including substitution, deletion, insertion, and translocation. Mutations in repair genes may lead to serious consequences, such as cancer. Mutations can be induced by environmental factors, such as UV radiation, or they can occur spontaneously. (We will explore the effects of mutation in more detail in a later chapter. Remember that mutations are not always detrimental. They can be beneficial, too. Changes in DNA increase genetic variation the foundation of evolution by natural selection.) 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.C.1 Changes in genotype can result in changes in phenotype. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. Essential Knowledge 3.C.1 Changes in genotype can result in changes in phenotype. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.25 The student can create a visual representation to illustrate how changes in a DNA nucleotide sequence can result in a change in the polypeptide produced. Essential Knowledge 3.C.2 Biological systems have multiple processes that increase genetic variation. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.28 The student is able to construct an explanation of the multiple processes that increase variation within a population. 

Emphasize that mistakes in replication occur on a regular basis and that most are repaired or are not significant. Use Images to illustrate the effects of different types of mutations. 

Have the class research specific mutations that cause different diseases. Ask the questions: Where are the mutations? How often do they occur? Why are these mistakes not corrected? Can they be corrected through gene therapy? 

Ask the class if it is possible that a silent mutation might be a benefit to the individual or species at a later time. 

DNA replication is a highly accurate process, but mistakes can occasionally occur, such as a DNA polymerase inserting a wrong base. Uncorrected mistakes may sometimes lead to serious consequences, such as cancer. Repair mechanisms correct the mistakes. In rare cases, mistakes are not corrected, leading to mutations; in other cases, repair enzymes are themselves mutated or defective. 

Most of the mistakes during DNA replication are promptly corrected by DNA polymerase by proofreading the base that has been just added ( [link] ). In proofreading , the DNA pol reads the newly added base before adding the next one, so a correction can be made. The polymerase checks whether the newly added base has paired correctly with the base in the template strand. If it is the right base, the next nucleotide is added. If an incorrect base has been added, the enzyme makes a cut at the phosphodiester bond and releases the wrong nucleotide. This is performed by the exonuclease action of DNA pol III. Once the incorrect nucleotide has been removed, a new one will be added again. Proofreading by DNA polymerase corrects errors during replication. 

Some errors are not corrected during replication, but are instead corrected after replication is completed; this type of repair is known as mismatch repair ( [link] ). The enzymes recognize the incorrectly added nucleotide and excise it; this is then replaced by the correct base. If this remains uncorrected, it may lead to more permanent damage. How do mismatch repair enzymes recognize which of the two bases is the incorrect one? In E. coli , after replication, the nitrogenous base adenine acquires a methyl group; the parental DNA strand will have methyl groups, whereas the newly synthesized strand lacks them. Thus, DNA polymerase is able to remove the wrongly incorporated bases from the newly synthesized, non-methylated strand. In eukaryotes, the mechanism is not very well understood, but it is believed to involve recognition of unsealed nicks in the new strand, as well as a short-term continuing association of some of the replication proteins with the new daughter strand after replication has completed. In mismatch repair, the incorrectly added base is detected after replication. The mismatch repair proteins detect this base and remove it from the newly synthesized strand by nuclease action. The gap is now filled with the correctly paired base. 

In another type of repair mechanism, nucleotide excision repair , enzymes replace incorrect bases by making a cut on both the 3' and 5' ends of the incorrect base ( [link] ). The segment of DNA is removed and replaced with the correctly paired nucleotides by the action of DNA pol. Once the bases are filled in, the remaining gap is sealed with a phosphodiester linkage catalyzed by DNA ligase. This repair mechanism is often employed when UV exposure causes the formation of pyrimidine dimers. Nucleotide excision repairs thymine dimers. When exposed to UV, thymines lying adjacent to each other can form thymine dimers. In normal cells, they are excised and replaced. 

A well-studied example of mistakes not being corrected is seen in people suffering from xeroderma pigmentosa ( [link] ). Affected individuals have skin that is highly sensitive to UV rays from the sun. When individuals are exposed to UV, pyrimidine dimers, especially those of thymine, are formed; people with xeroderma pigmentosa are not able to repair the damage. These are not repaired because of a defect in the nucleotide excision repair enzymes, whereas in normal individuals, the thymine dimers are excised and the defect is corrected. The thymine dimers distort the structure of the DNA double helix, and this may cause problems during DNA replication. People with xeroderma pigmentosa may have a higher risk of contracting skin cancer than those who dont have the condition. Xeroderma pigmentosa is a condition in which thymine dimerization from exposure to UV is not repaired. Exposure to sunlight results in skin lesions. (credit: James Halpern et al.) 

Errors during DNA replication are not the only reason why mutations arise in DNA. Mutations , variations in the nucleotide sequence of a genome, can also occur because of damage to DNA. Such mutations may be of two types: induced or spontaneous. Induced mutations are those that result from an exposure to chemicals, UV rays, x-rays, or some other environmental agent. Spontaneous mutations occur without any exposure to any environmental agent; they are a result of natural reactions taking place within the body. 

Mutations may have a wide range of effects. Some mutations are not expressed; these are known as silent mutations . Point mutations are those mutations that affect a single base pair. The most common nucleotide mutations are substitutions, in which one base is replaced by another. These can be of two types, either transitions or transversions. Transition substitution refers to a purine or pyrimidine being replaced by a base of the same kind; for example, a purine such as adenine may be replaced by the purine guanine. Transversion substitution refers to a purine being replaced by a pyrimidine, or vice versa; for example, cytosine, a pyrimidine, is replaced by adenine, a purine. Mutations can also be the result of the addition of a base, known as an insertion, or the removal of a base, also known as deletion. Sometimes a piece of DNA from one chromosome may get translocated to another chromosome or to another region of the same chromosome; this is also known as translocation. These mutation types are shown in [link] . 

Sometimes a nucleotide is overlooked by the DNA repair system for no known reason. This malignant melanoma is the result of DNA not undergoing repair after too much UV exposure. 

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Mutations can lead to changes in the protein sequence encoded by the DNA. 

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Mutations in repair genes have been known to cause cancer. Many mutated repair genes have been implicated in certain forms of pancreatic cancer, colon cancer, and colorectal cancer. Mutations can affect either somatic cells or germ cells. If many mutations accumulate in a somatic cell, they may lead to problems such as the uncontrolled cell division observed in cancer. If a mutation takes place in germ cells, the mutation will be passed on to the next generation, as in the case of hemophilia and xeroderma pigmentosa. Think About It 

Infertility can sometimes be explained by chromosome translocations. Explain how chromosome translocations can cause infertility. Are there times when a chromosome translocation might not result in infertility? 

The Think About It question is an application of Learning Objective 3.28 and Science Practice 6.2 because students are asked to explain a phenomenon that increases genetic variation. Answer If a chromosome translocation occurs in a germ cell it could affect the function of genes required for the formation of reproductive cells. If severe enough, the mutation could give rise to infertility. A translocation in a germ cell that does not affect genes required for sex cell formation would likely not affect fertility. Neither would a translocation that occurs in a somatic cell. Section Summary 

DNA polymerase can make mistakes while adding nucleotides. It edits the DNA by proofreading every newly added base. Incorrect bases are removed and replaced by the correct base, and then a new base is added. Most mistakes are corrected during replication, although when this does not happen, the mismatch repair mechanism is employed. Mismatch repair enzymes recognize the wrongly incorporated base and excise it from the DNA, replacing it with the correct base. In yet another type of repair, nucleotide excision repair, the incorrect base is removed along with a few bases on the 5' and 3' end, and these are replaced by copying the template with the help of DNA polymerase. The ends of the newly synthesized fragment are attached to the rest of the DNA using DNA ligase, which creates a phosphodiester bond. 

Most mistakes are corrected, and if they are not, they may result in a mutation defined as a permanent change in the DNA sequence. Mutations can be of many types, such as substitution, deletion, insertion, and translocation. Mutations in repair genes may lead to serious consequences such as cancer. Mutations can be induced or may occur spontaneously. Review Questions 

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[link] Glossary induced mutation mutation that results from exposure to chemicals or environmental agents mutation variation in the nucleotide sequence of a genome mismatch repair type of repair mechanism in which mismatched bases are removed after replication nucleotide excision repair type of DNA repair mechanism in which the wrong base, along with a few nucleotides upstream or downstream, are removed proofreading function of DNA pol in which it reads the newly added base before adding the next one point mutation mutation that affects a single base silent mutation mutation that is not expressed spontaneous mutation mutation that takes place in the cells as a result of chemical reactions taking place naturally without exposure to any external agent transition substitution when a purine is replaced with a purine or a pyrimidine is replaced with another pyrimidine transversion substitution when a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purineIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Genes, which are carried on (a) chromosomes, are linearly organized instructions for making the RNA and protein molecules that are necessary for all of processes of life. The (b) interleukin-2 protein and (c) alpha-2u-globulin protein are just two examples of the array of different molecular structures that are encoded by genes. (credit chromosome: National Human Genome Research Institute; credit interleukin-2 : Ramin Herati/Created from PDB 1M47 and rendered with Pymol; credit alpha-2u-globulin : Darren Logan/rendered with AISMIG) 

The definition of gene has progressed from being an abstract unit of heredity in Mendel s time to our current concept of a tangible molecular entity capable of replication, expression, and mutation ( [link] ). Currently, we can perform tests for many genetic diseases, but these tests create ethical and legal issues. For example, would you want to be tested for a debilitating genetic disease if there was the possibility insurance companies could use that information to deny you coverage? Fortunately, the Genetic Information Nondiscrimination Act of 2008 protects American citizens from discrimination from both insurance companies and employers based on genetic information. More information about policy, legal, and ethical issues in genetic research can be found here . 

Introduce students to the Human Genome Project. The project was started in the late 80 s when sequencing was both costly and time consuming. The entire sequence of the human genome was announced in 2003. By then, both the expense and time required for sequencing had dropped considerably. The information can easily be stored and disseminated. As can be expected, with the advent of new technology come moral questions that society must ask. 

Ask students if they would like their genomes to be sequenced. What would they gain by such knowledge? Have them consider who would versus who should have access to that information. Have students balance the benefits of being aware of a predisposition to a certain condition to the risk of having employment or health insurance denied. For some diseases, it is possible with the information on hand to modify one s lifestyle and increase screening for early detection of the condition. What happens if there are no cures, as is the case for Huntington s disease? This is the context of the Genetic Information Nondiscrimination Act. To learn more about it, read this summary .The Genetic Code The Genetic Code 

In this section, you will explore the following questions: What is the Central Dogma of protein synthesis? What is the genetic code, and how does nucleotide sequence prescribe the amino acid and polypeptide sequence? Connection for AP Courses 

Since the rediscovery of Mendel s work in the 1900s, scientists have learned much about how the genetic blueprints stored in DNA are capable of replication, expression, and mutation. Just as the 26 letters of the English alphabet can be arranged into what seems to be a limitless number of words, with new ones added to the dictionary every year, the four nucleotides of DNA A, T, C, and G can generate sequences of DNA called genes that specify tens of thousands of polymers of amino acids. In turn, these sequences can be transcribed into mRNA and translated into proteins which orchestrate nearly every function of the cell. The genetic code refers to the DNA alphabet (A, T, C, G), the RNA alphabet (A, U, C, G), and the polypeptide alphabet (20 amino acids). But how do genes located on a chromosome ultimately produce a polypeptide that can result in a physical phenotype such as hair or eye color or a disease like cystic fibrosis or hemophilia? 

The Central Dogma describes the normal flow of genetic information from DNA to mRNA to protein: DNA in genes specify sequences of mRNA which, in turn, specify amino acid sequences in proteins. The process requires two steps, transcription and translation. During transcription, genes are used to make messenger RNA (mRNA). In turn, the mRNA is used to direct the synthesis of proteins during the process of translation. Translation also requires two other types of RNA: transfer RNA (tRNA) and ribosomal RNA (rRNA). The genetic code is a triplet code, with each RNA codon consisting of three consecutive nucleotides that specify one amino acid or the release of the newly formed polypeptide chain; for example, the mRNA codon CAU specifies the amino acid histidine. The code is degenerate; that is, some amino acids are specified by more than one codon, like synonyms you study in your English class (different word, same meaning). For example, CCU, CCC, CCA, and CCG are all codons for proline. It is important to remember the same genetic code is universal to almost all organisms on Earth. Small variations in codon assignment exist in mitochondria and some microorganisms. 

Deviations from the simple scheme of the central dogma are discovered as researchers explore gene expression with new technology. For example the human immunodeficiency virus (HIV) is a retrovirus which stores its genetic information in single stranded RNA molecules. Upon infection of a host cell, RNA is used as a template by the virally encoded enzyme, reverse transcriptase, to synthesize DNA. The viral DNA is later transcribed into mRNA and translated into proteins. Some RNA viruses such as the influenza virus never go through a DNA step. The RNA genome is replicated by an RNA dependent RNA polymerase which is virally encoded. 

The content presented in this section supports the Learning Objectives outlined in Big Idea 1 and Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives merge Essential Knowledge content with one or more of the seven Science Practices. These Learning Objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP Exam questions. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Hereditable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structure and functions of DNA and RNA to support the claim that DNA and, in some cases, that RNA are the primary sources of heritable information. 

The Central Dogma has been validated by many experiments. The flow of information from DNA to mRNA to polypeptide is the common scheme in all cells, both prokaryotic and eukaryotic. The information in DNA is contained in the sequence of nitrogenous bases. Next question is, How is the sequence of the nitrogenous bases translated into amino acids? A combination of two out of the four letters gives 16 possible amino acids (4 2 = 16); for example, AA, or AC; but, there 20 amino acids. A combination of three bases gives 64 possible sets (4 3 = 64); for example, AAA or AAC. A combination of three bases in a row is a codon or triplets. This gives rise to more than enough combinations for the 20 common acids. Some amino acids are specified by a single codon, for example, methionine and tryptophan; others are encoded by up to six independent codons, for example, leucine. 

Although protein synthesis follows the same general scheme in prokaryotes and eukaryotes, the detailed mechanism of each can be quite different. The presence of the nuclear membrane adds a layer of complexity to the process. In prokaryotes, transcription and translation are tightly coupled. As soon as the 5'-end of a mRNA has been transcribed from the template strand of DNA, ribosomes can latch onto it and polypeptide synthesis begins. Eukaryotic cells use a more complex series of steps. The enzyme RNA polymerase forms the transcription initiation complex with many proteins called transcription factors. The product of transcription, mRNA undergoes several modifications that change its stability and facilitate export from the nucleus. These extra steps allow greater control over gene expression. Although prokaryotic mRNA is not generally modified, eukaryotic mRNA strands undergo the addition of a methyl-guanosine cap at the 5'-end and a poly-adenosine tail at the 3'- end, without which they may not exit the nucleus. The mRNA also undergoes splicing to remove introns , the non protein coding regions of the gene. Protein translation depends on the presence of ribosomes, mRNA, a full complement of tRNA molecules, many enzymes, and many protein factors. As the polypeptide is synthesized, it starts folding into its three-dimensional structure. Further modifications will ensure that the protein is fully functional and shipped to its destination. 

Ask the students what a dogma is. It will serve as an introduction to deviations from the Central Dogma. Viruses show numerous variations. The Human Immunodeficiency Virus (HIV) is a retrovirus. Its genome is encoded in RNA molecules which serve as a template for the synthesis of DNA by a virally encoded enzyme called reverse transcriptase. Point out that this enzyme, which is not found in humans, is the target of many anti-HIV medications. The flu virus carries non-coding strands of RNA molecules which are replicated in the host cell by a RNA-dependent RNA polymerase, an enzyme encoded in the viral genome. In the case of the flu virus, there is no DNA stage at all. The flow of information is RNA to RNA to proteins. Closer to home, the telomeres, the ends of the linear chromosomes in eukaryotes, are replicated by a special enzyme, a telomerase, which synthesizes DNA from an RNA template. 

Just as we transfer information using letters and numbers, the cell transfers information using molecules. Emphasize the similarities between writing and the genetic code. Tell the students that much of the vocabulary of molecular genetics is borrowed from editing: transcription, translation, proofreading, missense, nonsense, etc. 

Although the chapter does not use the term open reading frame, tie it to [link] . An open reading frame is a DNA sequence that follows a start codon and ends with a stop codon. A long open reading frame is likely to be a gene. 

Students confuse the vocabulary used to describe the Central Dogma. Copying information from DNA to RNA is transcription because the language is the same. Both are constructed using nucleotides. When a polypeptide is synthesized, the building blocks or letters have switched to amino acids. It is a translation. Although not quite identical, show students an example similar to the following: 

Dog to Dog (transcription) to Canis (translation) 

The first two words represent transcription. The letters are just copied. The last word has the same meaning, dog in Latin, but now the language is different. 

Consider using the word redundant to help explain the meaning of the word degenerate in this context. Students confuse the fact that the code is degenerate several codons can encode the same amino acid with the fact that the genetic code is universal, which means that the same codon, AUG as an example, is translated as methionine in all cells. The confusion arises from students learning the two concepts at the same time. Give examples of changes in the codons which result in the same amino acids. Although the gene sequence is different, the polypeptide is the same. Remind students that each codon specifies one amino acid, but the reverse is not true. Depending on the amino acid, more than one codon will translate to the same amino acid. 

Explain that many proteins of interest are synthesized in bacteria and yeast by inserting the genes for the proteins in the host expression systems. This is possible because the code is universal. If a gene coding for human insulin is inserted in the chromosomes of E. coli , the bacteria will synthesize human insulin. 

Give students examples of codons and ask them to find the matching amino acid. Bring to their attention that typographical errors are a great source of mutations. They should proofread their sequences carefully. 

The cellular process of transcription generates messenger RNA (mRNA), a mobile molecular copy of one or more genes with an alphabet of A, C, G, and uracil (U). Translation of the mRNA template converts nucleotide-based genetic information into a protein product. Protein sequences consist of 20 commonly occurring amino acids; therefore, it can be said that the protein alphabet consists of 20 letters ( [link] ). Each amino acid is defined by a three-nucleotide sequence called the triplet codon. Different amino acids have different chemistries (such as acidic versus basic, or polar and nonpolar) and different structural constraints. Variation in amino acid sequence gives rise to enormous variation in protein structure and function. Structures of the 20 amino acids found in proteins are shown. Each amino acid is composed of an amino group ( N H 3 + N H 3 + ), a carboxyl group (COO - ), and a side chain (blue). The side chain may be nonpolar, polar, or charged, as well as large or small. It is the variety of amino acid side chains that gives rise to the incredible variation of protein structure and function. The Central Dogma: DNA Encodes RNA; RNA Encodes Protein 

The flow of genetic information in cells from DNA to mRNA to protein is described by the Central Dogma ( [link] ), which states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins. The decoding of one molecule to another is performed by specific proteins and RNAs. Because the information stored in DNA is so central to cellular function, it makes intuitive sense that the cell would make mRNA copies of this information for protein synthesis, while keeping the DNA itself intact and protected. The copying of DNA to RNA is relatively straightforward, with one nucleotide being added to the mRNA strand for every nucleotide read in the DNA strand. The translation to protein is a bit more complex because three mRNA nucleotides correspond to one amino acid in the polypeptide sequence. However, the translation to protein is still systematic and colinear , such that nucleotides 1 to 3 correspond to amino acid 1, nucleotides 4 to 6 correspond to amino acid 2, and so on. Instructions on DNA are transcribed onto messenger RNA. Ribosomes are able to read the genetic information inscribed on a strand of messenger RNA and use this information to string amino acids together into a protein. The Genetic Code Is Degenerate and Universal 

Given the different numbers of letters in the mRNA and protein alphabets, scientists theorized that combinations of nucleotides corresponded to single amino acids. Nucleotide doublets would not be sufficient to specify every amino acid because there are only 16 possible two-nucleotide combinations (4 2 ). In contrast, there are 64 possible nucleotide triplets (4 3 ), which is far more than the number of amino acids. Scientists theorized that amino acids were encoded by nucleotide triplets and that the genetic code was degenerate . In other words, a given amino acid could be encoded by more than one nucleotide triplet. This was later confirmed experimentally; Francis Crick and Sydney Brenner used the chemical mutagen proflavin to insert one, two, or three nucleotides into the gene of a virus. When one or two nucleotides were inserted, protein synthesis was completely abolished. When three nucleotides were inserted, the protein was synthesized and functional. This demonstrated that three nucleotides specify each amino acid. These nucleotide triplets are called codons . The insertion of one or two nucleotides completely changed the triplet reading frame , thereby altering the message for every subsequent amino acid ( [link] ). Though insertion of three nucleotides caused an extra amino acid to be inserted during translation, the integrity of the rest of the protein was maintained. The deletion of two nucleotides shifts the reading frame of an mRNA and changes the entire protein message, creating a nonfunctional protein or terminating protein synthesis altogether. 

Scientists painstakingly solved the genetic code by translating synthetic mRNAs in vitro and sequencing the proteins they specified ( [link] ). This figure shows the genetic code for translating each nucleotide triplet in mRNA into an amino acid or a termination signal in a nascent protein. (credit: modification of work by NIH) 

In addition to instructing the addition of a specific amino acid to a polypeptide chain, three of the 64 codons terminate protein synthesis and release the polypeptide from the translation machinery. These triplets are called nonsense codons , or stop codons. Another codon, AUG, also has a special function. In addition to specifying the amino acid methionine, it also serves as the start codon to initiate translation. The reading frame for translation is set by the AUG start codon near the 5' end of the mRNA. 

The genetic code is universal. With a few exceptions, virtually all species use the same genetic code for protein synthesis. Conservation of codons means that a purified mRNA encoding the globin protein in horses could be transferred to a tulip cell, and the tulip would synthesize horse globin. That there is only one genetic code is powerful evidence that all of life on Earth shares a common origin, especially considering that there are about 10 84 possible combinations of 20 amino acids and 64 triplet codons. 

Transcribe a gene and translate it to protein using complementary pairing and the genetic code at this site . 

[link] Think About It 

A strand of DNA has the nucleotide sequence 3' GCT GTC AAA TTC GAT 5'. What is the sequence of mRNA that is complementary to this DNA sequence? Using the chart of codons in the text, determine the sequence of amino acids which can be generated from this strand of DNA. How does degeneracy of the genetic code make cells less vulnerable to mutations? What is an advantage of degeneracy with respect to the negative impact of random mutations on natural selection and evolution? 

The first question is an application of Learning Objective 3.1 and Science Practice 6.5 because students are explaining how the language of DNA can be transcribed and translated into a sequence of amino acids . 

The second set of questions are an application of Learning Objective 1.15 and Science Practice 3.1 because students are asked to raise questions about the universal genetic code and the impact of its degeneracy on mutations. Answer 3' GCT GTC AAA TTC GAT 5' mRNA 5' CGA CAG UUU AAG CUA 3' ; peptide Arg Gln Phe Lys Leu 

Degeneracy is believed to be a cellular mechanism to reduce the negative impact of random mutations. Codons that specify the same amino acid typically only differ by one nucleotide. In addition, amino acids with chemically similar side chains are encoded by similar codons. This nuance of the genetic code ensures that a single-nucleotide substitution mutation might either specify the same amino acid but have no effect or specify a similar amino acid, preventing the protein from being rendered completely nonfunctional. 

Which Has More DNA: A Kiwi or a Strawberry? Do you think that a kiwi or a strawberry has more DNA per fruit? (credit kiwi : "Kelbv"/Flickr; credit: strawberry : Alisdair McDiarmid) 

Question : Would a kiwifruit and strawberry that are approximately the same size ( [link] ) also have approximately the same amount of DNA? 

Background : Genes are carried on chromosomes and are made of DNA. All mammals are diploid, meaning they have two copies of each chromosome. However, not all plants are diploid. The common strawberry is octoploid (8 n ) and the cultivated kiwi is hexaploid (6 n ). Research the total number of chromosomes in the cells of each of these fruits and think about how this might correspond to the amount of DNA in these fruits cell nuclei. Read about the technique of DNA isolation to understand how each step in the isolation protocol helps liberate and precipitate DNA. 

Hypothesis : Hypothesize whether you would be able to detect a difference in DNA quantity from similarly sized strawberries and kiwis. Which fruit do you think would yield more DNA? 

Test your hypothesis : Isolate the DNA from a strawberry and a kiwi that are similarly sized. Perform the experiment in at least triplicate for each fruit. Prepare a bottle of DNA extraction buffer from 900 mL water, 50 mL dish detergent, and two teaspoons of table salt. Mix by inversion (cap it and turn it upside down a few times). Grind a strawberry and a kiwifruit by hand in a plastic bag, or using a mortar and pestle, or with a metal bowl and the end of a blunt instrument. Grind for at least two minutes per fruit. Add 10 mL of the DNA extraction buffer to each fruit, and mix well for at least one minute. Remove cellular debris by filtering each fruit mixture through cheesecloth or porous cloth and into a funnel placed in a test tube or an appropriate container. Pour ice-cold ethanol or isopropanol (rubbing alcohol) into the test tube. You should observe white, precipitated DNA. Gather the DNA from each fruit by winding it around separate glass rods. 

Record your observations : Because you are not quantitatively measuring DNA volume, you can record for each trial whether the two fruits produced the same or different amounts of DNA as observed by eye. If one or the other fruit produced noticeably more DNA, record this as well. Determine whether your observations are consistent with several pieces of each fruit. 

Analyze your data : Did you notice an obvious difference in the amount of DNA produced by each fruit? Were your results reproducible? 

Draw a conclusion : Given what you know about the number of chromosomes in each fruit, can you conclude that chromosome number necessarily correlates to DNA amount? Can you identify any drawbacks to this procedure? If you had access to a laboratory, how could you standardize your comparison and make it more quantitative? Section Summary 

The genetic code refers to the DNA alphabet (A, T, C, G), the RNA alphabet (A, U, C, G), and the polypeptide alphabet (20 amino acids). The Central Dogma describes the flow of genetic information in the cell from genes to mRNA to proteins. Genes are used to make mRNA by the process of transcription; mRNA is used to synthesize proteins by the process of translation. The genetic code is degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three nonsense codons. Almost every species on the planet uses the same genetic code. Review Questions 

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[link] Glossary Central Dogma states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins codon three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation colinear in terms of RNA and protein, three units of RNA (nucleotides) specify one unit of protein (amino acid) in a consecutive fashion degeneracy (of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous nonsense codon one of the three mRNA codons that specifies termination of translation reading frame sequence of triplet codons in mRNA that specify a particular protein; a ribosome shift of one or two nucleotides in either direction completely abolishes synthesis of that proteinProkaryotic Transcription Prokaryotic Transcription 

In this section, you will explore the following questions: What are the steps, in order, in prokaryotic transcription? How and when is transcription terminated? Connection for AP Courses 

During transcription, the enzyme RNA polymerase moves along the DNA template, reading nucleotides in a 3 to 5 direction, with U pairing with A and C with G, and assembling the mRNA transcript in a 5 to 3 direction. In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template. Transcription continues until RNA polymerase reaches a stop or terminator sequence at the end of the gene. Termination frees the mRNA and often occurs by the formation of an mRNA hairpin. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA and, in some cases, that RNA are the primary sources of heritable information. 

Ask students to draw a timeline of the steps needed for transcription and add all the different components as specific shapes. Use different colors to label the promoter and the terminator sequences. 

Review the complementarity of nitrogenous bases and the stability of base pairing as a function of number of hydrogen bonds. The couple AT/AU is much less stable than CG; therefore promoter sequences will be rich in AT because it takes less energy to unzip DNA. 

Ask the students, How do you recognize the beginning of a sentence? They may answer that they see a period. Answer that some abbreviations are followed by a period. So the period is not enough. Upper case is not enough either. It is the combination of period followed by a space and an upper case which indicates the beginning of a sentence. In the same way consensus sequences, which indicate a promoter region where an RNA polymerase binds, contain several elements that are required for recognition. 

Use a diagram to illustrate rho-independent termination. The following drawing may clarify the text in the chapter. 

There can be more than one consensus sequence in a genome as there are several sigma factors that recognize different sequences. Clarify, if necessary, the role of the sigma factor and rho proteins. Students confuse transcription, termination, and stop codons. 

Ask students to diagram a generic gene and label the following regions in the correct sequence in the 5'-3' direction. The regions are given in the correct order here. Change the order when giving the exercise to the class: 

Sigma binding consensus sequence/TATA box 

Shine Dalgarno sequence (binding to ribosome) 

ATG (start codon for protein transcription) 

STOP codon (polypeptide termination) 

Terminator region 

Students have difficulty visualizing polycistronic messages. Explain that as long as there are stop codons in the message, the polypeptides will be released and ribosomes reattached at the following Shine-Dalgarno sequence. If one were to write out the structure of a polycistronic mRNA, it would be Shine-Dalgarno-AUG-------STOP---Shine-Dalgarno AUG-------STOP---Shine-Dalgarno AUG---STOP. 

The prokaryotes, which include bacteria and archaea, are mostly single-celled organisms that, by definition, lack membrane-bound nuclei and other organelles. A bacterial chromosome is a covalently closed circle that, unlike eukaryotic chromosomes, is not organized around histone proteins. The central region of the cell in which prokaryotic DNA resides is called the nucleoid. In addition, prokaryotes often have abundant plasmids , which are shorter circular DNA molecules that may only contain one or a few genes. Plasmids can be transferred independently of the bacterial chromosome during cell division and often carry traits such as antibiotic resistance. 

Transcription in prokaryotes (and in eukaryotes) requires the DNA double helix to partially unwind in the region of mRNA synthesis. The region of unwinding is called a transcription bubble. Transcription always proceeds from the same DNA strand for each gene, which is called the template strand . The mRNA product is complementary to the template strand and is almost identical to the other DNA strand, called the nontemplate strand . The only difference is that in mRNA, all of the T nucleotides are replaced with U nucleotides. In an RNA double helix, A can bind U via two hydrogen bonds, just as in A T pairing in a DNA double helix. 

The nucleotide pair in the DNA double helix that corresponds to the site from which the first 5' mRNA nucleotide is transcribed is called the +1 site, or the initiation site . Nucleotides preceding the initiation site are given negative numbers and are designated upstream . Conversely, nucleotides following the initiation site are denoted with + numbering and are called downstream nucleotides. Initiation of Transcription in Prokaryotes 

Prokaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously. The intracellular level of a bacterial protein can quickly be amplified by multiple transcription and translation events occurring concurrently on the same DNA template. Prokaryotic transcription often covers more than one gene and produces polycistronic mRNAs that specify more than one protein. 

Our discussion here will exemplify transcription by describing this process in Escherichia coli , a well-studied bacterial species. Although some differences exist between transcription in E. coli and transcription in archaea, an understanding of E. coli transcription can be applied to virtually all bacterial species. Prokaryotic RNA Polymerase 

Prokaryotes use the same RNA polymerase to transcribe all of their genes. In E. coli , the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted , , , and ' comprise the polymerase core enzyme . These subunits assemble every time a gene is transcribed, and they disassemble once transcription is complete. Each subunit has a unique role; the two -subunits are necessary to assemble the polymerase on the DNA; the -subunit binds to the ribonucleoside triphosphate that will become part of the nascent recently born mRNA molecule; and the ' binds the DNA template strand. The fifth subunit, , is involved only in transcription initiation. It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site. Without , the core enzyme would transcribe from random sites and would produce mRNA molecules that specified protein gibberish. The polymerase comprised of all five subunits is called the holoenzyme . Prokaryotic Promoters 

A promoter is a DNA sequence onto which the transcription machinery binds and initiates transcription. In most cases, promoters exist upstream of the genes they regulate. The specific sequence of a promoter is very important because it determines whether the corresponding gene is transcribed all the time, some of the time, or infrequently. Although promoters vary among prokaryotic genomes, a few elements are conserved. At the -10 and -35 regions upstream of the initiation site, there are two promoter consensus sequences, or regions that are similar across all promoters and across various bacterial species ( [link] ). The -10 consensus sequence, called the -10 region, is TATAAT. The -35 sequence, TTGACA, is recognized and bound by . Once this interaction is made, the subunits of the core enzyme bind to the site. The A T-rich -10 region facilitates unwinding of the DNA template, and several phosphodiester bonds are made. The transcription initiation phase ends with the production of abortive transcripts, which are polymers of approximately 10 nucleotides that are made and released. The subunit of prokaryotic RNA polymerase recognizes consensus sequences found in the promoter region upstream of the transcription start sight. The subunit dissociates from the polymerase after transcription has been initiated. 

View this MolecularMovies animation to see the first part of transcription and the base sequence repetition of the TATA box. 

[link] Elongation and Termination in Prokaryotes 

The transcription elongation phase begins with the release of the subunit from the polymerase. The dissociation of allows the core enzyme to proceed along the DNA template, synthesizing mRNA in the 5' to 3' direction at a rate of approximately 40 nucleotides per second. As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it ( [link] ). The base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely. During elongation, the prokaryotic RNA polymerase tracks along the DNA template, synthesizes mRNA in the 5' to 3' direction, and unwinds and rewinds the DNA as it is read. Prokaryotic Termination Signals 

Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals. One is protein-based and the other is RNA-based. Rho-dependent termination is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. As a result, the rho protein collides with the polymerase. The interaction with rho releases the mRNA from the transcription bubble. 

Rho-independent termination is controlled by specific sequences in the DNA template strand. As the polymerase nears the end of the gene being transcribed, it encounters a region rich in C G nucleotides. The mRNA folds back on itself, and the complementary C G nucleotides bind together. The result is a stable hairpin that causes the polymerase to stall as soon as it begins to transcribe a region rich in A T nucleotides. The complementary U A region of the mRNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript. 

Upon termination, the process of transcription is complete. By the time termination occurs, the prokaryotic transcript would already have been used to begin synthesis of numerous copies of the encoded protein because these processes can occur concurrently. The unification of transcription, translation, and even mRNA degradation is possible because all of these processes occur in the same 5' to 3' direction, and because there is no membranous compartmentalization in the prokaryotic cell ( [link] ). In contrast, the presence of a nucleus in eukaryotic cells precludes simultaneous transcription and translation. Multiple polymerases can transcribe a single bacterial gene while numerous ribosomes concurrently translate the mRNA transcripts into polypeptides. In this way, a specific protein can rapidly reach a high concentration in the bacterial cell. 

Visit this BioStudio animation to see the process of prokaryotic transcription. 

[link] Activity 

Working in small groups, use a model of DNA to demonstrate synthesis transcription of mRNA to other groups in your class. In your demonstration, be sure to distinguish the differences between DNA and RNA, the template and non-template strands of the DNA, the directionality of transcription, and the significance of promoters. Think About It 

If mRNA is complementary to the DNA template strand, and the DNA template strand is complementary to the DNA non-template strand, are the base sequences of mRNA and the DNA non-template strand ever identical? Justify your answer. 

The activity is an application of Learning Objective 3.1 and Science Practice 6.5 because students are using a model to explain the process of transcription and how both DNA and RNA are carriers of heritable information. This activity also is an application of Learning Objective 3.21 and Science Practice 1.4 because they are using the model to describe the role of promoters in the regulation of transcription. 

The Think About It question is an application of Learning Objective 3.1 and Science Practice 6.5 because students are using a model to explain the process of transcription as well as how both DNA and RNA are carriers of heritable information. Answer DNA is different from RNA in that T nucleotides in DNA are replaced with U nucleotides in RNA. Therefore, they could never be identical in base sequence. A gene would not lack T residues as the initiation codon is AUG for methionine. Section Summary 

In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase. The prokaryotic polymerase consists of a core enzyme of four protein subunits and a protein that assists only with initiation. Elongation synthesizes mRNA in the 5' to 3' direction at a rate of 40 nucleotides per second. Termination liberates the mRNA and occurs either by rho protein interaction or by the formation of an mRNA hairpin. Review Questions 

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[link] Glossary consensus DNA sequence that is used by many species to perform the same or similar functions core enzyme prokaryotic RNA polymerase consisting of , , , and ' but missing ; this complex performs elongation downstream nucleotides following the initiation site in the direction of mRNA transcription; in general, sequences that are toward the 3' end relative to a site on the mRNA hairpin structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides holoenzyme prokaryotic RNA polymerase consisting of , , , ', and ; this complex is responsible for transcription initiation initiation site nucleotide from which mRNA synthesis proceeds in the 5' to 3' direction; denoted with a +1 nontemplate strand strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA plasmid extrachromosomal, covalently closed, circular DNA molecule that may only contain one or a few genes; common in prokaryotes promoter DNA sequence to which RNA polymerase and associated factors bind and initiate transcription Rho-dependent termination in prokaryotes, termination of transcription by an interaction between RNA polymerase and the rho protein at a run of G nucleotides on the DNA template Rho-independent termination sequence-dependent termination of prokaryotic mRNA synthesis; caused by hairpin formation in the mRNA that stalls the polymerase TATA box conserved promoter sequence in eukaryotes and prokaryotes that helps to establish the initiation site for transcription template strand strand of DNA that specifies the complementary mRNA molecule transcription bubble region of locally unwound DNA that allows for transcription of mRNA upstream nucleotides preceding the initiation site; in general, sequences toward the 5' end relative to a site on the mRNAEukaryotic Transcription Eukaryotic Transcription 

In this section, you will explore the following questions: What are the steps in eukaryotic transcription? What are the structural and functional similarities and differences among the three RNA polymerases? Connection for AP Courses 

As expected, transcription in eukaryotes is more complex than transcription in prokaryotes. First, transcription in eukaryotes involves one of three types of RNA polymerase, depending on the gene being transcribed. Second, the initiation of transcription involves the binding of several transcription factors to complex promoters which are usually located upstream of the gene being copied. Transcription factors can either activate or inhibit gene expression. Termination of transcription involves the RNA polymerases. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA and, in some cases, that RNA are the primary sources of heritable information. 

Ask students if they expect transcription to be different in eukaryotes. Ask students to explain their answers. Review the major difference between prokaryotes and eukaryotes, the presence of the nucleus. 

Explain that the process follows the same general order, but there are major differences. The initiation of transcription in eukaryotes is more complicated. Polycistronic mRNAs exist in eukaryotes although they are very rare. Remind students, if applicable, that they have encountered nuclear transcription factors when you studied cell signaling. Point out the useful role of -amanitin in differentiating between RNA polymerases. Remind students that the final product of a gene can be an RNA molecule, for example an rRNA molecule, or a polypeptide. 

Ask students to prepare a timeline of transcription in eukaryotes and compare it to their timeline of transcription in prokaryotes. Teach students a simple way to remember which are the intr ons ( in the tr ash) and which are the ex ons ( ex pressed). 

RNA polymerases in prokaryotes and eukaryotes have the same general functions; however, they are different enzymes. The numbering of RNA polymerases in eukaryotes does not reflect the order of activity. Pol II is the best studied polymerase, most likely because it transcribes mRNA. 

Ribosome assembly takes place in the nucleolus which means that the ribosomal proteins are synthesized in the cytoplasm and re-enter the nucleus. 

Prokaryotes and eukaryotes perform fundamentally the same process of transcription, with a few key differences. The most important difference between prokaryotes and eukaryotes is the latter s membrane-bound nucleus and organelles. With the genes bound in a nucleus, the eukaryotic cell must be able to transport its mRNA to the cytoplasm and must protect its mRNA from degrading before it is translated. Eukaryotes also employ three different polymerases that each transcribe a different subset of genes. Eukaryotic mRNAs are usually monogenic, meaning that they specify a single protein. Initiation of Transcription in Eukaryotes 

Unlike the prokaryotic polymerase that can bind to a DNA template on its own, eukaryotes require several other proteins, called transcription factors, to first bind to the promoter region and then help recruit the appropriate polymerase. The Three Eukaryotic RNA Polymerases 

The features of eukaryotic mRNA synthesis are markedly more complex those of prokaryotes. Instead of a single polymerase comprising five subunits, the eukaryotes have three polymerases that are each made up of 10 subunits or more. Each eukaryotic polymerase also requires a distinct set of transcription factors to bring it to the DNA template. 

RNA polymerase I is located in the nucleolus, a specialized nuclear substructure in which ribosomal RNA (rRNA) is transcribed, processed, and assembled into ribosomes ( [link] ). The rRNA molecules are considered structural RNAs because they have a cellular role but are not translated into protein. The rRNAs are components of the ribosome and are essential to the process of translation. RNA polymerase I synthesizes all of the rRNAs except for the 5S rRNA molecule. The S designation applies to Svedberg units, a nonadditive value that characterizes the speed at which a particle sediments during centrifugation. Locations, Products, and Sensitivities of the Three Eukaryotic RNA Polymerases RNA Polymerase Cellular Compartment Product of Transcription -Amanitin Sensitivity I Nucleolus All rRNAs except 5S rRNA Insensitive II Nucleus All protein-coding nuclear pre-mRNAs Extremely sensitive III Nucleus 5S rRNA, tRNAs, and small nuclear RNAs Moderately sensitive 

RNA polymerase II is located in the nucleus and synthesizes all protein-coding nuclear pre-mRNAs. Eukaryotic pre-mRNAs undergo extensive processing after transcription but before translation. For clarity, this module s discussion of transcription and translation in eukaryotes will use the term mRNAs to describe only the mature, processed molecules that are ready to be translated. RNA polymerase II is responsible for transcribing the overwhelming majority of eukaryotic genes. 

RNA polymerase III is also located in the nucleus. This polymerase transcribes a variety of structural RNAs that includes the 5S pre-rRNA, transfer pre-RNAs (pre-tRNAs), and small nuclear pre- RNAs . The tRNAs have a critical role in translation; they serve as the adaptor molecules between the mRNA template and the growing polypeptide chain. Small nuclear RNAs have a variety of functions, including splicing pre-mRNAs and regulating transcription factors. 

A scientist characterizing a new gene can determine which polymerase transcribes it by testing whether the gene is expressed in the presence of a particular mushroom poison, -amanitin ( [link] ). Interestingly, -amanitin produced by Amanita phalloides , the Death Cap mushroom, affects the three polymerases very differently. RNA polymerase I is completely insensitive to -amanitin, meaning that the polymerase can transcribe DNA in vitro in the presence of this poison. In contrast, RNA polymerase II is extremely sensitive to -amanitin, and RNA polymerase III is moderately sensitive. Knowing the transcribing polymerase can clue a researcher into the general function of the gene being studied. Because RNA polymerase II transcribes the vast majority of genes, we will focus on this polymerase in our subsequent discussions about eukaryotic transcription factors and promoters. Structure of an RNA Polymerase II Promoter 

Eukaryotic promoters are much larger and more complex than prokaryotic promoters, but both have a TATA box. For example, in the mouse thymidine kinase gene, the TATA box is located at approximately -30 relative to the initiation (+1) site ( [link] ). For this gene, the exact TATA box sequence is TATAAAA, as read in the 5' to 3' direction on the nontemplate strand. This sequence is not identical to the E. coli TATA box, but it conserves the A T rich element. The thermostability of A T bonds is low and this helps the DNA template to locally unwind in preparation for transcription. A generalized promoter of a gene transcribed by RNA polymerase II is shown. Transcription factors recognize the promoter. RNA polymerase II then binds and forms the transcription initiation complex. 

Eukaryotic mRNA contains introns that must be spliced out. A 5' cap and 3' poly-A tail are also added. 

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The mouse genome includes one gene and two pseudogenes for cytoplasmic thymidine kinase. Pseudogenes are genes that have lost their protein-coding ability or are no longer expressed by the cell. These pseudogenes are copied from mRNA and incorporated into the chromosome. For example, the mouse thymidine kinase promoter also has a conserved CAAT box (GGCCAATCT) at approximately -80. This sequence is essential and is involved in binding transcription factors. Further upstream of the TATA box, eukaryotic promoters may also contain one or more GC-rich boxes (GGCG) or octamer boxes (ATTTGCAT). These elements bind cellular factors that increase the efficiency of transcription initiation and are often identified in more active genes that are constantly being expressed by the cell. Transcription Factors for RNA Polymerase II 

The complexity of eukaryotic transcription does not end with the polymerases and promoters. An army of basal transcription factors, enhancers, and silencers also help to regulate the frequency with which pre-mRNA is synthesized from a gene. Enhancers and silencers affect the efficiency of transcription but are not necessary for transcription to proceed. Basal transcription factors are crucial in the formation of a preinitiation complex on the DNA template that subsequently recruits RNA polymerase II for transcription initiation. 

The names of the basal transcription factors begin with TFII (this is the transcription factor for RNA polymerase II) and are specified with the letters A J. The transcription factors systematically fall into place on the DNA template, with each one further stabilizing the preinitiation complex and contributing to the recruitment of RNA polymerase II. 

The processes of bringing RNA polymerases I and III to the DNA template involve slightly less complex collections of transcription factors, but the general theme is the same. Eukaryotic transcription is a tightly regulated process that requires a variety of proteins to interact with each other and with the DNA strand. Although the process of transcription in eukaryotes involves a greater metabolic investment than in prokaryotes, it ensures that the cell transcribes precisely the pre-mRNAs that it needs for protein synthesis. 

During human embryonic development, a transcription factor encoded by the SRY gene starts a chain of events, causing the embryo to develop male sex characteristics. This gene is on the Y chromosome in humans and many other mammals. A deletion or mutation of the SRY gene can cause the human embryo to not develop into a male even though the individual has an XY genotype, a condition called Swyer syndrome. The SYR gene of the Y chromosome produces proteins that lead to the expression of primary sex characteristics, as shown. 

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The Evolution of Promoters The evolution of genes may be a familiar concept. Mutations can occur in genes during DNA replication, and the result may or may not be beneficial to the cell. By altering an enzyme, structural protein, or some other factor, the process of mutation can transform functions or physical features. However, eukaryotic promoters and other gene regulatory sequences may evolve as well. For instance, consider a gene that, over many generations, becomes more valuable to the cell. Maybe the gene encodes a structural protein that the cell needs to synthesize in abundance for a certain function. If this is the case, it would be beneficial to the cell for that gene s promoter to recruit transcription factors more efficiently and increase gene expression. 

Scientists examining the evolution of promoter sequences have reported varying results. In part, this is because it is difficult to infer exactly where a eukaryotic promoter begins and ends. Some promoters occur within genes; others are located very far upstream, or even downstream, of the genes they are regulating. However, when researchers limited their examination to human core promoter sequences that were defined experimentally as sequences that bind the preinitiation complex, they found that promoters evolve even faster than protein-coding genes. 

It is still unclear how promoter evolution might correspond to the evolution of humans or other higher organisms. However, the evolution of a promoter to effectively make more or less of a given gene product is an intriguing alternative to the evolution of the genes themselves. 1 

[link] Promoter Structures for RNA Polymerases I and III 

In eukaryotes, the conserved promoter elements differ for genes transcribed by RNA polymerases I, II, and III. RNA polymerase I transcribes genes that have two GC-rich promoter sequences in the -45 to +20 region. These sequences alone are sufficient for transcription initiation to occur, but promoters with additional sequences in the region from -180 to -105 upstream of the initiation site will further enhance initiation. Genes that are transcribed by RNA polymerase III have upstream promoters or promoters that occur within the genes themselves. Eukaryotic Elongation and Termination 

Following the formation of the preinitiation complex, the polymerase is released from the other transcription factors, and elongation is allowed to proceed as it does in prokaryotes with the polymerase synthesizing pre-mRNA in the 5' to 3' direction. As discussed previously, RNA polymerase II transcribes the major share of eukaryotic genes, so this section will focus on how this polymerase accomplishes elongation and termination. 

Although the enzymatic process of elongation is essentially the same in eukaryotes and prokaryotes, the DNA template is more complex. When eukaryotic cells are not dividing, their genes exist as a diffuse mass of DNA and proteins called chromatin. The DNA is tightly packaged around charged histone proteins at repeated intervals. These DNA histone complexes, collectively called nucleosomes, are regularly spaced and include 146 nucleotides of DNA wound around eight histones like thread around a spool. 

For polynucleotide synthesis to occur, the transcription machinery needs to move histones out of the way every time it encounters a nucleosome. This is accomplished by a special protein complex called FACT , which stands for facilitates chromatin transcription. This complex pulls histones away from the DNA template as the polymerase moves along it. Once the pre-mRNA is synthesized, the FACT complex replaces the histones to recreate the nucleosomes. 

The termination of transcription is different for the different polymerases. Unlike in prokaryotes, elongation by RNA polymerase II in eukaryotes takes place 1,000 2,000 nucleotides beyond the end of the gene being transcribed. This pre-mRNA tail is subsequently removed by cleavage during mRNA processing. On the other hand, RNA polymerases I and III require termination signals. Genes transcribed by RNA polymerase I contain a specific 18-nucleotide sequence that is recognized by a termination protein. The process of termination in RNA polymerase III involves an mRNA hairpin similar to rho-independent termination of transcription in prokaryotes. Section Summary 

Transcription in eukaryotes involves one of three types of polymerases, depending on the gene being transcribed. RNA polymerase II transcribes all of the protein-coding genes, whereas RNA polymerase I transcribes rRNA genes, and RNA polymerase III transcribes rRNA, tRNA, and small nuclear RNA genes. The initiation of transcription in eukaryotes involves the binding of several transcription factors to complex promoter sequences that are usually located upstream of the gene being copied. The mRNA is synthesized in the 5' to 3' direction, and the FACT complex moves and reassembles nucleosomes as the polymerase passes by. Whereas RNA polymerases I and III terminate transcription by protein- or RNA hairpin-dependent methods, RNA polymerase II transcribes for 1,000 or more nucleotides beyond the gene template and cleaves the excess during pre-mRNA processing. Review Questions 

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[link] Footnotes 1 H Liang et al., Fast evolution of core promoters in primate genomes, Molecular Biology and Evolution 25 (2008): 1239 44. Glossary CAAT box (GGCCAATCT) essential eukaryotic promoter sequence involved in binding transcription factors FACT complex that facilitates chromatin transcription by disassembling nucleosomes ahead of a transcribing RNA polymerase II and reassembling them after the polymerase passes by GC-rich box (GGCG) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter Octamer box (ATTTGCAT) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter preinitiation complex cluster of transcription factors and other proteins that recruit RNA polymerase II for transcription of a DNA template small nuclear RNA molecules synthesized by RNA polymerase III that have a variety of functions, including splicing pre-mRNAs and regulating transcription factorsRNA Processing in Eukaryotes RNA Processing in Eukaryotes 

In this section, you will explore the following questions: What are the steps in eukaryotic transcription? What are the structural and functional similarities and differences among the three RNA polymerases? Connection for AP Courses 

Scientists discovered a strand of mRNA translated into a sequence of amino acids (polypeptide) shorter than the mRNA molecule transcribed from DNA. Before the information in eukaryotic mRNA is translated into protein, it is modified or edited in several ways. A 5 methylguanosine (or GTP) cap and a 3 poly-A tail are added to protect mature mRNA from degradation and allow its export from the nucleus. Pre-mRNAs also undergo splicing, in which introns are removed and exons are reconnected. Exons can be reconnected in different sequences, a phenomenon referred to as alternative gene splicing, which allows a single eukaryotic gene to code for different proteins. (We will explore the significance of alternative gene splicing in more detail in other chapters.) 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Hereditable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA and, in some cases, that RNA are the primary sources of heritable information. 

Have students work in groups of 4 5 and ask them to prepare models of RNA molecules undergoing processing. Supply scissors, glue, large sheets of white paper, and colored construction paper to differentiate the components of RNA molecules, exons and introns, and the other molecules such as transcription factors and enzymes associated with the process. Emphasize the importance of the order of the steps. Ask students to specify whether these steps happen in the nucleus or in the cytoplasm. 

Ask students which mRNAs would they expect to be stable and which mRNAs should have short half-lives. Proteins that control growth and cell cycles are associated with short-lived RNAs. The globin mRNAs which encode the protein parts of hemoglobin are unusually stable. Synthesis of globin continues in red blood cells without the nucleus being present. 

Explain that introns and exons vary in number and length. Mention that not all exons will be included in the final polypeptide and that there is alternative splicing which allows cells to produce different proteins using the same gene. 

After transcription, eukaryotic pre-mRNAs must undergo several processing steps before they can be translated. Eukaryotic (and prokaryotic) tRNAs and rRNAs also undergo processing before they can function as components in the protein synthesis machinery. mRNA Processing 

The eukaryotic pre-mRNA undergoes extensive processing before it is ready to be translated. The additional steps involved in eukaryotic mRNA maturation create a molecule with a much longer half-life than a prokaryotic mRNA. Eukaryotic mRNAs last for several hours, whereas the typical E. coli mRNA lasts no more than five seconds. 

Pre-mRNAs are first coated in RNA-stabilizing proteins; these protect the pre-mRNA from degradation while it is processed and exported out of the nucleus. The three most important steps of pre-mRNA processing are the addition of stabilizing and signaling factors at the 5' and 3' ends of the molecule, and the removal of intervening sequences that do not specify the appropriate amino acids. In rare cases, the mRNA transcript can be edited after it is transcribed. 

RNA Editing in Trypanosomes The trypanosomes are a group of protozoa that include the pathogen Trypanosoma brucei , which causes sleeping sickness in humans ( [link] ). Trypanosomes, and virtually all other eukaryotes, have organelles called mitochondria that supply the cell with chemical energy. Mitochondria are organelles that express their own DNA and are believed to be the remnants of a symbiotic relationship between a eukaryote and an engulfed prokaryote. The mitochondrial DNA of trypanosomes exhibit an interesting exception to The Central Dogma: their pre-mRNAs do not have the correct information to specify a functional protein. Usually, this is because the mRNA is missing several U nucleotides. The cell performs an additional RNA processing step called RNA editing to remedy this. Trypanosoma brucei is the causative agent of sleeping sickness in humans. The mRNAs of this pathogen must be modified by the addition of nucleotides before protein synthesis can occur. (credit: modification of work by Torsten Ochsenreiter) 

Other genes in the mitochondrial genome encode 40- to 80-nucleotide guide RNAs. One or more of these molecules interacts by complementary base pairing with some of the nucleotides in the pre-mRNA transcript. However, the guide RNA has more A nucleotides than the pre-mRNA has U nucleotides to bind with. In these regions, the guide RNA loops out. The 3' ends of guide RNAs have a long poly-U tail, and these U bases are inserted in regions of the pre-mRNA transcript at which the guide RNAs are looped. This process is entirely mediated by RNA molecules. That is, guide RNAs rather than proteins serve as the catalysts in RNA editing. 

RNA editing is not just a phenomenon of trypanosomes. In the mitochondria of some plants, almost all pre-mRNAs are edited. RNA editing has also been identified in mammals such as rats, rabbits, and even humans. What could be the evolutionary reason for this additional step in pre-mRNA processing? One possibility is that the mitochondria, being remnants of ancient prokaryotes, have an equally ancient RNA-based method for regulating gene expression. In support of this hypothesis, edits made to pre-mRNAs differ depending on cellular conditions. Although speculative, the process of RNA editing may be a holdover from a primordial time when RNA molecules, instead of proteins, were responsible for catalyzing reactions. 

[link] 5' Capping 

While the pre-mRNA is still being synthesized, a 7-methylguanosine cap is added to the 5' end of the growing transcript by a phosphate linkage. This moiety (functional group) protects the nascent mRNA from degradation. In addition, factors involved in protein synthesis recognize the cap to help initiate translation by ribosomes. 3' Poly-A Tail 

Once elongation is complete, the pre-mRNA is cleaved by an endonuclease between an AAUAAA consensus sequence and a GU-rich sequence, leaving the AAUAAA sequence on the pre-mRNA. An enzyme called poly-A polymerase then adds a string of approximately 200 A residues, called the poly-A tail . This modification further protects the pre-mRNA from degradation and signals the export of the cellular factors that the transcript needs to the cytoplasm. Pre-mRNA Splicing 

Eukaryotic genes are composed of exons , which correspond to protein-coding sequences ( ex- on signifies that they are ex pressed), and int ervening sequences called introns ( int- ron denotes their int ervening role), which may be involved in gene regulation but are removed from the pre-mRNA during processing. Intron sequences in mRNA do not encode functional proteins. 

The discovery of introns came as a surprise to researchers in the 1970s who expected that pre-mRNAs would specify protein sequences without further processing, as they had observed in prokaryotes. The genes of higher eukaryotes very often contain one or more introns. These regions may correspond to regulatory sequences; however, the biological significance of having many introns or having very long introns in a gene is unclear. It is possible that introns slow down gene expression because it takes longer to transcribe pre-mRNAs with lots of introns. Alternatively, introns may be nonfunctional sequence remnants left over from the fusion of ancient genes throughout evolution. This is supported by the fact that separate exons often encode separate protein subunits or domains. For the most part, the sequences of introns can be mutated without ultimately affecting the protein product. 

All of a pre-mRNA s introns must be completely and precisely removed before protein synthesis. If the process errs by even a single nucleotide, the reading frame of the rejoined exons would shift, and the resulting protein would be dysfunctional. The process of removing introns and reconnecting exons is called splicing ( [link] ). Introns are removed and degraded while the pre-mRNA is still in the nucleus. Splicing occurs by a sequence-specific mechanism that ensures introns will be removed and exons rejoined with the accuracy and precision of a single nucleotide. The splicing of pre-mRNAs is conducted by complexes of proteins and RNA molecules called spliceosomes. 

Pre-mRNA splicing involves the precise removal of introns from the primary RNA transcript. The splicing process is catalyzed by protein complexes called spliceosomes that are composed of proteins and RNA molecules called snRNAs. Spliceosomes recognize sequences at the 5' and 3' end of the intron. 

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Note that more than 70 individual introns can be present, and each has to undergo the process of splicing in addition to 5' capping and the addition of a poly-A tail just to generate a single, translatable mRNA molecule. 

See how introns are removed during RNA splicing at this website . 

[link] Processing of tRNAs and rRNAs 

The tRNAs and rRNAs are structural molecules that have roles in protein synthesis; however, these RNAs are not themselves translated. Pre-rRNAs are transcribed, processed, and assembled into ribosomes in the nucleolus. Pre-tRNAs are transcribed and processed in the nucleus and then released into the cytoplasm where they are linked to free amino acids for protein synthesis. 

Most of the tRNAs and rRNAs in eukaryotes and prokaryotes are first transcribed as a long precursor molecule that spans multiple rRNAs or tRNAs. Enzymes then cleave the precursors into subunits corresponding to each structural RNA. Some of the bases of pre-rRNAs are methylated; that is, a CH 3 moiety (methyl functional group) is added for stability. Pre-tRNA molecules also undergo methylation. As with pre-mRNAs, subunit excision occurs in eukaryotic pre-RNAs destined to become tRNAs or rRNAs. 

Mature rRNAs make up approximately 50 percent of each ribosome. Some of a ribosome s RNA molecules are purely structural, whereas others have catalytic or binding activities. Mature tRNAs take on a three-dimensional structure through intramolecular hydrogen bonding to position the amino acid binding site at one end and the anticodon at the other end ( [link] ). The anticodon is a three-nucleotide sequence in a tRNA that interacts with an mRNA codon through complementary base pairing. This is a space-filling model of a tRNA molecule that adds the amino acid phenylalanine to a growing polypeptide chain. The anticodon AAG binds the Codon UUC on the mRNA. The amino acid phenylalanine is attached to the other end of the tRNA. Section Summary 

Eukaryotic pre-mRNAs are modified with a 5' methylguanosine cap and a poly-A tail. These structures protect the mature mRNA from degradation and help export it from the nucleus. Pre-mRNAs also undergo splicing, in which introns are removed and exons are reconnected with single-nucleotide accuracy. Only finished mRNAs that have undergone 5' capping, 3' polyadenylation, and intron splicing are exported from the nucleus to the cytoplasm. Pre-rRNAs and pre-tRNAs may be processed by intramolecular cleavage, splicing, methylation, and chemical conversion of nucleotides. Rarely, RNA editing is also performed to insert missing bases after an mRNA has been synthesized. Review Questions 

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[link] Glossary 7-methylguanosine cap modification added to the 5' end of pre-mRNAs to protect mRNA from degradation and assist translation anticodon three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon exon sequence present in protein-coding mRNA after completion of pre-mRNA splicing intron non protein-coding intervening sequences that are spliced from mRNA during processing poly-A tail modification added to the 3' end of pre-mRNAs to protect mRNA from degradation and assist mRNA export from the nucleus RNA editing direct alteration of one or more nucleotides in an mRNA that has already been synthesized splicing process of removing introns and reconnecting exons in a pre-mRNARibosomes and Protein Synthesis Ribosomes and Protein Synthesis 

In this section, you will explore the following questions: What are the different sequential steps in protein synthesis? What is the role of ribosomes in protein synthesis? Connection for AP Courses 

After the information in the gene has been transcribed to mRNA, it is ready to be translated to polypeptide. The players in translation include the mRNA template, ribosomes, tRNA molecules, amino acids, and various enzymes. Ribosomes consist of small and large subunits of protein and rRNA which bind with mRNA; many ribosomes can move along the same mRNA at a time. Translation begins at the initiating AUG on mRNA, specifying methionine, the first amino acid in any polypeptide. Each amino acid is carried to the ribosome by attaching to a specific molecule of tRNA. A tRNA molecule often is depicted as a cloverleaf, with an anticodon on one end, and the amino acid attachment site at the other. Amino-acid charging enzymes ensure that the correct amino acid is attached to the correct tRNA. The anticodons on tRNA are complementary to the codons on mRNA; for example, the anticodon AAA on tRNA corresponds to TTT on mRNA. Sequential amino acids are linked by peptide bonds. The mRNA is translated, elongating the polypeptide, until a STOP or nonsense codon is reached. When this happens, a release factor dissociates the components and frees the new polypeptide. Folding of the protein occurs during and after translation. Once a polypeptide is synthesized, its role as a protein is established, such as determining a physical phenotype of an organism. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Hereditable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 3.4 The student is able to describe representations and models illustrating how genetic information is translated into polypeptides. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.6 The student can predict how a change in a specific DNA or RNA sequence can result in changes in gene expression. 

Create models of protein synthesis with the following items: Pipe cleaners for RNA linking several units to represent mRNA and twisting some to represent tRNAs Cotton puff balls or other supplies to represent ribosomes Colored beads to represent amino acids and nucleotides 

Ask students what specific challenges must face amino-acyl tRNA synthetases. The enzymes must recognize the anticodon, the amino acid that matches that anticodon, and the tRNA acceptor site. 

Ask students to compare and contrast TATA boxes and Kozak s sequences. Both are based on consensus sequences. TATA boxes are associated with promoters and Kozak s sequences with binding of the ribosomes. 

The RNA in the ribosomes catalyze the formation of the peptide bond. This is a good example of a ribozyme, an RNA molecule that acts as an enzyme. Students may have heard that all enzymes are proteins. This is an opportunity to clarify the point. The enzyme involved in the splicing of introns is another example of RNA with catalytic properties. 

The synthesis of proteins consumes more of a cell s energy than any other metabolic process. In turn, proteins account for more mass than any other component of living organisms (with the exception of water), and proteins perform virtually every function of a cell. The process of translation, or protein synthesis, involves the decoding of an mRNA message into a polypeptide product. Amino acids are covalently strung together by interlinking peptide bonds in lengths ranging from approximately 50 amino acid residues to more than 1,000. Each individual amino acid has an amino group (NH 2 ) and a carboxyl (COOH) group. Polypeptides are formed when the amino group of one amino acid forms an amide (i.e., peptide) bond with the carboxyl group of another amino acid ( [link] ). This reaction is catalyzed by ribosomes and generates one water molecule. A peptide bond links the carboxyl end of one amino acid with the amino end of another, expelling one water molecule. For simplicity in this image, only the functional groups involved in the peptide bond are shown. The R and R' designations refer to the rest of each amino acid structure. The Protein Synthesis Machinery 

In addition to the mRNA template, many molecules and macromolecules contribute to the process of translation. The composition of each component may vary across species; for instance, ribosomes may consist of different numbers of rRNAs and polypeptides depending on the organism. However, the general structures and functions of the protein synthesis machinery are comparable from bacteria to human cells. Translation requires the input of an mRNA template, ribosomes, tRNAs, and various enzymatic factors. 

Click through the steps of this PBS interactive to see protein synthesis in action. 

[link] Ribosomes 

Even before an mRNA is translated, a cell must invest energy to build each of its ribosomes. In E. coli , there are between 10,000 and 70,000 ribosomes present in each cell at any given time. A ribosome is a complex macromolecule composed of structural and catalytic rRNAs, and many distinct polypeptides. In eukaryotes, the nucleolus is completely specialized for the synthesis and assembly of rRNAs. 

Ribosomes exist in the cytoplasm in prokaryotes and in the cytoplasm and rough endoplasmic reticulum in eukaryotes. Mitochondria and chloroplasts also have their own ribosomes in the matrix and stroma, which look more similar to prokaryotic ribosomes (and have similar drug sensitivities) than the ribosomes just outside their outer membranes in the cytoplasm. Ribosomes dissociate into large and small subunits when they are not synthesizing proteins and reassociate during the initiation of translation. In E. coli , the small subunit is described as 30S, and the large subunit is 50S, for a total of 70S (recall that Svedberg units are not additive). Mammalian ribosomes have a small 40S subunit and a large 60S subunit, for a total of 80S. The small subunit is responsible for binding the mRNA template, whereas the large subunit sequentially binds tRNAs. Each mRNA molecule is simultaneously translated by many ribosomes, all synthesizing protein in the same direction: reading the mRNA from 5' to 3' and synthesizing the polypeptide from the N terminus to the C terminus. The complete mRNA/poly-ribosome structure is called a polysome . tRNAs 

The tRNAs are structural RNA molecules that were transcribed from genes by RNA polymerase III. Depending on the species, 40 to 60 types of tRNAs exist in the cytoplasm. Serving as adaptors, specific tRNAs bind to sequences on the mRNA template and add the corresponding amino acid to the polypeptide chain. Therefore, tRNAs are the molecules that actually translate the language of RNA into the language of proteins. 

Of the 64 possible mRNA codons or triplet combinations of A, U, G, and C three specify the termination of protein synthesis and 61 specify the addition of amino acids to the polypeptide chain. Of these 61, one codon (AUG) also encodes the initiation of translation. Each tRNA anticodon can base pair with one of the mRNA codons and add an amino acid or terminate translation, according to the genetic code. For instance, if the sequence CUA occurred on an mRNA template in the proper reading frame, it would bind a tRNA expressing the complementary sequence, GAU, which would be linked to the amino acid leucine. 

As the adaptor molecules of translation, it is surprising that tRNAs can fit so much specificity into such a small package. Consider that tRNAs need to interact with three factors: 1) they must be recognized by the correct aminoacyl synthetase (see below); 2) they must be recognized by ribosomes; and 3) they must bind to the correct sequence in mRNA. Aminoacyl tRNA Synthetases 

The process of pre-tRNA synthesis by RNA polymerase III only creates the RNA portion of the adaptor molecule. The corresponding amino acid must be added later, once the tRNA is processed and exported to the cytoplasm. Through the process of tRNA charging, each tRNA molecule is linked to its correct amino acid by a group of enzymes called aminoacyl tRNA synthetases . At least one type of aminoacyl tRNA synthetase exists for each of the 20 amino acids; the exact number of aminoacyl tRNA synthetases varies by species. These enzymes first bind and hydrolyze ATP to catalyze a high-energy bond between an amino acid and adenosine monophosphate (AMP); a pyrophosphate molecule is expelled in this reaction. The activated amino acid is then transferred to the tRNA, and AMP is released. The Mechanism of Protein Synthesis 

As with mRNA synthesis, protein synthesis can be divided into three phases: initiation, elongation, and termination. The process of translation is similar in prokaryotes and eukaryotes. Here we ll explore how translation occurs in E. coli , a representative prokaryote, and specify any differences between prokaryotic and eukaryotic translation. Initiation of Translation 

Protein synthesis begins with the formation of an initiation complex. In E. coli , this complex involves the small 30S ribosome, the mRNA template, three initiation factors (IFs; IF-1, IF-2, and IF-3), and a special initiator tRNA , called t R N A f M e t t R N A f M e t . The initiator tRNA interacts with the start codon AUG (or rarely, GUG), links to a formylated methionine called fMet, and can also bind IF-2. Formylated methionine is inserted by f M e t t R N A f M e t f M e t t R N A f M e t at the beginning of every polypeptide chain synthesized by E. coli , but it is usually clipped off after translation is complete. When an in-frame AUG is encountered during translation elongation, a non-formylated methionine is inserted by a regular Met-tRNA Met . 

In E. coli mRNA, a sequence upstream of the first AUG codon, called the Shine-Dalgarno sequence (AGGAGG), interacts with the rRNA molecules that compose the ribosome. This interaction anchors the 30S ribosomal subunit at the correct location on the mRNA template. Guanosine triphosphate (GTP), which is a purine nucleotide triphosphate, acts as an energy source during translation both at the start of elongation and during the ribosome s translocation. 

In eukaryotes, a similar initiation complex forms, comprising mRNA, the 40S small ribosomal subunit, IFs, and nucleoside triphosphates (GTP and ATP). The charged initiator tRNA, called Met-tRNA i , does not bind fMet in eukaryotes, but is distinct from other Met-tRNAs in that it can bind IFs. 

Instead of depositing at the Shine-Dalgarno sequence, the eukaryotic initiation complex recognizes the 7-methylguanosine cap at the 5' end of the mRNA. A cap-binding protein (CBP) and several other IFs assist the movement of the ribosome to the 5' cap. Once at the cap, the initiation complex tracks along the mRNA in the 5' to 3' direction, searching for the AUG start codon. Many eukaryotic mRNAs are translated from the first AUG, but this is not always the case. According to Kozak s rules , the nucleotides around the AUG indicate whether it is the correct start codon. Kozak s rules state that the following consensus sequence must appear around the AUG of vertebrate genes: 5'-gccRccAUGG-3'. The R (for purine) indicates a site that can be either A or G, but cannot be C or U. Essentially, the closer the sequence is to this consensus, the higher the efficiency of translation. 

Once the appropriate AUG is identified, the other proteins and CBP dissociate, and the 60S subunit binds to the complex of Met-tRNA i , mRNA, and the 40S subunit. This step completes the initiation of translation in eukaryotes. Translation, Elongation, and Termination 

In prokaryotes and eukaryotes, the basics of elongation are the same, so we will review elongation from the perspective of E. coli . The 50S ribosomal subunit of E. coli consists of three compartments: the A (aminoacyl) site binds incoming charged aminoacyl tRNAs. The P (peptidyl) site binds charged tRNAs carrying amino acids that have formed peptide bonds with the growing polypeptide chain but have not yet dissociated from their corresponding tRNA. The E (exit) site releases dissociated tRNAs so that they can be recharged with free amino acids. There is one exception to this assembly line of tRNAs: in E. coli , f M e t t R N A f M e t f M e t t R N A f M e t is capable of entering the P site directly without first entering the A site. Similarly, the eukaryotic Met-tRNA i , with help from other proteins of the initiation complex, binds directly to the P site. In both cases, this creates an initiation complex with a free A site ready to accept the tRNA corresponding to the first codon after the AUG. 

During translation elongation, the mRNA template provides specificity. As the ribosome moves along the mRNA, each mRNA codon comes into register, and specific binding with the corresponding charged tRNA anticodon is ensured. If mRNA were not present in the elongation complex, the ribosome would bind tRNAs nonspecifically. 

Elongation proceeds with charged tRNAs entering the A site and then shifting to the P site followed by the E site with each single-codon step of the ribosome. Ribosomal steps are induced by conformational changes that advance the ribosome by three bases in the 3' direction. The energy for each step of the ribosome is donated by an elongation factor that hydrolyzes GTP. Peptide bonds form between the amino group of the amino acid attached to the A-site tRNA and the carboxyl group of the amino acid attached to the P-site tRNA. The formation of each peptide bond is catalyzed by peptidyl transferase , an RNA-based enzyme that is integrated into the 50S ribosomal subunit. The energy for each peptide bond formation is derived from GTP hydrolysis, which is catalyzed by a separate elongation factor. The amino acid bound to the P-site tRNA is also linked to the growing polypeptide chain. As the ribosome steps across the mRNA, the former P-site tRNA enters the E site, detaches from the amino acid, and is expelled ( [link] ). Amazingly, the E. coli translation apparatus takes only 0.05 seconds to add each amino acid, meaning that a 200-amino acid protein can be translated in just 10 seconds. 

Translation begins when an initiator tRNA anticodon recognizes a codon on mRNA. The large ribosomal subunit joins the small subunit, and a second tRNA is recruited. As the mRNA moves relative to the ribosome, the polypeptide chain is formed. Entry of a release factor into the A site terminates translation and the components dissociate. 

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Termination of translation occurs when a nonsense codon (UAA, UAG, or UGA) is encountered. Upon aligning with the A site, these nonsense codons are recognized by release factors in prokaryotes and eukaryotes that instruct peptidyl transferase to add a water molecule to the carboxyl end of the P-site amino acid. This reaction forces the P-site amino acid to detach from its tRNA, and the newly made protein is released. The small and large ribosomal subunits dissociate from the mRNA and from each other; they are recruited almost immediately into another translation initiation complex. After many ribosomes have completed translation, the mRNA is degraded so the nucleotides can be reused in another transcription reaction. Protein Folding, Modification, and Targeting 

During and after translation, individual amino acids may be chemically modified, signal sequences may be appended, and the new protein folds into a distinct three-dimensional structure as a result of intramolecular interactions. A signal sequence is a short tail of amino acids that directs a protein to a specific cellular compartment. These sequences at the amino end or the carboxyl end of the protein can be thought of as the protein s train ticket to its ultimate destination. Other cellular factors recognize each signal sequence and help transport the protein from the cytoplasm to its correct compartment. For instance, a specific sequence at the amino terminus will direct a protein to the mitochondria or chloroplasts (in plants). Once the protein reaches its cellular destination, the signal sequence is usually clipped off. 

Many proteins fold spontaneously, but some proteins require helper molecules, called chaperones, to prevent them from aggregating during the complicated process of folding. Even if a protein is properly specified by its corresponding mRNA, it could take on a completely dysfunctional shape if abnormal temperature or pH conditions prevent it from folding correctly. Activity Working in a small group, create a simple board game to model the key steps of transcription and translation and have classmates spend ten minutes playing the game. Provided with incomplete or incorrect diagrams illustrating transcription and translation in prokaryotes, have students refine or revise the diagrams and share the edited versions with classmates for critical review. Think About It 

Many antibiotics inhibit protein synthesis. For example, tetracycline blocks the A site on the ribosome. What is the likely effect of tetracycline on protein synthesis? Using a chart of codons, transcribe and translate the following DNA sequence (non-template strand): 5 -ATGGCCGGTTATTAAGCA-3 . How can a single nucleotide change affect the protein produced from this sequence and its function? 

The activities are applications of Learning Objective 3.4 and Science Practice 1.2 because students model how genetic information in DNA is ultimately translated into protein. 

The first question is an application of Learning Objective 3.4 and Science Practice 1.2 because students are modeling how genetic information in DNA is ultimately translated into protein. 

The second question is an application of Learning Objective 3.6 and Science Practice 6.4 because provided with a DNA sequence, students are asked to transcribe and translate the sequence and make a prediction about the possible effect of a mutation on the protein produced. Answers: Tetracycline would directly affect tRNA binding to the ribosome. The mRNA would be: 5'-AUGGCCGGUUAUUAAGCA-3'. The protein would be: MAGY (methionine-alanine-glycine-tyrosine.) Even though there are six codons, the fifth codon corresponds to a stop, so the sixth codon would not be translated. Responses to the second part of the inquiry may vary, as it would be dependent upon which nucleotide was changed. For example, if the A in the first codon (AUG) was changed to C, no protein would result. Section Summary 

The players in translation include the mRNA template, ribosomes, tRNAs, and various enzymatic factors. The small ribosomal subunit forms on the mRNA template either at the Shine-Dalgarno sequence (prokaryotes) or the 5' cap (eukaryotes). Translation begins at the initiating AUG on the mRNA, specifying methionine. The formation of peptide bonds occurs between sequential amino acids specified by the mRNA template according to the genetic code. Charged tRNAs enter the ribosomal A site, and their amino acid bonds with the amino acid at the P site. The entire mRNA is translated in three-nucleotide steps of the ribosome. When a nonsense codon is encountered, a release factor binds and dissociates the components and frees the new protein. Folding of the protein occurs during and after translation. Review Questions 

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[link] Glossary aminoacyl tRNA synthetase enzyme that charges tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid initiator tRNA in prokaryotes, called t R N A f M e t t R N A f M e t ; in eukaryotes, called tRNA i ; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain Kozak s rules determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5 -GCC( purine )CC AUG G -3 ; the bolded bases are most important peptidyl transferase RNA-based enzyme that is integrated into the 50S ribosomal subunit and catalyzes the formation of peptide bonds polysome mRNA molecule simultaneously being translated by many ribosomes all going in the same direction Shine-Dalgarno sequence (AGGAGG); initiates prokaryotic translation by interacting with rRNA molecules comprising the 30S ribosome signal sequence short tail of amino acids that directs a protein to a specific cellular compartment start codon AUG (or rarely, GUG) on an mRNA from which translation begins; always specifies methionineIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" The genetic content of each somatic cell in an organism is the same, but not all genes are expressed in every cell. The control of which genes are expressed dictates whether a cell is (a) an eye cell or (b) a liver cell. It is the differential gene expression patterns that arise in different cells that give rise to (c) a complete organism. 

Most people know that regular exercise is important to maintain good health. It promotes cardiovascular health and helps to prevent obesity. Scientists have now discovered that long-term endurance training also changes how genes are expressed in muscle tissue. In a recent study, 23 healthy people each exercised one leg for 45 minutes four days a week while resting the other leg. After three months, muscles from participants legs were biopsied, and scientists analyzed the activity level of over 20,000 genes in the tissue samples. 

They found that for each participant the exercised leg had reduced inflammation and improved metabolism compared with the non-exercised leg. These differences were accompanied by changes in genes associated with metabolism and inflammation. However, the actual nucleotide sequences of the genes weren t changed. Instead, some genes were methylated, which simply means methyl groups were attached to certain nucleotides along the sequence. This, essentially, turned the genes off or otherwise changed how they were expressed. DNA methylation is an example of epigenetics, which is a process that alters genes without affecting the nucleotide sequence of the genes. The full research article can be found here . 

Before students begin this chapter, they should review these concepts: DNA and chromatin structure, transcription, and translation.Regulation of Gene Expression Regulation of Gene Expression 

In this section, you will explore the following question: How does prokaryotic gene regulation differ from eukaryotic gene regulation? Connection for AP Courses 

Structure and function in biology result from the presence of genetic information and the correct expression of this information. In the chapter on DNA structure and function, we explored how genes are translated into proteins, which in turn determine the nature of the cell. But how does a cell know when to turn on its DNA? With few exceptions, each cell in your body contains identical genetic information. If each cell has the same exact DNA make up, how is it that a liver cell differs from a nerve or muscle cell? 

As we will discover, although each cell shares the same genome and DNA sequence, each cell does not express exactly the same genes. Many factors determine when and how genes are expressed in a given cell. Even the type of chromosome a gene is located on, like whether it is a sex chromosome or not, can determine its expression pattern, as can mutations or changes in DNA sequence and other external factors. In prokaryotes, gene expression is regulated primarily at the level of transcription, when DNA is copied into RNA. However, eukaryotes have evolved regulatory mechanisms in gene expression at multiple levels. In all cases, regulation of gene expression determines the type and amount of protein produced in the cell. Errors in regulatory processes can result in many human diseases and conditions, including cancer. 

Gene expression regulation occurs at different points in prokaryotes and eukaryotes. Prokaryotic organisms express their entire genome in every cell, but not necessarily all at the same time. In general, a gene is expressed only when its specific protein product is needed. Remember that each cell in an organism carries the same DNA as every other cell. Yet cells of eukaryotic organisms each express a unique subset of DNA depending on cell type. To express a protein, DNA is first transcribed into RNA, which is then translated into proteins. In prokaryotic cells, transcription and translation occur almost simultaneously. In eukaryotic cells, transcription occurs in the nucleus, separate from the translation that occurs in the cytoplasm along ribosomes attached to endoplasmic reticulum. As stated above, gene expression in prokaryotes is regulated at the level of transcription, whereas in eukaryotes, gene expression is regulated at multiple levels, including the epigenetic (DNA), transcriptional, pre- and post-transcriptional, and translational levels. 

The science of epigenetics studies heritable changes in the genome that do not affect the underlying DNA gene sequences. 

The content presented in this section supports the learning objectives outlined in Big Idea 3 of the AP Biology Curriculum Framework. The AP learning objectives merge essential knowledge content with one or more of the seven science practices. These objectives provide a transparent foundation for the AP Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP exam questions. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms. Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 3.18 The student is able to describe the connection between the regulation of gene expression and observed differences between different kinds of organisms. 

For a cell to function properly, necessary proteins must be synthesized at the proper time. All cells control or regulate the synthesis of proteins from information encoded in their DNA. The process of turning on a gene to produce RNA and protein is called gene expression . Whether in a simple unicellular organism or a complex multi-cellular organism, each cell controls when and how its genes are expressed. For this to occur, there must be a mechanism to control when a gene is expressed to make RNA and protein, how much of the protein is made, and when it is time to stop making that protein because it is no longer needed. 

The regulation of gene expression conserves energy and space. It would require a significant amount of energy for an organism to express every gene at all times, so it is more energy efficient to turn on the genes only when they are required. In addition, only expressing a subset of genes in each cell saves space because DNA must be unwound from its tightly coiled structure to transcribe and translate the DNA. Cells would have to be enormous if every protein were expressed in every cell all the time. 

The control of gene expression is extremely complex. Malfunctions in this process are detrimental to the cell and can lead to the development of many diseases, including cancer. 

Ask students what genes are present in the DNA in a muscle cell and skin cell. Ask them if the same genome is present in every cell in the body, how do the cells have different properties. For example, discuss red blood cells, which lose their nucleus during development. This video gives an overview of gene regulation in prokaryotes and eukaryotes. Prokaryotic versus Eukaryotic Gene Expression 

To understand how gene expression is regulated, we must first understand how a gene codes for a functional protein in a cell. The process occurs in both prokaryotic and eukaryotic cells, just in slightly different manners. 

Prokaryotic organisms are single-celled organisms that lack a cell nucleus, and their DNA therefore floats freely in the cell cytoplasm. To synthesize a protein, the processes of transcription and translation occur almost simultaneously. When the resulting protein is no longer needed, transcription stops. As a result, the primary method to control what type of protein and how much of each protein is expressed in a prokaryotic cell is the regulation of DNA transcription. All of the subsequent steps occur automatically. When more protein is required, more transcription occurs. Therefore, in prokaryotic cells, the control of gene expression is mostly at the transcriptional level. 

Eukaryotic cells, in contrast, have intracellular organelles that add to their complexity. In eukaryotic cells, the DNA is contained inside the cell s nucleus and there it is transcribed into RNA. The newly synthesized RNA is then transported out of the nucleus into the cytoplasm, where ribosomes translate the RNA into protein. The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm. The regulation of gene expression can occur at all stages of the process ( [link] ). Regulation may occur when the DNA is uncoiled and loosened from nucleosomes to bind transcription factors ( epigenetic level), when the RNA is transcribed (transcriptional level), when the RNA is processed and exported to the cytoplasm after it is transcribed ( post-transcriptional level), when the RNA is translated into protein (translational level), or after the protein has been made ( post-translational level). Prokaryotic transcription and translation occur simultaneously in the cytoplasm, and regulation occurs at the transcriptional level. Eukaryotic gene expression is regulated during transcription and RNA processing, which take place in the nucleus, and during protein translation, which takes place in the cytoplasm. Further regulation may occur through post-translational modifications of proteins. 

The differences in the regulation of gene expression between prokaryotes and eukaryotes are summarized in [link] . The regulation of gene expression is discussed in detail in subsequent modules. Differences in the Regulation of Gene Expression of Prokaryotic and Eukaryotic Organisms Prokaryotic organisms Eukaryotic organisms Lack nucleus Contain nucleus DNA is found in the cytoplasm DNA is confined to the nuclear compartment RNA transcription and protein formation occur almost simultaneously RNA transcription occurs prior to protein formation, and it takes place in the nucleus. Translation of RNA to protein occurs in the cytoplasm. Gene expression is regulated primarily at the transcriptional level Gene expression is regulated at many levels (epigenetic, transcriptional, nuclear shuttling, post-transcriptional, translational, and post-translational) Evolution of Gene Regulation 

Prokaryotic cells can only regulate gene expression by controlling the amount of transcription. As eukaryotic cells evolved, the complexity of the control of gene expression increased. For example, with the evolution of eukaryotic cells came compartmentalization of important cellular components and cellular processes. A nuclear region that contains the DNA was formed. Transcription and translation were physically separated into two different cellular compartments. It therefore became possible to control gene expression by regulating transcription in the nucleus, and also by controlling the RNA levels and protein translation present outside the nucleus. 

Some cellular processes arose from the need of the organism to defend itself. Cellular processes such as gene silencing developed to protect the cell from viral or parasitic infections. If the cell could quickly shut off gene expression for a short period of time, it would be able to survive an infection when other organisms could not. Therefore, the organism evolved a new process that helped it survive, and it was able to pass this new development to offspring. 

[link] Think About It 

How does controlling gene expression alter the overall protein level in the cell? 

The question is an application of Learning Objective 3.18 and Science Practice 7.1 because students are asked to describe the connection between genes, gene expression (i.e., transcription and translation), and how the production of different proteins can result in cell specialization and differences between organisms. Answer 

The cell controls which proteins are expressed and to what level each protein is expressed in the cell. Prokaryotic cells alter the transcription rate to turn genes on or off. This method will increase or decrease protein levels in response to what is needed by the cell. Eukaryotic cells change the accessibility (through epigenetic mechanisms), transcription, or translation of a gene. This will alter the amount of RNA and the lifespan of the RNA to alter the amount of protein that exists. Eukaryotic organisms are much more complex and can manipulate protein levels by changing many stages in the process. Section Summary 

While all somatic cells within an organism contain the same DNA, not all cells within that organism express the same proteins. Prokaryotic organisms express the entire DNA they encode in every cell, but not necessarily all at the same time. Proteins are expressed only when they are needed. Eukaryotic organisms express a subset of the DNA that is encoded in any given cell. In each cell type, the type and amount of protein is regulated by controlling gene expression. To express a protein, the DNA is first transcribed into RNA, which is then translated into proteins. In prokaryotic cells, these processes occur almost simultaneously. In eukaryotic cells, transcription occurs in the nucleus and is separate from the translation that occurs in the cytoplasm. Gene expression in prokaryotes is regulated only at the transcriptional level, whereas in eukaryotic cells, gene expression is regulated at the epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels. Review Questions 

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[link] Critical Thinking Questions 

[link] Test Prep for AP Courses 

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[link] Glossary epigenetic heritable changes that do not involve changes in the DNA sequence gene expression processes that control the turning on or turning off of a gene post-transcriptional control of gene expression after the RNA molecule has been created but before it is translated into protein post-translational control of gene expression after a protein has been createdProkaryotic Gene Regulation Prokaryotic Gene Regulation 

In this section, you will explore the following question: What are operons and what are the roles of activators, inducers, and repressors in regulating operons and gene expression? Connection for AP Courses 

The regulation of gene expression in prokaryotic cells occurs at the transcriptional level. Simply stated, if a cell does not transcribe the DNA s message into mRNA, translation (protein synthesis), does not occur. Bacterial genes are often organized into common pathways or processes called operons for more coordinated regulation of expression. For example, in E. coli , genes responsible for lactose metabolism are located together on the bacterial chromosome. (The operon model includes several components, so when studying how the operon works, it is helpful to refer to a diagram of the model. See [link] and [link] .) The operon includes a regulatory gene that codes for a repressor protein that binds to the operator, which prevents RNA polymerase from transcribing the gene(s) of interest. An example of this is seen in the structural genes for lactose metabolism. However, if the repressor is inactivated, RNA polymerase binds to the promoter, and transcription of the structural genes occurs. 

There are three ways to control the transcription of an operon: inducible control, repressible control, and activator control. The lac operon is an example of inducible control because the presence of lactose turns on transcription of the genes for its own metabolism. The trp operon is an example of repressible control because it uses proteins bound to the operator sequence to physically prevent the binding of RNA polymerase. If tryptophan is not needed by the cell, the genes necessary to produce it are turned off. Activator control (typified by the action of Catabolite Activator Protein) increases the binding ability of RNA polymerase to the promoter. Certain genes are continually expressed via this regulatory mechanism. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms. Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively Learning Objective 3.21 The student can use representations to describe how gene regulation influences cell products and function. Essential Knowledge 3.B.2 A variety of intercellular and intracellular signal transmissions mediate gene expression. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 3.23 The student can use representations to describe mechanisms of the regulation of gene expression. 

When discussing the operons with students, challenge them to think about what would happen if there were a gene mutation that disrupted the function of one of the proteins that controls transcription of the operon. For example, if the repressor protein in the lac operon has a mutation that prevents it from binding to lactose, then the repressor will remain bound to the operator and will prevent transcription of the operon even in the presence of lactose. This video describes two other examples of mutations in the lac operon. 

Introduce the regulation of transcription in the lac operon using visuals such as this video . 

The DNA of prokaryotes is organized into a circular chromosome supercoiled in the nucleoid region of the cell cytoplasm. Proteins that are needed for a specific function, or that are involved in the same biochemical pathway, are encoded together in blocks called operons . For example, all of the genes needed to use lactose as an energy source are coded next to each other in the lactose (or lac ) operon. 

In prokaryotic cells, there are three types of regulatory molecules that can affect the expression of operons: repressors, activators, and inducers. Repressors are proteins that suppress transcription of a gene in response to an external stimulus, whereas activators are proteins that increase the transcription of a gene in response to an external stimulus. Finally, inducers are small molecules that either activate or repress transcription depending on the needs of the cell and the availability of substrate. The trp Operon: A Repressor Operon 

Bacteria such as E. coli need amino acids to survive. Tryptophan is one such amino acid that E. coli can ingest from the environment. E. coli can also synthesize tryptophan using enzymes that are encoded by five genes. These five genes are next to each other in what is called the tryptophan ( trp ) operon ( [link] ). If tryptophan is present in the environment, then E. coli does not need to synthesize it and the switch controlling the activation of the genes in the trp operon is switched off. However, when tryptophan availability is low, the switch controlling the operon is turned on, transcription is initiated, the genes are expressed, and tryptophan is synthesized. The five genes that are needed to synthesize tryptophan in E. coli are located next to each other in the trp operon. When tryptophan is plentiful, two tryptophan molecules bind the repressor protein at the operator sequence. This physically blocks the RNA polymerase from transcribing the tryptophan genes. When tryptophan is absent, the repressor protein does not bind to the operator and the genes are transcribed. 

A DNA sequence that codes for proteins is referred to as the coding region. The five coding regions for the tryptophan biosynthesis enzymes are arranged sequentially on the chromosome in the operon. Just before the coding region is the transcriptional start site . This is the region of DNA to which RNA polymerase binds to initiate transcription. The promoter sequence is upstream of the transcriptional start site; each operon has a sequence within or near the promoter to which proteins (activators or repressors) can bind and regulate transcription. 

A DNA sequence called the operator sequence is encoded between the promoter region and the first trp coding gene. This operator contains the DNA code to which the repressor protein can bind. When tryptophan is present in the cell, two tryptophan molecules bind to the trp repressor, which changes shape to bind to the trp operator. Binding of the tryptophan repressor complex at the operator physically prevents the RNA polymerase from binding, and transcribing the downstream genes. 

When tryptophan is not present in the cell, the repressor by itself does not bind to the operator; therefore, the operon is active and tryptophan is synthesized. Because the repressor protein actively binds to the operator to keep the genes turned off, the trp operon is negatively regulated and the proteins that bind to the operator to silence trp expression are negative regulators . Link to Learning 

Watch this video to learn more about the trp operon. 

[link] Catabolite Activator Protein (CAP): An Activator Regulator 

Just as the trp operon is negatively regulated by tryptophan molecules, there are proteins that bind to the operator sequences that act as a positive regulator to turn genes on and activate them. For example, when glucose is scarce, E. coli bacteria can turn to other sugar sources for fuel. To do this, new genes to process these alternate genes must be transcribed. When glucose levels drop, cyclic AMP (cAMP) begins to accumulate in the cell. The cAMP molecule is a signaling molecule that is involved in glucose and energy metabolism in E. coli . When glucose levels decline in the cell, accumulating cAMP binds to the positive regulator catabolite activator protein (CAP) , a protein that binds to the promoters of operons that control the processing of alternative sugars. When cAMP binds to CAP, the complex binds to the promoter region of the genes that are needed to use the alternate sugar sources ( [link] ). In these operons, a CAP binding site is located upstream of the RNA polymerase binding site in the promoter. This increases the binding ability of RNA polymerase to the promoter region and the transcription of the genes. When glucose levels fall, E. coli may use other sugars for fuel but must transcribe new genes to do so. As glucose supplies become limited, cAMP levels increase. This cAMP binds to the CAP protein, a positive regulator that binds to an operator region upstream of the genes required to use other sugar sources. The lac Operon: An Inducer Operon 

The third type of gene regulation in prokaryotic cells occurs through inducible operons , which have proteins that bind to activate or repress transcription depending on the local environment and the needs of the cell. The lac operon is a typical inducible operon. As mentioned previously, E. coli is able to use other sugars as energy sources when glucose concentrations are low. To do so, the cAMP CAP protein complex serves as a positive regulator to induce transcription. One such sugar source is lactose. The lac operon encodes the genes necessary to acquire and process the lactose from the local environment. CAP binds to the operator sequence upstream of the promoter that initiates transcription of the lac operon. However, for the lac operon to be activated, two conditions must be met. First, the level of glucose must be very low or non-existent. Second, lactose must be present. Only when glucose is absent and lactose is present will the lac operon be transcribed ( [link] ). This makes sense for the cell, because it would be energetically wasteful to create the proteins to process lactose if glucose was plentiful or lactose was not available. 

Transcription of the lac operon is carefully regulated so that its expression only occurs when glucose is limited and lactose is present to serve as an alternative fuel source. 

[link] 

If glucose is absent, then CAP can bind to the operator sequence to activate transcription. If lactose is absent, then the repressor binds to the operator to prevent transcription. If either of these requirements is met, then transcription remains off. Only when both conditions are satisfied is the lac operon transcribed ( [link] ). Signals that Induce or Repress Transcription of the lac Operon Glucose CAP binds Lactose Repressor binds Transcription + - - + No + - + - Some - + - + No - + + - Yes 

Watch an animated tutorial about the workings of lac operon here. 

[link] Activity 

Modeling the Operon. Use construction paper or more elaborate materials, such as Styrofoam noodles, electrical tape, and Velcro tabs, to create a model of the lac and trp operons that include a regulator, promoter, operator, and structural genes. Then use the model to show how the presence of substrate, e.g., allolactose or tryptophan, can change the activity of the operons. As an extension of the activity, use the model to make predictions about the effects of mutations in any of the regions on gene expression. Think About It 

In E. coli , the trp operon is on by default, while the lac operon is off by default. Why do you think this is the case? 

The activity is an application of Learning Objectives 3.21 and 3.23 and Science Practice 1.4 because students are using a representation to describe how operons regulate gene expression in prokaryotes. In addition, students are applying Science Practice 6.4 because they will use the model to make predictions about gene regulation and expression. 

The question is an application of Learning Objectives 3.2 and 3.23 and Science Practice 1.4 because students are using the operon model of gene regulation in prokaryotes to describe an observed phenomenon. Answer 

Tryptophan is an amino acid necessary for making proteins, so the cell always needs to have some on hand. However, if plenty of tryptophan is present, it is wasteful to make more, and the expression of the trp genes is repressed. Lactose, a sugar found in milk, is not always available. Cells need not make the enzymes necessary to digest an energy source that is not available, so the lac operon is only turned on when lactose is present. Section Summary 

The regulation of gene expression in prokaryotic cells occurs at the transcriptional level. There are three ways to control the transcription of an operon: repressive control, activator control, and inducible control. Repressive control, typified by the trp operon, uses proteins bound to the operator sequence to physically prevent the binding of RNA polymerase and the activation of transcription. Therefore, if tryptophan is not needed, the repressor is bound to the operator and transcription remains off. Activator control, typified by the action of CAP, increases the binding ability of RNA polymerase to the promoter when CAP is bound. In this case, low levels of glucose result in the binding of cAMP to CAP. CAP then binds the promoter, which allows RNA polymerase to bind to the promoter better. In the last example the lac operon two conditions must be met to initiate transcription. Glucose must not be present, and lactose must be available for the lac operon to be transcribed. If glucose is absent, CAP binds to the operator. If lactose is present, the repressor protein does not bind to its operator. Only when both conditions are met will RNA polymerase bind to the promoter to induce transcription. Review Questions 

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[link] Critical Thinking Questions 

[link] Test Prep for AP Courses 

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[link] Glossary activator protein that binds to prokaryotic operators to increase transcription catabolite activator protein (CAP) protein that complexes with cAMP to bind to the promoter sequences of operons that control sugar processing when glucose is not available inducible operon operon that can be activated or repressed depending on cellular needs and the surrounding environment lac operon operon in prokaryotic cells that encodes genes required for processing and intake of lactose negative regulator protein that prevents transcription operator region of DNA outside of the promoter region that binds activators or repressors that control gene expression in prokaryotic cells operon collection of genes involved in a pathway that are transcribed together as a single mRNA in prokaryotic cells positive regulator protein that increases transcription repressor protein that binds to the operator of prokaryotic genes to prevent transcription transcriptional start site site at which transcription begins trp operon series of genes necessary to synthesize tryptophan in prokaryotic cells tryptophan amino acid that can be synthesized by prokaryotic cells when necessaryEukaryotic Epigenetic Gene Regulation Eukaryotic Epigenetic Gene Regulation 

In this section, you will explore the following question: What is the science of epigenetics and how is this process regulated? Connection for AP Courses 

One reason that eukaryotic gene expression is more complex than prokaryotic gene expression is because the processes of transcription and translation are physically separated within the eukaryotic cell. Eukaryotic cells also package their genomes in a more sophisticated way compared with prokaryotic cells. Consequently, eukaryotic cells can regulate gene expression at multiple levels, beginning with control of access to DNA. Because genomic DNA is folded around histone proteins to create nucleosome complexes, nucleosomes physically regulate the access of proteins, such as transcription factors and enzymes, to the underlying DNA. Methylation of DNA and histones causes nucleosomes to pack tightly together, preventing transcription factors from binding to the DNA. Methylated nucleosomes contain DNA that is not expressed. On the other hand, histone acetylation results in loose packing of nucleosomes, allowing transcription factors to bind to DNA. Acetylated nucleosomes contain DNA that may be expressed. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms. Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales Learning Objective 3.19 The student is able to describe the connection between the regulation of gene expression and observed differences between individuals in a population Epigenetic Control: Regulating Access to Genes within the Chromosome 

As stated earlier, one reason why eukaryotic gene expression is more complex than prokaryotic gene expression is because the processes of transcription and translation are physically separated. Unlike prokaryotic cells, eukaryotic cells can regulate gene expression at many different levels. Eukaryotic gene expression begins with control of access to the DNA. This form of regulation, called epigenetic regulation, occurs even before transcription is initiated. 

Introduce epigenetics and have students work on an epigenetics activity found on the University of Utah s website . 

The human genome encodes over 20,000 genes; each of the 23 pairs of human chromosomes encodes thousands of genes. The DNA in the nucleus is precisely wound, folded, and compacted into chromosomes so that it will fit into the nucleus. It is also organized so that specific segments can be accessed as needed by a specific cell type. 

The first level of organization, or packing, is the winding of DNA strands around histone proteins. Histones package and order DNA into structural units called nucleosome complexes, which can control the access of proteins to the DNA regions ( [link] a ). Under the electron microscope, this winding of DNA around histone proteins to form nucleosomes looks like small beads on a string ( [link] b ). These beads (histone proteins) can move along the string (DNA) and change the structure of the molecule. DNA is folded around histone proteins to create (a) nucleosome complexes. These nucleosomes control the access of proteins to the underlying DNA. When viewed through an electron microscope (b), the nucleosomes look like beads on a string. (credit micrograph : modification of work by Chris Woodcock) 

If DNA encoding a specific gene is to be transcribed into RNA, the nucleosomes surrounding that region of DNA can slide down the DNA to open that specific chromosomal region and allow for the transcriptional machinery (RNA polymerase) to initiate transcription ( [link] ). Nucleosomes can move to open the chromosome structure to expose a segment of DNA, but do so in a very controlled manner. 

Nucleosomes can slide along DNA. When nucleosomes are spaced closely together (top), transcription factors cannot bind and gene expression is turned off. When the nucleosomes are spaced far apart (bottom), the DNA is exposed. Transcription factors can bind, allowing gene expression to occur. Modifications to the histones and DNA affect nucleosome spacing. 

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How the histone proteins move is dependent on signals found on both the histone proteins and on the DNA. These signals are tags added to histone proteins and DNA that tell the histones if a chromosomal region should be open or closed ( [link] depicts modifications to histone proteins and DNA). These tags are not permanent, but may be added or removed as needed. They are chemical modifications (phosphate, methyl, or acetyl groups) that are attached to specific amino acids in the protein or to the nucleotides of the DNA. The tags do not alter the DNA base sequence, but they do alter how tightly wound the DNA is around the histone proteins. DNA is a negatively charged molecule; therefore, changes in the charge of the histone will change how tightly wound the DNA molecule will be. When unmodified, the histone proteins have a large positive charge; by adding chemical modifications like acetyl groups, the charge becomes less positive. 

The DNA molecule itself can also be modified. This occurs within very specific regions called CpG islands. These are stretches with a high frequency of cytosine and guanine dinucleotide DNA pairs (CG) found in the promoter regions of genes. When this configuration exists, the cytosine member of the pair can be methylated (a methyl group is added). This modification changes how the DNA interacts with proteins, including the histone proteins that control access to the region. Highly methylated (hypermethylated) DNA regions with deacetylated histones are tightly coiled and transcriptionally inactive. Histone proteins and DNA nucleotides can be modified chemically. Modifications affect nucleosome spacing and gene expression. (credit: modification of work by NIH) 

This type of gene regulation is called epigenetic regulation. Epigenetic means around genetics. The changes that occur to the histone proteins and DNA do not alter the nucleotide sequence and are not permanent. Instead, these changes are temporary (although they often persist through multiple rounds of cell division) and alter the chromosomal structure (open or closed) as needed. A gene can be turned on or off depending upon the location and modifications to the histone proteins and DNA. If a gene is to be transcribed, the histone proteins and DNA are modified surrounding the chromosomal region encoding that gene. This opens the chromosomal region to allow access for RNA polymerase and other proteins, called transcription factors , to bind to the promoter region, located just upstream of the gene, and initiate transcription. If a gene is to remain turned off, or silenced, the histone proteins and DNA have different modifications that signal a closed chromosomal configuration. In this closed configuration, the RNA polymerase and transcription factors do not have access to the DNA and transcription cannot occur ( [link] ). Think About It 

In females, one of the two X chromosomes is inactivated during embryonic development because of epigenetic changes to the chromatin. What impact do you think these changes will have on nucleosome packaging and, consequently, gene expression? 

The question is an application of Learning Objective 3.19 and Science Practice 7.1 because students are asked to describe how epigenetic changes to chromatin during development can result in differential gene expression and, consequently, differences among cells and organisms. Answer: The nucleosomes will pack more tightly together. 

View this video that describes how epigenetic regulation controls gene expression. 

[link] Section Summary 

In eukaryotic cells, the first stage of gene expression control occurs at the epigenetic level. Epigenetic mechanisms control access to the chromosomal region to allow genes to be turned on or off. These mechanisms control how DNA is packed into the nucleus by regulating how tightly the DNA is wound around histone proteins. The addition or removal of chemical modifications (or flags) to histone proteins or DNA signals to the cell to open or close a chromosomal region. Therefore, eukaryotic cells can control whether a gene is expressed by controlling accessibility to transcription factors and the binding of RNA polymerase to initiate transcription. Review Questions 

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[link] Critical Thinking Questions 

[link] Glossary transcription factor protein that binds to the DNA at the promoter or enhancer region and that influences transcription of a geneEukaryotic Transcription Gene Regulation Eukaryotic Transcription Gene Regulation 

In this section, you will explore the following question: What is the role of transcription factors, enhancers, and repressors in gene regulation? Connection for AP Courses 

To start transcription, general transcription factors must first bind to a specific area on the DNA called the TATA box and then recruit RNA polymerase to that location. In addition, other areas on the DNA called enhancer regions help augment transcription. Transcription factors can bind to enhancer regions to increase or prevent transcription. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms. Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 3.18 The student is able to describe the connection between the regulation of gene expression and observed differences between different kinds of organisms Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales Learning Objective 3.19 The student is able to describe the connection between the regulation of gene expression and observed differences between individuals in a population Essential Knowledge 3.B.1 Gene regulation results in differential gene expression, leading to cell specialization. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices Learning Objective 3.20 The student is able to explain how the regulation of gene expression is essential for the processes and structures that support efficient cell function. Essential Knowledge 3.B.1 1 Gene regulation results in differential gene expression, leading to cell specialization. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 3.21 The student can use representations to describe how gene regulation influences cell products and function. 

Have students create a visual representation using colored paper that shows DNA transcription and the role of enhancers and repressors in transcription. 

Like prokaryotic cells, the transcription of genes in eukaryotes requires the actions of an RNA polymerase to bind to a sequence upstream of a gene to initiate transcription. However, unlike prokaryotic cells, the eukaryotic RNA polymerase requires other proteins, or transcription factors, to facilitate transcription initiation. Transcription factors are proteins that bind to the promoter sequence and other regulatory sequences to control the transcription of the target gene. RNA polymerase by itself cannot initiate transcription in eukaryotic cells. Transcription factors must bind to the promoter region first and recruit RNA polymerase to the site for transcription to be established. 

View the process of transcription the making of RNA from a DNA template at this site . 

[link] The Promoter and the Transcription Machinery 

Genes are organized to make the control of gene expression easier. The promoter region is immediately upstream of the coding sequence. This region can be short (only a few nucleotides in length) or quite long (hundreds of nucleotides long). The longer the promoter, the more available space for proteins to bind. This also adds more control to the transcription process. The length of the promoter is gene-specific and can differ dramatically between genes. Consequently, the level of control of gene expression can also differ quite dramatically between genes. The purpose of the promoter is to bind transcription factors that control the initiation of transcription. 

Within the promoter region, just upstream of the transcriptional start site, resides the TATA box. This box is simply a repeat of thymine and adenine dinucleotides (literally, TATA repeats). RNA polymerase binds to the transcription initiation complex, allowing transcription to occur. To initiate transcription, a transcription factor (TFIID) is the first to bind to the TATA box. Binding of TFIID recruits other transcription factors, including TFIIB, TFIIE, TFIIF, and TFIIH to the TATA box. Once this complex is assembled, RNA polymerase can bind to its upstream sequence. When bound along with the transcription factors, RNA polymerase is phosphorylated. This releases part of the protein from the DNA to activate the transcription initiation complex and places RNA polymerase in the correct orientation to begin transcription; DNA-bending protein brings the enhancer, which can be quite a distance from the gene, in contact with transcription factors and mediator proteins ( [link] ). An enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors. Two different genes may have the same promoter but different distal control elements, enabling differential gene expression. 

In addition to the general transcription factors, other transcription factors can bind to the promoter to regulate gene transcription. These transcription factors bind to the promoters of a specific set of genes. They are not general transcription factors that bind to every promoter complex, but are recruited to a specific sequence on the promoter of a specific gene. There are hundreds of transcription factors in a cell that each bind specifically to a particular DNA sequence motif. When transcription factors bind to the promoter just upstream of the encoded gene, it is referred to as a cis -acting element , because it is on the same chromosome just next to the gene. The region that a particular transcription factor binds to is called the transcription factor binding site . Transcription factors respond to environmental stimuli that cause the proteins to find their binding sites and initiate transcription of the gene that is needed. Enhancers and Transcription 

In some eukaryotic genes, there are regions that help increase or enhance transcription. These regions, called enhancers , are not necessarily close to the genes they enhance. They can be located upstream of a gene, within the coding region of the gene, downstream of a gene, or may be thousands of nucleotides away. 

Enhancer regions are binding sequences, or sites, for transcription factors. When a DNA-bending protein binds, the shape of the DNA changes ( [link] ). This shape change allows for the interaction of the activators bound to the enhancers with the transcription factors bound to the promoter region and the RNA polymerase. Whereas DNA is generally depicted as a straight line in two dimensions, it is actually a three-dimensional object. Therefore, a nucleotide sequence thousands of nucleotides away can fold over and interact with a specific promoter. Turning Genes Off: Transcriptional Repressors 

Like prokaryotic cells, eukaryotic cells also have mechanisms to prevent transcription. Transcriptional repressors can bind to promoter or enhancer regions and block transcription. Like the transcriptional activators, repressors respond to external stimuli to prevent the binding of activating transcription factors. Think About It 

How can cells in a multicellular eukaryotic organism be of different types given that they all share the same genome? 

The question is an application of Learning Objective 3.18 and Science Practice 7.1 and Learning Objective 3.21 and Science Practice 1.4 because students are asked to explain how the regulation of gene expression with the same genome influences cell morphology, function, and products (i.e., cell differentiation/specialization). Answer: Even though the genome within each cell of an organism is the same, when and whether those genes are expressed is controlled by many factors, including transcription factors, enhancers, repressors, and environmental stimuli. This results in different genes being expressed in different cells and allows cells to differentiate and specialize. Section Summary 

To start transcription, general transcription factors, such as TFIID, TFIIH, and others, must first bind to the TATA box and recruit RNA polymerase to that location. The binding of additional regulatory transcription factors to cis -acting elements will either increase or prevent transcription. In addition to promoter sequences, enhancer regions help augment transcription. Enhancers can be upstream, downstream, within a gene itself, or on other chromosomes. Transcription factors bind to enhancer regions to increase or prevent transcription. Review Questions 

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[link] Critical Thinking Questions 

[link] Test Prep for AP Courses 

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[link] Glossary cis -acting element transcription factor binding sites within the promoter that regulate the transcription of a gene adjacent to it enhancer segment of DNA that is upstream, downstream, perhaps thousands of nucleotides away, or on another chromosome that influence the transcription of a specific gene trans -acting element transcription factor binding site found outside the promoter or on another chromosome that influences the transcription of a particular gene transcription factor binding site sequence of DNA to which a transcription factor bindsEukaryotic Post-transcriptional Gene Regulation Eukaryotic Post-transcriptional Gene Regulation 

In this section, you will explore the following question: How is gene expression controlled through post-transcriptional modifications of RNA molecules? Connection for AP Courses 

Post-transcriptional regulation can occur at any stage after transcription. One important post-transcriptional mechanism is RNA splicing. After RNA is transcribed, it is often modified to create a mature RNA that is ready to be translated. As we studied in previous chapters, processing messenger RNA involves the removal of introns that do not code for protein. Spliceosomes remove the introns and ligate the exons together, often in different sequences than their original order on the newly transcribed (immature) messenger RNA. A GTP cap is added to the 5 -end and a poly-A tail is added to the 3 -end. This mature messenger RNA then leaves the nucleus and enters the cytoplasm. Once in the cytoplasm, the length of time the messenger RNA resides there before being degraded a characteristic lifespan or shelf-life of the molecule called RNA stability can be altered to control the amount of protein that is synthesized. RNA stability is controlled by several factors, including microRNAs (miRNA or RNAi, RNA interference); miRNAs always decrease stability and promote decay of messenger RNA. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.5 The student can evaluate alternative scientific explanations. Learning Objective 3.1 The student is able to construct scientific explanations that use the structures and mechanisms of DNA and RNA to support the claim that DNA and, in some cases, RNA are the primary source of heritable information. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.6 The student can predict how a change in a specific DNA or RNA sequence can result in changes in gene expression. 

Introduce mRNA modifications using videos such as this one about 5'caps and 3'poly-A tails. 

Students may not realize that splicing occurs with variation, not all introns are excised in exactly the same way all of the time. Differential splicing produces different protein products. This one introduces RNA splicing. 

RNA is transcribed, but must be processed into a mature form before translation can begin. This processing after an RNA molecule has been transcribed, but before it is translated into a protein, is called post-transcriptional modification. As with the epigenetic and transcriptional stages of processing, this post-transcriptional step can also be regulated to control gene expression in the cell. If the RNA is not processed, shuttled, or translated, then no protein will be synthesized. RNA Splicing, the First Stage of Post-transcriptional Control 

In eukaryotic cells, the RNA transcript often contains regions, called introns, that are removed prior to translation. The regions of RNA that code for protein are called exons ( [link] ). After an RNA molecule has been transcribed, but prior to its departure from the nucleus to be translated, the RNA is processed and the introns are removed by splicing. Pre-mRNA can be alternatively spliced to create different proteins. Alternative RNA Splicing 

In the 1970s, genes were first observed that exhibited alternative RNA splicing. Alternative RNA splicing is a mechanism that allows different protein products to be produced from one gene when different combinations of introns, and sometimes exons, are removed from the transcript ( [link] ). This alternative splicing can be haphazard, but more often it is controlled and acts as a mechanism of gene regulation, with the frequency of different splicing alternatives controlled by the cell as a way to control the production of different protein products in different cells or at different stages of development. Alternative splicing is now understood to be a common mechanism of gene regulation in eukaryotes; according to one estimate, 70 percent of genes in humans are expressed as multiple proteins through alternative splicing. There are five basic modes of alternative splicing. 

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Visualize how mRNA splicing happens by watching the process in action in this video . 

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What is an evolutionary advantage of alternative gene splicing of introns during post-transcriptional modification of mRNA? 

The question is an application of Learning Objective 3.1 and Science Practice 6.5 and Learning Objective 3.6 and Science Practice 6.4 because students are asked to explain how alternative spicing, i.e., the rearranging on introns following transcription, affects the product(s) produced and why this splicing provides evolutionary advantage(s). Answer: Alternative splicing has many advantages including higher efficiency, because one DNA sequence (one gene) can code for a number of different proteins. It also allows for evolutionary flexibility: different protein isoforms with different functions can be formed through alternative splicing. Control of RNA Stability 

Before the mRNA leaves the nucleus, it is given two protective "caps" that prevent the end of the strand from degrading during its journey. The 5' cap , which is placed on the 5' end of the mRNA, is usually composed of a methylated guanosine triphosphate molecule (GTP). The poly-A tail , which is attached to the 3' end, is usually composed of a series of adenine nucleotides. Once the RNA is transported to the cytoplasm, the length of time that the RNA resides there can be controlled. Each RNA molecule has a defined lifespan and decays at a specific rate. This rate of decay can influence how much protein is in the cell. If the decay rate is increased, the RNA will not exist in the cytoplasm as long, shortening the time for translation to occur. Conversely, if the rate of decay is decreased, the RNA molecule will reside in the cytoplasm longer and more protein can be translated. This rate of decay is referred to as the RNA stability. If the RNA is stable, it will be detected for longer periods of time in the cytoplasm. 

Binding of proteins to the RNA can influence its stability. Proteins, called RNA-binding proteins , or RBPs, can bind to the regions of the RNA just upstream or downstream of the protein-coding region. These regions in the RNA that are not translated into protein are called the untranslated regions , or UTRs. They are not introns (those have been removed in the nucleus). Rather, these are regions that regulate mRNA localization, stability, and protein translation. The region just before the protein-coding region is called the 5' UTR , whereas the region after the coding region is called the 3' UTR ( [link] ). The binding of RBPs to these regions can increase or decrease the stability of an RNA molecule, depending on the specific RBP that binds. The protein-coding region of mRNA is flanked by 5' and 3' untranslated regions (UTRs). The presence of RNA-binding proteins at the 5' or 3' UTR influences the stability of the RNA molecule. RNA Stability and microRNAs 

In addition to RBPs that bind to and control (increase or decrease) RNA stability, other elements called microRNAs can bind to the RNA molecule. These microRNAs , or miRNAs, are short RNA molecules that are only 21 24 nucleotides in length. The miRNAs are made in the nucleus as longer pre-miRNAs. These pre-miRNAs are chopped into mature miRNAs by a protein called dicer . Like transcription factors and RBPs, mature miRNAs recognize a specific sequence and bind to the RNA; however, miRNAs also associate with a ribonucleoprotein complex called the RNA-induced silencing complex (RISC) . RISC binds along with the miRNA to degrade the target mRNA. Together, miRNAs and the RISC complex rapidly destroy the RNA molecule. Section Summary 

Post-transcriptional control can occur at any stage after transcription, including RNA splicing, nuclear shuttling, and RNA stability. Once RNA is transcribed, it must be processed to create a mature RNA that is ready to be translated. This involves the removal of introns that do not code for protein. Spliceosomes bind to the signals that mark the exon/intron border to remove the introns and ligate the exons together. Once this occurs, the RNA is mature and can be translated. RNA is created and spliced in the nucleus, but needs to be transported to the cytoplasm to be translated. RNA is transported to the cytoplasm through the nuclear pore complex. Once the RNA is in the cytoplasm, the length of time it resides there before being degraded, called RNA stability, can also be altered to control the overall amount of protein that is synthesized. The RNA stability can be increased, leading to longer residency time in the cytoplasm, or decreased, leading to shortened time and less protein synthesis. RNA stability is controlled by RNA-binding proteins (RPBs) and microRNAs (miRNAs). These RPBs and miRNAs bind to the 5' UTR or the 3' UTR of the RNA to increase or decrease RNA stability. Depending on the RBP, the stability can be increased or decreased significantly; however, miRNAs always decrease stability and promote decay. Review Questions 

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[link] Glossary 3' UTR 3' untranslated region; region just downstream of the protein-coding region in an RNA molecule that is not translated 5' cap a methylated guanosine triphosphate (GTP) molecule that is attached to the 5' end of a messenger RNA to protect the end from degradation 5' UTR 5' untranslated region; region just upstream of the protein-coding region in an RNA molecule that is not translated dicer enzyme that chops the pre-miRNA into the mature form of the miRNA microRNA (miRNA) small RNA molecules (approximately 21 nucleotides in length) that bind to RNA molecules to degrade them poly-A tail a series of adenine nucleotides that are attached to the 3' end of an mRNA to protect the end from degradation RNA-binding protein (RBP) protein that binds to the 3' or 5' UTR to increase or decrease the RNA stability RNA stability how long an RNA molecule will remain intact in the cytoplasm untranslated region segment of the RNA molecule that are not translated into protein. These regions lie before (upstream or 5') and after (downstream or 3') the protein-coding region RISC protein complex that binds along with the miRNA to the RNA to degrade itEukaryotic Translational and Post-translational Gene Regulation Eukaryotic Translational and Post-translational Gene Regulation 

In this section, you will explore the following question: What are different ways in which translational and post-translational control of gene expression take place? Connection for AP Courses 

Changing the status of the RNA or the protein itself can affect the amount of protein produced, the function of the protein, or how long the protein resides in the cell. Modifications such as phosphorylation and environmental stimuli can affect the stability and function of the protein. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 4 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 4 Biological systems interact, and these systems and their interactions possess complex properties. 

Enduring Understanding 4.A Interactions within biological systems lead to complex properties. Essential Knowledge 4.A.3 Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs. Science Practice 1.3 The student can refine representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 4.7 The student is able to refine representations to illustrate how interactions between external stimuli and gene expression result in specialization of cells, tissues, and organs. 

Introduce the topic of post-translation gene regulation using visuals such as this video . 

After the RNA has been transported to the cytoplasm, it is translated into protein. Control of this process is largely dependent on the RNA molecule. As previously discussed, the stability of the RNA will have a large impact on its translation into a protein. As the stability changes, the amount of time that it is available for translation also changes. The Initiation Complex and Translation Rate 

Like transcription, translation is controlled by proteins that bind and initiate the process. In translation, the complex that assembles to start the process is referred to as the initiation complex . The first protein to bind to the RNA to initiate translation is the eukaryotic initiation factor-2 (eIF-2) . The eIF-2 protein is active when it binds to the high-energy molecule guanosine triphosphate (GTP) . GTP provides the energy to start the reaction by giving up a phosphate and becoming guanosine diphosphate (GDP) . The eIF-2 protein bound to GTP binds to the small 40S ribosomal subunit . When bound, the methionine initiator tRNA associates with the eIF-2/40S ribosome complex, bringing along with it the mRNA to be translated. At this point, when the initiator complex is assembled, the GTP is converted into GDP and energy is released. The phosphate and the eIF-2 protein are released from the complex and the large 60S ribosomal subunit binds to translate the RNA. The binding of eIF-2 to the RNA is controlled by phosphorylation. If eIF-2 is phosphorylated, it undergoes a conformational change and cannot bind to GTP. Therefore, the initiation complex cannot form properly and translation is impeded ( [link] ). When eIF-2 remains unphosphorylated, it binds the RNA and actively translates the protein. 

Gene expression can be controlled by factors that bind the translation initiation complex. 

[link] Chemical Modifications, Protein Activity, and Longevity 

Proteins can be chemically modified with the addition of groups including methyl, phosphate, acetyl, and ubiquitin groups. The addition or removal of these groups from proteins regulates their activity or the length of time they exist in the cell. Sometimes these modifications can regulate where a protein is found in the cell for example, in the nucleus, the cytoplasm, or attached to the plasma membrane. 

Chemical modifications occur in response to external stimuli such as stress, the lack of nutrients, heat, or ultraviolet light exposure. These changes can alter epigenetic accessibility, transcription, mRNA stability, or translation all resulting in changes in expression of various genes. This is an efficient way for the cell to rapidly change the levels of specific proteins in response to the environment. Because proteins are involved in every stage of gene regulation, the phosphorylation of a protein (depending on the protein that is modified) can alter accessibility to the chromosome, can alter translation (by altering transcription factor binding or function), can change nuclear shuttling (by influencing modifications to the nuclear pore complex), can alter RNA stability (by binding or not binding to the RNA to regulate its stability), can modify translation (increase or decrease), or can change post-translational modifications (add or remove phosphates or other chemical modifications). 

The addition of an ubiquitin group to a protein marks that protein for degradation. Ubiquitin acts like a flag indicating that the protein lifespan is complete. These proteins are moved to the proteasome , an organelle that functions to remove proteins, to be degraded ( [link] ). One way to control gene expression, therefore, is to alter the longevity of the protein. Proteins with ubiquitin tags are marked for degradation within the proteasome. Think About It 

How can environmental stimuli such as ultraviolet light exposure or nutrient deficiency modify gene expression? 

This question is an application of Learning Objective 4.7 and Science Practice 1.3 because, based on the student s knowledge of transcription and translation, the student is describing the means of translational control of gene expression. Answer: Proteins can be chemically modified with the addition of functional groups including methyl, phosphate, acetyl, and ubiquitin groups. The addition or removal of these groups from proteins regulates the protein activity or the length of time the proteins exist in the cell. Sometimes these modifications can regulate where a protein is found in the cell: in the nucleus or cytoplasm or attached to the plasma membrane, for example. Chemical modifications occur in response to external stimuli such as stressors including the lack of nutrients, increases in temperature, or exposure to ultraviolet light. These changes can alter epigenetic accessibility, transcription, mRNA stability, or translation all resulting in changes in expression of various genes. Section Summary 

Changing the status of the RNA or the protein itself can affect the amount of protein, the function of the protein, or how long it is found in the cell. To translate the protein, a protein initiator complex must assemble on the RNA. Modifications (such as phosphorylation) of proteins in this complex can prevent proper translation from occurring. Once a protein has been synthesized, it can be modified (phosphorylated, acetylated, methylated, or ubiquitinated). These post-translational modifications can greatly impact the stability, degradation, or function of the protein. Review Questions 

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[link] Glossary eukaryotic initiation factor-2 (eIF-2) protein that binds first to an mRNA to initiate translation guanine diphosphate (GDP) molecule that is left after the energy is used to start translation guanine triphosphate (GTP) energy-providing molecule that binds to eIF-2 and is needed for translation initiation complex protein complex containing eIF2-2 that starts translation large 60S ribosomal subunit second, larger ribosomal subunit that binds to the RNA to translate it into protein proteasome organelle that degrades proteins small 40S ribosomal subunit ribosomal subunit that binds to the RNA to translate it into proteinCancer and Gene Regulation Cancer and Gene Regulation 

In this section, you will explore the following questions: How can changes in gene expression cause cancer? How can changes to gene expression at different levels disrupt the cell cycle? Connection for AP Courses 

Cancer is a disease of altered gene expression that can occur at every level of control, including at the levels of DNA methylation, histone acetylation, and activation of transcription factors. By understanding how each stage of gene regulation works in normal cells, we can understand what goes wrong in diseased states. For example, changes in the activity of the tumor suppressor gene p53 can result in cancer. Phosphorylation and other protein modifications have also been implicated in cancer. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The learning objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms. Essential Knowledge 3.B.2 A variety of intercellular and intracellular signal transmissions mediate gene expression. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.22 The student is able to explain how signal pathways mediate gene expression, including how this process can affect protein production. Essential Knowledge 3.B.2 A variety of intercellular and intracellular signal transmissions mediate gene expression. Science Practice 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Learning Objective 3.23 The student can use representations to describe mechanisms of the regulation of gene expression. 

The normal role of the p53 protein is to arrest the cell cycle or to initiate apoptosis in response to stimuli such as DNA damage. 

Introduce the topic of cancer and gene regulation using visuals such as this video . 

Cancer is not a single disease but includes many different diseases. In cancer cells, mutations modify cell-cycle control and cells don t stop growing as they normally would. Mutations can also alter the growth rate or the progression of the cell through the cell cycle. One example of a gene modification that alters the growth rate is increased phosphorylation of cyclin B, a protein that controls the progression of a cell through the cell cycle and serves as a cell-cycle checkpoint protein. 

For cells to move through each phase of the cell cycle, the cell must pass through checkpoints. This ensures that the cell has properly completed the step and has not encountered any mutation that will alter its function. Many proteins, including cyclin B, control these checkpoints. The phosphorylation of cyclin B, a post-translational event, alters its function. As a result, cells can progress through the cell cycle unimpeded, even if mutations exist in the cell and its growth should be terminated. This post-translational change of cyclin B prevents it from controlling the cell cycle and contributes to the development of cancer. Cancer: Disease of Altered Gene Expression 

Cancer can be described as a disease of altered gene expression. There are many proteins that are turned on or off (gene activation or gene silencing) that dramatically alter the overall activity of the cell. A gene that is not normally expressed in that cell can be switched on and expressed at high levels. This can be the result of gene mutation or changes in gene regulation (epigenetic, transcription, post-transcription, translation, or post-translation). 

Changes in epigenetic regulation, transcription, RNA stability, protein translation, and post-translational control can be detected in cancer. While these changes don t occur simultaneously in one cancer, changes at each of these levels can be detected when observing cancer at different sites in different individuals. Therefore, changes in histone acetylation (epigenetic modification that leads to gene silencing), activation of transcription factors by phosphorylation, increased RNA stability, increased translational control, and protein modification can all be detected at some point in various cancer cells. Scientists are working to understand the common changes that give rise to certain types of cancer or how a modification might be exploited to destroy a tumor cell. Tumor Suppressor Genes, Oncogenes, and Cancer 

In normal cells, some genes function to prevent excess, inappropriate cell growth. These are tumor suppressor genes, which are active in normal cells to prevent uncontrolled cell growth. There are many tumor suppressor genes in cells. The most studied tumor suppressor gene is p53, which is mutated in over 50 percent of all cancer types. The p53 protein itself functions as a transcription factor. It can bind to sites in the promoters of genes to initiate transcription. Therefore, the mutation of p53 in cancer will dramatically alter the transcriptional activity of its target genes. 

Watch this animation to learn more about the use of p53 in fighting cancer. 

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Proto-oncogenes are positive cell-cycle regulators. When mutated, proto-oncogenes can become oncogenes and cause cancer. Overexpression of the oncogene can lead to uncontrolled cell growth. This is because oncogenes can alter transcriptional activity, stability, or protein translation of another gene that directly or indirectly controls cell growth. An example of an oncogene involved in cancer is a protein called myc. Myc is a transcription factor that is aberrantly activated in Burkett s Lymphoma, a cancer of the lymph system. Overexpression of myc transforms normal B cells into cancerous cells that continue to grow uncontrollably. High B-cell numbers can result in tumors that can interfere with normal bodily function. Patients with Burkett s lymphoma can develop tumors on their jaw or in their mouth that interfere with the ability to eat. Cancer and Epigenetic Alterations 

Silencing genes through epigenetic mechanisms is also very common in cancer cells. There are characteristic modifications to histone proteins and DNA that are associated with silenced genes. In cancer cells, the DNA in the promoter region of silenced genes is methylated on cytosine DNA residues in CpG islands. Histone proteins that surround that region lack the acetylation modification that is present when the genes are expressed in normal cells. This combination of DNA methylation and histone deacetylation (epigenetic modifications that lead to gene silencing) is commonly found in cancer. When these modifications occur, the gene present in that chromosomal region is silenced. Increasingly, scientists understand how epigenetic changes are altered in cancer. Because these changes are temporary and can be reversed for example, by preventing the action of the histone deacetylase protein that removes acetyl groups, or by DNA methyl transferase enzymes that add methyl groups to cytosines in DNA it is possible to design new drugs and new therapies to take advantage of the reversible nature of these processes. Indeed, many researchers are testing how a silenced gene can be switched back on in a cancer cell to help re-establish normal growth patterns. 

Genes involved in the development of many other illnesses, ranging from allergies to inflammation to autism, are thought to be regulated by epigenetic mechanisms. As our knowledge of how genes are controlled deepens, new ways to treat diseases like cancer will emerge. Cancer and Transcriptional Control 

Alterations in cells that give rise to cancer can affect the transcriptional control of gene expression. Mutations that activate transcription factors, such as increased phosphorylation, can increase the binding of a transcription factor to its binding site in a promoter. This could lead to increased transcriptional activation of that gene that results in modified cell growth. Alternatively, a mutation in the DNA of a promoter or enhancer region can increase the binding ability of a transcription factor. This could also lead to the increased transcription and aberrant gene expression that is seen in cancer cells. 

Researchers have been investigating how to control the transcriptional activation of gene expression in cancer. Identifying how a transcription factor binds, or a pathway that activates where a gene can be turned off, has led to new drugs and new ways to treat cancer. In breast cancer, for example, many proteins are overexpressed. This can lead to increased phosphorylation of key transcription factors that increase transcription. One such example is the overexpression of the epidermal growth factor receptor (EGFR) in a subset of breast cancers. The EGFR pathway activates many protein kinases that, in turn, activate many transcription factors that control genes involved in cell growth. New drugs that prevent the activation of EGFR have been developed and are used to treat these cancers. Cancer and Post-transcriptional Control 

Changes in the post-transcriptional control of a gene can also result in cancer. Recently, several groups of researchers have shown that specific cancers have altered expression of miRNAs. Because miRNAs bind to the 3' UTR of RNA molecules to degrade them, overexpression of these miRNAs could be detrimental to normal cellular activity. Too many miRNAs could dramatically decrease the RNA population leading to a decrease in protein expression. Several studies have demonstrated a change in the miRNA population in specific cancer types. It appears that the subset of miRNAs expressed in breast cancer cells is quite different from the subset expressed in lung cancer cells or even from normal breast cells. This suggests that alterations in miRNA activity can contribute to the growth of breast cancer cells. These types of studies also suggest that if some miRNAs are specifically expressed only in cancer cells, they could be potential drug targets. It would, therefore, be conceivable that new drugs that turn off miRNA expression in cancer could be an effective method to treat cancer. Cancer and Translational/Post-translational Control 

There are many examples of how translational or post-translational modifications of proteins arise in cancer. Modifications are found in cancer cells from the increased translation of a protein to changes in protein phosphorylation to alternative splice variants of a protein. An example of how the expression of an alternative form of a protein can have dramatically different outcomes is seen in colon cancer cells. The c-Flip protein, a protein involved in mediating the cell death pathway, comes in two forms: long (c-FLIPL) and short (c-FLIPS). Both forms appear to be involved in initiating controlled cell death mechanisms in normal cells. However, in colon cancer cells, expression of the long form results in increased cell growth instead of cell death. Clearly, the expression of the wrong protein dramatically alters cell function and contributes to the development of cancer. New Drugs to Combat Cancer: Targeted Therapies 

Scientists are using what is known about the regulation of gene expression in disease states, including cancer, to develop new ways to treat and prevent disease development. Many scientists are designing drugs on the basis of the gene expression patterns within individual tumors. This idea, that therapy and medicines can be tailored to an individual, has given rise to the field of personalized medicine. With an increased understanding of gene regulation and gene function, medicines can be designed to specifically target diseased cells without harming healthy cells. Some new medicines, called targeted therapies, have exploited the overexpression of a specific protein or the mutation of a gene to develop a new medication to treat disease. One such example is the use of anti-EGF receptor medications to treat the subset of breast cancer tumors that have very high levels of the EGF protein. Undoubtedly, more targeted therapies will be developed as scientists learn more about how gene expression changes can cause cancer. Clinical Trial Coordinator 

A clinical trial coordinator is the person managing the proceedings of the clinical trial. This job includes coordinating patient schedules and appointments, maintaining detailed notes, building the database to track patients (especially for long-term follow-up studies), ensuring proper documentation has been acquired and accepted, and working with the nurses and doctors to facilitate the trial and publication of the results. A clinical trial coordinator may have a science background, like a nursing degree, or other certification. People who have worked in science labs or in clinical offices are also qualified to become a clinical trial coordinator. These jobs are generally in hospitals; however, some clinics and doctor s offices also conduct clinical trials and may hire a coordinator. Think About It 

New drugs are being developed that decrease DNA methylation and prevent the removal of acetyl groups from histone proteins. Explain how these drugs could affect gene expression to help kill tumor cells. 

How can understanding the gene expression in a cancer cell tell you something about that specific form of cancer? 

The first question is an application of Learning Objective 3.22 and Science Practice 6.2 because students are asked to explain how altered gene expression can result in cancer and how drugs that target problems in signaling pathways can treat cancer. 

The second question is an application of Learning Objective 3.22 and Science Practice 6.2 and Learning Objective 3.23 and Science Practice 1.4 because students are explaining the connection between alterations in signaling pathways and alterations in gene expression, and how these changes can result in cancer. Answers: 

These drugs will keep the histone proteins and the DNA methylation patterns in the open chromosomal configuration so that transcription is feasible. If a gene is silenced in the cancer cell, these drugs could reverse the epigenetic configuration to re-express the gene. 

Understanding which genes are expressed in a cancer cell can help diagnose the specific form of cancer. It can also help identify treatment options for that patient. For example, if a breast cancer tumor expresses the epidermal growth factor receptor (EGFR) in high numbers, it might respond to specific anti-EGFR therapy. If this receptor is not expressed, then this cancer will not respond to anti-EGFR therapy. Section Summary 

Cancer can be described as a disease of altered gene expression. Changes at every level of eukaryotic gene expression can be detected in some form of cancer at some point in time. In order to understand how changes to gene expression can cause cancer, it is critical to understand how each stage of gene regulation works in normal cells. By understanding the mechanisms of control in normal, non-diseased cells, it will be easier for scientists to understand what goes wrong in disease states including complex ones like cancer. Review Questions 

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[link] Glossary DNA methylation epigenetic modification that leads to gene silencing; commonly found in cancer cells histone acetylation epigenetic modification that leads to gene silencing; commonly found in cancer cells found in cancer cells myc oncogene that causes cancer in many cancer cellsIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" In genomics, the DNA of different organisms is compared, enabling scientists to create maps with which to navigate the DNA of different organisms. (credit "map": modification of photo by NASA) 

Some of the greatest accomplishments of biotechnology are in the fields of medicine and medical research. For example, intestinal failure due to missing or abnormal intestinal tissue is a frequent problem in premature babies. Intestinal problems are also common for people who have had parts of their small intestines removed for reasons , such as Crohn s Disease, cancer, and blockages. Complications from intestinal failure may include liver disease, bacterial overgrowth, dehydration, and malnutrition. 

Scientists have recently developed a way to engineer human intestines from human cells using mice. Using a mixture of healthy mouse and human intestinal cells and placing it on scaffolding in the abdominal cavity of immunocompromised mice, functional human intestinal cells grow within four weeks. This could be the breakthrough needed to help patients suffering from intestinal failure. More details about this exciting research can be found here . 

This chapter gives the instructor the opportunity to explore the developments in the areas of biotechnology and genomics for both the good and detriment of individuals and society. The newest developments will have exceeded the scope of this text and will need to be supplemented during the course.Biotechnology Biotechnology 

In this section, you will explore the following questions: What are examples of basic techniques used to manipulate genetic material (DNA and RNA)? What is the difference between molecular and reproductive cloning? What are examples of uses of biotechnology in medicine and agriculture? Connection for AP Courses 

Did you eat cereal for breakfast or tomatoes in your dinner salad? Do you know someone who has received gene therapy to treat a disease such as cancer? Should your school, health insurance provider, or employer have access to your genetic profile? Understanding how DNA works has allowed scientists to recombine DNA molecules, clone organisms, and produce mice that glow in the dark. We likely have eaten genetically modified foods and are familiar with how DNA analysis is used to solve crimes. Manipulation of DNA by humans has resulted in bacteria that can protect plants from insect pests and restore ecosystems. Biotechnologies also have been used to produce insulin, hormones, antibiotics, and medicine that dissolve blood clots. Comparative genomics yields new insights into relationships among species, and DNA sequences reveal our personal genetic make-up. However, manipulation of DNA comes with social and ethical responsibilities, raising questions about its appropriate uses. 

Nucleic acids can be isolated from cells for analysis by lysing cell membranes and enzymatically destroying all other macromolecules. Fragmented or whole chromosomes can be separated on the basis of size (base pair length) by gel electrophoresis. Short sequences of DNA or RNA can be amplified using the polymerase chain reaction (PCR). Recombinant DNA technology can combine DNA from different sources using bacterial plasmids or viruses as vectors to carry foreign genes into host cells, resulting in genetically modified organisms (GMOs). Transgenic bacteria, agricultural plants such as corn and rice, and farm animals produce protein products such as hormones and vaccines that benefit humans. (It is important to remind ourselves that recombinant technology is possible because the genetic code is universal, and the processes of transcription and translation are fundamentally the same in all organisms.) Cloning produces genetically identical copies of DNA, cells, or even entire organisms (reproductive cloning). Genetic testing identifies disease-causing genes, and gene therapy can be used to treat or cure an inheritable disease. However, questions emerge from these technologies including the safety of GMOs and privacy issues. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.5 The student can justify the claim that humans can manipulate heritable information by identifying an example of a commonly used technology. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.C.1 Changes in genotype can result in changes in phenotype. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. 

Begin the discussion with the ethical considerations, such as genetic modified foods, the availability of a genome to the government or insurance provider, or modifying a genome for therapy or the sex selection with embryos. These topics will be in the minds of students, so get them out in front and then get into the mechanics of the topic. 

Basic Techniques to Manipulate Genetic Material (DNA and RNA) Go through the process of DNA extraction in class as a demonstration. This would probably be the first time the students would have an opportunity to actually see DNA. Bring in a gel from gel electrophoresis and the results of Southern Blotting as illustrations of the techniques. This will help the discussion be a little more concrete. Be sure that students understand the different uses of the word clone, such as molecular cloning, cellular cloning, reproductive cloning. Emphasize that the word is neutral and does not automatically infer a negative process. Earlier discussions of the ethics of the subject should help to put it into context. 

Biotechnology is the use of biological agents for technological advancement. Biotechnology was used for breeding livestock and crops long before the scientific basis of these techniques was understood. Since the discovery of the structure of DNA in 1953, the field of biotechnology has grown rapidly through both academic research and private companies. The primary applications of this technology are in medicine (production of vaccines and antibiotics) and agriculture (genetic modification of crops, such as to increase yields). Biotechnology also has many industrial applications, such as fermentation, the treatment of oil spills, and the production of biofuels ( [link] ). Antibiotics are chemicals produced by fungi, bacteria, and other organisms that have antimicrobial properties. The first antibiotic discovered was penicillin. Antibiotics are now commercially produced and tested for their potential to inhibit bacterial growth. (credit "advertisement": modification of work by NIH; credit "test plate": modification of work by Don Stalons/CDC; scale-bar data from Matt Russell) Basic Techniques to Manipulate Genetic Material (DNA and RNA) 

To understand the basic techniques used to work with nucleic acids, remember that nucleic acids are macromolecules made of nucleotides (a sugar, a phosphate, and a nitrogenous base) linked by phosphodiester bonds. The phosphate groups on these molecules each have a net negative charge. An entire set of DNA molecules in the nucleus is called the genome. DNA has two complementary strands linked by hydrogen bonds between the paired bases. The two strands can be separated by exposure to high temperatures (DNA denaturation) and can be reannealed by cooling. The DNA can be replicated by the DNA polymerase enzyme. Unlike DNA, which is located in the nucleus of eukaryotic cells, RNA molecules leave the nucleus. The most common type of RNA that is analyzed is the messenger RNA (mRNA) because it represents the protein-coding genes that are actively expressed. However, RNA molecules present some other challenges to analysis, as they are often less stable than DNA. DNA and RNA Extraction 

To study or manipulate nucleic acids, the DNA or RNA must first be isolated or extracted from the cells. Various techniques are used to extract different types of DNA ( [link] ). Most nucleic acid extraction techniques involve steps to break open the cell and use enzymatic reactions to destroy all macromolecules that are not desired (such as degradation of unwanted molecules and separation from the DNA sample). Cells are broken using a lysis buffer (a solution which is mostly a detergent); lysis means to split. These enzymes break apart lipid molecules in the cell membranes and nuclear membranes. Macromolecules are inactivated using enzymes such as proteases that break down proteins, and ribonucleases (RNAses) that break down RNA. The DNA is then precipitated using alcohol. Human genomic DNA is usually visible as a gelatinous, white mass. The DNA samples can be stored frozen at 80 C for several years. This diagram shows the basic method used for extraction of DNA. 

RNA analysis is performed to study gene expression patterns in cells. RNA is naturally very unstable because RNAses are commonly present in nature and very difficult to inactivate. Similar to DNA, RNA extraction involves the use of various buffers and enzymes to inactivate macromolecules and preserve the RNA. Gel Electrophoresis 

Because nucleic acids are negatively charged ions at neutral or basic pH in an aqueous environment, they can be mobilized by an electric field. Gel electrophoresis is a technique used to separate molecules on the basis of size, using this charge. The nucleic acids can be separated as whole chromosomes or fragments. The nucleic acids are loaded into a slot near the negative electrode of a semisolid, porous gel matrix and pulled toward the positive electrode at the opposite end of the gel. Smaller molecules move through the pores in the gel faster than larger molecules; this difference in the rate of migration separates the fragments on the basis of size. There are molecular weight standard samples that can be run alongside the molecules to provide a size comparison. Nucleic acids in a gel matrix can be observed using various fluorescent or colored dyes. Distinct nucleic acid fragments appear as bands at specific distances from the top of the gel (the negative electrode end) on the basis of their size ( [link] ). A mixture of genomic DNA fragments of varying sizes appear as a long smear, whereas uncut genomic DNA is usually too large to run through the gel and forms a single large band at the top of the gel. Shown are DNA fragments from seven samples run on a gel, stained with a fluorescent dye, and viewed under UV light. (credit: James Jacob, Tompkins Cortland Community College) Amplification of Nucleic Acid Fragments by Polymerase Chain Reaction 

Although genomic DNA is visible to the naked eye when it is extracted in bulk, DNA analysis often requires focusing on one or more specific regions of the genome. Polymerase chain reaction ( PCR ) is a technique used to amplify specific regions of DNA for further analysis ( [link] ). PCR is used for many purposes in laboratories, such as the cloning of gene fragments to analyze genetic diseases, identification of contaminant foreign DNA in a sample, and the amplification of DNA for sequencing. More practical applications include the determination of paternity and detection of genetic diseases. Polymerase chain reaction, or PCR, is used to amplify a specific sequence of DNA. Primers short pieces of DNA complementary to each end of the target sequence are combined with genomic DNA, Taq polymerase, and deoxynucleotides. Taq polymerase is a DNA polymerase isolated from the thermostable bacterium Thermus aquaticus that is able to withstand the high temperatures used in PCR. Thermus aquaticus grows in the Lower Geyser Basin of Yellowstone National Park. Reverse transcriptase PCR (RT-PCR) is similar to PCR, but cDNA is made from an RNA template before PCR begins. 

DNA fragments can also be amplified from an RNA template in a process called reverse transcriptase PCR (RT-PCR) . The first step is to recreate the original DNA template strand (called cDNA) by applying DNA nucleotides to the mRNA. This process is called reverse transcription. This requires the presence of an enzyme called reverse transcriptase. After the cDNA is made, regular PCR can be used to amplify it. 

Deepen your understanding of the polymerase chain reaction by clicking through this interactive exercise . 

[link] Hybridization, Southern Blotting, and Northern Blotting 

Nucleic acid samples, such as fragmented genomic DNA and RNA extracts, can be probed for the presence of certain sequences. Short DNA fragments called probes are designed and labeled with radioactive or fluorescent dyes to aid detection. Gel electrophoresis separates the nucleic acid fragments according to their size. The fragments in the gel are then transferred onto a nylon membrane in a procedure called blotting ( [link] ). The nucleic acid fragments that are bound to the surface of the membrane can then be probed with specific radioactively or fluorescently labeled probe sequences. When DNA is transferred to a nylon membrane, the technique is called Southern blotting , and when RNA is transferred to a nylon membrane, it is called northern blotting . Southern blots are used to detect the presence of certain DNA sequences in a given genome, and northern blots are used to detect gene expression. Southern blotting is used to find a particular sequence in a sample of DNA. DNA fragments are separated on a gel, transferred to a nylon membrane, and incubated with a DNA probe complementary to the sequence of interest. Northern blotting is similar to Southern blotting, but RNA is run on the gel instead of DNA. In western blotting, proteins are run on a gel and detected using antibodies. Molecular Cloning 

In general, the word cloning means the creation of a perfect replica; however, in biology, the re-creation of a whole organism is referred to as reproductive cloning. Long before attempts were made to clone an entire organism, researchers learned how to reproduce desired regions or fragments of the genome, a process that is referred to as molecular cloning. 

Cloning small fragments of the genome allows for the manipulation and study of specific genes (and their protein products), or noncoding regions in isolation. A plasmid (also called a vector) is a small circular DNA molecule that replicates independently of the chromosomal DNA. In cloning, the plasmid molecules can be used to provide a "folder" in which to insert a desired DNA fragment. Plasmids are usually introduced into a bacterial host for proliferation. In the bacterial context, the fragment of DNA from the human genome (or the genome of another organism that is being studied) is referred to as foreign DNA , or a transgene, to differentiate it from the DNA of the bacterium, which is called the host DNA . 

Plasmids occur naturally in bacterial populations (such as Escherichia coli ) and have genes that can contribute favorable traits to the organism, such as antibiotic resistance (the ability to be unaffected by antibiotics). Plasmids have been repurposed and engineered as vectors for molecular cloning and the large-scale production of important reagents, such as insulin and human growth hormone. An important feature of plasmid vectors is the ease with which a foreign DNA fragment can be introduced via the multiple cloning site (MCS) . The MCS is a short DNA sequence containing multiple sites that can be cut with different commonly available restriction endonucleases. Restriction endonucleases recognize specific DNA sequences and cut them in a predictable manner; they are naturally produced by bacteria as a defense mechanism against foreign DNA. Many restriction endonucleases make staggered cuts in the two strands of DNA, such that the cut ends have a 2- or 4-base single-stranded overhang. Because these overhangs are capable of annealing with complementary overhangs, these are called sticky ends. Addition of an enzyme called DNA ligase permanently joins the DNA fragments via phosphodiester bonds. In this way, any DNA fragment generated by restriction endonuclease cleavage can be spliced between the two ends of a plasmid DNA that has been cut with the same restriction endonuclease ( [link] ). Recombinant DNA Molecules 

Plasmids with foreign DNA inserted into them are called recombinant DNA molecules because they are created artificially and do not occur in nature. They are also called chimeric molecules because the origin of different parts of the molecules can be traced back to different species of biological organisms or even to chemical synthesis. Proteins that are expressed from recombinant DNA molecules are called recombinant proteins . Not all recombinant plasmids are capable of expressing genes. The recombinant DNA may need to be moved into a different vector (or host) that is better designed for gene expression. Plasmids may also be engineered to express proteins only when stimulated by certain environmental factors, so that scientists can control the expression of the recombinant proteins. 

This diagram shows the steps involved in molecular cloning. 

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View an animation of recombination in cloning from the DNA Learning Center. 

[link] Activity 

Cloning can be used to quickly replicate crop plants that have advantageous genes, such as greater disease resistance or greater fruit production. However, cloning also produces crop plants that have little genetic variation. In a group, discuss the advantages and disadvantages of using clones as human food sources in an era where the Earth is undergoing a period of climate change. How well will cloned populations of crop plants be able to adapt to climate change, compared to non-clone crop plants? Then, defend your group s position against those of other groups in a classroom debate. Think About It 

How would a scientist introduce a gene for herbicide resistance into a plant, such as corn? 

Suggested group size for the activity is 3 6 students. Guide student groups to think about climate change as a natural selection pressure that will affect the success of the clones. By using crop plants with little genetic variation, there is little potential that these plants to withstand an environmental change such as rapid, human-induced global warming. 

The activity is an application of Learning Objective 3.5 and Science Practice 6.4 because students are discussing the justification for cloning crop plants and then predicting how climate change will act as a selection pressure on the clones. 

The Think About It question is an application of Learning Objective 3.5 and Science Practice 6.4 because the technique for introducing new genes into an organism is an example of how heritable information can be manipulated. 

An expanded lab investigation for biotechnology, involving performing a genetic transformation on E. coli , is available from the College Board s AP Biology Investigative Labs: An Inquiry-Based Approach in Investigation 8 . Answer: Alter a plant RNA virus to contain the gene for herbicide resistance. Use the virus as a vector to place the gene into appropriate plants. 

Genetic engineering is as old as farming. Discuss the efforts that were made by farmers to develop better crops before technology gave its assistance. Discuss how technology has increased the changes in crops worldwide. What is the evidence for possible benefits and possible hazards of the development of genetically modified crops (GMO s)? Cellular Cloning 

Unicellular organisms, such as bacteria and yeast, naturally produce clones of themselves when they replicate asexually by binary fission; this is known as cellular cloning . The nuclear DNA duplicates by the process of mitosis, which creates an exact replica of the genetic material. Reproductive Cloning 

Reproductive cloning is a method used to make a clone or an identical copy of an entire multicellular organism. Most multicellular organisms undergo reproduction by sexual means, which involves genetic hybridization of two individuals (parents), making it impossible for generation of an identical copy or a clone of either parent. Recent advances in biotechnology have made it possible to artificially induce asexual reproduction of mammals in the laboratory. 

Parthenogenesis, or virgin birth, occurs when an embryo grows and develops without the fertilization of the egg occurring; this is a form of asexual reproduction. An example of parthenogenesis occurs in species in which the female lays an egg and if the egg is fertilized, it is a diploid egg and the individual develops into a female; if the egg is not fertilized, it remains a haploid egg and develops into a male. The unfertilized egg is called a parthenogenic, or virgin, egg. Some insects and reptiles lay parthenogenic eggs that can develop into adults. 

Sexual reproduction requires two cells; when the haploid egg and sperm cells fuse, a diploid zygote results. The zygote nucleus contains the genetic information to produce a new individual. However, early embryonic development requires the cytoplasmic material contained in the egg cell. This idea forms the basis for reproductive cloning. Therefore, if the haploid nucleus of an egg cell is replaced with a diploid nucleus from the cell of any individual of the same species (called a donor), it will become a zygote that is genetically identical to the donor. Somatic cell nuclear transfer is the technique of transferring a diploid nucleus into an enucleated egg. It can be used for either therapeutic cloning or reproductive cloning. 

The first cloned animal was Dolly, a sheep who was born in 1996. The success rate of reproductive cloning at the time was very low. Dolly lived for seven years and died of respiratory complications ( [link] ). There is speculation that because the cell DNA belongs to an older individual, the age of the DNA may affect the life expectancy of a cloned individual. Since Dolly, several animals such as horses, bulls, and goats have been successfully cloned, although these individuals often exhibit facial, limb, and cardiac abnormalities. There have been attempts at producing cloned human embryos as sources of embryonic stem cells, sometimes referred to as cloning for therapeutic purposes. Therapeutic cloning produces stem cells to attempt to remedy detrimental diseases or defects (unlike reproductive cloning, which aims to reproduce an organism). Still, therapeutic cloning efforts have met with resistance because of bioethical considerations. 

Dolly the sheep was the first mammal to be cloned. To create Dolly, the nucleus was removed from a donor egg cell. The nucleus from a second sheep was then introduced into the cell, which was allowed to divide to the blastocyst stage before being implanted in a surrogate mother. (credit: modification of work by "Squidonius"/Wikimedia Commons) 

[link] Genetic Engineering 

Genetic engineering is the alteration of an organism s genotype using recombinant DNA technology to modify an organism s DNA to achieve desirable traits. The addition of foreign DNA in the form of recombinant DNA vectors generated by molecular cloning is the most common method of genetic engineering. The organism that receives the recombinant DNA is called a genetically modified organism (GMO). If the foreign DNA that is introduced comes from a different species, the host organism is called transgenic . Bacteria, plants, and animals have been genetically modified since the early 1970s for academic, medical, agricultural, and industrial purposes. In the US, GMOs such as Roundup-ready soybeans and borer-resistant corn are part of many common processed foods. Gene Targeting 

Although classical methods of studying the function of genes began with a given phenotype and determined the genetic basis of that phenotype, modern techniques allow researchers to start at the DNA sequence level and ask: "What does this gene or DNA element do?" This technique, called reverse genetics, has resulted in reversing the classic genetic methodology. This method would be similar to damaging a body part to determine its function. An insect that loses a wing cannot fly, which means that the function of the wing is flight. The classical genetic method would compare insects that cannot fly with insects that can fly, and observe that the non-flying insects have lost wings. Similarly, mutating or deleting genes provides researchers with clues about gene function. The methods used to disable gene function are collectively called gene targeting. Gene targeting is the use of recombinant DNA vectors to alter the expression of a particular gene, either by introducing mutations in a gene, or by eliminating the expression of a certain gene by deleting a part or all of the gene sequence from the genome of an organism. Biotechnology in Medicine and Agriculture 

It is easy to see how biotechnology can be used for medicinal purposes. Knowledge of the genetic makeup of our species, the genetic basis of heritable diseases, and the invention of technology to manipulate and fix mutant genes provides methods to treat the disease. Biotechnology in agriculture can enhance resistance to disease, pest, and environmental stress, and improve both crop yield and quality. Genetic Diagnosis and Gene Therapy 

The process of testing for suspected genetic defects before administering treatment is called genetic diagnosis by genetic testing . Depending on the inheritance patterns of a disease-causing gene, family members are advised to undergo genetic testing. For example, women diagnosed with breast cancer are usually advised to have a biopsy so that the medical team can determine the genetic basis of cancer development. Treatment plans are based on the findings of genetic tests that determine the type of cancer. If the cancer is caused by inherited gene mutations, other female relatives are also advised to undergo genetic testing and periodic screening for breast cancer. Genetic testing is also offered for fetuses (or embryos with in vitro fertilization) to determine the presence or absence of disease-causing genes in families with specific debilitating diseases. 

Gene therapy is a genetic engineering technique used to cure disease. In its simplest form, it involves the introduction of a good gene at a random location in the genome to aid the cure of a disease that is caused by a mutated gene. The good gene is usually introduced into diseased cells as part of a vector transmitted by a virus that can infect the host cell and deliver the foreign DNA ( [link] ). More advanced forms of gene therapy try to correct the mutation at the original site in the genome, such as is the case with treatment of severe combined immunodeficiency (SCID). Gene therapy using an adenovirus vector can be used to cure certain genetic diseases in which a person has a defective gene. (credit: NIH) Production of Vaccines, Antibiotics, and Hormones 

Traditional vaccination strategies use weakened or inactive forms of microorganisms to mount the initial immune response. Modern techniques use the genes of microorganisms cloned into vectors to mass produce the desired antigen. The antigen is then introduced into the body to stimulate the primary immune response and trigger immune memory. Genes cloned from the influenza virus have been used to combat the constantly changing strains of this virus. 

Antibiotics are a biotechnological product. They are naturally produced by microorganisms, such as fungi, to attain an advantage over bacterial populations. Antibiotics are produced on a large scale by cultivating and manipulating fungal cells. 

Recombinant DNA technology was used to produce large-scale quantities of human insulin in E. coli as early as 1978. Previously, it was only possible to treat diabetes with pig insulin, which caused allergic reactions in humans because of differences in the gene product. In addition, human growth hormone (HGH) is used to treat growth disorders in children. The HGH gene was cloned from a cDNA library and inserted into E. coli cells by cloning it into a bacterial vector. Transgenic Animals 

Although several recombinant proteins used in medicine are successfully produced in bacteria, some proteins require a eukaryotic animal host for proper processing. For this reason, the desired genes are cloned and expressed in animals, such as sheep, goats, chickens, and mice. Animals that have been modified to express recombinant DNA are called transgenic animals. Several human proteins are expressed in the milk of transgenic sheep and goats, and some are expressed in the eggs of chickens. Mice have been used extensively for expressing and studying the effects of recombinant genes and mutations. Transgenic Plants 

Manipulating the DNA of plants (i.e., creating GMOs) has helped to create desirable traits, such as disease resistance, herbicide and pesticide resistance, better nutritional value, and better shelf-life ( [link] ). Plants are the most important source of food for the human population. Farmers developed ways to select for plant varieties with desirable traits long before modern-day biotechnology practices were established. Corn, a major agricultural crop used to create products for a variety of industries, is often modified through plant biotechnology. (credit: Keith Weller, USDA) 

Plants that have received recombinant DNA from other species are called transgenic plants. Because they are not natural, transgenic plants and other GMOs are closely monitored by government agencies to ensure that they are fit for human consumption and do not endanger other plant and animal life. Because foreign genes can spread to other species in the environment, extensive testing is required to ensure ecological stability. Staples like corn, potatoes, and tomatoes were the first crop plants to be genetically engineered. Transformation of Plants Using Agrobacterium tumefaciens 

Gene transfer occurs naturally between species in microbial populations. Many viruses that cause human diseases, such as cancer, act by incorporating their DNA into the human genome. In plants, tumors caused by the bacterium Agrobacterium tumefaciens occur by transfer of DNA from the bacterium to the plant. Although the tumors do not kill the plants, they make the plants stunted and more susceptible to harsh environmental conditions. Many plants, such as walnuts, grapes, nut trees, and beets, are affected by A. tumefaciens . The artificial introduction of DNA into plant cells is more challenging than in animal cells because of the thick plant cell wall. 

Researchers used the natural transfer of DNA from Agrobacterium to a plant host to introduce DNA fragments of their choice into plant hosts. In nature, the disease-causing A. tumefaciens have a set of plasmids, called the Ti plasmids (tumor-inducing plasmids), that contain genes for the production of tumors in plants. DNA from the Ti plasmid integrates into the infected plant cell s genome. Researchers manipulate the Ti plasmids to remove the tumor-causing genes and insert the desired DNA fragment for transfer into the plant genome. The Ti plasmids carry antibiotic resistance genes to aid selection and can be propagated in E. coli cells as well. The Organic Insecticide Bacillus thuringiensis 

Bacillus thuringiensis (Bt) is a bacterium that produces protein crystals during sporulation that are toxic to many insect species that affect plants. Bt toxin has to be ingested by insects for the toxin to be activated. Insects that have eaten Bt toxin stop feeding on the plants within a few hours. After the toxin is activated in the intestines of the insects, death occurs within a couple of days. Modern biotechnology has allowed plants to encode their own crystal Bt toxin that acts against insects. The crystal toxin genes have been cloned from Bt and introduced into plants. Bt toxin has been found to be safe for the environment, non-toxic to humans and other mammals, and is approved for use by organic farmers as a natural insecticide. Flavr Savr Tomato 

The first GM crop to be introduced into the market was the Flavr Savr Tomato produced in 1994. Antisense RNA technology was used to slow down the process of softening and rotting caused by fungal infections, which led to increased shelf life of the GM tomatoes. Additional genetic modification improved the flavor of this tomato. The Flavr Savr tomato did not successfully stay in the market because of problems maintaining and shipping the crop. Section Summary 

Nucleic acids can be isolated from cells for the purposes of further analysis by breaking open the cells and enzymatically destroying all other major macromolecules. Fragmented or whole chromosomes can be separated on the basis of size by gel electrophoresis. Short stretches of DNA or RNA can be amplified by PCR. Southern and northern blotting can be used to detect the presence of specific short sequences in a DNA or RNA sample. The term cloning may refer to cloning small DNA fragments (molecular cloning), cloning cell populations (cellular cloning), or cloning entire organisms (reproductive cloning). Genetic testing is performed to identify disease-causing genes, and gene therapy is used to cure an inheritable disease. 

Transgenic organisms possess DNA from a different species, usually generated by molecular cloning techniques. Vaccines, antibiotics, and hormones are examples of products obtained by recombinant DNA technology. Transgenic plants are usually created to improve characteristics of crop plants. Review Questions 

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[link] Glossary antibiotic resistance ability of an organism to be unaffected by the actions of an antibiotic biotechnology use of biological agents for technological advancement cellular cloning production of identical cell populations by binary fission clone exact replica foreign DNA DNA that belongs to a different species or DNA that is artificially synthesized gel electrophoresis technique used to separate molecules on the basis of size using electric charge gene targeting method for altering the sequence of a specific gene by introducing the modified version on a vector gene therapy technique used to cure inheritable diseases by replacing mutant genes with good genes genetic diagnosis diagnosis of the potential for disease development by analyzing disease-causing genes genetic engineering alteration of the genetic makeup of an organism genetic testing process of testing for the presence of disease-causing genes genetically modified organism (GMO) organism whose genome has been artificially changed host DNA DNA that is present in the genome of the organism of interest lysis buffer solution used to break the cell membrane and release cell contents molecular cloning cloning of DNA fragments multiple cloning site (MCS) site that can be recognized by multiple restriction endonucleases northern blotting transfer of RNA from a gel to a nylon membrane polymerase chain reaction (PCR) technique used to amplify DNA probe small DNA fragment used to determine if the complementary sequence is present in a DNA sample protease enzyme that breaks down proteins recombinant DNA combination of DNA fragments generated by molecular cloning that does not exist in nature; also known as a chimeric molecule recombinant protein protein product of a gene derived by molecular cloning reproductive cloning cloning of entire organisms restriction endonuclease enzyme that can recognize and cleave specific DNA sequences reverse genetics method of determining the function of a gene by starting with the gene itself instead of starting with the gene product reverse transcriptase PCR (RT-PCR) PCR technique that involves converting RNA to DNA by reverse transcriptase ribonuclease enzyme that breaks down RNA Southern blotting transfer of DNA from a gel to a nylon membrane Ti plasmid plasmid system derived from Agrobacterium tumifaciens that has been used by scientists to introduce foreign DNA into plant cells transgenic organism that receives DNA from a different speciesMapping Genomes Mapping Genomes 

In this section, you will explore the following questions: What is genomics? What is a genetic map? What is an example of a genomic mapping method? Connection for AP Courses 

Genome mapping is similar to solving a big, complicated puzzle with pieces of information collected from laboratories all over the world. Genetic maps provide an outline for the location of genes within a chromosome. Distances between genes and genetic markers are estimated on the basis of recombination (crossing over) frequencies during meiosis. The Human Genome Project helped researchers identify thousands of human genes and their protein products. Noncoding regions of DNA may be involved in regulating gene expression, and other sequences once considered junk may play an important role in genome evolution. Few differences exist between human DNA sequences and those of many other organisms. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. 

Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. 

Enduring Understanding 3.A Heritable information provides for continuity of life. Essential Knowledge 3.A.1 DNA, and in some cases RNA, is the primary source of heritable information. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.5 The student can justify the claim that humans can manipulate heritable information by identifying examples of commonly used technologies. Essential Knowledge 3.A.2 In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 3.10 The student is able to represent the connection between meiosis and increased genetic diversity necessary for evolution. Essential Knowledge 3.A.3 The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. 

Mapping is the first step in examining the genome of an organism. Some of the techniques have been used for years while others were developed with the advances in technology. In addition to discussing the details of this subject, this may be a good time to discuss the genetic similarities between races of people and between humans and other organisms. A very good movie about this has been put out by PBS, here . Obtain examples of genetic and physical maps and cytogenetic maps for humans and other species to use in general teaching and in the discussions suggested above. 

Genomics is the study of entire genomes, including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species. Genome mapping is the process of finding the locations of genes on each chromosome. The maps created by genome mapping are comparable to the maps that we use to navigate streets. A genetic map is an illustration that lists genes and their location on a chromosome. Genetic maps provide the big picture (similar to a map of interstate highways) and use genetic markers (similar to landmarks). A genetic marker is a gene or sequence on a chromosome that co-segregates (shows genetic linkage) with a specific trait. Early geneticists called this linkage analysis. Physical maps present the intimate details of smaller regions of the chromosomes (similar to a detailed road map). A physical map is a representation of the physical distance, in nucleotides, between genes or genetic markers. Both genetic linkage maps and physical maps are required to build a complete picture of the genome. Having a complete map of the genome makes it easier for researchers to study individual genes. Human genome maps help researchers in their efforts to identify human disease-causing genes related to illnesses like cancer, heart disease, and cystic fibrosis. Genome mapping can be used in a variety of other applications, such as using live microbes to clean up pollutants or even prevent pollution. Research involving plant genome mapping may lead to producing higher crop yields or developing plants that better adapt to climate change. Genetic Maps 

The study of genetic maps begins with linkage analysis , a procedure that analyzes the recombination frequency between genes to determine if they are linked or show independent assortment. The term linkage was used before the discovery of DNA. Early geneticists relied on the observation of phenotypic changes to understand the genotype of an organism. Shortly after Gregor Mendel (the father of modern genetics) proposed that traits were determined by what are now known as genes, other researchers observed that different traits were often inherited together, and thereby deduced that the genes were physically linked by being located on the same chromosome. The mapping of genes relative to each other based on linkage analysis led to the development of the first genetic maps. 

Observations that certain traits were always linked and certain others were not linked came from studying the offspring of crosses between parents with different traits. For example, in experiments performed on the garden pea, it was discovered that the color of the flower and shape of the plant s pollen were linked traits, and therefore the genes encoding these traits were in close proximity on the same chromosome. The exchange of DNA between homologous pairs of chromosomes is called genetic recombination , which occurs by the crossing over of DNA between homologous strands of DNA, such as nonsister chromatids. Linkage analysis involves studying the recombination frequency between any two genes. The greater the distance between two genes, the higher the chance that a recombination event will occur between them, and the higher the recombination frequency between them. Two possibilities for recombination between two nonsister chromatids during meiosis are shown in [link] . If the recombination frequency between two genes is less than 50 percent, they are said to be linked. Crossover may occur at different locations on the chromosome. Recombination between genes A and B is more frequent than recombination between genes B and C because genes A and B are farther apart; a crossover is therefore more likely to occur between them. 

The generation of genetic maps requires markers, just as a road map requires landmarks (such as rivers and mountains). Early genetic maps were based on the use of known genes as markers. More sophisticated markers, including those based on non-coding DNA, are now used to compare the genomes of individuals in a population. Although individuals of a given species are genetically similar, they are not identical; every individual has a unique set of traits. These minor differences in the genome between individuals in a population are useful for the purposes of genetic mapping. In general, a good genetic marker is a region on the chromosome that shows variability or polymorphism (multiple forms) in the population. 

Some genetic markers used in generating genetic maps are restriction fragment length polymorphisms (RFLP), variable number of tandem repeats (VNTRs), microsatellite polymorphisms , and the single nucleotide polymorphisms (SNPs). RFLPs (sometimes pronounced rif-lips ) are detected when the DNA of an individual is cut with a restriction endonuclease that recognizes specific sequences in the DNA to generate a series of DNA fragments, which are then analyzed by gel electrophoresis. The DNA of every individual will give rise to a unique pattern of bands when cut with a particular set of restriction endonucleases; this is sometimes referred to as an individual s DNA fingerprint. Certain regions of the chromosome that are subject to polymorphism will lead to the generation of the unique banding pattern. VNTRs are repeated sets of nucleotides present in the non-coding regions of DNA. Non-coding, or junk, DNA has no known biological function; however, research shows that much of this DNA is actually transcribed. While its function is uncertain, it is certainly active, and it may be involved in the regulation of coding genes. The number of repeats may vary in individual organisms of a population. Microsatellite polymorphisms are similar to VNTRs, but the repeat unit is very small. SNPs are variations in a single nucleotide. 

Because genetic maps rely completely on the natural process of recombination, mapping is affected by natural increases or decreases in the level of recombination in any given area of the genome. Some parts of the genome are recombination hotspots, whereas others do not show a propensity for recombination. For this reason, it is important to look at mapping information developed by multiple methods. Physical Maps 

A physical map provides detail of the actual physical distance between genetic markers, as well as the number of nucleotides. There are three methods used to create a physical map: cytogenetic mapping, radiation hybrid mapping, and sequence mapping. Cytogenetic mapping uses information obtained by microscopic analysis of stained sections of the chromosome ( [link] ). It is possible to determine the approximate distance between genetic markers using cytogenetic mapping, but not the exact distance (number of base pairs). Radiation hybrid mapping uses radiation, such as x-rays, to break the DNA into fragments. The amount of radiation can be adjusted to create smaller or larger fragments. This technique overcomes the limitation of genetic mapping and is not affected by increased or decreased recombination frequency. Sequence mapping resulted from DNA sequencing technology that allowed for the creation of detailed physical maps with distances measured in terms of the number of base pairs. The creation of genomic libraries and complementary DNA (cDNA) libraries (collections of cloned sequences or all DNA from a genome) has sped up the process of physical mapping. A genetic site used to generate a physical map with sequencing technology (a sequence-tagged site, or STS) is a unique sequence in the genome with a known exact chromosomal location. An expressed sequence tag (EST) and a single sequence length polymorphism (SSLP) are common STSs. An EST is a short STS that is identified with cDNA libraries, while SSLPs are obtained from known genetic markers and provide a link between genetic maps and physical maps. A cytogenetic map shows the appearance of a chromosome after it is stained and examined under a microscope. (credit: National Human Genome Research Institute) Integration of Genetic and Physical Maps 

Genetic maps provide the outline and physical maps provide the details. It is easy to understand why both types of genome mapping techniques are important to show the big picture. Information obtained from each technique is used in combination to study the genome. Genomic mapping is being used with different model organisms that are used for research. Genome mapping is still an ongoing process, and as more advanced techniques are developed, more advances are expected. Genome mapping is similar to completing a complicated puzzle using every piece of available data. Mapping information generated in laboratories all over the world is entered into central databases, such as GenBank at the National Center for Biotechnology Information (NCBI). Efforts are being made to make the information more easily accessible to researchers and the general public. Just as we use global positioning systems instead of paper maps to navigate through roadways, NCBI has created a genome viewer tool to simplify the data-mining process. 

How to Use a Genome Map Viewer 

Problem statement: Do the human, macaque, and mouse genomes contain common DNA sequences? 

Develop a hypothesis. 

To test the hypothesis, click this link . 

In Search box on the left panel, type any gene name or phenotypic characteristic, such as iris pigmentation (eye color). Select the species you want to study, and then press Enter. The genome map viewer will indicate which chromosome encodes the gene in your search. Click each hit in the genome viewer for more detailed information. This type of search is the most basic use of the genome viewer; it can also be used to compare sequences between species, as well as many other complicated tasks. 

Is the hypothesis correct? Why or why not? 

Online Mendelian Inheritance in Man (OMIM) is a searchable online catalog of human genes and genetic disorders. This website shows genome mapping information, and also details the history and research of each trait and disorder. Click this link to search for traits (such as handedness) and genetic disorders (such as diabetes). 

[link] Think About It 

Why is so much effort being poured into genome mapping applications? How could a genetic map of the human genome help find a treatment for genetically based cancers? 

The questions are applications of Learning Objectives 3.5 and Science Practice 6.4 because mapping the human genome and possibly altering it are examples of how humans can manipulate heritable information. 

Answer 

A genetic map of the human genome for multiple individuals could identify alleles of genes that are susceptible to agents that could cause cancer. The mapping could also identify allele variations that are resistant to changes that result in cancer, thereby offering the opportunity of genetic therapy for the disorders. Section Summary 

Genome mapping is similar to solving a big, complicated puzzle with pieces of information coming from laboratories all over the world. Genetic maps provide an outline for the location of genes within a genome, and they estimate the distance between genes and genetic markers on the basis of recombination frequencies during meiosis. Physical maps provide detailed information about the physical distance between the genes. The most detailed information is available through sequence mapping. Information from all mapping and sequencing sources is combined to study an entire genome. Review Questions 

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[link] Glossary cytogenetic mapping technique that uses a microscope to create a map from stained chromosomes expressed sequence tag (EST) short STS that is identified with cDNA genetic map outline of genes and their location on a chromosome genetic marker gene or sequence on a chromosome with a known location that is associated with a specific trait genetic recombination exchange of DNA between homologous pairs of chromosomes genome mapping process of finding the location of genes on each chromosome cDNA library collection of cloned cDNA sequences genomic library collection of cloned DNA which represents all of the sequences and fragments from a genome genomics study of entire genomes including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species linkage analysis procedure that analyzes the recombination of genes to determine if they are linked microsatellite polymorphism variation between individuals in the sequence and number of repeats of microsatellite DNA physical map representation of the physical distance between genes or genetic markers radiation hybrid mapping information obtained by fragmenting the chromosome with x-rays restriction fragment length polymorphism (RFLP) variation between individuals in the length of DNA fragments generated by restriction endonucleases sequence mapping mapping information obtained after DNA sequencing single nucleotide polymorphism (SNP) variation between individuals in a single nucleotide variable number of tandem repeats (VNTRs) variation in the number of tandem repeats between individuals in the populationWhole-Genome Sequencing Whole-Genome Sequencing 

In this section, you will explore the following questions: What are three types of gene sequencing? What is whole-genome sequencing? Connection for AP Courses 

Information presented in section is not in scope for AP . However, you can study information in the section as optional or illustrative material. 

With older techniques, identification of pathogenic bacteria is a time consuming process that may take days or weeks. Previously, identification of the tuberculosis bacteria can take up to six weeks. The development of DNA microarrays has enabled clinical laboratories to shorten that time to hours, with better specificity of the identification. This has provided physicians with the information they need to get patients on the most effective antibiotic therapy rapidly, providing better care and preventing the infectious agent from spreading to more hosts. 

Although there have been significant advances in the medical sciences in recent years, doctors are still confounded by some diseases, and they are using whole-genome sequencing to get to the bottom of the problem. Whole-genome sequencing is a process that determines the DNA sequence of an entire genome. Whole-genome sequencing is a brute-force approach to problem solving when there is a genetic basis at the core of a disease. Several laboratories now provide services to sequence, analyze, and interpret entire genomes. 

For example, whole-exome sequencing is a lower-cost alternative to whole genome sequencing. In exome sequencing, only the coding, exon-producing regions of the DNA are sequenced. In 2010, whole-exome sequencing was used to save a young boy whose intestines had multiple mysterious abscesses. The child had several colon operations with no relief. Finally, whole-exome sequencing was performed, which revealed a defect in a pathway that controls apoptosis (programmed cell death). A bone-marrow transplant was used to overcome this genetic disorder, leading to a cure for the boy. He was the first person to be successfully treated based on a diagnosis made by whole-exome sequencing. Today, human genome sequencing is more readily available and can be completed in a day or two for about $1000. Strategies Used in Sequencing Projects 

The basic sequencing technique used in all modern day sequencing projects is the chain termination method (also known as the dideoxy method), which was developed by Fred Sanger in the 1970s. The chain termination method involves DNA replication of a single-stranded template with the use of a primer and a regular deoxynucleotide (dNTP), which is a monomer, or a single unit, of DNA. The primer and dNTP are mixed with a small proportion of fluorescently labeled dideoxynucleotides (ddNTPs). The ddNTPs are monomers that are missing a hydroxyl group ( OH) at the site at which another nucleotide usually attaches to form a chain ( [link] ). Each ddNTP is labeled with a different color of fluorophore. Every time a ddNTP is incorporated in the growing complementary strand, it terminates the process of DNA replication, which results in multiple short strands of replicated DNA that are each terminated at a different point during replication. When the reaction mixture is processed by gel electrophoresis after being separated into single strands, the multiple newly replicated DNA strands form a ladder because of the differing sizes. Because the ddNTPs are fluorescently labeled, each band on the gel reflects the size of the DNA strand and the ddNTP that terminated the reaction. The different colors of the fluorophore-labeled ddNTPs help identify the ddNTP incorporated at that position. Reading the gel on the basis of the color of each band on the ladder produces the sequence of the template strand ( [link] ). A dideoxynucleotide is similar in structure to a deoxynucleotide, but is missing the 3' hydroxyl group (indicated by the box). When a dideoxynucleotide is incorporated into a DNA strand, DNA synthesis stops. Frederick Sanger's dideoxy chain termination method is illustrated. Using dideoxynucleotides, the DNA fragment can be terminated at different points. The DNA is separated on the basis of size, and these bands, based on the size of the fragments, can be read. Early Strategies: Shotgun Sequencing and Pair-Wise End Sequencing 

In shotgun sequencing method, several copies of a DNA fragment are cut randomly into many smaller pieces (somewhat like what happens to a round shot cartridge when fired from a shotgun). All of the segments are then sequenced using the chain-sequencing method. Then, with the help of a computer, the fragments are analyzed to see where their sequences overlap. By matching up overlapping sequences at the end of each fragment, the entire DNA sequence can be reformed. A larger sequence that is assembled from overlapping shorter sequences is called a contig . As an analogy, consider that someone has four copies of a landscape photograph that you have never seen before and know nothing about how it should appear. The person then rips up each photograph with their hands, so that different size pieces are present from each copy. The person then mixes all of the pieces together and asks you to reconstruct the photograph. In one of the smaller pieces you see a mountain. In a larger piece, you see that the same mountain is behind a lake. A third fragment shows only the lake, but it reveals that there is a cabin on the shore of the lake. Therefore, from looking at the overlapping information in these three fragments, you know that the picture contains a mountain behind a lake that has a cabin on its shore. This is the principle behind reconstructing entire DNA sequences using shotgun sequencing. 

Originally, shotgun sequencing only analyzed one end of each fragment for overlaps. This was sufficient for sequencing small genomes. However, the desire to sequence larger genomes, such as that of a human, led to the development of double-barrel shotgun sequencing, more formally known as pairwise-end sequencing . In pairwise-end sequencing, both ends of each fragment are analyzed for overlap. Pairwise-end sequencing is, therefore, more cumbersome than shotgun sequencing, but it is easier to reconstruct the sequence because there is more available information. Next-generation Sequencing 

Since 2005, automated sequencing techniques used by laboratories are under the umbrella of next-generation sequencing , which is a group of automated techniques used for rapid DNA sequencing. These automated low-cost sequencers can generate sequences of hundreds of thousands or millions of short fragments (25 to 500 base pairs) in the span of one day. These sequencers use sophisticated software to get through the cumbersome process of putting all the fragments in order. 

Comparing Sequences A sequence alignment is an arrangement of proteins, DNA, or RNA; it is used to identify regions of similarity between cell types or species, which may indicate conservation of function or structures. Sequence alignments may be used to construct phylogenetic trees. The following website uses a software program called BLAST (basic local alignment search tool) . 

Under Basic Blast, click Nucleotide Blast. Input the following sequence into the large "query sequence" box: ATTGCTTCGATTGCA. Below the box, locate the "Species" field and type "human" or "Homo sapiens". Then click BLAST to compare the inputted sequence against known sequences of the human genome. The result is that this sequence occurs in over a hundred places in the human genome. Scroll down below the graphic with the horizontal bars and you will see short description of each of the matching hits. Pick one of the hits near the top of the list and click on "Graphics". This will bring you to a page that shows where the sequence is found within the entire human genome. You can move the slider that looks like a green flag back and forth to view the sequences immediately around the selected gene. You can then return to your selected sequence by clicking the "ATG" button. 

[link] Use of Whole-Genome Sequences of Model Organisms 

The first genome to be completely sequenced was of a bacterial virus, the bacteriophage fx174 (5368 base pairs); this was accomplished by Fred Sanger using shotgun sequencing. Several other organelle and viral genomes were later sequenced. The first organism whose genome was sequenced was the bacterium Haemophilus influenzae ; this was accomplished by Craig Venter in the 1980s. Approximately 74 different laboratories collaborated on the sequencing of the genome of the yeast Saccharomyces cerevisiae , which began in 1989 and was completed in 1996, because it was 60 times bigger than any other genome that had been sequenced. By 1997, the genome sequences of two important model organisms were available: the bacterium Escherichia coli K12 and the yeast Saccharomyces cerevisiae . Genomes of other model organisms, such as the mouse Mus musculus , the fruit fly Drosophila melanogaster , the nematode Caenorhabditis. elegans , and humans Homo sapiens are now known. A lot of basic research is performed in model organisms because the information can be applied to genetically similar organisms. A model organism is a species that is studied as a model to understand the biological processes in other species represented by the model organism. Having entire genomes sequenced helps with the research efforts in these model organisms. The process of attaching biological information to gene sequences is called genome annotation . Annotation of gene sequences helps with basic experiments in molecular biology, such as designing PCR primers and RNA targets. 

Click through each step of genome sequencing at this site . 

[link] Uses of Genome Sequences 

DNA microarrays are methods used to detect gene expression by analyzing an array of DNA fragments that are fixed to a glass slide or a silicon chip to identify active genes and identify sequences. Almost one million genotypic abnormalities can be discovered using microarrays, whereas whole-genome sequencing can provide information about all six billion base pairs in the human genome. Although the study of medical applications of genome sequencing is interesting, this discipline tends to dwell on abnormal gene function. Knowledge of the entire genome will allow future onset diseases and other genetic disorders to be discovered early, which will allow for more informed decisions to be made about lifestyle, medication, and having children. Genomics is still in its infancy, although someday it may become routine to use whole-genome sequencing to screen every newborn to detect genetic abnormalities. 

In addition to disease and medicine, genomics can contribute to the development of novel enzymes that convert biomass to biofuel, which results in higher crop and fuel production, and lower cost to the consumer. This knowledge should allow better methods of control over the microbes that are used in the production of biofuels. Genomics could also improve the methods used to monitor the impact of pollutants on ecosystems and help clean up environmental contaminants. Genomics has allowed for the development of agrochemicals and pharmaceuticals that could benefit medical science and agriculture. 

It sounds great to have all the knowledge we can get from whole-genome sequencing; however, humans have a responsibility to use this knowledge wisely. Otherwise, it could be easy to misuse the power of such knowledge, leading to discrimination based on a person's genetics, human genetic engineering, and other ethical concerns. This information could also lead to legal issues regarding health and privacy. Section Summary 

Whole-genome sequencing is the latest available resource to treat genetic diseases. Some doctors are using whole-genome sequencing to save lives. Genomics has many industrial applications including biofuel development, agriculture, pharmaceuticals, and pollution control. The basic principle of all modern-day sequencing strategies involves the chain termination method of sequencing. 

Although the human genome sequences provide key insights to medical professionals, researchers use whole-genome sequences of model organisms to better understand the genome of the species. Automation and the decreased cost of whole-genome sequencing may lead to personalized medicine in the future. Review Questions 

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[link] Glossary chain termination method method of DNA sequencing using labeled dideoxynucleotides to terminate DNA replication; it is also called the dideoxy method or the Sanger method contig larger sequence of DNA assembled from overlapping shorter sequences deoxynucleotide individual monomer (single unit) of DNA dideoxynucleotide individual monomer of DNA that is missing a hydroxyl group ( OH) DNA microarray method used to detect gene expression by analyzing an array of DNA fragments that are fixed to a glass slide or a silicon chip to identify active genes and identify sequences genome annotation process of attaching biological information to gene sequences model organism species that is studied and used as a model to understand the biological processes in other species represented by the model organism next-generation sequencing group of automated techniques used for rapid DNA sequencing shotgun sequencing method used to sequence multiple DNA fragments to generate the sequence of a large piece of DNA whole-genome sequencing process that determines the DNA sequence of an entire genomeApplying Genomics Applying Genomics 

In this section, you will explore the following questions: What is pharmacogenomics? What is an example of a polygenic human disease? Connection for AP Courses 

Information presented in section is not in scope for AP . However, you can study information in the section as optional or illustrative material. 

Predicting Disease Risk at the Individual Level: 

Cancer, heart disease, and stroke account for a large number of health problems in developed countries. Genomics is a tool which allows physicians to predict who may be susceptible to particular cancers and what someone s risk of heart disease is. This is making adjustments in life style and important to prolonging life. 

Pharmacogenomics and Toxicogenomics: 

Assign the class the job of identifying drugs from the literature whose metabolism is susceptible to genetic variation in patients. Can pharmacogenomics benefit these patients? 

Microbial Genomics: Creation of New Biofuels, Mitochondrial Genomics, Genomics in Agriculture: 

Assign three groups from the class to investigate the following questions. What biofuels are on the market and what has their impact been on energy use? Why are mitochondrial genes examined in forensic cases, but not nuclear chromosomal material? What effects have agricultural applications of genomics had? 

The introduction of DNA sequencing and whole genome sequencing projects, particularly the Human Genome project, has expanded the applicability of DNA sequence information. Genomics is now being used in a wide variety of fields, such as metagenomics, pharmacogenomics, and mitochondrial genomics. The most commonly known application of genomics is to understand and find cures for diseases. Predicting Disease Risk at the Individual Level 

Predicting the risk of disease involves screening currently healthy individuals by genome analysis at the individual level. Intervention with lifestyle changes and drugs can be recommended before disease onset. However, this approach is most applicable when the problem resides within a single gene defect. Such defects only account for approximately 5 percent of diseases in developed countries. Most of the common diseases, such as heart disease, are multi-factored or polygenic , which is a phenotypic characteristic that involves two or more genes, and also involve environmental factors such as diet. In April 2010, scientists at Stanford University published the genome analysis of a healthy individual (Stephen Quake, a scientist at Stanford University, who had his genome sequenced); the analysis predicted his propensity to acquire various diseases. A risk assessment was performed to analyze Quake s percentage of risk for 55 different medical conditions. A rare genetic mutation was found, which showed him to be at risk for sudden heart attack. He was also predicted to have a 23 percent risk of developing prostate cancer and a 1.4 percent risk of developing Alzheimer s. The scientists used databases and several publications to analyze the genomic data. Even though genomic sequencing is becoming more affordable and analytical tools are becoming more reliable, ethical issues surrounding genomic analysis at a population level remain to be addressed. 

PCA3 is a gene that is expressed in prostate epithelial cells and overexpressed in cancerous cells. A high concentration of PCA3 in urine is indicative of prostate cancer. The PCA3 test is considered to be a better indicator of cancer than the more well know PSA test, which measures the level of PSA (prostate-specific antigen) in the blood. 

[link] Pharmacogenomics and Toxicogenomics 

Pharmacogenomics , also called toxicogenomics, involves evaluating the effectiveness and safety of drugs on the basis of information from an individual's genomic sequence. Genomic responses to drugs can be studied using experimental animals (such as laboratory rats or mice) or live cells in the laboratory before embarking on studies with humans. Studying changes in gene expression could provide information about the transcription profile in the presence of the drug, which can be used as an early indicator of the potential for toxic effects. For example, genes involved in cellular growth and controlled cell death, when disturbed, could lead to the growth of cancerous cells. Genome-wide studies can also help to find new genes involved in drug toxicity. Personal genome sequence information can be used to prescribe medications that will be most effective and least toxic on the basis of the individual patient s genotype. The gene signatures may not be completely accurate, but can be tested further before pathologic symptoms arise. Microbial Genomics: Metagenomics 

Traditionally, microbiology has been taught with the view that microorganisms are best studied under pure culture conditions, which involves isolating a single type of cell and culturing it in the laboratory. Because microorganisms can go through several generations in a matter of hours, their gene expression profiles adapt to the new laboratory environment very quickly. In addition, the vast majority of bacterial species resist being cultured in isolation. Most microorganisms do not live as isolated entities, but in microbial communities known as biofilms. For all of these reasons, pure culture is not always the best way to study microorganisms. Metagenomics is the study of the collective genomes of multiple species that grow and interact in an environmental niche. Metagenomics can be used to identify new species more rapidly and to analyze the effect of pollutants on the environment ( [link] ). Metagenomics involves isolating DNA from multiple species within an environmental niche. Microbial Genomics: Creation of New Biofuels 

Knowledge of the genomics of microorganisms is being used to find better ways to harness biofuels from algae and cyanobacteria. The primary sources of fuel today are coal, oil, wood, and other plant products, such as ethanol. Although plants are renewable resources, there is still a need to find more alternative renewable sources of energy to meet our population s energy demands. The microbial world is one of the largest resources for genes that encode new enzymes and produce new organic compounds, and it remains largely untapped. Microorganisms are used to create products, such as enzymes that are used in research, antibiotics, and other anti-microbial mechanisms. Microbial genomics is helping to develop diagnostic tools, improved vaccines, new disease treatments, and advanced environmental cleanup techniques. Mitochondrial Genomics 

Mitochondria are intracellular organelles that contain their own DNA. Mitochondrial DNA mutates at a rapid rate and is often used to study evolutionary relationships. Another feature that makes studying the mitochondrial genome interesting is that the mitochondrial DNA in most multicellular organisms is passed on from the mother during the process of fertilization. For this reason, mitochondrial genomics is often used to trace genealogy. 

Information and clues obtained from DNA samples found at crime scenes have been used as evidence in court cases, and genetic markers have been used in forensic analysis. Genomic analysis has also become useful in this field. In 2001, the first use of genomics in forensics was published. It was a collaborative attempt between academic research institutions and the FBI to solve the mysterious cases of anthrax communicated via the US Postal Service. Using microbial genomics, researchers determined that a specific strain of anthrax was used in all the mailings. Genomics in Agriculture 

Genomics can reduce the trials and failures involved in scientific research to a certain extent, which could improve the quality and quantity of crop yields in agriculture. Linking traits to genes or gene signatures helps to improve crop breeding to generate hybrids with the most desirable qualities. Scientists use genomic data to identify desirable traits, and then transfer those traits to a different organism. Scientists are discovering how genomics can improve the quality and quantity of agricultural production. For example, scientists could use desirable traits to create a useful product or enhance an existing product, such as making a drought-sensitive crop more tolerant of the dry season. Section Summary 

Imagination is the only barrier to the applicability of genomics. Genomics is being applied to most fields of biology; it is being used for personalized medicine, prediction of disease risks at an individual level, the study of drug interactions before the conduct of clinical trials, and the study of microorganisms in the environment as opposed to the laboratory. It is also being applied to developments such as the generation of new biofuels, genealogical assessment using mitochondria, advances in forensic science, and improvements in agriculture. Review Questions 

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[link] Glossary metagenomics study of the collective genomes of multiple species that grow and interact in an environmental niche pharmacogenomics study of drug interactions with the genome or proteome; also called toxicogenomics polygenic phenotypic characteristic caused by two or more genes pure culture growth of a single type of cell in the laboratoryGenomics and Proteomics Genomics and Proteomics 

In this section, you will explore the following questions: What is a proteome? What is a protein signature and what is its relevance to cancer screening? Connection for AP Courses 

Information presented in section is not in scope for AP . However, you can study information in the section as optional or illustrative material. 

Cancer Proteomics: 

Connect this section to the previous one titled: Predicting Disease Risk at the Individual Level. Emphasize the importance of accurate testing and that there is always a number of false positives, meaning that the test is positive, but shouldn t be, and false negatives, meaning that the test should have been positive and wasn t. A test that can serve as a case study for this situation is the Prostate Specific Antigen (PSA) assay that has been used in conjunction with prostate cancer diagnosis. Research the current understanding and usefulness of the test as reflected in its characteristics of false positives and negatives. 

Proteins are the final products of genes, which help perform the function encoded by the gene. Proteins are composed of amino acids and play important roles in the cell. All enzymes (except ribozymes) are proteins that act as catalysts to affect the rate of reactions. Proteins are also regulatory molecules, and some are hormones. Transport proteins, such as hemoglobin, help transport oxygen to various organs. Antibodies that defend against foreign particles are also proteins. In the diseased state, protein function can be impaired because of changes at the genetic level or because of direct impact on a specific protein. 

A proteome is the entire set of proteins produced by a cell type. Proteomes can be studied using the knowledge of genomes because genes code for mRNAs, and the mRNAs encode proteins. Although mRNA analysis is a step in the right direction, not all mRNAs are translated into proteins. The study of the function of proteomes is called proteomics . Proteomics complements genomics and is useful when scientists want to test their hypotheses that were based on genes. Even though all cells of a multicellular organism have the same set of genes, the set of proteins produced in different tissues is different and dependent on gene expression. Thus, the genome is constant, but the proteome varies and is dynamic within an organism. In addition, RNAs can be alternately spliced (cut and pasted to create novel combinations and novel proteins) and many proteins are modified after translation by processes such as proteolytic cleavage, phosphorylation, glycosylation, and ubiquitination. There are also protein-protein interactions, which complicate the study of proteomes. Although the genome provides a blueprint, the final architecture depends on several factors that can change the progression of events that generate the proteome. 

Metabolomics is related to genomics and proteomics. Metabolomics involves the study of small molecule metabolites found in an organism. The metabolome is the complete set of metabolites that are related to the genetic makeup of an organism. Metabolomics offers an opportunity to compare genetic makeup and physical characteristics, as well as genetic makeup and environmental factors. The goal of metabolome research is to identify, quantify, and catalogue all of the metabolites that are found in the tissues and fluids of living organisms. Basic Techniques in Protein Analysis 

The ultimate goal of proteomics is to identify or compare the proteins expressed from a given genome under specific conditions, study the interactions between the proteins, and use the information to predict cell behavior or develop drug targets. Just as the genome is analyzed using the basic technique of DNA sequencing, proteomics requires techniques for protein analysis. The basic technique for protein analysis, analogous to DNA sequencing, is mass spectrometry. Mass spectrometry is used to identify and determine the characteristics of a molecule. Advances in spectrometry have allowed researchers to analyze very small samples of protein. X-ray crystallography, for example, enables scientists to determine the three-dimensional structure of a protein crystal at atomic resolution. Another protein imaging technique, nuclear magnetic resonance (NMR), uses the magnetic properties of atoms to determine the three-dimensional structure of proteins in aqueous solution. Protein microarrays have also been used to study interactions between proteins. Large-scale adaptations of the basic two-hybrid screen ( [link] ) have provided the basis for protein microarrays. Computer software is used to analyze the vast amount of data generated for proteomic analysis. 

Genomic- and proteomic-scale analyses are part of systems biology. Systems biology is the study of whole biological systems (genomes and proteomes) based on interactions within the system. The European Bioinformatics Institute and the Human Proteome Organization (HUPO) are developing and establishing effective tools to sort through the enormous pile of systems biology data. Because proteins are the direct products of genes and reflect activity at the genomic level, it is natural to use proteomes to compare the protein profiles of different cells to identify proteins and genes involved in disease processes. Most pharmaceutical drug trials target proteins. Information obtained from proteomics is being used to identify novel drugs and understand their mechanisms of action. Two-hybrid screening is used to determine whether two proteins interact. In this method, a transcription factor is split into a DNA-binding domain (BD) and an activator domain (AD). The binding domain is able to bind the promoter in the absence of the activator domain, but it does not turn on transcription. A protein called the bait is attached to the BD, and a protein called the prey is attached to the AD. Transcription occurs only if the prey catches the bait. 

The challenge of techniques used for proteomic analyses is the difficulty in detecting small quantities of proteins. Although mass spectrometry is good for detecting small amounts of proteins, variations in protein expression in diseased states can be difficult to discern. Proteins are naturally unstable molecules, which makes proteomic analysis much more difficult than genomic analysis. Cancer Proteomics 

Genomes and proteomes of patients suffering from specific diseases are being studied to understand the genetic basis of the disease. The most prominent disease being studied with proteomic approaches is cancer. Proteomic approaches are being used to improve screening and early detection of cancer; this is achieved by identifying proteins whose expression is affected by the disease process. An individual protein is called a biomarker , whereas a set of proteins with altered expression levels is called a protein signature . For a biomarker or protein signature to be useful as a candidate for early screening and detection of a cancer, it must be secreted in body fluids, such as sweat, blood, or urine, such that large-scale screenings can be performed in a non-invasive fashion. The current problem with using biomarkers for the early detection of cancer is the high rate of false-negative results. A false negative is an incorrect test result that should have been positive. In other words, many cases of cancer go undetected, which makes biomarkers unreliable. Some examples of protein biomarkers used in cancer detection are CA-125 for ovarian cancer and PSA for prostate cancer. Protein signatures may be more reliable than biomarkers to detect cancer cells. Proteomics is also being used to develop individualized treatment plans, which involves the prediction of whether or not an individual will respond to specific drugs and the side effects that the individual may experience. Proteomics is also being used to predict the possibility of disease recurrence. 

The National Cancer Institute has developed programs to improve the detection and treatment of cancer. The Clinical Proteomic Technologies for Cancer and the Early Detection Research Network are efforts to identify protein signatures specific to different types of cancers. The Biomedical Proteomics Program is designed to identify protein signatures and design effective therapies for cancer patients. Section Summary 

Proteomics is the study of the entire set of proteins expressed by a given type of cell under certain environmental conditions. In a multicellular organism, different cell types will have different proteomes, and these will vary with changes in the environment. Unlike a genome, a proteome is dynamic and in constant flux, which makes it both more complicated and more useful than the knowledge of genomes alone. 

Proteomics approaches rely on protein analysis; these techniques are constantly being upgraded. Proteomics has been used to study different types of cancer. Different biomarkers and protein signatures are being used to analyze each type of cancer. The future goal is to have a personalized treatment plan for each individual. Review Questions 

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[link] Glossary biomarker individual protein that is uniquely produced in a diseased state false negative incorrect test result that should have been positive metabolome complete set of metabolites which are related to the genetic makeup of an organism metabolomics study of small molecule metabolites found in an organism protein signature set of uniquely expressed proteins in the diseased state proteome entire set of proteins produced by a cell type proteomics study of the function of proteomes systems biology study of whole biological systems (genomes and proteomes) based on interactions within the systemIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" All organisms are products of evolution adapted to their environment. (a) Saguaro ( Carnegiea gigantea ) can soak up 750 liters of water in a single rain storm, enabling these cacti to survive the dry conditions of the Sonora desert in Mexico and the Southwestern United States. (b) The Andean semiaquatic lizard ( Potamites montanicola ) discovered in Peru in 2010 lives between 1,570 to 2,100 meters in elevation, and, unlike most lizards, is nocturnal and swims. Scientists still do no know how these ectotherms, which rely on external sources of body heat, are able to move in the cold (10 to 15 C) temperatures of the Andean night. (credit a: modification of work by Gentry George, U.S. Fish and Wildlife Service; credit b: modification of work by Germ n Ch vez and Diego V squez, ZooKeys ) 

The field of biology is a diverse one that includes the study of organisms from the small and simple to the large and complex. From biological molecules to biomes, the one theme that remains consistent is evolution. All species of living organisms are descended from a common ancestor. Although it may seem that living things today stay much the same, this is not the case. Evolution is actually an ongoing process. Additionally, new species are discovered regularly. For example, scientists have used a method called fluorescent in situ hybridization, which uses fluorescent probes to locate specific genes on chromosomes, to discover a green sea slug that can perform photosynthesis just like a plant. 1 The slug obtains genes related to photosynthesis from the algae it eats through a process called horizontal gene transfer. In this process, genes can be transferred directly from one cell to another. The algal genes code for products that repair and maintain chloroplasts eaten by the slug. You can read more about it at this website . 

The ongoing process of evolution includes the repeated formation of new species (speciation), changes within species (anagenesis), and death of species (extinction). Patterns in shared morphological and biochemical traits, including shared DNA sequences, can be used in constructing a diagram that illustrates the biodiversity, taxonomic links, and evolutionary history of extinct and extant living things. Such diagrams are commonly called The Tree of Life. 

You may wish to share a tree of life diagram with students and use the diagram alongside facts about the rates of extinction (historically and currently) and species estimates versus species documentation to guide a discussion about evidence for evolution as an ongoing process. Ask students to discuss where in their daily lives they are aware of evidence of speciation, anagenesis, and extinction. Through discussion, elicit from students the importance of considering scale (both temporal and physical) when considering evidence of evolutionary change. Ideas and thoughts shared during this discussion may prove to be helpful reference points when students read about misconceptions of evolution later in the chapter. Footnotes 1 Biol. Bull. 227: 300 312. (December 2014)Understanding Evolution Understanding Evolution 

In this section, you will explore the following questions: How was the present-day theory of evolution developed? What is adaptation, and how does adaptation relate to natural selection? What are the differences between convergent and divergent evolution, and what are examples of each that support evolution by natural selection? What are examples of homologous and vestigial structures, and what evidence do these structures provide to support patterns of evolution? What are common misconceptions about the theory of evolution? Connection for AP Courses 

Millions of species, from bacteria to blueberries to baboons, currently call Earth their home, but these organisms evolved from different species. Furthermore, scientists estimate that several million more species will become extinct before they have been classified and studied. But why don t polar bears naturally inhabit deserts or rain forests, except, perhaps, in movies? Why do humans possess traits, such as opposable thumbs, that are unique to primates but not other mammals? How did observations of finches by Charles Darwin visiting the Galapagos Islands in the 1800s provide the foundation for our modern understanding of evolution? 

The theory of evolution as proposed by Darwin is the unifying theory of biology. The tenet that all life has evolved and diversified from a common ancestor is the foundation from which we approach all questions in biology. As we learned in our exploration of the structure and function of DNA, variations in individuals within a population occur through mutation, allowing more desirable traits to be passed to the next generation. Due to competition for resources and other environmental pressures, individuals possessing more favorable adaptive characteristics are more likely to survive and reproduce, passing those characteristics to the next generation with increased frequency. When environments change, what was once an unfavorable trait may become a favorable one. Organisms may evolve in response to their changing environment by the accumulation of favorable traits in succeeding generations. Thus, evolution by natural selection explains both the unity and diversity of life. 

Convergent evolution occurs when similar traits with the same function evolve in multiple species exposed to similar selection pressure, such as the wings of bats and insects. In divergent evolution , two species evolve in different directions from a common point, such as the forelimbs of humans, dogs, birds, and whales. Although Darwin s theory was revolutionary for its time because it contrasted with long-held ideas (for example, Lamarck proposed the inheritance of acquired characteristics ), evidence drawn from many scientific disciplines, including the fossil record, the existence of homologous and vestigial structures, mathematics, and DNA analysis supports evolution through natural selection. It is also important to understand that evolution continues to occur; for example, bacteria that evolve resistance to antibiotics or plants that become resistant to pesticides provide evidence for continuing change. 

Information presented and the examples highlighted in this section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.A Change in the genetic makeup of a population over time is evolution. Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.9 The student is able to evaluate evidence provided by data from many scientific disciplines that support biological evolution. Essential Knowledge 1.A.2 Natural selection acts on phenotypic variations in populations. Science Practice 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain. Learning Objective 1.5 The student is able to connect evolutionary changes in a population over time to a change in the environment. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 1.2 The student is able to evaluate evidence provided by data to qualitatively and quantitatively investigate the role of natural selection in evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.12 The student is able to connect scientific evidence from many scientific disciplines to support the modern concept of evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 5.2 The student can refine observations and measurements based on data analysis. Learning Objective 1.10 The student is able to refine evidence based on data from many scientific disciplines that support biological evolution. 

Enduring Understanding 1.C Life continues to evolve within a changing environment. Essential Knowledge 1.C.3 Populations of organisms continue to evolve. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 1.26 The student is able to evaluate given data sets that illustrate evolution as an ongoing processes. Essential Knowledge 1.C.3 Populations of organisms continue to evolve. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 1.25 The student is able to describe a model that represents evolution within a population. Essential Knowledge 1.C.3 Populations of organisms continue to evolve. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 1.4 The student is able to evaluate data-based evidence that describes evolutionary changes in the genetic makeup of a population over time. 

The chapter talks about embryology, so it might be important to mention Ernst Haeckel (1834 1919) and his famous principle "ontogeny recapitulates phylogeny." Please see this PBS website for more information. Charles Darwin and Natural Selection 

In the mid-nineteenth century, the actual mechanism for evolution was independently conceived of and described by two naturalists: Charles Darwin and Alfred Russel Wallace. Importantly, each naturalist spent time exploring the natural world on expeditions to the tropics. From 1831 to 1836, Darwin traveled around the world on H.M.S. Beagle , including stops in South America, Australia, and the southern tip of Africa. Wallace traveled to Brazil to collect insects in the Amazon rainforest from 1848 to 1852 and to the Malay Archipelago from 1854 to 1862. Darwin s journey, like Wallace s later journeys to the Malay Archipelago, included stops at several island chains, the last being the Gal pagos Islands west of Ecuador. On these islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences. For example, the ground finches inhabiting the Gal pagos Islands comprised several species with a unique beak shape ( [link] ). The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. He observed that these finches closely resembled another finch species on the mainland of South America. Darwin imagined that the island species might be species modified from one of the original mainland species. Upon further study, he realized that the varied beaks of each finch helped the birds acquire a specific type of food. For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey. Darwin observed that beak shape varies among finch species. He postulated that the beak of an ancestral species had adapted over time to equip the finches to acquire different food sources. 

Wallace and Darwin both observed similar patterns in other organisms and they independently developed the same explanation for how and why such changes could take place. Darwin called this mechanism natural selection. Natural selection , also known as survival of the fittest, is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits; this leads to evolutionary change. 

For example, a population of giant tortoises found in the Galapagos Archipelago was observed by Darwin to have longer necks than those that lived on other islands with dry lowlands. These tortoises were selected because they could reach more leaves and access more food than those with short necks. In times of drought when fewer leaves would be available, those that could reach more leaves had a better chance to eat and survive than those that couldn t reach the food source. Consequently, long-necked tortoises would be more likely to be reproductively successful and pass the long-necked trait to their offspring. Over time, only long-necked tortoises would be present in the population. 

Natural selection, Darwin argued, was an inevitable outcome of three principles that operated in nature. First, most characteristics of organisms are inherited, or passed from parent to offspring. Although no one, including Darwin and Wallace, knew how this happened at the time, it was a common understanding. Second, more offspring are produced than are able to survive, so resources for survival and reproduction are limited. The capacity for reproduction in all organisms outstrips the availability of resources to support their numbers. Thus, there is competition for those resources in each generation. Both Darwin and Wallace s understanding of this principle came from reading an essay by the economist Thomas Malthus who discussed this principle in relation to human populations. Third, offspring vary among each other in regard to their characteristics and those variations are inherited. Darwin and Wallace reasoned that offspring with inherited characteristics which allow them to best compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Because characteristics are inherited, these traits will be better represented in the next generation. This will lead to change in populations over generations in a process that Darwin called descent with modification. Ultimately, natural selection leads to greater adaptation of the population to its local environment; it is the only mechanism known for adaptive evolution. 

Papers by Darwin and Wallace ( [link] ) presenting the idea of natural selection were read together in 1858 before the Linnean Society in London. The following year Darwin s book, On the Origin of Species, was published. His book outlined in considerable detail his arguments for evolution by natural selection. Both (a) Charles Darwin and (b) Alfred Wallace wrote scientific papers on natural selection that were presented together before the Linnean Society in 1858. 

Demonstrations of evolution by natural selection are time consuming and difficult to obtain. One of the best examples has been demonstrated in the very birds that helped to inspire Darwin s theory: the Gal pagos finches. Peter and Rosemary Grant and their colleagues have studied Gal pagos finch populations every year since 1976 and have provided important demonstrations of natural selection. The Grants found changes from one generation to the next in the distribution of beak shapes with the medium ground finch on the Gal pagos island of Daphne Major. The birds have inherited variation in the bill shape with some birds having wide deep bills and others having thinner bills. During a period in which rainfall was higher than normal because of an El Ni o, the large hard seeds that large-billed birds ate were reduced in number; however, there was an abundance of the small soft seeds which the small-billed birds ate. Therefore, survival and reproduction were much better in the following years for the small-billed birds. In the years following this El Ni o, the Grants measured beak sizes in the population and found that the average bill size was smaller. Since bill size is an inherited trait, parents with smaller bills had more offspring and the size of bills had evolved to be smaller. As conditions improved in 1987 and larger seeds became more available, the trend toward smaller average bill size ceased. Career Connection 

Field Biologist Many people hike, explore caves, scuba dive, or climb mountains for recreation. People often participate in these activities hoping to see wildlife. Experiencing the outdoors can be incredibly enjoyable and invigorating. What if your job was to be outside in the wilderness? Field biologists by definition work outdoors in the field. The term field in this case refers to any location outdoors, even under water. A field biologist typically focuses research on a certain species, group of organisms, or a single habitat ( [link] ). A field biologist tranquilizes a polar bear for study. (credit: Karen Rhode) 

One objective of many field biologists includes discovering new species that have never been recorded. Not only do such findings expand our understanding of the natural world, but they also lead to important innovations in fields such as medicine and agriculture. Plant and microbial species, in particular, can reveal new medicinal and nutritive knowledge. Other organisms can play key roles in ecosystems or be considered rare and in need of protection. When discovered, these important species can be used as evidence for environmental regulations and laws. Processes and Patterns of Evolution 

Natural selection can only take place if there is variation , or differences, among individuals in a population. Importantly, these differences must have some genetic basis; otherwise, the selection will not lead to change in the next generation. This is critical because variation among individuals can be caused by non-genetic reasons such as an individual being taller because of better nutrition rather than different genes. 

Genetic diversity in a population comes from two main mechanisms: mutation and sexual reproduction. Mutation, a change in DNA, is the ultimate source of new alleles, or new genetic variation in any population. The genetic changes caused by mutation can have one of three outcomes on the phenotype. A mutation can affect the phenotype of the organism in a way that gives it reduced fitness lower likelihood of survival or fewer offspring. Alternatively, a mutation may produce a phenotype with a beneficial effect on fitness. And, many mutations will also have no effect on the fitness of the phenotype; these are called neutral mutations. Mutations may also have a whole range of effect sizes on the fitness of the organism that expresses them in their phenotype, from a small effect to a great effect. Sexual reproduction also leads to genetic diversity: when two parents reproduce, unique combinations of alleles assemble to produce the unique genotypes and thus phenotypes in each of the offspring. 

A heritable trait that helps the survival and reproduction of an organism in its present environment is called an adaptation . Scientists describe groups of organisms becoming adapted to their environment when a change in the range of genetic variation occurs over time that increases or maintains the fit of the population to its environment. The webbed feet of platypuses are an adaptation for swimming. The snow leopards thick fur is an adaptation for living in the cold. The cheetahs fast speed is an adaptation for catching prey. 

Whether or not a trait is favorable depends on the environmental conditions at the time. The same traits are not always selected because environmental conditions can change. For example, consider a species of plant that grew in a moist climate and did not need to conserve water. Large leaves were selected because they allowed the plant to obtain more energy from the sun. Large leaves require more water to maintain than small leaves, and the moist environment provided favorable conditions to support large leaves. After thousands of years, the climate changed, and the area no longer had excess water. The direction of natural selection shifted so that plants with small leaves were selected because those populations were able to conserve water to survive the new environmental conditions. 

The evolution of species has resulted in enormous variation in form and function. Sometimes, evolution gives rise to groups of organisms that become tremendously different from each other. When two species evolve in diverse directions from a common point, it is called divergent evolution. Such divergent evolution can be seen in the forms of the reproductive organs of flowering plants which share the same basic anatomies; however, they can look very different as a result of selection in different physical environments and adaptation to different kinds of pollinators ( [link] ). Flowering plants evolved from a common ancestor. Notice that the (a) dense blazing star ( Liatrus spicata ) and the (b) purple coneflower ( Echinacea purpurea ) vary in appearance, yet both share a similar basic morphology. (credit a: modification of work by Drew Avery; credit b: modification of work by Cory Zanker) 

In other cases, similar phenotypes evolve independently in distantly related species. For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. However, the wings of bats and insects have evolved from very different original structures. This phenomenon is called convergent evolution, where similar traits evolve independently in species that do not share a recent common ancestry. The two species came to the same function, flying, but did so separately from each other. 

These physical changes occur over enormous spans of time and help explain how evolution occurs. Natural selection acts on individual organisms, which in turn can shape an entire species. Although natural selection may work in a single generation on an individual, it can take thousands or even millions of years for the genotype of an entire species to evolve. It is over these large time spans that life on earth has changed and continues to change. Evidence of Evolution 

The evidence for evolution is compelling and extensive. Looking at every level of organization in living systems, biologists see the signature of past and present evolution. Darwin dedicated a large portion of his book, On the Origin of Species , to identifying patterns in nature that were consistent with evolution, and since Darwin, our understanding has become clearer and broader. Fossils 

Fossils provide solid evidence that organisms from the past are not the same as those found today, and fossils show a progression of evolution. Scientists determine the age of fossils and categorize them from all over the world to determine when the organisms lived relative to each other. The resulting fossil record tells the story of the past and shows the evolution of form over millions of years ( [link] ). For example, scientists have recovered highly detailed records showing the evolution of humans and horses. In this (a) display, fossil hominids are arranged from oldest (bottom) to newest (top). As hominids evolved, the shape of the skull changed. An artist s rendition of (b) extinct species of the genus Equus reveals that these ancient species resembled the modern horse ( Equus ferus ) but varied in size. Anatomy and Embryology 

Another type of evidence for evolution is the presence of structures in organisms that share the same basic form. For example, the bones in the appendages of a human, dog, bird, and whale all share the same overall construction ( [link] ) resulting from their origin in the appendages of a common ancestor. Over time, evolution led to changes in the shapes and sizes of these bones in different species, but they have maintained the same overall layout. Scientists call these synonymous parts homologous structures . The similar construction of these appendages indicates that these organisms share a common ancestor. 

Some structures exist in organisms that have no apparent function at all, and appear to be residual parts from a past common ancestor. These unused structures without function are called vestigial structures . Examples of vestigial structures include wings on flightless birds, leaves on some cacti, and hind leg bones in whales. Link to Learning 

Visit this interactive site to guess which bones structures are homologous and which are analogous, and see examples of evolutionary adaptations to illustrate these concepts. 

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Another evidence of evolution is the convergence of form in organisms that share similar environments. For example, species of unrelated animals, such as the arctic fox and ptarmigan, living in the arctic region have been selected for seasonal white phenotypes during winter to blend with the snow and ice ( [link] ab ). These similarities occur not because of common ancestry, but because of similar selection pressures the benefits of not being seen by predators. The white winter coat of the (a) arctic fox and the (b) ptarmigan s plumage are adaptations to their environments. (credit a: modification of work by Keith Morehouse) 

Embryology, the study of the development of the anatomy of an organism to its adult form, also provides evidence of relatedness between now widely divergent groups of organisms. Mutational tweaking in the embryo can have such magnified consequences in the adult that embryo formation tends to be conserved. As a result, structures that are absent in some groups often appear in their embryonic forms and disappear by the time the adult or juvenile form is reached. For example, all vertebrate embryos, including humans, exhibit gill slits and tails at some point in their early development. These disappear in the adults of terrestrial groups but are maintained in adult forms of aquatic groups such as fish and some amphibians. Great ape embryos, including humans, have a tail structure during their development that is lost by the time of birth. Biogeography 

The geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction with the movement of tectonic plates over geological time. Broad groups that evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of members of the plant family Proteaceae in Australia, southern Africa, and South America, for example, is best explained by their presence prior to the southern supercontinent Gondwana breaking up. 

The great diversification of marsupials in Australia and the absence of other mammals reflect Australia s long isolation. Australia has an abundance of endemic species species found nowhere else which is typical of islands whose isolation by expanses of water prevents species from migrating. Over time, these species diverge evolutionarily into new species that look very different from their ancestors that may exist on the mainland. The marsupials of Australia, the finches on the Gal pagos, and many species on the Hawaiian Islands are all unique to their one point of origin, yet they display distant relationships to ancestral species on mainlands. Molecular Biology 

Like anatomical structures, the structures of the molecules of life reflect descent with modification. Evidence of a common ancestor for all of life is reflected in the universality of DNA as the genetic material and in the near universality of the genetic code and the machinery of DNA replication and expression. Fundamental divisions in life between the three domains are reflected in major structural differences in otherwise conservative structures such as the components of ribosomes and the structures of membranes. In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences exactly the pattern that would be expected from descent and diversification from a common ancestor. 

DNA sequences have also shed light on some of the mechanisms of evolution. For example, it is clear that the evolution of new functions for proteins commonly occurs after gene duplication events that allow the free modification of one copy by mutation, selection, or drift (changes in a population s gene pool resulting from chance), while the second copy continues to produce a functional protein. Misconceptions of Evolution 

Although the theory of evolution generated some controversy when it was first proposed, it was almost universally accepted by biologists, particularly younger biologists, within 20 years after publication of On the Origin of Species . Nevertheless, the theory of evolution is a difficult concept and misconceptions about how it works abound. Link to Learning 

This site addresses some of the main misconceptions associated with the theory of evolution. 

[link] Evolution Is Just a Theory 

Critics of the theory of evolution dismiss its importance by purposefully confounding the everyday usage of the word theory with the way scientists use the word. In science, a theory is understood to be a body of thoroughly tested and verified explanations for a set of observations of the natural world. Scientists have a theory of the atom, a theory of gravity, and the theory of relativity, each of which describes understood facts about the world. In the same way, the theory of evolution describes facts about the living world. As such, a theory in science has survived significant efforts to discredit it by scientists. In contrast, a theory in common vernacular is a word meaning a guess or suggested explanation; this meaning is more akin to the scientific concept of hypothesis. When critics of evolution say evolution is just a theory, they are implying that there is little evidence supporting it and that it is still in the process of being rigorously tested. This is a mischaracterization. Individuals Evolve 

Evolution is the change in genetic composition of a population over time, specifically over generations, resulting from differential reproduction of individuals with certain alleles. Individuals do change over their lifetime, obviously, but this is called development and involves changes programmed by the set of genes the individual acquired at birth in coordination with the individual s environment. When thinking about the evolution of a characteristic, it is probably best to think about the change of the average value of the characteristic in the population over time. For example, when natural selection leads to bill-size change in medium-ground finches in the Gal pagos, this does not mean that individual bills on the finches are changing. If one measures the average bill size among all individuals in the population at one time and then measures the average bill size in the population several years later, this average value will be different as a result of evolution. Although some individuals may survive from the first time to the second, they will still have the same bill size; however, there will be many new individuals that contribute to the shift in average bill size. Evolution Explains the Origin of Life 

It is a common misunderstanding that evolution includes an explanation of life s origins. Conversely, some of the theory s critics believe that it cannot explain the origin of life. The theory does not try to explain the origin of life. The theory of evolution explains how populations change over time and how life diversifies the origin of species. It does not shed light on the beginnings of life including the origins of the first cells, which is how life is defined. The mechanisms of the origin of life on Earth are a particularly difficult problem because it occurred a very long time ago, and presumably it just occurred once. Importantly, biologists believe that the presence of life on Earth precludes the possibility that the events that led to life on Earth can be repeated because the intermediate stages would immediately become food for existing living things. 

However, once a mechanism of inheritance was in place in the form of a molecule like DNA either within a cell or pre-cell, these entities would be subject to the principle of natural selection. More effective reproducers would increase in frequency at the expense of inefficient reproducers. So while evolution does not explain the origin of life, it may have something to say about some of the processes operating once pre-living entities acquired certain properties. Organisms Evolve on Purpose 

Statements such as organisms evolve in response to a change in an environment are quite common, but such statements can lead to two types of misunderstandings. First, the statement must not be understood to mean that individual organisms evolve. The statement is shorthand for a population evolves in response to a changing environment. However, a second misunderstanding may arise by interpreting the statement to mean that the evolution is somehow intentional. A changed environment results in some individuals in the population, those with particular phenotypes, benefiting and therefore producing proportionately more offspring than other phenotypes. This results in change in the population if the characteristics are genetically determined. 

It is also important to understand that the variation that natural selection works on is already in a population and does not arise in response to an environmental change. For example, applying antibiotics to a population of bacteria will, over time, select a population of bacteria that are resistant to antibiotics. The resistance, which is caused by a gene, did not arise by mutation because of the application of the antibiotic. The gene for resistance was already present in the gene pool of the bacteria, likely at a low frequency. The antibiotic, which kills the bacterial cells without the resistance gene, strongly selects individuals that are resistant, since these would be the only ones that survived and divided. Experiments have demonstrated that mutations for antibiotic resistance do not arise as a result of antibiotic. 

In a larger sense, evolution is not goal directed. Species do not become better over time; they simply track their changing environment with adaptations that maximize their reproduction in a particular environment at a particular time. Evolution has no goal of making faster, bigger, more complex, or even smarter species, despite the commonness of this kind of language in popular discourse. What characteristics evolve in a species are a function of the variation present and the environment, both of which are constantly changing in a non-directional way. What trait is fit in one environment at one time may well be fatal at some point in the future. This holds equally well for a species of insect as it does the human species. Activity 

Using information from a book or online resource such as Jonathan Weiner s The Beak of the Finch , explain how contemporary evidence drawn from multiple scientific disciplines supports the observations of Charles Darwin regarding evolution by natural selection. Then, in small groups or as a whole class discussion or debate, present an argument to dispel misconceptions about evolution and how it works. Lab Investigation 

AP Biology Investigative Labs: Inquiry-Based, Investigation 8: Biotechnology: Bacterial Transformation . You will explore how genetic engineering techniques can be used to manipulate heritable information by inserting plasmids into bacterial cells. Think About It 

What selection pressures may affect the survival and reproduction of a group of pea seeds scattered by a person along the ground? The activity is an application of all of the AP Learning Objectives and Science Practices listed above because students are constructing an argument based on scientific evidence and data that support Darwin s model of evolution through natural selection. The lab investigation is an application of AP Learning Objective 1.2 and Science Practices 2.2 and 5.3, Learning Objective 1.4 and Science Practice 5.3, and Learning Objective 1.26 and Science Practice 5.3 because students are performing experiments and collecting and analyzing data to confirm that the development of resistance to antibiotics by bacteria is an example of evolution by natural selection and that evolution continues to occur. (Note: This lab investigation also connects to concepts studied in the Biotechnology chapter and is a link between genetic variation and evolution.) The Think About It question is an application of Learning Objective 1.25 and Science Practice 1.2 because students are describing a model that represents evolution within a population. Think About It sample answer: The survival and reproduction of the pea seeds would likely face selection pressure imposed by the fertility of the ground on which they land, how often the ground is disturbed (such as by people walking on it), and the amount of water and light the plants receive. Biointeractive activities, such as that found at [link] contain more evolution activities that generate population statistics which students can analyze. Section Summary 

Evolution is the process of adaptation through mutation which allows more desirable characteristics to be passed to the next generation. Over time, organisms evolve more characteristics that are beneficial to their survival. For living organisms to adapt and change to environmental pressures, genetic variation must be present. With genetic variation, individuals have differences in form and function that allow some to survive certain conditions better than others. These organisms pass their favorable traits to their offspring. Eventually, environments change, and what was once a desirable, advantageous trait may become an undesirable trait and organisms may further evolve. Evolution may be convergent with similar traits evolving in multiple species or divergent with diverse traits evolving in multiple species that came from a common ancestor. Evidence of evolution can be observed by means of DNA code and the fossil record, and also by the existence of homologous and vestigial structures. Review Questions 

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[link] Glossary adaptation heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment convergent evolution process by which groups of organisms independently evolve to similar forms divergent evolution process by which groups of organisms evolve in diverse directions from a common point homologous structures parallel structures in diverse organisms that have a common ancestor natural selection reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change variation genetic differences among individuals in a population vestigial structure physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor acquired characteristics modifications caused by an individual s environment that can be inherited by its offspring theory of evolution explains how populations change over time and how life diversifies the origin of speciesFormation of New Species Formation of New Species 

In this section, you will explore the following questions: What defines a species, and how can different species be distinguished from each other? How does genetic variation lead to speciation? What is the role of pre-zygotic and post-zygotic reproductive barriers in speciation? What is the difference between allopatric speciation and sympatric speciation? How does adaptive radiation explain the diversification? Connection for AP Courses 

Speciation explains the diversity of organisms that inhabit the Earth. Although all life shares various genetic similarities, only certain organisms combine genetic information by sexual reproduction and produce viable and fertile offspring that, in turn, can successfully reproduce. Scientists call such organisms members of a biological species. As we will study in later, changes in allele frequencies within a population over generations result in microevolution. However, macroevolution leads to the evolution of new species when populations diverge from a common ancestor and, for one reason or another, become reproductively isolated from the original population. 

Speciation occurs along two main pathways: geographic separation ( allopatric speciation ) and through mechanisms that occur within a shared habitat ( sympatric speciation ). In both cases, populations become reproductively isolated. When populations become geographically isolated, the free-flow of alleles is prevented. Over time and because of different selective pressures the populations diverge and become genetically independent species. Prezygotic barriers block reproduction prior to formation of a zygote, whereas postzygotic barriers block reproduction after fertilization occurs. Obviously, if two populations are separated by a vast ocean, they will not come in contact with each other to reproduce. However, if speciation has occurred, even when brought back together, they will retain their species identity. There are many examples of this in nature, including Darwin s finches, northern and Mexican spotted owls, and Hawaiian honeycreeper. Adaptive radiation occurs when a single ancestral species gives rise to many new species. This may occur, for example, when new habitats become available. It can also be seen historically in the rise of mammals following the extinction of dinosaurs. Other examples of prezygotic isolating mechanisms include mating seasons and unique courtship behaviors. Sometimes mating occurs between two different species, resulting in a hybrid such as the mule, which is a cross between a horse and a donkey. However, most hybrids are inviable or sterile. 

Sympatric speciation does not require a geographic barrier and explains how many different species can inhabit the same area. One form of sympatric speciation begins with a serious chromosomal error during cell division. As you recall from our exploration of meiosis, sometimes errors occur in the separation of chromosomes or chromatids, resulting in gametes with extra chromosomes ( polyploidy ). This type of speciation is more common in plants than in animals, though some examples in animals exist. For example, two groups of cichlid fish in Africa s Lake Victoria, which have distinct morphologies and diets, may be in the early stage of sympatric speciation without polyploidy, as genetic differences arise between the two groups. 

Information presented and the examples highlighted in this section support concepts outlined in Big Idea 1 and Big Idea 3 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.C Life continues to evolve within a changing environment. Essential Knowledge 1.C.1 Speciation and extinction have occurred throughout the Earth s history. Science Practice 5.1 The student can analyze data to identify patterns or relationships. Learning Objective 1.20 The student is able to analyze data related to questions of speciation and extinction throughout the Earth s history. Essential Knowledge 1.C.1 Speciation and extinction have occurred throughout the Earth s Science Practice 4.2 The student can design a plan for collecting data to answer a particular scientific question. Learning Objective 1.21 The student is able to design a plan for collecting data to investigate the scientific claim that speciation and extinction have occurred throughout the Earth s history. Essential Knowledge 1.C.2 Speciation may occur when two populations become reproductively isolated from each other. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 1.22 The student is able to use data from a real or simulated population(s), based on graphs or models of types of selection, to predict what will happen to the population in the future. Essential Knowledge 1.C.2 Speciation may occur when two populations become reproductively isolated from each other. Science Practice 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific question. Learning Objective 1.23 The student is able to justify the selection of data that address questions related to reproductive isolation and speciation. Essential Knowledge 1.C.2 Speciation may occur when two populations become reproductively isolated from each other. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 1.24 The student is able to describe speciation in an isolated population and connect it to change in gene frequency, change in environment, natural selection, and/or genetic drift. 

Big Idea 3 Living systems store, retrieve, transmit, and respond to information essential to life processes. 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.C.1 Changes in genotype can result in changes in phenotype. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. Essential Knowledge 3.C.1 Changes in genotype can result in changes in phenotype. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 3.26 The student is able to explain the connection between genetic variations in organisms and phenotypic variations in populations. 

The word species means kind in Latin. In daily life, we commonly distinguish between kinds of organisms strictly by using the criteria of appearance. Differentiating between kinds of organisms on the basis of bodily form (or morphology) is, of course, both a useful and practical thing to do. As it turns out, it is also largely in line with other means (physiological traits, biochemical patterns, and DNA sequences) of biological differentiation. 

The definition of species as a group of individuals whose members have the potential to interbreed and produce viable, fertile offspring is known as the biological species concept . Inherent in this concept of species as populations of reproductively compatible individuals is the related concept of speciation as dependent on reproductive isolation. While this definition of species depends on ideas of separateness, other definitions depend on ideas of unity. For example, the ecological species concept defines species as a set of organisms adapted to a singular niche. In the phylogenetic species concept , a species is defined as the smallest cluster of individuals within which there is a pattern of ancestry and descent. 

You may wish to ask students to research and report on different species concepts. Have students compare and contrast the different definitions. Through discussion, elicit which definitions are useful, and in what kinds of situations, and which are less useful, and in what kinds of situations. You might ask questions such as: Which definition or definitions is useful for identifying asexual species? Which definition or definitions is useful for identifying asexual and sexual species? Why might different definitions work in different environments, for different types of organisms, or at different junctures of individuals lives? Species and the Ability to Reproduce 

A species is a group of individual organisms that interbreed and produce fertile, viable offspring. According to this definition, one species is distinguished from another when, in nature, it is not possible for matings between individuals from each species to produce fertile offspring. 

Members of the same species share both external and internal characteristics, which develop from their DNA. The closer relationship two organisms share, the more DNA they have in common, just like people and their families. People s DNA is likely to be more like their father or mother s DNA than their cousin or grandparent s DNA. Organisms of the same species have the highest level of DNA alignment and therefore share characteristics and behaviors that lead to successful reproduction. 

Species appearance can be misleading in suggesting an ability or inability to mate. For example, even though domestic dogs ( Canis lupus familiaris ) display phenotypic differences, such as size, build, and coat, most dogs can interbreed and produce viable puppies that can mature and sexually reproduce ( [link] ). The (a) poodle and (b) cocker spaniel can reproduce to produce a breed known as (c) the cockapoo. (credit a: modification of work by Sally Eller, Tom Reese; credit b: modification of work by Jeremy McWilliams; credit c: modification of work by Kathleen Conklin) 

In other cases, individuals may appear similar although they are not members of the same species. For example, even though bald eagles ( Haliaeetus leucocephalus ) and African fish eagles ( Haliaeetus vocifer ) are both birds and eagles, each belongs to a separate species group ( [link] ). If humans were to artificially intervene and fertilize the egg of a bald eagle with the sperm of an African fish eagle and a chick did hatch, that offspring, called a hybrid (a cross between two species), would probably be infertile unable to successfully reproduce after it reached maturity. Different species may have different genes that are active in development; therefore, it may not be possible to develop a viable offspring with two different sets of directions. Thus, even though hybridization may take place, the two species still remain separate. The (a) African fish eagle is similar in appearance to the (b) bald eagle, but the two birds are members of different species. (credit a: modification of work by Nigel Wedge; credit b: modification of work by U.S. Fish and Wildlife Service) 

Populations of species share a gene pool: a collection of all the variants of genes in the species. Again, the basis to any changes in a group or population of organisms must be genetic for this is the only way to share and pass on traits. When variations occur within a species, they can only be passed to the next generation along two main pathways: asexual reproduction or sexual reproduction. The change will be passed on asexually simply if the reproducing cell possesses the changed trait. For the changed trait to be passed on by sexual reproduction, a gamete, such as a sperm or egg cell, must possess the changed trait. In other words, sexually-reproducing organisms can experience several genetic changes in their body cells, but if these changes do not occur in a sperm or egg cell, the changed trait will never reach the next generation. Only heritable traits can evolve. Therefore, reproduction plays a paramount role for genetic change to take root in a population or species. In short, organisms must be able to reproduce with each other to pass new traits to offspring. 

Until recently, these three species of short-tailed pythons, Python curtus, Python brongersmai (middle), and Python breitensteini were considered one species. However, due to the different locations in which they are found, they have become three distinct species. 

[link] Speciation 

The biological definition of species, which works for sexually reproducing organisms, is a group of actually or potentially interbreeding individuals. There are exceptions to this rule. Many species are similar enough that hybrid offspring are possible and may often occur in nature, but for the majority of species this rule generally holds. In fact, the presence in nature of hybrids between similar species suggests that they may have descended from a single interbreeding species, and the speciation process may not yet be complete. 

Given the extraordinary diversity of life on the planet there must be mechanisms for speciation : the formation of two species from one original species. Darwin envisioned this process as a branching event and diagrammed the process in the only illustration found in On the Origin of Species ( [link] a ). Compare this illustration to the diagram of elephant evolution ( [link] b ), which shows that as one species changes over time, it branches to form more than one new species, repeatedly, as long as the population survives or until the organism becomes extinct. The only illustration in Darwin's On the Origin of Species is (a) a diagram showing speciation events leading to biological diversity. The diagram shows similarities to phylogenetic charts that are drawn today to illustrate the relationships of species. (b) Modern elephants evolved from the Palaeomastodon , a species that lived in Egypt 35 50 million years ago. 

For speciation to occur, two new populations must be formed from one original population and they must evolve in such a way that it becomes impossible for individuals from the two new populations to interbreed. Biologists have proposed mechanisms by which this could occur that fall into two broad categories. Allopatric speciation (allo- = "other"; -patric = "homeland") involves geographic separation of populations from a parent species and subsequent evolution. Sympatric speciation (sym- = "same"; -patric = "homeland") involves speciation occurring within a parent species remaining in one location. 

Biologists think of speciation events as the splitting of one ancestral species into two descendant species. There is no reason why there might not be more than two species formed at one time except that it is less likely and multiple events can be conceptualized as single splits occurring close in time. Allopatric Speciation 

A geographically continuous population has a gene pool that is relatively homogeneous. Gene flow, the movement of alleles across the range of the species, is relatively free because individuals can move and then mate with individuals in their new location. Thus, the frequency of an allele at one end of a distribution will be similar to the frequency of the allele at the other end. When populations become geographically discontinuous, that free-flow of alleles is prevented. When that separation lasts for a period of time, the two populations are able to evolve along different trajectories. Thus, their allele frequencies at numerous genetic loci gradually become more and more different as new alleles independently arise by mutation in each population. Typically, environmental conditions, such as climate, resources, predators, and competitors for the two populations will differ causing natural selection to favor divergent adaptations in each group. 

Isolation of populations leading to allopatric speciation can occur in a variety of ways: a river forming a new branch, erosion forming a new valley, a group of organisms traveling to a new location without the ability to return, or seeds floating over the ocean to an island. The nature of the geographic separation necessary to isolate populations depends entirely on the biology of the organism and its potential for dispersal. If two flying insect populations took up residence in separate nearby valleys, chances are, individuals from each population would fly back and forth continuing gene flow. However, if two rodent populations became divided by the formation of a new lake, continued gene flow would be unlikely; therefore, speciation would be more likely. 

Biologists group allopatric processes into two categories: dispersal and vicariance. Dispersal is when a few members of a species move to a new geographical area, and vicariance is when a natural situation arises to physically divide organisms. 

Scientists have documented numerous cases of allopatric speciation taking place. For example, along the west coast of the United States, two separate sub-species of spotted owls exist. The northern spotted owl has genetic and phenotypic differences from its close relative: the Mexican spotted owl, which lives in the south ( [link] ). The northern spotted owl and the Mexican spotted owl inhabit geographically separate locations with different climates and ecosystems. The owl is an example of allopatric speciation. (credit "northern spotted owl": modification of work by John and Karen Hollingsworth; credit "Mexican spotted owl": modification of work by Bill Radke) 

Additionally, scientists have found that the farther the distance between two groups that once were the same species, the more likely it is that speciation will occur. This seems logical because as the distance increases, the various environmental factors would likely have less in common than locations in close proximity. Consider the two owls: in the north, the climate is cooler than in the south; the types of organisms in each ecosystem differ, as do their behaviors and habits; also, the hunting habits and prey choices of the southern owls vary from the northern owls. These variances can lead to evolved differences in the owls, and speciation likely will occur. Adaptive Radiation 

In some cases, a population of one species disperses throughout an area, and each population finds a distinct niche or isolated habitat. Over time, the varied demands of their new lifestyles lead to multiple speciation events originating from a single species. This is called adaptive radiation because many adaptations evolve from a single point of origin; thus, causing the species to radiate into several new ones. Island archipelagos like the Hawaiian Islands provide an ideal context for adaptive radiation events because water surrounds each island which leads to geographical isolation for many organisms. The Hawaiian honeycreeper illustrates one example of adaptive radiation. From a single species, called the founder species, numerous species have evolved, including the six shown in [link] . The honeycreeper birds illustrate adaptive radiation. From one original species of bird, multiple others evolved, each with its own distinctive characteristics. 

Notice the differences in the species beaks in [link] . Evolution in response to natural selection based on specific food sources in each new habitat led to evolution of a different beak suited to the specific food source. The seed-eating bird has a thicker, stronger beak which is suited to break hard nuts. The nectar-eating birds have long beaks to dip into flowers to reach the nectar. The insect-eating birds have beaks like swords, appropriate for stabbing and impaling insects. Darwin s finches are another example of adaptive radiation in an archipelago. Link to Learning 

Click through this interactive site to see how island birds evolved in evolutionary increments from 5 million years ago to today. 

[link] Sympatric Speciation 

Can divergence occur if no physical barriers are in place to separate individuals who continue to live and reproduce in the same habitat? The answer is yes. The process of speciation within the same space is called sympatric speciation; the prefix sym means same, so sympatric means same homeland in contrast to allopatric meaning other homeland. A number of mechanisms for sympatric speciation have been proposed and studied. 

One form of sympatric speciation can begin with a serious chromosomal error during cell division. In a normal cell division event chromosomes replicate, pair up, and then separate so that each new cell has the same number of chromosomes. However, sometimes the pairs separate and the end cell product has too many or too few individual chromosomes in a condition called aneuploidy ( [link] ). Visual Connection Aneuploidy results when the gametes have too many or too few chromosomes due to nondisjunction during meiosis. In the example shown here, the resulting offspring will have 2 n +1 or 2 n -1 chromosomes 

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Polyploidy is a condition in which a cell or organism has an extra set, or sets, of chromosomes. Scientists have identified two main types of polyploidy that can lead to reproductive isolation of an individual in the polyploidy state. Reproductive isolation is the inability to interbreed. In some cases, a polyploid individual will have two or more complete sets of chromosomes from its own species in a condition called autopolyploidy ( [link] ). The prefix auto- means self, so the term means multiple chromosomes from one s own species. Polyploidy results from an error in meiosis in which all of the chromosomes move into one cell instead of separating. Autopolyploidy results when mitosis is not followed by cytokinesis. 

For example, if a plant species with 2 n = 6 produces autopolyploid gametes that are also diploid (2 n = 6, when they should be n = 3), the gametes now have twice as many chromosomes as they should have. These new gametes will be incompatible with the normal gametes produced by this plant species. However, they could either self-pollinate or reproduce with other autopolyploid plants with gametes having the same diploid number. In this way, sympatric speciation can occur quickly by forming offspring with 4 n called a tetraploid. These individuals would immediately be able to reproduce only with those of this new kind and not those of the ancestral species. 

The other form of polyploidy occurs when individuals of two different species reproduce to form a viable offspring called an allopolyploid . The prefix allo- means other (recall from allopatric): therefore, an allopolyploid occurs when gametes from two different species combine. [link] illustrates one possible way an allopolyploid can form. Notice how it takes two generations, or two reproductive acts, before the viable fertile hybrid results. Alloploidy results when two species mate to produce viable offspring. In the example shown, a normal gamete from one species fuses with a polyploidy gamete from another. Two matings are necessary to produce viable offspring. 

The cultivated forms of wheat, cotton, and tobacco plants are all allopolyploids. Although polyploidy occurs occasionally in animals, it takes place most commonly in plants. (Animals with any of the types of chromosomal aberrations described here are unlikely to survive and produce normal offspring.) Scientists have discovered more than half of all plant species studied relate back to a species evolved through polyploidy. With such a high rate of polyploidy in plants, some scientists hypothesize that this mechanism takes place more as an adaptation than as an error. Activity 

Create a visual representation such as a diagram with annotation to explain how island chains provide ideal conditions for allopatric speciation and adaptive radiation to occur. Then design a plan for collecting data to support the claim that speciation has occurred. Think About It Two species of fish had recently undergone sympatric speciation. The males of each species had a different coloring through which the females could identify and choose a partner from her own species. After some time, pollution made the lake so cloudy that it was hard for females to distinguish colors. What might take place in this situation? In a lake where most fish of a single species exhibit colorful stripes, a few individual animals have muted colors. The local fisherman receives a large order to catch the most colorful fish for a local aquarium store. The fisherman casts wide nets across the lake to catch a large number of the fish. He then keeps the colorful fish for the aquarium and throws back the dull colored fish. How will this single event change the make-up of the fish population? This activity is an application of AP Learning Objective 1.21 and Science Practice 4.2 because students are designing a plan to support the claim that islands provide the ideal conditions for allopatric speciation and adaptive radiation. The first Think About It question is an application of AP Learning Objective 1.22 and Science Practice 6.4 because students are making a prediction based on observations and a model of natural selection. Students also address questions relating to reproductive isolation and speciation (Learning Objective 1.23 and Science Practice 4.1). In the case of the first Think About It question, the females will likely attempt to breed with members of both species. However, because the two species can no longer interbreed, only females that mate with males of the same species will have offspring. This may eventually drive the evolution of other distinguishing traits, such as chemical signals, so that females can better identify males of their own species. The second Think About It question is an application of AP Learning Objective 1.24 and Science Practice 6.4 because students are making a prediction based on observations and a model of natural selection. In the second Think About It question, the gene frequency here will be modified as a consequence of a random event which drastically changes the composition of the population and is an example of genetic drift and the bottle-neck effect. The fish in the lake represent an isolated population on which genetic drift will act rapidly. Reproductive Isolation 

Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were to be brought together, mating would be less likely, but if mating occurred, offspring would be non-viable or infertile. Many types of diverging characters may affect the reproductive isolation (the inability to interbreed) of the two populations. 

Reproductive isolation can take place in a variety of ways. Scientists organize them into two groups: prezygotic barriers and postzygotic barriers. Recall that a zygote is a fertilized egg: the first cell of the development of an organism that reproduces sexually. Therefore, a prezygotic barrier is a mechanism that blocks reproduction from taking place; this includes barriers that prevent fertilization when organisms attempt reproduction. A postzygotic barrier occurs after zygote formation; this includes organisms that don t survive the embryonic stage and those that are born sterile. 

Some types of prezygotic barriers prevent reproduction entirely. Many organisms only reproduce at certain times of the year, often just annually. Differences in breeding schedules, called temporal isolation , can act as a form of reproductive isolation. For example, two species of frogs inhabit the same area, but one reproduces from January to March, whereas the other reproduces from March to May ( [link] ). These two related frog species exhibit temporal reproductive isolation. (a) Rana aurora breeds earlier in the year than (b) Rana boylii . (credit a: modification of work by Mark R. Jennings, USFWS; credit b: modification of work by Alessandro Catenazzi) 

In some cases, populations of a species move or are moved to a new habitat and take up residence in a place that no longer overlaps with the other populations of the same species. This situation is called habitat isolation . Reproduction with the parent species ceases, and a new group exists that is now reproductively and genetically independent. For example, a cricket population that was divided after a flood could no longer interact with each other. Over time, the forces of natural selection, mutation, and genetic drift will likely result in the divergence of the two groups ( [link] ). Speciation can occur when two populations occupy different habitats. The habitats need not be far apart. The cricket (a) Gryllus pennsylvanicus prefers sandy soil, and the cricket (b) Gryllus firmus prefers loamy soil. The two species can live in close proximity, but because of their different soil preferences, they became genetically isolated. 

Behavioral isolation occurs when the presence or absence of a specific behavior prevents reproduction from taking place. For example, male fireflies use specific light patterns to attract females. Various species of fireflies display their lights differently. If a male of one species tried to attract the female of another, she would not recognize the light pattern and would not mate with the male. 

Other prezygotic barriers work when differences in their gamete cells (eggs and sperm) prevent fertilization from taking place; this is called a gametic barrier . Similarly, in some cases closely related organisms try to mate, but their reproductive structures simply do not fit together. For example, damselfly males and females of different species have differently shaped reproductive organs. If one species tries to mate with another, their body parts simply do not fit together. ( [link] ). The shape of the male reproductive organ varies among male damselfly species, and is only compatible with the female of the same species. Reproductive organ incompatibility keeps each species reproductively isolated. 

In plants, certain structures aimed to attract one type of pollinator simultaneously prevent a different pollinator from accessing the pollen. The tunnel through which an animal must access nectar can vary widely in length and diameter, which prevents the plant from being cross-pollinated with a different species ( [link] ). Some flowers have evolved to attract certain pollinators. The (a) wide foxglove flower is adapted for pollination by bees, while the (b) long, tube-shaped trumpet creeper flower is adapted for pollination by humming birds. 

When fertilization takes place and a zygote forms, postzygotic barriers can prevent reproduction. Hybrid individuals in many cases cannot form normally in the womb and simply do not survive past the embryonic stages. This is called hybrid inviability because the hybrid organisms simply are not viable. In another postzygotic situation, reproduction leads to the birth and growth of a hybrid that is sterile and unable to reproduce offspring of their own; this is called hybrid sterility. Habitat Influence on Speciation 

Sympatric speciation may also take place in ways other than polyploidy. For example, consider a species of fish that lives in a lake. As the population grows, competition for food also grows. Under pressure to find food, suppose that a group of these fish had the genetic flexibility to discover and feed off another resource that was unused by the other fish. What if this new food source was found at a different depth of the lake? Over time, those feeding on the second food source would interact more with each other than the other fish; therefore, they would breed together as well. Offspring of these fish would likely behave as their parents: feeding and living in the same area and keeping separate from the original population. If this group of fish continued to remain separate from the first population, eventually sympatric speciation might occur as more genetic differences accumulated between them. 

This scenario does play out in nature, as do others that lead to reproductive isolation. One such place is Lake Victoria in Africa, famous for its sympatric speciation of cichlid fish. Researchers have found hundreds of sympatric speciation events in these fish, which have not only happened in great number, but also over a short period of time. [link] shows this type of speciation among a cichlid fish population in Nicaragua. In this locale, two types of cichlids live in the same geographic location but have come to have different morphologies that allow them to eat various food sources. Cichlid fish from Lake Apoyeque, Nicaragua, show evidence of sympatric speciation. Lake Apoyeque, a crater lake, is 1800 years old, but genetic evidence indicates that the lake was populated only 100 years ago by a single population of cichlid fish. Nevertheless, two populations with distinct morphologies and diets now exist in the lake, and scientists believe these populations may be in an early stage of speciation. Section Summary 

Speciation occurs along two main pathways: geographic separation (allopatric speciation) and through mechanisms that occur within a shared habitat (sympatric speciation). Both pathways isolate a population reproductively in some form. Mechanisms of reproductive isolation act as barriers between closely related species, enabling them to diverge and exist as genetically independent species. Prezygotic barriers block reproduction prior to formation of a zygote, whereas postzygotic barriers block reproduction after fertilization occurs. For a new species to develop, something must cause a breach in the reproductive barriers. Sympatric speciation can occur through errors in meiosis that form gametes with extra chromosomes (polyploidy). Autopolyploidy occurs within a single species, whereas allopolyploidy occurs between closely related species. Review Questions 

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[link] Glossary adaptive radiation speciation when one species radiates out to form several other species allopatric speciation speciation that occurs via geographic separation allopolyploid polyploidy formed between two related, but separate species aneuploidy condition of a cell having an extra chromosome or missing a chromosome for its species autopolyploid polyploidy formed within a single species behavioral isolation type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place dispersal allopatric speciation that occurs when a few members of a species move to a new geographical area gametic barrier prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place habitat isolation reproductive isolation resulting when populations of a species move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the other populations of the same species hybrid offspring of two closely related individuals, not of the same species postzygotic barrier reproductive isolation mechanism that occurs after zygote formation prezygotic barrier reproductive isolation mechanism that occurs before zygote formation reproductive isolation situation that occurs when a species is reproductively independent from other species; this may be brought about by behavior, location, or reproductive barriers speciation formation of a new species species group of populations that interbreed and produce fertile offspring sympatric speciation speciation that occurs in the same geographic space temporal isolation differences in breeding schedules that can act as a form of prezygotic barrier leading to reproductive isolation vicariance allopatric speciation that occurs when something in the environment separates organisms of the same species into separate groups polyploidy gametes with extra chromosomesReconnection and Rates of Speciation Reconnection and Rates of Speciation 

In this section, you will explore the following questions: What are the pathways of species evolution in hybrid zones? What are the two major theories on rates of speciation? Connection for AP Courses 

Speciation can both occur gradually over time in small steps or in bursts of change known as punctuated equilibrium. With punctuated equilibrium, a species may remain unchanged for long periods of time. The primary influencing factor on changes in speciation rate is environmental change. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.C Life continues to evolve within a changing environment. Essential Knowledge 1.C.1 Speciation and extinction have occurred throughout Earth s history. Science Practice 5.1 The student can analyze data to identify patterns or relationships. Learning Objective 1.20 The student is able to analyze data related to questions of speciation and extinction throughout the Earth s history. 

Hybrid zones provide scientists with spaces from which to research the factors that cause reproductive isolation, and thus, speciation. The spatial patterns of hybrid zones reveal much about these factors and allow for inferences to be made about the number and degree of obstacles to gene flow as well as the number and types of contacts between species. 

You may wish to identify for students examples of hybrid zones, or encourage them to research zones for themselves. Pose questions to students about why hybrid zones might be viewed a natural experiments in which to study the process of speciation. Encourage them to compare and contrast the information they find about different hybrid zones. Have them consider what questions they might ask about the species in the zones and what information they might expect to gain from asking them. 

Speciation occurs over a span of evolutionary time, so when a new species arises, there is a transition period during which the closely related species continue to interact. Reconnection 

After speciation, two species may continue interacting indefinitely or even recombine. Individual organisms will mate with any nearby individual who they are capable of breeding with. An area where two closely related species continue to interact and reproduce, forming hybrids, is called a hybrid zone . Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers ( [link] ). If the hybrids are less fit than the parents, reinforcement of speciation occurs, and the species continue to diverge until they can no longer mate and produce viable offspring. If reproductive barriers weaken, fusion occurs and the two species become one. Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues. Visual Connection After speciation has occurred, the two separate but closely related species may continue to produce offspring in an area called the hybrid zone. Reinforcement, fusion, or stability may result, depending on reproductive barriers and the relative fitness of the hybrids. 

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Hybrids can be either less fit than the parents, more fit, or about the same. Usually hybrids tend to be less fit; therefore, such reproduction diminishes over time, nudging the two species to diverge further in a process called reinforcement . This term is used because the low success of the hybrids reinforces the original speciation. If the hybrids are as fit or more fit than the parents, the two species may fuse back into one species ( [link] ). Scientists have also observed that sometimes two species will remain separate but also continue to interact to produce some hybrid individuals; this is classified as stability because no real net change is taking place. Varying Rates of Speciation 

Scientists around the world study speciation, documenting observations both of living organisms and those found in the fossil record. As their ideas take shape and as research reveals new details about how life evolves, they develop models to help explain rates of speciation. In terms of how quickly speciation occurs, two patterns are currently observed: gradual speciation model and punctuated equilibrium model. 

In the gradual speciation model , species diverge gradually over time in small steps. In the punctuated equilibrium model, a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward ( [link] ). This early change model is called punctuated equilibrium, because it begins with a punctuated or periodic change and then remains in balance afterward. While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism. Visual Connection In (a) gradual speciation, species diverge at a slow, steady pace as traits change incrementally. In (b) punctuated equilibrium, species diverge quickly and then remain unchanged for long periods of time. 

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The primary influencing factor on changes in speciation rate is environmental conditions. Under some conditions, selection occurs quickly or radically. Consider a species of snails that had been living with the same basic form for many thousands of years. Layers of their fossils would appear similar for a long time. When a change in the environment takes place such as a drop in the water level a small number of organisms are separated from the rest in a brief period of time, essentially forming one large and one tiny population. The tiny population faces new environmental conditions. Because its gene pool quickly became so small, any variation that surfaces and that aids in surviving the new conditions becomes the predominant form. Link to Learning 

Visit this website to continue the speciation story of the snails. 

[link] Section Summary 

Speciation is not a precise division: overlap between closely related species can occur in areas called hybrid zones. Organisms reproduce with other similar organisms. The fitness of these hybrid offspring can affect the evolutionary path of the two species. Scientists propose two models for the rate of speciation: one model illustrates how a species can change slowly over time; the other model demonstrates how change can occur quickly from a parent generation to a new species. Both models continue to follow the patterns of natural selection. Review Questions 

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[link] Glossary gradual speciation model model that shows how species diverge gradually over time in small steps hybrid zone area where two closely related species continue to interact and reproduce, forming hybrids punctuated equilibrium model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population reinforcement continued speciation divergence between two related species due to low fitness of hybrids between themIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" Living things may be single-celled or complex, multicellular organisms. They may be plants, animals, fungi, bacteria, or archaea. This diversity results from evolution. (credit "wolf": modification of work by Gary Kramer; credit "coral": modification of work by William Harrigan, NOAA; credit "river": modification of work by Vojt ch Dost l; credit "fish" modification of work by Christian Mehlf hrer; credit "mushroom": modification of work by Cory Zanker; credit "tree": modification of work by Joseph Kranak; credit "bee": modification of work by Cory Zanker) 

Evolutionary medicine is an emerging field that applies evolutionary theory to modern medicine. Rather than just seeking answers to how illness occurs, evolutionary medicine also asks why illness occurs. This approach to medicine has led to many important advances. For example, endogenous retroviruses (ERVs) are pieces of retroviruses that began invading mammalian genomes over 100 million years ago. While studying why smaller mammals tend to get cancer more frequently than larger mammals, scientists discovered that larger mammals have had fewer ERVs invade their genome. Because retroviral integration is associated with cancer, results from this research suggest the possibility that larger mammals are able to control EVR replication until they reach post-reproductive age. 1 More on this research can be found on the PLOS Pathogens website . Footnotes 1 Katzourakis A, Magiorkinis G, Lim AG, Gupta S, Belshaw R, et al. (2014) Larger Mammalian Body Size Leads to Lower Retroviral Activity. PLoS Pathog10(7): e1004214. doi: 10.1371/journal.ppat.1004214Population Evolution Population Evolution 

In this section, you will explore the following questions: What is population genetics and how is population genetics a synthesis of Mendelian inheritance and Darwinian evolution? What is the Hardy Weinberg principle, and how can it be applied to microevolution? 

The mechanisms of inheritance, or genetics, were not understood at the time Charles Darwin and Alfred Russel Wallace were developing their idea of natural selection. This lack of understanding was a stumbling block to understanding many aspects of evolution. In fact, the predominant (and incorrect) genetic theory of the time, blending inheritance, made it difficult to understand how natural selection might operate. Darwin and Wallace were unaware of the genetics work by Austrian monk Gregor Mendel, which was published in 1866, not long after publication of Darwin's book, On the Origin of Species . Mendel s work was rediscovered in the early twentieth century at which time geneticists were rapidly coming to an understanding of the basics of inheritance. Initially, the newly discovered particulate nature of genes made it difficult for biologists to understand how gradual evolution could occur. But over the next few decades genetics and evolution were integrated in what became known as the modern synthesis the coherent understanding of the relationship between natural selection and genetics that took shape by the 1940s and is generally accepted today. In sum, the modern synthesis describes how evolutionary processes, such as natural selection, can affect a population s genetic makeup, and, in turn, how this can result in the gradual evolution of populations and species. The theory also connects this change of a population over time, called microevolution , with the processes that gave rise to new species and higher taxonomic groups with widely divergent characters, called macroevolution . Connection for AP Courses 

Population genetics studies microevolution by measuring changes in a population s allele frequencies over time. (Remember that we studied genotypes and allele frequencies when we explored inheritance patterns proposed by Mendel.) For example, scientists examining allele frequencies in a pesticide resistance gene in mosquitoes at Equatorial Guinea found that the frequency of one resistance allele was 6.3%, while a second resistance allele s frequency was 74.6%, and the non-resistance allele s frequency was 19.0%. These three frequencies add up to 100%. 1 A population s gene pool is the sum of all the alleles. If these frequencies do not change over time, the population is said to be in Hardy Weinberg principle of equilibrium a stable, non-evolving state. However, if a phenotype is favored by natural selection, allele frequencies can change. If this is the case, the population is evolving. Sometimes allele frequencies within a population change randomly with no advantage to the population over existing allele frequencies. This phenomenon is called genetic drift . An event that initiates an allele frequency change in an isolated part of the population, which is not typical of the original population, is called the founder effect . In Population Genetics , we will explore how natural selection, random drift, and founder effects can lead to significant changes in the genome of a population. 

Hardy Weinberg equilibrium reflects a state of constancy in a population s gene pool. In other words, allele frequencies remain stable from generation to generation if certain conditions are met: no mutations, no gene flow, random mating, no genetic drift, and no selection. Because these conditions are rarely met, allele frequencies are typically changing, reflecting evolution. The Hardy Weinberg principle is represented by the mathematical equation p 2 + 2pq + q 2 = 1 , where p represents the frequency of the dominant allele and q represents the frequency of the recessive allele. Deviations from Hardy Weinberg equilibrium allow us to measure microevolutionary shifts in a population when one or more of the Hardy Weinberg parameters change. For example, if we go back to the study of the frequencies of alleles in a pesticide resistance gene, after an area was treated with pesticides for two years, the resistance alleles increased to 11.1% and 83.3%, respectively, while the non-resistance allele decreased to 5.6%. This indicates that microevolution was occurring. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1: The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.A Change in the genetic makeup of a population over time is evolution. Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 1.5 The student can re-express key elements of natural phenomena across multiple representations in the domain. Science Practice 1.1 The student is able to convert a data set from a table of numbers that reflect a change in the genetic makeup of a population over time and to apply mathematical methods and conceptual understandings to investigate the cause(s) and effect(s) of this change. Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 1.2 The student is able to evaluate evidence provided by data to qualitatively and quantitatively investigate the role of natural selection in evolution. Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.3 The student is able to apply mathematical methods to data from a real or simulated population to predict what will happen to the population in the future. 

A good video tutorial by Bozeman on Hardy Weinberg can be found here . 

Evolution and Flu Vaccines Every fall, the media starts reporting on flu vaccinations and potential outbreaks. Scientists, health experts, and institutions determine recommendations for different parts of the population, predict optimal production and inoculation schedules, create vaccines, and set up clinics to provide inoculations. You may think of the annual flu shot as a lot of media hype, an important health protection, or just a briefly uncomfortable prick in your arm. But do you think of it in terms of evolution? 

The media hype of annual flu shots is scientifically grounded in our understanding of evolution. Each year, scientists across the globe strive to predict the flu strains that they anticipate being most widespread and harmful in the coming year. This knowledge is based in how flu strains have evolved over time and over the past few flu seasons. Scientists then work to create the most effective vaccine to combat those selected strains. Hundreds of millions of doses are produced in a short period in order to provide vaccinations to key populations at the optimal time. 

Because viruses, like the flu, evolve very quickly (especially in evolutionary time), this poses quite a challenge. Viruses mutate and replicate at a fast rate, so the vaccine developed to protect against last year s flu strain may not provide the protection needed against the coming year s strain. Evolution of these viruses means continued adaptions to ensure survival, including adaptations to survive previous vaccines. 

[link] Population Genetics 

Recall that a gene for a particular character may have several alleles, or variants, that code for different traits associated with that character. For example, in the ABO blood type system in humans, three alleles determine the particular blood-type protein on the surface of red blood cells. Each individual in a population of diploid organisms can only carry two alleles for a particular gene, but more than two may be present in the individuals that make up the population. Mendel followed alleles as they were inherited from parent to offspring. In the early twentieth century, biologists in a field of study known as population genetics began to study how selective forces change a population through changes in allele and genotypic frequencies. 

The allele frequency (or gene frequency) is the proportion of a specific allele within a population, relative to all other alleles of that gene that are present in the population. Until now we have discussed evolution as a change in the characteristics of a population of organisms, but behind that phenotypic change is genetic change. In population genetics, the term evolution is defined as a change in the frequency of an allele in a population. Using the ABO blood type system as an example, the frequency of one of the alleles, I A , is the number of copies of that allele divided by all the copies of the ABO gene in the population. For example, a study in Jordan 2 found a frequency of I A to be 26.1 percent. The I B and I 0 alleles made up 13.4 percent and 60.5 percent of the alleles respectively, and all of the frequencies added up to 100 percent. A change in this frequency over time would constitute evolution in the population. 

The allele frequency within a given population can change depending on environmental factors; therefore, certain alleles become more widespread than others during the process of natural selection. Natural selection can alter the population s genetic makeup; for example, if a given allele confers a phenotype that allows an individual to better survive or have more offspring. Because many of those offspring will also carry the beneficial allele, and often the corresponding phenotype, they will have more offspring of their own that also carry the allele, thus, perpetuating the cycle. Over time, the allele will spread throughout the population. Some alleles will quickly become fixed in this way, meaning that every individual of the population will carry the allele, while detrimental mutations may be swiftly eliminated if derived from a dominant allele from the gene pool. The gene pool is the sum of all the alleles in a population. 

Sometimes, allele frequencies within a population change randomly with no advantage to the population over existing allele frequencies. This phenomenon is called genetic drift. Natural selection and genetic drift usually occur simultaneously in populations and are not isolated events. It is hard to determine which process dominates because it is often nearly impossible to determine the cause of change in allele frequencies at each occurrence. An event that initiates an allele frequency change in an isolated part of the population, which is not typical of the original population, is called the founder effect. Natural selection, random drift, and founder effects can lead to significant changes in the genome of a population. Hardy Weinberg Principle of Equilibrium 

In the early twentieth century, English mathematician Godfrey Hardy and German physician Wilhelm Weinberg stated the principle of equilibrium to describe the genetic makeup of a population. The theory, which later became known as the Hardy Weinberg principle of equilibrium, states that a population s allele and genotype frequencies are inherently stable unless some kind of evolutionary force is acting upon the population, neither the allele nor the genotypic frequencies would change. The Hardy Weinberg principle assumes conditions with no mutations, migration, emigration, or selective pressure for or against genotype, plus an infinite population; while no population can satisfy those conditions, the principle offers a useful model against which to compare real population changes. 

Working under this theory, population geneticists represent different alleles as different variables in their mathematical models. The variable p, for example, typically represents the frequency of the dominant allele, say Y for the trait of yellow in Mendel's peas. The variable q represents the frequency of the recessive allele, in this case y, that confers the color green. If these are the only two possible alleles for a given locus in the population, p + q = 1. In other words, all the p alleles and all the q alleles make up all of the alleles for that locus that are found in the population. 

But what ultimately interests most biologists is not the frequencies of different alleles, but the frequencies of the resulting genotypes, known as the population s genetic structure , from which scientists can surmise the distribution of phenotypes. If the phenotype is observed, only the genotype of the homozygous recessive alleles can be known; the calculations provide an estimate of the remaining genotypes. Since each individual carries two alleles per gene, if the allele frequencies (p and q) are known, predicting the frequencies of these genotypes is a simple mathematical calculation to determine the probability of getting these genotypes if two alleles are drawn at random from the gene pool. So in the above scenario, an individual pea plant could be pp (YY), and thus produce yellow peas; pq (Yy), also yellow; or qq (yy), and thus producing green peas ( [link] ). In other words, the frequency of pp individuals is simply p 2 ; the frequency of pq individuals is 2pq; and the frequency of qq individuals is q 2 . And, again, if p and q are the only two possible alleles for a given trait in the population, these genotypes frequencies will sum to one: p 2 + 2pq + q 2 = 1. 

When populations are in the Hardy Weinberg equilibrium, the allelic frequency is stable from generation to generation and the distribution of alleles can be determined from the Hardy Weinberg equation. If the allelic frequency measured in the field differs from the predicted value, scientists can make inferences about what evolutionary forces are at play. 

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In theory, if a population is at equilibrium that is, there are no evolutionary forces acting upon it generation after generation would have the same gene pool and genetic structure, and these equations would all hold true all of the time. Of course, even Hardy and Weinberg recognized that no natural population is immune to evolution. Populations in nature are constantly changing in genetic makeup due to drift, mutation, possibly migration, and selection. As a result, the only way to determine the exact distribution of phenotypes in a population is to go out and count them. But the Hardy Weinberg principle gives scientists a mathematical baseline of a non-evolving population to which they can compare evolving populations and thereby infer what evolutionary forces might be at play. If the frequencies of alleles or genotypes deviate from the value expected from the Hardy Weinberg equation, then the population is evolving. 

Use this online calculator to determine the genetic structure of a population. 

[link] Lab Investigation 

AP Biology Investigative Labs: Inquiry-Based Approach, Investigation 2: Mathematical Modeling: Hardy Weinberg . In this lab investigation, you apply the Hardy Weinberg equation and create a spreadsheet to study changes in allele frequencies in a population and to examine possible causes for these changes. Think About It 

Imagine you are trying to determine if a population of flowers is undergoing microevolution. You suspect there is selection pressure on the color of the flower because bees seem to cluster around red flowers more often than blue flowers. In a separate experiment, you discover that blue flower color is dominant to red flower color. In a field, you count 600 blue flowers and 200 red flowers. Based on the H-W equation, what are the expected allele frequencies for flower color? 

Two years later, you revisit the same field and discover that out of 1,000 flowers, 650 are blue. Use the H W equation to determine if the population of flowers is undergoing evolution. This lab investigation is an application of AP Learning Objective 1.1 and Science Practices 1.5 and 2.2, Learning Objective 1.2 and Science Practices 2.2 and 5.3, and Learning Objective 1.3 and Science Practice 2.2 because students are analyzing data sets and applying the Hardy Weinberg equation to calculate allele frequencies and determine if a population if evolving based on changes in allele frequencies. For additional interactive programs and tutorials to aid students in understanding allelles, go to this website . Think About It Answers: In the first example, 200 out of 800 flowers had the recessive homozygous phenotype. The q2=0.25 and thus the frequency of q = 0.5. Since p + q = 1, the frequency of p is also 0.5. In the second example, using the same math, the frequency of p is 0.57 and q is 0.43, so it is clear that the allelic frequencies are changing and that the populations is indeed undergoing natural selection. The Think About It questions are applications of AP Learning Objective 1.1 and Science Practices 1.5 and 2.2, Learning Objective 1.2 and Science Practices 2.2 and 5.3, and Learning Objective 1.3 and Science Practice 2.2 because students are applying the Hardy Weinberg equation to data sets and using calculated allele frequencies to determine if a population is evolving. Section Summary 

The modern synthesis of evolutionary theory grew out of the cohesion of Darwin s, Wallace s, and Mendel s thoughts on evolution and heredity, along with the more modern study of population genetics. It describes the evolution of populations and species, from small-scale changes among individuals to large-scale changes over paleontological time periods. To understand how organisms evolve, scientists can track populations allele frequencies over time. If they differ from generation to generation, scientists can conclude that the population is not in Hardy Weinberg equilibrium, and is thus evolving. Review Questions 

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[link] Footnotes 1 Reddy, M. R., Godoy, A., Dion, K., Matias, A., Callender, K., Kiszewski, A. E., Slotman, M. A. (2013). Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea. The American Journal of Tropical Medicine and Hygiene, 88 (5), 897 907. doi:10.4269/ajtmh.12-0467 2 Sahar S. Hanania, Dhia S. Hassawi, and Nidal M. Irshaid, Allele Frequency and Molecular Genotypes of ABO Blood Group System in a Jordanian Population, Journal of Medical Sciences 7 (2007): 51-58, doi:10.3923/jms.2007.51.58. Glossary allele frequency (also, gene frequency) rate at which a specific allele appears within a population founder effect event that initiates an allele frequency change in part of the population, which is not typical of the original population gene pool all of the alleles carried by all of the individuals in the population genetic structure distribution of the different possible genotypes in a population macroevolution broader scale evolutionary changes seen over paleontological time microevolution changes in a population s genetic structure modern synthesis overarching evolutionary paradigm that took shape by the 1940s and is generally accepted today population genetics study of how selective forces change the allele frequencies in a population over time Hardy Weinberg principle of equilibrium a stable, non-evolving state of a population in which allelic frequencies are stable over time genotype frequency the proportion of a specific genotype in a population relative to all other genotypes for those genes that are present in the populationPopulation Genetics Population Genetics 

In this section, you will explore the following questions: What are the different types of variation in a population? Why can only heritable variation be acted upon by natural selection? How can genetic drift, the bottleneck effect, and the founder effect influence allele frequencies in a population? How can gene flow, mutation, nonrandom mating, and environmental variance affect allele frequencies in a population? Connection for AP Courses 

Take a look at your classmates. Individuals of a population often display different phenotypes, or express different alleles of a particular gene. These differences are called polymorphisms . The distribution of phenotypes among individuals, known as population variation , is influenced by several factors, including the population s genetic structure and the environment ( [link] ). Understanding the sources of phenotypic variation is important for determining how a population will evolve in response to different evolutionary pressures. Only those variations that are encoded in an individual s genes can be passed to its offspring and be a target of natural selection. The distribution of phenotypes in this litter of kittens illustrates population variation. (credit: Pieter Lanser) 

As you learn in the chapter that discusses the evolution and origin of species, natural selection works by selecting for phenotypes and the alleles that determine them that confer beneficial traits or behaviors. Deleterious qualities are selected against. Genetic drift stems from the chance occurrence that some individuals have more offspring than others and, thus, will pass on more of their genes to the next generation. Small and isolated populations are more susceptible to genetic drift. Natural events, such as wildfires or hurricanes, can magnify genetic drift when a large portion of the population is killed. Because a fire does not distinguish between the genotypes of various organisms, no particular genotype survives the fire better than another. Therefore, the genetic structure of the surviving population may be very different from the genetic structure of the original population. This is called the bottleneck effect. Another scenario in which populations might experience a strong influence of genetic drift occurs when some portion of the population leaves to start a new population in a new location or gets separated by a physical barrier of some kind. In this situation, those individuals are unlikely to be representative of the entire population, a phenomenon called the founder effect. Both the bottleneck effect and the founder effect reduce genetic variation within a population and genetic variation is the basis for natural selection. When individuals leave or join a population, they carry their alleles with them, resulting in changes in the population s allele frequencies. Allele frequencies also can change due to mutation in DNA and when individuals do not randomly mate with others; when an individual selects a mate based on phenotype, the genotype is also selected. In summary, any of these conditions can result in deviations from the Hardy Weinberg equilibrium and lead to the microevolution of a population. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1: The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.A Change in the genetic makeup of a population over time is evolution. Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Learning Objective 1.2 The student is able to evaluate evidence provided by data to qualitatively and quantitatively investigate the role of natural selection in evolution. Essential Knowledge 1.A.2 Natural selection acts on phenotypic variations in populations. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 1.3 The student is able to apply mathematical methods to data from a real or simulated population to predict what will happen to the population in the future. Essential Knowledge 1.A.2 Natural selection acts on phenotypic variations in populations. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.4 The student is able to evaluate data-based evidence that describes evolutionary changes in the genetic makeup of a population over time. Essential Knowledge 1.A.3 Evolutionary change is also driven by random processes. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Learning Objective 1.8 The student is able to make predictions about the effects of genetic drift, migration, and artificial selection on the genetic makeup of a population. Essential Knowledge 1.A.3 Evolutionary change is also driven by random processes. Science Practice 1.4 The student can use representatives and models to analyze situations or solve problems qualitatively and quantitatively. Science Practice 2.1 The student can justify the selection of a mathematical routine to solve problems. Learning Objective 1.6 The student is able to use data from mathematical models based on the Hardy Weinberg equilibrium to analyze genetic drift and the effects of selection in the evolution of specific populations. Essential Knowledge 1.A.3 Evolutionary change is also driven by random processes. Science Practice 2.1 The student can justify the selection of a mathematical routine to solve problems. Learning Objective 1.7 The student is able to justify data from mathematical models based on the Hardy Weinberg equilibrium to analyze genetic drift and the effects of selection in the evolution of specific populations. 

Another online example of genetic drift can be found at this website . Genetic Variance 

Natural selection and some of the other evolutionary forces can only act on heritable traits, namely an organism s genetic code. Because alleles are passed from parent to offspring, those that confer beneficial traits or behaviors may be selected for, while deleterious alleles may be selected against. Acquired traits, for the most part, are not heritable. For example, if an athlete works out in the gym every day, building up muscle strength, the athlete s offspring will not necessarily grow up to be a body builder. If there is a genetic basis for the ability to run fast, on the other hand, this may be passed to a child. 

Before Darwinian evolution became the prevailing theory of the field, French naturalist Jean-Baptiste Lamarck theorized that acquired traits could, in fact, be inherited; while this hypothesis has largely been unsupported, scientists have recently begun to realize that Lamarck was not completely wrong. Visit this site to learn more. 

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Heritability is the fraction of phenotype variation that can be attributed to genetic differences, or genetic variance, among individuals in a population. The greater the hereditability of a population s phenotypic variation, the more susceptible it is to the evolutionary forces that act on heritable variation. 

The diversity of alleles and genotypes within a population is called genetic variance . When scientists are involved in the breeding of a species, such as with animals in zoos and nature preserves, they try to increase a population s genetic variance to preserve as much of the phenotypic diversity as they can. This also helps reduce the risks associated with inbreeding , the mating of closely related individuals, which can have the undesirable effect of bringing together deleterious recessive mutations that can cause abnormalities and susceptibility to disease. For example, a disease that is caused by a rare, recessive allele might exist in a population, but it will only manifest itself when an individual carries two copies of the allele. Because the allele is rare in a normal, healthy population with unrestricted habitat, the chance that two carriers will mate is low, and even then, only 25 percent of their offspring will inherit the disease allele from both parents. While it is likely to happen at some point, it will not happen frequently enough for natural selection to be able to swiftly eliminate the allele from the population, and as a result, the allele will be maintained at low levels in the gene pool. However, if a family of carriers begins to interbreed with each other, this will dramatically increase the likelihood of two carriers mating and eventually producing diseased offspring, a phenomenon known as inbreeding depression . 

Changes in allele frequencies that are identified in a population can shed light on how it is evolving. In addition to natural selection, there are other evolutionary forces that could be in play: genetic drift, gene flow, mutation, nonrandom mating, and environmental variances. Genetic Drift 

The theory of natural selection stems from the observation that some individuals in a population are more likely to survive longer and have more offspring than others; thus, they will pass on more of their genes to the next generation. A big, powerful male gorilla, for example, is much more likely than a smaller, weaker one to become the population s silverback, the pack s leader who mates far more than the other males of the group. The pack leader will father more offspring, who share half of his genes, and are likely to also grow bigger and stronger like their father. Over time, the genes for bigger size will increase in frequency in the population, and the population will, as a result, grow larger on average. That is, this would occur if this particular selection pressure , or driving selective force, were the only one acting on the population. In other examples, better camouflage or a stronger resistance to drought might pose a selection pressure. 

Another way a population s allele and genotype frequencies can change is genetic drift ( [link] ), which is simply the effect of chance. By chance, some individuals will have more offspring than others not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the right time (when the receptive female walked by) or because the other one happened to be in the wrong place at the wrong time (when a fox was hunting). 

Genetic drift in a population can lead to the elimination of an allele from a population by chance. In this example, rabbits with the brown coat color allele ( B ) are dominant over rabbits with the white coat color allele ( b ). In the first generation, the two alleles occur with equal frequency in the population, resulting in p and q values of .5. Only half of the individuals reproduce, resulting in a second generation with p and q values of .7 and .3, respectively. Only two individuals in the second generation reproduce, and by chance these individuals are homozygous dominant for brown coat color. As a result, in the third generation the recessive b allele is lost. 

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Small populations are more susceptible to the forces of genetic drift. Large populations, on the other hand, are buffered against the effects of chance. If one individual of a population of 10 individuals happens to die at a young age before it leaves any offspring to the next generation, all of its genes 1/10 of the population s gene pool will be suddenly lost. In a population of 100, that s only 1 percent of the overall gene pool; therefore, it is much less impactful on the population s genetic structure. 

Go to this site to watch an animation of random sampling and genetic drift in action. 

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Genetic drift can also be magnified by natural events, such as a natural disaster that kills at random a large portion of the population. Known as the bottleneck effect, it results in a large portion of the genome suddenly being wiped out ( [link] ). In one fell swoop, the genetic structure of the survivors becomes the genetic structure of the entire population, which may be very different from the pre-disaster population. A chance event or catastrophe can reduce the genetic variability within a population. 

Another scenario in which populations might experience a strong influence of genetic drift is if some portion of the population leaves to start a new population in a new location or if a population gets divided by a physical barrier of some kind. In this situation, those individuals are unlikely to be representative of the entire population, which results in the founder effect. The founder effect occurs when the genetic structure changes to match that of the new population s founding fathers and mothers. The founder effect is believed to have been a key factor in the genetic history of the Afrikaner population of Dutch settlers in South Africa, as evidenced by mutations that are common in Afrikaners but rare in most other populations. This is likely due to the fact that a higher-than-normal proportion of the founding colonists carried these mutations. As a result, the population expresses unusually high incidences of Huntington s disease (HD) and Fanconi anemia (FA), a genetic disorder known to cause blood marrow and congenital abnormalities even cancer. 1 

Watch this short video to learn more about the founder and bottleneck effects. 

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Testing the Bottleneck Effect 

Question: How do natural disasters affect the genetic structure of a population? 

Background: When much of a population is suddenly wiped out by an earthquake or hurricane, the individuals that survive the event are usually a random sampling of the original group. As a result, the genetic makeup of the population can change dramatically. This phenomenon is known as the bottleneck effect. 

Hypothesis: Repeated natural disasters will yield different population genetic structures; therefore, each time this experiment is run, the results will vary. 

Test the hypothesis: Count out the original population using different colored beads. For example, red, blue, and yellow beads might represent red, blue, and yellow individuals. After recording the number of each individual in the original population, place them all in a bottle with a narrow neck that will only allow a few beads out at a time. Then, pour 1/3 of the bottle s contents into a bowl. This represents the surviving individuals after a natural disaster kills a majority of the population. Count the number of the different colored beads in the bowl, and record it. Then, place all of the beads back in the bottle and repeat the experiment four more times. 

Analyze the data: Compare the five populations that resulted from the experiment. Do the populations all contain the same number of different colored beads, or do they vary? Remember, these populations all came from the same exact parent population. 

Form a conclusion: Most likely, the five resulting populations will differ quite dramatically. This is because natural disasters are not selective they kill and spare individuals at random. Now think about how this might affect a real population. What happens when a hurricane hits the Mississippi Gulf Coast? How do the seabirds that live on the beach fare? Gene Flow 

Another important evolutionary force is gene flow : the flow of alleles in and out of a population due to the migration of individuals or gametes ( [link] ). While some populations are fairly stable, others experience more flux. Many plants, for example, send their pollen far and wide, by wind or by bird, to pollinate other populations of the same species some distance away. Even a population that may initially appear to be stable, such as a pride of lions, can experience its fair share of immigration and emigration as developing males leave their mothers to seek out a new pride with genetically unrelated females. This variable flow of individuals in and out of the group not only changes the gene structure of the population, but it can also introduce new genetic variation to populations in different geological locations and habitats. 

Gene flow can occur when an individual travels from one geographic location to another. Mutation 

Mutations are changes to an organism s DNA and are an important driver of diversity in populations. Species evolve because of the accumulation of mutations that occur over time. The appearance of new mutations is the most common way to introduce novel genotypic and phenotypic variance. Some mutations are unfavorable or harmful and are quickly eliminated from the population by natural selection. Others are beneficial and will spread through the population. Whether or not a mutation is beneficial or harmful is determined by whether it helps an organism survive to sexual maturity and reproduce. Some mutations do not do anything and can linger, unaffected by natural selection, in the genome. Some can have a dramatic effect on a gene and the resulting phenotype. Nonrandom Mating 

If individuals nonrandomly mate with their peers, the result can be a changing population. There are many reasons nonrandom mating occurs. One reason is simple mate choice; for example, female peahens may prefer peacocks with bigger, brighter tails. Traits that lead to more matings for an individual become selected for by natural selection. One common form of mate choice, called assortative mating , is an individual s preference to mate with partners who are phenotypically similar to themselves. 

Another cause of nonrandom mating is physical location. This is especially true in large populations spread over large geographic distances where not all individuals will have equal access to one another. Some might be miles apart through woods or over rough terrain, while others might live immediately nearby. Environmental Variance 

Genes are not the only players involved in determining population variation. Phenotypes are also influenced by other factors, such as the environment ( [link] ). For example, sun exposure is an environmental factor, as a person who spends more time in the sun will likely have darker skin than a person who spends most of their time indoors (assuming both people had similarly-colored skin to start with). Some major characteristics, such as gender, are determined by the environment for some species. For example, some turtles and other reptiles have temperature-dependent sex determination (TSD). TSD means that individuals develop into males if their eggs are incubated within a certain temperature range, or females at a different temperature range. The sex of the American alligator ( Alligator mississippiensis ) is determined by the temperature at which the eggs are incubated. Eggs incubated at 30 C produce females, and eggs incubated at 33 C produce males. (credit: Steve Hillebrand, USFWS) 

Geographic separation between populations can lead to differences in the phenotypic variation between those populations. Such geographical variation is seen between most populations and can be significant. One type of geographic variation, called a cline , can be seen as populations of a given species vary gradually across an ecological gradient. Species of warm-blooded animals, for example, tend to have larger bodies in the cooler climates closer to the earth s poles, allowing them to better conserve heat. This is considered a latitudinal cline. Alternatively, flowering plants tend to bloom at different times depending on where they are along the slope of a mountain, known as an altitudinal cline. 

If there is gene flow between the populations, the individuals will likely show gradual differences in phenotype along the cline. Restricted gene flow, on the other hand, can lead to abrupt differences, even speciation. Lab Investigation 

AP Biology Investigative Labs: Inquiry-Based Approach, Investigation 1: Artificial Selection . Using Wisconsin Fast Plants, you explore evolution by conducting an artificial selection investigation to increase or decrease genetic variation in a population and then determine if extreme selection can change the expression of a quantitative trait. Think About It Do you think genetic drift would happen more quickly on an island or on the mainland? Provide reasoning for your answer. Consider the population of red and blue flowers you analyzed in Section 1 to determine if they were undergoing microevolution. Recall that you counted 600 blue flowers and 200 red flowers. Imagine that you return four years after your initial visit, and the flowers at the site have been split into two different populations by a newly formed river, which isolates the two populations. In the population 1, you counted 125 blue flowers and 10 red flowers. In the population 2, you counted 450 blue flowers and 300 red flowers. Did genetic drift or natural selection likely cause these change in allele frequencies in population 1? What about population 2? Explain how you know for each population. The lab investigation is an application of AP Learning Objective 1.8 and Science Practice 6.4 because students are investigating the effect(s) of artificial selection on the genetic makeup of a population. The first Think About It question is an application AP Learning Objective 1.8 and Science Practice 6.4 because students are making a prediction about the effect of genetic drift on the genetic makeup of a population, and the factors that influence the effects of genetic drift. First think about it question answer: Genetic drift is more likely on an island because of the founder effect. New island populations are often started by specific individuals of an original population, carrying gene frequencies different from those of the parent population. This causes genetic drift. Second Think About It Answers: In the first visit, it was determined that 200 out of 800 flowers had the recessive homozygous phenotype. Therefore, q 2 =0.25 and q = 0.5. For the first population, 10 out of 135 flowers were red. Therefore, q = 0.27. If bees were selecting for red flowers, the frequency of red flowers should increase, not decrease. Therefore, this evolutionary change in population 1 was likely caused by genetic drift. In the second population, 300 out of 750 flowers were red. Therefore, q=0.63 and p=0.37. This indicates that the frequency of the recessive allele q, which causes red coloration, is increasing, and is consistent with the hypothesis that red flowers are being selected for by bees. The second Think About It questions are applications AP Learning Objective 1.6 and Science Practices 1.4 and 2.1, and Learning Objective 1.7 and Science Practice 2.1, because students are using data sets that require the use of the Hardy Weinberg equation to justify if genetic drift or selection is involved in the evolution of specific populations. Section Summary 

Both genetic and environmental factors can cause phenotypic variation in a population. Different alleles can confer different phenotypes, and different environments can also cause individuals to look or act differently. Only those differences encoded in an individual s genes, however, can be passed to its offspring and, thus, be a target of natural selection. Natural selection works by selecting for alleles that confer beneficial traits or behaviors, while selecting against those for deleterious qualities. Genetic drift stems from the chance occurrence that some individuals in the germ line have more offspring than others. When individuals leave or join the population, allele frequencies can change as a result of gene flow. Mutations to an individual s DNA may introduce new variation into a population. Allele frequencies can also be altered when individuals do not randomly mate with others in the group. Review Questions 

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[link] Footnotes 1 A. J. Tipping et al., Molecular and Genealogical Evidence for a Founder Effect in Fanconi Anemia Families of the Afrikaner Population of South Africa, PNAS 98, no. 10 (2001): 5734-5739, doi: 10.1073/pnas.091402398. Glossary assortative mating when individuals tend to mate with those who are phenotypically similar to themselves bottleneck effect magnification of genetic drift as a result of natural events or catastrophes cline gradual geographic variation across an ecological gradient gene flow flow of alleles in and out of a population due to the migration of individuals or gametes genetic drift effect of chance on a population s gene pool genetic variance diversity of alleles and genotypes in a population geographical variation differences in the phenotypic variation between populations that are separated geographically heritability fraction of population variation that can be attributed to its genetic variance inbreeding mating of closely related individuals inbreeding depression increase in abnormalities and disease in inbreeding populations nonrandom mating changes in a population s gene pool due to mate choice or other forces that cause individuals to mate with certain phenotypes more than others polymorphisms variations in phenotype within individuals of a population population variation distribution of phenotypes in a population selective pressure environmental factor that causes one phenotype to be better than anotherAdaptive Evolution Adaptive Evolution 

In this section, you will explore the following questions: What are different ways in which natural selection can shape populations? How can these different forces lead to different outcomes in terms of population variation? Connections for AP Courses 

As we have learned, natural selection acts on the level of the individual, selecting those with a higher overall fitness (reproductive success) compared to the rest of the population. In other words, natural selection favors the most adaptive variation for a given environment. If the fit phenotypes are evolving in a stable environment, natural selection results in stabilizing selection , resulting in an overall decrease in the population s variation. However, if environmental conditions change, directional selection shifts a population s variance toward a new and more favorable phenotype. Diversifying selection results in increased variance by selecting for two or more distinct phenotypes. 

Sexual selection results when one sex has more reproductive success than the other; as a result, males and females experience different selective pressures, which often lead to distinct phenotypic differences, or sexual dimorphisms , between the two. For example, male birds often exhibit more colorful plumage than female birds of the same species. 

What is most important to recognize is that there is no perfect organism. Natural selection acts on existing variations in the population; it does not create anything from scratch. Although natural selection selects the fittest individuals, other forces of evolution, including genetic drift and gene flow, often introduce deleterious alleles to the population s gene pool. Evolution has no purpose; it is simply the sum of various forces that influence the genetic and phenotypic variation of a population. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.A. Natural selection is a major mechanism of evolution Essential Knowledge 1.A.1 Natural selection is a major mechanism of evolution. Science Practice 2.2 The student can apply mathematical routines to quantities that describe natural phenomena. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.2 The student is able to evaluate evidence provided by data to qualitatively and quantitatively investigate the role of natural selection in evolution. Essential Knowledge 1.A.2 Natural selection acts on phenotypic variations in populations. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 1.5 The student is able to connect evolutionary changes in a population over time to a change in the environment. 

Natural selection only acts on the population s heritable traits: selecting for beneficial alleles and thus increasing their frequency in the population, while selecting against deleterious alleles and thereby decreasing their frequency a process known as adaptive evolution . Natural selection does not act on individual alleles, however, but on entire organisms. An individual may carry a very beneficial genotype with a resulting phenotype that, for example, increases the ability to reproduce (fecundity), but if that same individual also carries an allele that results in a fatal childhood disease, that fecundity phenotype will not be passed on to the next generation because the individual will not live to reach reproductive age. Natural selection acts at the level of the individual; it selects for individuals with greater contributions to the gene pool of the next generation, known as an organism s evolutionary (Darwinian) fitness . 

Fitness is often quantifiable and is measured by scientists in the field. However, it is not the absolute fitness of an individual that counts, but rather how it compares to the other organisms in the population. This concept, called relative fitness , allows researchers to determine which individuals are contributing additional offspring to the next generation, and thus, how the population might evolve. 

There are several ways selection can affect population variation: stabilizing selection, directional selection, diversifying selection, frequency-dependent selection, and sexual selection. As natural selection influences the allele frequencies in a population, individuals can either become more or less genetically similar and the phenotypes displayed can become more similar or more disparate. Stabilizing Selection 

If natural selection favors an average phenotype, selecting against extreme variation, the population will undergo stabilizing selection ( [link] ). In a population of mice that live in the woods, for example, natural selection is likely to favor individuals that best blend in with the forest floor and are less likely to be spotted by predators. Assuming the ground is a fairly consistent shade of brown, those mice whose fur is most closely matched to that color will be most likely to survive and reproduce, passing on their genes for their brown coat. Mice that carry alleles that make them a bit lighter or a bit darker will stand out against the ground and be more likely to fall victim to predation. As a result of this selection, the population s genetic variance will decrease. Directional Selection 

When the environment changes, populations will often undergo directional selection ( [link] ), which selects for phenotypes at one end of the spectrum of existing variation. A classic example of this type of selection is the evolution of the peppered moth in eighteenth- and nineteenth-century England. Prior to the Industrial Revolution, the moths were predominately light in color, which allowed them to blend in with the light-colored trees and lichens in their environment. But as soot began spewing from factories, the trees became darkened, and the light-colored moths became easier for predatory birds to spot. Over time, the frequency of the melanic form of the moth increased because they had a higher survival rate in habitats affected by air pollution because their darker coloration blended with the sooty trees. Similarly, the hypothetical mouse population may evolve to take on a different coloration if something were to cause the forest floor where they live to change color. The result of this type of selection is a shift in the population s genetic variance toward the new, fit phenotype. 

In science, sometimes things are believed to be true, and then new information comes to light that changes our understanding. The story of the peppered moth is an example: the facts behind the selection toward darker moths have recently been called into question. Read this article to learn more. 

[link] Diversifying Selection 

Sometimes two or more distinct phenotypes can each have their advantages and be selected for by natural selection, while the intermediate phenotypes are, on average, less fit. Known as diversifying selection ( [link] ), this is seen in many populations of animals that have multiple male forms. Large, dominant alpha males obtain mates by brute force, while small males can sneak in for furtive copulations with the females in an alpha male s territory. In this case, both the alpha males and the sneaking males will be selected for, but medium-sized males, which can t overtake the alpha males and are too big to sneak copulations, are selected against. Diversifying selection can also occur when environmental changes favor individuals on either end of the phenotypic spectrum. Imagine a population of mice living at the beach where there is light-colored sand interspersed with patches of tall grass. In this scenario, light-colored mice that blend in with the sand would be favored, as well as dark-colored mice that can hide in the grass. Medium-colored mice, on the other hand, would not blend in with either the grass or the sand, and would thus be more likely to be eaten by predators. The result of this type of selection is increased genetic variance as the population becomes more diverse. Different types of natural selection can impact the distribution of phenotypes within a population. In (a) stabilizing selection, an average phenotype is favored. In (b) directional selection, a change in the environment shifts the spectrum of phenotypes observed. In (c) diversifying selection, two or more extreme phenotypes are selected for, while the average phenotype is selected against. 

[link] Frequency-dependent Selection 

Another type of selection, called frequency-dependent selection , favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection). An interesting example of this type of selection is seen in a unique group of lizards of the Pacific Northwest. Male common side-blotched lizards come in three throat-color patterns: orange, blue, and yellow. Each of these forms has a different reproductive strategy: orange males are the strongest and can fight other males for access to their females; blue males are medium-sized and form strong pair bonds with their mates; and yellow males ( [link] ) are the smallest, and look a bit like females, which allows them to sneak copulations. Like a game of rock-paper-scissors, orange beats blue, blue beats yellow, and yellow beats orange in the competition for females. That is, the big, strong orange males can fight off the blue males to mate with the blue s pair-bonded females, the blue males are successful at guarding their mates against yellow sneaker males, and the yellow males can sneak copulations from the potential mates of the large, polygynous orange males. A yellow-throated side-blotched lizard is smaller than either the blue-throated or orange-throated males and appears a bit like the females of the species, allowing it to sneak copulations. (credit: tinyfroglet /Flickr) 

In this scenario, orange males will be favored by natural selection when the population is dominated by blue males, blue males will thrive when the population is mostly yellow males, and yellow males will be selected for when orange males are the most populous. As a result, populations of side-blotched lizards cycle in the distribution of these phenotypes in one generation, orange might be predominant, and then yellow males will begin to rise in frequency. Once yellow males make up a majority of the population, blue males will be selected for. Finally, when blue males become common, orange males will once again be favored. 

Negative frequency-dependent selection serves to increase the population s genetic variance by selecting for rare phenotypes, whereas positive frequency-dependent selection usually decreases genetic variance by selecting for common phenotypes. Sexual Selection 

Males and females of certain species are often quite different from one another in ways beyond the reproductive organs. Males are often larger, for example, and display many elaborate colors and adornments, like the peacock s tail, while females tend to be smaller and duller in decoration. Such differences are known as sexual dimorphisms ( [link] ), which arise from the fact that in many populations, particularly animal populations, there is more variance in the reproductive success of the males than there is of the females. That is, some males often the bigger, stronger, or more decorated males get the vast majority of the total matings, while others receive none. This can occur because the males are better at fighting off other males, or because females will choose to mate with the bigger or more decorated males. In either case, this variation in reproductive success generates a strong selection pressure among males to get those matings, resulting in the evolution of bigger body size and elaborate ornaments to get the females attention. Females, on the other hand, tend to get a handful of selected matings; therefore, they are more likely to select more desirable males. 

Sexual dimorphism varies widely among species, of course, and some species are even sex-role reversed. In such cases, females tend to have a greater variance in their reproductive success than males and are correspondingly selected for the bigger body size and elaborate traits usually characteristic of males. Sexual dimorphism is observed in (a) peacocks and peahens, (b) Argiope appensa spiders (the female spider is the large one), and in (c) wood ducks. (credit spiders : modification of work by Sanba38 /Wikimedia Commons; credit duck : modification of work by Kevin Cole) 

The selection pressures on males and females to obtain matings is known as sexual selection; it can result in the development of secondary sexual characteristics that do not benefit the individual s likelihood of survival but help to maximize its reproductive success. Sexual selection can be so strong that it selects for traits that are actually detrimental to the individual s survival. Think, once again, about the peacock s tail. While it is beautiful and the male with the largest, most colorful tail is more likely to win the female, it is not the most practical appendage. In addition to being more visible to predators, it makes the males slower in their attempted escapes. There is some evidence that this risk, in fact, is why females like the big tails in the first place. The speculation is that large tails carry risk, and only the best males survive that risk: the bigger the tail, the more fit the male. This idea is known as the handicap principle . 

The good genes hypothesis states that males develop these impressive ornaments to show off their efficient metabolism or their ability to fight disease. Females then choose males with the most impressive traits because it signals their genetic superiority, which they will then pass on to their offspring. Though it might be argued that females should not be picky because it will likely reduce their number of offspring, if better males father more fit offspring, it may be beneficial. Fewer, healthier offspring may increase the chances of survival more than many, weaker offspring. Link to Learning 

In 1915, biologist Ronald Fisher proposed another model of sexual selection: the Fisherian runaway model , which suggests that selection of certain traits is a result of sexual preference. 

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In both the handicap principle and the good genes hypothesis, the trait is said to be an honest signal of the males quality, thus giving females a way to find the fittest mates males that will pass the best genes to their offspring. No Perfect Organism 

Natural selection is a driving force in evolution and can generate populations that are better adapted to survive and successfully reproduce in their environments. But natural selection cannot produce the perfect organism. Natural selection can only select on existing variation in the population; it does not create anything from scratch. Thus, it is limited by a population s existing genetic variance and whatever new alleles arise through mutation and gene flow. 

Natural selection is also limited because it works at the level of individuals, not alleles, and some alleles are linked due to their physical proximity in the genome, making them more likely to be passed on together (linkage disequilibrium). Any given individual may carry some beneficial alleles and some unfavorable alleles. It is the net effect of these alleles, or the organism s fitness, upon which natural selection can act. As a result, good alleles can be lost if they are carried by individuals that also have several overwhelmingly bad alleles; likewise, bad alleles can be kept if they are carried by individuals that have enough good alleles to result in an overall fitness benefit. 

Furthermore, natural selection can be constrained by the relationships between different polymorphisms. One morph may confer a higher fitness than another, but may not increase in frequency due to the fact that going from the less beneficial to the more beneficial trait would require going through a less beneficial phenotype. Think back to the mice that live at the beach. Some are light-colored and blend in with the sand, while others are dark and blend in with the patches of grass. The dark-colored mice may be, overall, more fit than the light-colored mice, and at first glance, one might expect the light-colored mice be selected for a darker coloration. But remember that the intermediate phenotype, a medium-colored coat, is very bad for the mice they cannot blend in with either the sand or the grass and are more likely to be eaten by predators. As a result, the light-colored mice would not be selected for a dark coloration because those individuals that began moving in that direction (began being selected for a darker coat) would be less fit than those that stayed light. 

Finally, it is important to understand that not all evolution is adaptive. While natural selection selects the fittest individuals and often results in a more fit population overall, other forces of evolution, including genetic drift and gene flow, often do the opposite: introducing deleterious alleles to the population s gene pool. Evolution has no purpose it is not changing a population into a preconceived ideal. It is simply the sum of the various forces described in this chapter and how they influence the genetic and phenotypic variance of a population. Think About It 

In recent years, factories have been cleaner, and less soot is released into the environment. What impact do you think this has had on the distribution of moth color in the population? This question is an application of AP Learning Objective 1.2 and Science Practices 2.2 and 5.3 and Learning Objective 1.5 and Science Practice 7.1 because, based on evidence, students are connecting evolutionary changes in a population by natural selection to environmental change. To further enrich this activity, use the peppered moth simulator located here . Additional information on the controversial nature of Kettlewell s findings can be found at the following sites: The Panda s Thumb The Peppered Moth An Update Fine Tuning The Peppered Moth Paradigm With less soot in the environment, tree bark tends to be lighter in color. This change is a selective advantage for light-colored moths, which will be camouflaged from predators. Darker moths, on the other hand, will have a selective disadvantage based on their color contrast with the lighter bark, making them stand out visually to predators. Thus, the percentage of light-colored moths will increase while the percentage of dark-colored moths will decrease. Section Summary 

Because natural selection acts to increase the frequency of beneficial alleles and traits while decreasing the frequency of deleterious qualities, it is adaptive evolution. Natural selection acts at the level of the individual, selecting for those that have a higher overall fitness compared to the rest of the population. If the fit phenotypes are those that are similar, natural selection will result in stabilizing selection, and an overall decrease in the population s variation. Directional selection works to shift a population s variance toward a new, fit phenotype, as environmental conditions change. In contrast, diversifying selection results in increased genetic variance by selecting for two or more distinct phenotypes. 

Other types of selection include frequency-dependent selection, in which individuals with either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection) are selected for. Finally, sexual selection results from the fact that one sex has more variance in the reproductive success than the other. As a result, males and females experience different selective pressures, which can often lead to the evolution of phenotypic differences, or sexual dimorphisms, between the two. Review Questions 

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[link] Glossary adaptive evolution increase in frequency of beneficial alleles and decrease in deleterious alleles due to selection directional selection selection that favors phenotypes at one end of the spectrum of existing variation diversifying selection selection that favors two or more distinct phenotypes evolutionary fitness (also, Darwinian fitness) individual s ability to survive and reproduce fitness measure of successful reproduction, the passing on alleles to the next generation frequency-dependent selection selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection) good genes hypothesis theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease handicap principle theory of sexual selection that argues only the fittest individuals can afford costly traits honest signal trait that gives a truthful impression of an individual s fitness relative fitness individual s ability to survive and reproduce relative to the rest of the population sexual dimorphism phenotypic difference between the males and females of a population stabilizing selection selection that favors average phenotypesIntroduction Introduction class="introduction" class="summary" title="Chapter Summary" class="ost-reading-discard ost-chapter-review review" title="Review Questions" class="ost-reading-discard ost-chapter-review critical-thinking" title="Critical Thinking Questions" class="ost-chapter-review ost-reading-discard ap-test-prep" title="Test Prep for AP sup #174; /sup Courses" The life of a bee is very different from the life of a flower, but the two organisms are related. Both are members of the domain Eukarya and have cells containing many similar organelles, genes, and proteins. (credit: modification of work by John Beetham) 

This bee and Echinacea flower ( [link] ) could not look more different, yet they are related, as are all living organisms on Earth. By following pathways of similarities and changes both visible and genetic scientists seek to map the evolutionary past of how life developed from single-celled organisms to the tremendous variety of creatures that have germinated, crawled, floated, swam, flown, and walked on this planet. 

New species are discovered with frequent regularity, but it s not too common to discover a new large mammal. However, that s what scientists did in Australia when they named a new species of cetacean the Australian humpback dolphin, Souse sahulensis . The dolphin had originally been classified as another closely related species, but a closer look at its coloration, skeletal structure, habitat, and DNA determined that it was in fact a separate species. 

For more information, read the research article yourself.Organizing Life on Earth Organizing Life on Earth 

In this section, you will explore the following questions: Why do scientists need a comprehensive classification system to study living organisms? What are the different levels of the taxonomic classification system? How are systematics and taxonomy related to phylogeny? What are the components and purpose of a phylogenetic tree? Connection for AP Courses 

In prior chapters we explored how all organisms on Earth, extant and extinct, evolved from common ancestry. Supporting this claim are core features and processes, such as a common genetic code and metabolic pathways, which evolved billions of years ago and are widely distributed among organisms living today. The evolutionary history and relationship of an organism or a group of organisms is called phylogeny . Scientists often construct phylogenetic trees based on evidence drawn from multiple disciplines to illustrate evolutionary pathways and connections among organisms. 

Scientists historically organized Earth s millions of species into a hierarchical taxonomic classification system from the most inclusive category to the most specific: domain, kingdom, phylum, class, order, family, genus, and species. The traditional five-kingdom system that you might have studied in middle school was expanded (and reorganized) to include three domains: Bacteria, Archaea, and Eukarya, with prokaryotes divided between Bacteria or Archaea depending on their molecular genetic machinery, and protists, fungi, plants, and animals grouped in Eukarya. Today, however, phylogenetic trees provide more specific information about evolutionary history and relationships among organisms. (For the purpose of AP , you do not have to memorize the taxonomic levels. However, it is important to reiterate that taxonomy is a tool to organize the millions of organisms on Earth, similar to how items in a grocery store or mall shop are organized into different departments. Like new products, organisms are often shifted among their taxonomic groups!) 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives and diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.14 The student is able to pose scientific questions that correctly identify essential properties of shared, core life processes that provide insight into the history of life on Earth. Essential Knowledge 1.B.1 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 1.16 The student is able to justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Essential Knowledge 1.B.2 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.17 The student is able to pose scientific questions about a group of organisms whose relatedness is described by a phylogenetic tree or cladogram. Phylogenetic Trees 

Scientists use a tool called a phylogenetic tree to show the evolutionary pathways and connections among organisms. A phylogenetic tree is a diagram used to reflect evolutionary relationships among organisms or groups of organisms. Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships. In other words, a tree of life can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms ( [link] ). 

Unlike a taxonomic classification diagram, a phylogenetic tree can be read like a map of evolutionary history. Many phylogenetic trees have a single lineage at the base representing a common ancestor. Scientists call such trees rooted , which means there is a single ancestral lineage (typically drawn from the bottom or left) to which all organisms represented in the diagram relate. Notice in the rooted phylogenetic tree that the three domains Bacteria, Archaea, and Eukarya diverge from a single point and branch off. The small branch that plants and animals (including humans) occupy in this diagram shows how recent and miniscule these groups are compared with other organisms. Unrooted trees don t show a common ancestor but do show relationships among species. Both of these phylogenetic trees shows the relationship of the three domains of life Bacteria, Archaea, and Eukarya but the (a) rooted tree attempts to identify when various species diverged from a common ancestor while the (b) unrooted tree does not. (credit a: modification of work by Eric Gaba) 

In a rooted tree, the branching indicates evolutionary relationships ( [link] ). The point where a split occurs, called a branch point , represents where a single lineage evolved into a distinct new one. A lineage that evolved early from the root and remains unbranched is called basal taxon . When two lineages stem from the same branch point, they are called sister taxa . A branch with more than two lineages is called a polytomy and serves to illustrate where scientists have not definitively determined all of the relationships. It is important to note that although sister taxa and polytomy do share an ancestor, it does not mean that the groups of organisms split or evolved from each other. Organisms in two taxa may have split apart at a specific branch point, but neither taxa gave rise to the other. The root of a phylogenetic tree indicates that an ancestral lineage gave rise to all organisms on the tree. A branch point indicates where two lineages diverged. A lineage that evolved early and remains unbranched is a basal taxon. When two lineages stem from the same branch point, they are sister taxa. A branch with more than two lineages is a polytomy. 

The diagrams above can serve as a pathway to understanding evolutionary history. The pathway can be traced from the origin of life to any individual species by navigating through the evolutionary branches between the two points. Also, by starting with a single species and tracing back towards the "trunk" of the tree, one can discover that species' ancestors, as well as where lineages share a common ancestry. In addition, the tree can be used to study entire groups of organisms. 

Another point to mention on phylogenetic tree structure is that rotation at branch points does not change the information. For example, if a branch point was rotated and the taxon order changed, this would not alter the information because the evolution of each taxon from the branch point was independent of the other. 

Many disciplines within the study of biology contribute to understanding how past and present life evolved over time; these disciplines together contribute to building, updating, and maintaining the tree of life. Information is used to organize and classify organisms based on evolutionary relationships in a scientific field called systematics . Data may be collected from fossils, from studying the structure of body parts or molecules used by an organism, and by DNA analysis. By combining data from many sources, scientists can put together the phylogeny of an organism; since phylogenetic trees are hypotheses, they will continue to change as new types of life are discovered and new information is learned. Limitations of Phylogenetic Trees 

It may be easy to assume that more closely related organisms look more alike, and while this is often the case, it is not always true. If two closely related lineages evolved under significantly varied surroundings or after the evolution of a major new adaptation, it is possible for the two groups to appear more different than other groups that are not as closely related. For example, the phylogenetic tree in [link] shows that lizards and rabbits both have amniotic eggs, whereas frogs do not; yet lizards and frogs appear more similar than lizards and rabbits. This ladder-like phylogenetic tree of vertebrates is rooted by an organism that lacked a vertebral column. At each branch point, organisms with different characters are placed in different groups based on the characteristics they share. 

Another aspect of phylogenetic trees is that, unless otherwise indicated, the branches do not account for length of time, only the evolutionary order. In other words, the length of a branch does not typically mean more time passed, nor does a short branch mean less time passed unless specified on the diagram. For example, in [link] , the tree does not indicate how much time passed between the evolution of amniotic eggs and hair. What the tree does show is the order in which things took place. Again using [link] , the tree shows that the oldest trait is the vertebral column, followed by hinged jaws, and so forth. Remember that any phylogenetic tree is a part of the greater whole, and like a real tree, it does not grow in only one direction after a new branch develops. So, for the organisms in [link] , just because a vertebral column evolved does not mean that invertebrate evolution ceased, it only means that a new branch formed. Also, groups that are not closely related, but evolve under similar conditions, may appear more phenotypically similar to each other than to a close relative. Link to Learning 

Head to this website to see interactive exercises that allow you to explore the evolutionary relationships among species. 

[link] Think About It 

How does a phylogenetic tree relate to the passing of time? What other questions about the evolutionary history of an organism and its relatedness to other organisms can a phylogenetic tree answer? This question is an application of AP Learning Objective 1.14 and Science Practice 3.1 and Learning Objective 1.17 and Science Practice 3.1 because students must pose questions about evolutionary history before they can answer them. Phylogenetic trees approximate the passing of time by the lengths of their branches. Longer branches mean that more time has passed since the organisms shared a common ancestor. Thus, a phylogenetic tree not only shows evolutionary relationships among organisms, but also how long ago the divergence from the common ancestor occurred. The Levels of Classification 

Taxonomy (which literally means arrangement law ) is the science of classifying organisms to construct internationally shared classification systems with each organism placed into more and more inclusive groupings. Think about how a grocery store is organized. One large space is divided into departments, such as produce, dairy, and meats. Then each department further divides into aisles, then each aisle into categories and brands, and then finally a single product. This organization from larger to smaller, more specific categories is called a hierarchical system. 

The taxonomic classification system (also called the Linnaean system after its inventor, Carl Linnaeus, a Swedish botanist, zoologist, and physician) uses a hierarchical model. Moving from the point of origin, the groups become more specific, until one branch ends as a single species. For example, after the common beginning of all life, scientists divide organisms into three large categories called a domain: Bacteria, Archaea, and Eukarya. Within each domain is a second category called a kingdom . After kingdoms, the subsequent categories of increasing specificity are: phylum , class , order , family , genus , and species ( [link] ). The taxonomic classification system uses a hierarchical model to organize living organisms into increasingly specific categories. The common dog, Canis lupus familiaris , is a subspecies of Canis lupus , which also includes the wolf and dingo. (credit dog : modification of work by Janneke Vreugdenhil) 

The kingdom Animalia stems from the Eukarya domain. For the common dog, the classification levels would be as shown in [link] . Therefore, the full name of an organism technically has eight terms. For the dog, it is: Eukarya, Animalia, Chordata, Mammalia, Carnivora, Canidae, Canis, and lupus . Notice that each name is capitalized except for species, and the genus and species names are italicized. Scientists generally refer to an organism only by its genus and species, which is its two-word scientific name, in what is called binomial nomenclature . Therefore, the scientific name of the dog is Canis lupus . The name at each level is also called a taxon . In other words, dogs are in order Carnivora. Carnivora is the name of the taxon at the order level; Canidae is the taxon at the family level, and so forth. Organisms also have a common name that people typically use, in this case, dog. Note that the dog is additionally a subspecies: the familiaris in Canis lupus familiaris. Subspecies are members of the same species that are capable of mating and reproducing viable offspring, but they are considered separate subspecies due to geographic or behavioral isolation or other factors. 

[link] shows how the levels move toward specificity with other organisms. Notice how the dog shares a domain with the widest diversity of organisms, including plants and butterflies. At each sublevel, the organisms become more similar because they are more closely related. Historically, scientists classified organisms using characteristics, but as DNA technology developed, more precise phylogenies have been determined. Visual Connection At each sublevel in the taxonomic classification system, organisms become more similar. Dogs and wolves are the same species because they can breed and produce viable offspring, but they are different enough to be classified as different subspecies. (credit plant : modification of work by "berduchwal"/Flickr; credit insect : modification of work by Jon Sullivan; credit fish : modification of work by Christian Mehlf hrer; credit rabbit : modification of work by Aidan Wojtas; credit cat : modification of work by Jonathan Lidbeck; credit fox : modification of work by Kevin Bacher, NPS; credit jackal : modification of work by Thomas A. Hermann, NBII, USGS; credit wolf : modification of work by Robert Dewar; credit dog : modification of work by "digital_image_fan"/Flickr) 

[link] Link to Learning 

Visit this website to classify three organisms bear, orchid, and sea cucumber from kingdom to species. To launch the game, under Classifying Life, click the picture of the bear or the Launch Interactive button. 

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Recent genetic analysis and other advancements have found that some earlier phylogenetic classifications do not align with the evolutionary past; therefore, changes and updates must be made as new discoveries occur. Recall that phylogenetic trees are hypotheses and are modified as data becomes available. In addition, classification historically has focused on grouping organisms mainly by shared characteristics and does not necessarily illustrate how the various groups relate to each other from an evolutionary perspective. For example, despite the fact that a hippopotamus resembles a pig more than a whale, the hippopotamus may be the closest living relative of the whale. Section Summary 

Scientists continually gain new information that helps understand the evolutionary history of life on Earth. Each group of organisms went through its own evolutionary journey, called its phylogeny. Each organism shares relatedness with others, and based on morphologic and genetic evidence, scientists attempt to map the evolutionary pathways of all life on Earth. Historically, organisms were organized into a taxonomic classification system. However, today many scientists build phylogenetic trees to illustrate evolutionary relationships. Review Questions 

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[link] Glossary basal taxon branch on a phylogenetic tree that has not diverged significantly from the root ancestor binomial nomenclature system of two-part scientific names for an organism, which includes genus and species names branch point node on a phylogenetic tree where a single lineage splits into distinct new ones class division of phylum in the taxonomic classification system family division of order in the taxonomic classification system genus division of family in the taxonomic classification system; the first part of the binomial scientific name kingdom division of domain in the taxonomic classification system order division of class in the taxonomic classification system phylogenetic tree diagram used to reflect the evolutionary relationships among organisms or groups of organisms phylogeny evolutionary history and relationship of an organism or group of organisms phylum (plural: phyla) division of kingdom in the taxonomic classification system polytomy branch on a phylogenetic tree with more than two groups or taxa rooted single ancestral lineage on a phylogenetic tree to which all organisms represented in the diagram relate sister taxa two lineages that diverged from the same branch point systematics field of organizing and classifying organisms based on evolutionary relationships taxon (plural: taxa) single level in the taxonomic classification system taxonomy science of classifying organisms taxonomic classification system hierarchical system of classifying organisms, including the classification of domain, kingdom, phylum, class, order, family, genus, and speciesDetermining Evolutionary Relationships Determining Evolutionary Relationships What is the difference between homologous and analogous traits? How are these traits used when determining evolutionary relatedness? What is cladistics? How does a cladogram differ from a phylogenetic tree? What is parsimony? Connection for AP Courses 

To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony ) and the fewest number of evolutionary steps. 

Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 1 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives the diversity and unity of life. 

Enduring Understanding 1.A Change in the genetic makeup of a population over time is evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.9 The student is able to evaluate evidence provided by data from many scientific disciplines that support biological evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 5.2 The student can refine observations and measurements based on data analysis. Learning Objective 1.10 The student is able to refine evidence based on data from many scientific disciplines that support biological evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 4.2 The student can design a plan for collecting data to answer a particular scientific question. Learning Objective 1.11 The student is able to design a plan to answer scientific questions regarding how organisms have changed over time using information from morphology, biochemistry, and geology. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 7.1 The student can connect phenomena and models across spatial and temporal scales. Learning Objective 1.12 The student is able to connect scientific evidence from many scientific disciplines to support the modern concept of evolution. Essential Knowledge 1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 2.1 The student can justify the selection of a mathematical routine to solve problems. Learning Objective 1.13 The student is able to construct and/or justify mathematical models, diagrams or simulations that represent processes of biological evolution. 

Big Idea 1 The process of evolution drives and diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.14 The student is able to pose scientific questions that correctly identify essential properties of shared, core life processes that provide insight into the history of life on Earth. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 6.1 The student can justify claims with evidence. Learning Objective 1.16 The student is able to justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Essential Knowledge 1.B.2 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.17 The student is able to pose scientific questions about a group of organisms whose relatedness is described by a phylogenetic tree or cladogram. Essential Knowledge 1.B.2 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. Science Practice 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. Learning Objective 1.18 The student is able to evaluate evidence provided by a data set in conjunction with a phylogenetic tree or simple cladogram to determine evolutionary history and speciation. Essential Knowledge 1.B.2 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. Science Practice 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain. Science Practice 2.1 The student can justify the selection of a mathematical routine to solve problems. Learning Objective 1.19 The student is able to create a phylogenetic tree or simple cladogram that correctly represents evolutionary history and speciation from a provided data set. Two Options for Similarities 

In general, organisms that share similar physical features and genomes tend to be more closely related than those that do not. Such features that overlap both morphologically (in form) and genetically are referred to as homologous structures; they stem from developmental similarities that are based on evolution. For example, the bones in the wings of bats and birds have homologous structures ( [link] ). Bat and bird wings are homologous structures, indicating that bats and birds share a common evolutionary past. (credit a: modification of work by Steve Hillebrand, USFWS; credit b: modification of work by U.S. DOI BLM) 

Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances 

Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures ( [link] ). 

Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied. The (c) wing of a honeybee is similar in shape to a (b) bird wing and (a) bat wing, and it serves the same function. However, the honeybee wing is not composed of bones and has a distinctly different structure and embryonic origin. These wing types (insect versus bat and bird) illustrate an analogy similar structures that do not share an evolutionary history. (credit a: modification of work by Steve Hillebrand, USFWS; credit b: modification of work by U.S. DOI BLM; credit c: modification of work by Jon Sullivan) Link to Learning 

This website has several examples to show how appearances can be misleading in understanding the phylogenetic relationships of organisms. 

[link] Molecular Comparisons 

With the advancement of DNA technology, the area of molecular systematics , which describes the use of information on the molecular level including DNA analysis, has blossomed. New computer programs not only confirm many earlier classified organisms, but also uncover previously made errors. As with physical characteristics, even the DNA sequence can be tricky to read in some cases. For some situations, two very closely related organisms can appear unrelated if a mutation occurred that caused a shift in the genetic code. An insertion or deletion mutation would move each nucleotide base over one place, causing two similar codes to appear unrelated. 

Sometimes two segments of DNA code in distantly related organisms randomly share a high percentage of bases in the same locations, causing these organisms to appear closely related when they are not. For both of these situations, computer technologies have been developed to help identify the actual relationships, and, ultimately, the coupled use of both morphologic and molecular information is more effective in determining phylogeny. Evolution Connection 

Why Does Phylogeny Matter? Evolutionary biologists could list many reasons why understanding phylogeny is important to everyday life in human society. For botanists, phylogeny acts as a guide to discovering new plants that can be used to benefit people. Think of all the ways humans use plants food, medicine, and clothing are a few examples. If a plant contains a compound that is effective in treating cancer, scientists might want to examine all of the relatives of that plant for other useful drugs. 

A research team in China identified a segment of DNA thought to be common to some medicinal plants in the family Fabaceae (the legume family) and worked to identify which species had this segment ( [link] ). After testing plant species in this family, the team found a DNA marker (a known location on a chromosome that enabled them to identify the species) present. Then, using the DNA to uncover phylogenetic relationships, the team could identify whether a newly discovered plant was in this family and assess its potential medicinal properties. Dalbergia sissoo (D. sissoo) is in the Fabaceae, or legume family. Scientists found that D. sissoo shares a DNA marker with species within the Fabaceae family that have antifungal properties. Subsequently, D. sissoo was shown to have fungicidal activity, supporting the idea that DNA markers can be used to screen for plants with potential medicinal properties. 

[link] Building Phylogenetic Trees 

How do scientists construct phylogenetic trees? After the homologous and analogous traits are sorted, scientists often organize the homologous traits using a system called cladistics . This system sorts organisms into clades: groups of organisms that descended from a single ancestor. For example, in [link] , all of the organisms in the orange region evolved from a single ancestor that had amniotic eggs. Consequently, all of these organisms also have amniotic eggs and make a single clade, also called a monophyletic group . Clades must include all of the descendants from a branch point. Visual Connection Lizards, rabbits, and humans all descend from a common ancestor that had an amniotic egg. Thus, lizards, rabbits, and humans all belong to the clade Amniota. Vertebrata is a larger clade that also includes fish and lamprey. 

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Clades can vary in size depending on which branch point is being referenced. The important factor is that all of the organisms in the clade or monophyletic group stem from a single point on the tree. This can be remembered because monophyletic breaks down into mono, meaning one, and phyletic, meaning evolutionary relationship. [link] shows various examples of clades. Notice how each clade comes from a single point, whereas the non-clade groups show branches that do not share a single point. Visual Connection All the organisms within a clade stem from a single point on the tree. A clade may contain multiple groups, as in the case of animals, fungi and plants, or a single group, as in the case of flagellates. Groups that diverge at a different branch point, or that do not include all groups in a single branch point, are not considered clades. 

[link] Shared Characteristics 

Organisms evolve from common ancestors and then diversify. Scientists use the phrase descent with modification because even though related organisms have many of the same characteristics and genetic codes, changes occur. This pattern repeats over and over as one goes through the phylogenetic tree of life: A change in the genetic makeup of an organism leads to a new trait which becomes prevalent in the group. Many organisms descend from this point and have this trait. New variations continue to arise: some are adaptive and persist, leading to new traits. With new traits, a new branch point is determined (go back to step 1 and repeat). 

If a characteristic is found in the ancestor of a group, it is considered a shared ancestral character because all of the organisms in the taxon or clade have that trait. The vertebrate in [link] is a shared ancestral character. Now consider the amniotic egg characteristic in the same figure. Only some of the organisms in [link] have this trait, and to those that do, it is called a shared derived character because this trait derived at some point but does not include all of the ancestors in the tree. 

The tricky aspect to shared ancestral and shared derived characters is the fact that these terms are relative. The same trait can be considered one or the other depending on the particular diagram being used. Returning to [link] , note that the amniotic egg is a shared ancestral character for the Amniota clade, while having hair is a shared derived character for some organisms in this group. These terms help scientists distinguish between clades in the building of phylogenetic trees. Choosing the Right Relationships 

Imagine being the person responsible for organizing all of the items in a department store properly an overwhelming task. Organizing the evolutionary relationships of all life on Earth proves much more difficult: scientists must span enormous blocks of time and work with information from long-extinct organisms. Trying to decipher the proper connections, especially given the presence of homologies and analogies, makes the task of building an accurate tree of life extraordinarily difficult. Add to that the advancement of DNA technology, which now provides large quantities of genetic sequences to be used and analyzed. Taxonomy is a subjective discipline: many organisms have more than one connection to each other, so each taxonomist will decide the order of connections. 

To aid in the tremendous task of describing phylogenies accurately, scientists often use a concept called maximum parsimony, which means that events occurred in the simplest, most obvious way. For example, if a group of people entered a forest preserve to go hiking, based on the principle of maximum parsimony, one could predict that most of the people would hike on established trails rather than forge new ones. 

For scientists deciphering evolutionary pathways, the same idea is used: the pathway of evolution probably includes the fewest major events that coincide with the evidence at hand. Starting with all of the homologous traits in a group of organisms, scientists look for the most obvious and simple order of evolutionary events that led to the occurrence of those traits. Link to Learning 

Head to this website to learn how maximum parsimony is used to create phylogenetic trees. 

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These tools and concepts are only a few of the strategies scientists use to tackle the task of revealing the evolutionary history of life on Earth. Recently, newer technologies have uncovered surprising discoveries with unexpected relationships, such as the fact that people seem to be more closely related to fungi than fungi are to plants. Sound unbelievable? As the information about DNA sequences grows, scientists will become closer to mapping the evolutionary history of all life on Earth. Activity 

Using a data set provided by your teacher or other sources, construct a phylogenetic tree or cladogram to reflect the evolutionary history among a group of organisms based on shared characteristics. Then share the phylogenetic tree or cladogram with peers for review and revision. Lab Investigation 

AP Biology Investigative Labs: Inquiry-Based Approach, Investigation 3: Comparing DNA Sequences to Understand Evolutionary Relationships with BLAST . Students will learn to use a common tool, BLAST, to compare several genes from different organisms and then use this information to construct a cladogram to determine evolutionary relatedness among species. Then students will use BLAST to track a gene(s) of choice through several species. Bioinformatics has many applications, including understanding genetic disease. Think About It 

Why must scientists distinguish between homologous and analogous characteristics before building phylogenetic trees? Do more closely related organisms share homologous or analogous traits? Which type of trait is used to support convergent or divergent evolution? This activity is an application of AP Learning Objective 1.19 and Science Practice 1.1, Learning Objective 1.18 and Science Practice 5.3, and Learning Objective 1.7 and Science Practice 1.3 because 1) students are asked to create a phylogenetic tree or cladogram based on evidence provided by a data set; 2) student s diagram should raise questions about the evolutionary history of the group; and 3) evolutionary history is subject to revision based on interpretation and new evidence. This lab investigation is an application of several AP Learning Objectives and Science Practices described above (Learning Objectives 1.11, 1.16, 1.17, and 1.18) because students will use BLAST to determine evolutionary relatedness among species based on molecular evidence/DNA sequences and then construct a cladogram based on that information. The Think About It question is an application of AP Learning Objective 1.17 and Science Practice 3.1 because students must distinguish between homologous and analogous characteristics when constructing phylogenetic trees. Only homologous traits are considered in establishing evolutionary relationships, because they are evidence of evolutionary change. Closely related organisms will share homologous traits, whereas analogous traits are often shared by only distantly related organisms. The study of convergent and divergent evolution also relies on the analysis of analogous and homologous traits. Section Summary 

To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections between organisms. Using morphologic and molecular data, scientists work to identify homologous characteristics and genes. Similarities between organisms can stem either from shared evolutionary history (homologies) or from separate evolutionary paths (analogies). Newer technologies can be used to help distinguish homologies from analogies. After homologous information is identified, scientists use cladistics to organize these events as a means to determine an evolutionary timeline. Scientists apply the concept of maximum parsimony, which states that the order of events probably occurred in the most obvious and simple way with the least amount of steps. For evolutionary events, this would be the path with the least number of major divergences that correlate with the evidence. Review Questions 

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[link] Glossary analogy (also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path cladistics system used to organize homologous traits to describe phylogenies maximum parsimony applying the simplest, most obvious way with the least number of steps molecular systematics technique using molecular evidence to identify phylogenetic relationships monophyletic group (also, clade) organisms that share a single ancestor shared ancestral character describes a characteristic on a phylogenetic tree that is shared by all organisms on the tree shared derived character describes a characteristic on a phylogenetic tree that is shared only by a certain clade of organisms cladograms visual representations of evolutionary relationships between organisms parsimony the simplest, most straightforward way of constructing phylogenetic and evolutionary relationships between organismsPerspectives on the Phylogenetic Tree Perspectives on the Phylogenetic Tree 

In this section, you will explore the following questions: What is horizontal gene transfer and its significance in constructing phylogenetic trees? How do prokaryotes and eukaryotes transfer genes horizontally? What are other models of phylogenetic relationships and how do they differ from the original phylogenetic tree concept? Connection for AP Courses 

Newer technologies have uncovered surprising discoveries with unexpected relationships among organisms, such as the fact that humans seems to be more closely related to fungi than fungi are to plants. (Think about that the next time you see a mushroom). As the information about DNA sequences grows, scientists will become closer to mapping a more accurate evolutionary history of all life on Earth. 

What makes phylogeny difficult, especially among prokaryotes, is the transfer of genes horizontally ( horizontal gene transfer , or HGT ) between unrelated species. Like mutations, HGT introduces genetic variation into the bacterial population. This passing of genes between species adds a layer of complexity to understanding relatedness. 

Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 of the AP Biology Curriculum Framework. The AP Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP exam questions. A learning objective merges required content with one or more of the seven science practices. 

Big Idea 1 The process of evolution drives and diversity and unity of life. 

Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 3.1 The student can pose scientific questions. Learning Objective 1.14 The student is able to pose scientific questions that correctly identify essential properties of shared, core life processes that provide insight into the history of life on Earth. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Learning Objective 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 

Big Idea 3 

Enduring Understanding 3.C The processing of genetic information is imperfect and is a source of genetic variation. Essential Knowledge 3.C.2 Biological systems have multiple processes that increase genetic variation. Science Practice 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Learning Objective 3.27 The student is able to construct an explanation of processes that increase variation within a population. 

The concepts of phylogenetic modeling are constantly changing. It is one of the most dynamic fields of study in all of biology. Over the last several decades, new research has challenged scientists ideas about how organisms are related. New models of these relationships have been proposed for consideration by the scientific community. 

Many phylogenetic trees have been shown as models of the evolutionary relationship among species. Phylogenetic trees originated with Charles Darwin, who sketched the first phylogenetic tree in 1837 ( [link] a ), which served as a pattern for subsequent studies for more than a century. The concept of a phylogenetic tree with a single trunk representing a common ancestor, with the branches representing the divergence of species from this ancestor, fits well with the structure of many common trees, such as the oak ( [link] b ). However, evidence from modern DNA sequence analysis and newly developed computer algorithms has caused skepticism about the validity of the standard tree model in the scientific community. The (a) concept of the tree of life goes back to an 1837 sketch by Charles Darwin. Like an (b) oak tree, the tree of life has a single trunk and many branches. (credit b: modification of work by "Amada44"/Wikimedia Commons) Limitations to the Classic Model 

Classical thinking about prokaryotic evolution, included in the classic tree model, is that species evolve clonally. That is, they produce offspring themselves with only random mutations causing the descent into the variety of modern-day and extinct species known to science. This view is somewhat complicated in eukaryotes that reproduce sexually, but the laws of Mendelian genetics explain the variation in offspring, again, to be a result of a mutation within the species. The concept of genes being transferred between unrelated species was not considered as a possibility until relatively recently. Horizontal gene transfer (HGT), also known as lateral gene transfer, is the transfer of genes between unrelated species. HGT has been shown to be an ever-present phenomenon, with many evolutionists postulating a major role for this process in evolution, thus complicating the simple tree model. Genes have been shown to be passed between species which are only distantly related using standard phylogeny, thus adding a layer of complexity to the understanding of phylogenetic relationships. 

The various ways that HGT occurs in prokaryotes is important to understanding phylogenies. Although at present HGT is not viewed as important to eukaryotic evolution, HGT does occur in this domain as well. Finally, as an example of the ultimate gene transfer, theories of genome fusion between symbiotic or endosymbiotic organisms have been proposed to explain an event of great importance the evolution of the first eukaryotic cell, without which humans could not have come into existence. Horizontal Gene Transfer 

Horizontal gene transfer (HGT) is the introduction of genetic material from one species to another species by mechanisms other than the vertical transmission from parent(s) to offspring. These transfers allow even distantly related species to share genes, influencing their phenotypes. It is thought that HGT is more prevalent in prokaryotes, but that only about 2% of the prokaryotic genome may be transferred by this process. Some researchers believe such estimates are premature: the actual importance of HGT to evolutionary processes must be viewed as a work in progress. As the phenomenon is investigated more thoroughly, it may be revealed to be more common. Many scientists believe that HGT and mutation appear to be (especially in prokaryotes) a significant source of genetic variation, which is the raw material for the process of natural selection. These transfers may occur between any two species that share an intimate relationship ( [link] ). Summary of Mechanisms of Prokaryotic and Eukaryotic HGT Mechanism Mode of Transmission Example Prokaryotes transformation DNA uptake many prokaryotes transduction bacteriophage (virus) bacteria conjugation pilus many prokaryotes gene transfer agents phage-like particles purple non-sulfur bacteria Eukaryotes from food organisms unknown aphid jumping genes transposons rice and millet plants epiphytes/parasites unknown yew tree fungi from viral infections HGT in Prokaryotes 

The mechanism of HGT has been shown to be quite common in the prokaryotic domains of Bacteria and Archaea, significantly changing the way their evolution is viewed. The majority of evolutionary models, such as in the Endosymbiont Theory, propose that eukaryotes descended from multiple prokaryotes, which makes HGT all the more important to understanding the phylogenetic relationships of all extant and extinct species. 

The fact that genes are transferred among common bacteria is well known to microbiology students. These gene transfers between species are the major mechanism whereby bacteria acquire resistance to antibiotics. Classically, this type of transfer has been thought to occur by three different mechanisms: Transformation: naked DNA is taken up by a bacteria Transduction: genes are transferred using a virus Conjugation: the use a hollow tube called a pilus to transfer genes between organisms 

More recently, a fourth mechanism of gene transfer between prokaryotes has been discovered. Small, virus-like particles called gene transfer agents (GTAs) transfer random genomic segments from one species of prokaryote to another. GTAs have been shown to be responsible for genetic changes, sometimes at a very high frequency compared to other evolutionary processes. The first GTA was characterized in 1974 using purple, non-sulfur bacteria. These GTAs, which are thought to be bacteriophages that lost the ability to reproduce on their own, carry random pieces of DNA from one organism to another. The ability of GTAs to act with high frequency has been demonstrated in controlled studies using marine bacteria. Gene transfer events in marine prokaryotes, either by GTAs or by viruses, have been estimated to be as high as 10 13 per year in the Mediterranean Sea alone. GTAs and viruses are thought to be efficient HGT vehicles with a major impact on prokaryotic evolution. 

As a consequence of this modern DNA analysis, the idea that eukaryotes evolved directly from Archaea has fallen out of favor. While eukaryotes share many features that are absent in bacteria, such as the TATA box (found in the promoter region of many genes), the discovery that some eukaryotic genes were more homologous with bacterial DNA than Archaea DNA made this idea less tenable. Furthermore, the fusion of genomes from Archaea and Bacteria by endosymbiosis has been proposed as the ultimate event in eukaryotic evolution. HGT in Eukaryotes 

Although it is easy to see how prokaryotes exchange genetic material by HGT, it was initially thought that this process was absent in eukaryotes. After all, prokaryotes are but single cells exposed directly to their environment, whereas the sex cells of multicellular organisms are usually sequestered in protected parts of the body. It follows from this idea that the gene transfers between multicellular eukaryotes should be more difficult. Indeed, it is thought that this process is rarer in eukaryotes and has a much smaller evolutionary impact than in prokaryotes. In spite of this fact, HGT between distantly related organisms has been demonstrated in several eukaryotic species, and it is possible that more examples will be discovered in the future. 

In plants, gene transfer has been observed in species that cannot cross-pollinate by normal means. Transposons or jumping genes have been shown to transfer between rice and millet plant species. Furthermore, fungal species feeding on yew trees, from which the anti-cancer drug TAXOL is derived from the bark, have acquired the ability to make taxol themselves, a clear example of gene transfer. 

In animals, a particularly interesting example of HGT occurs within the aphid species ( [link] ). Aphids are insects that vary in color based on carotenoid content. Carotenoids are pigments made by a variety of plants, fungi, and microbes, and they serve a variety of functions in animals, who obtain these chemicals from their food. Humans require carotenoids to synthesize vitamin A, and we obtain them by eating orange fruits and vegetables: carrots, apricots, mangoes, and sweet potatoes. On the other hand, aphids have acquired the ability to make the carotenoids on their own. According to DNA analysis, this ability is due to the transfer of fungal genes into the insect by HGT, presumably as the insect consumed fungi for food. A carotenoid enzyme called a desaturase is responsible for the red coloration seen in certain aphids, and it has been further shown that when this gene is inactivated by mutation, the aphids revert back to their more common green color ( [link] ). (a) Red aphids get their color from red carotenoid pigment. Genes necessary to make this pigment are present in certain fungi, and scientists speculate that aphids acquired these genes through HGT after consuming fungi for food. If genes for making carotenoids are inactivated by mutation, the aphids revert back to (b) their green color. Red coloration makes the aphids a lot more conspicuous to predators, but evidence suggests that red aphids are more resistant to insecticides than green ones. Thus, red aphids may be more fit to survive in some environments than green ones. (credit a: modification of work by Benny Mazur; credit b: modification of work by Mick Talbot) 

Barbara McClintock (1902 1992) discovered transposons while working on maize genetics. 

[link] Genome Fusion and the Evolution of Eukaryotes 

Scientists believe the ultimate in HGT occurs through genome fusion between different species of prokaryotes when two symbiotic organisms become endosymbiotic. This occurs when one species is taken inside the cytoplasm of another species, which ultimately results in a genome consisting of genes from both the endosymbiont and the host. This mechanism is an aspect of the Endosymbiont Theory, which is accepted by a majority of biologists as the mechanism whereby eukaryotic cells obtained their mitochondria and chloroplasts. However, the role of endosymbiosis in the development of the nucleus is more controversial. Nuclear and mitochondrial DNA are thought to be of different (separate) evolutionary origin, with the mitochondrial DNA being derived from the circular genomes of bacteria that were engulfed by ancient prokaryotic cells. Mitochondrial DNA can be regarded as the smallest chromosome. Interestingly enough, mitochondrial DNA is inherited only from the mother. The mitochondrial DNA degrades in sperm when the sperm degrades in the fertilized egg or in other instances when the mitochondria located in the flagellum of the sperm fails to enter the egg. 

Within the past decade, the process of genome fusion by endosymbiosis has been proposed by James Lake of the UCLA/NASA Astrobiology Institute to be responsible for the evolution of the first eukaryotic cells ( [link] a ). Using DNA analysis and a new mathematical algorithm called conditioned reconstruction (CR), his laboratory proposed that eukaryotic cells developed from an endosymbiotic gene fusion between two species, one an Archaea and the other a Bacteria. As mentioned, some eukaryotic genes resemble those of Archaea, whereas others resemble those from Bacteria. An endosymbiotic fusion event, such as Lake has proposed, would clearly explain this observation. On the other hand, this work is new and the CR algorithm is relatively unsubstantiated, which causes many scientists to resist this hypothesis. 

More recent work by Lake ( [link] b ) proposes that gram-negative bacteria, which are unique within their domain in that they contain two lipid bilayer membranes, indeed resulted from an endosymbiotic fusion of archaeal and bacterial species. The double membrane would be a direct result of the endosymbiosis, with the endosymbiont picking up the second membrane from the host as it was internalized. This mechanism has also been used to explain the double membranes found in mitochondria and chloroplasts. Lake s work is not without skepticism, and the ideas are still debated within the biological science community. In addition to Lake s hypothesis, there are several other competing theories as to the origin of eukaryotes. How did the eukaryotic nucleus evolve? One theory is that the prokaryotic cells produced an additional membrane that surrounded the bacterial chromosome. Some bacteria have the DNA enclosed by two membranes; however, there is no evidence of a nucleolus or nuclear pores. Other proteobacteria also have membrane-bound chromosomes. If the eukaryotic nucleus evolved this way, we would expect one of the two types of prokaryotes to be more closely related to eukaryotes. The theory that mitochondria and chloroplasts are endosymbiotic in origin is now widely accepted. More controversial is the proposal that (a) the eukaryotic nucleus resulted from the fusion of archaeal and bacterial genomes, and that (b) Gram-negative bacteria, which have two membranes, resulted from the fusion of Archaea and Gram-positive bacteria, each of which has a single membrane. 

The nucleus-first hypothesis proposes that the nucleus evolved in prokaryotes first ( [link] a ), followed by a later fusion of the new eukaryote with bacteria that became mitochondria. The mitochondria-first hypothesis proposes that mitochondria were first established in a prokaryotic host ( [link] b ), which subsequently acquired a nucleus, by fusion or other mechanisms, to become the first eukaryotic cell. Most interestingly, the eukaryote-first hypothesis proposes that prokaryotes actually evolved from eukaryotes by losing genes and complexity ( [link] c ). All of these hypotheses are testable. Only time and more experimentation will determine which hypothesis is best supported by data. Three alternate hypotheses of eukaryotic and prokaryotic evolution are (a) the nucleus-first hypothesis, (b) the mitochondrion-first hypothesis, and (c) the eukaryote-first hypothesis. Web and Network Models 

The recognition of the importance of HGT, especially in the evolution of prokaryotes, has caused some to propose abandoning the classic tree of life model. In 1999, W. Ford Doolittle proposed a phylogenetic model that resembles a web or a network more than a tree. The hypothesis is that eukaryotes evolved not from a single prokaryotic ancestor, but from a pool of many species that were sharing genes by HGT mechanisms. As shown in [link] a , some individual prokaryotes were responsible for transferring the bacteria that caused mitochondrial development to the new eukaryotes, whereas other species transferred the bacteria that gave rise to chloroplasts. This model is often called the web of life . In an effort to save the tree analogy, some have proposed using the Ficus tree ( [link] b ) with its multiple trunks as a phylogenetic to represent a diminished evolutionary role for HGT. In the (a) phylogenetic model proposed by W. Ford Doolittle, the tree of life arose from a community of ancestral cells, has multiple trunks, and has connections between branches where horizontal gene transfer has occurred. Visually, this concept is better represented by (b) the multi-trunked Ficus than by the single trunk of the oak similar to the tree drawn by Darwin [link] . (credit b: modification of work by "psyberartist"/Flickr) Ring of Life Models 

Others have proposed abandoning any tree-like model of phylogeny in favor of a ring structure, the so-called ring of life ( [link] ); a phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes. Lake, again using the conditioned reconstruction algorithm, proposes a ring-like model in which species of all three domains Archaea, Bacteria, and Eukarya evolved from a single pool of gene-swapping prokaryotes. His laboratory proposes that this structure is the best fit for data from extensive DNA analyses performed in his laboratory, and that the ring model is the only one that adequately takes HGT and genomic fusion into account. However, other phylogeneticists remain highly skeptical of this model. According to the ring of life phylogenetic model, the three domains of life evolved from a pool of primitive prokaryotes. 

In summary, the tree of life model proposed by Darwin must be modified to include HGT. Does this mean abandoning the tree model completely? Even Lake argues that all attempts should be made to discover some modification of the tree model to allow it to accurately fit his data, and only the inability to do so will sway people toward his ring proposal. 

This doesn t mean a tree, web, or a ring will correlate completely to an accurate description of phylogenetic relationships of life. A consequence of the new thinking about phylogenetic models is the idea that Darwin s original conception of the phylogenetic tree is too simple, but made sense based on what was known at the time. However, the search for a more useful model moves on: each model serving as hypotheses to be tested with the possibility of developing new models. This is how science advances. These models are used as visualizations to help construct hypothetical evolutionary relationships and understand the massive amount of data being analyzed. Section Summary 

The phylogenetic tree, first used by Darwin, is the classic tree of life model describing phylogenetic relationships among species, and the most common model used today. New ideas about HGT and genome fusion have caused some to suggest revising the model to resemble webs or rings. Review Questions 

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[link] Glossary eukaryote-first hypothesis proposal that prokaryotes evolved from eukaryotes gene transfer agent (GTA) bacteriophage-like particle that transfers random genomic segments from one species of prokaryote to another genome fusion fusion of two prokaryotic genomes, presumably by endosymbiosis horizontal gene transfer (HGT) (also, lateral gene transfer) transfer of genes between unrelated species mitochondria-first hypothesis proposal that prokaryotes acquired a mitochondrion first, followed by nuclear development nucleus-first hypothesis proposal that prokaryotes acquired a nucleus first, and then the mitochondrion ring of life phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes web of life phylogenetic model that attempts to incorporate the effects of horizontal gene transfer on evolution

Introduction Introduction class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" A plane slows down as it comes in for landing in St. Maarten. Its acceleration is in the opposite direction of its velocity. (credit: Steve Conry, Flickr) 

Ask the students to give definitions of acceleration. Dispel any misconceptions such as, acceleration means very high speed or going faster. Emphasize that acceleration does not just indicate speeding up; acceleration can also include slowing down or changing direction. Explain that acceleration is the change in either the magnitude or direction of velocity, or both. Have the students list the objects in the opening image that are moving. Then ask which are definitely accelerating and which might be accelerating. Review the use of + and signs as they relate to acceleration and velocity. Explain that, when studying motion, these symbols are often used to indicate the direction of motion. The + symbol typically represents motion that is to the right or upward, whereas typically represents motion that is to the left or downward. 

You may have heard the term accelerator , referring to the gas pedal in a car. When the gas pedal is pushed down, the flow of gasoline to the engine increases, which increases the car s velocity . Pushing on the gas pedal results in acceleration because the velocity of the car increases, and acceleration is defined as a change in velocity. You need two quantities to define velocity: a speed and a direction. Changing either of these quantities (or both together) changes the velocity. You may be surprised to learn that pushing on the brake pedal or turning the steering wheel also causes acceleration. The first reduces the speed and so changes the velocity, and the second changes the direction and so also changes the velocity. 

In fact, any change in velocity whether positive, negative, directional, or any combination of these is an acceleration . The plane in the picture is accelerating because its velocity is decreasing as it prepares to land. To begin our study of acceleration, we need to have a clear understanding of what it means. 

Before students begin this chapter, it is useful to review the following concepts: Significant figures: demonstrate how to obtain the proper number of significant figures when adding and multiplying. Scientific notation and how it expresses significant figures. Converting units: demonstrate how to convert from km/h to m/s. Show how units cancel in calculations. Calculating average: demonstrate how to calculate the average of two numbers. Commonly used terms: explain that constant means unchanging, so constant acceleration refers to acceleration that is not changing in time. Explain that initial means starting or beginning, so the initial time is the time at which the action of interest begins. Explain that an object that is not moving is often described in physics as being at rest. Review conventions of coordinate systems. Review kinematics concepts introduced earlier: vectors, displacement, velocity, speed.Acceleration Acceleration Section Learning Objectives 

By the end of this section, you will be able to: Explain acceleration and determine the direction and magnitude of acceleration in one dimension. Analyze motion in one dimension using kinematic equations and graphic representations. 

The Learning Objectives in this section will help your students master the following TEKS: (4A) : Generate and interpret graphs and charts describing different types of motion, including the use of real-time technology such as motion detectors or photogates. (4B) : Describe and analyze motion in one dimension using equations with the concepts of distance, displacement, speed, average velocity, instantaneous velocity, and acceleration. Section Key Terms average acceleration instantaneous acceleration negative acceleration 

[BL] [OL] Begin a general discussion about acceleration and deceleration. Ask for examples of both. Explain that deceleration is not used in physics because acceleration can be positive or negative. Lead the students to their topics of interest, such as motor vehicles or sports. Explain that the capital Greek letter delta always means final minus initial and that the net change may be zero, positive, or negative. 

[AL] See how much students remember about vectors. What does a vector arrow represent? Ask them to name some quantities that are vectors and some that are scalars. Defining Acceleration 

Throughout this chapter we will use the following terms: time , displacement , velocity , and acceleration . Recall that each of these terms has a designated variable and SI unit of measurement as follows: Time : t , measured in seconds (s) Displacement : d , measured in meters (m) Velocity : v , measured in meters per second (m/s) Acceleration : a , measured in meters per second per second (m/s 2 , also called meters per second squared) Also note: means change in. The subscript 0 refers to an initial value (sometimes subscript i is used to refer to initial value). The subscript f refers to final value. A bar over a symbol, such as a a , means average. 

[BL] Review the definitions of the terms: time , displacement , velocity , and acceleration . Point out that the variables commonly used to represent these quantities are the first letters of the corresponding term. 

[OL] Verify that the students know the SI units in which time, displacement, velocity, and acceleration are expressed. Note that these are some of the seven base units of the metric system. Explain that converting to base units is a good first step when calculating these quantities. Explain the meaning of seconds squared in the denominator of the units of acceleration. 

[AL] Review all the base units of the metric system. Explain how these units are interrelated. For example, show how the length is defined by time. 

[BL] [OL] Use the equation a = v t = v f v 0 t f t 0 a = v t = v f v 0 t f t 0 to emphasize the relationship between and the subscripts f and 0. Distinguish between constant and variable acceleration. There could be confusion here, especially in the case of increasing acceleration. Be sure students understand that the word deceleration is not used in physics and that acceleration can be positive or negative. 

[AL] See if students can use the concept of acceleration to understand confusing statements such as a decrease in the rate of increase. For example, use the concept of acceleration to analyze the statement the rate of increase in the cost of health care is decreasing. If the increase in the cost is defined as positive, then the acceleration in the cost of health care would be negative. 

[OL] The arrow for acceleration that points opposite to the arrow for velocity a may be confusing. Explain that it points in the direction opposite the velocity because it is the velocity is getting smaller (i.e., the velocity arrow is getting shorter). 

Acceleration is the change in velocity divided by a period of time during which the change occurs. The SI units of velocity are m/s and the SI units for time are s, so the SI units for acceleration are m/s 2 . Average acceleration is given by a = v t = v f v 0 t f t 0 a = v t = v f v 0 t f t 0 

Average acceleration is distinguished from instantaneous acceleration , which is acceleration at a specific instant in time. The magnitude of acceleration is often not constant over time. For example, runners in a race accelerate at a greater rate in the first second of a race than during the following seconds. You do not need to know all the instantaneous acceleration at all times to calculate average acceleration. All you need to know is the change in velocity (i.e., the final velocity minus the initial velocity) and the change in time (i.e., the final time minus the initial time), as shown in the formula. Note that the average acceleration can be positive, negative, or zero. A negative acceleration is simply an acceleration in the negative direction. 

Keep in mind that, although acceleration points in the same direction as the change in velocity, it is not always in the direction of the velocity itself. When an object slows down, its acceleration is opposite to the direction of its velocity. In everyday language, this is called deceleration, but in physics, it is acceleration (whose direction happens to be opposite that of the velocity). For now, let us assume that motion to the right along the x -axis is positive and motion to the left is negative. 

[link] shows a car with positive acceleration in (a) and negative acceleration in (b). The arrows represent vectors showing the direction and magnitude of velocity and acceleration. The car is speeding up in (a) and slowing down in (b). 

Velocity and acceleration are both vector quantities . Recall that vectors have both magnitude and direction. An object travelling at a constant velocity therefore having no acceleration does accelerate if it changes direction. This is why turning the steering wheel of a moving car makes the car accelerate: its velocity changes direction. The Moving Man 

With this animation, you can produce both variations of acceleration and velocity shown in [link] , plus a few more. Vary the velocity and acceleration by sliding the red and green markers along the scales. Keeping the velocity marker near zero will make the effect of acceleration more obvious. Try changing acceleration from positive to negative while the man is moving. We will come back to this animation and look at the Charts view when we study graphical representation of motion. Click here for the simulation 

Have students use a very low setting for velocity and acceleration because it is easier to see how the motion changes. Show them how setting velocity as positive and acceleration as negative creates the motion that resembles that of an object thrown into the air. 

[link] Calculating Average Acceleration 

Look back at the equation for average acceleration. You can see that the calculation of average acceleration involves three values: change in time, t ; change in velocity, v ; and acceleration, a . 

Change in time is often stated as a time interval, and change in velocity can often be calculated by subtracting the initial velocity from the final velocity. Average acceleration is then simply change in velocity divided by change in time. Before you begin calculating, be sure that all distances and times have been converted to meters and seconds. Look at these examples of acceleration of a subway train. 

[BL] [OL] Before beginning the calculations, verify that students understand the equation for acceleration. Do they understand what it means when quantities have a plus or minus sign? Do they understand the units for each variable? An Accelerating Subway Train 

A subway train accelerates from rest to 30.0 km/h in 20.0 s. What is the average acceleration during that time interval? Strategy 

Start by making a simple sketch: 

This problem involves four steps: Convert to units of meters and seconds. Determine the change in velocity. Determine the change in time. Use these values to calculate the average acceleration. Solution Identify the knowns. Be sure to read the problem for given information, which may not look like numbers. When the problem states that the train starts from rest, you can write down that the initial velocity is 0 m/s. Therefore: v 0 = 0; v f = 30.0 km/h; and t = 20.0 s 

Convert the units: 30.0 km h 10 3 m 1 km 1 h 3600 s = 8.333 m s 30.0 km h 10 3 m 1 km 1 h 3600 s = 8.333 m s Calculate change in velocity, v = v f v 0 = 8.333 m/s 0 = + 8.333 m/s v = v f v 0 = 8.333 m/s 0 = + 8.333 m/s , where the plus sign means the change in velocity is to the right. 

We know t , so all we have to do is insert the known values into the formula for average acceleration: a = v t = 8.333 m/s 20.0 s = + 0.417 m s 2 a = v t = 8.333 m/s 20.0 s = + 0.417 m s 2 Discussion 

The plus sign in the answer means that acceleration is to the right. This is a reasonable conclusion because the train starts from rest and ends up with a velocity directed to the right (i.e., positive). So acceleration is in the same direction as the change in velocity, as it should be. 

Note that extra digits were carried along and rounding off to the correct number of significant figures, 3, was not done until the final answer was calculated. An Accelerating Subway Train 

Now, suppose that, at the end of its trip, the train slows to a stop in 8.00 s from a speed of 30.0 km/h. What is its average acceleration during this time? Strategy 

Again, make a simple sketch: 

In this case, the train is decelerating and its acceleration is negative because it is pointing to the left. As in the previous example, we must find the change in velocity and the change in time, then solve for acceleration. Solution Identify the knowns: v 0 = 30.0 km/h; v f = 0; t = 8.00 s. Convert the units: From the first problem, we know that 30.0 km/h = 8.333 m/s. Calculate change in velocity, v = v f v 0 = 0 8.333 m/s = 8.333 m/s v = v f v 0 = 0 8.333 m/s = 8.333 m/s , where the minus sign means that the change in velocity points to the left. 

We know t = 8.00 s, so all we have to do is insert the known values into the equation for average acceleration: a = v t = 8.333 m/s 8.00 s = 1.04 m s 2 a = v t = 8.333 m/s 8.00 s = 1.04 m s 2 Discussion 

The minus sign indicates that acceleration is to the left. This is reasonable because the train initially has a positive velocity in this problem, and a negative acceleration would reduce the velocity. Again, acceleration is in the same direction as the change in velocity, which is negative in this case. This acceleration can be called a deceleration because it has a direction opposite to the velocity. 

Help students see the relationship between the direction of the vector arrows and the plus and minus signs. Explain that one indication of the sign for acceleration is that it is in the direction opposite that of the velocity. Also point out that correctly identifying the initial and final speeds will result in the correct sign for acceleration. It is easier to get plus and minus signs correct if you always assume that motion is away from 0 and toward positive values on the x axis. This way v always starts off being positive and points to the right. If speed is increasing, then acceleration is positive and also points to the right. If speed is decreasing, then acceleration is negative and points to the left. It is a good idea to carry two extra significant figures from step-to-step when making calculations. Do not round off with each step. When you arrive at the final answer, apply the rules of significant figures for the operations you carried out and round to the correct number of digits. Sometimes this will make your answer slightly more accurate. Practice Problems 

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[link] Acceleration 

This video shows the basic calculation of acceleration and some useful unit conversions. 

Ask students to note the explanation of units and the identification of the vector quantities. Tell them the calculations demonstrated in the video are fairly straightforward and that the definitions given for displacement, elapsed time, velocity, and acceleration should be clear. 

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[link] Measure the Acceleration of a Bicycle on a Slope 

In this lab you will take measurements to determine if the acceleration of a moving bicycle is constant. If the acceleration is constant, then the following relationships hold: v = d t = v 0 + v f 2 v = d t = v 0 + v f 2 If v 0 = 0 v 0 = 0 , then v f = 2 v v f = 2 v and a = v f t a = v f t . 

You will work in pairs to measure and record data for a bicycle coasting down an incline on a uniform, gentle slope. The data will consist of distances traveled and elapsed times. Find an open area to minimize the risk of injury during this lab. stopwatch measuring tape bicycle Find a gentle, paved slope, such as an incline on a bike path. The more gentle the slope, the more accurate your data is likely to be. Mark uniform distances along the slope, such as 5 m, 10 m, etc. Determine the following roles: the bike rider, the timer, and the recorder. The recorder should create a data table to collect the distance and time data. Have the rider at the starting point at rest on the bike. When the timer calls Start, the timer starts the stopwatch and the rider begins coasting down the slope on the bike without pedaling. Have the timer call out the elapsed times as the bike passes each marked point. The recorder should record the times in the data table. It may be necessary to repeat the process to practice roles and make necessary adjustments. Once acceptable data has been recorded, switch roles. Repeat Steps 3 5 to collect a second set of data. Switch roles again to collect a third set of data. Calculate average acceleration for each set of distance-time data. If your result for a a is not the same for different pairs of v and t , then acceleration is not constant. Interpret your results. 

Explain that two factors that could prevent uniform acceleration are (i) friction between the tires and the pavement and in the bicycle axles, and (ii) air resistance. Discuss methods for minimizing these factors (e.g., selecting a smooth surface for the bike to coast, greasing the axels, etc.). Explain that friction will only decrease acceleration, but air resistance to a tail wind would increase acceleration. Discuss why it would be difficult to study constant acceleration if students were to pedal the bicycle. Note that the given kinematic equation that is valid for constant acceleration, which is presented at the start of the Snap Lab!, will be presented in further detail in the following section. 

Prior to the lab, investigate appropriate areas around the school that have gentle, uniform slopes. Should the number of bicycles be limited, consider conducting the lab as a whole class or in larger clusters. Ensure that the planned paths of student groups not cross and that there is adequate space for riders to stop without risk of injury. 

[link] Check Your Understanding 

Use these questions to assess student achievement of the section s Learning Objectives. If students are struggling with a specific objective, these questions will help identify which and direct students to the relevant content. 

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[link] Section Summary Acceleration is the rate of change of velocity and may be negative or positive. Average acceleration is expressed in m/s 2 and, in one dimension, can be calculated by using a = v t = v f v 0 t f t o a = v t = v f v 0 t f t o Key Equations Average acceleration a = v t = v f v 0 t f t o a = v t = v f v 0 t f t o Concept Items 

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[link] Glossary average acceleration change in velocity divided by the time interval over which it changed instantaneous acceleration rate of change of velocity at a specific instant in time negative acceleration acceleration in the negative directionRepresenting Acceleration with Equations and Graphs Representing Acceleration with Equations and Graphs Section Learning Objectives 

By the end of this section, you will be able to: Explain the kinematic equations related to acceleration and illustrate them with graphs. Apply the kinematic equations and related graphs to problems involving acceleration. 

The Learning Objectives in this section will help your students master the following TEKS: (4A) : Generate and interpret graphs and charts describing different types of motion, including the use of real-time technology such as motion detectors or photogates. (4B) : Describe and analyze motion in one dimension using equations with the concepts of distance, displacement, speed, average velocity, instantaneous velocity, and acceleration. Section Key Terms acceleration due to gravity kinematic equations uniform acceleration 

[BL] Briefly review displacement, time, velocity, and acceleration; their variables, and their units. 

[OL] [AL] Explain that this section introduces five equations that allow us to solve a wider range of problems than just finding acceleration from time and velocity. Review graphical analysis, including axes, algebraic signs, how to designate points on a coordinate plane, i.e., ( x , y ), slopes and intercepts. Explain that these equations can also be represented graphically. How the Kinematic Equations are Related to Acceleration 

We are studying concepts related to motion: time, displacement, velocity , and especially acceleration. We are only concerned with motion in one dimension. The kinematic equations apply to conditions of constant acceleration and show how these concepts are related. Constant acceleration is acceleration that does not change over time. The first kinematic equation relates displacement d , average velocity v v , and time t . 

d = d 0 + v t the initial displacement d 0 is often 0, in which case the equation can be written as v = d t d = d 0 + v t the initial displacement d 0 is often 0, in which case the equation can be written as v = d t 

This equation says that average velocity is displacement per unit time. We will express velocity in meters per second. If we graph displacement versus time, as in [link] , the slope will be the velocity. Whenever a rate, such as velocity, is represented graphically, time is usually taken to be the independent variable and is plotted along the x axis. The slope of displacement versus time is velocity. 

Another expression for average velocity v v is simply the initial velocity plus the final velocity divided by two: v = v 0 + v f 2 v = v 0 + v f 2 

Now we come to our main concern of this chapter; namely, the kinematic equations that describe motion with constant acceleration. Acceleration is the rate at which velocity increases, so velocity at any point equals initial velocity plus acceleration multiplied by time: v = v 0 + a t Also , if we start from rest ( v 0 = 0 ), we can write a = v t v = v 0 + a t Also , if we start from rest ( v 0 = 0 ), we can write a = v t 

Note that Equation 3 does not have displacement in it. Therefore, if you do not know the displacement and are not trying to solve for a displacement, this equation might be a good one to use. 

Equation 3 is represented by the graph in [link] . The slope of velocity versus time is acceleration. 

The fourth kinematic equation shows how displacement is related to acceleration. d = d 0 + v 0 t + 1 2 a t 2 d = d 0 + v 0 t + 1 2 a t 2 

When starting at the origin, d 0 = 0 d 0 = 0 and, when starting from rest, v 0 = 0 v 0 = 0 , in which case the equation can be written as a = 2 d t 2 a = 2 d t 2 

This equation tells us that, for constant acceleration, the slope of a plot of 2 d versus t 2 is acceleration, as shown in [link] . When acceleration is constant, the slope of 2 d versus t 2 gives the acceleration. 

The final kinematic equation relates velocity, acceleration, and displacement: v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) 

This equation is useful to when we do not know (or need to know) the time. 

When starting from rest, Equation 6 simplifies to: a = v 2 2 d a = v 2 2 d 

According to this equation, a graph of velocity squared versus twice the displacement will have a slope equal to acceleration. 

Note that, in reality, knowns and unknowns will vary. Sometimes you will want to rearrange a kinematic equation so that the knowns are the values on the axes and the unknown is the slope. Sometimes the intercept will not be at the origin (0, 0). This will happen when v 0 or d 0 is not 0. This will be the case when the object of interest is already in motion or the motion begins at some point other than at the origin of the coordinate system. 

[BL] Be sure everyone is completely comfortable with the idea that velocity is displacement divided by the time during which the displacement occurs. Use everyday examples. 

[OL] Remind students that they studied velocity in early chapters. Relate the simplified equation v = d t v = d t to a graph of displacement versus time. Point out the of the plot starts at (0,0) because the initial velocity is zero. Pick a segment on the graph and explain how finding the slope at this segment. Explain that [link] would show a straight line if velocity were changing; that is, if the object were accelerating. Show how the graph would change for both negative and positive acceleration. 

[OL] Build on the understanding of velocity to introduce acceleration. Contrast constant velocity with changing velocity. Use everyday examples from transportation, sports, or amusement park rides. Explain that [link] represents constant acceleration because it is a straight line. Give examples of increasing, decreasing, and constant acceleration and explain how each affects the shape of plots of velocity versus time. 

[OL] [AL] Ask students why all three of the plots are straight lines. Refer to the graph of 2 d vs t 2 and explain why this is a straight line whereas d vs t would be nonlinear. The Moving Man (Part 2) 

Look at the Moving Man video again and this time watch the Charts view. Again, vary the velocity and acceleration by sliding the red and green markers along the scales. Keeping the velocity marker near zero will make the effect of acceleration more obvious. Observe how the graphs of position, velocity, and acceleration vary with time. Note which are linear plots and which are not. Click here for the simulation 

Ask the students to click the Charts option and adjust the settings for the animation to reproduce the plots found in [link] and [link] . 

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The kinematic equations are applicable when you have constant acceleration. d = d 0 + v t d = d 0 + v t , or v = d t v = d t when d 0 = 0. v = v 0 + v f 2 v = v 0 + v f 2 v = v 0 + a t v = v 0 + a t , or a = v t a = v t when v 0 = 0. d = d 0 + v 0 t + 1 2 a t 2 d = d 0 + v 0 t + 1 2 a t 2 , or a = 2 d t 2 a = 2 d t 2 when d 0 = 0 and v 0 = 0. v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) , or a = 2 d t 2 a = 2 d t 2 when d 0 = 0 and v 0 = 0. 

[OL] Go through the algebra to show how the kinematic equations can be simplified when some of the values are zero. Note that any motion starting or ending in a motionless state will simplify the equations. Applying Kinematic Equations to Situations of Constant Acceleration 

Problem-solving skills are essential to success in a science and in life in general. The ability to apply broad physical principles, which are often represented by equations, to specific situations is a very powerful form of knowledge. It is much more powerful than memorizing a list of facts. Analytical skills and problem-solving abilities can be applied to new situations, whereas a list of facts cannot be made long enough to contain every possible circumstance. Such analytical skills will be developed by solving problems in this text and will be useful for understanding physics and science in general throughout your life. Problem-Solving Steps 

While no single step-by-step method works for every problem, the following general procedures facilitate problem solving and make the answers more meaningful. A certain amount of creativity and insight are required as well. Examine the situation to determine which physical principles are involved. It is vital to draw a simple sketch at the outset. Decide which direction is positive and note that on your sketch. Identify the knowns: make a list of what information is given or can be inferred from the problem statement. Remember, not all given information will be in the form of a number with units in the problem. If something starts from rest, we know the initial velocity is zero. If something stops, we know the final velocity is zero Identify the unknowns: decide exactly what needs to be determined in the problem. Find an equation or set of equations that can help you solve the problem. Your list of knowns and unknowns can help here. For example, if time is not needed or not given, Equation 6, which does not include time, could be useful. Insert the knowns along with their units into the appropriate equation and obtain numerical solutions complete with units. This step produces the numerical answer; it also provides a check on units that can help you find errors. If the units of the answer are incorrect, then an error has been made. Check the answer to see if it is reasonable: does it make sense? This final step is extremely important because the goal of physics is to accurately describe nature. To see if the answer is reasonable, check its magnitude, its sign, and its units. Are the significant figures correct? Summary of Problem Solving Determine the knowns and unknowns. Find an equation that expresses the unknown in terms of the knowns. More than one unknown means more than one equation is needed. Solve the equation or equations. Be sure units and significant figures are correct. Check whether the answer is reasonable. 

[BL] [OL] [AL] Consider starting with the simplified summary of problem solving and then expand it to the more wordy description above. Stress that this is not a strict recipe that can solve all problems. Applying analytical skills is still required. If the preliminary analysis is correct and the knowns and unknowns are correctly sorted, the rest should go be correct. Try applying the method to some non-mathematical everyday problems. Ask for suggestions. Drag Racing Smoke rises from the tires of a dragster at the beginning of a drag race. (credit: Lt. Col. William Thurmond. Photo courtesy of U.S. Army.) 

The object of the sport of drag racing is acceleration. Period! The races take place from a standing start on a straight one-quarter-mile (402 m) track. Usually two cars race side by side, and the winner is the driver who gets the car past the quarter-mile point first. At the finish line, the cars may be going more than 300 miles per hour (134 m/s). The driver then deploys a parachute to bring the car to a stop because it is unsafe to brake at such high speeds. The cars, called dragsters, are capable of accelerating at 26 m/s 2 . By comparison, a typical sports car that is available to the general public can accelerate at about 5 m/s 2 . 

Several measurements are taken during each drag race: Reaction time is the time between the starting signal and when the front of the car crosses the starting line. Elapsed time is the time from when the vehicle crosses the starting line to when it crosses the finish line. The record is a little over 3 s. Speed is the average speed during the last 20 m before the finish line. The record is a little under 400 mph. 

The video shows a race between two dragsters powered by jet engines. The actual race lasts about four seconds and is near the end of the video . [link] 

Explain the direction and magnitude of acceleration and velocity vectors before and after the braking chute is deployed. Explain that mile is 440 yards. If any students are on the track team, you might ask them to describe this distance. Compare record times for this track event to 4 seconds. 

[link] Acceleration of a Dragster 

The time it takes for a dragster to cross the finish line is unknown. The dragster accelerates from rest at 26 m/s 2 for a quarter mile (0.250 mi). What is the final velocity of the dragster? Strategy 

The equation v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) is ideally suited to this task because it gives the velocity from acceleration and displacement, without involving the time. Solution Convert miles to meters: ( 0.250 mi ) 1609 m 1 mi = 402 m ( 0.250 mi ) 1609 m 1 mi = 402 m Identify the known values. We know that v 0 = 0 since the dragster starts from rest, and we know that the distance traveled, d d 0 is 402 m. Finally, the acceleration is constant at a = 26.0 m/s 2 . Insert the knowns into the equation v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) and solve for v : v 2 = 0 + 2 ( 26.0 m s 2 ) ( 402 m ) = 2.09 10 4 m 2 s 2 v 2 = 0 + 2 ( 26.0 m s 2 ) ( 402 m ) = 2.09 10 4 m 2 s 2 

Taking the square root gives us: v = 2.09 10 4 m 2 s 2 = 145 m s v = 2.09 10 4 m 2 s 2 = 145 m s Discussion 

145 m/s is about 522 km/hour or about 324 mi/h, but even this breakneck speed is short of the record for the quarter mile. Also, note that a square root has two values. We took the positive value because we know that the velocity must be in the same direction as the acceleration for the answer to make physical sense. 

An examination of the equation v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) can produce further insights into the general relationships among physical quantities: The final velocity depends on the magnitude of the acceleration and the distance over which it applies. For a given acceleration, a car that is going twice as fast does not stop in twice the distance it goes much further before it stops. (This is why, for example, we have reduced speed zones near schools.) 

[OL] Work through the problem-solving steps with the student: What is the goal? What is known and unknown? Which equation expresses the unknown in terms of the knowns? Solve for the unknown. Insert known values. Calculate. Checking that answer is reasonable and has the correct units, sign, and significant figures. 

Repeat for the second sample problem. 

[AL] Initiate a discussion on variation in gravity. Compare gravity on Earth to gravity on the Moon. Explain the difference between g and constants that are the same everywhere in the universe, such as the speed of light. Practice Problems 

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[link] Constant Acceleration 

In many cases, acceleration is not uniform because the force acting on the accelerating object is not constant over time. A situation that gives constant acceleration is the acceleration of falling objects. When air resistance is not a factor, all objects near Earth s surface fall with an acceleration of about 9.80 m/s 2 . Although this value decreases slightly with increasing altitude, it may be assumed to be essentially constant. The value of 9.80 m/s 2 is labeled g and is referred to as acceleration due to gravity . Gravity is the force that causes nonsupported objects to accelerate downward (or, more precisely, toward the center of Earth). The magnitude of this force is called the weight of the object and is given by mg where m is the mass of the object (in kg). In places other than on Earth, such as the moon or on other planets, g is not 9.80 m/s 2 but takes on other values. When using g for the acceleration a in a kinematic equation, it is usually given a negative sign because the acceleration due to gravity is downward. Effects of Rapid Acceleration Astronauts train using G Force Simulators. (credit: NASA) 

When in a vehicle that accelerates rapidly, you experience a force on your entire body that accelerates your body. You feel this force in automobiles and slightly more on amusement park rides. For example, when you ride in a car that turns, the car applies a force on your body to make you accelerate in the direction in which the car is turning. If enough force is applied, you will accelerate at 9.80 m/s 2 . This is the same as the acceleration due to gravity, so this force is called one G. 

One G is the force required to accelerate an object at the acceleration due to gravity at Earth s surface. Thus, one G for a paper cup is much less than one G for an elephant, because the elephant is much more massive and so requires a greater force to make it accelerate at 9.80 m/s 2 . For a person, a G of about 4 is so strong that his or her face will distort as the bones accelerate forward through the loose flesh. Other symptoms at extremely high Gs include changes in vision, loss of consciousness, and even death. The space shuttle produces about 3 Gs during takeoff and reentry. Some roller coasters and dragsters produce forces of around 4 Gs for their occupants. A fighter jet can produce up to 12 Gs during a sharp turn. 

Astronauts and fighter pilots must undergo G-force training in simulators. The video shows the experience of several people undergoing this training. 

People such as astronauts who work with G forces must also be trained to experience zero G also called free fall or weightlessness which can cause queasiness. NASA has an aircraft that allows it occupants to experience about 25 s of free fall. The aircraft is nicknamed the Vomit Comet. 

Mention that, later in this course, students will encounter some interesting concepts related to gravity and acceleration when studying the general theory of relativity. In part, the theory is based on the idea that gravity cannot be distinguished from acceleration, either experientially or mathematically. When in an upward-bound elevator, can you really tell whether you are accelerating or whether gravity has suddenly become stronger? 

[link] Falling Objects 

A person standing on the edge of a high cliff throws a rock straight up with an initial velocity v 0 of 13 m/s. 

(a) Calculate the position and velocity of the rock at 1.00, 2.00, and 3.00 seconds after it is thrown. Ignore the effect of air resistance. Strategy 

Sketch the initial velocity and acceleration vectors and the axes. Initial conditions for rock thrown straight up. 

List the knowns: time t = 1.00 s, 2.00 s, and 3.00 s; initial velocity v 0 = 13 m/s; acceleration a = g = 9.80 m/s 2 ; position y 0 = 0 m. 

List the unknowns: y 1 , y 2 , and y 3 ; v 1 , v 2 , and v 3 (where 1, 2, 3 refer to times 1.00 s, 2.00 s, and 3.00 s). 

Choose the equations: 

d = d 0 + v 0 t + 1 2 a t 2 d = d 0 + v 0 t + 1 2 a t 2 becomes y = y 0 + v 0 t 1 2 g t 2 y = y 0 + v 0 t 1 2 g t 2 

v = v 0 + a t v = v 0 + a t becomes v = v 0 + g t v = v 0 + g t 

These equations describe the unknowns in terms of knowns only. Solution 

y 1 = 0 + ( 13.0 m/s ) ( 1.00 s ) + ( 9.80 m/s 2 ) ( 1.00 s ) 2 2 = 8.10 m y 2 = 0 + ( 13.0 m/s ) ( 2.00 s ) + ( 9.80 m/s 2 ) ( 2.00 s ) 2 2 = 6.40 m y 3 = 0 + ( 13.0 m/s ) ( 3.00 s ) + ( 9.80 m/s 2 ) ( 3.00 s ) 2 2 = 5.10 m v 1 = 13.0 m/s + ( 9.80 m/s 2 ) ( 1.00 s ) = 3.20 m/s v 2 = 13.0 m/s + ( 9.80 m/s 2 ) ( 2.00 s ) = 6.60 m/s v 3 = 13.0 m/s + ( 9.80 m/s 2 ) ( 3.00 s ) = 16.4 m/s y 1 = 0 + ( 13.0 m/s ) ( 1.00 s ) + ( 9.80 m/s 2 ) ( 1.00 s ) 2 2 = 8.10 m y 2 = 0 + ( 13.0 m/s ) ( 2.00 s ) + ( 9.80 m/s 2 ) ( 2.00 s ) 2 2 = 6.40 m y 3 = 0 + ( 13.0 m/s ) ( 3.00 s ) + ( 9.80 m/s 2 ) ( 3.00 s ) 2 2 = 5.10 m v 1 = 13.0 m/s + ( 9.80 m/s 2 ) ( 1.00 s ) = 3.20 m/s v 2 = 13.0 m/s + ( 9.80 m/s 2 ) ( 2.00 s ) = 6.60 m/s v 3 = 13.0 m/s + ( 9.80 m/s 2 ) ( 3.00 s ) = 16.4 m/s Discussion 

The first two positive values for y show that the rock is still above the edge of the cliff, and the third negative y value shows that it has passed the starting point and is below the cliff. Remember that we set up to be positive. Any position with a positive value is above the cliff, and any velocity with a positive value is an upward velocity. The first value for v is positive, so the rock is still on the way up. The second and third values for v are negative, so the rock is on its way down. 

(b) Make graphs of position versus time, velocity versus time, and acceleration versus time. Use increments of 0.5 s in your graphs. Strategy 

Time is customarily plotted on the x axis because it is the independent variable. Position versus time will not be linear, so calculate points for 0.50 s, 1.50 s, and 2.50 s. This will give a curve closer to the true, smooth shape. Solution 

The three graphs are shown in [link] . Discussion y vs. t does not represent the two-dimensional parabolic path of a trajectory. The path of the rock is straight up and straight down. The slope of a line tangent to the curve at any point on the curve equals the velocity at that point (i.e., the instantaneous velocity). Note that the v vs. t line crosses the vertical axis at the initial velocity and crosses the horizontal axis at the time when the rock changes direction and begin to fall back to Earth. This plot is linear because acceleration is constant. The a vs. t plot also shows that acceleration is constant; that is, it does not change with time. 

Prior to solving the problem, have students consider the following questions: What is the goal? What is known and unknown? Which equation expresses the unknown in terms of the knowns? 

After solving the problem, have students check that the answer is reasonable and has the correct units, sign, and significant figures. Practice Problems 

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[link] Check Your Understanding 

Use these questions to assess students achievement of the sections Learning Objectives. If students are struggling with a specific objective, the formative assessment will help identify which objective is the problem so that you can direct students to the relevant content. 

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[link] Section Summary The kinematic equations show how time, displacement, velocity, and acceleration are related for objects in motion. In general, kinematic problems can be solved by identifying the kinematic equation that expresses the unknown in terms of the knowns. Displacement, velocity, and acceleration may be displayed graphically versus time. Key Equations Average velocity d = d 0 + v t d = d 0 + v t , or v = d t v = d t when d 0 = 0. Average velocity v = v 0 + v f 2 v = v 0 + v f 2 Velocity v = v 0 + a t v = v 0 + a t , or when v 0 = 0. Displacement d = d 0 + v 0 t + 1 2 a t 2 d = d 0 + v 0 t + 1 2 a t 2 , or a = 2 d t 2 a = 2 d t 2 when d 0 = 0 and v 0 = 0. Acceleration v 2 = v 0 2 + 2 a ( d d 0 ) v 2 = v 0 2 + 2 a ( d d 0 ) , or a = v 2 2 d a = v 2 2 d when d 0 = 0 and v 0 = 0. Concept Items 

[link] Critical Thinking 

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[link] Performance Task 

Design an experiment to measure displacement and elapsed time. Use the data to calculate final velocity, average velocity, acceleration, and acceleration. Materials a small marble or ball bearing a garden hose a measuring tape a stopwatch or stopwatch software download a sloping driveway or lawn as long as the garden hose with a level area beyond 

(a) How would you use the garden hose, stopwatch, marble, measuring tape, and slope to measure displacement and elapsed time? (Hint: The marble is the accelerating object, and the length of the hose is total displacement.) 

(b) How would you use the displacement and time data to calculate velocity, average velocity, and acceleration? Which kinematic equations would you use? 

(c) How would you use the materials, the measured and calculated data, and the flat area below the slope to determine the negative acceleration? What would you measure, and which kinematic equation would you us? 

This performance task supports NGSS HS-PS2-1: Analyze data to support the claim that Newton s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. 

Performance Task Rubric 

(a) Insert the marble (without a push) into the end of the hose at the top of the slope. With the stopwatch, measure the time, t , from when the marble was introduced at the top until it appears at the bottom. The length of the hose is displacement, x . 

(b) Use Equation 1 to calculate average velocity; use Equation 2 to calculate velocity; and use Equation 3 to calculate acceleration. 

(c) Measure the time from when the marble comes out of the hose until it stops to get t . You will not need x . Use the average v measurement from above for v 0 . The value of v is zero. Use Equation 3 to calculate deceleration. The sign of a will be minus. Test Prep Multiple Choice 

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[link] Glossary acceleration due to gravity acceleration of an object that is subject only to the force of gravity. Near Earth s surface this acceleration is 9.80 m/s 2 constant acceleration acceleration that does not change with respect to time kinematic equations the five equations that describe motion in terms of time, displacement, velocity, and accelerationIntroduction Introduction Force Newton s First Law of Motion: Inertia Newton s Second Law of Motion Newton s Third Law of Motion class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" 

Before students begin this chapter, they may wish to review the concepts of distance, displacement, speed, velocity, acceleration, scalars, vectors, representing vectors, units of acceleration, and acceleration due to gravity. Explain that an object that is not moving is often described in physics as being at rest. Newton s laws of motion describe the motion of the dolphin s path. (credit: Jin Jang) 

Point out that we come across motion in our everyday lives; for instance, a dolphin jumping out of water as shown in the photo. There are simple laws of physics that govern motion. These laws are universal; that is, they apply to every object in the universe. Much of the work done in describing motion was done by Sir Isaac Newton. This chapter is about motion, the causes of motion, and the universal laws of motion. 

Isaac Newton (1642 1727) was a natural philosopher; a great thinker who combined science and philosophy to try to explain the workings of nature on Earth and in the universe. His laws of motion were just one part of the monumental work that has made him legendary. The development of Newton s laws marks the transition from the Renaissance period of history to the modern era. This transition was characterized by a revolutionary change in the way people thought about the physical universe. Drawing upon earlier work by scientists Galileo Galilei and Johannes Kepler , Newton s laws of motion allowed motion on Earth and in space to be predicted mathematically. In this chapter you will learn about force as well as Newton s first, second, and third laws of motion.Force Force Section Learning Objectives 

By the end of this section, you will be able to: Differentiate between force, net force, and dynamics Draw a free-body diagram 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4C) : analyze and describe accelerated motion in two dimensions using equations, including projectile and circular examples (4E) : develop and interpret free-body diagrams 

[BL] [OL] Point out that objects at rest tend to stay at rest. A ball, for example, moves only when pushed or pulled. The action of pushing or pulling is the application of force. Force applied to an object changes its motion. 

[AL] Start a discussion about force and motion. Ask students what would happen if more than one force is applied to an object. Take a heavy object such as a desk for demonstration. Ask one student to push it from one side. Explain how force and motion work. Now ask a second student to push it in the opposite direction. Ask students why no motion occurs even though the first student applies the same amount of force. Introduce the concept of adding forces. Section Key Terms dynamics external force force free-body diagram net external force net force Defining Force and Dynamics 

[OL] Explain that the word dynamics comes from a Greek word meaning power. Also point out that the word dynamics is singular, like the word physics. 

[BL] [OL] You may want to introduce the terms system, external force, and internal force. 

[AL] Explain that both magnitude and direction must be considered when talking about forces. 

Demonstrate by using physical objects how different forces acting together can add if they act in the same direction or cancel if they act in opposite directions. Explain the terms acting on and being acted on. 

Force is the cause of motion, and motion draws our attention. Motion itself can be beautiful, such as a dolphin jumping out of the water, the flight of a bird, or the orbit of a satellite. The study of motion is called kinematics , but kinematics describes only the way objects move their velocity and their acceleration . Dynamics considers the forces that affect the motion of moving objects and systems . Newton s laws of motion are the foundation of dynamics. These laws describe the way objects speed up, slow down, stay in motion, and interact with other objects. They are also universal laws : they apply everywhere on Earth as well as in space. 

A force pushes or pulls an object. The object being moved by a force could be an inanimate object, such as a table, or an animate object, such as a person. The pushing or pulling may be done by a person, or even the gravitational pull of Earth. Forces have different magnitudes and directions; this means that some forces are stronger than others and can act in different directions. For example, a cannon exerts a strong force on the cannonball that is launched into the air. In contrast, a mosquito landing on your arm exerts only a small force on your arm. 

When multiple forces act on an object, the forces combine. Adding together all of the forces acting on an object gives the total force, or net force . An external force is a force that acts on an object within the system from outside the system. This type of force is different than an internal force, which acts between two objects that are both within the system. The net external force combines these two definitions; it is the total combined external force. We discuss further details about net force, external force, and net external force in the coming sections. 

In mathematical terms, two forces acting in opposite directions have opposite signs (positive or negative). By convention, the negative sign is assigned to movement to the left or downward. If two forces pushing in opposite directions are added together, the larger force will be somewhat canceled out by the smaller force pushing in the opposite direction. It is important to be consistent with your chosen coordinate system within a problem; for example, if negative values are assigned to the downward direction for velocity, then distance, force and acceleration should also be designated as negative in the downward direction. Free-body Diagrams and Examples of Forces 

[BL] Review vectors and how they are represented. Review vector addition. 

[AL] Ask students to give everyday examples of situations where multiple forces act together. Draw free-body diagrams for some of these situations. 

For our first example of force, consider an object hanging from a rope. This example gives us the opportunity to introduce a useful tool known as a free-body diagram . A free-body diagram represents the object being acted upon (that is, the free body) as a single point. Only the forces acting on the body (that is, external forces) are shown and are represented by vectors (which are drawn as arrows). These forces are the only ones shown because only external forces acting on the body affect its motion. We can ignore any internal forces within the body because they cancel each other out, as explained in the section on Newton's third law of motion. Free-body diagrams are very useful for analyzing forces acting on an object. An object of mass, m , is held up by the force of tension. 

[link] shows the force of tension in the rope acting in the upward direction, opposite the force of gravity. The forces are indicated in the free-body diagram by an arrow pointing up, representing tension, and another arrow pointing down, representing gravity. In a free-body diagram, the lengths of the arrows show the relative magnitude (or strength) of the forces. Because forces are vectors, they add just like other vectors. Notice that the two arrows have equal lengths in [link] which means that the forces of tension and weight are of equal magnitude. Because these forces of equal magnitude act in opposite directions, they are perfectly balanced, so they add together to give a net force of zero. 

Not all forces are as noticeable as when you push or pull on an object. Some forces act without physical contact, such as the pull of a magnet (in the case of magnetic force) or the gravitational pull of Earth (in the case of gravitational force). 

In the next three sections discussing Newton s laws of motion, we will learn about three specific types of forces: friction, the normal force , and the gravitational force . To analyze situations involving forces, we will create free-body diagrams to organize the framework of the mathematics for each individual situation. 

Correctly drawing and labeling a free-body diagram is an important first step for solving a problem. It will help you visualize the problem and correctly apply the mathematics to solve the problem. Section Summary Dynamics is the study of how forces affect the motion of objects and systems. Force is a push or pull that can be defined in terms of various standards. It is a vector and so has both magnitude and direction. External forces are any forces outside of a body that act on the body. A free-body diagram is a drawing of all external forces acting on a body. Check Your Understanding 

Use the questions in Check Your Understanding to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment through Check Your Understanding will help identify which objective is causing the problem and direct students to the relevant content. 

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[link] Glossary dynamics the study of how forces affect the motion of objects and systems external force a force acting on an object or system that originates outside of the object or system force a push or pull on an object with a specific magnitude and direction; can be represented by vectors; can be expressed as a multiple of a standard force free-body diagram a diagram showing all external forces acting on a body net external force the sum of all external forces acting on an object or system net force the sum of all forces acting on an object or systemNewton s First Law of Motion: Inertia Newton s First Law of Motion: Inertia Section Learning Objectives 

By the end of this section, you will be able to: Describe Newton s first law and friction Discuss the relationship between mass and inertia 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4D) : calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects 

Before students begin this section, it is useful to review the concepts of force, external force, net external force, and addition of forces. 

[BL] [OL] [AL] Ask students to speculate what happens to objects when they are set in motion. Do they remain in motion or stop after some time? Why? 

Students may believe that objects that are in motion tend to slow down and stop. Explain the concept of friction. Talk about objects in outer space, where there is no atmosphere and no gravity. Ask students to describe the motion of such objects. Section Key Terms friction inertia law of inertia mass Newton s first law of motion system Newton s First Law and Friction 

[BL] [OL] [AL] Discuss examples of Newton s First Law seen in everyday life. 

[BL] [OL] [AL] Talk about different pairs of surfaces and how each exhibits different levels of friction. Ask students to give examples of smooth and rough surfaces. Ask them where friction may be useful and where it may be undesirable. 

[OL] [AL] Ask students to give different examples of systems where multiple forces occur. Draw free-body diagrams for these. Include the force of friction. Emphasize the direction of the force of friction. 

Newton s first law of motion states that: A body at rest tends to remain at rest. A body in motion tends to remain in motion at constant velocity unless acted on by a net external force. (Recall that constant velocity means the body moves in a straight line and at a constant speed.) 

At first glance, this law may seem to contradict your everyday experience. You have probably noticed that a moving object will usually slow down and stop unless some effort is made to keep it moving. The key to understanding why, for example, a sliding box slows down (seemingly on its own) is to first understand that a net external force acts on the box to make the box slow down. Without this net external force, the box would continue to slide at a constant velocity (as stated in Newton s first law of motion). What force acts on the box to slow it down? It is called friction . Friction is an external force that acts opposite to the direction of motion (see [link] ). Think of it as a resistance to motion that slows things down. 

Consider an air hockey table. When the air is turned off, the puck slides only a short distance before friction slows it to a stop. However, when the air is turned on, it lifts the puck slightly, so that the puck experiences very little friction as it moves over the surface. With friction almost eliminated, the puck glides along with very little change in speed. On a frictionless surface, the puck would experience no net external force (ignoring air resistance, which is also a form of friction). Additionally, if we know enough about friction, we can accurately predict how quickly objects will slow down. 

Now let s think about another example. A man pushes a box across a floor at constant velocity by applying a force of +50 N. (The positive sign indicates that, by convention, the direction of motion is to the right.) What is the force of friction that opposes the motion? The force of friction must be 50 N. Why? According to Newton s first law of motion, any object moving at constant velocity has no net external force acting upon it, which means that the sum of the forces acting on the object must be zero. The mathematical way to say that no net external force acts on an object is F net = 0 F net = 0 or F = 0 F = 0 . So if the man applies +50 N of force, then the force of friction must be 50 N for the two forces to add up to zero (that is, for the two forces to cancel each other). Whenever you encounter the phrase at constant velocity, Newton s first law tells you that the net external force is zero. For a box sliding across a floor, friction acts in the direction opposite to the velocity. 

The force of friction depends on two factors: the coefficient of friction and the normal force . For any two surfaces that are in contact with one another, the coefficient of friction is a constant that depends on the nature of the surfaces. The normal force is the force exerted by a surface that pushes on an object in response to gravity pulling the object down. In equation form, the force of friction is f = N f = N 

where is the coefficient of friction and N is the normal force. (The coefficient of friction is discussed in more detail in another chapter, and the normal force is discussed in more detail in the section named Newton's Third Law of Motion, in this chapter.) 

Recall from the section on Force that a net external force acts from outside on the object of interest. A more precise definition is that it acts on the system of interest. A system is one or more objects that you choose to study. It is important to define the system at the beginning of a problem to figure out which forces are external and need to be considered and which are internal and can be ignored. 

For example, in [link] part (a), two children push a third child in a wagon at constant velocity. The system of interest is the wagon plus the small child, as shown in part (b) of the figure. The two children behind the wagon exert external forces on this system ( F 1, F 2). Friction f acting at the axles of the wheels and at the surface where the wheels touch the ground is another external force acting on the system. Two more external forces act on the system: the weight W of the system pulling down and the normal force N of the ground pushing up. Notice that the wagon is not accelerating vertically, so Newton s first law tells us that the normal force balances the weight. Because the wagon is moving forward at constant velocity, the force of friction must have the same strength as the sum of the forces applied by the two children. (a) The wagon and rider form a system that is acted on by external forces. (b)The two children pushing the wagon and child provide two external forces. Friction acting at the wheel axles and on the surface of the tires where they touch the ground provides an external force that acts against the direction of motion. The weight W and the normal force N from the ground are two more external forces acting on the system. All external forces are represented in the figure by arrows. All of the external forces acting on the system add together, but because the wagon moves at a constant velocity, all the forces must add up to zero. Mass and Inertia 

[BL] Review Newton s first law. Explain that the property of objects to maintain their state of motion is called inertia. 

[OL] [AL] Take two similar carts or trolleys with wheels. Place a heavy weight in one of them. Ask students which cart would require more force to change its state of motion. Ask students which would stay in motion longer if you were to set them in motion. Based on this discussion, have students speculate what inertia may depend on. 

[BL] [OL] Explain the concepts of mass and weight. Explain that these terms may be used interchangeably in everyday life but have different meanings in science. 

Inertia is the tendency for an object at rest to remain at rest, or for a moving object to remain in motion in a straight line with constant speed. This key property of objects was first described by Galileo. Later, Newton incorporated the concept of inertia into his first law, which is often referred to as the law of inertia . 

As we know from experience, some objects have more inertia than others. For example, changing the motion of a large truck is more difficult than changing the motion of a toy truck. In fact, the inertia of an object is proportional to the mass of the object. Mass is a measure of the amount of matter (or stuff ) in an object. The quantity or amount of matter in an object is determined by the number and types of atoms the object contains. Unlike weight (which changes if the gravitational force changes), mass does not depend on gravity. The mass of an object is the same on Earth, in orbit, or on the surface of the moon. In practice, it is very difficult to count and identify all of the atoms and molecules in an object, so mass is usually not determined this way. Instead, the mass of an object is determined by comparing it with the standard kilogram. Mass is therefore expressed in kilograms. 

In everyday language, people often use the terms weight and mass interchangeably but this is not correct. Weight is actually a force. (We cover this topic in more detail in section on Newton's Second Law of Motion.) Newton s First Law of Motion 

This video contrasts the way we thought about motion and force in the time before Galileo s concept of inertia and Newton s first law of motion with the way we understand force and motion now. 

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In this simulation, you will first explore net force by placing blue people on the left side of a tug of war rope and red people on the right side of the rope (by clicking people and dragging them with your mouse). Experiment with changing the number and size of people on each side to see how it affects the outcome of the match and the net force. Hit the Go! button to start the match, and the reset all button to start over. 

Next, click on the Friction tab. Try selecting different objects for the person to push. Slide the applied force button to the right to apply force to the right and to the left to apply force to the left. The force will continue to be applied as long as you hold down the button. See the arrow representing friction change in magnitude and direction, depending on how much force you apply. Try increasing or decreasing the friction force to see how this change affects the motion. Click here for the simulation 

[link] Section Summary Newton s first law states that a body at rest remains at rest or, if moving, remains in motion in a straight line at a constant speed unless acted on by a net external force. This law is also known as the law of inertia. Inertia is the tendency of an object at rest to remain at rest or, if moving, to remain in motion at constant velocity. Inertia is related to an object s mass. Friction is a force that opposes motion and causes an object or system to slow down. Mass is the quantity of matter in a substance. Key Equations Newton's first law of motion F net = 0 F net = 0 or F = 0 F = 0 

Use the questions in Check Your Understanding to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment through Check Your Understanding will help identify which objective is causing the problem and direct students to the relevant content. Check Your Understanding 

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[link] Glossary friction an external force that acts in the direction opposite to the direction of motion inertia the tendency of an object at rest to remain at rest, or for a moving object to remain in motion in a straight line and at constant speed law of inertia Newton s first law of motion: a body at rest remains at rest or, if in motion, remains in motion at a constant speed in a straight line unless acted on by a net external force; also known as the law of inertia mass the quantity of matter in a substance; measured in kilograms Newton s first law of motion a body at rest remains at rest or, if in motion, remains in motion at a constant speed in a straight line unless acted on by a net external force; also known as the law of inertia system one or more objects of interest for which only the forces acting on them from the outside are considered, but not the forces acting between them or inside of themNewton s Second Law of Motion Newton s Second Law of Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe Newton s second law both verbally and mathematically Use Newton s second law to solve problems 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4D) : calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects 

Before beginning this section, review forces, acceleration, acceleration due to gravity (g), friction, inertia, and Newton s First Law. Section Key Terms freefall Newton s second law of motion weight Describing Newton s Second Law of Motion 

[BL] [OL] Review the concepts of inertia and Newton s first law. Explain that, according to Newton s First Law, a change in motion is caused by an external force. For instance, a ball that is pitched changes its speed and direction when it is hit by a bat. 

[BL] [OL] [AL] Write the equation for Newton s Second Law and show how it can be solved for all three variables, F , m , and a . Explain the practical implications for each case. Ask students how the other two variables would behave if one quantity is held constant. 

Students might confuse the terms equal and proportional. 

Newton s first law considered bodies at rest or bodies in motion at constant velocity . The other state of motion to consider is when an object is moving with a changing velocity, which means a change in the speed and/or the direction of motion. This type of motion is addressed by Newton s second law of motion , which states how force causes changes in motion. Newton s second law of motion is used to calculate what happens in situations involving forces and motion, and it shows the mathematical relationship between force, mass , and acceleration . Mathematically, the second law is most often written as F net = m a or F = m a F net = m a or F = m a 

where F net (or F ) is the net external force , m is the mass of the system, and a is the acceleration. Note that F net and F are the same because the net external force is the sum of all of the external forces acting on the system. 

First, what do we mean by a change in motion ? A change in motion is simply a change in velocity: the speed of an object can become slower or faster, the direction in which the object is moving can change, or both of these variables may change. A change in velocity means, by definition, that an acceleration has occurred. Newton s first law says that only a nonzero net external force can cause a change in motion, so a net external force must cause an acceleration. Note that acceleration can refer to slowing down or to speeding up. Acceleration can also refer to a change in the direction of motion with no change in speed, because acceleration is the change in velocity divided by the time it takes for that change to occur, and velocity is defined by speed and direction. 

From the equation F net = m a , F net = m a , we see that force is directly proportional to both mass and acceleration, which makes sense. To accelerate two objects from rest to the same velocity, you would expect more force to be required to accelerate the more massive object. Likewise, for two objects of the same mass, applying a greater force to one would accelerate it to a greater velocity. 

Now, let s rearrange Newton s second law to solve for acceleration. We get a = F net m or a = F m . a = F net m or a = F m . 

In this form, we can clearly see that acceleration is directly proportional to force, which we write as a F net , a F net , 

where the symbol means proportional to. 

This proportionality states mathematically what we just said in words acceleration is directly proportional to the net external force. When two variables are directly proportional to each other, then if one variable doubles, the other variable must double. Likewise, if one variable is reduced by half, the other variable must also be reduced by half. In general, when one variable is multiplied by a number, the other variable will also be multiplied by the same number. It seems reasonable that the acceleration of a system should be directly proportional to and in the same direction as the net external force acting on the system. An object experiences greater acceleration when acted on by a greater force. 

It is also clear from the equation a = F net / m a = F net / m that acceleration is inversely proportional to mass, which we write as a 1 m . a 1 m . 

Inversely proportional means that, if one variable is multiplied by a number, the other variable must be divided by the same number. Now, it also seems reasonable that acceleration should be inversely proportional to the mass of the system. In other words, the larger the mass (the inertia), the smaller the acceleration produced by a given force. This relationship is illustrated in [link] , which shows that a given net external force applied to a basketball produces a much greater acceleration than when applied to a car. The same force exerted on systems of different mass produces different accelerations. (a) A boy pushes a basketball to make a pass. The effect of gravity on the ball is ignored. (b) The same boy pushing with identical force on a stalled car produces a far smaller acceleration (friction is negligible). Note that the free-body diagrams for the ball and for the car are identical, which allows us to compare the two situations. Applying Newton s Second Law 

[BL] Review how to convert between units. 

[OL] [AL] Ask students to give examples of Newton s Second Law. 

Students might confuse weight, which is a force, and g , which is the acceleration due to gravity. 

[BL] [OL] [AL] Ask students if they think an astronaut weighs the same on the moon as they do on Earth. Talk about the difference between mass and weight. 

Before putting Newton s second law into action, it is important to consider units. The equation F net = m a F net = m a is used to define the units of force in terms of the three basic units of mass, length, and time (recall that acceleration has units of length divided by time squared). The SI unit of force is called the newton (abbreviated N) and is the force needed to accelerate a 1 kg system at the rate of 1 m/s2. That is, because F net = m a , F net = m a , we have 1 N = 1 kg 1 m/s 2 = 1 kg m s 2 1 N = 1 kg 1 m/s 2 = 1 kg m s 2 

One of the most important applications of Newton s second law is to calculate weight (also known as the gravitational force ), which is usually represented mathematically as W . When people talk about gravity , they don t always realize that it is an acceleration. When an object is dropped, it accelerates toward the center of Earth. Newton s second law states that the net external force acting on an object is responsible for the acceleration of the object. If air resistance is negligible, the net external force on a falling object is only the gravitational force (i.e., the weight of the object). 

Weight can be represented by a vector because it has a direction. Down is defined as the direction in which gravity pulls, so weight is normally considered a downward force. By using Newton s second law, we can figure out the equation for weight. 

Consider an object with mass m falling toward Earth. It experiences only the force of gravity (i.e. the gravitational force or weight), which is represented by W . Newton s second law states that F net = m a . F net = m a . Since the only force acting on the object is the gravitational force, we have F net = W . F net = W . We know that the acceleration of an object due to gravity is g , so we have a = g . a = g . Substituting these two expressions into Newton s second law gives W = m g W = m g 

This is the equation for weight the gravitational force on a mass m . On Earth, g = 9.80 m/s 2 , g = 9.80 m/s 2 , so the weight (disregarding for now the direction of the weight) of a 1.0 kg object on Earth is W = m g = (1 .0 kg)(9 .80 m/s 2 ) = 9.8 N W = m g = (1 .0 kg)(9 .80 m/s 2 ) = 9.8 N 

Although most of the world uses newtons as the unit of force, in the United States the most familiar unit of force is the pound (lb), where 1 N = 0.225 lb. 

Recall that, although gravity acts downward, it can be assigned a positive or negative value, depending on the positive direction in your chosen coordinate system. Be sure to take this into consideration when solving problems with weight. When the downward direction is taken to be negative, as is often the case, acceleration due to gravity becomes g = 9.8 m/s 2 . 

When the net external force on an object is its weight, we say that it is in freefall . In this case, the only force acting on the object is the force of gravity. On the surface of Earth, when objects fall downward toward Earth, they are never truly in freefall because there is always some upward force due to the air resistance that acts on the object (and there is also the buoyancy force of air, which is similar to the buoyancy force in water that keeps boats afloat). 

Gravity varies slightly over the surface of Earth, so that the weight of an object depends very slightly on its location on Earth. Weight varies dramatically away from Earth s surface. On the Moon, for example, the acceleration due to gravity is only 1.67 m/s 2 . Because weight depends on the force of gravity, a 1.0 kg mass weighs 9.8 N on Earth and only about 1.7 N on the Moon. 

It is important to remember that weight and mass are very different, although they are closely related. Mass is the quantity of matter (how much stuff ) in an object and does not vary, but weight is the gravitational force on an object and is proportional to the force of gravity. It is easy to confuse the two, because our experience is confined to Earth, and the weight of an object is essentially the same no matter where you are on Earth. Adding to the confusion, the terms mass and weight are often used interchangeably in everyday language; for example, our medical records often show our weight in kilograms, but never in the correct units of newtons. Mass and Weight 

Explain that, even though a scale gives a mass, it actually measures weight. Scales are calibrated to show the correct mass on Earth. They would give different results on the Moon, because the force of gravity is weaker on the Moon. 

In this activity you will use a scale to investigate mass and weight. 1 bathroom scale 1 table What do bathroom scales measure? When you stand on a bathroom scale, what happens to the scale? It depresses slightly. The scale contains springs that compress in proportion to your weight similar to rubber bands expanding when pulled. The springs provide a measure of your weight (provided you are not accelerating). This is a force in newtons (or pounds). In most countries, the measurement is now divided by 9.80 to give a reading in kilograms, which are units of mass. The scale detects weight but is calibrated to display mass. If you went to the Moon and stood on your scale, would it detect the same mass as it did on Earth? 

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Only net external force impacts the acceleration of an object. If more than one force acts on an object and you calculate the acceleration by using only one of these forces, you will not get the correct acceleration for the object. Newton s Second Law of Motion 

This video reviews Newton s second law of motion and how net external force and acceleration relate to one another and to mass. It also covers units of force, mass, and acceleration and goes over a worked example. 

[link] What Acceleration Can a Person Produce when Pushing a Lawn Mower? 

Suppose that the net external force (push minus friction) exerted on a lawn mower is 51 N parallel to the ground. The mass of the mower is 240 kg. What is its acceleration? Strategy 

Since F net and m are given, the acceleration can be calculated directly from Newton s second law: F net = m a . Solution 

Solving Newton s second law for the acceleration, we find that the magnitude of the acceleration, a , is a = F net m . a = F net m . Entering the given values for net external force and mass gives 

a = 51 N 240 kg a = 51 N 240 kg 

Inserting the units kg m/s 2 kg m/s 2 for N yields 

a = 51 kg m/s 2 240 kg = 0.21 m/s 2 a = 51 kg m/s 2 240 kg = 0.21 m/s 2 Discussion 

The acceleration is in the same direction as the net external force, which is parallel to the ground and to the right. There is no information given in this example about the individual external forces acting on the system, but we can say something about their relative magnitudes. For example, the force exerted by the person pushing the mower must be greater than the friction opposing the motion because we are given that the net external force is in the direction in which the person pushes. Also, the vertical forces must cancel if there is no acceleration in the vertical direction (the mower is moving only horizontally). The acceleration found is reasonable for a person pushing a mower; the mower s speed must increase by 0.21 m/s every second, which is possible. The time during which mower accelerates would not be very long because the person s top speed would soon be reached. At this point, the person could push a little less hard, because he only has to overcome friction. What Rocket Thrust Accelerates This Sled? 

Prior to manned space flights, rocket sleds were used to test aircraft, missile equipment, and physiological effects on humans at high accelerations. Rocket sleds consisted of a platform mounted on one or two rails and propelled by several rockets. Calculate the magnitude of force exerted by each rocket, called its thrust T , for the four-rocket propulsion system shown below. The sled s initial acceleration is 49 m/s 2 , 49 m/s 2 , the mass of the system is 2100 kg, and the force of friction opposing the motion is 650 N. Strategy 

The system of interest is the rocket sled. Although forces act vertically on the system, they must cancel because the system does not accelerate vertically. This leaves us with only horizontal forces to consider. We ll assign the direction to the right as the positive direction. See the free-body diagram in the figure. Solution 

We start with Newton s second law and look for ways to find the thrust T of the engines. Because all forces and acceleration are along a line, we need only consider the magnitudes of these quantities in the calculations. We begin with 

F net = m a , F net = m a , 

where F net F net is the net external force in the horizontal direction. We can see from the image above that the engine thrusts are in the same direction (which we call the positive direction), whereas friction opposes the thrust. In equation form, the net external force is 

F net = 4 T f . F net = 4 T f . 

Newton s second law tells us that F net = m a , so we get 

m a = 4 T f . m a = 4 T f . 

After a little algebra, we solve for the total thrust 4 T : 

4 T = m a + f , 4 T = m a + f , 

which means that the individual thrust is 

T = m a + f 4 . T = m a + f 4 . 

Inserting the known values yields 

T = ( 2100 kg)(49 m/s 2 ) + 650 N 4 = 2.6 10 4 N . T = ( 2100 kg)(49 m/s 2 ) + 650 N 4 = 2.6 10 4 N . Discussion 

The numbers are quite large, so the result might surprise you. Experiments such as this were performed in the early 1960s to test the limits of human endurance and to test the apparatus designed to protect fighter pilots in emergency ejections. Speeds of 1000 km/h were obtained, with accelerations of 45 g . (Recall that g, the acceleration due to gravity, is 9 .80 m/s 2 . 9 .80 m/s 2 . An acceleration 45 g is 45 9 .80 m/s 2 , 45 9 .80 m/s 2 , which is approximately 440 m/s 2 . 440 m/s 2 . ) Living subjects are no longer used, and land speeds of 10,000 km/h have now been obtained with rocket sleds. In this example, as in the preceding example, the system of interest is clear. We will see in later examples that choosing the system of interest is crucial and that the choice is not always obvious. Practice Problems 

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[link] Section Summary Acceleration is a change in velocity, meaning a change in speed, direction, or both. An external force acts on a system from outside the system, as opposed to internal forces, which act between components within the system. Newton s second law of motion states that the acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system, and inversely proportional to the system s mass. In equation form, Newton s second law of motion is F net = m a F net = m a or F = m a F = m a This is sometimes written as a = F net m a = F net m or a = F m a = F m . The weight of an object of mass m is the force of gravity that acts on it. From Newton s second law, weight is given by W = m g W = m g If the only force acting on an object is its weight, then the object is in freefall. Key Equations Newton s second law of motion: F net = m a F net = m a or F = m a F = m a Newton s second law of motion to solve acceleration a = F net m or a = F m a = F net m or a = F m Newton s second law of motion to solve weight W = m g W = m g Check Your Understanding 

Use the questions in Check Your Understanding to assess whether students achieve the section learning objectives. If students are struggling with a specific objective, the assessment through Check Your Understanding will help identify which is causing the problem and direct students to the relevant content. 

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[link] Glossary freefall a situation in which the only force acting on an object is the force of gravity Newton s second law of motion the net external force F net F net on an object is proportional to and in the same direction as the acceleration of the object, a , and also proportional to the object s mass m ; defined mathematically as F net = m a F net = m a or F = m a . F = m a . weight the force of gravity, W , acting on an object of mass m ; defined mathematically as W = m g , where g is the magnitude and direction of the acceleration due to gravityNewton s Third Law of Motion Newton s Third Law of Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe Newton s Third Law both verbally and mathematically Use Newton s Third Law to solve problems 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4D) : calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects Section Key Terms Newton s third law of motion normal force tension thrust Describing Newton s Third Law of Motion 

[BL] [OL] Review Newton s First and Second Laws. 

[AL] Start a discussion about action and reaction by giving examples. Introduce the concepts of systems and systems of interest. Explain how forces can be classified as internal or external to the system of interest. Give examples of systems. Ask students which forces are internal and which are external in each scenario. 

If you have ever stubbed your toe, you have noticed that although your toe initiates the impact, the surface that you stub it on exerts a force back on your toe. Although the first thought that crosses your mind is probably ouch, that hurt rather than this is a great example of Newton s third law, both statements are true. 

This is exactly what happens whenever one object exerts a force on another each object experiences a force that is the same strength as the force acting on the other object but that acts in the opposite direction. Everyday experiences, such as stubbing a toe or throwing a ball, are all perfect examples of Newton s third law in action. 

Newton s third law of motion states that, whenever a first object exerts a force on a second object, the first object experiences a force equal in magnitude but opposite in direction to the force that it exerts. 

Newton s third law of motion tells us that forces always occur in pairs, and one object cannot exert a force on another without experiencing the same strength force in return. We sometimes refer to these force pairs as action-reaction pairs, where the force exerted is the action, and the force experienced in return is the reaction (although which is which depends on your point of view). 

Newton s third law is useful for figuring out which forces are external to a system. Recall that identifying external forces is important when setting up a problem, because the external forces must be added together to find the net force . 

We can see Newton s third law at work by looking at how people move about. Consider a swimmer pushing off from the side of a pool, as illustrated in [link] . She pushes against the pool wall with her feet and accelerates in the direction opposite to her push. The wall has thus exerted on the swimmer a force of equal magnitude but in the direction opposite that of her push. You might think that two forces of equal magnitude but that act in opposite directions would cancel, but they do not because they act on different systems. 

In this case, there are two different systems that we could choose to investigate: the swimmer or the wall. If we choose the swimmer to be the system of interest, as in the figure, then F wall on feet F wall on feet is an external force on the swimmer and affects her motion. Since acceleration is in the same direction as the net external force , the swimmer moves in the direction of F wall on feet . F wall on feet . Since the swimmer is our system (or object of interest) and not the wall, we do not need to consider the force F feet on wall F feet on wall because it originates from the swimmer rather than acting on the swimmer. Therefore, F feet on wall F feet on wall does not directly affect the motion of the system and does not cancel F wall on feet . F wall on feet . Note that the swimmer pushes in the direction opposite to the direction in which she wants to move. When the swimmer exerts a force F feet on wall F feet on wall on the wall, she accelerates in the direction opposite to that of her push. This means that the net external force on her is in the direction opposite to F feet on wall . F feet on wall . This opposition is the result of Newton s third law of motion, which dictates that the wall exerts a force F wall on feet F wall on feet on the swimmer that is equal in magnitude but that acts in the direction opposite to the force that the swimmer exerts on the wall. 

Other examples of Newton s third law are easy to find. As a teacher paces in front of a blackboard, he exerts a force backward on the floor. The floor exerts a reaction force in the forward direction on the teacher that causes him to accelerate forward. Similarly, a car accelerates because the ground pushes forward on the drive wheels in reaction to the drive wheels pushing backward on the ground. You can see evidence of the wheels pushing backward when tires spin on a gravel road and throw rocks backward. 

Another example is the force of a baseball as it makes contact with the bat. Helicopters create lift by pushing air down, creating an upward reaction force. Birds fly by exerting force on air in the direction opposite that in which they wish to fly. For example, the wings of a bird force air downward and backward in order to get lift and move forward. An octopus propels itself forward in the water by ejecting water backward through a funnel in its body, which is similar to how a jet ski is propelled. In these examples, the octopus or jet ski push the water backward, and the water in turn pushes the octopus or jet ski forward. Applying Newton s Third Law 

[BL] Review the concept of weight as a force. 

[OL] Ask students what happens when an object is dropped from a height. Why does it stop when it hits the ground? Introduce the term normal force. 

[BL] [OL] [AL] Demonstrate the concept of tension by using physical objects. Suspend an object such as an eraser from a peg by using a rubber band. Hang another rubber band beside the first but with no object attached. Ask students what the difference is between the two. What are the forces on the first peg? Explain how the rubber band (i.e., the connector) transmits force. Now ask students the direction of the external forces acting on the connector. Also ask what internal forces are acting on the connector. If you remove the eraser, in which direction will the rubber band move? This is the direction of the force the rubber band applied to the eraser. 

Forces are classified and given names based on their source, how they are transmitted, or their effects. In previous sections, we discussed the forces called push, weight, and friction. In this section, applying Newton s third law of motion will allows us to explore three more forces: the normal force , tension , and thrust . However, because we haven t yet covered vectors in depth, we ll only consider one-dimensional situations in this chapter. Another chapter will consider forces acting in two dimensions. 

The gravitational force (or weight ) acts on objects at all times and everywhere on Earth. We know from Newton s second law that a net force produces an acceleration; so why is everything not in a constant state of freefall toward the center of Earth? The answer is the normal force. The normal force is the force that a surface applies to an object to support the weight of that object; it acts perpendicular to the surface upon which the object rests. If an object on a flat surface is not accelerating, the net external force is zero, and the normal force has the same magnitude as the weight of the system but acts in the opposite direction. In equation form, we write that N = m g . N = m g . 

Note that this equation is only true for a horizontal surface. 

The word tension comes from the Latin word meaning to stretch. Tension is the force along the length of a flexible connector, such as a string, rope, chain, or cable. Regardless of the type of connector attached to the object of interest, one must remember that the connector can only pull (or exert tension ) in the direction parallel to its length. Tension is a pull that acts parallel to the connector, and that acts in opposite directions at the two ends of the connector. This is possible because a flexible connector is simply a long series of action-reaction forces, except at the two ends where outside objects provide one member of the action-reaction forces. 

Consider a person holding a mass on a rope as shown in [link] . When a perfectly flexible connector (one requiring no force to bend it) such as an ideal rope transmits a force T , this force must be parallel to the length of the rope, as shown. The pull that such a flexible connector exerts is a tension. Note that the rope pulls with equal magnitude force but in opposite directions on the hand and on the mass (neglecting the weight of the rope). This is an example of Newton s third law. The rope is the medium that transmits between the two objects forces of equal magnitude but that act in opposite directions. 

Tension in the rope must equal the weight of the supported mass, as we can prove by using Newton s second law. If the 5.00 kg mass in the figure is stationary, then its acceleration is zero, so F net = 0. F net = 0. The only external forces acting on the mass are its weight W and the tension T supplied by the rope. Summing the external forces to find the net force, we obtain F net = T W = 0 , F net = T W = 0 , 

where T and W are the magnitudes of the tension and weight and their signs indicate direction, with up being positive. By substituting m g for F net and rearranging the equation, the tension equals the weight of the supported mass, just as you would expect: T = W = m g . T = W = m g . 

For a 5.00 kg mass (neglecting the mass of the rope), we see that T = m g = ( 5.00 kg)(9 .80 m/s 2 ) = 49.0 N . T = m g = ( 5.00 kg)(9 .80 m/s 2 ) = 49.0 N . 

Another example of Newton s third law in action is thrust. Rockets move forward by expelling gas backward at high velocity. This means that the rocket exerts a large force backward on the gas in the rocket combustion chamber, and the gas in turn exerts a large force forward on the rocket in response. This reaction force is called thrust. 

A common misconception is that rockets propel themselves by pushing on the ground or on the air behind them. They actually work better in a vacuum, where they can expel exhaust gases more easily. Math: Problem-Solving Strategy for Newton s Laws of Motion 

The basics of problem solving, presented earlier in this text, are followed here with specific strategies for applying Newton s laws of motion. These techniques also reinforce concepts that are useful in many other areas of physics. 

First, identify the physical principles involved. If the problem involves forces, then Newton s laws of motion are involved, and it is important to draw a careful sketch of the situation. Such a sketch is shown in [link] . Next, as in [link] , use vectors to represent all forces. Label the forces carefully and make sure that their lengths are proportional to the magnitude of the forces and that the arrows point in the direction in which the forces act. (a) A sketch of Tarzan hanging motionless from a vine. (b) Arrows are used to represent all forces. T is the tension exerted on Tarzan by the vine, F T F T is the force exerted on the vine by Tarzan, and W is Tarzan s weight (i.e., the force exerted on Tarzan by Earth s gravity ). All other forces, such as a nudge of a breeze, are assumed to be negligible. (c) Suppose we are given Tarzan s mass and asked to find the tension in the vine. We define the system of interest as shown and draw a free-body diagram as shown in (d). F T F T is no longer shown because it does not act on the system of interest; rather, F T F T acts on the outside world. (d) The free-body diagram shows only the external forces acting on Tarzan. For these to sum to zero, we must have T = W . T = W . 

Next, make a list of knowns and unknowns and assign variable names to the quantities given in the problem. Figure out which variables need to be calculated; these are the unknowns. Now carefully define the system, meaning which objects are of interest for the problem. This decision is important, because Newton s second law involves only external forces. Once the system is identified, it s possible to see which forces are external and which are internal (see [link] ). 

If the system acts on an object outside the system, you then know that the outside object exerts a force of equal magnitude but in the opposite direction on the system. 

A diagram showing the system of interest and all the external forces acting on it is called a free-body diagram. Only external forces are shown on free-body diagrams, not acceleration or velocity. [link] shows a free-body diagram for the system of interest. 

After drawing a free-body diagram, apply Newton s second law to solve the problem. This is done in [link] for the case of Tarzan hanging from a vine. When external forces are clearly identified in the free-body diagram, translate the forces into equation form and solve for the unknowns. Note that forces acting in opposite directions have opposite signs. By convention, forces acting downward or to the left are usually negative. 

[link] Newton s Third Law of Motion 

This video explains Newton s third law of motion through examples involving push, normal force, and thrust (the force that propels a rocket or a jet). 

[link] An Accelerating Subway Train 

A physics teacher pushes a cart of demonstration equipment to a classroom, as in [link] Her mass is 65.0 kg, the cart s mass is 12.0 kg, and the equipment s mass is 7.0 kg. To push the cart forward, the teacher s foot applies a force of 150 N in the opposite direction (backward) on the floor. Calculate the acceleration produced by the teacher. The force of friction, which opposes the motion, is 24.0 N. Strategy 

Since they accelerate together, we define the system to be the teacher, the cart, and the equipment. The teacher pushes backward with a force F foot F foot of 150 N. According to Newton s third law, the floor exerts a forward force F floor F floor of 150 N on the system. Because all motion is horizontal, we can assume that no net force acts in the vertical direction, and the problem becomes one dimensional. As noted in the figure, the friction f opposes the motion and therefore acts opposite the direction of F floor . F floor . 

We should not include the forces F teacher F teacher , F cart F cart , or F foot F foot because these are exerted by the system, not on the system. We find the net external force by adding together the external forces acting on the system (see free-body diagram in the figure) and then use Newton s second law to find the acceleration. Solution 

Newton s second law is a = F net m . a = F net m . 

The net external force on the system is the sum of the external forces: the force of the floor acting on the teacher, cart, and equipment (in the horizontal direction) and the force of friction. Because friction acts in the opposite direction, we assign it a negative value. Thus, for the net force, we obtain F net = F floor f = 150 N 24 .0 N = 126 N F net = F floor f = 150 N 24 .0 N = 126 N 

The mass of the system is the sum of the mass of the teacher, cart, and equipment: m = ( 6 5 . 0 + 1 2 . 0 + 7 . 0 ) k g = 8 4 k g . m = ( 6 5 . 0 + 1 2 . 0 + 7 . 0 ) k g = 8 4 k g . 

Insert these values of net F and m into Newton s second law to obtain the acceleration of the system: a = F net m a = 1 2 6 N 84 kg = 1 . 5 m/s 2 . a = F net m a = 1 2 6 N 84 kg = 1 . 5 m/s 2 . Discussion 

None of the forces between components of the system, such as between the teacher s hands and the cart, contribute to the net external force because they are internal to the system. Another way to look at this is to note that forces between components of a system cancel because they are equal in magnitude and opposite in direction. For example, the force exerted by the teacher on the cart is of equal magnitude but in the opposite direction of the force exerted by the cart on the teacher. In this case both forces act on the same system, so they cancel. Defining the system was crucial to solving this problem. Practice Problems 

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[link] Section Summary Newton s third law of motion states that, when one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that it exerts. When objects rest on a surface, the surface applies a force on the object that opposes the weight of the object. This force acts perpendicular to the surface and is called the normal force. The pulling force that acts along a stretched flexible connector, such as a rope or cable, is called tension. When a rope supports the weight of an object at rest, the tension in the rope is equal to the weight of the object. Thrust is a force that pushes an object forward in response to the backward ejection of mass by the object. Rockets and airplanes are pushed forward by thrust. Key Equations Normal force for a non-accelerating horizontal surface N = m g N = m g Tension for an object at rest T = m g T = m g Check Your Understanding 

Use the questions in Check Your Understanding to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment through Check Your Understanding will help identify which objective is causing the problem and direct students to the relevant content. 

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This performance task gives your students the opportunity to practice content and skills that support the following NGSS performance expectations and/or science practices: NGSS HS-PS2-1 : Students who demonstrate understanding can: Analyze data to support the claim that Newton s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. Test Prep Multiple Choice 

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[link] Glossary Newton s third law of motion when one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that it exerts normal force the force that a surface applies to an object; acts perpendicular and away from the surface with which the object is in contact tension a pulling force that acts along a connecting medium, especially a stretched flexible connector, such as a rope or cable; when a rope supports the weight of an object, the force exerted on the object by the rope is called tension thrust a force that pushes an object forward in response to the backward ejection of mass by the object; rockets and airplanes are pushed forward by a thrust reaction force in response to ejecting gases backwards.Consequences of Special Relativity Consequences of Special Relativity Section Learning Objectives 

By the end of this section, you will be able to: Describe the relativistic effects seen in time dilation, length contraction, and conservation of relativistic momentum Explain and perform calculations involving mass-energy equivalence 

The learning objectives in this section will help your students master the following TEKS: (4F) : identify and describe motion relative to different frames of reference. (8C) : describe the significance of mass-energy equivalence and apply it in explanations of phenomena such as nuclear stability, fission, and fusion. Section Key Terms binding energy length contraction mass defect proper length relativistic relativistic momentum relativistic energy relativistic factor rest mass time dilation 

In this section, you will see how the postulates lead to the theory of special relativity and see how that theory predicts effects on time, distance, momentum, and energy at velocities approaching the speed of light. 

[BL] Begin a discussion by asking if students have ever seen a science fiction movie where space travelers age more slowly than the people left behind on Earth. Tell them there is some basis in fact to these stories. Discuss nuclear power. Ask if they know the basic difference between the nuclear power and combustion power. 

[OL] Explain that Newton s laws are valid for everyday mechanics, but break down at speeds approaching the speed of light. Discuss the relationship between relativity theory and Newton s laws. Briefly describe the changes predicted for measurements of time, length, momentum, and energy. See how much they know about energy derived from nuclear reactions. 

[AL] Ask what the students already know about relativity theory. See if they know that relative motion is an old idea and ask for examples of relative motion in everyday situations. Explain that special relativity is similar but describes unexpected results at speeds approaching the speed of light. Ask if anyone can explain why this statement is true: The original source of all the energy we use is the conversion of matter into energy. Relativistic Effects on Time, Distance, and Momentum 

Consideration of the measurement of elapsed time and simultaneity leads to an important relativistic effect. Time dilation is the phenomenon of time passing more slowly for an observer who is moving relative to another observer. 

For example, suppose an astronaut measures the time it takes for light to travel from the light source, cross her ship, bounce off a mirror, and return. (See [link] ). How does the elapsed time the astronaut measures compare with the elapsed time measured for the same event by a person on the Earth? Asking this question (another thought experiment) produces a profound result. We find that the elapsed time for a process depends on who is measuring it. In this case, the time measured by the astronaut is smaller than the time measured by the Earth-bound observer. The passage of time is different for the two observers because the distance the light travels in the astronaut s frame is smaller than in the Earth-bound frame. Light travels at the same speed in each frame, and so it will take longer to travel the greater distance in the Earth-bound frame. 

[OL] Discuss the expression for the relativistic factor. Explain that this is involved in all relativistic effects. Show how to tell when relativistic effects are significant and when they are negligible by plugging in values of v and c. (a) An astronaut measures the time t 0 t 0 for light to cross her ship using an electronic timer. Light travels a distance 2 D 2 D in the astronaut s frame. (b) A person on the Earth sees the light follow the longer path 2 s 2 s and take a longer time t t . 

[AL] [link] , like [link] , may be hard for some students to grasp. Refer back to the previous figure. The animation in the discussion of length contraction further on should also be some help. 

The relationship between t and t o is given by t = t 0 , t = t 0 , 

where is the relativistic factor given by = 1 1 v 2 c 2 , = 1 1 v 2 c 2 , 

and v and c are the speeds of the moving observer and light, respectively. 

Try putting some values for v into the expression for the relativistic factor ( ). Observe at which speeds this factor will make a difference and when is so close to 1 that it can be ignored. Try 225 m/s, the speed of an airliner; 2.98 10 4 m/s, the speed of Earth in its orbit; and 2.990 10 8 m/s, the speed of a particle in an accelerator. 

Try putting some values for v into the expression for the relativistic factor. Observe at which speeds this factor will make a difference and when it is so close to 1 that it can be ignored. 

Notice that when the velocity v is small compared to the speed of light c , then v/c becomes small, and becomes close to 1. When this happens, time measurements are the same in both frames of reference. Relativistic effects, meaning those that have to do with special relativity, usually become significant when speeds become comparable to the speed of light. This is seen to be the case for time dilation. 

You may have seen science fiction movies in which space travelers return to Earth after a long trip to find that the planet and everyone on it has aged much more than they have. This type of scenario is a based on a thought experiment, known as the twin paradox , which imagines a pair of twins, one of whom goes on a trip into space while the other stays home. When the space traveler returns, she finds her twin has aged much more than she. This happens because the traveling twin has been in two frames of reference , one leaving Earth and one returning. 

Time dilation has been confirmed by comparing the time recorded by an atomic clock sent into orbit to the time recorded by a clock that remained on Earth. GPS satellites must also be adjusted to compensate for time dilation in order to give accurate positioning. 

Have you ever driven on a road, like that shown in [link] , that seems like it goes on forever? If you look ahead, you might say you have about 10 km left to go. Another traveler might say the road ahead looks like it s about 15 km long. If you both measured the road, however, you would agree. Traveling at everyday speeds, the distance you both measure would be the same. You will read in this section, however, that this is not true at relativistic speeds. Close to the speed of light, distances measured are not the same when measured by different observers moving with respect to each other. People might describe distances differently, but at relativistic speeds, the distances really are different. (credit: Corey Leopold, Flickr) 

[OL] Discuss the relationship between time dilation and length contraction. If observers agree on speed, but not on time, they must also disagree on length because v = d/t . 

One thing all observers agree upon is their relative speed . When one observer is traveling away from another, they both see the other receding at the same speed, regardless of whose frame of reference is chosen. Remember that speed equals distance divided by time: v = d/t . If the observers experience a difference in elapsed time, they must also observe a difference in distance traversed. This is because the ratio d/t must be the same for both observers. 

The shortening of distance experienced by an observer moving with respect to the points whose distance apart is measured is called length contraction . Proper length , L 0 , is the distance between two points measured in the reference frame where the observer and the points are at rest. The observer in motion with respect to the points measures L . These two lengths are related by the equation L = L 0 L = L 0 

Because is the same expression used in the time dilation equation above, the equation becomes L = L 0 1 v 2 c 2 . L = L 0 1 v 2 c 2 . 

To see how length contraction is seen by a moving observer, go to this simulation . Here you can also see that simultaneity, time dilation, and length contraction are interrelated phenomena. 

This link is to a simulation that illustrates the relativity of simultaneous events. 

In classical physics, momentum is a simple product of mass and velocity. When special relativity is taken into account, objects that have mass have a speed limit. What effect do you think mass and velocity have on the momentum of objects moving at relativistic speeds, i.e., speeds close to the speed of light? 

Momentum is one of the most important concepts in physics. The broadest form of Newton s second law is stated in terms of momentum. Momentum is conserved in classical mechanics whenever the net external force on a system is zero. This makes momentum conservation a fundamental tool for analyzing collisions. We will see that momentum has the same importance in modern physics. Relativistic momentum is conserved, and much of what we know about subatomic structure comes from the analysis of collisions of accelerator-produced relativistic particles. 

One of the postulates of special relativity states that the laws of physics are the same in all inertial frames. Does the law of conservation of momentum survive this requirement at high velocities? The answer is yes, provided that the momentum is defined as follows. 

Relativistic momentum, p , is classical momentum multiplied by the relativistic factor . p = m u , p = m u , 

where m m is the rest mass of the object (that is the mass measured at rest, without any factor involved), u u is its velocity relative to an observer, and , as before, is the relativistic factor. We use the mass of the object as measured at rest because we cannot determine its mass while it is moving. 

Note that we use u u for velocity here to distinguish it from relative velocity v v between observers. Only one observer is being considered here. With p p defined in this way, p tot p tot is conserved whenever the net external force is zero, just as in classical physics. Again we see that the relativistic quantity becomes virtually the same as the classical at low velocities. That is, relativistic momentum m u m u becomes the classical m u m u at low velocities, because is very nearly equal to 1 at low velocities. 

Relativistic momentum has the same intuitive feel as classical momentum. It is greatest for large masses moving at high velocities. Because of the factor , , however, relativistic momentum behaves differently from classical momentum by approaching infinity as u u approaches c c . (See [link] .) This is another indication that an object with mass cannot reach the speed of light. If it did, its momentum would become infinite, which is an unreasonable value. Relativistic momentum approaches infinity as the velocity of an object approaches the speed of light. 

[OL] Discuss the graph. Explain how it shows that objects that have mass cannot reach the speed of light. Have them analyze the equation for relativistic momentum and see how this supports this conclusion. Explain that light can travel at the speed of light because it has no rest mass. 

Relativistic momentum is defined in such a way that the conservation of momentum will hold in all inertial frames. Whenever the net external force on a system is zero, relativistic momentum is conserved, just as is the case for classical momentum. This has been verified in numerous experiments. Mass-Energy Equivalence 

Let us summarize the calculation of relativistic effects on objects moving at speeds near the speed of light. In each case we will need to calculate the relativistic factor, given by: = 1 1 v 2 c 2 , = 1 1 v 2 c 2 , 

where v and c are as defined earlier. We use u as the velocity of a particle or an object in one frame of reference, and v for the velocity of one frame of reference with respect to another. Time Dilation 

Elapsed time on a moving object, t 0 t 0 , as seen by a stationary observer is given by t = t 0 , t = t 0 , where t 0 t 0 is the time observed on the moving object when it is taken to be the frame or reference. Length Contraction 

Length measured by a person at rest with respect to a moving object, L , is given by L = L 0 , L = L 0 , 

where L 0 is the length measured on the moving object. Relativistic Momentum 

Momentum, p , of an object of mass, m , traveling at relativistic speeds is given by p = m u p = m u , where u is velocity of a moving object as seen by a stationary observer. Relativistic Energy 

The original source of all the energy we use is the conversion of mass into energy. Most of this energy is generated by nuclear reactions in the sun and radiated to Earth in the form of electromagnetic radiation, where it is then transformed into all the forms with which we are familiar. The remaining energy from nuclear reactions is produced in nuclear power plants and in Earth s interior. In each of these cases, the source of the energy is the conversion of a small amount of mass into a large amount of energy. These sources are shown in [link] . The Sun (a) and the Susquehanna Steam Electric Station (b) both convert mass into energy. (credits: (a) NASA/Goddard Space Flight Center, Scientific Visualization Studio; (b) U.S. government) 

The first postulate of relativity states that the laws of physics are the same in all inertial frames. Einstein showed that the law of conservation of energy is valid relativistically, if we define energy to include a relativistic factor. The result of his analysis is that a particle or object of mass m moving at velocity u has relativistic energy given by E = m c 2 . E = m c 2 . 

This is the expression for the total energy of an object of mass m at any speed u and includes both kinetic and potential energy . Look back at the equation for and you will see that it is equal to 1 when u is 0, that is, when an object is at rest. Then the rest energy, E 0 , is simply E 0 = m c 2 . E 0 = m c 2 . 

This is the correct form of Einstein s famous equation. 

This equation is very useful to nuclear physicists because it can be used to calculate the energy released by a nuclear reaction. This is done simply by subtracting the mass of the products of such a reaction from the mass of the reactants. The difference is the m in E 0 = m c 2 E 0 = m c 2 . Here is a simple example: 

A positron is a type of antimatter that is just like an electron, except that it has a positive charge. When a positron and an electron collide, their masses are completely annihilated and converted to energy in the form of gamma rays. Because both particles have a rest mass of 9.11 10 31 kg, we multiply the mc 2 term by 2. So the energy of the gamma rays is E 0 = 2 ( 9.11 10 31 kg ) ( 3.00 10 8 m s ) 2 = 1.64 10 13 kg m 2 s 2 = 1.64 10 13 J E 0 = 2 ( 9.11 10 31 kg ) ( 3.00 10 8 m s ) 2 = 1.64 10 13 kg m 2 s 2 = 1.64 10 13 J 

where we have the expression for the joule (J) in terms of its SI base units of kg, m, and s. In general, the nuclei of stable isotopes have less mass then their constituent subatomic particles. The energy equivalent of this difference is called the binding energy of the nucleus. This energy is released during the formation of the isotope from its constituent particles because the product is more stable than the reactants. Expressed as mass, it is called the mass defect . For example, a helium nucleus is made of two neutrons and two protons and has a mass of 4.0003 atomic mass units (u). The sum of the masses of two protons and two neutrons is 4.0330 u. The mass defect then is 0.0327 u. Converted to kg, the mass defect is 5.0442 10 30 kg. Multiplying this mass times c 2 gives a binding energy of 4.540 10 12 J. This doesn t sound like much because it is only one atom. If you were to make one gram of helium out of neutrons and protons, it would release 683,000,000,000 J. By comparison, burning one gram of coal releases about 24 J. 

[BL] In regards to the change in the law of conservation of energy to the law of conservation of mass-energy, it may help to think of mass as simply a very concentrated form of energy. 

[OL] Impress upon the students the enormous amount of energy derived from the conversion of a small amount of mass. Have them note that c 2 is a very large number. Students try to understand new concepts by using previous knowledge, and that may result in a misconception here. They are comfortable with chemical reactions and may try to relate this to the burning of a piece of wood. Tell them that burning the wood chemically might provide energy for a single room in a house, but converting the mass of the wood completely to energy according to E = mc 2 would provide power for thousands of houses. 

[AL] Ask students if they know the difference between fission and fusion and where examples of each of these occur. The RHIC Collider 

[link] shows the Brookhaven National Laboratory in Upton, NY. The circular structure houses a particle accelerator called the RHIC, which stands for Relativistic Heavy Ion Collider. The heavy ions in the name are gold nuclei that have been stripped of their electrons. Streams of ions are accelerated in several stages before entering the big ring seen in the figure. Here they are accelerated to their final speed, which is about 99.7% the speed of light. Such high speeds are called relativistic. All the relativistic phenomena we have been discussing in this chapter are very pronounced in this case. At this speed = 12.9, so that relativistic time dilates by a factor of about 13, and relativistic length contracts by the same factor. Brookhaven National Laboratory. The circular structure houses the RHIC. (credit: energy.gov, Wikimedia Commons) 

Two ion beams circle the 2.4-mile long track around the big ring in opposite directions. The paths can then be made to cross thereby causing ions to collide. The collision event is very short-lived but amazingly intense. The temperatures and pressures produced are greater than those in the hottest suns. At 4 trillion degrees Celsius, this is the hottest material ever created in a laboratory 

But what is the point of creating such an extreme event? Under these conditions, the neutrons and protons that make up the gold nuclei are smashed apart into their components, which are called quarks and gluons. The goal is to recreate the conditions that theorists believe existed at the very beginning of the universe. It is thought that at that time matter was a sort of soup of quarks and gluons. When things cooled down after the initial bang, these particles condensed to form protons and neutrons. 

Some of the results have been surprising and unexpected. It was thought the quark-gluon soup would resemble a gas or plasma. Instead it behaves more like a liquid. It has been called a perfect liquid because it has virtually no viscosity (meaning that it has no resistance to flow.) 

Discuss particle colliders such as the relatively new Large Hadron Collider built by CERN. Students may want to know more about this project and the God particle. Explain why there are so many applications of special relativity theory in the field of particle physics. 

[link] The Speed of Light 

One night you are out looking up at the stars and an extraterrestrial spaceship flashes across the sky. The ship is 50 meters long and is travelling at 95% of the speed of light. What would the ship s length be when measured from your Earthbound frame of reference? Strategy 

List the knowns and unknowns: 

knowns: proper length of the ship, L 0 = 50 m; velocity, v , = 0.95 c 

unknowns: observed length of the ship accounting for relativistic length contraction, L . 

Choose the relevant equation: L = L 0 = L 0 1 u 2 c 2 . L = L 0 = L 0 1 u 2 c 2 . Solution L = 50 m 1 ( 0.95 ) 2 c 2 c 2 = 50 m 1 ( 0.95 ) 2 = 16 m L = 50 m 1 ( 0.95 ) 2 c 2 c 2 = 50 m 1 ( 0.95 ) 2 = 16 m Discussion 

Calculations of can usually be simplified in this way when v is expressed as a percentage of c because the c 2 terms cancel. Be sure to also square the decimal representing the percentage before subtracting from 1. Note that the aliens will still see the length as L 0 because they are moving with the frame of reference that is the ship. 

Identify the variables, the knowns and unknowns, and the relevant equation. Understand clearly which length applies to your frame of reference and which applies to the ship s frame of reference, that is, which is proper length. Practice Problems 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which and direct students to the relevant content. Section Summary Time dilates, length contracts, and momentum increases as an object approaches the speed of light. Energy and mass are interchangeable, according to the relationship E = mc 2. The laws of conservation of mass and energy are combined into the law of conservation of mass-energy. Key Equations Elapsed time t = t 0 t = t 0 Relativistic factor = 1 1 u 2 c 2 = 1 1 u 2 c 2 Length contraction L = L 0 L = L 0 Relativistic momentum p = m u p = m u Relativistic energy E = m c 2 E = m c 2 Rest energy E 0 = m c 2 . E 0 = m c 2 . Concept Items 

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People are fascinated by the possibility of traveling across the universe to discover intelligent life on other planets. To do this, we would have to travel enormous distances. Suppose we could somehow travel at up to 90% of the speed of light. The closest star is Alpha Centauri, which is 4.37 light years away. (A light year is the distance light travels in one year.) How long, from the point of view of people on Earth, would it take a space ship to travel to Alpha Centauri and back at 0.9 c ? How much would the astronauts on the spaceship have aged by the time they got back to Earth? Discuss the problems related to travel to stars that are 20 or 30 light years away. Assume travel speeds near the speed of light. Glossary binding energy the energy equivalent of the difference between the mass of a nucleus and the masses of its nucleons length contraction the shortening of an object as seen by an observer who is moving relative to the frame of reference of the object mass defect of the difference between the mass of a nucleus and the masses of its nucleons. proper length the length of an object within its own frame of reference, as opposed to the length observed by an observer moving relative to that frame of reference relativistic having to do with modern relativity, such as the effects that become significant only when an object is moving close enough to the speed of light for to be significantly greater than 1 relativistic energy the total energy of a moving object or particle E = m c 2 E = m c 2 , which includes both its rest energy mc 2 and its kinetic energy relativistic factor = 1 1 u 2 c 2 = 1 1 u 2 c 2 , where u is the velocity of a moving object and c is the speed of light relativistic momentum p = m u , where is the relativistic factor, m is rest mass of an object, and u is the velocity relative to an observer rest mass the mass of an object that is motionless with respect to its frame of reference time dilation the contraction of time as seen by an observer in a frame of reference that is moving relative to the observerPostulates of Special Relativity Postulates of Special Relativity Section Learning Objectives 

By the end of this section, you will be able to: Describe the experiments and scientific problems that led Albert Einstein to develop the special theory of relativity Understand the postulates on which the special theory of relativity was based 

The learning objectives in this section will help your students master the following TEKS: (2C) : Know that scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well-established and well-tested explanations, but may be subject to change as new areas of science and new technologies are developed. (3D) : Explain the impacts of the scientific contributions of a variety of historical and contemporary scientists on scientific thought and society. (4F) : Identify and describe motion relative to different frames of reference. Section Key Terms ether frame of reference inertial reference frame general relativity postulate relativity simultaneity special relativity 

[AL] Discuss the history of the concept of the ether. Explain that it more of a philosophical concept that was important prior to the development of modern science. It arose from the belief that matter was continuous and vacuums were impossible. Ether was sometimes considered to be one of the elements. 

[BL] [OL] Mention that electromagnetic waves are unique among wave-propagated energy forms, in that they can travel across empty space. This was difficult to believe and caused scientists to doggedly hang onto the idea that there must be an ether permeating space. Ask students what they know about Einstein and dispel any misconceptions. Explain what thought experiments and postulates are. Scientific Experiments and Problems 

Relativity is not new. Way back around the year 1600, Galileo explained that motion is relative. Wherever you happen to be, it seems like you are at a fixed point and that everything moves with respect to you. Everyone else feels the same way. Motion is always measured with respect to a fixed point. This is called establishing a frame of reference . But the choice of the point is arbitrary, and all frames of reference are equally valid. A passenger in a moving car is not moving with respect to the driver, but they are both moving from the point of view of a person on the sidewalk waiting for a bus. They are moving even faster as seen by a person in a car coming toward them. It s all relative. 

[OL] [AL] Focus students thinking on the speed of light. Can the students think of anything else that has a maximum allowable value and is also a universal constant? Most constants are just numbers, like the value of pi. Most properties, such as mass and volume have no fixed upper limit. Why does speed have a limit? 

A frame of reference is not a complicated concept. It is just something you decide is a fixed point or group of connected points. It is completely up to you. For example, when you look up at celestial objects in the sky, you choose the Earth as your frame of reference and the sun, moon, etc. seem to move across the sky. 

Light is involved in the discussion of relativity because theories related to electromagnetism are inconsistent with Galileo s and Newton s explanation of relativity. The true nature of light was a hot topic of discussion and controversy in the late nineteenth century. At the time, it was not generally believed that light could travel across empty space. It was known to travel as waves, and all other types of energy that propagated as waves needed to travel though a material medium. It was believed that space was filled with an invisible medium that light waves traveled through. This imaginary (as it turned out) material was called the ether (also spelled aether). It was thought that everything moved through this mysterious fluid. In other words, ether was the one fixed frame of reference. The Michelson Morley experiment proved it was not. 

In 1887 Albert Michelson and Edward Morley designed the interferometer shown in [link] to measure the speed of Earth through the ether. A light beam is split into two perpendicular paths and then recombined. Recombining the waves produces an inference pattern, with a bright fringe at the locations where the two waves arrive in phase, that is, with the crests of both waves arriving together and the troughs arriving together. A dark fringe appears where the crest of one wave coincides with a trough of the other, so that the two cancel. If Earth is traveling through the ether as it orbits the sun, the peaks in one arm would take longer than in the other to reach the same location. The places where the two waves arrive in phase would change, and the interference pattern would shift. But, using the interferometer, there was no shift seen! This result led to two conclusions: that there is no ether and that the speed of light is the same regardless of the relative motion of source and observer. The Michelson Morley investigation has been called the most famous failed experiment in history. This is a diagram of the instrument used in the Michelson-Morley experiment. 

[BL] [OL] Explain the geometry of the Michelson Morley experiment. Explain why failure in this case was actually a success. Discuss how accepting unexpected results is an important ability for scientists. Ask students to memorize the value of the speed of light in m/s to three significant figures. 

To see what Michelson and Morley expected to find when they measured the speed of light in two directions, watch this animation . In the video, two people swimming in a lake are represented as an analogy to light beams leaving Earth as it moves through the ether (if there were any ether). The swimmers swim away from and back to a platform that is moving through the water. The swimmers swim in different directions with respect to the motion of the platform. Even though they swim equal distances at the same speed, the motion of the platform causes them to arrive at different times. 

[AL] Be sure students understand that this animation does not explain how light behaves. It shows what Michelson and Morley expected to observe. It may work best to just introduce the Michelson-Morley experiment briefly and then watch the animation. Einstein s Postulates 

The results described above left physicists with some puzzling and unsettling questions, such as: why doesn t light emitted by a fast moving object travel faster than light from a street lamp? A radical new theory was needed, and Albert Einstein, shown in [link] , was about to become everyone s favorite genius. Einstein began with two simple postulates based on the two things we have discussed so far in this chapter. The laws of physics are the same in all inertial reference frames. The speed of light is the same in all inertial reference frames and is not affected by the speed of its source. Albert Einstein (1879 1955) developed modern relativity and also made fundamental contributions to the foundations of quantum mechanics. (credit: The Library of Congress) 

The speed of light is given the symbol c and is equal to exactly 299,792,458 m/s. This is the speed of light in vacuum, that is, in the absence of air. For most purposes, we round this number off to 3.00 10 8 m/s 3.00 10 8 m/s . The term inertial reference frame simply refers to a frame of reference where all objects follow Newton s first law of motion: Objects at rest remain at rest, and objects in motion remain in motion at a constant velocity in a straight line, unless acted upon by an external force. The inside of a car moving along a road at constant velocity and the inside of a stationary house are inertial reference frames. 

[BL] Ask students to round off the value given for c to 3 significant figures and express in scientific notation. Stress the units of measurements. 

[OL] Explain the postulates carefully. Note that, although they both seem true they lead to problems with the classical mechanics of Newton. Explain the concept of reference frame and ask students to think of examples of reference frames that are moving relative to each other. Use vehicles and celestial bodies. Explain that the understanding of relative motion goes back hundreds of years and did not begin with relativity theory. 

[AL] Explain that it is the combination of these two postulates that leads to unusual results that will follow in the next section and that it is the combination of these postulates that forces us to abandon some aspects of Newtonian physics in some scenarios. 

Note that the very precise value for the speed of light only applies to light traveling through a vacuum and that in all transparent material media it is slower. The Speed of Light 

This lecture on light summarizes the most important facts about the speed of light. If you are interested, you can watch the whole video, but the parts relevant to this chapter are found between 3:25 and 5:10, which you find by running your cursor along the bottom of the video. 

Only the section from 3:25 to 5:10 minutes is completely relevant to an understanding of the speed of light. If students watch it just after the text above, they will be adequately prepared. 

[link] Measure the Speed of Light 

In this experiment, you will measure the speed of light using a microwave oven and a slice of bread. The waves generated by a microwave oven are not part of the visible spectrum, but they are still electromagnetic radiation, so they travel at the speed of light. If we know the wavelength, , and frequency, f , of a wave we can calculate its speed, v , using the equation v = f . You can measure the wavelength. You will find the frequency on a label on the back of a microwave oven. The wave in a microwave is a standing wave with areas of high and low intensity. The high intensity sections are one-half wavelength apart. High temperature: Very hot temperatures are encountered in this lab. These can cause burns. a microwave oven one slice of plain white bread a centimeter ruler a calculator Work with a partner. Turn off the revolving feature of the microwave oven or remove the wheels under the microwave dish that make it turn. It is important that the dish doesn t turn. Place the slice of bread on the dish, set the microwave on high, close the door, run the microwave for about 15 seconds. A row of brown or black marks should appear on the bread. Stop the microwave as soon as they appear. Measure the distance between two adjacent burn marks and multiply the result by 2. This is the wavelength. The frequency of the waves is written on the back of the microwave. Look for something like 2,450 MHz. Hz is the unit hertz, which means per second. The M represents mega, which stands for million, so multiply the number by 10 6 . Express the wavelength in meters and multiply it times the frequency. If you did everything correctly, you will get a number very close to the speed of light. Do not eat the bread. It is a general laboratory safety rule never to eat anything in the lab. 

This experiment could be demonstrated to the class if a microwave is available in the classroom. It might be better to let the students do the experiment at home so they can get more of a hands-on experience. Before the lab you might have them watch this video . 

To continue the discussion, you could tell them about how light is refracted when it changes speed as it passes from one medium to another. Because light speed in air is slower than in a vacuum, light is refracted as it enters Earth s atmosphere. 

This link takes you to a video demonstrating how to measure the speed of light using a microwave, a ruler, and a bar of chocolate. There is also an accompanying article with background information on measuring the speed of light. 

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[AL] This will be difficult to grasp completely for some students. The fact that the observers see different things is the result of the two postulates being true. If light speed is a constant and the two frames of reference are both valid, then simultaneity is not the same for all observers. Ask them to try the thought experiment in their own head to grasp what is being shown here. Sometimes students have fun sketching a cartoon that explains or demonstrates difficult concepts. They can then show the cartoon to the class and explain their reasoning. 

[OL] If students are struggling with this explanation of simultaneity, let them know that there will be an animation in the next section that should make it clearer. 

[OL] [BL] Point out that the relationship between special relativity and Newton s mechanics is an excellent example of how science advances. Explain that new theories rarely reverse old theories. It is more common that new theories extend and expand on old theories. Ask students if they can think of other examples from the history of science. 

Einstein s postulates were carefully chosen, and they both seemed very likely to be true. Einstein proceeded despite realizing that these two ideas taken together and applied to extreme conditions led to results that contradict Newtonian mechanics. He just took the ball and ran with it. 

In the traditional view, velocities are additive. If you are running at 3 m/s and you throw a ball forward at a speed of 10 m/s, the ball should have a net speed of 13 m/s. However, according to relativity theory, the speed of a moving light source is not added to the speed of the emitted light. 

In addition, Einstein s theory shows that if you were moving forward relative to Earth at nearly c (the speed of light) and could throw a ball forward at c , an observer at rest on the Earth would not see the ball moving at nearly twice the speed of light. The observer would see it moving at a speed that is still less than c . This result conforms to both of Einstein s postulates: The speed of light has a fixed maximum and neither reference frame is privileged. 

Consider how we measure elapsed time. If we use a stopwatch, for example, how do we know when to start and stop the watch? One method is to use the arrival of light from the event, such as observing a light turn green to start a drag race. The timing will be more accurate if some sort of electronic detection is used, avoiding human reaction times and other complications. 

Now suppose we use this method to measure the time interval between two flashes of light produced by flash lamps on a moving train. (See [link] ) Light arriving to observer A as seen by two different observers. 

A woman (observer A) is seated in the center of a rail car, with two flash lamps at opposite sides equidistant from her. Multiple light rays that are emitted from the flash lamps move towards observer A (as shown with arrows). A velocity vector arrow for the rail car is shown towards the right. A man (observer B) standing on the platform is facing her and also observes the flashes of light. 

Observer A moves with the lamps on the rail car as the rail car moves towards the right of observer B. Observer B receives the light flashes simultaneously, and sees the bulbs as both having flashed at the same time. However, he sees observer A receive the flash from the right first. Because the pulse from the right reaches her first, in her frame of reference she sees the bulbs as not having flashed simultaneously. Here, a relative velocity between observers affects whether two events at well-separated locations are observed to be simultaneous. Simultaneity , or whether different events occur at the same instant, depends on the frame of reference of the observer. Remember that velocity equals distance divided by time, so t = d/ v . If velocity appears to be different, then duration of time appears to be different. 

This illustrates the power of clear thinking. We might have guessed incorrectly that if light is emitted simultaneously, then two observers halfway between the sources would see the flashes simultaneously. But careful analysis shows this not to be the case. Einstein was brilliant at this type of thought experiment (in German, Gedankenexperiment ). He very carefully considered how an observation is made and disregarded what might seem obvious. The validity of thought experiments, of course, is determined by actual observation. The genius of Einstein is evidenced by the fact that experiments have repeatedly confirmed his theory of relativity. No experiments after that of Michelson and Morley were able to detect any ether medium. We will describe later how experiments also confirmed other predictions of special relativity , such as the distance between two objects and the time interval two events being different for two observers moving with respect to each other. 

In summary: Two events are defined to be simultaneous if an observer measures them as occurring at the same time (such as by receiving light from the events). Two events are not necessarily simultaneous to all observers. 

The discrepancies between Newtonian mechanics and relativity theory illustrate an important point about how science advances. Einstein s theory did not replace Newton s, but rather extended it. It is not unusual that a new theory must be developed to account for new information. In most cases, the new theory is built on the foundation of older theory. It is rare that old theories are completely replaced. 

In this chapter, you will learn about the theory of special relativity, but, as mentioned in the introduction, Einstein developed two relativity theories: special and general. [link] summarizes the differences between the two theories Comparing Special Relativity and General Relativity Special Relativity General Relativity Published in 1905 Final form published in 1916 A theory of space-time A theory of gravity Applies to observers moving at constant speed Applies to observers that are accelerating Most useful in the field of nuclear physics Most useful in the field of astrophysics Accepted quickly and put to practical use by nuclear physicists and quantum chemists Largely ignored until 1960 when new mathematical techniques made the theory more accessible and astronomers found some important applications Also note that the theory of general relativity includes the theory of special relativity. Calculating the Time it Takes Light to Travel a Given Distance 

The sun is 1.50 10 8 km from Earth. How long does it take light to travel from the sun to Earth in minutes and seconds? Strategy 

Identify knowns: 

Distance = 1.50 10 8 km 

Speed = 3.00 10 8 m/s 

Identify unknowns: 

Time 

Find the equation that relates knowns and unknowns: 

v = d t ; t = d v v = d t ; t = d v 

Be sure to use consistent units. Solution t = d v = ( 1.50 10 8 k m ) 10 3 m km 3.00 10 8 m s = 5.00 10 2 s t = d v = ( 1.50 10 8 k m ) 10 3 m km 3.00 10 8 m s = 5.00 10 2 s 500 s = 8 min and 20 s 500 s = 8 min and 20 s Discussion 

The answer is written as 5.00 10 2 rather than 500, in order to show that there are three significant figures. When astronomers witness an event on the sun, such as a sunspot, it actually happened minutes earlier. Compare 8 light minutes to the distance to stars, which are light years away. Any events on other stars happened years ago. 

Identify the three variables and choose the relevant equation. In physics, calculations are usually done using units of meters and seconds. Use scientific notation to keep track of significant figures. Practice Problems 

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[link] Check Your Understanding 

Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which and direct students to the relevant content. 

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[link] Section Summary One postulate of special relativity theory is that the laws of physics are the same in all inertial frames of reference. The other postulate is that the speed of light in a vacuum is the same in all inertial frames. Einstein showed that simultaneity (or lack of it) depends on the frame of reference of the observer. Key Equations Speed of light v = f v = f Constant value for the speed of light c = 3.00 10 8 m/s c = 3.00 10 8 m/s Concept Items 

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[link] Glossary ether scientists once believed there was a medium that carried light waves; eventually, experiments proved that ether does not exist frame of reference the point or collection of points arbitrarily chosen which motion is measured in relation to inertial reference frame a frame of reference where all objects follow Newton s first law of motion general relativity the theory proposed to explain gravity and acceleration postulate a statement that is assumed to be true for the purposes of reasoning in a scientific or mathematic argument relativity the explanation of how object move relative to one another simultaneity the property of events that occur at the same time special relativity the theory proposed to explain the consequences of requiring the speed of light and the laws of physics to be the same in all inertial framesIntroduction Introduction In this chapter you will learn about: Postulates of Special Relativity Consequences of Special Relativity class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" Special relativity explains why travel to other star systems, such as these in the Orion Nebula, is unlikely using our current level of technology. (credit: s58y, Flickr) 

Start a discussion that taps into the longing of humans to explore worlds beyond our planet. Is this basic human nature? Perhaps it is; humans have now been almost everywhere there is to go on this planet. Ask students why we haven t traveled to other star systems yet. Is it just a matter waiting a few years for technological advances, or is there a more daunting problem? If no one knows, tell them it all has to do with achievable speeds, and use this as a lead-in to Einstein s postulate related to the speed of light. 

Have you ever dreamed of travelling to other planets in faraway star systems? The trip might seem possible by traveling fast enough, but you will read in this chapter why it is not. In 1905 Albert Einstein developed the theory of special relativity . Einstein developed the theory to help explain inconsistencies between the equations describing electromagnetism and Newtonian mechanics and to explain why the ether didn t exist. This theory explains the limit on an object s speed among other implications. 

Relativity is the study of how different observers moving with respect to each other measure the same events. Galileo and Newton developed the first correct version of classical relativity. Einstein developed the modern theory of relativity. Modern relativity is divided into two parts. Special relativity deals with observers moving at constant velocity. General relativity deals with observers who are moving at constant acceleration. Einstein s theories of relativity made revolutionary predictions. Most importantly, his predictions have been verified by experiments. 

In this chapter you learn how experiments and puzzling contradictions in existing theories led to the development of the theory of special relativity. You will also learn the simple postulates on which the theory was based; a postulate is a statement that is assumed to be true for the purposes of reasoning in a scientific or mathematic argument. 

Before students begin this chapter, it is useful to review these concepts: Using significant figures in calculations Demonstrate how use the proper number of significant figures when adding and multiplying. Using scientific notation in calculations Demonstrate how use the proper scientific notation and operations in scientific notation (e.g. addition/subtraction, multiplication/division). Converting units Demonstrate how to convert from km/h to m/s. Calculating average Demonstrate how to average two numbers by dividing their sum by 2. Review the difference between mass and weight. Commonly used terms Explain that constant means "unchanging." Constant speed refers to speed that is not changing. Explain that initial means "starting. Initial time is the time at which the action of a problem begins. Explain that an object that is not moving is often described in physics as being at rest. 

To reinforce this description, and to open the door for a discussion of frame of reference, take an object, place it in front of the class, and ask someone to describe its motion. Students will likely respond that the object is at rest. Explain that this correct, but it is not the only correct answer. Help students to understand that the object is sitting still, but also moving at a high rate of speed as the earth rotates, orbits the sun, etc. It all depends on how you define the frame of reference. 

Initiate a discussion aimed at making relativity theory less intimidating. Dispel the misconception that Only three people in the world understand Einstein s theories. Stories like this come about because Einstein s second relativity theory, called general relativity, was more difficult to understand. In this chapter we will only learn about special relativity.Introduction Introduction class="introduction" In this chapter you will learn about: Physics: Definitions and Applications The Scientific Methods The Language of Physics: Physical Quantities and Units class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" 

Before students begin this chapter, it is useful to review these concepts: The definition of the atom and subatomic particles (electron, proton, neutron) Metric units Using significant figures in calculations Galaxies, such as the Andromeda galaxy pictured here, are immense in size. The small blue spots in this photo are also galaxies. The same physical laws apply to objects as large as galaxies or objects as small as atoms. The laws of physics are, therefore, surprisingly few in number. (credit: NASA, JPL-Caltech, P. Barmby, Harvard-Smithsonian Center for Astrophysics). 

The photo of the Andromeda galaxy and its subsequent mention in this chapter is meant to show students that the same laws of physics apply to extremely large systems, such as a galaxy, as apply also to smaller systems in our universe. The same laws that govern the movement of the stars within the Andromeda galaxy also explain the gravitational forces on Earth that all humans experience and interact with every second of their lives. 

Take a look at the image above of the Andromeda Galaxy ( [link] ), which contains billions of stars. This galaxy is the nearest one to our own galaxy (the Milky Way) but is still a staggering 2.5 million light years from Earth. (A light year is a measurement of the distance light travels in a year.) Yet, the primary force that affects the movement of stars within Andromeda is the same force that we contend with here on Earth namely, gravity. 

You may soon realize that physics plays a much larger role in your life than you thought. This section introduces you to the realm of physics, and discusses applications of physics in other disciplines of study. It also describes the methods by which science is done, and how scientists communicate their results to each other.Physics: Definitions and Applications Physics: Definitions and Applications Section Learning Objectives 

By the end of this section, you will be able to: Describe the definition, aims, and branches of physics Describe and distinguish classical physics from modern physics and describe the importance of relativity, quantum mechanics, and relativistic quantum mechanics in modern physics Describe how aspects of physics are used in other sciences (e.g. biology, chemistry, geology, etc.) as well as in everyday technology 

The learning objectives in this section will help your students master the following TEKS: (2A) : Know the definition of science and understand that it has limitations, as specified in subsection (b)(2) of this section. (3A) : In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. (3B) : Communicate and apply scientific information extracted from various sources such as current events, news reports, published journal articles, and marketing materials. (3C) : Draw inferences based on data related to promotional materials for products and services. (3D) : Explain the impacts of the scientific contributions of a variety of historical and contemporary scientists on scientific thought and society. Section Key Terms atom classical physics modern physics physics quantum mechanics theory of relativity 

To help meet the multimodal needs of classrooms today, OpenStax Tutor s Physics provides Teacher Support tips for on-level [OL], below-level [BL], and above-level [AL] students. 

[OL] Pre-assessment for this section could involve asking students the definition of matter, atoms, electrons, protons, neutrons, subatomic particles, and energy. Students could also be asked to name some prominent classical and modern physicists and to describe some of their work in general terms. 

[OL] The introduction and opening picture are meant to show students that the physical laws governing their own everyday surroundings also govern the movement of stars in a galaxy. Teachers could ask students how gravity affects life on Earth. Students will likely mention how gravity keeps us on Earth s surface. Prompt them, if necessary, to also think about Earth s orbital motion around the sun. This motion allows Earth bask in the warmth of the sun s light. Without the Sun s gravity, Earth would continue moving in a straight line and move away from the sun, while people would float off of Earth s surface. The orbit of the moon could also be brought into this discussion, because Earth s gravity keeps the moon moving around Earth rather than continuing in a straight path. What Physics Is 

Think about all of the technological devices that you use on a regular basis. Computers, wireless internet, smart phones, tablets, global positioning system (GPS), MP3 players, and satellite radio might come to mind. Next, think about the most exciting modern technologies that you have heard about in the news, such as trains that levitate above their tracks, invisibility cloaks that bend light around them, and microscopic robots that fight cancer cells in our bodies. All of these groundbreaking advancements rely on the principles of physics . 

Physics is the science aimed at describing the fundamental aspects of our universe, such as what things are in it, what properties of those things are noticeable, and what processes those things or their properties undergo. In simpler terms, physics attempts to describe the basic mechanisms that make our universe behave the way it does. For example, consider a smart phone ( [link] ). Physics describes how electric current interacts with the various circuits inside the device. This knowledge helps engineers select the appropriate materials and circuit layout when building the smart phone. Next, consider a GPS. Physics describes the relationship between the speed of an object, the distance over which it travels, and the time it takes to travel that distance. When you use a GPS device in a vehicle, it utilizes these physics relationships to determine the travel time from one location to another. Physics describes the way that electric charge flows through the circuits of this device. Engineers use their knowledge of physics to construct a smart phone with features that consumers will enjoy, such as a GPS function. GPS uses physics equations to determine the driving time between two locations on a map. (credit: @gletham GIS, Social, Mobile Tech Images) 

[AL] Ask what parts of a cell phone should contain conducting materials (wires, circuit boards, etc.) versus insulating materials (e.g., places where electrical insulation keeps humans from touching electrical circuits inside the phone). 

[AL] You can delve into GPS usage at this point by defining velocity = distance/time, discussing triangulation, and/or discussing line of sight. 

As our technology evolved over the centuries, physics expanded into many branches. Ancient peoples could only study things that they could see with the naked eye or otherwise experience without the aid of scientific equipment. This included the study of kinematics , which is the study of moving objects. For example, ancient people often studied the apparent motion of objects in the sky, such as the Sun, Moon, and stars. This is evident in the construction of prehistoric astronomical observatories, such as Stonehenge in England (shown in [link] ). 

Ancient people also studied statics and dynamics , which focus on how objects start moving, stop moving, and change speed and direction in response to forces that push or pull on the objects. This early interest in kinematics and dynamics allowed humans to invent simple machines, such as the lever, the pulley, the ramp, and the wheel. These simple machines were gradually combined and integrated to produce more complicated machines, such as wagons and cranes. Machines allowed humans to gradually do more work more effectively in less time, allowing them to create larger and more complicated buildings and structures, many of which still exist today from ancient times. Stonehenge is a monument located in England that was built between 3000 and 2000 BCE. It functions as an ancient astronomical observatory, with certain rocks in the monument aligning with the position of the Sun during the summer and winter solstices. Other rocks align with the rising and setting of the Moon during certain days of the year. (credit: Citypeek, Wikimedia Commons) 

As technology advanced, the branches of physics diversified even more. These include branches such as acoustics , the study of sound, and optics , the study of the light. The invention of the telescope by Hans Lippershey, a German spectacle maker, in 1608, led to huge breakthroughs in astronomy , the study of objects or phenomena in space. One year later, in 1609, Galileo Galilei began the first studies of the solar system and the universe using a telescope. During the Renaissance era, Isaac Newton used observations made by Galileo to construct his three laws of motion. These laws were the standard for studying kinematics and dynamics even today. 

Another major branch of physics is thermodynamics , which includes the study of thermal energy and the transfer of heat. James Prescott Joule, an English physicist, studied the nature of heat and its relationship to work. Joule s work helped lay the foundation for the first of three laws of thermodynamics that describe how energy in our universe is transferred from one object to another or transformed from one form to another. Studies in thermodynamics were motivated by the need to make engines more efficient, keep people safe from the elements, and preserve food. 

The eighteenth and nineteenth centuries also saw great strides in the study of electricity and magnetism. Electricity involves the study of electric charges and their movements. Magnetism had long ago been noticed as an attractive force between a magnetized object and a metal like iron, or between the opposite poles (North and South) of two magnetized objects. In 1820, Danish physicist Hans Christian Oersted showed that electric currents create magnetic fields. In 1831, English inventor Michael Faraday showed that moving a wire through a magnetic field could induce an electric current. These studies led to the inventions of the electric motor and electric generator, which revolutionized human life by bringing electricity and magnetism into our machines. 

The end of the 19 th century saw the discovery of radioactive substances by the French scientists Marie and Pierre Curie. Nuclear physics involves studying the nuclei of atoms , the source of nuclear radiation. In the 20 th century, the study of nuclear physics eventually led to the ability to split the nucleus of an atom, a process called nuclear fission. This process is the basis for nuclear power plants and nuclear weapons. Also, the field of quantum mechanics , which involves the mechanics of atoms and molecules, saw great strides during the 20 th century as our understanding of atoms and subatomic particles increased (see below). 

Early in the 20th century, Albert Einstein revolutionized several branches of physics, especially relativity . Relativity revolutionized our understanding of motion and the universe in general as described further in this chapter. Now, in the 21 st century, physicists continue to study these and many other branches of physics. 

By studying the most important topics in physics, you will gain analytical abilities that will enable you to apply physics far beyond the scope of what can be included in a single book. These analytical skills will help you to excel academically, and they will also help you to think critically in any career you choose to pursue. Physics: Past and Present 

The word physics is thought to come from the Greek word phusis, meaning nature. The study of nature later came to be called natural philosophy. From ancient times through the Renaissance, natural philosophy encompassed many fields, including astronomy, biology, chemistry, mathematics, and medicine. Over the last few centuries, the growth of scientific knowledge has resulted in ever-increasing specialization and branching of natural philosophy into separate fields, with physics retaining the most basic facets. Physics, as it developed from the Renaissance to the end of the 19th century, is called classical physics . Revolutionary discoveries starting at the beginning of the 20th century transformed physics from classical physics to modern physics . 

[BL] [EL]English learners may need philosophy and classical defined during this section. Relate the definition of classical physics to the use of the word classical in a context that is probably more familiar to students, such as classic films. 

Classical physics is not an exact description of the universe, but it is an excellent approximation under the following conditions: 1) matter must be moving at speeds less than about 1% of the speed of light, 2) the objects dealt with must be large enough to be seen with the naked eye, and 3) only weak gravity, such as that generated by Earth, can be involved. Very small objects, such as atoms and molecules, cannot be adequately explained by classical physics. These three conditions apply to almost all of everyday experience. As a result, most aspects of classical physics should make sense on an intuitive level. 

[OL] To better relate to student experience, express the speed of light in units used while driving a car, for example, 1.080 million km/h or 671 million miles per hour. Relate this to the approximately 8 minute trip that light takes to travel 150 billion kilometers (93 billion miles) from the Sun to the Earth. 

Many laws of classical physics have been modified during the twentieth century, resulting in revolutionary changes in technology, society, and our view of the universe. This new physics is called physics. As a result, many aspects of modern physics, which occur outside of the range of our everyday experience, may seem bizarre or unbelievable. So why is most of this textbook devoted to classical physics? There are two main reasons. The first is that knowledge of classical physics is necessary to understand modern physics. The second reason is that classical physics still gives an accurate description of the universe under a wide range of everyday circumstances. 

Modern physics includes two revolutionary theories: relativity and quantum mechanics. These theories deal with the very fast and the very small, respectively. The theory of relativity was developed by Albert Einstein in 1905. By examining how two observers moving relative to each other would see the same phenomena, Einstein devised radical new ideas about time and space. He came to the startling conclusion that the measured length of an object travelling at high speeds (greater than about 1% of the speed of light) is shorter than the same object measured at rest. Perhaps even more bizarre is the idea the time for the same process to occur is different depending on the motion of the observer. Time passes more slowly for an object travelling at high speeds. A trip to the nearest star system, Alpha Centauri, might take an astronaut 4.5 Earth years if the ship travels near the speed of light. However, because time is slowed at higher speeds, the astronaut would age only 0.5 years during the trip. Einstein s ideas of relativity were accepted after they were confirmed by numerous experiments. 

Gravity, the force that holds us to Earth, can also affect time and space. For example, time passes more slowly on Earth s surface than for objects farther from the surface, such as a satellite in orbit. The very accurate clocks on global positioning satellites have to correct for this. They slowly keep getting ahead of clocks at Earth s surface. This is called time dilation, and it occurs because gravity, in essence, slows down time. 

[AL] By saying that time passes more slowly at near-light speeds or high gravity, it is important to mention that people in both locations perceive the second as the same length of time. 

Large objects, like Earth, have strong enough gravity to distort space. To visualize this idea, think about a bowling ball placed on a trampoline. The bowling ball depresses or curves the surface of the trampoline. If you rolled a marble across the trampoline, it would follow the surface of the trampoline, roll into the depression caused by the bowling ball, and hit the ball. Similarly, the Earth curves space around it in the shape of a funnel. These curves in space due to the Earth cause objects to be attracted to Earth (i.e., gravity). 

Because of the way gravity affects space and time, Einstein stated that gravity affects the space-time continuum, as illustrated in [link] . This is why time proceeds more slowly at Earth s surface than in orbit. In black holes, whose gravity is hundreds of times that of Earth, time passes so slowly that it would appear to a far-away observer to have stopped! Einstein s theory of relativity describes space and time as an interweaved mesh. Large objects, such as a planet, distort space, causing objects to fall in toward the planet due to the action of gravity. Large objects also distort time, causing time to proceed at a slower rate near the surface of Earth compared with the area outside of the distorted region of space-time. 

[AL] Black holes are much more dense and massive than Earth. The greater an object s mass, the stronger the gravitational field it produces, and the more that gravity slows down time. 

In summary, relativity says that in describing the universe, it is important to realize that time, space, speed and gravity are not absolute. Instead, they can appear different to different observers. Einstein s ability to reason out relativity is even more amazing because we cannot see the effects of relativity in our everyday lives. 

Quantum mechanics is the second major theory of modern physics. Quantum mechanics deals with the very small, namely, the subatomic particles that make up atoms. Atoms ( [link] ) are the smallest units of elements. However, atoms themselves are constructed of even smaller subatomic particles, such as protons, neutrons and electrons. Quantum mechanics strives to describe the properties and behavior of these and other subatomic particles. Often, these particles do not behave in the ways expected by classical physics. One reason for this is that they are small enough to travel at great speeds, near the speed of light, for example. Using a scanning tunneling microscope (STM), scientists can see the individual atoms that compose this sheet of gold. (credit: Erwinrossen) 

[OL] [AL] Assess prior knowledge of subatomic particles by asking students if they have heard of protons, electrons, neutrons, as well as quarks, Higgs-Boson particles, and so on. 

[AL] Scanning electron microscopes generate highly-detailed surface views of objects such as that shown in [link] . They scan the object s surface with beams of electrons to detect the object s microscopic topography. 

At particle colliders ( [link] ), such as the Large Hadron Collider on the France-Swiss border, particle physicists can make subatomic particles travel at very high speeds within a 27 km (17 mi) long superconducting tunnel. They can then study the properties of the particles at high speeds, as well as collide them with each other to see how they exchange energy. This has led to many intriguing discoveries such as the Higgs-Boson particle, which gives matter the property of mass, and antimatter, which causes a huge energy release when it comes in contact with matter. Particle colliders such as the Large Hadron Collider in Switzerland or Fermilab in the United States (pictured here), have long tunnels that allows subatomic particles to be accelerated to near light speed (credit: Andrius.v ) 

Physicists are currently trying to unify the two theories of modern physics, relativity and quantum mechanics into a single, comprehensive theory called relativistic quantum mechanics. Relating the behavior of subatomic particles to gravity, time, and space will allow us to explain how the universe works in a much more comprehensive way. Application of Physics 

You need not be a scientist to use physics. On the contrary, knowledge of physics is useful in everyday situations as well as in nonscientific professions. For example, physics can help you understand why you shouldn t put metal in the microwave, why a black car radiator helps remove heat in a car engine, and why a white roof helps keep the inside of a house cool. (See [link] ) The operation of a car s ignition system, as well as the transmission of electrical signals through our nervous system, are much easier to understand when you think about them in terms of the basic physics of electricity. Microwave ovens use electromagnetic waves to heat food. (credit: MoneyBlogNewz) 

[AL] It is hazardous to put metal in the microwave because metal reflects microwaves, which, when free to bounce around the oven, can damage the oven. Also, the metal in the microwave oven gets very hot and begins generating an electrical field. This electrical field ionizes the air surrounding the metal, creating sparks. 

Physics is the foundation of many important scientific disciplines. For example, chemistry deals with the interactions of atoms and molecules. Not surprisingly, chemistry is rooted in atomic and molecular physics. Most branches of engineering are also applied physics. In architecture, physics is at the heart of determining structural stability, acoustics, heating, lighting, and cooling for buildings. Parts of geology, the study of the nonliving parts of Earth, rely heavily on physics, including radioactive dating, earthquake analysis, and heat transfer across Earth s surface. Indeed, some disciplines, such as biophysics and geophysics, are hybrids of physics and other disciplines. 

[BL] [EL]Students may need acoustics to be explained as the properties of a room or structure that determine how sound is transmitted within it. 

Physics also has many applications in biology, the study of life. For example, physics describes how cells can protect themselves using their cell walls and cell membranes. It also describes the chemical processes that power the human body. Physics is involved in medical diagnostics, such as x-rays, magnetic resonance imaging (MRI), and ultrasonic blood flow measurements ( [link] and [link] ). Medical therapy sometimes directly involves physics, such as in using radiation to treat cancer. Physics can also explain what we perceive with our senses, such as how the ears detect sound or the eye detects color. Magnetic resonance imaging (MRI) also uses electromagnetic waves to yield an image of the brain, from which the exact location of tumors can be determined. (credit: Rashmi Chawla, Daniel Smith, and Paul E. Marik) Physics, chemistry, and biology help describe the properties of cell walls in plant cells, such as the onion cells seen here. (credit: Umberto Salvagnin) 

[BL] Cell membranes (found in the cells of all organisms) control the transport of materials into and out of a cell. Cell walls (found in plant cells, fungus cells, bacteria, and plant-like microbes) mainly provide structure and support. 

[AL] X-rays easily penetrate skin and soft tissues but are absorbed to a far greater extent by bone. This produces an image where bones within the body are clearly visible while soft tissue is not. MRI scans for the magnetic properties of atoms within the body, allowing the solid versus empty areas within the body to be visualized. Ultrasonic blood flow measurements use sound waves and the Doppler effect to measure blood flow speed and volume. The Physics of Landing on a Comet 

On November 12, 2014, the European Space Agency s Rosetta spacecraft (shown in [link] ) became the first ever to reach and orbit a comet. Shortly after, Rosetta s rover, Philae, landed on the comet, representing the first time humans have ever landed a space probe on a comet. The Rosetta spacecraft, with its large and revolutionary solar panels, carried the Philae lander to a comet. The lander then detached and landed on the comet s surface. (Photo Credits: European Space Agency) 

The comet Rosetta landed on, named 67P/Churyumov-Gerasimenko, after traveling 6.4 billion kilometers starting from its launch on Earth. The comet, itself, is only 4 km wide. Physics was needed to successfully plot the course to reach such a small, distant, and rapidly moving target. Rosetta s path to the comet was not straight forward. The probe first had to travel to Mars so that Mars s gravity could accelerate it and divert it in the exact direction of the comet. 

This was not the first time humans used gravity to power our spaceships, however. Voyager 2, a space probe launched in 1977, used the gravity of Saturn to slingshot over to Uranus and Neptune (illustrated in [link] ), providing the first pictures ever taken of these planets. Now, almost 40 years after its launch, Voyager 2 is at the very edge of our solar system and is about to enter interstellar space. Its sister ship, Voyager 1 (illustrated in [link] ), which was also launched in 1977, is already there. 

To listen to the sounds of interstellar space or see images that have been transmitted back from the Voyager I or to learn more about the Voyager mission, visit the Voyager s Mission website . a) Voyager 2, launched in 1977, used the gravity of Saturn to slingshot over to Uranus and Neptune. Photo credit: NASA b) A rendering of Voyager 1, the first space probe to ever leave our solar system and enter interstellar space. Photo credit: NASA 

Both Voyagers have electrical power generators based on the decay of radioisotopes. These generators have served them for almost 40 years. Rosetta, on the other hand, is solar-powered. In fact, Rosetta became the first space probe to travel beyond the asteroid belt by relying only on solar cells for power generation. 

At 800 million kilometers from the Sun, Rosetta receives sunlight that is only 4% as strong as on Earth. In addition, it is very cold in space. Therefore, a lot of physics went into developing Rosetta s low-intensity low-temperature solar cells. 

In this sense, the Rosetta project nicely shows the huge range of topics encompassed by physics: from modeling the movement of gigantic planets over huge distances within our solar systems, to learning how to generate electric power from low-intensity light. Physics is, by far, the broadest field of science. 

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This passage describes the physics behind getting the Rosetta and Voyager probes across the solar system using gravitational sling shots. In addition, the physics behind the power systems of these probes is compared. This is meant to reinforce how physics applies over wide ranges, from the immense distances in our universe to the tiny sizes of subatomic particles. 

Answers to the Grasp Check may vary. A sample answer: You would have to how the target planet moves to know when to launch the probe so it actually reaches the planet. You would also need to know and account for the effects of gravity from other planets during the path followed during its journey. 

In summary, physics studies many of the most basic aspects of science. A knowledge of physics is, therefore, necessary to understand all other sciences. This is because physics explains the most basic ways in which our universe works. However, it is not necessary to formally study all applications of physics. A knowledge of the basic laws of physics will be most useful to you, so that you can use them to solve some everyday problems. In this way, the study of physics can improve your problem-solving skills. Check Your Understanding 

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Use the Check Your Understanding questions to assess students mastery of the sections learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify the source of the problem and direct students to the relevant content. Section Summary Physics is the most fundamental of the sciences, concerning itself with energy, matter, space and time, and their interactions. Modern physics involves the theory of relativity, which describes how time, space and gravity are not constant in our universe can be different for different observers, and quantum mechanics, which describes the behavior of subatomic particles. Physics is the basis for all other sciences, such as chemistry, biology and geology, because physics describes the fundamental way in which the universe functions. Concept Items 

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[link] Glossary atom smallest and most basic units of matter classical physics physics, as it developed from the Renaissance to the end of the nineteenth century modern physics physics as developed from the twentieth century to the present, involving the theories of relativity and quantum mechanics physics science aimed at describing the fundamental aspects of our universe, namely: energy, matter, space, motion, and time quantum mechanics major theory of modern physics which describes the properties and nature of atoms and their subatomic particles theory of relativity theory constructed by Albert Einstein which describes how space, time and energy are different for different observers in relative motionInclined Planes Inclined Planes Section Learning Objectives 

By the end of this section, you will be able to: Distinguish between static friction and kinetic friction Solve problems involving inclined planes 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in two dimensions for a variety of situations. The student is expected to: (D) : calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects Section Key Terms kinetic friction static friction Static Friction and Kinetic Friction 

Recall from the previous chapter that friction is a force that opposes motion, and is around us all the time. Friction allows us to move (which you have discovered if you have ever tried to walk on ice). 

There are different types of friction kinetic and static. Kinetic friction acts on an object in motion, while static friction acts on an object or system at rest. The maximum static friction is usually greater than the kinetic friction between the objects. 

[BL] [OL] Review the concept of friction. 

[AL] Start a discussion about the two kinds of friction: static and kinetic. Ask students which one they think would be greater for two given surfaces. Explain the concept of coefficient of friction and what the number would imply in practical terms. Look at the table of static and kinetic friction and ask students to guess which other systems would have higher or lower coefficients. 

Imagine, for example, trying to slide a heavy crate across a concrete floor. You may push harder and harder on the crate and not move it at all. This means that the static friction responds to what you do it increases to be equal to and in the opposite direction of your push. But if you finally push hard enough, the crate seems to slip suddenly and starts to move. Once in motion, it is easier to keep it in motion than it was to get it started because the kinetic friction force is less than the static friction force. If you were to add mass to the crate, (for example, by placing a box on top of it) you would need to push even harder to get it started and also to keep it moving. If, on the other hand, you oiled the concrete you would find it easier to get the crate started and keep it going. 

[link] shows how friction occurs at the interface between two objects. Magnifying these surfaces shows that they are rough on the microscopic level. So when you push to get an object moving (in this case, a crate), you must raise the object until it can skip along with just the tips of the surface hitting, break off the points, or do both. The harder the surfaces are pushed together (such as if another box is placed on the crate), the more force is needed to move them. Frictional forces, such as f , always oppose motion or attempted motion between objects in contact. Friction arises in part because of the roughness of the surfaces in contact, as seen in the expanded view. 

The magnitude of the frictional force has two forms: one for static friction, the other for kinetic friction. When there is no motion between the objects, the magnitude of static friction f s is f s s N s f s s N s 

where s s is the coefficient of static friction and N is the magnitude of the normal force. (Recall that the normal force opposes the force of gravity and acts perpendicular to the surface in this example, but not always). 

Since the symbol means less than or equal to, this equation says that static friction can have a maximum value of s N . s N . That is, f s (max) = s N f s (max) = s N 

Static friction is a responsive force that increases to be equal and opposite to whatever force is exerted, up to its maximum limit. Once the applied force exceeds f s(max), the object will move. Once an object is moving, the magnitude of kinetic friction f k is given by f k = k N f k = k N 

where k k is the coefficient of kinetic friction. 

Friction varies from surface to surface because different substances are rougher than others. [link] compares values of static and kinetic friction for different surfaces. The coefficient of the friction depends on the two surfaces that are in contact. Coefficients of Static and Kinetic Friction System Static Friction s s Kinetic Friction k k Rubber on dry concrete 1.0 0.7 Rubber on wet concrete 0.7 0.5 Wood on wood 0.5 0.3 Waxed wood on wet snow 0.14 0.1 Metal on wood 0.5 0.3 Steel on steel (dry) 0.6 0.3 Steel on steel (oiled) 0.05 0.03 Teflon on steel 0.04 0.04 Bone lubricated by synovial fluid 0.016 0.015 Shoes on wood 0.9 0.7 Shoes on ice 0.1 0.05 Ice on ice 0.1 0.03 Steel on ice 0.4 0.02 

Since the direction of friction is always opposite to the direction of motion, friction runs parallel to the surface between objects and perpendicular to the normal force. For example, if the crate you try to push (with a force parallel to the floor) has a mass of 100 kg, then the normal force would be equal to its weight W = m g = ( 100 kg ) ( 9.80 m/s 2 ) = 980 N , W = m g = ( 100 kg ) ( 9.80 m/s 2 ) = 980 N , 

perpendicular to the floor. If the coefficient of static friction is 0.45, you would have to exert a force parallel to the floor greater than f s (max) = s N = ( 0.45 ) ( 980 N) = 440 N f s (max) = s N = ( 0.45 ) ( 980 N) = 440 N 

to move the crate. Once there is motion, friction is less and the coefficient of kinetic friction might be 0.30, so that a force of only 290 N f k = k N = ( 0.30 ) ( 980 N) = 290 N f k = k N = ( 0.30 ) ( 980 N) = 290 N 

would keep it moving at a constant speed. If the floor were lubricated, both coefficients would be much smaller than they would be without lubrication. The coefficient of friction is unitless and is a number usually between 0 and 1.0. Working with Inclined Planes 

We discussed previously that when an object rests on a horizontal surface, there is a normal force supporting it equal in magnitude to its weight. Up until now, we dealt only with normal force in one dimension, with gravity and normal force acting perpendicular to the surface in opposing directions (gravity downward, and normal force upward). Now that you have the skills to work with forces in two dimensions, we can explore what happens to weight and the normal force on a tilted surface such as an inclined plane. For inclined plane problems, it is easier breaking down the forces into their components if we rotate the coordinate system, as illustrated in [link] . The first step when setting up the problem is to break down the force of weight into components. The diagram shows perpendicular and horizontal components of weight on an inclined plane. 

[BL] Review the concepts of mass, weight, gravitation and normal force. 

[OL] Review vectors and components of vectors. 

When an object rests on an incline that makes an angle with the horizontal, the force of gravity acting on the object is divided into two components: a force acting perpendicular to the plane, w w , and a force acting parallel to the plane, w | | w | | . The perpendicular force of weight, w w , is typically equal in magnitude and opposite in direction to the normal force, N . N . The force acting parallel to the plane, w | | w | | , causes the object to accelerate down the incline. The force of friction, f f , opposes the motion of the object, so it acts upward along the plane. 

It is important to be careful when resolving the weight of the object into components. If the angle of the incline is at an angle to the horizontal, then the magnitudes of the weight components are w | | = w s i n ( ) = m g s i n ( ) and w | | = w s i n ( ) = m g s i n ( ) and w = w c o s ( ) = m g c o s ( ) w = w c o s ( ) = m g c o s ( ) 

Instead of memorizing these equations, it is helpful to be able to determine them from reason. To do this, draw the right triangle formed by the three weight vectors. Notice that the angle of the incline is the same as the angle formed between w w and w w . Knowing this property, you can use trigonometry to determine the magnitude of the weight components: c o s ( ) = w w w = w c o s ( ) = m g c o s ( ) c o s ( ) = w w w = w c o s ( ) = m g c o s ( ) s i n ( ) = w | | w w | | = w s i n ( ) = m g s i n ( ) s i n ( ) = w | | w w | | = w s i n ( ) = m g s i n ( ) 

[BL] [OL] [AL] Experiment with sliding different objects on inclined planes to understand static and kinetic friction. Which objects need a larger angle to slide down? What does this say about the coefficients of friction of those systems? Is a greater force required to start the motion of an object than to keep it in motion? What does this say about static and kinetic friction? When does an object slide down at constant velocity? What does this say about friction and normal force? Inclined Plane Force Components 

This video shows how the weight of an object on an inclined plane is broken down into components perpendicular and parallel to the surface of the plane. It explains the geometry for finding the angle in more detail. 

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Normal force is represented by the variable N . N . This should not be confused with the symbol for the newton, which is also represented by the letter N. It is important to tell apart these symbols, especially since the units for normal force ( N N ) happen to be newtons (N). For example, the normal force, N N , that the floor exerts on a chair might be N = 100 N . N = 100 N . One important difference is that normal force is a vector, while the newton is simply a unit. Be careful not to confuse these letters in your calculations! 

To review, the process for solving inclined plane problems is as follows: Draw a sketch of the problem. Identify known and unknown quantities, and identify the system of interest. Draw a free-body diagram (which is a sketch showing all of the forces acting on an object) with the coordinate system rotated at the same angle as the inclined plane. Resolve the vectors into horizontal and vertical components and draw them on the free-body diagram. Write Newton s second law in the horizontal and vertical directions and add the forces acting on the object. If the object does not accelerate in a particular direction (for example, the x -direction) then F net x = 0. If the object does accelerate in that direction, F net x = m a . Check your answer. Is the answer reasonable? Are the units correct? Finding the Coefficient of Kinetic Friction on an Inclined Plane 

A skier, illustrated in [link] (a) , with a mass of 62 kg is sliding down a snowy slope at an angle of 25 degrees. Find the coefficient of kinetic friction for the skier if friction is known to be 45.0 N. Use the diagram to help find the coefficient of kinetic friction for the skier. Strategy 

The magnitude of kinetic friction was given as 45.0 N. Kinetic friction is related to the normal force N as f k = k N f k = k N . Therefore, we can find the coefficient of kinetic friction by first finding the normal force of the skier on a slope. The normal force is always perpendicular to the surface, and since there is no motion perpendicular to the surface, the normal force should equal the component of the skier s weight perpendicular to the slope. 

That is, N = w = w cos ( 25 ) = m g cos ( 25 ) N = w = w cos ( 25 ) = m g cos ( 25 ) 

Substituting this into our expression for kinetic friction, we get f k = k m g cos 25 , f k = k m g cos 25 , 

which can now be solved for the coefficient of kinetic friction k . Solution 

Solving for k k gives 

k = f k w cos 25 = f k m g cos 25 k = f k w cos 25 = f k m g cos 25 

Substituting known values on the right-hand side of the equation, 

k = 45.0 N ( 62 kg)(9 .80 m/s 2 ) ( 0.906 ) = 0.082 k = 45.0 N ( 62 kg)(9 .80 m/s 2 ) ( 0.906 ) = 0.082 Discussion 

This result is a little smaller than the coefficient listed in Table 5.1 for waxed wood on snow, but it is still reasonable since values of the coefficients of friction can vary greatly. In situations like this, where an object of mass m slides down a slope that makes an angle with the horizontal, friction is given by f k = k m g cos . f k = k m g cos . Weight on an Incline, a Two-Dimensional Problem 

The skier s mass, including equipment, is 60.0 kg. (See [link] (b) .) (a) What is her acceleration if friction is negligible? (b) What is her acceleration if the frictional force is 45.0 N? Now use the diagram to help find the skier's acceleration if friction is negligible and if the frictional force is 45.0 N. Strategy 

The most convenient coordinate system for motion on an incline is one that has one coordinate parallel to the slope and one perpendicular to the slope. (Remember that motions along perpendicular axes are independent.) We use the symbol to mean perpendicular, and | | | | to mean parallel. 

The only external forces acting on the system are the skier s weight, friction, and the normal force exerted by the ski slope, labeled w w , f f , and N N in the free-body diagram. N N is always perpendicular to the slope and f f is parallel to it. But w w is not in the direction of either axis, so we must break it down into components along the chosen axes. We define w | | w | | to be the component of weight parallel to the slope and w w the component of weight perpendicular to the slope. Once this is done, we can consider the two separate problems of forces parallel to the slope and forces perpendicular to the slope. Solution 

The magnitude of the component of the weight parallel to the slope is w | | = w sin ( 25 ) = m g sin ( 25 ) w | | = w sin ( 25 ) = m g sin ( 25 ) , and the magnitude of the component of the weight perpendicular to the slope is w = w cos ( 25 ) = m g cos ( 25 ) w = w cos ( 25 ) = m g cos ( 25 ) . 

(a) Neglecting friction: Since the acceleration is parallel to the slope, we only need to consider forces parallel to the slope. (Forces perpendicular to the slope add to zero, since there is no acceleration in that direction.) The forces parallel to the slope are the amount of the skier s weight parallel to the slope w | | w | | and friction f f . Assuming no friction, by Newton s second law the acceleration parallel to the slope is a | | = F net || m , a | | = F net || m , 

Where the net force parallel to the slope F net || = w | | = m g sin ( 25 ) F net || = w | | = m g sin ( 25 ) , so that a | | = F net || m = m g sin ( 25 ) m = g sin ( 25 ) = ( 9.80 m/s 2 ) ( 0.423 ) = 4.14 m/s 2 a | | = F net || m = m g sin ( 25 ) m = g sin ( 25 ) = ( 9.80 m/s 2 ) ( 0.423 ) = 4.14 m/s 2 

is the acceleration. 

(b) Including friction: Here we now have a given value for friction, and we know its direction is parallel to the slope and it opposes motion between surfaces in contact. So the net external force is now F net | | = w | | f , F net | | = w | | f , 

and substituting this into Newton s second law, a | | = F net || m a | | = F net || m gives a | | = F net || m = w | | f m = m g sin ( 25 ) f m . a | | = F net || m = w | | f m = m g sin ( 25 ) f m . 

We substitute known values to get a | | = (60 .0 kg)(9 .80 m/s 2 )(0 .423) 45 .0 N 60 .0 kg , a | | = (60 .0 kg)(9 .80 m/s 2 )(0 .423) 45 .0 N 60 .0 kg , 

or a | | = 3 .39 m/s 2 , a | | = 3 .39 m/s 2 , 

which is the acceleration parallel to the incline when there is 45 N opposing friction. Discussion 

Since friction always opposes motion between surfaces, the acceleration is smaller when there is friction than when there is not. Practice Problems 

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[link] Friction at an Angle: Sliding a Coin 

An object will slide down an inclined plane at a constant velocity if the net force on the object is zero. We can use this fact to measure the coefficient of kinetic friction between two objects. As shown in the first Worked Example , the kinetic friction on a slope f k = k m g cos f k = k m g cos , and the component of the weight down the slope is equal to m g sin m g sin . These forces act in opposite directions, so when they have equal magnitude, the acceleration is zero. Writing these out: f k = F g x k m g cos = m g sin . f k = F g x k m g cos = m g sin . 

Solving for k k , since tan = sin /cos tan = sin /cos we find that 

k = m g sin m g cos = tan k = m g sin m g cos = tan 1 coin 1 book 1 protractor Put a coin flat on a book and tilt it until the coin slides at a constant velocity down the book. You might need to tap the book lightly to get the coin to move. Measure the angle of tilt relative to the horizontal and find k k . 

[link] Section Summary Friction is a contact force between systems that opposes the motion or attempted motion between them. Simple friction is proportional to the normal force N pushing the systems together. (A normal force is always perpendicular to the contact surface between systems.) Friction depends on both of the materials involved. s is the coefficient of static friction, which depends on both of the materials. k is the coefficient of kinetic friction, which also depends on both materials. When objects rest on an inclined plane that makes an angle with the horizontal surface, the weight of the object can be broken into components that act perpendicular ( w w ) and parallel ( w | | w | | ) to the surface of the plane. Key Equations force of static friction f s s N f s s N force of kinetic friction f k = k N f k = k N perpendicular component of weight on an inclined plane w = w cos ( ) = m g cos ( ) w = w cos ( ) = m g cos ( ) parallel component of weight on an inclined plane w | | = w sin ( ) = m g sin ( ) w | | = w sin ( ) = m g sin ( ) Check Your Understanding 

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[link] Glossary kinetic friction a force that opposes the motion of two systems that are in contact and moving relative to one another static friction a force that opposes the motion of two systems that are in contact and are not moving relative to one anotherThe Scientific Method The Scientific Method 

By the end of this section, you will be able to: Explain how the methods of science are used to make scientific discoveries Define a scientific model and describe examples of physical and mathematical models used in physics Compare and contrast hypothesis, theory, and law 

The learning objectives in this section will help your students master the following TEKS: (2A) : Know the definition of science and understand that it has limitations, as specified in subsection (b)(2) of this section. (2B) : Know that scientific hypotheses are tentative and testable statements that must be capable of being supported or not supported by observational evidence. Hypotheses of durable explanatory power which have been tested over a wide variety of conditions are incorporated into theories. (2C) : Know that scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well-established and highly-reliable explanations, but may be subject to change as new areas of science and new technologies are developed. (2D) : Distinguish between scientific hypotheses and scientific theories. Section Key Terms experiment hypothesis model observation principle scientific law scientific method theory universal 

[OL] Pre-assessment for this section could involve students sharing or writing down an anecdote about when they used the methods of science. Then, students could label their thought processes in their anecdote with the appropriate scientific methods. The class could also discuss their definitions of theory and law, both outside and within the context of science. 

[OL] It should be noted and possibly mentioned that "a scientist," as mentioned in this section, does not necessarily mean a trained scientist. It could be anyone using methods of science. Scientific Methods 

Scientists often plan and carry out investigations to answer questions about the universe around us. Such laws are intrinsic to the universe, meaning that humans did not create them and cannot change them. We can only discover and understand them. Their discovery is a very human endeavor, with all the elements of mystery, imagination, struggle, triumph, and disappointment inherent in any creative effort. The cornerstone of discovering natural laws is observation. Science must describe the universe as it is, not as we imagine or wish it to be. 

We all are curious to some extent. We look around, make generalizations, and try to understand what we see. For example, we look up and wonder whether one type of cloud signals an oncoming storm. As we become serious about exploring nature, we become more organized and formal in collecting and analyzing data. We attempt greater precision, perform controlled experiments (if we can), and write down ideas about how data may be organized. We then formulate models, theories, and laws based on the data we have collected, and communicate those results with others. This, in a nutshell, describes the scientific method , a term used for the techniques that scientists employ to decide scientific issues on the basis of evidence from observation and experiment. 

An investigation often begins with a scientist making an observation . The scientist observes a pattern or trend within the natural world. Observation may generate questions that the scientist wishes to answer. Next, the scientist may perform some research about the topic and devise a hypothesis . A hypothesis is a testable statement that describes how something in the natural world works. In essence, a hypothesis is an educated guess that explains something about an observation. 

[OL] Educated guess is used throughout this section in describing a hypothesis to combat the tendency to think of a theory as an educated guess. 

Scientists may test the hypothesis by performing an experiment . During an experiment, the scientist collects data that will help them learn about the phenomenon they are studying. Then the scientists analyze the results of the experiment (that is, the data), often using statistical, mathematical, and/or graphical methods. From the data analysis, they draw conclusions. They may conclude that their experiment either supports or rejects their hypothesis. If the hypothesis is supported, the scientist usually goes on to test another hypothesis related to the first. If their hypothesis is rejected, they will often then test a new and different hypothesis in their effort to learn more about whatever they are studying. 

Scientific processes can be applied to many situations. Let s say that you try to turn on your car, but it will not start. You have just made an observation! You ask yourself, "Why won t my car start?" You can now use scientific processes to answer this question. First, you generate a hypothesis such as, "The car won t start because it has no gasoline in the gas tank." To test this hypothesis, you put gasoline in the car and try to start it again. If the car starts, then your hypothesis is supported by the experiment. If the car does not start, then your hypothesis is rejected. You will then need to think up a new hypothesis to test such as, "My car won t start because the fuel pump is broken." Hopefully, your experiments lead you to discover why the car won t start, and enable you to fix it. Modeling 

A model is a representation of something that is often too difficult (or impossible) to study directly. Models can take the form of physical models, equations, computer programs, or simulations computer graphics/animations. Models are tools that are especially useful in modern physics because they let us visualize phenomena that we normally cannot observe with our senses, such as very small objects or objects that move at high speeds. For example, we can understand the structure of an atom using models, despite the fact that no one has ever seen an atom with their own eyes. Models are always approximate, so they are simpler to consider than the real situation; the more complete a model is, the more complicated it must be. Models put the intangible or the extremely complex into human terms that we can visualize, discuss, and hypothesize about. 

Scientific models are constructed based on the results of previous experiments. Even still, models often only describe a phenomenon partially or in a few limited situations. Some phenomena are so complex that it may be impossible to model it in its entirety, even using computers. An example is the electron cloud model of the atom in which electrons are moving around the atom s center in distinct clouds. (See [link] ) that represent the likelihood of finding an electron in different places. This model helps us to visualize the structure of an atom. However, it does not show us exactly where an electron will be within its cloud at any one particular time. The electron cloud model of the atom predicts the geometry and shape of areas where different electrons may be found in an atom. However, it cannot indicate exactly where an electron will be at any one time. 

As mentioned previously, physicists use a variety of models including equations, physical models, computer simulations, etc. For example, three-dimensional models are often commonly used in chemistry and physics to model molecules. Properties other than appearance or location are usually modelled using mathematics, where functions are used to show how these properties relate to one another. Processes such as the formation of a star or the planets, can also be modelled using computer simulations. Once a simulation is correctly programmed based on actual experimental data, the simulation can allow us to view processes that happened in the past or happen too quickly or slowly for us to observe directly. In addition, scientists can also run virtual experiments using computer based models . In a model of planet formation, for example, the scientist could alter the amount or type of rocks present in space and see how it affects planet formation. 

Scientists use models and experimental results to construct explanations of observations or design solutions to problems. For example, one way to make a car more fuel efficient is to reduce the friction or drag caused by air flowing around the moving car. This can be done by designing the body shape of the car to be more aerodynamic, such as by using rounded corners instead of sharp ones. Engineers can then construct physical models of the car body, place them in a wind tunnel, and examine the flow of air around the model (This can also be done mathematically in a computer simulation). The air flow pattern can be analyzed for regions smooth air flow and for eddies that indicate drag. The model of the car body may have to be altered slightly to produce the smoothest pattern of air flow (i.e., the least drag). The pattern with the least drag may be the solution to increasing fuel efficiency of the car. This solution might then be incorporated into the car design. Using Models and the Scientific Processes 

Be sure to secure loose items before opening the window or door. 

In this activity, you will learn about scientific models by making a model of how air flows through your classroom or a room in your house. One room with at least 1 window or door that can be opened Piece of single-ply tissue paper Work with a group of four, as directed by your teacher. Close all of the windows and doors in the room you are working in. Your teacher may assign you a specific window or door to study. Before opening any windows or doors, draw a to-scale diagram of your room. First, measure the length and width of your room using the tape measure. Then, transform the measurement using a scale that could fit on your paper, such as 1/2 inch = 1 foot or 5 centimeters = 1 meter. Your teacher will assign you a specific window or door to study air flow. On your diagram, add arrows showing your hypothesis (before opening any windows or doors) of how air will flow through the room when your assigned window or door is opened. Use pencil so that you can easily make changes to your diagram. On you diagram, mark 4 locations where you would like to test air flow in your room. To test for airflow, hold a strip of single ply tissue paper between the thumb and index finger. Note the direction that the paper moves by when exposed to the airflow. Then, for each location, predict which way the paper will move if your air flow diagram is correct. Now, each member of your group will stand in one of the four selected areas. Each member will test the airflow Agree upon an approximate height at which everyone will hold their papers. When you teacher tells you to, open your assigned window and/or door. Each person should note the direction that their paper points immediately after the window or door was opened. Record your results on your diagram. Did the airflow test data support or refute the hypothetical model of air flow shown in your diagram? Why or why not? Correct your model based on your experimental evidence. With your group, discuss how accurate your model is. What limitations did it have? Write down the limitations that your group agreed upon. 

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This Snap Lab! has students construct a model of how air flows in their classroom. Each group of 4 students will create a model of air flow in their classroom using a scale drawing of the room. Then, the groups will test the validity of their model by placing weathervanes that they have constructed around the room and opening a window or door. By observing the weather vanes, students will see how air actually flows through the room from a specific window or door. Students will then correct their model based on their experimental evidence. The material list is given per group: One room with at least 1 window or door that can be opened (An optimal configuration would be 1 window or door per group.) several pieces of construction paper (at least 4 per group) strips of single ply tissue paper One tape measure (long enough to measure the dimensions of the room) straws scissors tape Group size can vary depending on the number of windows/doors available and the number of students in the class. The room dimensions could be provided by the teacher. Also, students may need a brief introduction in how to make a drawing to scale. This is another opportunity to discuss controlled experiments in terms of why the students should hold the strips of tissue paper at the same height and in the same way. One student could also serve as a control and stand far away from the window/door or in another area that will not receive air flow from the window/door. You will probably need to coordinate this when multiple windows or doors are used. Only one window or door should be opened at a time for best results. Between openings, allow a short period (5 minutes) when all windows and doors are closed, if possible. 

Answers to the Grasp Check will vary, but the air flow in the new window or door should be based on what the students observed in their experiment. Scientific Laws and Theories 

A scientific law is a description of a pattern in nature that is true in all circumstances that have been studied. That is, physical laws are meant to be universal , meaning that they apply throughout the known universe. Laws are often also concise, whereas theories are more complicated. A law can be expressed in the form of a single sentence or mathematical equation. For example, Newton s second law of motion , which relates the motion of an object to the force applied ( F ), the mass of the object ( m ), and the object s acceleration ( a ), is simply stated using the equation: F = m a F = m a 

Scientific ideas and explanations that are true in many, but not all situations in the universe are usually called principles . An example is Pascal s principle , which explains properties of liquids, but not solids or gases. However, the distinction between laws and principles is sometimes not carefully made in science. 

A theory is an explanation for patterns in nature that is supported by much scientific evidence and verified multiple times by multiple researchers. While many people confuse theories with educated guesses o hypotheses, theories have withstood more rigorous testing and verification than hypotheses. 

[OL] Explain to students that in informal, everyday English the word "theory" can be used to describe an idea that is possibly true but that has not been proven to be true. This use of the word "theory" often leads people to think that scientific theories are nothing more than educated guesses. This is not just a misconception among students, but among the general public as well. 

As a closing idea about scientific processes, we want to point out that scientific laws and theories, even those that have been supported by experiments for centuries, can still be changed by new discoveries. This is especially true when new technologies emerge that allow us to observe things that were formerly unobservable. Imagine how viewing previously invisible objects with a microscope or viewing Earth for the first time from space may have instantly changed our scientific theories and laws! What discoveries still await us in the future? The constant retesting and perfecting of our scientific laws and theories allows our knowledge of nature to progress. For this reason, many scientists are reluctant to say that their studies "prove" anything. By saying "support" instead of "prove," it keeps the door open for future discoveries, even if they won t occur for centuries or even millennia. 

[OL] With regard to scientists avoiding using the word "prove," the general public knows that science has proven certain things such as that the heart pumps blood and the Earth is round. However, scientists should shy away from using "prove" because it is impossible to test every single instance and every set of conditions in a system to absolutely prove anything. Using "support" or similar terminology leaves the door open for further discovery. Check Your Understanding 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which objective and direct students to the relevant content. Section Summary Science seeks to discover and describe the underlying order and simplicity in nature. The processes of science include observation, hypothesis, experiment, and conclusion. Theories are scientific explanations that are supported by a large body experimental results. Scientific laws are concise descriptions of the universe that are universally true. Concept Items 

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[link] Glossary experiment process involved with testing a hypothesis hypothesis testable statement that describes how something in the natural world works model system that is analogous to the real system of interest in essential ways but more easily analyzed observation step where a scientist observes a pattern or trend within the natural world. principle description of nature that is true in many, but not all situations scientific law pattern in nature that is true in all circumstances studied thus far scientific method the techniques and processes used in the constructing and testing of scientific hypotheses, laws, and theories, and in deciding issues on the basis of experiment and observation theory explanation of patterns in nature that is supported by much scientific evidence and verified multiple times by various groups of researchers universal applies throughout the known universeThe Language of Physics: Physical Quantities and Units The Language of Physics: Physical Quantities and Units 

By the end of this section, you will be able to: Associate physical quantities with their SI units and perform conversions among SI units using scientific notation Relate measurement uncertainty to significant figures and apply the rules for using significant figures in calculations Correctly create, label, and identify relationships in graphs using mathematical relationships (e.g.: slope, y -intercept, inverse, quadratic and logarithmic) 

The learning objectives in this section will help your students master the following TEKS: (2H) : Make measurements with accuracy and precision and record data using scientific notation and International System (SI) units. (2L) : Express and manipulate relationships among physical variables quantitatively, including the use of graphs, charts, and equations. Section Key Terms accuracy ampere constant conversion factor dependent variable derived units English units exponential relationship fundamental physical units independent variable inverse relationship inversely proportional kilogram linear relationship logarithmic (log) scale log-log plot meter method of adding percents order of magnitude precision quadratic relationship scientific notation second semi-log plot SI units significant figures slope uncertainty variable y -intercept 

[OL] Pre-assessment for this section could involve asking students what experience they have had with the four fundamental units in their daily lives. One could also poll the class for what they think accuracy, precision, and uncertainty refer to. For graphing, students could make a quick graph of some data and then edit their graph after reading to note ways they could improve the clarity of their graph. The Role of Units 

Physicists, like other scientists, make observations and ask basic questions. For example: how big is an object? How much mass does it have? How far did it travel? To answer these questions, they make measurements with various instruments (e.g., meter stick, balance, stopwatch, etc.). 

The measurements of physical quantities are expressed in terms of units, which are standardized values. For example, the length of a race, which is a physical quantity, can be expressed in meters (for sprinters) or kilometers (for distance runners.) Without standardized units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way. (See [link] ). Distances given in unknown units are maddeningly useless. 

All physical quantities in the SI system of units are expressed in terms of combinations of seven fundamental physical units, which are units for: length, mass, time, electric current, temperature, amount of a substance, and luminous intensity. SI Units: Fundamental and Derived Units 

There are two major systems of units used in the world: SI units (acronym for the French Syst me International, also known as the metric system) and English units (also known as the imperial system). English units were historically used in nations once ruled by the British Empire. Today, the United States is the only country that still uses English units extensively. Virtually every other country in the world now uses the metric system, which is the standard system agreed upon by scientists and mathematicians. 

[OL] As a clarification, certain countries use the British system for a few of their measurements. For example, Britain still uses the pint to measure beer, miles to measure road distances, and pounds to measure body weight (although weight must be reported in kg in British medical records). The British people still use the British system extensively in their everyday lives, but the metric system is the official standard for the government. Likewise, many oil-producing countries measure oil in British gallons. 

Some physical quantities are more fundamental than others. In physics, there are seven fundamental physical quantities (which are measured in base units , or fundamental physical units): length, mass, time, electric current, temperature, amount of a substance, and luminous intensity. Units for other physical quantities (such as force, speed, and electric charge) described by mathematically combining these 7 base units. In this course, we will mainly use five of these: length, mass, time, electric current and temperature. The units in which they are measured are the meter, kilogram, second, ampere, kelvin, mole, and candela ( [link] ). All other units are made by mathematically combining the fundamental units. These are called derived units . SI Base Unit Quantity Name Symbol length meter m mass kilogram kg time second s electric current ampere a temperature kelvin k amount of substance mole mol luminous intensity candela cd The Meter 

The SI unit for length is the meter (abbreviated as m). The definition of the meter has changed over time to become more accurate and precise. The meter was first defined in 1791 as 1/10,000,000 of the distance from the equator to the North Pole. This measurement was improved in 1889 by redefining the meter to be the distance between two engraved lines on a platinum-iridium bar. (The bar is now housed at the International Bureau of Weights and Meaures, near Paris). By 1960, some distances could be measured more precisely by comparing them to wavelengths of light. The meter was redefined as 1,650,763.73 wavelengths of orange light emitted by krypton atoms. In 1983, the meter was given its present definition as the distance light travels in a vacuum in 1/ 299,792,458 of a second. (See [link] ). The meter is defined to be the distance light travels in 1/299,792,458 of a second through a vacuum. Distance traveled is speed multiplied by time. The Kilogram 

The SI unit for mass is the kilogram (abbreviated as kg). It is defined to be the mass of a platinum-iridium cylinder, housed at the International Bureau of Weights and Measures near Paris. Exact replicas of the standard kilogram cylinder are kept in numerous locations throughout the world, such as the National Institute of Standards and Technology in Gaithersburg, Maryland. The determination of all other masses can be done by comparing them with one of these standard kilograms. The Second 

The SI unit for time, the second (abbreviated as s) also has a long history. For many years it was defined as 1/86,400 of an average solar day. However, the average solar day is actually very gradually getting longer due to gradual slowing of Earth s rotation. Accuracy in the fundamental units is essential, since all other measurements are derived from them. Therefore, a new standard was adopted to define the second in terms of a non-varying, or constant, physical phenomenon. One constant phenomenon is the very steady vibration of Cesium atoms, which can be observed and counted. This vibration forms the basis of the cesium atomic clock . In 1967, the second was redefined as the time required for 9,192,631,770 Cesium atom vibrations. (See [link] .) An atomic clock such as this one uses the vibrations of cesium atoms to keep time to a precision of one microsecond per year. The fundamental unit of time, the second, is based on such clocks. This image is looking down from the top of an atomic clock. (credit: Steve Jurvetson/Flickr) 

[BL] An average solar day was used to originally define the second because the length of a solar day varies throughout the year due to Earth s tilt of its axis as well as its elliptical orbit. The accumulation of these variations could result in a day length difference of up to 16 minutes during different seasons. Using an average solar day resolves these variations in day length. The Ampere 

Electric current is measured in the ampere (named for Andre Ampere and abbreviated A). You have probably heard of amperes, or "amps," when people discuss electrical currents or electrical devices. Understanding an ampere requires a basic understanding of electricity and magnetism, something that will be explored in depth in later chapters of this book. Basically, two parallel wires with an electric current running through them will produce an attractive force on each other. One ampere is defined as the amount of electric current that will produce an attractive force of 2.7 10 7 newton per meter of separation between the two wires (the newton is the derived unit of force). 

[BL] Some students may not know that a vacuum is a region of space that contains no air. Kelvins 

The SI unit of temperature is the kelvin (or kelvins, but not degrees kelvin). This scale is named after physicist William Thomson, Lord Kelvin, who was the first to call for an absolute temperature scale. The Kelvin scale is based on absolute zero. This is the point at which all thermal energy has been removed from all atoms or molecules in a system. This temperature, 0 K, is equal to 273.15 C and 459.67 F. Conveniently, the Kelvin scale actually changes in the same way as the Celsius scale. For example, the freezing point (0 C) and boiling points of water (100 C) are 100 degrees apart on the Celsius scale. These two temperatures are also 100 kelvins apart (freezing point = 273.15 K; boiling point = 373.15 K). Metric Prefixes 

Physical objects or phenomena may vary widely. For example, the size of objects varies from something very small (like an atom) to something very large (like a star). Yet the standard metric unit of length is the meter. So, the metric system includes many prefixes that can be attached to a unit. Each prefix is based on factors of 10 (10, 100, 1000, etc. as well as 0.1, 0.01, 0.001, etc.). [link] gives the metric prefixes and symbols used to denote the different various factors of 10 in the metric system. 

The metric system is convenient because conversions between metric units can be done simply by moving the decimal place of a number. This is because the metric prefixes are sequential powers of 10. There are 100 centimeters in a meter, 1000 meters in a kilometer, and so on. In nonmetric systems, such as U.S. customary units , the relationships are less simple there are 12 inches in a foot, 5280 feet in a mile, 4 quarts in a gallon, and so on. Another advantage of the metric system is that the same unit can be used over extremely large ranges of values simply by switching to the most-appropriate metric prefix. For example, distances in meters are suitable for building construction, but kilometers are used to describe road construction. Therefore, with the metric system, there is no need to invent new units when measuring very small or very large objects you just have to move the decimal point (and use the appropriate prefix). Prefix Symbol Value[1] Example (some are approximate) exa E 10 18 exameter Em 10 18 m distance light travels in a century peta P 10 15 petasecond Ps 10 15 s 30 million years tera T 10 12 terawatt TW 10 12 W powerful laser output giga G 10 9 gigahertz GHz 10 9 Hz a microwave frequency mega M 10 6 megacurie MCi 10 6 Ci high radioactivity kilo k 10 3 kilometer km 10 3 m about 6/10 mile hector h 10 2 hectoliter hL 10 2 L 26 gallons deka da 10 1 dekagram dag 10 1 g teaspoon of butter ____ ____ 10 0 (=1) deci d 10 1 deciliter dL 10 1 L less than half a soda centi c 10 2 centimeter Cm 10 2 m fingertip thickness mili m 10 3 millimeter Mm 10 3 m flea at its shoulder micro 10 6 micrometer m 10 6 m detail in microscope nano n 10 9 nanogram Ng 10 9 g small speck of dust pico p 10 12 picofarad pF 10 12 F small capacitor in radio femto f 10 15 femtometer Fm 10 15 m size of a proton atto a 10 18 attosecond as 10 18 s time light takes to cross an atom Known Ranges of Length, Mass, and Time 

[link] lists known lengths, masses, and time measurements. You can see that scientists use a range of measurement units. This wide range demonstrates the vastness and complexity of the universe, as well as the breadth of phenomena physicists study. As you examine this table, note how the metric system allows us to discuss and compare an enormous range of phenomena, using one system of measurement. (See [link] and [link] .) Approximate Values of Length, Mass, and Time Lengths in meters Masses in kilogram (more precise values in parentheses) Times in seconds (more precise values in parentheses) 10 18 Present experimental limit to smallest observable detail 10 30 Mass of an electron (9.11 10 31 kg) 10 23 Time for light to cross an proton 10 15 Diameter of a proton 10 27 Mass of a hydrogen atom (1.67 10 27 kg) 10 22 Mean life of an extremely unstable nucleus 10 14 Diameter of a uranium nucleus 10 15 Mass of a bacterium 10 15 Time for one oscillation of a visible light 10 10 Diameter of a hydrogen atom 10 5 Mass of a mosquito 10 13 Time for one vibration of an atom in a solid 10 8 Thickness of membranes in cell of living organism 10 2 Mass of a hummingbird 10 8 Time for one oscillation of an FM radio wave 10 6 Wavelength of visible light 1 Mass of a liter of water (about a quart) 10 3 Duration of a nerve impulse 10 3 Size of a grain of sand 10 2 Mass of a person 1 Time for one heartbeat 1 Height of a 4 year-old child 10 3 Mass of a car 10 5 One day (8.64 10 4 s) 10 2 Length of a football field 10 8 Mass of a large ship 10 7 One year (y) (3.16 10 7 s) 10 4 Greatest ocean depth 10 12 Mass of a large iceberg 10 9 About half the life expectancy of a human 10 7 Diameter of the Earth 10 15 Mass of the nucleus of a comet 10 11 Recorded history 10 11 Distance from the Earth to the Sun 10 23 Mass of the Moon (7.35 10 22 kg) 10 17 Age of the Earth 10 16 Distance traveled by light in 1 year (a light year) 10 25 Mass of Earth (5.97 10 24 kg) 10 18 Age of the universe 10 21 Diameter of the Milky Way galaxy 10 30 Mass of the Sun (1.99 10 24 kg) 10 22 Distance from Earth to the nearest large galaxy (Andromeda) 10 42 Mass of the Milky Way galaxy (current upper limit) 10 26 Distance from the Earth to the edges of the known universe 10 53 Mass of the known universe (current upper limit) Tiny phytoplankton float among crystals of ice in the Antarctic Sea. They range from a few micrometers to as much as 2 millimeters in length. (credit: Prof. Gordon T. Taylor, Stony Brook University; NOAA Corps Collections) Galaxies collide 2.4 billion light years away from Earth. The tremendous range of observable phenomena in nature challenges the imagination. (credit: NASA/CXC/UVic./A. Mahdavi et al. Optical/lensing: CFHT/UVic./H. Hoekstra et al.) Using Scientific Notation with Physical Measurements 

Scientific notation is a way of writing numbers that are too large or small to be conveniently written as a decimal. For example, consider the number 840,000,000,000,000. It s a rather large number to write out. The scientific notation for this number is 8.40 10 14 . Scientific notation follows this general format: x 10 y x 10 y 

In this format x is the value of the measurement with all placeholder zeros removed. In the example above, x is 8.4. The x is multiplied by a factor, 10 y , which indicates the number of placeholder zeros in the measurement. Placeholder zeros are those at the end of a number that is 10 or greater, and at the beginning of a decimal number that is less than 1. In the example above, the factor is 10 14 . This tells you that you should move the decimal point 14 positions to the right, filling in placeholder zeros as you go. In this case, moving the decimal point 14 places creates only 13 placeholder zeros, indicating that the actual measurement value is 840,000,000,000,000. 

Numbers that are fractions can be indicated by scientific notation as well. Consider the number 0.0000045. Its scientific notation is 4.5 10 6 . Its scientific notation has the same format: x 10 y x 10 y 

Here, x is 4.5. However, the value of y in the 10 y factor is negative, which indicates that the measurement is a fraction of 1. Therefore, we move the decimal place to the left, for a negative y . In our example of 4.5 10 6 , the decimal point would be moved to the left six times to yield the original number, which would be 0.0000045. 

The term order of magnitude refers to the power of 10 when numbers are expressed in scientific notation. Quantities that have the same power of 10 when expressed in scientific notation, or come close to it, are said to be of the same order of magnitude. For example, the number 800 can be written as 8 10 2 , and the number 450 can be written as 4.5 10 2 . Both numbers have the same value for y . Therefore, 800 and 450 are of the same order of magnitude. Similarly, 101 and 99 would be regarded as the same order of magnitude, 10 2 . Order of magnitude can be thought of as a ballpark estimate for the scale of a value. The diameter of an atom is on the order of 10 9 m, while the diameter of the sun is on the order of 10 9 m. These two values are 18 orders of magnitude apart. 

Scientists make frequent use of scientific notation because of the vast range of physical measurements possible in the universe, such as the distance from Earth to the Moon, seen in [link] , or to the nearest star. The distance from Earth to the Moon may seem immense, but it is just a tiny fraction of the distance from Earth to our closest neighboring star. (credit: NASA) Unit Conversion and Dimensional Analysis 

It is often necessary to convert from one type of unit to another. For example, if you are reading a European cookbook in the United States, some quantities may be expressed in liters and you need to convert them to cups. A Canadian tourist driving through the United States might want to convert miles to kilometers, to have a sense of how far away his next destination is. A doctor in the United States might convert a patient s weight in pounds to kilograms. 

Let s consider a simple example of how to convert units within the metric system. How can we want to convert 1 hour to seconds? 

Next, we need to determine a conversion factor relating meters to kilometers. A conversion factor is a ratio expressing how many of one unit are equal to another unit. A conversion factor is simply a fraction which equals 1. You can multiply any number by 1 and get the same value. When you multiply a number by a conversion factor, you are simply multiplying it by one. For example, the following are conversion factors: (1 foot)/(12 inches) = 1 to convert inches to feet, (1 meter)/(100 centimeters) = 1 to convert centimeters to meters, (1 minute)/(60 seconds) = 1 to convert seconds to minutes. In this case, we know that there are 1,000 meters in 1 kilometer. 

Now we can set up our unit conversion. We will write the units that we have and then multiply them by the conversion factor (1 km/1000m) = 1, so we are simply multiplying 80 m by "1: 1 h 60 min 1 h 60 s 1 min = 3600 s = 3 .6 10 2 s 1 h 60 min 1 h 60 s 1 min = 3600 s = 3 .6 10 2 s 

When there is a unit in the original number, and a unit in the denominator (bottom) of the conversion factor, the units cancel. In this case, hours and minutes cancel and the value in seconds remains. 

You can use this method to convert between any types of unit, including between the U.S. customary system and metric system. Notice also that, although you can multiply and divide units algebraically, you cannot add or subtract different units. An expression like 10 km + 5 kg makes no sense. Even adding two lengths in different units, such as 10 km + 20 m does not make sense. You express both lengths in the same unit. See Appendix C for a more complete list of conversion factors. Unit Conversions: A Short Drive Home 

Suppose that you drive the 10.0 km from your university to home in 20.0 min. Calculate your average speed (a) in kilometers per hour (km/h) and (b) in meters per second (m/s). (Note: Average speed is distance traveled divided by time of travel.) Strategy 

First we calculate the average speed using the given units. Then we can get the average speed into the desired units by picking the correct conversion factor and multiplying by it. The correct conversion factor is the one that cancels the unwanted unit and leaves the desired unit in its place. Solution for (a) 

Calculate average speed. Average speed is distance traveled divided by time of travel. (Take this definition as a given for now average speed and other motion concepts will be covered in a later module.) In equation form, average speed = distance time average speed = distance time 

Substitute the given values for distance and time. average speed = 10.0 km 20.0 min = 0.500 km min average speed = 10.0 km 20.0 min = 0.500 km min 

Convert km/min to km/h: multiply by the conversion factor that will cancel minutes and leave hours. That conversion factor is 60 min/1 h 60 min/1 h . Thus, average speed = 0.500 km min 60 min 1 h = 30.0 km h . average speed = 0.500 km min 60 min 1 h = 30.0 km h . Discussion for (a) 

To check your answer, consider the following: 

Be sure that you have properly cancelled the units in the unit conversion. If you have written the unit conversion factor upside down, the units will not cancel properly in the equation. If you accidentally get the ratio upside down, then the units will not cancel; rather, they will give you the wrong units as follows: km min 1 hr 60 min = 1 60 km h min 2 km min 1 hr 60 min = 1 60 km h min 2 

which are obviously not the desired units of km/h. Check that the units of the final answer are the desired units. The problem asked us to solve for average speed in units of km/h and we have indeed obtained these units. Check the significant figures. Because each of the values given in the problem has three significant figures, the answer should also have three significant figures. The answer 30.0 km/h does indeed have three significant figures, so this is appropriate. Note that the significant figures in the conversion factor are not relevant because an hour is defined to be 60 minutes, so the precision of the conversion factor is perfect. Next, check whether the answer is reasonable. Let us consider some information from the problem if you travel 10 km in a third of an hour (20 min), you would travel three times that far in an hour. The answer does seem reasonable. Solution (b) 

There are several ways to convert the average speed into meters per second. Start with the answer to (a) and convert km/h to m/s. Two conversion factors are needed one to convert hours to seconds, and another to convert kilometers to meters. 

Multiplying by these yields Average speed = 30.0 km h 1 h 3,600 s 1 , 000 m 1 km Average speed = 30.0 km h 1 h 3,600 s 1 , 000 m 1 km Average speed = 8.33 m s Average speed = 8.33 m s Discussion for (b) 

If we had started with 0.500 km/min, we would have needed different conversion factors, but the answer would have been the same: 8.33 m/s. 

You may have noted that the answers in the worked example just covered were given to three digits. Why? When do you need to be concerned about the number of digits in something you calculate? Why not write down all the digits your calculator produces? Accuracy, Precision and Significant Figures 

Science is based on experimentation that requires good measurements. The validity of a measurement can be described in terms of its accuracy and its precision (see [link] and [link] ). Accuracy is how close a measurement is to the correct value for that measurement. For example, let us say that you are measuring the length of standard piece of printer paper. The packaging in which you purchased the paper states that it is 11 inches long, and suppose this stated value is correct. You measure the length of the paper three times and obtain the following measurements: 11.1 in., 11.2 in., and 10.9 in. These measurements are quite accurate because they are very close to the correct value of 11.0 inches. In contrast, if you had obtained a measurement of 12 inches, your measurement would not be very accurate. This is why measuring instruments are calibrated based on a known measurement. If the instrument consistently returns the correct value of the known measurement, it is safe for use in finding unknown values. A double-pan mechanical balance is used to compare different masses. Usually an object with unknown mass is placed in one pan and objects of known mass are placed in the other pan. When the bar that connects the two pans is horizontal, then the masses in both pans are equal. The known masses are typically metal cylinders of standard mass such as 1 gram, 10 grams, and 100 grams. (credit: Serge Melki) Whereas a mechanical balance may only read the mass of an object to the nearest tenth of a gram, some digital scales can measure the mass of an object up to the nearest thousandth of a gram. As in other measuring devices, the precision of a scale is limited to the last measured figures. This is the hundredths place in the scale pictured here. (credit: Splarka, Wikimedia Commons) 

Precision states how well repeated measurements of something generate the same or similar results. Therefore, the precision of measurements refers to how close together the measurements are when you measure the same thing several times. One way to analyze the precision of measurements would be to determine the range, or difference between the lowest and the highest measured values. In the case of the printer paper measurements, the lowest value was 10.9 in. and the highest value was 11.2 in. Thus, the measured values deviated from each other by, at most, 0.3 in. These measurements were reasonably precise because they varied by only a fraction of an inch. However, if the measured values had been 10.9 in., 11.1 in., and 11.9 in., then the measurements would not be very precise because there is a lot of variation from one measurement to another. 

The measurements in the paper example are both accurate and precise, but in some cases, measurements are accurate but not precise, or they are precise but not accurate. Let us consider a GPS system that is attempting to locate the position of a restaurant in a city. Think of the restaurant location as existing at the center of a bull s-eye target. Then think of each GPS attempt to locate the restaurant as a black dot on the bull s eye. 

In [link] , you can see that the GPS measurements are spread far apart from each other, but they are all relatively close to the actual location of the restaurant at the center of the target. This indicates a low precision, high accuracy measuring system. However, in [link] , the GPS measurements are concentrated quite closely to one another, but they are far away from the target location. This indicates a high precision, low accuracy measuring system. Finally, in [link] , the GPS is both precise and accurate, allowing the restaurant to be located. A GPS system attempts to locate a restaurant at the center of the bull s-eye. The black dots represent each attempt to pinpoint the location of the restaurant. The dots are spread out quite far apart from one another, indicating low precision, but they are each rather close to the actual location of the restaurant, indicating high accuracy. (credit: Dark Evil) In this figure, the dots are concentrated close to one another, indicating high precision, but they are rather far away from the actual location of the restaurant, indicating low accuracy. (credit: Dark Evil) In this figure, the dots are concentrated close to one another, indicating high precision, but they are rather far away from the actual location of the restaurant, indicating low accuracy. (credit: Dark Evil) Uncertainty 

The accuracy and precision of a measuring system determine the uncertainty of its measurements. Uncertainty is a way to describe how much your measured value deviates from the actual value that the object has. If your measurements are not very accurate or precise, then the uncertainty of your values will be very high. In more general terms, uncertainty can be thought of as a disclaimer for your measured values. For example, if someone asked you to provide the mileage on your car, you might say that it is 45,000 miles, plus or minus 500 miles. The plus or minus amount is the uncertainty in your value. That is, you are indicating that the actual mileage of your car might be as low as 44,500 miles or as high as 45,500 miles, or anywhere in between. All measurements contain some amount of uncertainty. In our example of measuring the length of the paper, we might say that the length of the paper is 11 in. plus or minus 0.2 in or 11 in. 0.2 in. The uncertainty in a measurement, A , is often denoted as A ("delta A "), 

The factors contributing to uncertainty in a measurement include: Limitations of the measuring device The skill of the person making the measurement Irregularities in the object being measured Any other factors that affect the outcome (highly dependent on the situation) 

In the printer paper example, uncertainty could be caused by 1) the fact that the smallest division on the ruler is 0.1 in., 2) the person using the ruler has bad eyesight, or 3) uncertainty caused by the paper cutting machine (e.g. one side of the paper is slightly longer than the other). It is good practice to carefully consider all possible sources of uncertainty in a measurement and reduce or eliminate them, if possible. Percent Uncertainty 

One method of expressing uncertainty is as a percent of the measured value. If a measurement, A , is expressed with uncertainty, A , the percent uncertainty is: % uncertainty = A A 100 % % uncertainty = A A 100 % Calculating Percent Uncertainty: A Bag of Apples 

A grocery store sells 5-lb bags of apples. You purchase four bags over the course of a month and weigh the apples each time. You obtain the following measurements: Week 1 weight: 4. 8 lb 4. 8 lb Week 2 weight: 5.3 lb 5.3 lb Week 3 weight: 4. 9 lb 4. 9 lb Week 4 weight: 5.4 lb 5.4 lb 

You determine that the weight of the 5 lb bag has an uncertainty of 0.4 lb. What is the percent uncertainty of the bag s weight? Strategy 

First, observe that the expected value of the bag s weight, A A , is 5 lb. The uncertainty in this value, A A , is 0.4 lb. We can use the following equation to determine the percent uncertainty of the weight: % uncertainty = A A 100 % % uncertainty = A A 100 % Solution 

Plug the known values into the equation: % uncertainty = 0.4 lb 5 lb 100 % = 8 % . % uncertainty = 0.4 lb 5 lb 100 % = 8 % . Discussion 

We can conclude that the weight of the apple bag is 5 lb 8%. Consider how this percent uncertainty would change if the bag of apples were half as heavy, but the uncertainty in the weight remained the same. Hint for future calculations: when calculating percent uncertainty, always remember that you must multiply the fraction by 100%. If you do not do this, you will have a decimal quantity, not a percent value. Uncertainty in Calculations 

There is an uncertainty in anything calculated from measured quantities. For example, the area of a floor calculated from measurements of its length and width has an uncertainty because the both the length and width have uncertainties. How big is the uncertainty in something you calculate by multiplication or division? If the measurements in the calculation have small uncertainties (a few percent or less), then the method of adding percents can be used. This method says that the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation. For example, if a floor has a length of 4.00 m and a width of 3.00 m, with uncertainties of 2% and 1%, respectively, then the area of the floor is 12.0 m 2 and has an uncertainty of 3% (expressed as an area this is 0.36 m 2 , which we round to 0.4 m 2 since the area of the floor is given to a tenth of a square meter). 

For a quick demonstration of the accuracy, precision, and uncertainty of measurements based upon the units of measurement, try this simulation . You will have the opportunity to measure the length and weight of a desk, using milli- versus centi- units. Which do you think will provide greater accuracy, precision and uncertainty when measuring the desk and the notepad in the simulation? Consider how the nature of the hypothesis or research question might influence how precise of a measuring tool you need to collect data. Precision of Measuring Tools and Significant Figures 

An important factor in the accuracy and precision of measurements is the precision of the measuring tool. In general, a precise measuring tool is one that can measure values in very small increments. For example, consider measuring the thickness of a coin. A standard ruler can measure thickness to the nearest millimeter, while a micrometer can measure the thickness to the nearest 0.005 millimeter. The micrometer is a more precise measuring tool because it can measure extremely small differences in thickness. The more precise the measuring tool, the more precise and accurate the measurements can be. 

When we express measured values, we can only list as many digits as we initially measured with our measuring tool (such as the rulers shown in [link] ). For example, if you use a standard ruler to measure the length of a stick, you may measure it with a decimeter ruler as 3.6 cm. You could not express this value as 3.65 cm because your measuring tool was not precise enough to measure a hundredth of a centimeter. It should be noted that the last digit in a measured value has been estimated in some way by the person performing the measurement. For example, the person measuring the length of a stick with a ruler notices that the stick length seems to be somewhere in between 36 mm and 37 mm. He or she must estimate the value of the last digit. The rule is that the last digit written down in a measurement is the first digit with some uncertainty. For example, the last measured value 36.5 mm has three digits, or three significant figures. The number of significant figures in a measurement indicates the precision of the measuring tool. The more precise a measuring tool is, the greater the number of significant figures it can report. Three metric rulers are shown. The first ruler is in decimeters and can measure point three decimeters. The second ruler is in centimeters long and can measure three point six centimeters. The last ruler is in millimeters and can measure thirty-six point five millimeters. Zeros 

Special consideration is given to zeros when counting significant figures. For example, the zeros in 0.053 are not significant because they are only placeholders that locate the decimal point. There are two significant figures in 0.053 the 5 and the 3. However, if the zero occurs between other significant figures, the zeros are significant. For example, both zeros in 10.053 are significant, as these zeros were actually measured. Therefore, the 10.053 placeholder has five significant figures. The zeros in 1300 may or may not be significant, depending on the style of writing numbers. They could mean the number is known to the last zero, or the zeros could be placeholders. So 1300 could have two, three, or four significant figures. To avoid this ambiguity, write 1300 in scientific notation as 1.3 10 3 . Only significant figures are given in the x factor for a number in scientific notation (in the form x 10 y x 10 y ). Therefore, we know that 1 and 3 are the only significant digits in this number. In summary, zeros are significant except when they serve only as placeholders. [link] provides examples of the number of significant figures in various numbers. Number Significant figures Rationale 1.657 4 There are no zeros and all non-zero numbers are always significant. 0.4578 4 The first zero is only a placeholder for the decimal point. 0.000458 3 The first four zeros are placeholders needed to report the data to the ten-thoudsandths place. 2000.56 6 The three zeros are significant here because they occur between other significant figures. 45,600 3 With no underlines or scientific notation, we assume that the last two zeros are placeholders and are not significant. 15895 00 0 7 The two underlined zeros are significant, while the last zero is not, as it is not underlined. 5.457 10 13 4 In scientific notation, all numbers reported in front of the multiplication sign are significant 6.520 10 23 4 In scientific notation, all numbers reported in front of the multiplication sign are significant, including zeros. Significant Figures in Calculations 

When combining measurements with different degrees of accuracy and precision, the number of significant digits in the final answer can be no greater than the number of significant digits in the least precise measured value. There are two different rules, one for multiplication and division and another rule for addition and subtraction, as discussed below. 

For multiplication and division: The answer should have the same number of significant figures as the starting value with the fewest significant figures. For example, the area of a circle can be calculated from its radius using A = r 2 A = r 2 . Let us see how many significant figures the area will have if the radius has only two significant figures, for example, r = 2.0 m. Then, using a calculator that keeps eight significant figures, you would get A = r 2 = ( 3.1415927... ) ( 2.0 m ) 2 = 4.5238934 m 2 . A = r 2 = ( 3.1415927... ) ( 2.0 m ) 2 = 4.5238934 m 2 . 

But because the radius has only two significant figures, the area calculated is meaningful only to two significant figures or A = 4.5 m 2 A = 4.5 m 2 

even though the value of is meaningful to at least eight digits. 

For addition and subtraction : The answer should have the same number places (e.g. tens place, ones place, tenths place, etc.) as the least-precise starting value. Suppose that you buy 7.56 kg of potatoes in a grocery store as measured with a scale having a precision of 0.01 kg. Then you drop off 6.052 kg of potatoes at your laboratory as measured by a scale with a precision of 0.001 kg. Finally, you go home and add 13.7 kg of potatoes as measured by a bathroom scale with a precision of 0.1 kg. How many kilograms of potatoes do you now have, and how many significant figures are appropriate in the answer? The mass is found by simple addition and subtraction: 



7.56 kg 6.052 kg + 13.7 kg _ 15.208 kg 7.56 kg 6.052 kg + 13.7 kg _ 15.208 kg 

The least precise measurement is 13.7 kg. This measurement is expressed to the 0.1 decimal place, so our final answer must also be expressed to the 0.1 decimal place. Thus, the answer should be rounded to the tenths place, giving 15.2 kg. The same is true for non-decimal numbers. For example: 6527.23 + 2 = 6528.23 = 6528 6527.23 + 2 = 6528.23 = 6528 

We cannot report the decimal places in the answer because "2" has no decimal places that would be significant. Therefore, we can only report to the ones place. 

It is a good idea to keep extra significant figures while calculating, and to round off to the correct number of significant figures only in the final answers. The reason is that small errors from rounding while calculating can sometimes produce significant errors in the final answer. As an example, try calculating 5098 ( 5.000 ) ( 1010 ) 5098 ( 5.000 ) ( 1010 ) to obtain a final answer to only two significant figures. Keeping all significant during the calculation gives 48. Rounding to two significant figures in the middle of the calculation changes it to 5100 ( 5.000 ) ( 1000 ) = 100 5100 ( 5.000 ) ( 1000 ) = 100 , which is way off. You would similarly avoid rounding in the middle of the calculation in counting and in doing accounting, where many small numbers need to be added and subtracted accurately to give possibly much larger final numbers. 

Remind students that they will be expected to report the proper number of significant figures on assignment and test problems. Significant Figures in this Text 

In this textbook, most numbers are assumed to have three significant figures. Furthermore, consistent numbers of significant figures are used in all worked examples. You will note that an answer given to three digits is based on input good to at least three digits. If the input has fewer significant figures, the answer will also have fewer significant figures. Care is also taken that the number of significant figures is reasonable for the situation posed. In some topics, such as optics, more than three significant figures will be used. Finally, if a number is exact, such as the "2" in the formula, c = 2 r c = 2 r , it does not affect the number of significant figures in a calculation. Approximating Vast Numbers: a Trillion Dollars 

The U.S. federal deficit in the 2008 fiscal year was a little greater than $10 trillion. Most of us do not have any concept of how much even one trillion actually is. Suppose that you were given a trillion dollars in $100 bills. If you made 100-bill stacks, like that shown in [link] , and used them to evenly cover a football field (between the end zones), make an approximation of how high the money pile would become. (We will use feet/inches rather than meters here because football fields are measured in yards.) One of your friends says 3 in., while another says 10 ft. What do you think? A bank stack contains one hundred $100 bills, and is worth $10,000. How many bank stacks make up a trillion dollars? (Credit: Andrew Magill) Strategy 

When you imagine the situation, you probably envision thousands of small stacks of 100 wrapped $100 bills, such as you might see in movies or at a bank. Since this is an easy-to-approximate quantity, let us start there. We can find the volume of a stack of 100 bills, find out how many stacks make up one trillion dollars, and then set this volume equal to the area of the football field multiplied by the unknown height. Solution Calculate the volume of a stack of 100 bills. The dimensions of a single bill are approximately 3 in. by 6 in. A stack of 100 of these is about 0.5 in. thick. So the total volume of a stack of 100 bills is: volume of stack = length width height, volume of stack = 6 in . 3 in . 0 .5 in ., volume of stack = 9 in . 3 . volume of stack = length width height, volume of stack = 6 in . 3 in . 0 .5 in ., volume of stack = 9 in . 3 . 

Calculate the number of stacks. Note that a trillion dollars is equal to $ 1 10 12 $ 1 10 12 , and a stack of one-hundred $ 100 $ 100 bills is equal to $ 10 , 000 , $ 10 , 000 , or $ 1 10 4 $ 1 10 4 . The number of stacks you will have is: 

$ 1 10 12 $ 1 10 12 (a trillion dollars) / $ 1 10 4 $ 1 10 4 per stack = 1 10 8 1 10 8 stacks. 

Calculate the area of a football field in square inches. The area of a football field is 100 yd 50 yd 100 yd 50 yd , which gives 5 , 000 yd 2 5 , 000 yd 2 . Because we are working in inches, we need to convert square yards to square inches: 



Area = 5,000 yd 2 3 ft 1yd 3 ft 1yd 12 in . 1 foot 12 in . 1 foot = 6 , 480 , 000 in . 2 , Area 6 10 6 in . 2 . Area = 5,000 yd 2 3 ft 1yd 3 ft 1yd 12 in . 1 foot 12 in . 1 foot = 6 , 480 , 000 in . 2 , Area 6 10 6 in . 2 . 

This conversion gives us 6 10 6 in . 2 6 10 6 in . 2 for the area of the field. (Note that we are using only one significant figure in these calculations.) Calculate the total volume of the bills. The volume of all the $ 100 $ 100 -bill stacks is 9 in . 3 / stack 10 8 stacks = 9 10 8 in . 3 9 in . 3 / stack 10 8 stacks = 9 10 8 in . 3 . Calculate the height. To determine the height of the bills, use the equation: volume of bills = area of field height of money: Height of money = volume of bills area of field Height of money = 9 10 8 in . 3 6 10 6 in . 2 = 1.33 10 2 in . Height of money 1 10 2 in . = 100 in . volume of bills = area of field height of money: Height of money = volume of bills area of field Height of money = 9 10 8 in . 3 6 10 6 in . 2 = 1.33 10 2 in . Height of money 1 10 2 in . = 100 in . 

The height of the money will be about 100 in. high. Converting this value to feet gives 100 in . 1ft 12 in . = 8.33 ft 8 ft . 100 in . 1ft 12 in . = 8.33 ft 8 ft . Discussion 

The final approximate value is much higher than the early estimate of 3 in., but the other early estimate of 10 ft (120 in.) was roughly correct. How did the approximation measure up to your first guess? What can this exercise tell you in terms of rough "guesstimates" versus carefully calculated approximations? 

In the example above, the final approximate value is much higher than the first friend s early estimate of 3 in. However, the other friend s early estimate of 10 ft. (120 in.) was roughly correct. How did the approximation measure up to your first guess? What can this exercise suggest about the value of rough "guesstimates" versus carefully calculated approximations? 

In [link] , point out to students the importance of precision in their measurements. Greater precision allows measurements to be less uncertain, and therefore, a close approximation rather than a "guesstimate." Graphing in Physics 

Most results in science are presented in scientific journal articles using graphs. Graphs present data in a way that is easy to visualize for humans in general, especially someone unfamiliar with what is being studied. They are also useful for presenting large amounts of data or data with complicated trends in an easily-readable way. 

One commonly-used graph in physics and other sciences is the line graph , probably because it is the best graph for showing how one quantity changes in response to the other. Let s build a line graph based on the data in [link] , which shows the measured distance that a train travels from its station versus time. Our two variables , or things that change along the graph, are time in minutes, and distance from the station, in kilometers. Remember that measured data may not have perfect accuracy. Time (min) Distance from Station (km) 0 0 10 24 20 36 30 60 40 84 50 97 60 116 70 140 Draw the two axes. The horizontal axis, or x -axis, shows the independent variable , which is the variable that is controlled or manipulated. The vertical axis, or y -axis, shows the dependent variable , the non-manipulated variable that changes with (or is dependent on) the value of the independent variable. In the data above, time is the independent variable and should be plotted on the x -axis. Distance from the station is the dependent variable and should be plotted on the y -axis. Label each axes on the graph with the name of each variable, followed by the symbol for its units in parentheses. Be sure to leave room so that you can number each axis. In this example, use "Time (min)" as the label for the x -axis. 

Next, you must determine the best scale to use for numbering each axis. Because the time values on the x -axis are taken every 10 minutes, we could easily number the x -axis from 0 to 70 minutes with a tick mark every 10 minutes. Likewise, the y -axis scale should start low enough and continue high enough to include all of the "distance from station" values. A scale from 0 km to 160 km should suffice, perhaps with a tick mark every 10 km. 

In general, you want to pick a scale for both axes that 1) shows all of your data, and 2) makes it easy to identify trends in your data. If you make your scale too large, it will be harder to see how your data change. Likewise, the smaller and more fine you make your scale, the more space you will need to make the graph. The number of significant figures in the axis values should be coarser than the number of significant figures in the measurements. Now that your axes are ready, you can begin plotting your data. For the first data point, count along the x -axis until you find the 10 min tick mark. Then, count up from that point to the 10 km tick mark on the y -axis, and approximate where 22 km is along the y -axis. Place a dot at this location. Repeat for the other six data points ( [link] ). Add a title to the top of the graph to state what the graph is describing, such as the y -axis parameter vs. the x -axis parameter. In the graph shown here, the title is "train motion." It could also be titled distance of the train from the station vs. time. The graph of the train s distance from the station versus time from the exercise above. Finally, with data points now on the graph, you should draw a trend line ( [link] ). The trend line represents the dependence you think the graph represents, so that the person who looks at your graph can see how close it is to the real data. In the present case, since the data points look like they ought to fall on a straight line, you would draw a straight line as the trend line. Draw it to come closest to all the points. Real data may have some inaccuracies, and the plotted points may not all fall on the trend line. In some cases, none of the data points fall exactly on the trend line. The completed graph with the trend line included. 

[OL] The importance of bar graphs should also be mentioned as a useful way to show data relations when one variable is not continuous, such as in a frequency histogram, which compares how many data points fall into discrete categories. 

[OL] If students have difficulty understanding the difference between dependent and independent variables in the train example, explain that time is independent because it will continue to move forward at the same rate whether the train leaves the station or not. Analyzing a Graph Using Its Equation 

One way to get a quick snapshot of a dataset is to look at the equation of its trend line . If the graph produces a straight line, the equation of the trend line takes the form: y = m x + b y = m x + b 

The b in the equation is the y -intercept while the m in the equation is the slope . The y -intercept tells you at what y value the line intersects the y -axis. In the case of the graph above, the y -intercept occurs at 0, at the very beginning of the graph. The y -intercept, therefore, lets you know immediately where on the y -axis the plot line begins. 

The m in the equation is the slope. This value describes how much the line on the graph moves up or down on the y -axis along the line s length. The slope is found using the following equation: m = Y 2 Y 1 X 2 X 1 m = Y 2 Y 1 X 2 X 1 

In order to solve this equation, you need to pick two points on the line (preferably far apart on the line so the slope you calculate describes the line accurately). The quantities Y 2 and Y 1 represent the y -values from the two points on the line (not data points) that you picked, while X 2 and X 1 represent the two x -values of the those points. 

What can the slope value tell you about the graph? The slope of a perfectly horizontal line will equal 0, while the slope of a perfectly vertical line will be undefined because you cannot divide by 0. A positive slope indicates that the line moves up the y -axis as the x -value increases while a negative slope means that the line moves down the y -axis. The more negative or positive the slope is, the steeper the line moves up or down, respectively. The slope of our graph in [link] is calculated below based on the two endpoints of the line: 



m = Y 2 Y 1 X 2 X 1 m = ( 80 km ) ( 20 km ) ( 40 min ) ( 10 min ) m = 60 km 30 min m = 2.0 km/min m = Y 2 Y 1 X 2 X 1 m = ( 80 km ) ( 20 km ) ( 40 min ) ( 10 min ) m = 60 km 30 min m = 2.0 km/min 

Equation of line: y = ( 2.0 km/min ) x + 0 y = ( 2.0 km/min ) x + 0 

Because the x axis is time in minutes, we would actually be more likely to use the time t as the independent ( x- axis) variable and write the equation as y = ( 2.0 km/min ) t + 0. y = ( 2.0 km/min ) t + 0. 

The formula y = m x + b y = m x + b only applies to linear relationships , or ones that produce a straight line. Another common type of line in physics is the quadratic relationship , which occurs when one of the variables is squared. One quadratic relationship in physics is the relation between the speed of an object its centripetal acceleration, which is used to determine the force needed to keep an object moving in a circle. Another common relationship in physics is the inverse relationship , in which one variable decreases whenever the other variable increases. An example in physics is Coulomb s law. As the distance between two charged objects increases, the electrical force between the two charged objects decreases. Inverse proportionality , such the relation between x and y in the equation y = k / x y = k / x 

for some number k , is one particular kind of inverse relationship. A third commonly-seen relationship is the exponential relationship , in which a change in the independent variable produces a proportional change in the dependent variable. As the value of the dependent variable gets larger, its rate of growth also increases. For example, bacteria often reproduce at an exponential rate when grown under ideal conditions. As each generation passes, there are more and more bacteria to reproduce. As a result, the growth rate of the bacterial population increases every generation. ( [link] ). Examples of (a) linear, (b) quadratic, (c) inverse, and (d) exponential relationship graphs. Using Logarithmic Scales in Graphing 

Sometimes a variable can have a very large range of values. This presents a problem when you re trying to figure out the best scale to use for your graph s axes. One option is to use a logarithmic (log) scale . In a logarithmic scale, the value each mark labels is the previous mark s value multiplied by some constant. For a log base 10 scale, each mark labels a value that is 10 times the value of the mark before it. Therefore, a base 10 logarithmic scale would be numbered: 0, 10, 100, 1000, etc. You can see how the logarithmic scale covers a much larger range of values than the corresponding linear scale, in which the marks would label the values 0, 10, 20, 30, and so on. 

If you use a logarithmic scale on one axis of the graph and a linear scale on the other axis, you are using a semi-log plot . The Richter scale, which measures the strength of earthquakes, uses a semi-log plot. The degree of ground movement is plotted on a logarithmic scale against the assigned intensity level of the earthquake, which ranges linearly from 1-10 (see [link] (a) ). 

If a graph has both axes in a logarithmic scale, then it is referred to as a log-log plot . The relationship between the wavelength and frequency of electromagnetic radiation such as light is usually shown as a log-log plot (see [link] (b) ). Log-log plots are also commonly used to describe exponential functions, such as radioactive decay. (a) The Richter scale uses a log base 10 scale on its y-axis (microns of amplified maximum ground motion). (b) The relationship between the frequency and wavelength of electromagnetic radiation can be plotted as a straight line if a log-log plot is used. Graphing Lines 

In this simulation you will examine how changing the slope and y-intercept of an equation changes the appearance of a plotted line. Select slope-intercept form and drag the blue circles along the line to change the line s characteristics. Then, play the line game and see if you can determine the slope or y-intercept of a given line. Click here for the simulation 

[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess students achievement of the sections learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which and direct students to the relevant content. Section Summary Physical quantities are a characteristic or property of an object that can be measured or calculated from other measurements. The four fundamental units we will use in this textbook are the meter (for length), the kilogram (for mass), the second (for time), and the ampere (for electric current). These units are part of the metric system, which uses powers of 10 to relate quantities over the vast ranges encountered in nature. Unit conversions involve changing a value expressed in one type of unit to another type of unit. This is done by using conversion factors, which are ratios relating equal quantities of different units. Accuracy of a measured value refers to how close a measurement is to the correct value. The uncertainty in a measurement is an estimate of the amount by which the measurement result may differ from this value. Precision of measured values refers to how close the agreement is between repeated measurements. Significant figures express the precision of a measuring tool. When multiplying or dividing measured values, the final answer can contain only as many significant figures as the least precise value. When adding or subtracting measured values, the final answer cannot contain more decimal places than the least precise value. Key Equations Slope intercept form y = m x + b y = m x + b Quadratic formula y = a x 2 + b x + c y = a x 2 + b x + c Positive exponential formula y = a x y = a x Negative exponential formula y = a x y = a x Concept Items 

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[link] Performance Task Create a new system of units to describe something that interests you. Your unit should be described using at least two subunits. For example, you can decide to measure the quality of songs using a new unit called song awesomeness. Song awesomeness is measured by: 1) the number of song downloads and 2) the number of times the song was used in movies. Create an equation that shows how to calculate your unit. Then, using your equation, create a sample dataset that you could graph. Are your two subunits related linearly, quadratically or inversely? Test Prep Multiple Choice 

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[link] Glossary accuracy how close a measurement is to the correct value for that measurement ampere the SI unit for electrical current constant a quantity that does not change conversion factor a ratio expressing how many of one unit are equal to another unit dependent variable the vertical, or y -axis, variable, which changes with (or is dependent on) the value of the independent variable derived units units that are derived by combining the fundamental physical units English units (also known as the customary or imperial system) system of measurement used in the United States; includes units of measurement such as feet, gallons, degrees Fahrenheit, and pounds exponential relationship relation between variables in which a constant change in the independent variable is accompanied by change in the dependent variable that is proportional to the value it already had fundamental physical units the seven fundamental physical units in the SI system of units are length, mass, time, electric current, temperature, amount of a substance, and luminous intensity. independent variable the horizontal, or x -axis, variable, which is not influence by the second variable on the graph, the dependent variable inverse proportionality a relation between two variables expressible by an equation of the form y = k / x y = k / x where k stays constant when x and y change; the special form of inverse relationship that satisfies this equation inverse relationship any relation between variables where one variable decreases as the other variable increases kilogram the SI unit for mass (abbreviated kg) linear relationships relation between variables that produce a straight line when graphed logarithmic scale a graphing scale in which each tick on an axis is the previous tick multiplied by some value. log-log plot a plot that uses a logarithmic scale in both axes meter the SI unit for length, abbreviated (m) method of adding percents calculating the percent uncertainty of a quantity in multiplication or division by adding the percent uncertainties in the quantities being added or divided order of magnitude the size of a quantity in terms of its power of 10 when expressed in scientific notation precision how well repeated measurements generate the same or closely similar results quadratic relationship relation between variables that can be expressed in the form y = a x 2 + b x + c y = a x 2 + b x + c , which produces a curved line when graphed scientific notation way of writing numbers that are too large or small to be conveniently written in simple decimal form; the measurement is multiplied by a power of 10, which indicates the number of placeholder zeros in the measurement second the SI unit for time, abbreviated (s) semi-log plot A plot that uses a logarithmic scale on one axis of the graph and a linear scale on the other axis. standard international (SI) units (also known as the metric system) the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams significant figures when writing a number, the digits, or number of digits, that express the precision of a measuring tool used to measure the number slope the ratio of the change of a graph on the y axis to the change along the x- axis, the value of m in the equation of a line, y = m x + b y = m x + b uncertainty a quantitative measure of how much measured values deviate from a standard or expected value y -intercept the point where a plot line intersects the y-axisIntroduction Introduction In this chapter you will learn about: Vector Addition and Subtraction: Graphical Methods Vector Addition and Subtraction: Analytical Methods Projectile Motion Inclined Planes Simple Harmonic Motion class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" 

Physics learning objectives come from 112.39 (c) Knowledge and Skills Billiard balls on a pool table are in motion after being hit with a cue stick. (credit: Popperipopp, Wikimedia Commons) 

Point out to the students that most motion is in two or three dimensions and can be described in a similar fashion to one-dimensional motion. This chapter is about motion in two dimensions. Motion in two dimensions can be analyzed using vectors. We will first learn the practical skills of adding and subtracting vectors graphically (in drawings) and analytically (with math). Once we re able to work with two-dimensional vectors, we can then apply these skills to problems of projectile motion, inclined planes, and harmonic motion. 

In Chapter 2, we learned to distinguish between vectors and scalars; the difference being that a vector has magnitude and direction, whereas a scalar has only magnitude. We learned how to deal with vectors in physics by working straightforward one-dimensional vector problems, which may be treated mathematically in the same as scalars. In this chapter, we ll use vectors to expand our understanding of forces and motion into two dimensions. Most real-world physics problems (such as with the game of pool pictured here) are, after all, either two- or three-dimensional problems and physics is most useful when applied to real physical scenarios. We start by learning the practical skills of graphically adding and subtracting vectors (by using drawings) and analytically (with math). Once we re able to work with two-dimensional vectors, we apply these skills to problems of projectile motion, inclined planes, and harmonic motion. 

Before students begin this chapter, review the concepts of displacement, velocity, acceleration, vectors, representing vectors, free-body diagrams.Simple Harmonic Motion Simple Harmonic Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe Hooke s law and Simple Harmonic Motion Describe periodic motion, oscillations, amplitude, frequency, and period Solve problems in simple harmonic motion involving springs and pendulums 

The learning objectives in this section will help your students master the following TEKS: (7) Science concepts. The student knows the characteristics and behavior of waves. The student is expected to: (7A) : examine and describe oscillatory motion and wave propagation in various types of media Section Key Terms amplitude deformation equilibrium position frequency Hooke s law oscillate period periodic motion restoring force simple harmonic motion simple pendulum Hooke s Law and Simple Harmonic Motion 

Imagine a car parked against a wall. If a bulldozer pushes the car into the wall, the car will not move but it will noticeably change shape. A change in shape due to the application of a force is a deformation . Even very small forces are known to cause some deformation. For small deformations, two important things can happen. First, unlike the car and bulldozer example, the object returns to its original shape when the force is removed. Second, the size of the deformation is proportional to the force. This second property is known as Hooke s law . In equation form, Hooke s law is F = k x F = k x 

where x is the amount of deformation (the change in length, for example) produced by the restoring force F , and k is a constant that depends on the shape and composition of the object. The restoring force is the force that brings the object back to its equilibrium position; the minus sign is there because the restoring force acts in the direction opposite to the displacement. Note that the restoring force is proportional to the deformation x . The deformation can also be thought of as a displacement from equilibrium. It is a change in position due to a force. In the absence of force, the object would rest at its equilibrium position. The force constant k is related to the stiffness of a system. The larger the force constant, the stiffer the system. A stiffer system is more difficult to deform and requires a greater restoring force. The units of k are newtons per meter (N/m). One of the most common uses of Hooke s law is solving problems involving springs and pendulums, which we will cover at the end of this section. 

[BL] Review the concept of force. 

[BL] [OL] [AL] Introduce Hooke s law and force constant of a spring. Oscillations and Periodic Motion 

What do an ocean buoy, a child in a swing, a guitar, and the beating of hearts all have in common? They all oscillate . That is, they move back and forth between two points, like the ruler illustrated in [link] . All oscillations involve force. For example, you push a child in a swing to get the motion started. A ruler is displaced from its equilibrium position. 

[BL] [OL] [AL] Find springs or rubber bands with different amounts of stiffness. Ask students to attach weights to these to construct oscillators. Introduce the terms frequency and time period. Ask students to observe how the stiffness of the spring affects them. How does mass of the system affect them? How does the initial force applied affect them? 

Newton s first law implies that an object oscillating back and forth is experiencing forces. Without force, the object would move in a straight line at a constant speed rather than oscillate. Consider, for example, plucking a plastic ruler to the left as shown in [link] . The deformation of the ruler creates a force in the opposite direction, known as a restoring force . Once released, the restoring force causes the ruler to move back toward its stable equilibrium position, where the net force on it is zero. However, by the time the ruler gets there, it gains momentum and continues to move to the right, producing the opposite deformation. It is then forced to the left, back through equilibrium, and the process is repeated until it gradually loses all of its energy. The simplest oscillations occur when the restoring force is directly proportional to displacement. Recall that Hooke s law describes this situation with the equation F = kx . Therefore, Hooke s law describes and applies to the simplest case of oscillation, known as simple harmonic motion . (a) The plastic ruler has been released, and the restoring force is returning the ruler to its equilibrium position. (b) The net force is zero at the equilibrium position, but the ruler has momentum and continues to move to the right. (c) The restoring force is in the opposite direction. It stops the ruler and moves it back toward equilibrium again. (d) Now the ruler has momentum to the left. (e) In the absence of damping (caused by frictional forces), the ruler reaches its original position. From there, the motion will repeat itself. 

When you pluck a guitar string, the resulting sound has a steady tone and lasts a long time. Each vibration of the string takes the same time as the previous one. Periodic motion is a motion that repeats itself at regular time intervals, such as with an object bobbing up and down on a spring or a pendulum swinging back and forth. The time to complete one oscillation (a complete cycle of motion) remains constant and is called the period T . Its units are usually seconds. 

Frequency f is the number of oscillations per unit time. The SI unit for frequency is the hertz (Hz), defined as the number of oscillations per second. The relationship between frequency and period is f = 1 / T f = 1 / T 

As you can see from the equation, frequency and period are different ways of expressing the same concept. For example, if you get a paycheck twice a month, you could say that the frequency of payment is two per month, or that the period between checks is half a month. 

If there is no friction to slow it down, then an object in simple motion will oscillate forever with equal displacement on either side of the equilibrium position. The equilibrium position is where the object would naturally rest in the absence of force. The maximum displacement from equilibrium is called the amplitude X . The units for amplitude and displacement are the same, but depend on the type of oscillation. For the object on the spring, shown in [link] , the units of amplitude and displacement are meters. An object attached to a spring sliding on a frictionless surface is a simple harmonic oscillator. When displaced from equilibrium, the object performs simple harmonic motion that has an amplitude X and a period T . The object s maximum speed occurs as it passes through equilibrium. The stiffer the spring is, the smaller the period T . The greater the mass of the object is, the greater the period T . 

The mass m and the force constant k are the only factors that affect the period and frequency of simple harmonic motion. The period of a simple harmonic oscillator is given by T = 2 m k T = 2 m k 

and, because f = 1/ T , the frequency of a simple harmonic oscillator is f = 1 2 k m f = 1 2 k m Introduction to Harmonic Motion 

This video shows how to graph the displacement of a spring in the x-direction over time, based on the period. Watch the first ten minutes of the video (you can stop when the narrator begins to cover calculus). 

[link] Solving Spring and Pendulum Problems with Simple Harmonic Motion 

Before solving problems with springs and pendulums, it is important to first get an understanding of how a pendulum works. [link] provides a useful illustration of a simple pendulum. A simple pendulum has a small-diameter bob and a string that has a very small mass but is strong enough not to stretch. The linear displacement from equilibrium is s, the length of the arc. Also shown are the forces on the bob, which result in a net force of mg sin toward the equilibrium position that is, a restoring force. 

[BL] Review simple harmonic motion. 

Everyday examples of pendulums include old-fashioned clocks, a child s swing, or the sinker on a fishing line. For small displacements of less than 15 degrees, a pendulum experiences simple harmonic oscillation, meaning that its restoring force is directly proportional to its displacement. A pendulum in simple harmonic motion is called a simple pendulum . A pendulum has an object with a small mass, also known as the pendulum bob, which hangs from a light wire or string. The equilibrium position for a pendulum is where the angle is zero (that is, when the pendulum is hanging straight down). It makes sense that without any force applied, this is where the pendulum bob would rest. 

[BL] [OL] [AL] Construct simple pendulums of different lengths. Ask students to measure their time periods or frequencies. Are they constant for a given pendulum? How does the mass impact the frequency? How does the initial displacement affect it? What happens if a small push is given to the pendulum to get it started? Does that change the frequency? In what way does the length affect the frequency? 

The displacement of the pendulum bob is the arc length s . The weight m g has components m g cos along the string and m g sin tangent to the arc. Tension in the string exactly cancels the component m g cos parallel to the string. This leaves a net restoring force back toward the equilibrium position that runs tangent to the arc and equals m g sin . 

For a simple pendulum, The period is T = 2 L g . T = 2 L g . 

The only things that affect the period of a simple pendulum are its length and the acceleration due to gravity. The period is completely independent of other factors, such as mass or amplitude. However, note that T does depend on g . This means that if we know the length of a pendulum, we can actually use it to measure gravity! This will come in useful in [link] . 

Tension is represented by the variable T , and period is represented by the variable T . It is important not to confuse the two, since tension is a force and period is a length of time. Measuring Acceleration due to Gravity: The Period of a Pendulum 

What is the acceleration due to gravity in a region where a simple pendulum having a length 75.000 cm has a period of 1.7357 s? Strategy 

We are asked to find g given the period T and the length L of a pendulum. We can solve T = 2 L g T = 2 L g for g , assuming that the angle of deflection is less than 15 degrees. Recall that when the angle of deflection is less than 15 degrees, the pendulum is considered to be in simple harmonic motion, allowing us to use this equation. Solution Square T = 2 L g T = 2 L g and solve for g : g = 4 2 L T 2 g = 4 2 L T 2 Substitute known values into the new equation: g = 4 2 0.75000 m ( 1.7357 s ) 2 g = 4 2 0.75000 m ( 1.7357 s ) 2 Calculate to find g : g = 9.8281 m / s 2 . g = 9.8281 m / s 2 . Discussion 

This method for determining g can be very accurate. This is why length and period are given to five digits in this example. Hooke s Law: How Stiff Are Car Springs? 

What is the force constant for the suspension system of a car, like that shown in [link] , that settles 1.20 cm when an 80.0-kg person gets in? A car in a parking lot. (credit: exfordy, Flickr) Strategy 

Consider the car to be in its equilibrium position x = 0 before the person gets in. The car then settles down 1.20 cm, which means it is displaced to a position x = 1.20 10 2 m. 

At that point, the springs supply a restoring force F equal to the person s weight 

w = m g = (80.0 kg)(9.80 m/s 2 ) = 784 N. We take this force to be F in Hooke s law. 

Knowing F and x , we can then solve for the force constant k . Solution 

Solve Hooke s law, F = kx , for k : k = F x k = F x 

Substitute known values and solve for k : k = 784 N 1.20 10 2 m = 6.53 10 4 N/m k = 784 N 1.20 10 2 m = 6.53 10 4 N/m Discussion 

Note that F and x have opposite signs because they are in opposite directions the restoring force is up, and the displacement is down. Also, note that the car would oscillate up and down when the person got in, if it were not for the shock absorbers. Bouncing cars are a sure sign of bad shock absorbers. Practice Problems 

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Use a simple pendulum to find the acceleration due to gravity g in your home or classroom. 1 string 1 stopwatch 1 small dense object Cut a piece of a string or dental floss so that it is about 1 m long. Attach a small object of high density to the end of the string (for example, a metal nut or a car key). Starting at an angle of less than 10 degrees, allow the pendulum to swing and measure the pendulum s period for 10 oscillations using a stopwatch. Calculate g . 

[link] Section Summary An oscillation is a back and forth motion of an object between two points of deformation. An oscillation may create a wave, which is a disturbance that propagates from where it was created. The simplest type of oscillations are related to systems that can be described by Hooke s law Periodic motion is a repetitious oscillation. The time for one oscillation is the period T The number of oscillations per unit time is the frequency A mass m suspended by a wire of length L is a simple pendulum and undergoes simple harmonic motion for amplitudes less than about 15 degrees. Key Equations Hooke s law F = k x F = k x period in simple harmonic motion T = 2 m k T = 2 m k frequency in simple harmonic motion f = 1 2 k m f = 1 2 k m period of a simple pendulum T = 2 L g T = 2 L g Check Your Understanding 

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[AL] Ask two students to demonstrate pushing a table from two different directions. Ask students what they feel the direction of resultant motion will be. How would they represent this graphically? Recall that a vector s magnitude is represented by the length of the arrow. Demonstrate the head-to-tail method of adding vectors, using the example given in the chapter. Ask students to practice this method of addition using a scale and a protractor. 

[BL] [OL] [AL] Ask students if anything changes by moving the vector from one place to another on a graph. How about the order of addition? Would that make a difference? Introduce negative of a vector and vector subtraction. 

Construct a seconds pendulum (pendulum with time period 2 seconds). Test Prep Multiple Choice 

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[link] Glossary amplitude the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position deformation displacement from equilibrium, or change in shape due to the application of force equilibrium position where an object would naturally rest in the absence of force frequency number of events per unit of time Hooke s law proportional relationship between the force F on a material and the deformation L L it causes, F = k L F = k L oscillate moving back and forth regularly between two points period time it takes to complete one oscillation periodic motion motion that repeats itself at regular time intervals restoring force force acting in opposition to the force caused by a deformation simple harmonic motion the oscillatory motion in a system where the net force can be described by Hooke s law simple pendulum an object with a small mass suspended from a light wire or stringProjectile Motion Projectile Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe the properties of projectile motion Apply kinematic equations and vectors to solve problems involving projectile motion 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in two dimensions for a variety of situations. The student is expected to: (4C) : analyze and describe accelerated motion in two dimensions using equations Section Key Terms air resistance maximum height (of a projectile) projectile projectile motion range trajectory Properties of Projectile Motion 

Projectile motion is the motion of an object thrown (projected) into the air. After the initial force that launches the object, it only experiences the force of gravity. The object is called a projectile , and its path is called its trajectory . As an object travels through the air, it encounters a frictional force that slows its motion called air resistance . Air resistance does significantly alter trajectory motion, but due to the difficulty in calculation, it is ignored in introductory physics. 

[BL] [OL] Review addition of vectors graphically and analytically. 

[BL] [OL] [AL] Explain the term projectile motion . Ask students to guess what the motion of a projectile might depend on? Is the initial velocity important? Is the angle important? How will these things affect its height and the distance it covers? Introduce the concept of air resistance. Review kinematic equations. 

The most important concept in projectile motion is that horizontal and vertical motions are independent , meaning that they don t influence one another. [link] compares a cannonball in free fall (in blue) to a cannonball launched horizontally in projectile motion (in red). You can see that the cannonball in free fall falls at the same rate as the cannonball in projectile motion. Keep in mind that if the cannon launched the ball with any vertical component to the velocity, the vertical displacements would not line up perfectly. 

Since vertical and horizontal motions are independent, we can analyze them separately, along perpendicular axes. To do this, we separate projectile motion into the two components of its motion, one along the horizontal axis and the other along the vertical. The diagram shows the projectile motion of a cannonball shot at a horizontal angle versus one dropped with no horizontal velocity. Note that both cannonballs have the same vertical position over time. 

We ll call the horizontal axis the x -axis and the vertical axis the y -axis. For notation, d is the total displacement, and x and y are its components along the horizontal and vertical axes. The magnitudes of these vectors are x and y , as illustrated in [link] . A boy kicks a ball at angle , and it is displaced a distance of s along its trajectory. 

As usual, we use velocity, acceleration, and displacement to describe motion. We must also find the components of these variables along the x - and y -axes. The components of acceleration are then very simple: a y = g = 9.80 m/s 2 . (Note that this definition defines the upwards direction as positive). Because gravity is vertical, a x = 0. Both accelerations are constant, so we can use the kinematic equations. For review, the kinematic equations from a previous chapter are summarized in [link] . Summary of Kinematic Equations (constant a) x = x 0 + v a v g t x = x 0 + v a v g t (when a = 0 a = 0 ) v a v g = v 0 + v 2 v a v g = v 0 + v 2 (when a = 0 a = 0 ) v = v 0 + a t v = v 0 + a t x = x 0 + v 0 t + 1 2 a t 2 x = x 0 + v 0 t + 1 2 a t 2 v 2 = v 0 2 + 2 a ( x x 0 ) v 2 = v 0 2 + 2 a ( x x 0 ) 

Where x is position, x 0 is initial position, v is velocity, v avg is average velocity, t is time and a is acceleration. Solve Problems Involving Projectile Motion 

The following steps are used to analyze projectile motion: Separate the motion into horizontal and vertical components along the x- and y-axes. These axes are perpendicular, so A x = A cos A x = A cos and A y = A sin A y = A sin are used. The magnitudes of the displacement s s along x- and y-axes are called x x and y . y . The magnitudes of the components of the velocity v v are v x = v cos v x = v cos and v y = v sin v y = v sin , where v v is the magnitude of the velocity and is its direction. Initial values are denoted with a subscript 0. Treat the motion as two independent one-dimensional motions, one horizontal and the other vertical. The kinematic equations for horizontal and vertical motion take the following forms: Horizontal Motion ( a x = 0 ) x = x 0 + v x t v x = v 0 x = v x = velocity is a constant Horizontal Motion ( a x = 0 ) x = x 0 + v x t v x = v 0 x = v x = velocity is a constant Vertical motion (assuming positive is up a y = g = 9.80 m/s 2 a y = g = 9.80 m/s 2 ) y = y 0 + 1 2 ( v 0 y + v y ) t v y = v 0 y g t y = y 0 + v 0 y t 1 2 g t 2 v y 2 = v 0 y 2 2 g ( y y 0 ) y = y 0 + 1 2 ( v 0 y + v y ) t v y = v 0 y g t y = y 0 + v 0 y t 1 2 g t 2 v y 2 = v 0 y 2 2 g ( y y 0 ) Solve for the unknowns in the two separate motions (one horizontal and one vertical). Note that the only common variable between the motions is time t t . The problem solving procedures here are the same as for one-dimensional kinematics. Recombine the two motions to find the total displacement s s and velocity v v . We can use the analytical method of vector addition, which uses A = A x 2 + A y 2 A = A x 2 + A y 2 and = tan 1 ( A y / A x ) = tan 1 ( A y / A x ) to find the magnitude and direction of the total displacement and velocity. Displacement: d = x 2 + y 2 = tan 1 ( y / x ) Velocity: v = v x 2 + v y 2 v = tan 1 ( v y / v x ) Displacement: d = x 2 + y 2 = tan 1 ( y / x ) Velocity: v = v x 2 + v y 2 v = tan 1 ( v y / v x ) is the direction of the displacement d d , and v v is the direction of the velocity v v . (See [link] (a) We analyze two-dimensional projectile motion by breaking it into two independent one-dimensional motions along the vertical and horizontal axes. (b) The horizontal motion is simple, because a x = 0 a x = 0 and v x v x is thus constant. (c) The velocity in the vertical direction begins to decrease as the object rises; at its highest point, the vertical velocity is zero. As the object falls towards the Earth again, the vertical velocity increases again in magnitude but points in the opposite direction to the initial vertical velocity. (d) The x - and y -motions are recombined to give the total velocity at any given point on the trajectory. 

Demonstrate the path of a projectile by doing a simple demonstration. Toss a dark beanbag in front of a white board so that students can get a good look at the projectile path. Vary the toss angles, so different paths can be displayed. This demonstration could be extended by using digital photography. Draw a reference grid on the whiteboard , then toss the bag at different angles while taking a video. Replay this in slow motion to observe and compare the altitudes and trajectories. 

For problems of projectile motion, it is important to set up a coordinate system. The first step is to choose an initial position for x x and y y . Usually, it is simplest to set the initial position of the object so that x 0 = 0 x 0 = 0 and y 0 = 0 y 0 = 0 . Projectile at an Angle 

This video presents an example of finding the displacement (or range) of a projectile launched at an angle. It also reviews basic trigonometry for finding the sine, cosine and tangent of an angle. 

[link] A Fireworks Projectile Explodes High and Away 

During a fireworks display like the one illustrated in [link] , a shell is shot into the air with an initial speed of 70.0 m/s at an angle of 75 above the horizontal. The fuse is timed to ignite the shell just as it reaches its highest point above the ground. (a) Calculate the height at which the shell explodes. (b) How much time passed between the launch of the shell and the explosion? (c) What is the horizontal displacement of the shell when it explodes? The diagram shows the trajectory of a fireworks shell. Strategy 

The motion can be broken into horizontal and vertical motions in which a x = 0 a x = 0 and a y = g a y = g . We can then define x 0 x 0 and y 0 y 0 to be zero and solve for the maximum height . Solution for (a) 

By height we mean the altitude or vertical position y y above the starting point. The highest point in any trajectory, the maximum height, is reached when v y = 0 v y = 0 ; this is the moment when the vertical velocity switches from positive (upwards) to negative (downwards). Since we know the initial velocity, initial position, and the value of v y when the firework reaches its maximum height, we use the following equation to find y y : v y 2 = v 0 y 2 2 g ( y y 0 ) . v y 2 = v 0 y 2 2 g ( y y 0 ) . 

Because y 0 y 0 and v y v y are both zero, the equation simplifies to 0 = v 0 y 2 2 g y . 0 = v 0 y 2 2 g y . 

Solving for y y gives y = v 0 y 2 2 g . y = v 0 y 2 2 g . 

Now we must find v 0 y v 0 y , the component of the initial velocity in the y -direction. It is given by v 0 y = v 0 sin v 0 y = v 0 sin , where v 0 y v 0 y is the initial velocity of 70.0 m/s, and = 75 = 75 is the initial angle. Thus, v 0 y = v 0 sin 0 = ( 70.0 m/s ) ( sin 75 ) = 67.6 m/s v 0 y = v 0 sin 0 = ( 70.0 m/s ) ( sin 75 ) = 67.6 m/s 

and y y is y = ( 67.6 m/s ) 2 2 ( 9.80 m/s 2 ) , y = ( 67.6 m/s ) 2 2 ( 9.80 m/s 2 ) , 

so that y = 233 m . y = 233 m . Discussion for (a) 

Since up is positive, the initial velocity and maximum height are positive, but the acceleration due to gravity is negative. The maximum height depends only on the vertical component of the initial velocity. The numbers in this example are reasonable for large fireworks displays, the shells of which do reach such heights before exploding. Solution for (b) 

There is more than one way to solve for the time to the highest point. In this case, the easiest method is to use y = y 0 + 1 2 ( v 0 y + v y ) t y = y 0 + 1 2 ( v 0 y + v y ) t . Because y 0 y 0 is zero, this equation reduces to y = 1 2 ( v 0 y + v y ) t y = 1 2 ( v 0 y + v y ) t 

Note that the final vertical velocity, v y v y , at the highest point is zero. Therefore, t = 2 y ( v 0 y + v y ) = 2 ( 233 m) ( 67.6 m/s ) = 6.90 s t = 2 y ( v 0 y + v y ) = 2 ( 233 m) ( 67.6 m/s ) = 6.90 s Discussion for (b) 

This time is also reasonable for large fireworks. When you are able to see the launch of fireworks, you will notice several seconds pass before the shell explodes. (Another way of finding the time is by using y = y 0 + v 0 y t 1 2 g t 2 y = y 0 + v 0 y t 1 2 g t 2 , and solving the quadratic equation for t t .) Solution for (c) 

Because air resistance is negligible, a x = 0 a x = 0 and the horizontal velocity is constant. The horizontal displacement is horizontal velocity multiplied by time as given by x = x 0 + v x t x = x 0 + v x t , where x 0 x 0 is equal to zero: x = v x t , x = v x t , 

where v x v x is the x -component of the velocity, which is given by v x = v 0 cos 0 . v x = v 0 cos 0 . Now, v x = v 0 cos 0 = ( 70.0 m/s ) ( cos 75 ) = 18.1 m/s . v x = v 0 cos 0 = ( 70.0 m/s ) ( cos 75 ) = 18.1 m/s . 

The time t t for both motions is the same, and so x x is x = ( 18.1 m/s ) ( 6.90 s ) = 125 m x = ( 18.1 m/s ) ( 6.90 s ) = 125 m Discussion for (c) 

The horizontal motion is a constant velocity in the absence of air resistance. The horizontal displacement found here could be useful in keeping the fireworks fragments from falling on spectators. Once the shell explodes, air resistance has a major effect, and many fragments will land directly below, while some of the fragments may now have a velocity in the x direction due to the forces of the explosion. 

[BL] [OL] [AL] Talk about the sample problem. Discuss the variables or unknowns in each part of the problem Ask students which kinematic equations may be best suited to solve the different parts of the problem. 

The expression we found for y y while solving part (a) of the previous problem works for any projectile motion problem where air resistance is negligible. Call the maximum height y = h y = h ; then, h = v 0 y 2 2 g . h = v 0 y 2 2 g . 

This equation defines the maximum height of a projectile . The maximum height depends only on the vertical component of the initial velocity. Calculating Projectile Motion: Hot Rock Projectile 

Suppose a large rock is ejected from a volcano, as illustrated in [link] , with a speed of 25.0 m / s 25.0 m / s and at an angle 3 5 3 5 above the horizontal. The rock strikes the side of the volcano at an altitude 20.0 m lower than its starting point. (a) Calculate the time it takes the rock to follow this path. The diagram shows the projectile motion of a large rock from a volcano. Strategy 

Breaking this two-dimensional motion into two independent one-dimensional motions will allow us to solve for the time. The time a projectile is in the air depends only on its vertical motion. Solution 

While the rock is in the air, it rises and then falls to a final position 20.0 m lower than its starting altitude. We can find the time for this by using y = y 0 + v 0 y t 1 2 g t 2 y = y 0 + v 0 y t 1 2 g t 2 

If we take the initial position y 0 y 0 to be zero, then the final position is y = 20.0 m . y = 20.0 m . Now the initial vertical velocity is the vertical component of the initial velocity, found from 

v 0 y = v 0 sin 0 = ( 25.0 m/s ) ( sin 35 ) = 14.3 m/s . v 0 y = v 0 sin 0 = ( 25.0 m/s ) ( sin 35 ) = 14.3 m/s . 

Substituting known values yields 20.0 m = ( 14.3 m/s) t ( 4.90 m/s 2 ) t 2 20.0 m = ( 14.3 m/s) t ( 4.90 m/s 2 ) t 2 

Rearranging terms gives a quadratic equation in t t : ( 4.90 m/s 2 ) t 2 ( 14 .3 m/s ) t ( 20.0 m ) = 0 ( 4.90 m/s 2 ) t 2 ( 14 .3 m/s ) t ( 20.0 m ) = 0 

This expression is a quadratic equation of the form a t 2 + b t + c = 0 a t 2 + b t + c = 0 , where the constants are a = 4.90, b = 14.3, and c = 20.0. Its solutions are given by the quadratic formula: t = b b 2 4 a c 2 a t = b b 2 4 a c 2 a 

This equation yields two solutions: t = 3.96 and t = 1.03. (You may verify these solutions as an exercise). The time is t = 3.96 s or 1.03 s. The negative value of time implies an event before the start of motion, so we discard it. Therefore, t = 3.96 s t = 3.96 s Discussion 

The time for projectile motion is completely determined by the vertical motion. So any projectile that has an initial vertical velocity of 14.3 m / s 14.3 m / s and lands 20.0 m below its starting altitude will spend 3.96 s in the air. Practice Problems 

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The fact that vertical and horizontal motions are independent of each other lets us predict the range of a projectile. The range is the horizontal distance R traveled by a projectile on level ground, as illustrated in [link] . Throughout history, people have been interested in finding the range of projectiles for practical purposes, such as aiming cannons. Trajectories of projectiles on level ground. (a) The greater the initial speed v 0 v 0 , the greater the range for a given initial angle. (b) The effect of initial angle 0 0 on the range of a projectile with a given initial speed. Note that any combination of trajectories that add to 90 degrees will have the same range in the absence of air resistance, although the maximum heights of those paths are different. 

How does the initial velocity of a projectile affect its range? Obviously, the greater the initial speed v 0 v 0 , the greater the range, as shown in the figure above. The initial angle 0 0 also has a dramatic effect on the range. When air resistance is negligible, the range R R of a projectile on level ground is R = v 0 2 sin 2 0 g R = v 0 2 sin 2 0 g 

where v 0 v 0 is the initial speed and 0 0 is the initial angle relative to the horizontal. It is important to note that the range doesn t apply to problems where the initial and final y position are different, or to cases where the object is launched perfectly horizontally. Projectile Motion 

In this simulation you will learn about projectile motion by blasting objects out of a cannon. You can choose between objects such as a tank shell, a golf ball or even a Buick. Experiment with changing the angle, initial speed, and mass, and adding in air resistance. Make a game out of this simulation by trying to hit the target. Click here for the simulation 

[link] Section Summary Projectile motion is the motion of an object through the air that is subject only to the acceleration of gravity. Projectile motion in the horizontal and vertical directions are independent of one another. The maximum height of an projectile is the highest altitude, or maximum displacement in the vertical position reached in the path of a projectile. The range is the maximum horizontal distance traveled by a projectile. To solve projectile problems: choose a coordinate system; analyze the motion in the vertical and horizontal direction separately; then, recombine the horizontal and vertical components using vector addition equations. Key Equations angle of displacement = tan 1 ( y / x ) = tan 1 ( y / x ) velocity v = v x 2 + v y 2 v = v x 2 + v y 2 angle of velocity v = tan 1 ( v y / v x ) v = tan 1 ( v y / v x ) maximum height h = v 0 y 2 2 g h = v 0 y 2 2 g range R = v 0 2 sin 2 0 g R = v 0 2 sin 2 0 g Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students achieve the learning objectives for this section. If students are struggling with a specific objective, the Check Your Understanding will help identify which objective is causing the problem and direct students to the relevant content. Concept Items 

[link] Problems 

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[link] Critical Thinking 

[link] Test Prep Multiple Choice 

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[link] Test Prep Short Answer 

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[link] Test Prep Extended Response 

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[link] Glossary air resistance a frictional force that slows the motion of objects as they travel through the air; when solving basic physics problems, air resistance is assumed to be zero maximum height (of a projectile) the highest altitude, or maximum displacement in the vertical position reached in the path of a projectile projectile an object that travels through the air and experiences only acceleration due to gravity projectile motion the motion of an object that is subject only to the acceleration of gravity range the maximum horizontal distance that a projectile travels trajectory the path of a projectile through the airVector Addition and Subtraction: Graphical Methods Vector Addition and Subtraction: Graphical Methods Section Learning Objectives 

By the end of this section, you will be able to: Describe the graphical method of vector addition and subtraction Use the graphical method of vector addition and subtraction to solve physics problems 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in two dimensions for a variety of situations. The student is expected to: (4E) : develop and interpret free-body force diagrams Section Key Terms graphical method head (of a vector) head-to-tail method resultant resultant vector tail vector addition vector subtraction The Graphical Method of Vector Addition and Subtraction 

Recall that a vector is a quantity that has magnitude and direction. For example, displacement, velocity, acceleration, and force are all vectors. In one-dimensional or straight-line motion, the direction of a vector can be given simply by a plus or minus sign. Motion that is forward, to the right, or upward is usually considered to be positive (+); and motion that is backward, to the left, or downward is usually considered to be negative ( ). 

In two dimensions, a vector describes motion in two perpendicular directions (such as vertical and horizontal). For vertical and horizontal motion, each vector is made up of vertical and horizontal components. In a one-dimensional problem, one of the components simply has a value of zero. For two-dimensional vectors, we work with vectors by using a frame of reference such as a coordinate system. Just as with one-dimensional vectors, we graphically represent vectors with an arrow having a length proportional to the vector s magnitude and pointing in the direction that the vector points. 

[BL] [OL] Review vectors and free body diagrams. Recall how velocity, displacement and acceleration vectors are represented. 

[link] shows a graphical representation of a vector; the total displacement for a person walking in a city. The person first walks nine blocks east and then five blocks north. Her total displacement does not match her path to her final destination. The displacement simply connects her starting point with her ending point using a straight line, which is the shortest distance. We use the notation that a boldface symbol, such as D , stands for a vector. Its magnitude is represented by the symbol in italics, D , and its direction is given by an angle represented by the symbol . . Note that her displacement would be the same if she had begun by first walking five blocks north and then walking nine blocks east. 

In this text, we represent a vector with a boldface variable. For example, we represent a force with the vector F , which has both magnitude and direction. The magnitude of the vector is represented by the variable in italics, F , and the direction of the variable is given by the angle . . A person walks nine blocks east and five blocks north. The displacement is 10.3 blocks at an angle 29.1 29.1 north of east. 

The head-to-tail method is a graphical way to add vectors. The tail of the vector is the starting point of the vector, and the head (or tip) of a vector is the pointed end of the arrow. The following steps describe how to use the head-to-tail method for graphical vector addition . Let the x-axis represent the east-west direction. Using a ruler and protractor, draw an arrow to represent the first vector (nine blocks to the east), as shown in [link] (a) . The diagram shows a vector with a magnitude of nine units and a direction of 0 . Let the y-axis represent the north-south direction. Draw an arrow to represent the second vector (five blocks to the north). Place the tail of the second vector at the head of the first vector, as shown in [link] (b) . A vertical vector is added. If there are more than two vectors, continue to add the vectors head-to-tail as described in step 2. In this example, we have only two vectors, so we have finished placing arrows tip to tail. Draw an arrow from the tail of the first vector to the head of the last vector, as shown in [link] (c) . This is the resultant , or the sum, of the vectors. The diagram shows the resultant vector, a ruler, and protractor. To find the magnitude of the resultant, measure its length with a ruler. (When we deal with vectors analytically in the next section, the magnitude will be calculated by using the Pythagorean theorem.) To find the direction of the resultant, use a protractor to measure the angle it makes with the reference direction (in this case, the x -axis). When we deal with vectors analytically in the next section, the direction will be calculated by using trigonometry to find the angle. 

[AL] Ask two students to demonstrate pushing a table from two different directions. Ask students what they feel the direction of resultant motion will be. How would they represent this graphically? Recall that a vector s magnitude is represented by the length of the arrow. Demonstrate the head-to-tail method of adding vectors, using the example given in the chapter. Ask students to practice this method of addition using a scale and a protractor. 

[BL] [OL] [AL] Ask students if anything changes by moving the vector from one place to another on a graph. How about the order of addition? Would that make a difference? Introduce negative of a vector and vector subtraction. Visualizing Vector Addition Examples 

This video shows four graphical representations of vector addition and matches them to the correct vector addition formula. 

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Vector subtraction is done in the same way as vector addition with one small change. We add the first vector to the negative of the vector that needs to be subtracted. A negative vector has the same magnitude as the original vector, but points in the opposite direction (as shown in [link] ). Subtracting the vector B from the vector A , which is written as A B , is the same as A + ( B ). Since it does not matter in what order vectors are added, A B is also equal to ( B ) + A . This is true for scalars as well as vectors. For example: 5 2 = 5 + ( 2) = ( 2) + 5. The diagram shows a vector, B, and the negative of this vector, B. 

Global angles are calculated in the counterclockwise direction. The clockwise direction is considered negative. For example, an angle of 30 30 south of west is the same as the global angle 210 , 210 , which can also be expressed as 150 150 from the positive x-axis. Using the Graphical Method of Vector Addition and Subtraction to Solve Physics Problems 

Now that we have the skills to work with vectors in two dimensions, we can apply vector addition to graphically determine the resultant vector , which represents the total force. Consider an example of force involving two ice skaters pushing a third as seen in [link] . Part (a) shows an overhead view of two ice skaters pushing on a third. Forces are vectors and add like vectors, so the total force on the third skater is in the direction shown. In part (b), we see a free-body diagram representing the forces acting on the third skater. 

In problems where variables such as force are already known, the forces can be represented by making the length of the vectors proportional to the magnitudes of the forces. For this, you need to create a scale. For example, each centimeter of vector length could represent 50 N worth of force. Once you have the initial vectors drawn to scale, you can then use the head-to-tail method to draw the resultant vector. The length of the resultant can then be measured and converted back to the original units using the scale you created. 

You can tell by looking at the vectors in the free-body diagram in [link] that the two skaters are pushing on the third skater with equal-magnitude forces, since the length of their force vectors are the same. (Note, however, that the forces are not equal because they act in different directions). If, for example, each force had a magnitude of 400 N, then we would find the magnitude of the total external force acting on the third skater by finding the magnitude of the resultant vector. Since the forces act at a right angle to one another, we can use the Pythagorean theorem. For a triangle with sides a, b, and c, the Pythagorean theorem tells us that a 2 + b 2 = c 2 c = a 2 + b 2 a 2 + b 2 = c 2 c = a 2 + b 2 

Applying this theorem to the triangle made by F 1 , F 2 , and F tot in [link] , we get F tot 2 = F 1 2 + F 1 2 , F tot 2 = F 1 2 + F 1 2 , 

or F tot = ( 400 N ) 2 + ( 400 N ) 2 = 566 N F tot = ( 400 N ) 2 + ( 400 N ) 2 = 566 N 

Note that, if the vectors were not at a right angle to each other ( 90 90 to one another), we would not be able to use the Pythagorean theorem to find the magnitude of the resultant vector. Another scenario where adding two-dimensional vectors is necessary is for velocity, where the direction may not be purely east-west or north-south, but some combination of these two directions. In the next section, we cover how to solve this type of problem analytically. For now let s consider the problem graphically. Adding Vectors Graphically by Using the Head-to-Tail Method: A Woman Takes a Walk 

Use the graphical technique for adding vectors to find the total displacement of a person who walks the following three paths (displacements) on a flat field. First, he walks 25 m in a direction 49 49 north of east. Then, he walks 23 m heading 15 15 north of east. Finally, he turns and walks 32 m in a direction 68 68 south of east. Strategy 

Graphically represent each displacement vector with an arrow, labeling the first A , the second B , and the third C . Make the lengths proportional to the distance of the given displacement and orient the arrows as specified relative to an east-west line. Use the head-to-tail method outlined above to determine the magnitude and direction of the resultant displacement, which we ll call R . Solution 

(1) Draw the three displacement vectors, creating a convenient scale (such as 1 cm of vector length on paper equals 1 m in the problem), as shown in [link] . The three displacement vectors are drawn first. 

(2) Place the vectors head to tail, making sure not to change their magnitude or direction, as shown in [link] . Next, the vectors are placed head to tail. 

(3) Draw the resultant vector R from the tail of the first vector to the head of the last vector, as shown in [link] . The resultant vector is drawn . 

(4) Use a ruler to measure the magnitude of R , remembering to convert back to the units of meters using the scale. Use a protractor to measure the direction of R . While the direction of the vector can be specified in many ways, the easiest way is to measure the angle between the vector and the nearest horizontal or vertical axis. Since R is south of the eastward pointing axis (the x-axis), we flip the protractor upside down and measure the angle between the eastward axis and the vector, as illustrated in [link] . A ruler is used to measure the magnitude of R , and a protractor is used to measure the direction of R . 

In this case, the total displacement R has a magnitude of 50 m and points 7 7 south of east. Using its magnitude and direction, this vector can be expressed as 

R = 50 m 

and 

= 7 = 7 south of east Discussion 

The head-to-tail graphical method of vector addition works for any number of vectors. It is also important to note that it does not matter in what order the vectors are added. Changing the order does not change the resultant. For example, we could add the vectors as shown in [link] , and we would still get the same solution. Vectors can be added in any order to get the same result. 

[BL] [OL] [AL] Ask three students to enact the situation shown in [link] . Recall how these forces can be represented in a free-body diagram. Giving values to these vectors, show how these can be added graphically. Subtracting Vectors Graphically: A Woman Sailing a Boat 

A woman sailing a boat at night is following directions to a dock. The instructions read to first sail 27.5 m in a direction 66.0 66.0 north of east from her current location, and then travel 30.0 m in a direction 112 112 north of east (or 22.0 22.0 west of north). If the woman makes a mistake and travels in the opposite direction for the second leg of the trip, where will she end up? (The two legs of the woman s trip are illustrated in [link] . In the diagram, the first leg of the trip is represented by vector A and the second leg is represented by vector B. Strategy 

We can represent the first leg of the trip with a vector A , and the second leg of the trip that she was supposed to take with a vector B . Since the woman mistakenly travels in the opposite direction for the second leg of the journey, the vector for second leg of the trip she actually takes is B . Therefore, she will end up at a location A + ( B ), or A B . Note that B has the same magnitude as B (30.0 m), but is in the opposite direction, 68 ( 180 112 ) 68 ( 180 112 ) south of east, as illustrated in [link] . Vector B represents traveling in the opposite direction of vector B. 

We use graphical vector addition to find where the woman arrives: A + ( B ). Solution 

(1) To determine the location at which the woman arrives by accident, draw vectors A and B . 

(2) Place the vectors head to tail. 

(3) Draw the resultant vector R . 

(4) Use a ruler and protractor to measure the magnitude and direction of R . 

These steps are demonstrated in [link] . The vectors are placed head to tail. 

In this case 

R = 23.0 m R = 23.0 m 

and 

= 7.5 south of east = 7.5 south of east Discussion 

Because subtraction of a vector is the same as addition of the same vector with the opposite direction, the graphical method for subtracting vectors works the same as for adding vectors. Adding Velocities: A Boat on a River 

A boat attempts to travel straight across a river at a speed of 3.8 m/s. The river current flows at a speed v river of 6.1 m/s to the right. What is the total velocity and direction of the boat? Note: you can represent each meter per second of velocity as one centimeter of vector length in your drawing. Strategy 

We start by choosing a coordinate system with its x-axis parallel to the velocity of the river. Because the boat is directed straight toward the other shore, its velocity is perpendicular to the velocity of the river. We draw the two vectors, v boat and v river , as shown in [link] . 

Using the head-to-tail method, we draw the resulting total velocity vector from the tail of v boat to the head of v river . A boat attempts to travel across a river. What is the total velocity and direction of the boat? Solution 

By using a ruler, we find that the length of the resultant vector is 7.2 cm, which means that the magnitude of the total velocity is 

v tot = 7.2 m/s. 

By using a protractor to measure the angle, we find = 32.0 = 32.0 Discussion 

If the velocity of the boat and river were equal, then the direction of the total velocity would have been 45 . However, since the velocity of the river is greater than that of the boat, the direction is less than 45 with respect to the shore (or x -axis). 

Plot the way from the classroom to the cafeteria (or any two places in the school on the same level). Ask students to come up with approximate distances. Ask them to do a vector analysis of the path. What is the total distance travelled? What is the displacement? Practice Problems 

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[link] Vector Addition 

In this simulation , you will experiment with adding vectors graphically. Click and drag the red vectors from the Grab One basket onto the graph in the middle of the screen. These red vectors can be rotated, stretched, or repositioned by clicking and dragging with your mouse. Check the Show Sum box to display the resultant vector (in green), which is the sum of all of the red vectors placed on the graph. To remove a red vector, drag it to the trash or click the Clear All button if you wish to start over. Notice that, if you click on any of the vectors, the | R | | R | is its magnitude, is its direction with respect to the positive x -axis, R x is its horizontal component, and R y is its vertical component. You can check the resultant by lining up the vectors so that the head of the first vector touches the tail of the second. Continue until all of the vectors are aligned together head-to-tail. You will see that the resultant magnitude and angle is the same as the arrow drawn from the tail of the first vector to the head of the last vector. Rearrange the vectors in any order head-to-tail and compare. The resultant will always be the same. Click here for the simulation 

[link] Section Summary The graphical method of adding vectors A A and B B involves drawing vectors on a graph and adding them by using the head-to-tail method. The resultant vector R R is defined such that A + B = R . The magnitude and direction of R R are then determined with a ruler and protractor. The graphical method of subtracting vectors A and B involves adding the opposite of vector B , which is defined as B . In this case, A B = A + ( B ) = R . A B = A + ( B ) = R . Next, use the head-to-tail method as for vector addition to obtain the resultant vector R R . Addition of vectors is independent of the order in which they are added; A + B = B + A . The head-to-tail method of adding vectors involves drawing the first vector on a graph and then placing the tail of each subsequent vector at the head of the previous vector. The resultant vector is then drawn from the tail of the first vector to the head of the final vector. Variables in physics problems, such as force or velocity, can be represented with vectors by making the length of the vector proportional to the magnitude of the force or velocity. Problems involving displacement, force, or velocity may be solved graphically by measuring the resultant vector s magnitude with a ruler and measuring the direction with a protractor. Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students achieve the learning objectives for this section. If students are struggling with a specific objective, the Check Your Understanding will help identify which objective is causing the problem and direct students to the relevant content. Concept Items 

[link] Problems 

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[link] Critical Thinking 

[link] Test Prep Multiple Choice 

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[link] Test Prep Short Answer 

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[link] Test Prep Extended Response 

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[link] Glossary graphical method drawing vectors on a graph to add them using the head-to-tail method head (of a vector) the end point of a vector; the location of the vector s arrow; also referred to as the tip head-to-tail method a method of adding vectors in which the tail of each vector is placed at the head of the previous vector resultant the sum of the a collection of vectors resultant vector the vector sum of two or more vectors tail the starting point of a vector; the point opposite to the head or tip of the arrow vector addition adding together two or more vectorsVector Addition and Subtraction: Analytical Methods Vector Addition and Subtraction: Analytical Methods Section Learning Objectives 

By the end of this section, you will be able to: Define components of vectors Describe the analytical method of vector addition and subtraction Use the analytical method of vector addition and subtraction to solve problems 

The learning objectives in this section will help your students master the following TEKS: (3) Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to: (3F) : express and interpret relationships symbolically in accordance with accepted theories to make predictions and solve problems mathematically, including problems requiring proportional reasoning and graphical vector addition (4) Science concepts. The student knows and applies the laws governing motion in two dimensions for a variety of situations. The student is expected to: (4E) : develop and interpret free-body force diagrams (4F) : identify and describe motion relative to different frames of reference Section Key Terms analytical method component (of a two-dimensional vector) Components of Vectors 

For the analytical method of vector addition and subtraction, we use some simple geometry and trigonometry, instead of using a ruler and protractor as we did for graphical methods. However, the graphical method will still come in handy to visualize the problem by drawing vectors using the head-to-tail method. The analytical method is more accurate than the graphical method, which is limited by the precision of the drawing. For a refresher on the definitions of the sine, cosine, and tangent of an angle, see [link] . For a right triangle, the sine, cosine, and tangent of are defined in terms of the adjacent side, the opposite side, or the hypotenuse. In this figure, x is the adjacent side, y is the opposite side, and h is the hypotenuse. 

[BL] [OL] Review trigonometric concepts of sine, cosine, tangent and the Pythagorean theorem. 

Since, by definition, cos = x / h cos = x / h , we can find the length x if we know h and by using x = h cos x = h cos . Similarly, we can find the length of y by using y = h sin y = h sin . These trigonometric relationships are useful for adding vectors. 

When a vector acts in more than one dimension, it is useful to break it down into its x and y components. For a two-dimensional vector, a component is a piece of a vector that points in either the x- or y-direction. Every 2-d vector can be expressed as a sum of its x and y components. 

For example, given a vector like A A in [link] , we may want to find what two perpendicular vectors, A x A x and A y A y , add to produce it. In this example, A x A x and A y A y form a right triangle, meaning that the angle between them is 90 degrees. This is a common situation in physics and happens to be the least complicated situation trigonometrically. The vector A A , with its tail at the origin of an x, y-coordinate system, is shown together with its x - and y -components, A x A x and A y . A y . These vectors form a right triangle. 

A x A x and A y A y are defined to be the components of A A along the x - and y -axes. The three vectors, A A , A x A x , and A y A y , form a right triangle: A x + A y = A . A x + A y = A . 

If the vector A A is known, then its magnitude A A (its length) and its angle (its direction) are known. To find A x A x and A y A y , its x - and y -components, we use the following relationships for a right triangle: A x = A cos A x = A cos 

and A y = A sin A y = A sin 

Where A x A x is the magnitude of A in the x-direction, A y A y is the magnitude of A in the y-direction, and is the angle of the resultant with respect to the x-axis, as shown in [link] . The magnitudes of the vector components A x A x and A y A y can be related to the resultant vector A A and the angle with trigonometric identities. Here we see that A x = A cos A x = A cos and A y = A sin . A y = A sin . 

[BL] [OL] [AL] Derive the formula for getting the magnitude and direction of a vector. 

Students might be confused between the relationship A x + A y = A A x + A y = A , which shows the addition of vectors and A = A x 2 + A y 2 A = A x 2 + A y 2 which shows the addition of magnitudes of vectors. 

Suppose, for example, that A A is the vector representing the total displacement of the person walking in a city, as illustrated in [link] . We can use the relationships A x = A cos A x = A cos and A y = A sin A y = A sin to determine the magnitude of the horizontal and vertical component vectors in this example. 

Then A = 10.3 blocks and = 29.1 = 29.1 , so that: 

A x = A cos = ( 10.3 blocks)(cos29 .1 ) = ( 10.3 blocks)(0 .874) = 9 .0 blocks A x = A cos = ( 10.3 blocks)(cos29 .1 ) = ( 10.3 blocks)(0 .874) = 9 .0 blocks 

This magnitude indicates that the walker has traveled 9 blocks to the east in other words, a 9-block eastward displacement. Similarly, 

A y = A sin = ( 10.3 blocks)(sin29 .1 ) = ( 10.3 blocks)(0 .846) = 5 .0 blocks A y = A sin = ( 10.3 blocks)(sin29 .1 ) = ( 10.3 blocks)(0 .846) = 5 .0 blocks 

indicating that the walker has traveled 5 blocks to the north a 5-block northward displacement. Analytical Method of Vector Addition and Subtraction 

Calculating a resultant vector (or vector addition) is the reverse of breaking the resultant down into its components. If the perpendicular components A x A x and A y A y of a vector A A are known, then we can find A A analytically. How do we do this? Since, by definition, tan = y / x (or in this case tan = A y / A x ), tan = y / x (or in this case tan = A y / A x ), 

we solve for to find the direction of the resultant = tan 1 ( A y / A x ) = tan 1 ( A y / A x ) 

Since this is a right triangle, the Pythagorean theorem (x 2 + y 2 = h 2 ) for finding the hypotenuse applies. In this case, it becomes 

A 2 = A x 2 + A y 2 A 2 = A x 2 + A y 2 

Solving for A gives A = A x 2 + A y 2 A = A x 2 + A y 2 

In summary, to find the magnitude A A and direction of a vector from its perpendicular components A x A x and A y A y , as illustrated in [link] , we use the following relationships: A = A x 2 + A y 2 = tan 1 ( A y / A x ) A = A x 2 + A y 2 = tan 1 ( A y / A x ) The magnitude and direction of the resultant vector A A can be determined once the horizontal components A x A x and A y A y have been determined. 

[BL] [OL] [AL] Demonstrate a problem involving displacement by physically walking along the specified direction. Show how this can be represented on a graph. Explain that even when solving problems analytically; representing it on a graph would make it easier to visualize the problem. 

Sometimes, the vectors added are not perfectly perpendicular to one another. An example of this is the case below, where the vectors A A and B B are added to produce the resultant R R , as illustrated in [link] . Vectors A A and B B are two legs of a walk, and R R is the resultant or total displacement. You can use analytical methods to determine the magnitude and direction of R R . 

If A A and B B represent two legs of a walk (two displacements), then R R is the total displacement. The person taking the walk ends up at the tip of R R . There are many ways to arrive at the same point. The person could have walked straight ahead first in the x -direction and then in the y -direction. Those paths are the x - and y -components of the resultant, R x R x and R y . R y . If we know R x R x and R y R y , we can find R R and using the equations R = R x 2 + R y 2 R = R x 2 + R y 2 and = t a n 1 ( R y / R x ) = t a n 1 ( R y / R x ) . Draw in the x and y components of each vector (including the resultant) with a dashed line. Use the equations A x = A cos A x = A cos and A y = A sin A y = A sin to find the components. In [link] , these components are A x A x , A y A y , B x B x , and B y . B y . Vector A A makes an angle of A A with the x-axis, and vector B B makes and angle of B B with its own x-axis (which is slightly above the x-axis used by vector A ). To add vectors A A and B , B , first determine the horizontal and vertical components of each vector. These are the dotted vectors A x , A x , A y A y B y B y shown in the image. Find the x component of the resultant by adding the x component of the vectors: R x = A x + B x R x = A x + B x 

and find the y component of the resultant (as illustrated in [link] ) by adding the y component of the vectors: R y = A y + B y R y = A y + B y The vectors A x A x and B x B x add to give the magnitude of the resultant vector in the horizontal direction, R x . R x . Similarly, the vectors A y A y and B y B y add to give the magnitude of the resultant vector in the vertical direction, R y . R y . 

Now that we know the components of R , R , we can find its magnitude and direction. To get the magnitude of the resultant R, use the Pythagorean theorem: R = R x 2 + R y 2 . R = R x 2 + R y 2 . To get the direction of the resultant: = tan 1 ( R y / R x ) . = tan 1 ( R y / R x ) . Classifying Vectors and Quantities Example 

This video contrasts and compares three vectors in terms of their magnitudes, positions, and directions. 

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In the video, the vectors were represented with an arrow above them rather than in bold. This is a common notation in math classes. Using the Analytical Method of Vector Addition and Subtraction to Solve Problems 

The [link] uses the analytical method to add vectors. An Accelerating Subway Train 

Add the vector A A to the vector B B shown in [link] , using the steps above. The x -axis is along the east west direction, and the y -axis is along the north south directions. A person first walks 53 .0 m 53 .0 m in a direction 20 .0 20 .0 north of east, represented by vector A . A . The person then walks 34 .0 m 34 .0 m in a direction 63 .0 63 .0 north of east, represented by vector B . B . You can use analytical models to add vectors. Strategy 

The components of A A and B B along the x - and y -axes represent walking due east and due north to get to the same ending point. We will solve for these components and then add them in the x-direction and y-direction to find the resultant. Solution 

First, we find the components of A A and B B along the x - and y -axes. From the problem, we know that A = 53.0 m A = 53.0 m , A = 20.0 A = 20.0 , B B = 34 .0 m 34 .0 m , and B = 63.0 B = 63.0 . We find the x -components by using A x = A cos A x = A cos , which gives A x = A cos A = ( 53.0 m ) ( cos 20.0 ) = ( 53.0 m ) ( 0.940 ) = 49.8 m A x = A cos A = ( 53.0 m ) ( cos 20.0 ) = ( 53.0 m ) ( 0.940 ) = 49.8 m 

and B x = B cos B = ( 34.0 m ) ( cos 63.0 ) = ( 34.0 m ) ( 0.454 ) = 15.4 m B x = B cos B = ( 34.0 m ) ( cos 63.0 ) = ( 34.0 m ) ( 0.454 ) = 15.4 m 

Similarly, the y -components are found using A y = A sin A A y = A sin A : A y = A sin A = ( 53.0 m ) ( sin 20.0 ) = ( 53.0 m ) ( 0.342 ) = 18.1 m A y = A sin A = ( 53.0 m ) ( sin 20.0 ) = ( 53.0 m ) ( 0.342 ) = 18.1 m 

and B y = B sin B = ( 34.0 m ) ( sin 63.0 ) = ( 34.0 m ) ( 0.891 ) = 30.3 m . B y = B sin B = ( 34.0 m ) ( sin 63.0 ) = ( 34.0 m ) ( 0.891 ) = 30.3 m . 

The x - and y -components of the resultant are R x = A x + B x = 49.8 m + 15.4 m = 65.2 m R x = A x + B x = 49.8 m + 15.4 m = 65.2 m 

and R y = A y + B y = 18.1 m + 30.3 m = 48.4 m . R y = A y + B y = 18.1 m + 30.3 m = 48.4 m . 

Now we can find the magnitude of the resultant by using the Pythagorean theorem: R = R x 2 + R y 2 = ( 65.2 ) 2 + ( 48.4 ) 2 m R = R x 2 + R y 2 = ( 65.2 ) 2 + ( 48.4 ) 2 m 

so that R = 6601 m = 81.2 m . R = 6601 m = 81.2 m . 

Finally, we find the direction of the resultant: = tan 1 ( R y / R x ) = + tan 1 ( 48.4 / 65.2 ) . = tan 1 ( R y / R x ) = + tan 1 ( 48.4 / 65.2 ) . 

This is = tan 1 ( 0.742 ) = 36.6 . = tan 1 ( 0.742 ) = 36.6 . Discussion 

This example shows vector addition using the analytical method. Vector subtraction using the analytical method is very similar. It is just the addition of a negative vector. That is, A B A + ( B ) A B A + ( B ) . The components of B B are the negatives of the components of B B . Therefore, the x - and y -components of the resultant A B = R A B = R are R x = A x + - B x R x = A x + - B x 

and R y = A y + - B y R y = A y + - B y 

and the rest of the method outlined above is identical to that for addition. Practice Problems 

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[link] Atmospheric Science This picture shows Bert Foord during a television Weather Forecast from the Meteorological Office in 1963. (credit: BBC TV) 

Atmospheric science is a physical science , meaning that it is a science based heavily on physics. Atmospheric science includes meteorology (the study of weather) and climatology (the study of climate). Climate is basically the average weather over a longer time scale. Weather changes quickly over time, whereas the climate changes more gradually. 

The movement of air, water and heat is vitally important to climatology and meteorology. Since motion is such a major factor in weather and climate, this field uses vectors for much of its math. 

Vectors are used to represent currents in the ocean, wind velocity and forces acting on a parcel of air. You have probably seen a weather map using vectors to show the strength (magnitude) and direction of the wind. 

Vectors used in atmospheric science are often three-dimensional. We won t cover three-dimensional motion in this text, but to go from two-dimensions to three-dimensions, you simply add a third vector component. Three-dimensional motion is represented as a combination of x-, y- and z components, where z is the altitude. 

Vector calculus combines vector math with calculus, and is often used to find the rates of change in temperature, pressure or wind speed over time or distance. This is useful information, since atmospheric motion is driven by changes in pressure or temperature. The greater the variation in pressure over a given distance, the stronger the wind to try to correct that imbalance. Cold air tends to be more dense and therefore has higher pressure than warm air. Higher pressure air rushes into a region of lower pressure and gets deflected by the spinning of the Earth, and friction slows the wind at Earth s surface. 

Finding how wind changes over distance and multiplying vectors lets meteorologists, like the one shown in [link] , figure out how much rotation (spin) there is in the atmosphere at any given time and location. This is an important tool for tornado prediction. Conditions with greater rotation are more likely to produce tornadoes. 

[link] Section Summary The analytical method of vector addition and subtraction uses the Pythagorean theorem and trigonometric identities to determine the magnitude and direction of a resultant vector. The steps to add vectors A A and B B using the analytical method are as follows: Determine the coordinate system for the vectors. Then, determine the horizontal and vertical components of each vector using the equations: A x = A cos B x = B cos A x = A cos B x = B cos 

And A y = A sin B y = B sin A y = A sin B y = B sin Add the horizontal and vertical components of each vector to determine the components R x R x and R y R y of the resultant vector, R R : R x = A x + B x R x = A x + B x 

and R y = A y + B y . R y = A y + B y . Use the Pythagorean theorem to determine the magnitude, R R , of the resultant vector R R : R = R x 2 + R y 2 . R = R x 2 + R y 2 . Use a trigonometric identity to determine the direction, , of R R : = tan 1 ( R y / R x ) . = tan 1 ( R y / R x ) . Key Equations resultant magnitude R = R x 2 + R y 2 R = R x 2 + R y 2 resultant direction = tan 1 ( R y / R x ) = tan 1 ( R y / R x ) x-component of a vector A (when an angle is given relative to the horizontal) A x = A cos A x = A cos y-component of a vector A (when an angle is given relative to the horizontal) A y = A sin A y = A sin addition of vectors A x + A y = A A x + A y = A Check Your Understanding 

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[link] Glossary analytical method the method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities component (of a 2-dimensional vector) a piece of a vector that points in either the vertical or the horizontal direction; every 2-d vector can be expressed as a sum of two vertical and horizontal vector componentsKepler s Laws of Planetary Motion Kepler s Laws of Planetary Motion Section Learning Objectives 

By the end of this section, you will be able to: Explain Kepler s three laws of planetary motion Apply Kepler s laws to calculate characteristics of orbits 

The learning objectives in this section will help your students master the following TEKS: (4C) : Analyze and describe accelerated motion in two dimensions using equations, including projectile and circular examples. 

In this section students will apply Kepler s laws of planetary motion to objects in the solar system. 

[BL] [OL] Discuss the historical setting in which Kepler worked. Most people still thought the Earth was the center of the universe, and yet Kepler not only knew that the planets circled the sun, he found patterns in the paths they followed. What would it be like to be that far ahead of almost everyone? A fascinating description of this is given in the program "Cosmos" with Carl Sagan (Episode 3, Harmony of the Worlds). 

[AL] Explain that Kepler s laws were laws and not theories. Laws describe patterns in nature that always repeat themselves under the same set of conditions. Theories provide an explanation for the patterns. Kepler provided no explanation. Section Key Terms aphelion Copernican model eccentricity Kepler s laws of planetary motion perihelion Ptolemaic model Concepts Related to Kepler s Laws of Planetary Motion 

Examples of orbits abound. Hundreds of artificial satellites orbit Earth together with thousands of pieces of debris. The moon s orbit around Earth has intrigued humans from time immemorial. The orbits of planets, asteroids, meteors, and comets around the sun are no less interesting. If we look farther, we see almost unimaginable numbers of stars, galaxies, and other celestial objects orbiting one another and interacting through gravity. 

All these motions are governed by gravitational force. The orbital motions of objects in our own solar system are simple enough to describe with a few fairly simple laws. The orbits of planets and moons satisfy the following two conditions: The mass of the orbiting object, m , is small compared to the mass of the object it orbits, M . The system is isolated from other massive objects. 

[OL] Ask the students to explain the criteria to see if they understand relative mass and isolated systems. 

Based on the motion of the planets about the sun, Kepler devised a set of three classical laws, called Kepler s laws of planetary motion , that describe the orbits of all bodies satisfying these two conditions. The orbit of each planet around the sun is an ellipse with the sun at one focus. Each planet moves so that an imaginary line drawn from the sun to the planet sweeps out equal areas in equal times. The ratio of the squares of the periods of any two planets about the sun is equal to the ratio of the cubes of their average distances from the sun. 

These descriptive laws are named for the German astronomer Johannes Kepler (1571 1630). He devised them after careful study (over some 20 years) of a large amount of meticulously recorded observations of planetary motion done by Tycho Brahe (1546 1601). Such careful collection and detailed recording of methods and data are hallmarks of good science. Data constitute the evidence from which new interpretations and meanings can be constructed. Let s look closer at each of these laws. 

[BL] Relate orbit to year and rotation to day. Be sure that students know that an object rotates on its axis and revolves around a parent body as it follows its orbit. 

[OL] See how many levels of orbital motion the students know and fill in the ones they don t. For example: moons orbit around planets; planets around stars; stars around the center of the galaxy, etc. 

[AL] From the point of view of Earth, which objects appear (incorrectly) to be orbiting Earth (stars, the sun, galaxies) and which can be seen to be orbiting parent bodies (the moon, moons of other planets, stars in other galaxies)? Kepler s First Law 

The orbit of each planet about the sun is an ellipse with the sun at one focus, as shown in [link] . The planet s closest approach to the sun is called aphelion and its farthest distance from the sun is called perihelion . (a) An ellipse is a closed curve such that the sum of the distances from a point on the curve to the two foci ( f 1 and f 2 ) is constant. (b) For any closed orbit, m follows an elliptical path with M at one focus. (c) The aphelion ( r a) is the closest distance between the planet and the sun, while the perihelion ( r p) is the farthest distance from the sun. 

[AL] Ask for a definition of planet. Prepare to discuss Pluto s demotion if it comes up. Discuss the first criterion in terms of center of rotation of a moon-planet system. Explain that for all planet-moon systems in the solar system, the center of rotation is within the planet. This is not true for Pluto and its largest moon, Charon, because their masses are similar enough that they rotate around a point in space between them. 

If you know the aphelion ( r a ) and perihelion ( r p ) distances, then you can calculate the semi-major axis ( a ) and semi-minor axis ( b ): a = ( r a + r p ) 2 b = r a r p a = ( r a + r p ) 2 b = r a r p 

[AL] If any students are interested and proficient in algebra and geometry, ask them to derive a formula that relates the length of the string and the distance between pins to the major and minor axes of an ellipse. Explain that this is a real world problem for workers who design elliptical tabletops and mirrors. 

[BL] [OL] Impress upon the students that Kepler had to crunch an enormous amount of data and that all his calculations had to be done by hand. Ask students to think of similar projects where scientists found order in a daunting amount of data (the periodic table, DNA structure, climate models, etc.). 

Demonstrate the pins and string method of drawing an ellipse, as shown in [link] , or have the students try it at home or in class. 

Ask students: Why does the string and pin method create a shape that conforms to Kepler's second law? That is, why is the shape an ellipse? 

Explain that the pins are the foci and explain what each of the three sections of string represents. Note that the pencil represents a planet and one of the pins represents the sun. You can draw an ellipse as shown by putting a pin at each focus, and then placing a loop of string around a pen and the pins and tracing a line on the paper. Kepler s Second Law 

Each planet moves so that an imaginary line drawn from the sun to the planet sweeps out equal areas in equal times, as shown in [link] . The shaded regions have equal areas. The time for m to go from A to B is the same as the time to go from C to D and from E to F. The mass m moves fastest when it is closest to M . Kepler s second law was originally devised for planets orbiting the sun, but it has broader validity. 

Ask the students to imagine how complicated it would be to describe the motion of the planets mathematically, if it is assumed that Earth is stationary. And yet, people tried to do this for hundreds of years, while overlooking the simple explanation that all planets circle the sun. 

[OL] Ask students to use this figure to understand why planets and comets travel faster when they are closer to the sun. Explain that time intervals and areas are constant, but both velocity and distance from the sun vary. 

Note that while, for historical reasons, Kepler s laws are stated for planets orbiting the sun, they are actually valid for all bodies satisfying the two previously stated conditions. Kepler s Third Law 

The ratio of the periods squared of any two planets around the sun is equal to the ratio of their average distances from the sun cubed. In equation form, this is T 1 2 T 2 2 = r 1 3 r 2 3 , T 1 2 T 2 2 = r 1 3 r 2 3 , 

where T is the period (time for one orbit) and r is the average distance (also called orbital radius). This equation is valid only for comparing two small masses orbiting a single large mass. Most importantly, this is only a descriptive equation; it gives no information about the cause of the equality. 

[BL] See if students can rearrange this equation to solve for any one of the variables when the other three are known. 

[AL] Show a solution for one of the periods T or radii r and ask students to interpret the fractional powers on the right hand side of the equation. 

[OL] Emphasize that this approach only works for two satellites orbiting the same parent body. The parent body must be the same because r 2 / T 2 = G M / ( 4 2 ) r 2 / T 2 = G M / ( 4 2 ) and M is the mass of the parent body. If M changes, the ratio r 3 / T 2 also changes. History: Ptolemy vs. Copernicus 

Before the discoveries of Kepler, Copernicus, Galileo, Newton, and others, the solar system was thought to revolve around Earth as shown in [link] (a) . This is called the Ptolemaic model , named for the Greek philosopher Ptolemy who lived in the second century AD. (Note that the P is silent.) The Ptolemaic model is characterized by a list of facts for the motions of planets, with no explanation of cause and effect. There tended to be a different rule for each heavenly body and a general lack of simplicity. 

[link] (b) represents the modern or Copernican model . In this model, a small set of rules and a single underlying force explain not only all planetary motion in the solar system, but also all other situations involving gravity. The breadth and simplicity of the laws of physics are compelling. (a) The Ptolemaic model of the universe has Earth at the center with the moon, the planets, the sun, and the stars revolving about it in complex circular paths. This geocentric (Earth-centered) model, which can be made progressively more accurate by adding more circles, is purely descriptive, containing no hints about the causes of these motions. (b) The Copernican heliocentric (sun-centered) model is a simpler and more accurate model. 

Nicolaus Copernicus (1473 1543) first had the idea that the planets circle the sun, in about 1514. It took him almost 20 years to work out the mathematical details for his model. He waited another 10 years or so to publish his work. It is thought he hesitated because he was afraid people would make fun of his theory. Actually, the reaction of many people was more one of fear and anger. Many people felt the Copernican model threatened their basic belief system. About 100 years later, the astronomer Galileo was put under house arrest for providing evidence that planets, including Earth, orbited the sun. In all, it took almost 300 years for everyone to admit that Copernicus had been right all along. 

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Introduce the historical debate around the geocentric versus the heliocentric view of the universe. Stress how controversial this debate was at the time. Explain that this was important to people because their worldview and religious beliefs were at stake. Acceleration 

This simulation allows you to create your own solar system so that you can see how changing distances and masses determines the orbits of planets. Click "Help" for instructions. Click here for the simulation 

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Give the students ample time to manipulate this animation. It may take some time to get the parameters adjusted so that they can see how mass and eccentricity affect the orbit. Initially, the planet is likely to disappear off the screen or crash into the sun. Calculations Related to Kepler s Laws of Planetary Motion Kepler s First Law 

Refer back to this figure (a) . Notice which distances are constant. The foci are fixed, so distance f 1 f 2 f 1 f 2 is a constant. The definition of an ellipse states that the sum of the distances f 1 m + m f 2 f 1 m + m f 2 is also constant. These two facts taken together mean that the perimeter of triangle f 1 m f 2 f 1 m f 2 must also be constant. Knowledge of these constants will help you determine positions and distances of objects in a system that includes one object orbiting another. Kepler s Second Law 

Refer back to this figure . The second law says that the segments have equal area and that it takes equal time to sweep through each segment. That is, the time it takes to travel from A to B equals the time it takes to travel from C to D, and so forth. Velocity v equals distance d divided by time t : v = d / t v = d / t . Then, t = d / v t = d / v , so distance divided by velocity is also a constant. For example, if we know the average velocity of Earth on June 21 and December 21, we can compare the distance Earth travels on those days. 

The degree of elongation of an elliptical orbit is called its eccentricity ( e ). Eccentricity is calculated by dividing the distance f from the center of an ellipse to one of the foci by half the long axis a : e = f / a e = f / a . When e = 0 e = 0 , the ellipse is a circle. 

The area of an ellipse is given by A = a b A = a b , where b is half the short axis. If you know the axes of Earth s orbit and the area Earth sweeps out in a given period of time, you can calculate the fraction of the year that has elapsed. 

[OL] Review the definitions of major and minor axes, semi-major and semi-minor axes, and distance f . The major axis is the length of the ellipse and passes through both foci. The minor axis is the width of the ellipse and is perpendicular to the major axis. The semi-major and semi-minor axes are half of the major and minor axes, respectively. Kepler s First Law 

At its closest approach, a moon comes within 200,000 km of the planet it orbits. At that point, the moon is 300,000 km from the other focus of its orbit, f 2 . The planet is focus f 1 of the moon s elliptical orbit. How far is the moon from the planet when it is 260,000 km from f 2 ? Strategy 

Show and label the ellipse that is the orbit in your solution. Picture the triangle f 1 m f 2 collapsed along the major axis and add up the lengths of the three sides. Find the length of the unknown side of the triangle when the moon is 260,000 km from f 2 . Solution 

Perimeter of f 1 m f 2 = 200 , 000 km + 100,000 km + 300,000 km = 600,000 km f 1 m f 2 = 200 , 000 km + 100,000 km + 300,000 km = 600,000 km . 

m f 1 = 600,000 km ( 100,000 km + 200,000 km ) = 240,000 km m f 1 = 600,000 km ( 100,000 km + 200,000 km ) = 240,000 km . Discussion 

The perimeter of triangle f 1 mf 2 must be constant because the distance between the foci does not change and Kepler s first law says the orbit is an ellipse. For any ellipse, the sum of the two sides of the triangle, which are f 1 m and mf 2 , is constant. 

Walk the students through the process of mentally collapsing the f 1 mf 2 at the end of the major axis to reveal what the three sides of the triangle f 1 mf 2 are equal to. Picture the sections of the string as the pencil approaches the major axis. This distance f 1 f 2 remains constant, f 1 m is the distance from f 1 to the end of the major axis, and mf 2 is f 1 m + f 1 f 2 . 

[OL] Have students relate eccentricity, distance between foci, and shape of orbit. 

[AL] Ask for examples of orbits with high eccentricity (comets, Pluto) and low eccentricity (moon, Earth). Kepler s Second Law 

[link] shows the major and minor axes of an ellipse. The semi-major and semi-minor axes are half of these, respectively. The major axis is the length of the ellipse, and the minor axis is the width of the ellipse. The semi-major axis is half the major axis, and the semi-minor axis is half the minor axis. 

The Earth s orbit is slightly elliptical, with a semi-major axis of 152 million km and a semi-minor axis of 147 million km. If Earth s period is 365.26 days, what area does an Earth-to-sun line sweep past in one day? Strategy 

Each day, the Earth sweeps past an equal-sized area, so we divide the total area by the number of days in a year to find the area swept past in one day. For total area use A = a b A = a b . Calculate A , the area inside Earth s orbit and divide by the number of days in a year (i.e., its period). Solution 

area per day = total area total number of days = a b 365 d = ( 1.47 10 8 km ) ( 1.52 10 3 km ) 365 d = 1.92 10 14 km 2 / d area per day = total area total number of days = a b 365 d = ( 1.47 10 8 km ) ( 1.52 10 3 km ) 365 d = 1.92 10 14 km 2 / d 

The area swept out in one day is thus 1.92 10 14 km 2 1.92 10 14 km 2 . Discussion 

The answer is based on Kepler s law, which states that a line from a planet to the sun sweeps out equal areas in equal times. 

Explain that this formula is easy to remember because it is similar to A = r 2 A = r 2 . Discuss Earth s eccentricity. Compare it with that of other planets, asteroids, or comets to further emphasize what defines a planet. Note that Earth has one of the least eccentric orbits and Mercury has the most eccentric orbit of the planets. 

[BL] Have the students memorized the value of ? 

[OL] [AL] What is the formula when a = b ? Is the formula familiar? 

[OL] Can the student verify this statement by rearranging the equation? Kepler s Third Law 

Kepler s third law states that the ratio of the squares of the periods of any two planets ( T 1 , T 2 ) is equal to the ratio of the cubes of their average orbital distance from the sun ( r 1 , r 2 ). Mathematically, this is represented by T 1 2 T 2 2 = r 1 3 r 2 3 T 1 2 T 2 2 = r 1 3 r 2 3 

From this equation, it follows that the ratio r 3 /T 2 is the same for all planets in the solar system. Later we will see how the work of Newton leads to a value for this constant. Kepler s Third Law 

Given that the moon orbits Earth each 27.3 d and that it is an average distance of 3.84 10 8 m 3.84 10 8 m from the center of Earth, calculate the period of an artificial satellite orbiting at an average altitude of 1500 km above Earth s surface. Strategy 

The period, or time for one orbit, is related to the radius of the orbit by Kepler s third law, given in mathematical form by T 1 2 T 2 2 = r 1 3 r 2 3 T 1 2 T 2 2 = r 1 3 r 2 3 . Let us use the subscript 1 for the moon and the subscript 2 for the satellite. We are asked to find T 2 . The given information tells us that the orbital radius of the moon is r 1 = 3.84 10 8 m r 1 = 3.84 10 8 m , and that the period of the moon is T 1 = 27.3 d T 1 = 27.3 d . The height of the artificial satellite above Earth s surface is given, so to get the distance r 2 from the center of Earth we must add the height to the radius of Earth (6380 km). This gives r 2 = 1500 km + 6380 km = 7880 km r 2 = 1500 km + 6380 km = 7880 km . Now all quantities are known, so T 2 can be found. Solution 

To solve for T 2 , we cross-multiply and take the square root, yielding 

T 2 2 = T 1 2 ( r 2 r 1 ) 3 ; T 2 = T 1 ( r 2 r 1 ) 3 2 T 2 = ( 27.3 d ) ( 24.0 h d ) ( 7880 km 3.84 10 5 km ) 3 2 = 1.93 h . T 2 2 = T 1 2 ( r 2 r 1 ) 3 ; T 2 = T 1 ( r 2 r 1 ) 3 2 T 2 = ( 27.3 d ) ( 24.0 h d ) ( 7880 km 3.84 10 5 km ) 3 2 = 1.93 h . Discussion 

This is a reasonable period for a satellite in a fairly low orbit. It is interesting that any satellite at this altitude will complete one orbit in the same amount of time. 

Remind the students that this only works when the satellites are small compared to the parent object and when both satellites orbit the same parent object. Practice Problems 

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Use the Check Your Answers questions to assess whether students master the learning objectives for this section. If students are struggling with a specific objective, the Check Your Answers will help identify which objective is causing the problem and direct students to the relevant content. Section Summary all satellites follow elliptical orbits the line from the satellite to the parent body sweeps out equal areas in equal time the radius cubed divided by the period squared is a constant for all satellites orbiting the same parent body Key Equations Kepler s third law T 1 2 T 2 2 = r 1 3 r 2 3 T 1 2 T 2 2 = r 1 3 r 2 3 eccentricity e = f a e = f a area of an ellipse A = a b A = a b semi-major axis of an ellipse a = ( r a + r p ) / 2 a = ( r a + r p ) / 2 semi-minor axis of an ellipse b = r a r p b = r a r p Concept Items 

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[link] Glossary aphelion closest distance between a planet and the sun (called apoapsis for other celestial bodies) Copernican model the model of the solar system where the sun is at the center of the solar system and all the planets orbit around it; this is also called the heliocentric model eccentricity a measure of the separation of the foci of an ellipse Kepler s laws of planetary motion three laws derived by Johannes Kepler that describe the properties of all orbiting satellites perihelion farthest distance between a planet and the sun (called periapsis for other celestial bodies) Ptolemaic model the model of the solar system where Earth is at the center of the solar system and the sun and all the planets orbit around it; this is also called the geocentric modelIntroduction Introduction In this chapter you will learn about: Kepler s Laws of Planetary Motion Newton s Law of Universal Gravitation and Einstein s Theory of General Relativity class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" 

Physics learning objectives come from 112.39 (c) Knowledge and Skills Johannes Kepler (left) showed how the planets move, and Isaac Newton (right) discovered that gravitational force caused them to move that way. (credits: (left) unknown, Public Domain; (right) Sir Godfrey Kneller, Public Domain) 

Contrast the type of work that each scientist did. Both were important and tackled difficult problems. Kepler found patterns in a mountain of data. Newton found the underlying cause of those patterns. 

What do a falling apple and the orbit of the moon have in common? You will learn in this chapter that each is caused by gravitational force. The motion of all celestial objects, in fact, is determined by the gravitational force, which depends on their mass and separation. 

Johannes Kepler discovered three laws of planetary motion that all orbiting planets and moons follow. Years later, Isaac Newton found these laws useful in developing his law of universal gravitation. This law relates gravitational force to the masses of objects and the distance between them. Many years later still, Albert Einstein showed there was a little more to the gravitation story when he published his theory of general relativity. 

Before students begin this chapter, it is useful to review these concepts: Using significant figures in calculations. Demonstrate how to use the proper number of significant figures when adding and multiplying. Review scientific notation as related to significant figures. Converting units: demonstrate how to convert from km/h to m/s. Review dimensional analysis. For example, N is equivalent to kg m/s 2 . Explain that metric units clearly distinguish between mass and weight, but that the commonly used English units do not. Calculating average: demonstrate how to average two numbers. Review manipulation of formulas so that they may be expressed in terms of the unknown. Review Newton s laws of motion.Introduction Introduction In this chapter, you will learn about: Linear Momentum, Force, and Impulse Conservation of Momentum Elastic and Inelastic Collisions NFC defensive backs Ronde Barber and Roy Williams along with linebacker Jeremiah Trotter gang tackle AFC running back Ladainian Tomlinson during the 2006 Pro Bowl in Hawaii. (Credit: United States Marine Corps.) 

Point out to the students how players often collide with each other while playing American football. How do these collisions affect the players? Does colliding into someone change your velocity? Does it change your mass? What about the force of collision? What does it depend on? Would it hurt more if a heavier person collided into you or a faster person? Tell students that in this chapter they will learn about momentum, its relation to force and about collisions. 

We know from everyday use of the word "momentum" that it is a tendency to continue on course in the same direction. Newscasters speak of sports teams or politicians gaining, losing, or maintaining the momentum to win. As we learned when studying about inertia (Newton's first law of motion), every object or system has inertia that is, a tendency for an object in motion to remain in motion or an object at rest to remain at rest. Mass is a useful variable that lets us quantify inertia. Momentum is mass in motion. 

Momentum is important because it is conserved in isolated systems; this fact is convenient for solving problems where objects collide. The magnitude of momentum grows with greater mass and/or speed. For example, look at the football players in the photograph ( [link] ). They collide and fall to the ground. During their collisions, momentum will play a large part. In this chapter, we will learn about momentum, the different types of collisions, and how to use momentum equations to solve collision problems. 

Before students begin this chapter, it would be useful to review these concepts: mass, inertia, Newton s laws of motion, angular motion, moment of inertia.Linear Momentum, Force, and Impulse Linear Momentum, Force, and Impulse Section Learning Objectives 

By the end of this section, you will be able to: Describe momentum, what can change momentum, impulse, and the impulse-momentum theorem Describe Newton s second law in terms of momentum Solve problems using the impulse-momentum theorem 

The learning objectives in this section will help your students master the following TEKS: (6) Science concepts. The student knows that changes occur within a physical system and applies the laws of conservation of energy and momentum. The student is expected to: (6C) : calculate the mechanical energy of, power generated within, impulse applied to, and momentum of a physical system Section Key Terms change in momentum impulse impulse momentum theorem linear momentum 

[BL] [OL] Review inertia and Newton s laws of motion. 

[AL] Start a discussion about movement and collision. Using the example of football players, point out that both the mass and the velocity of an object are important considerations in determining the impact of collisions. The direction as well as the magnitude of velocity is very important. Momentum, Impulse, and the Impulse-Momentum Theorem 

Linear momentum is the product of a system s mass and its velocity . In equation form, linear momentum p is p = m v p = m v 

You can see from the equation that momentum is directly proportional to the object s mass ( m ) and velocity ( v ). Therefore, the greater an object s mass or the greater its velocity, the greater its momentum. A large, fast-moving object has greater momentum than a smaller, slower object. 

Momentum is a vector and has the same direction as velocity v . Since mass is a scalar , when velocity is in a negative direction (i.e. opposite the direction of motion), the momentum will also be in a negative direction; and when velocity is in a positive direction, momentum will likewise be in a positive direction. The SI unit for momentum is kg m/s. 

Momentum is so important for understanding motion that it was called the quantity of motion by physicists such as Newton. Force influences momentum, and we can rearrange Newton s second law of motion to show the relationship between force and momentum. 

Recall our study of Newton s second law of motion ( F net = m a). Newton actually stated his second law of motion in terms of momentum: The net external force equals the change in momentum of a system divided by the time over which it changes. The change in momentum is the difference between the final and initial values of momentum. 

In equation form, this law is F net = p t F net = p t 

where F net is the net external force, p p is the change in momentum, and t t is the change in time. 

We can solve for p p by rearranging the equation F net = p t F net = p t 

to be p = F net t p = F net t 

F net t F net t is known as impulse and this equation is known as the impulse-momentum theorem . From the equation, we see that the impulse equals the average net external force multiplied by the time this force acts. It is equal to the change in momentum. The effect of a force on an object depends on how long it acts, as well as the strength of the force. Impulse is a useful concept because it quantifies the effect of a force. A very large force acting for a short time can have a great effect on the momentum of an object, such as the force of a racket hitting a tennis ball. A small force could cause the same change in momentum, but it would have to act for a much longer time. 

[OL] [AL] Explain that a large, fast-moving object has greater momentum than a smaller, slower object. This quality is called momentum. 

[BL] [OL] Review the equation of Newton s second law of motion. Point out the two different equations for the law. Newton s Second Law in Terms of Momentum 

When Newton s second law is expressed in terms of momentum, it can be used for solving problems where mass varies, since p = ( m v ) p = ( m v ) . In the more traditional form of the law that you are used to working with, mass is assumed to be constant. In fact, the form of Newton s second law in the form we re most familiar with is a special case of the law, where mass is constant. F net = m a F net = m a is actually derived from this equation: F net = p t F net = p t 

For the sake of understanding the relationship between Newton s second law in its two forms, let s recreate the derivation of F net = m a F net = m a from F net = p t F net = p t 

by substituting the definitions of acceleration and momentum. 

The change in momentum p p is given by p = ( m v ) p = ( m v ) 

If the mass of the system is constant, then ( m v ) = m v ( m v ) = m v 

By substituting m v m v for p p , Newton s second law of motion becomes F net = p t = m v t F net = p t = m v t 

for a constant mass. 

Because v t = a v t = a 

we can substitute to get the familiar equation F net = m a F net = m a 

when the mass of the system is constant. 

[BL] [OL] [AL] Show the two different forms of Newton s second law and how one can be derived from the other. 

We just showed how F net = m a F net = m a applies only when the mass of the system is constant. An example of when this formula would not apply would be a moving rocket that burns enough fuel to significantly change the mass of the rocket. In this case, you would need to use Newton s second law expressed in terms of momentum to account for the changing mass. Hand Movement and Impulse 

In this activity you will experiment with different types of hand motions to gain an intuitive understanding of the relationship between force, time and impulse. 1 ball 1 tub filled with water Try catching a ball while giving with the ball, pulling your hands toward your body. Next, try catching a ball while keeping your hands still. Hit water in a tub with your full palm. (Your full palm represents a swimmer doing a belly flop.) After the water has settled, hit the water again by diving your hand with your fingers first into the water. (Your diving hand represents a swimmer doing a dive.) Explain what happens in each case and why. 

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[OL] [AL] Discuss the impact one feels when one falls or jumps. List the factors that affect this impact. Engineering: Saving Lives Using the Concept of Impulse 

Cars over the past several decades have gotten much safer. Seat belts play a major role in automobile safety by preventing people from flying into the windshield in the event of a crash. Other safety features, such as airbags, are less visible or obvious, but are also effective at making auto crashes less deadly (see [link] ). Many of these other safety features make use of the concept of impulse from physics. Recall that impulse is the net force multiplied by the duration of time of the impact. This was expressed mathematically as p = F net t p = F net t . Vehicles have safety features like airbags and seatbelts installed. 

Airbags allow the net force on the occupants in the car to act over a much longer time when there is a sudden stop. The momentum change is the same for an occupant whether an air bag is deployed or not, but the force (to bring the occupant to a stop) will be much less if it acts over a larger time. By rearranging the equation for impulse to solve for force F net = p t , F net = p t , you can see how increasing t t as p p stays the same will decrease F net . (This is another example of an inverse relationship.) Similarly, a padded dashboard increases the time over which the force of impact acts, thereby reducing the force of impact. 

Cars today have many plastic components. One advantage of plastics is their lighter weight, which results in better gas mileage. Another advantage is that a car will crumple in a collision , especially in the event of a head-on collision. A longer collision time means the force on the occupants of the car will be less. Deaths during car races decreased dramatically when the rigid frames of racing cars were replaced with parts that could crumple or collapse in the event of an accident. 

[link] Solving Problems Using the Impulse-Momentum Theorem 

Talk about the different strategies to be used while solving problems. Make sure that students know the assumptions made in each equation regarding certain quantities being constant or some quantities being negligible. Calculating Momentum: A Football Player and a Football 

(a) Calculate the momentum of a 110 kg football player running at 8.00 m/s. (b) Compare the player s momentum with the momentum of a 0.410 kg football thrown hard at a speed of 25.00 m/s. Strategy 

No information is given about the direction of the football player or the football, so we can calculate only the magnitude of the momentum, p . (As usual, a symbol in italics represents magnitude.) In both parts of this example, the magnitude of momentum can be calculated directly from the definition of momentum: p = m v p = m v Solution for (a) 

To find the player s momentum, substitute the known values for the player s mass and speed into the equation. p player = ( 110 kg ) ( 8.00 m/s ) = 880 k g m / s p player = ( 110 kg ) ( 8.00 m/s ) = 880 k g m / s Solution for (b) 

To find the ball s momentum, substitute the known values for the ball s mass and speed into the equation. p ball = ( 0.410 kg ) ( 25.00 m/s ) = 10.25 k g m/s p ball = ( 0.410 kg ) ( 25.00 m/s ) = 10.25 k g m/s 

The ratio of the player s momentum to the ball s momentum is p player p ball = 880 10.3 = 85.9 p player p ball = 880 10.3 = 85.9 Discussion 

Although the ball has greater velocity, the player has a much greater mass. Therefore, the momentum of the player is about 86 times greater than the momentum of the football. Calculating Force: Venus Williams Racquet 

During the 2007 French Open, Venus Williams ( [link] ) hit the fastest recorded serve in a premier women s match, reaching a speed of 58 m/s (209 km/h). What was the average force exerted on the 0.057 kg tennis ball by Venus Williams racquet? Assume that the ball s speed just after impact was 58 m/s, the horizontal velocity before impact is negligible, and that the ball remained in contact with the racquet for 5.0 ms (milliseconds). Venus Williams playing in the 2013 US Open. (credit: Edwin Martinez, Flickr) Strategy 

Recall that Newton s second law stated in terms of momentum is F net = p t F net = p t 

As noted above, when mass is constant, the change in momentum is given by p = m v = m ( v f v i ) p = m v = m ( v f v i ) 

where v f is the final velocity and v i is the initial velocity. In this example, the velocity just after impact and the change in time are given, so after we solve for p p , we can use F net = p t F net = p t to find the force. Solution 

To determine the change in momentum, substitute the values for mass and the initial and final velocities into the equation above. 

p = m ( v f v i ) = ( 0 .057 kg ) ( 58 m/s 0 m/s ) = 3 .306 kg m/s 3 .3 kg m/s p = m ( v f v i ) = ( 0 .057 kg ) ( 58 m/s 0 m/s ) = 3 .306 kg m/s 3 .3 kg m/s 

Now we can find the magnitude of the net external force using F net = p t F net = p t : 

F net = p t = 3.306 5 10 3 = 661 N 660 N F net = p t = 3.306 5 10 3 = 661 N 660 N Discussion 

This quantity was the average force exerted by Venus Williams racquet on the tennis ball during its brief impact. This problem could also be solved by first finding the acceleration and then using F net = m a , but we would have had to do one more step. In this case, using momentum was a shortcut. Practice Problems 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment will help identify which objective is causing the problem and direct students to the relevant content. Section Summary Linear momentum ( momentum for short) is defined as the product of a system s mass multiplied by its velocity, p = m v . The SI unit for momentum is kg m/s. Newton s second law of motion in terms of momentum states that the net external force equals the change in momentum of a system divided by the time over which it changes, F net = p t F net = p t . Impulse is the average net external force multiplied by the time this force acts and impulse equals the change in momentum, p = F net t p = F net t . Forces are usually not constant over a period of time, so we use the average of the force over the time it acts. Key Equations impulse F net t F net t impulse momentum theorem p = F net t p = F net t linear momentum p = m v p = m v Newton s Second Law in terms of momentum F net = p t F net = p t Concept Items 

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[link] Glossary change in momentum the difference between the final and initial values of momentum; the mass times the change in velocity impulse average net external force multiplied by the time the force acts; equal to the change in momentum impulse momentum theorem the impulse (or change in momentum) is the product of the net external force and the time over which the force acts linear momentum the product of a system's mass and velocityNewton s Law of Universal Gravitation and Einstein s Theory of General Relativity Newton s Law of Universal Gravitation and Einstein s Theory of General Relativity Section Learning Objectives 

By the end of this section, you will be able to: Explain Newton s law of universal gravitation and compare it to Einstein s theory of general relativity Perform calculations using Newton s law of universal gravitation 

The learning objectives in this section will help your students master the following TEKS: (4D) : Calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects (5A) : Research and describe the historical development of the concepts of gravitational, electromagnetic, weak nuclear, and strong nuclear forces. (5B) : Describe and calculate how the magnitude of the gravitational force between two objects depends on their masses and the distance between their centers. Section Key Terms Einstein s theory of general relativity gravitational constant Newton s universal law of gravitation 

In this section, students will apply Newton s law of universal gravitation to objects close at hand and far off in the depths of the solar system. 

[BL] [OL] Compare the contributions of Kepler, Newton, and Einstein. Place them historically with dates. 

[AL] Ask if anyone knows the difference between special relativity and general relativity. Special relativity is a theory of spacetime and applies to observers moving at constant velocity. General relativity is a theory of gravity and applies to observers that are accelerating. General relativity is broader and includes special relativity, which was published first. Concepts Related to Newton s Law of Universal Gravitation 

Sir Isaac Newton was the first scientist to precisely define the gravitational force, and to show that it could explain both falling bodies and astronomical motions. See [link] . But Newton was not the first to suspect that the same force caused both our weight and the motion of planets. His forerunner, Galileo Galilei, had contended that falling bodies and planetary motions had the same cause. Some of Newton s contemporaries, such as Robert Hooke, Christopher Wren, and Edmund Halley, had also made some progress toward understanding gravitation. But Newton was the first to propose an exact mathematical form and to use that form to show that the motion of heavenly bodies should be conic sections circles, ellipses, parabolas, and hyperbolas. This theoretical prediction was a major triumph. It had been known for some time that moons, planets, and comets follow such paths, but no one had been able to propose an explanation of the mechanism that caused them to follow these paths and not others. The popular legend that Newton suddenly discovered the law of universal gravitation when an apple fell from a tree and hit him on the head has an element of truth in it. A more probable account is that he was walking through an orchard and wondered why all the apples fell in the same direction with the same acceleration. Great importance is attached to it because Newton s universal law of gravitation and his laws of motion answered very old questions about nature and gave tremendous support to the notion of underlying simplicity and unity in nature. Scientists still expect underlying simplicity to emerge from their ongoing inquiries into nature. 

[BL] [OL] Ask students if it really is obvious why all things fall straight down. Ask them to back up their reasons. Ask if the name Halley rings a bell. 

[OL] [AL] Ask if anyone thinks it is strange or even mysterious that a force can act at a distance across empty space. Ask the students to compare and contrast gravitational force with magnetic and electrostatic forces. Note how much force at a distance is like magic or having superpowers. 

The gravitational force is relatively simple. It is always attractive, and it depends only on the masses involved and the distance between them. Expressed in modern language, Newton s universal law of gravitation states that every object in the universe attracts every other object with a force that is directed along a line joining them. The force is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This attraction is illustrated by [link] . Gravitational attraction is along a line joining the centers of mass (CM) of the two bodies. The magnitude of the force on each body is the same, consistent with Newton s third law (action-reaction). 

For two bodies having masses m and M with a distance r between their centers of mass, the equation for Newton s universal law of gravitation is F = G m M r 2 F = G m M r 2 

where F is the magnitude of the gravitational force and G is a proportionality factor called the gravitational constant . G is a universal constant, meaning that it is thought to be the same everywhere in the universe. It has been measured experimentally to be G = 6.673 10 11 N m 2 /kg 2 G = 6.673 10 11 N m 2 /kg 2 . 

If a person has a mass of 60.0 kg, what would be the force of gravitational attraction on him at Earth s surface? G is given above, Earth s mass M is 5.97 10 24 kg, and the radius r of Earth is 6.38 10 6 m. Putting these values into Newton s universal law of gravitation gives F = G m M r 2 = ( 6.673 10 11 N m 2 kg 2 ) ( ( 60.0 kg ) ( 5.97 10 24 kg ) ( 6.38 10 6 m ) 2 ) = 584 N F = G m M r 2 = ( 6.673 10 11 N m 2 kg 2 ) ( ( 60.0 kg ) ( 5.97 10 24 kg ) ( 6.38 10 6 m ) 2 ) = 584 N 

We can check this result with the relationship: F = m g = ( 60 kg ) ( 9.8 m/s 2 ) = 588 N F = m g = ( 60 kg ) ( 9.8 m/s 2 ) = 588 N 

You may remember that g , the acceleration due to gravity, is another important constant related to gravity. By substituting g for a in the equation for Newton s second law of motion we get F = m g F = m g . Combining this with the equation for universal gravitation gives m g = G m M r 2 m g = G m M r 2 

Cancelling the mass m on both sides of the equation and filling in the values for the gravitational constant and mass and radius of the Earth, gives the value of g, which may look familiar. g = G M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 5.98 10 24 kg ( 6.38 10 6 m ) 2 ) = 9.80 m/s 2 g = G M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 5.98 10 24 kg ( 6.38 10 6 m ) 2 ) = 9.80 m/s 2 

This is a good point to recall the difference between mass and weight. Mass is the amount of matter in an object; weight is the force of attraction between the mass within two objects. Weight can change because g is different on every moon and planet. An object s mass m does not change but its weight m g can. 

[BL] [OL] Be sure no one is confusing G with g . 

[AL] Ask if anyone can explain why G is a universal constant that applies anywhere in the universe. Have them discuss the idea that the laws of physics are the same everywhere and that, at one time, people were not so sure about this. Emphasize that g is not a universal constant. Gravity and Orbits 

Move the sun, Earth, moon and space station in this simulation to see how it affects their gravitational forces and orbital paths. Visualize the sizes and distances between different heavenly bodies. Turn off gravity to see what would happen without it! Click here for the Gravity and Orbits simulation. 

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This is a good animation of the Earth-Moon-Sun system. Have the students try all of the buttons. This will show the paths of the Earth and the moon separately and together. Explain the gravitational force and velocity vectors. Point out the interesting shape of the moon s path around the sun. Explain that the velocity vector of the moon changes because sometimes the moon is traveling in the direction of Earth s orbit and sometimes it is traveling in the opposite direction. Take-Home Experiment: Falling Objects 

In this activity you will study the effects of mass and air resistance on the acceleration of falling objects. Make predictions (hypotheses) about the outcome of this experiment. Write them down to compare later with results. Four sheets of 8 - 1 / 2 11 8 - 1 / 2 11 -inch paper Take four identical pieces of paper. Crumple one up into a small ball. Leave one uncrumpled. Take the other two and crumple them up together, so that they make a ball of exactly twice the mass of the other crumpled ball. Now compare which ball of paper lands first when dropped simultaneously from the same height. Compare crumpled one-paper ball with crumpled two-paper ball. Compare crumpled one-paper ball with uncrumpled paper. 

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Ask for predictions (hypotheses) about the outcome of this experiment. Have the students write them down to compare later with results. 

It is possible to derive Kepler s third law from Newton s law of universal gravitation. Applying Newton s second law of motion to angular motion gives an expression for centripetal force, which can be equated to the expression for force in the universal gravitation equation. This expression can be manipulated to produce the equation for Kepler s third law. We saw earlier that the expression r 3 /T 2 is a constant for satellites orbiting the same massive object. The derivation of Kepler s third law from Newton s law of universal gravitation and Newton s second law of motion yields that constant: r 3 T 2 = G M 4 2 r 3 T 2 = G M 4 2 

where M is the mass of the central body about which the satellites orbit (for example, the sun in our solar system). The usefulness of this equation will be seen later. 

[OL] This equation illustrates the difference between Kepler s and Newton s work. Ask the students to explain why this is so. 

[AL] Ask the students what the attraction would be between two 10 kg balls separated by a distance of 1.0 m. Could they feel it? Later, ask them to calculate it after they have done some similar calculations. Solution: F = G m M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 10 kg 10 kg ( 1 m ) 2 ) = 6.67 10 9 N F = G m M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 10 kg 10 kg ( 1 m ) 2 ) = 6.67 10 9 N 

The universal gravitational constant G is determined experimentally. This definition was first done accurately in 1798 by English scientist Henry Cavendish (1731 1810), more than 100 years after Newton published his universal law of gravitation. The measurement of G is very basic and important because it determines the strength of one of the four forces in nature. Cavendish s experiment was very difficult because he measured the tiny gravitational attraction between two ordinary-sized masses (tens of kilograms at most) by using an apparatus like that in [link] . Remarkably, his value for G differs by less than 1% from the modern value. Cavendish used an apparatus like this to measure the gravitational attraction between two suspended spheres ( m ) and two spheres on a stand ( M ) by observing the amount of torsion (twisting) created in the fiber. The distance between the masses can be varied to check the dependence of the force on distance. Modern experiments of this type continue to explore gravity. Einstein s Theory of General Relativity 

Einstein s theory of general relativity explained some interesting properties of gravity not covered by Newton s theory. Einstein based his theory on the postulate that acceleration and gravity have the same effect and cannot be distinguished from each other. He concluded that light must fall in both a gravitational field and in an accelerating reference frame. [link] shows this effect (greatly exaggerated) in an accelerating elevator. In [link] (a) , the elevator accelerates upward in zero gravity. In [link] (b) , the room is not accelerating but is subject to gravity. The effect on light is the same: it falls downward in both situations. The person in the elevator cannot tell whether the elevator is accelerating in zero gravity or is stationary and subject to gravity. Thus, gravity affects the path of light, even though we think of gravity as acting between masses, while photons are massless. 

[BL] [OL] Ask the students to discuss the postulate. Can they relate the identity of gravity and acceleration to experience? (a) A beam of light emerges from a flashlight in an upward-accelerating elevator. Since the elevator moves up during the time the light takes to reach the wall, the beam strikes lower than it would if the elevator were not accelerated. (b) Gravity must have the same effect on light, since it is not possible to tell whether the elevator is accelerating upward or is stationary and acted upon by gravity. 

Einstein s theory of general relativity got its first verification in 1919 when starlight passing near the sun was observed during a solar eclipse. (See [link] .) During an eclipse, the sky is darkened and we can briefly see stars. Those on a line of sight nearest the sun should have a shift in their apparent positions. Not only was this shift observed, but it agreed with Einstein s predictions well within experimental uncertainties. This discovery created a scientific and public sensation. Einstein was now a folk hero as well as a very great scientist. The bending of light by matter is equivalent to a bending of space itself, with light following the curve. This is another radical change in our concept of space and time. It is also another connection that any particle with mass or energy (e.g., massless photons) is affected by gravity. This schematic shows how light passing near a massive body like the sun is curved toward it. The light that reaches the Earth then seems to be coming from different locations than the known positions of the originating stars. Not only was this effect observed, but the amount of bending was precisely what Einstein predicted in his general theory of relativity. 

To summarize the two views of gravity, Newton envisioned gravity as a tug of war along the line connecting any two objects in the universe. In contrast, Einstein envisioned gravity as a bending of space-time by mass. NASA gravity probe B 

NASA s Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein s general theory of relativity. The probe, shown in [link] was launched in 2004. It carried four ultra-precise gyroscopes designed to measure two effects hypothesized by Einstein s theory: The geodetic effect , which is the warping of space and time by the gravitational field of a massive body (in this case, Earth) The frame-dragging effect , which is the amount by which a spinning object pulls space and time with it as it rotates Artist concept of Gravity Probe B spacecraft in orbit around the Earth. (credit: NASA/MSFC) 

Both effects were measured with unprecedented precision. This was done by pointing the gyroscopes at a single star while orbiting Earth in a polar orbit. As predicted by relativity theory, the gyroscopes experienced very small, but measureable, changes in the direction of their spin caused by the pull of Earth s gravity. 

The principle investigator suggested imagining Earth spinning in honey. As Earth rotates it drags space and time with it as it would a surrounding sea of honey. 

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Explain that it is very exciting when a prediction of relativity theory is tested successfully. Some of the predictions were in doubt because they sounded so bizarre. Calculations Based on Newton s Law of Universal Gravitation 

When performing calculations using the equations in this chapter, use units of kilograms for mass, meters for distances, newtons for force, and seconds for time. 

The mass of an object is constant, but its weight varies with the strength of the gravitational field. This means the value of g varies from place to place in the universe. The relationship between force, mass, and acceleration from the second law of motion can be written in terms of g . F = m a = m g F = m a = m g 

In this case, the force is the weight of the object, which is caused by the gravitational attraction of the planet or moon on which the object is located. We can use this expression to compare weights of an object on different moons and planets. 

[BL] Check to make sure students are clear about the distinction between mass and weight. 

[OL] Recall the antics of astronauts of on the moon performed to illustrate the effect of a different value for g . Mass and Weight Clarification 

This video shows the mathematical basis of the relationship between mass and weight. The distinction between mass and weight are clearly explained. The mathematical relationship between mass and weight are shown mathematically in terms of the equation for Newton s law of universal gravitation and in terms of his second law of motion. 

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This may be a rather long-winded explanation of the mass-weight distinction, but it should drive home the point. 

Two equations involving the gravitational constant, G , are often useful. The first is Newton s equation: F = G m M r 2 F = G m M r 2 . Several of the values in this equation are either constants or easily obtainable. F is often the weight of an object on the surface of a large object with mass M , which is usually known. The mass of the smaller object, m , is often known, and G is a universal constant with the same value anywhere in the universe. This equation can be used to solve problems involving an object on or orbiting the Earth or other massive celestial object. Sometimes it is helpful to equate the right-hand side of the equation to m g and cancel the m on both sides. 

The equation r 3 T 2 = G M 4 2 r 3 T 2 = G M 4 2 is also useful for problems involving objects in orbit. Note that there is no need to know the mass of the object. Often, we know the radius r or the period T and want to find the other. If these are both known, we can use the equation to calculate the mass of a planet or star. Mass and Weight Clarification 

This video demonstrates calculations involving Newton s universal law of gravitation. 

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This video is a thorough demonstration of many of the calculations to be learned in this subsection. Change in g 

The value of g on the planet Mars is 3.71 m/s 2 . If you have a mass of 60.0 kg on Earth, what would be your mass on Mars? What would be your weight on Mars? Strategy 

Weight equals acceleration due to gravity times mass: W = m g W = m g . An object s mass is constant. Call acceleration due to gravity on Mars g M and weight on Mars W M . Solution 

Mass on Mars would be the same, 60 kg. 

W M = m g M = ( 60.0 kg ) ( 3.71 m/s 2 ) = 223 N W M = m g M = ( 60.0 kg ) ( 3.71 m/s 2 ) = 223 N Discussion 

The value of g on any planet depends on the mass of the planet and the distance from its center. If the material below the surface varies from point to point, the value of g will also vary slightly. 

This is a typical mass-weight calculation. Earth s g at the Moon 

Find the acceleration due to Earth s gravity at the distance of the moon. 

G = 6.67 10 11 N m 2 /kg 2 G = 6.67 10 11 N m 2 /kg 2 

Earth-moon distance = 3.84 10 8 m 3.84 10 8 m 

Earth s mass = 5.98 10 24 kg 5.98 10 24 kg Strategy 

Express the force of gravity in terms of g . F = W = m a = m g F = W = m a = m g 

Combine with the equation for universal gravitation: 

m g = m G M r 2 m g = m G M r 2 Solution 

Cancel m and substitute. 

g = G M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 5.98 10 24 kg ( 3.84 10 8 m ) 2 ) = 2.70 10 3 m/s 2 g = G M r 2 = ( 6.67 10 11 N m 2 kg 2 ) ( 5.98 10 24 kg ( 3.84 10 8 m ) 2 ) = 2.70 10 3 m/s 2 Discussion 

The value of g for the moon is 1.62 m/s 2 . Comparing this value to the answer, we see that Earth s gravitational influence on an object on the moon s surface would be insignificant. 

[BL] [OL] Review the meanings of all the symbols in these equations: F , G , m , M , r , T , and . 

[OL] [AL] Have the students memorize the values of G , g , and to three significant figures. Practice Problems 

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[link] Check Your Understanding 

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Use the Check Your Answers questions to assess whether students master the learning objectives for this section. If students are struggling with a specific objective, the Check Your Answers will help identify which objective is causing the problem and direct students to the relevant content. Section Summary Newton s law of universal gravitation provides a mathematical basis for gravitational force and Kepler s laws of planetary motion. Einstein s theory of general relativity shows that gravitational fields change the path of light and warp space and time. An object s mass is constant, but its weight changes when acceleration due to gravity, g , changes. Key Equations Newton s second law of motion F = m a = m g F = m a = m g Newton s universal law of gravitation F = G m M r 2 F = G m M r 2 acceleration due to gravity g = G M r 2 g = G M r 2 constant for satellites orbiting the same massive object r 3 T 2 = G M 4 2 r 3 T 2 = G M 4 2 Concept Items 

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Design an experiment to test whether magnetic force is inversely proportional to the square of distance. Gravitational, magnetic, and electrical fields all act at a distance, but do they all follow the inverse square law? One difference in the forces related to these fields is that gravity is only attractive, but the other two can repel as well. In general, the inverse square law says that force F equals a constant C divided by the distance between objects, d , squared: F = C / d 2 F = C / d 2 . 

Incorporate these materials into your design: Two strong, permanent bar magnets A spring scale that can measure small forces A short ruler calibrated in millimeters 

Use the magnets to study the relationship between attractive force and distance. What will be the independent variable? What will be the dependent variable? How will you measure each of these variables? If you plot the independent variable versus the dependent variable and the inverse square law is upheld, will the plot be a straight line? Explain. Which plot would be a straight line if the inverse square law were upheld? 

Magnets must be strong, such as neodymium magnets or cow magnets (ask a veterinarian). Suggest that they could either measure distance versus attractive force or repulsive force. Attractive force at various distances can be measured with the spring scale. Repulsive force could be measured by dropping the magnets into a transparent tube oriented so that they repel each other. The distance will be the distance between the magnets. Ask what the force will be. Ask how they could change the force and thereby change the distance. Test Prep Multiple Choice 

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[link] Glossary Einstein s theory of general relativity the theory that gravitational force results from the bending of spacetime by an object s mass gravitational constant the proportionality constant in Newton s law of universal gravitation Newton s universal law of gravitation states that gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.Conservation of Momentum Conservation of Momentum Section Learning Objectives Describe the law of conservation of momentum verbally and mathematically 

The learning objectives in this section will help your students master the following TEKS: (6) Science concepts. The student knows that changes occur within a physical system and applies the laws of conservation of energy and momentum. The student is expected to: (6C) : Calculate the mechanical energy of, power generated within, impulse applied to, and momentum of a physical system (6D) : Demonstrate and apply the laws of conservation of energy and conservation of momentum in one dimension; Section Key Terms angular momentum isolated system law of conservation of momentum 

In this section, students will apply what they have learned about momentum, impulse and force. 

[BL] [OL] Before students read the section, ask them what they understand by the word conservation . Have they come across it in any other law of physics? Conservation of Momentum 

It is important we realize that momentum is conserved during collisions, explosions, and other events involving objects in motion. To say that a quantity is conserved means that it is constant throughout the event. In the case of conservation of momentum, the total momentum in the system remains the same before and after the collision. 

You may have noticed that momentum was not conserved in this example , where forces acting on the objects produced large changes in momentum. Why is this? The systems of interest considered in those problems were not inclusive enough. If the systems were expanded to include more objects, then momentum would in fact be conserved in those sample problems. It is always possible to find a larger system where momentum is conserved, even though momentum changes for individual objects within the system. 

[OL] [AL] Caution students that momentum is only conserved when the entire system affected is taken into account. Explain isolated system. Ask students to give examples of isolated systems. Ask them is these are perfectly isolated. Would it be possible to have perfectly isolated systems on earth? 

For example, if a football player runs into the goalpost in the end zone, there will be a force on him that causes him to bounce backward. His momentum is obviously greatly changed, and considering only the football player, we would find that momentum is not conserved. However, the system can be expanded to contain the entire Earth! Surprisingly, the Earth also recoils conserving momentum because of the force applied to it through the goalpost. Of course, the effect on the Earth is not noticeable because Earth is so much more massive than the player, but the effect is real nevertheless. 

Next, consider what happens if the masses of two colliding objects are more similar than the masses of a football player and Earth for example, one car bumping into another, as shown in [link] . Both cars are coasting in the same direction when the lead car (labeled m 2 ) is bumped by the trailing car (labeled m 1 ). The only unbalanced force on each car is the force of the collision. (Assume that the effects due to friction are negligible.) Car 1 slows down as a result of the collision, losing some momentum, while car 2 speeds up and gains some momentum. If we choose the system to include both cars and assume that friction is negligible, then the momentum of the two-car system should remain constant. Now we will prove that the total momentum of the two-car system does in fact remain constant, and is therefore conserved. Car of mass m 1 moving with a velocity of v 1 bumps into another car of mass m 2 and velocity v 2 that it is following. As a result, the first car slows down to a velocity of v 1 and the second speeds up to a velocity of v 2 . The momentum of each car is changed, but the total momentum p tot of the two cars is the same before and after the collision (if you assume friction is negligible). 

Using the impulse-momentum theorem, the change in momentum of car 1 is given by p 1 = F 1 t p 1 = F 1 t 

where F 1 is the force on car 1 due to car 2, and t t is the time the force acts (the duration of the collision). 

Similarly, the change in momentum of car 2 is p 2 = F 2 t p 2 = F 2 t where F 2 is the force on car 2 due to car 1, and we assume the duration of the collision t t is the same for both cars. We know from Newton s third law that F 2 = F 1 , and so p 2 = F 1 t = p 1 p 2 = F 1 t = p 1 . 

Therefore, the changes in momentum are equal and opposite, and p 1 + p 2 = 0 p 1 + p 2 = 0 . 

Because the changes in momentum add to zero, the total momentum of the two-car system is constant. That is, p 1 + p 2 = constant p 1 + p 2 = constant p 1 + p 2 = p 1 + p 2 p 1 + p 2 = p 1 + p 2 

where p 1 and p 2 are the momenta of cars 1 and 2 after the collision. 

This result that momentum is conserved is true not only for this example involving the two cars, but momentum is conserved for any system where the net external force is zero (known as an isolated system ). The law of conservation of momentum states that for an isolated system with any number of objects in it, the total momentum is conserved. In equation form, the law of conservation of momentum for an isolated system is written as p tot = constant p tot = constant 

or p tot = p tot p tot = p tot 

where p tot is the total momentum (the sum of the momenta of the individual objects in the system) at a given time and p tot is the total momentum some time later. 

The conservation of momentum principle can be applied to systems as diverse as a comet striking Earth or a gas containing huge numbers of atoms and molecules. Conservation of momentum appears to be violated only when the net external force is not zero. But another larger system can always be considered in which momentum is conserved by simply including the source of the external force. For example, in the collision of two cars considered above, the two-car system conserves momentum while each one-car system does not. 

Momenta is the plural form of the word momentum. One object is said to have momentum, but two or more objects are said to have momenta. Angular Momentum in Figure Skating 

So far we ve covered linear momentum, which describes the inertia of objects traveling in a straight line. But we know that many objects in nature have a curved or circular path. Just as linear motion has linear momentum to describe its tendency to move forward, circular motion has the equivalent, angular momentum , to describe how rotational motion is carried forward. 

This is similar to how torque is analogous to force, angular acceleration is analogous to translational acceleration , and mr 2 is analogous to mass (or inertia). You may recall learning that the quantity mr 2 is called the rotational inertia or moment of inertia of a point mass m at a distance r from the center of rotation. 

We already know the equation for linear momentum, p = m v . Since angular momentum is analogous to linear momentum, the moment of inertia ( I ) is analogous to mass, and angular velocity ( ) is analogous to linear velocity, it makes sense that angular momentum ( L ) is defined as L = I L = I 

Angular momentum is conserved when the net external torque ( ) is zero, just as linear momentum is conserved when the net external force is zero. 

Figure skaters take advantage of the conservation of angular momentum, likely without even realizing it. In [link] , a figure skater is executing a spin. The net torque on her is very close to zero, because there is relatively little friction between her skates and the ice, and because the friction is exerted very close to the pivot point. (Both F and r are small, and so is negligibly small.) (a) An ice skater is spinning on the tip of her skate with her arms extended. In the next image, (b), her rate of spin increases greatly when she pulls in her arms. 

Consequently, she can spin for quite some time. She can do something else, too. She can increase her rate of spin by pulling her arms and legs in. Why does pulling her arms and legs in increase her rate of spin? The answer is that her angular momentum is constant, so that L = L . 

Expressing this equation in terms of the moment of inertia, I = I I = I 

where the primed quantities refer to conditions after she has pulled in her arms and reduced her moment of inertia. Because I is smaller, the angular velocity must increase to keep the angular momentum constant. This allows her to spin much faster without exerting any extra torque! 

A video is also available that shows a real figure skater executing a spin. It discusses the physics of spins in figure skating. 

You can demonstrate a similar exercise in class using a revolving stool or chair. Ask a student to sit on the stool with outstretched arms, holding some weight in each hand. Rotate the stool and once a good speed is achieved, ask him to bring his hands in close to his body. He will start spinning faster. 

[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment will help identify which objective is causing the problem and direct students to the relevant content. Section Summary The law of conservation of momentum is written p tot = constant or p tot = p tot (isolated system), where p tot is the initial total momentum and p tot is the total momentum some time later. In an isolated system the net external force is zero. Conservation of momentum applies only when the net external force is zero within the defined system. Key Equations law of conservation of momentum p tot = constant, or p tot = p tot conservation of momentum for two objects p 1 + p 2 = constant, or p 1 + p 2 = p 1 + p 2 angular momentum L = I Concept Items 

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[link] Glossary angular momentum the product of the moment of inertia and angular velocity isolated system system in which the net external force is zero law of conservation of momentum when the net external force is zero, the total momentum of the system is conserved or constantElastic and Inelastic Collisions Elastic and Inelastic Collisions Section Learning Objectives 

By the end of this section, you will be able to: Distinguish between elastic and inelastic collisions Solve collision problems by applying the law of conservation of momentum 

The learning objectives in this section will help your students master the following TEKS: (6) Science concepts. The student knows that changes occur within a physical system and applies the laws of conservation of energy and momentum. The student is expected to: (6C) : Calculate the mechanical energy of, power generated within, impulse applied to, and momentum of a physical system (6D) : Demonstrate and apply the laws of conservation of energy and conservation of momentum in one dimension Section Key Terms elastic collision inelastic collision point masses recoil Elastic and Inelastic Collisions 

When objects collide, they can either stick together or bounce off one another, remaining separate. In this section, we ll cover these two different types of collisions , first in one dimension and then in two dimensions. 

In an elastic collision , the objects separate after impact and don t lose any of their kinetic energy . Kinetic energy is the energy of motion and is covered in detail elsewhere. The law of conservation of momentum is very useful here, and it can be used whenever the net external force on a system is zero. [link] shows an elastic collision where momentum is conserved. The diagram shows a one-dimensional elastic collision between two objects. 

An animation of an elastic collision between balls can be seen by watching this video . It replicates the elastic collisions between balls of identical masses as well as balls of different masses. 

Perfectly elastic collisions can happen only with subatomic particles. Everyday observable examples of perfectly elastic collisions don t exist some kinetic energy is always lost, as it is converted into heat transfer due to friction. However, collisions between everyday objects are almost perfectly elastic when they occur with objects and surfaces that are nearly frictionless, such as with two steel blocks on ice. 

Now, to solve problems involving one-dimensional elastic collisions between two objects, we can use the equation for conservation of momentum. First, the equation for conservation of momentum for two objects in a one-dimensional collision is p 1 + p 2 = p 1 + p 2 ( F net = 0 ) p 1 + p 2 = p 1 + p 2 ( F net = 0 ) 

Substituting the definition of momentum p = m v for each initial and final momentum, we get m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 

where the primes (') indicate values after the collision; in some texts, you may see i for initial (before collision) and f for final (after collision). The equation assumes that the mass of each object does not change during the collision. Momentum: Ice Skater Throws a Ball 

This video covers an elastic collision problem in which we find the recoil velocity of an ice skater who throws a ball straight forward. (To clarify, Sal is using the equation 

m ball V ball + m skater V skater = m ball v ball + m skater v skater m ball V ball + m skater V skater = m ball v ball + m skater v skater .) 

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Now, let s turn to the second type of collision. An inelastic collision is one in which objects stick together after impact, and kinetic energy is not conserved. This lack of conservation means that the forces between colliding objects may convert kinetic energy to other forms of energy, such as potential energy or thermal energy. (The concepts of energy are discussed more thoroughly elsewhere). For inelastic collisions, kinetic energy may be lost in the form of heat. [link] shows an example of an inelastic collision. Two objects that have equal masses head toward each other at equal speeds and then stick together. The two objects come to rest after sticking together, conserving momentum but not kinetic energy after they collide. Some of the energy of motion gets converted to thermal energy, or heat. A one-dimensional inelastic collision between two objects. Momentum is conserved, but kinetic energy is not conserved. (a) Two objects of equal mass initially head directly toward each other at the same speed. (b) The objects stick together (a perfectly inelastic collision). In the case shown in this figure, the combined objects stop; this is not true for all inelastic collisions. 

Since the two objects stick together after collision, they move together at the same speed. This lets us simplify the conservation of momentum equation from m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 

to m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v 

for inelastic collisions, where v is the final velocity for both objects as they are stuck together (either in motion or at rest). 

[BL] [OL] Review the concept of internal energy. Ask students what they understand by the words elastic and inelastic. 

[AL] Start a discussion about collisions. Ask students to give examples of elastic and inelastic collisions. Introduction to Momentum 

This video reviews the definitions of momentum and impulse. It also covers an example of using conservation of momentum to solve a problem involving an inelastic collision between a car with constant velocity and a stationary truck. Note that Sal accidentally gives the unit for impulse as Joules; it is actually N s or k gm/s. 

[link] Ice Cubes and Elastic Collisions 

In this activity, you will observe an elastic collision by sliding an ice cube into another ice cube on a smooth surface, so that a negligible amount of energy is converted to heat. Several ice cubes (The ice must be in the form of cubes) A smooth surface Find a few ice cubes that are about the same size and a smooth kitchen tabletop or a table with a glass top. Place the ice cubes on the surface several centimeters away from each other. Flick one ice cube toward a stationary ice cube and observe the path and velocities of the ice cubes after the collision. (Try to avoid edge-on collisions and collisions with rotating ice cubes.) Explain the speeds and directions of the ice cubes using momentum. 

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Here s a trick for remembering which collisions are elastic and which are inelastic: Elastic is a bouncy material, so when objects bounce off one another in the collision and separate, it is an elastic collision. When they don t, the collision is inelastic. Solving Collision Problems 

The Khan Academy videos referenced in this section show examples of elastic and inelastic collisions in one dimension. In one-dimensional collisions, the incoming and outgoing velocities are all along the same line. But what about collisions, such as those between billiard balls, in which objects scatter to the side? These are two-dimensional collisions, and just as we did with two-dimensional forces, we will solve these problems by first choosing a coordinate system and separating the motion into its x and y components. 

One complication with two-dimensional collisions is that the objects might rotate before or after their collision. For example, if two ice skaters hook arms as they pass each other, they will spin in circles. We will not consider such rotation until later, and so for now, we arrange things so that no rotation is possible. To avoid rotation, we consider only the scattering of point masses that is, structureless particles that cannot rotate or spin. 

We start by assuming that F net = 0, so that momentum p is conserved. The simplest collision is one in which one of the particles is initially at rest. The best choice for a coordinate system is one with an axis parallel to the velocity of the incoming particle, as shown in [link] . Because momentum is conserved, the components of momentum along the x - and y -axes ( p x and p y ) will also be conserved. With the chosen coordinate system, p y is initially zero and p x is the momentum of the incoming particle. A two-dimensional collision with the coordinate system chosen so that m 2 is initially at rest and v 1 is parallel to the x -axis. 

Now, we will take the conservation of momentum equation, p 1 + p 2 = p 1 + p 2 and break it into its x and y components. 

Along the x -axis, the equation for conservation of momentum is p 1x + p 2x = p 1x + p 2x p 1x + p 2x = p 1x + p 2x 

In terms of masses and velocities, this equation is m 1 v 1 x + m 2 v 2 x = m 1 v 1 x + m 2 v 2 x m 1 v 1 x + m 2 v 2 x = m 1 v 1 x + m 2 v 2 x 

But because particle 2 is initially at rest, this equation becomes m 1 v 1 x = m 1 v 1 x + m 2 v 2 x m 1 v 1 x = m 1 v 1 x + m 2 v 2 x 

The components of the velocities along the x -axis have the form v cos . Because particle 1 initially moves along the x -axis, we find v 1 x = v 1 . Conservation of momentum along the x -axis gives the following equation: m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 

where 1 1 and 2 2 are as shown in [link] . 

Along the y -axis, the equation for conservation of momentum is p 1 y + p 2 y = p 1 y + p 2 y p 1 y + p 2 y = p 1 y + p 2 y 

or m 1 v 1 y + m 2 v 2 y = m 1 v 1 y + m 2 v 2 y m 1 v 1 y + m 2 v 2 y = m 1 v 1 y + m 2 v 2 y 

But v 1 y is zero, because particle 1 initially moves along the x -axis. Because particle 2 is initially at rest, v 2 y is also zero. The equation for conservation of momentum along the y -axis becomes 0 = m 1 v 1 y + m 2 v 2 y 0 = m 1 v 1 y + m 2 v 2 y 

The components of the velocities along the y -axis have the form v sin . Therefore, conservation of momentum along the y -axis gives the following equation: 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 

Review conservation of momentum and the equations derived in the previous sections of this chapter. Say that in the problems of this section, all objects are assumed to be point masses. Explain point masses. Collision Lab 

In this simulation, you will investigate collisions on an air hockey table. Place checkmarks next to the momentum vectors and momenta diagram options. Experiment with changing the masses of the balls and the initial speed of ball 1. How does this affect the momentum of each ball? What about the total momentum? Next, experiment with changing the elasticity of the collision. You will notice that collisions have varying degrees of elasticity, ranging from perfectly elastic to perfectly inelastic. Click here for the simulation 

[link] Calculating Velocity: Inelastic Collision of a Puck and a Goalie 

Find the recoil velocity of a 70.0 kg ice hockey goalie who catches a 0.150-kg hockey puck slapped at him at a velocity of 35.0 m/s. Assume that the goalie is at rest before catching the puck, and friction between the ice and the puck-goalie system is negligible (see [link] ). An ice hockey goalie catches a hockey puck and recoils backward in an inelastic collision. Strategy 

Momentum is conserved because the net external force on the puck-goalie system is zero. Therefore, we can use conservation of momentum to find the final velocity of the puck and goalie system. Note that the initial velocity of the goalie is zero and that the final velocity of the puck and goalie are the same. Solution 

For an inelastic collision, conservation of momentum is m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v 

where v is the velocity of both the goalie and the puck after impact. Because the goalie is initially at rest, we know v 2 = 0. This simplifies the equation to m 1 v 1 = ( m 1 + m 2 ) v m 1 v 1 = ( m 1 + m 2 ) v 

Solving for v yields v = ( m 1 m 1 + m 2 ) v 1 v = ( m 1 m 1 + m 2 ) v 1 

Entering known values in this equation, we get v = ( 0.150 kg 70.0 kg + 0.150 kg ) ( 35 m/s ) = 7.48 10 2 m/s v = ( 0.150 kg 70.0 kg + 0.150 kg ) ( 35 m/s ) = 7.48 10 2 m/s Discussion 

This recoil velocity is small and in the same direction as the puck s original velocity, as we might expect. Calculating Final Velocity: Elastic Collision of Two Carts 

Two hard steel carts collide head-on and then ricochet off each other in opposite directions on a frictionless surface (see [link] ). Cart 1 has a mass of 0.350 kg and an initial velocity of 2.00 m/s. Cart 2 has a mass of 0.500 kg and an initial velocity of 0.500 m/s. After the collision, cart 1 recoils with a velocity of 4.00 m/s. What is the final velocity of cart 2? Two carts collide with each other in an elastic collision. Strategy 

Since the track is frictionless, F net = 0 and we can use conservation of momentum to find the final velocity of cart 2. Solution 

As before, the equation for conservation of momentum for a one-dimensional elastic collision in a two-object system is m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 

The only unknown in this equation is v 2 . Solving for v 2 and substituting known values into the previous equation yields v 2 = m 1 v 1 + m 2 v 2 m 1 v 1 m 2 = ( 0 .350 kg ) ( 2 .00 m/s ) + ( 0 .500 kg ) ( 0 .500 m/s ) ( 0 .350 kg ) ( 4 .00 m/s ) 0 .500 kg = 3 .70 m/s v 2 = m 1 v 1 + m 2 v 2 m 1 v 1 m 2 = ( 0 .350 kg ) ( 2 .00 m/s ) + ( 0 .500 kg ) ( 0 .500 m/s ) ( 0 .350 kg ) ( 4 .00 m/s ) 0 .500 kg = 3 .70 m/s Discussion 

The final velocity of cart 2 is large and positive, meaning that it is moving to the right after the collision. Calculating Final Velocity in a Two-Dimensional Collision 

Suppose the following experiment is performed ( [link] ). An object of mass 0.250 kg ( m 1 ) is slid on a frictionless surface into a dark room, where it strikes an initially stationary object of mass 0.400 kg ( m 2 ). The 0.250 kg object emerges from the room at an angle of 45.0 with its incoming direction. The speed of the 0.250 kg object is originally 2.00 m/s and is 1.50 m/s after the collision. Calculate the magnitude and direction of the velocity ( v 2 and 2 2 ) of the 0.400 kg object after the collision. The incoming object of mass m 1 is scattered by an initially stationary object. Only the stationary object s mass m 2 is known. By measuring the angle and speed at which the object of mass m 1 emerges from the room, it is possible to calculate the magnitude and direction of the initially stationary object s velocity after the collision. Strategy 

Momentum is conserved because the surface is frictionless. We chose the coordinate system so that the initial velocity is parallel to the x -axis, and conservation of momentum along the x - and y -axes applies. 

Everything is known in these equations except v 2 and , which we need to find. We can find two unknowns because we have two independent equations: the equations describing the conservation of momentum in the x and y directions. Solution 

First, we ll solve both conservation of momentum equations ( m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 and 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 ) for v 2 sin 2 2 . 

For conservation of momentum along x-axis, let s substitute sin 2 2 /tan 2 2 for cos 2 2 so that terms may cancel out later on. (This comes from rearranging the definition of the trigonometric identity tan = sin /cos ). This gives us m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 sin 2 tan 2 m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 sin 2 tan 2 

Solving for v 2 sin 2 2 yields: v 2 sin 2 = ( m 1 v 1 m 1 v 1 cos 1 ) ( tan 2 ) m 2 v 2 sin 2 = ( m 1 v 1 m 1 v 1 cos 1 ) ( tan 2 ) m 2 

For conservation of momentum along y -axis, solving for v 2 sin 2 2 yields: v 2 sin 2 = ( m 1 v 1 sin 1 ) m 2 v 2 sin 2 = ( m 1 v 1 sin 1 ) m 2 

Since both equations equal v 2 sin 2 2 , we can set them equal to one another, yielding ( m 1 v 1 m 1 v 1 cos 1 ) ( tan 2 ) m 2 = ( m 1 v 1 sin 1 ) m 2 ( m 1 v 1 m 1 v 1 cos 1 ) ( tan 2 ) m 2 = ( m 1 v 1 sin 1 ) m 2 

Solving this equation for tan 2 2 , we get tan 2 = v 1 sin 1 v 1 cos 1 v 1 tan 2 = v 1 sin 1 v 1 cos 1 v 1 

Entering known values into the previous equation gives tan 2 = ( 1.50 ) ( 0.707 ) ( 1.50 ) ( 0.707 ) 2.00 = 1.129 tan 2 = ( 1.50 ) ( 0.707 ) ( 1.50 ) ( 0.707 ) 2.00 = 1.129 

Therefore, 2 = tan 1 ( 1.129 ) = 312 0 2 = tan 1 ( 1.129 ) = 312 0 

Since angles are defined as positive in the counterclockwise direction, m 2 is scattered to the right. 

We ll use the conservation of momentum along the y-axis equation to solve for v 2 . v 2 = m 1 m 2 v 1 sin 1 sin 2 v 2 = m 1 m 2 v 1 sin 1 sin 2 

Entering known values into this equation gives v 2 = ( 0.250 ) ( 0.400 ) ( 1.50 ) ( 0.7071 0.7485 ) v 2 = ( 0.250 ) ( 0.400 ) ( 1.50 ) ( 0.7071 0.7485 ) 

Therefore, v 2 = 0.886 m/s . v 2 = 0.886 m/s . Discussion 

Either equation for the x - or y -axis could have been used to solve for v 2 , but the equation for the y -axis is easier because it has fewer terms. Practice Problems 

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[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the assessment will help identify which objective is causing the problem and direct students to the relevant content. Section Summary If objects separate after impact, the collision is elastic, and if they stick together, the collision is inelastic. Kinetic energy is conserved in an elastic collision, but not in an inelastic collision. The approach to two-dimensional collisions is to choose a convenient coordinate system and break the motion into components along perpendicular axes. Choose a coordinate system with the x -axis parallel to the velocity of the incoming particle. Two-dimensional collisions of point masses where mass 2 is initially at rest conserve momentum along the initial direction of mass 1 (the x -axis) and along the direction perpendicular to the initial direction (the y -axis). Point masses are structureless particles that cannot spin. Key Equations conservation of momentum in an elastic collision m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 , m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 , conservation of momentum in an inelastic collision m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v m 1 v 1 + m 2 v 2 = ( m 1 + m 2 ) v conservation of momentum along x-axis for 2D collisions m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 m 1 v 1 = m 1 v 1 cos 1 + m 2 v 2 cos 2 conservation of momentum along y-axis for 2D collisions 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 0 = m 1 v 1 sin 1 + m 2 v 2 sin 2 Concept Items 

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[link] Performance Task You will need: balls of different weights a ruler or wooden strip some books a paper cup 

Make an inclined plane by resting one end of a ruler on a stack of books. Place a paper cup on the other end. Roll a ball from the top of the ruler so that it hits the paper cup. Measure the displacement of the paper cup due to the collision. Now use increasingly heavier balls for this activity and see how that affects the displacement of the cup. Plot a graph of mass vs displacement. Now repeat the same activity, but this time, instead of using different balls, change the incline of the ruler by varying the height of the stack of books. This will give you different velocities of the ball. See how this affects the displacement of the paper cup. Test Prep Multiple Choice 

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[link] Glossary elastic collision collision in which objects separate after impact and kinetic energy is conserved inelastic collision collision in which objects stick together after impact and kinetic energy is not conserved point masses structureless particles that cannot rotate or spin recoil backward movement of an object caused by the transfer of momentum from another object in a collisionWork, Power, and the Work Energy Theorem Work, Power, and the Work Energy Theorem Section Learning Objectives 

By the end of this section, you will be able to: Describe and apply the work energy theorem Describe and calculate work and power 

The learning objectives in this section will help your students master the following TEKS: (6A) : Describe and apply the work energy theorem. (6C) : Describe and calculate work and power. Section Key Terms energy gravitational potential energy joule kinetic energy mechanical energy potential energy power watt work work energy theorem 

In this section, students learn how work determines changes in kinetic energy and that power is the rate at which work is done. 

[BL] [OL] Review understanding of mass, velocity, and acceleration due to gravity. Define the general definitions of the words potential and kinetic . 

[AL] [AL] Remind students of the equation W = P E e = f m g W = P E e = f m g . Point out that acceleration due to gravity is a constant, therefore PE e that results from work done by gravity will also be constant. Compare this to acceleration due to other forces, such as applying muscles to lift a rock, which may not be constant. The Work Energy Theorem 

In physics, the term work has a very specific definition. Work is application of force, f f , to move an object over a distance, d , in the direction that the force is applied. Work, W , is described by the equation: W = f d W = f d 

Some things that we typically consider to be work are not work in the scientific sense of the term. Let s consider a few examples. Think about why each of the following statements is true. Homework is not work. Lifting a rock upwards off the ground is work. Carrying a rock in a straight path across the lawn at a constant speed is not work. 

The first two examples are fairly simple. Homework is not work because objects are not being moved over a distance. Lifting a rock up off the ground is work because the rock is moving in the direction that force is applied. The last example is less obvious. Recall from the laws of motion that force is not required to move an object at constant velocity. Therefore, while some force may be applied to keep the rock up off the ground, no net force is applied to keep the rock moving forward at constant velocity. 

[BL] [OL] Explain that, when this theorem is applied to an object that is initially at rest and then accelerates, the 1 2 m v 1 2 1 2 m v 1 2 term equals zero. 

[OL] [AL] Work is measured in joules and W = f d W = f d . Force is measured in newtons and distance in meters, so joules are equivalent to newton-meters ( N m ) ( N m ) 

Work and energy are closely related. When you do work to move an object, you change the object s energy. You (or an object) also expend energy to do work. In fact, energy can be defined as the ability to do work. Energy can take a variety of different forms, and one form of energy can transform to another. In this chapter we will be concerned with mechanical energy , which comes in two forms: kinetic energy and potential energy . Kinetic energy is also called energy of motion. A moving object has kinetic energy. Potential energy, sometimes called stored energy, comes in several forms. Gravitational potential energy is the stored energy an object has as a result of its position above Earth s surface (or another object in space). A roller coaster car at the top of a hill has gravitational potential energy. 

Let s examine how doing work on an object changes the object s energy. If we apply force to lift a rock off the ground, we increase the rock s potential energy, PE . If we drop the rock, the force of gravity increases the rock s kinetic energy as the rock moves downward until it hits the ground. 

The force we exert to lift the rock is equal to its weight, w , which is equal to its mass, m , multiplied by acceleration due to gravity, g : f = w = m g f = w = m g 

The work we do on the rock equals the force we exert multiplied by the distance, d , that we lift the rock. The work we do on the rock also equals the rock s gain in gravitational potential energy, PE e : W = P E e = f m g W = P E e = f m g 

Kinetic energy depends on the mass of an object and its velocity, v : K E = 1 2 m v 2 K E = 1 2 m v 2 

When we drop the rock the force of gravity causes the rock to fall, giving the rock kinetic energy. When work done on an object increases only its kinetic energy, then the net work equals the change in the value of the quantity 1 2 m v 2 1 2 m v 2 . This is a statement of the work energy theorem , which is expressed mathematically as: W = K E = 1 2 m v 2 2 1 2 m v 1 2 W = K E = 1 2 m v 2 2 1 2 m v 1 2 

The subscripts 2 and 1 indicate the final and initial velocity, respectively. This theorem was proposed and successfully tested by James Joule, shown in [link] . 

Does the name Joule sound familiar? The joule (J) is the metric unit of measurement for both work and energy. The measurement of work and energy with the same unit reinforces the idea that work and energy are related and can be converted into one another. 1.0 J = 1.0 N m, the units of force multiplied by distance. 1.0 N = 1.0 k m/s 2 , so 1.0 J = 1.0 k m 2 /s 2 . Analyzing the units of the term (1/2) m v 2 will produce the same units for joules. The joule is named after physicist James Joule (1818 1889). (credit: C. H. Jeens, Wikimedia Commons) Work and Energy 

This video explains the work energy theorem and discusses how work done on an object increases the object s KE. 

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Repeat the information on kinetic and potential energy discussed earlier in the section. Have the students distinguish between and understand the two ways of increasing the energy of an object (1) applying a horizontal force to increase KE and (2) applying a vertical force to increase PE. Calculations Involving Work and Power 

In applications that involve work, we are often interested in how fast the work is done. For example, in roller coaster design, the amount of time it takes to lift a roller coaster car to the top of the first hill is an important consideration. Taking a half hour on the ascent will surely irritate riders and decrease ticket sales. Let s take a look at how to calculate the time it takes to do work. 

Recall that a rate can be used to describe a quantity, such as work, over a period of time. Power is the rate at which work is done. In this case, rate means "per unit of time." Power is calculated by dividing the work done by the time it took to do the work: P = W t P = W t 

Let s consider an example that can help illustrate the differences among work, force, and power. Suppose the woman in [link] lifting the TV with a pulley gets the TV to the fourth floor in two minutes, and the man carrying the TV up the stairs takes five minutes to arrive at the same place. They have done the same amount of work ( f d ) ( f d ) on the TV, because they have moved the same mass over the same vertical distance, which requires the same amount of upward force. However, the woman using the pulley has generated more power. This is because she did the work in a shorter amount of time, so the denominator of the power formula, t , is smaller. (For simplicity s sake, we will leave aside for now the fact that the man climbing the stairs has also done work on himself.) No matter how you move a TV to the fourth floor, the amount of work performed and the potential energy gain are the same. 

Power can be expressed in units of watts (W). This unit can be used to measure power related to any form of energy or work. You have most likely heard the term used in relation to electrical devices, especially light bulbs. Multiplying power by time gives the amount of energy. Electricity is sold in kilowatt-hours because that equals the amount of electrical energy consumed. 

The watt unit was named after James Watt (1736 1819) (see [link] ). He was a Scottish engineer and inventor who discovered how to coax a lot more power out of steam engines. Is James Watt thinking about watts? (credit: Carl Frederik von Breda, Wikimedia Commons) 

[BL] [OL] Review the concept that work changes the energy of an object or system. Review the units of work, energy, force, and distance. Use the equations for mechanical energy and work to show what is work and what is not. Make it clear why holding something off the ground or carrying something over a level surface is not work in the scientific sense. 

[OL] Ask the students to use the mechanical energy equations to explain why each of these is or is not work. Ask them to provide more examples until they understand the difference between the scientific term work and a task that is simply difficult but not literally work (in the scientific sense). 

[BL] [OL] Stress that power is a rate and that rate means "per unit of time." In the metric system this unit is usually seconds. End the section by clearing up any misconceptions about the distinctions between force, work, and power. 

[AL] Explain relationships between the units for force, work, and power. If W = f d W = f d and work can be expressed in J, then P = W t = f d t P = W t = f d t so power can be expressed in units of N m s N m s 

Also explain that we buy electricity in kilowatt-hours because, when power is multiplied by time, the time units cancel, which leaves work or energy. Watt s Steam Engine 

James Watt did not invent the steam engine, but by the time he was done tinkering with it, it was a lot more useful. The first steam engines were not only inefficient, they only produced a back and forth, or reciprocal , motion. This was natural because pistons move in and out as the pressure in the chamber changes. This limitation was okay for simple tasks like pumping water or mashing potatoes, but did not work so well for moving a train. Watt was able build a steam engine that converted reciprocal motion to circular motion. With that one innovation, the industrial revolution was off and running. The world would never be the same. One of Watt's steam engines is shown in [link] . The video that follows the figure explains the importance of the steam engine in the industrial revolution. A late version of the Watt steam engine. (credit: Nehemiah Hawkins, Wikimedia Commons) 

Initiate a discussion on the historical significance of suddenly increasing the amount of power available to industry and transportation. Have students consider the fact that the speed of transportation increased roughly tenfold. Changes in how goods were manufactured were just as great. Ask students how they think the resulting changes in lifestyle compare to more recent changes brought about by innovations such as air travel and the Internet. Watt's Role in the Industrial Revolution 

This video demonstrates how all those watts that resulted from Watt's inventions helped make the industrial revolution possible and got England in on the ground floor of this new historical era. 

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Before proceeding, be sure you understand the distinctions among force, work, energy, and power. Force exerted on an object over a distance does work. Work can increase energy, and energy can do work. Power is the rate at which work is done. Applying the Work Energy Theorem 

An ice skater with a mass of 50 kg is gliding across the ice at a speed of 8 m/s when her friend comes up from behind and gives her a push, causing her speed to increase to 12 m/s. How much work did the friend do on the skater? Strategy 

The work energy theorem can be applied to the problem. Write the equation for the theorem and simplify it if possible. W = KE = 1 2 m v 2 2 1 2 m v 1 2 W = KE = 1 2 m v 2 2 1 2 m v 1 2 Simplify to W = 1 2 m ( v 2 2 v 1 2 ) Simplify to W = 1 2 m ( v 2 2 v 1 2 ) Solution 

Identify the variables: m = 50 kg, v 2 = 12 m s v 2 = 12 m s , and v 1 = 8 m s v 1 = 8 m s . 

Substitute: W = 1 2 50 ( 12 2 8 2 ) = 2 , 000 J W = 1 2 50 ( 12 2 8 2 ) = 2 , 000 J Discussion 

Work done on an object or system increases its energy. In this case, the increase is to the skater s kinetic energy. It follows that the increase in energy must be the difference in KE before and after the push. 

This problem illustrates a general technique for approaching problems that require you to apply formulas: identify the unknown and the known variables, express the unknown variables in terms of the known variables, and then enter all the known values. 

Identify the three variables and choose the relevant equation. Distinguish between initial and final velocity and pay attention to the minus sign 

Identify the variables: m = 50 kg, v 2 = 12 m s v 2 = 12 m s , and v 1 = 8 m s v 1 = 8 m s 

Substitute: W = 1 2 50 ( 12 2 8 2 ) = 2 , 000 J W = 1 2 50 ( 12 2 8 2 ) = 2 , 000 J Practice Problems 

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Use Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which one and direct students to the relevant content. Section Summary Doing work on a system or object changes its energy. The work energy theorem states that an amount of work that changes the velocity of an object is equal to the change in kinetic energy of that object.The work energy theorem states that an amount of work that changes the velocity of an object is equal to the change in kinetic energy of that object. Power is the rate at which work is done. Key Equations equation for work W = f d W = f d force f = w = m g f = w = m g work equivalencies W = P E e = f m g W = P E e = f m g kinetic energy K E = 1 2 m v 2 K E = 1 2 m v 2 work energy theorem W = KE = 1 2 m v 2 2 1 2 m v 1 2 W = KE = 1 2 m v 2 2 1 2 m v 1 2 power P = W t P = W t Concept Items 

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[link] Glossary energy the ability to do work gravitational potential energy energy acquired by doing work against gravity joule the metric unit for work and energy; equal to 1 newton meter (N m) kinetic energy energy of motion mechanical energy kinetic or potential energy power the rate at which work is done potential energy stored energy watt the metric unit of power; equivalent to joules per second work force multiplied by distance work energy theorem states that the net work done on a system equals the change in kinetic energyIntroduction Introduction In this chapter, you will learn about: Work, Power, and the Work Energy Theorem Mechanical Energy and the Conservation of Energy Simple Machines class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" 

Physics learning objectives come from 112.39 (c) Knowledge and Skills People on a roller coaster experience thrills caused by changes in types of energy. (credit: Jonrev, Wikimedia Commons) 

Before students begin this chapter, it is useful to review these concepts: Using significant figures in calculations. Demonstrate how to use the proper number of significant figures when adding and multiplying. Converting units. Demonstrate how to convert from km/h to m/s. Calculating average. Demonstrate how to average two numbers by dividing their sum by two. Commonly used terms. Explain that constant means "unchanging," so constant speed refers to speed that is not changing. Explain that initial means "starting," so initial time is the time at which the action of a problem begins. Explain that an object that is not moving is often described in physics as being at rest. Review the difference between mass and weight. Review the force of gravity and acceleration due to gravity. 

Initiate a discussion about how speed changes at different points in a roller coaster ride. Also discuss acceleration and deceleration. Ask students to try to describe the physical experience of these changes. 

Roller coasters have provided thrills for daring riders around the world since the nineteenth century. Inventors of roller coasters used simple physics to build the earliest examples using railroad tracks on mountainsides and old mines. Modern roller coaster designers use the same basic laws of physics to create the latest amusement park favorites. Physics principles are used to engineer the machines that do the work to lift a roller coaster car up its first big incline before it is set loose to roll. Engineers also have to understand the changes in the car s energy that keep it speeding over hills, through twists, turns, and even loops. 

What exactly is energy? How changes in force and energy move objects like roller coaster cars? How can machines help us do work? In this chapter, you will discover the answers to these questions as you learn about work, energy, and simple machines.Mechanical Energy and the Conservation of Energy Mechanical Energy and the Conservation of Energy Section Learning Objectives 

By the end of this section, you will be able to: Explain the law of conservation of energy in terms of kinetic and potential energy Perform calculations related to kinetic and potential energy. Apply the law of conservation of energy 

The learning objectives in this section will help your students master the following TEKS: (6B) : investigate examples of kinetic and potential energy and their transformations. (6D) : demonstrate and apply the laws of conservation of energy and conservation of momentum in one dimension. Section Key Term law of conservation of energy 

[BL] [OL] Begin by distinguishing mechanical energy from other forms of energy. Explain how the general definition of energy as the ability to do work makes perfect sense in terms of either form of mechanical energy. Discuss the law of conservation of energy and dispel any misconceptions related to this law, such is the idea that moving objects just slow down naturally. Identify heat generated by friction as the usual explanation for apparent violations of the law. 

[AL] Start a discussion about how other useful forms of energy also end up as wasted heat, such as light, sound, and electricity. Try to get students to understand heat and temperature at a molecular level. Explain that energy lost to friction is really transforming kinetic energy at the macroscopic level to kinetic energy at the atomic level. Mechanical Energy and Conservation of Energy 

We saw earlier that mechanical energy can be either potential or kinetic. In this section we will see how energy is transformed from one of these forms to the other. We will also see that, in a closed system, the sum of these forms of energy remains constant. 

Quite a bit of potential energy is gained by a roller coaster car and its passengers when they are raised to the top of the first hill. Remember that the potential part of the term means that energy has been stored and can be used at another time. You will see that this stored energy can either be used to do work or can be transformed into kinetic energy. For example, when an object that has gravitational potential energy falls, its energy is converted to kinetic energy. Remember that both work and energy are expressed in joules. 

Refer back to this figure . The amount of work required to raise the TV from point A to point B is equal to the amount of gravitational potential energy the TV gains from its height above the ground. This is generally true for any object raised above the ground. If all the work done on an object is used to raise the object above the ground, the amount work equals the object s gain in gravitational potential energy. However, note that because of the work done by friction, these energy work transformations are never perfect. Friction causes the loss of some useful energy. In the discussions to follow, we will use the approximation that transformations are frictionless. 

Now, let s look at the roller coaster in [link] . Work was done on the roller coaster to get it to the top of the first rise; at this point, the roller coaster has gravitational potential energy. It is moving slowly, so it also has a small amount of kinetic energy. As the car descends the first slope, its PE is converted to KE . At the low point much of the original PE has been transformed to KE , and speed is at a maximum. As the car moves up the next slope, some of the KE is transformed back into PE and the car slows down. During this roller coaster ride, there are conversions between potential and kinetic energy. 

[OL] [AL] Ask if definitions of energy make sense to the class, and try to bring out any expressions of confusions or misconceptions. Help them make the logical leap that, if energy is the ability to do work, it makes sense that it is expressed by the same unit of measurement. Ask students to name all the forms of energy they can. Ask if this helps them get a feel for the nature of energy. Ask if they have a problem seeing how some forms of energy, such as sunlight, can do work. 

[BL] [OL] You may want to introduce the concept of a reference point as the starting point of motion. Relate this to the origin of a coordinate grid. 

[BL] Make it clear that energy is a different property with different units than either force or power. 

[OL] Help students understand that the speed with which the TV is delivered is not part of the calculation of PE . It is assumed that the speed is constant. Any KE due to increases in delivery speed will be lost when motion stops. 

[BL] Be sure there is a clear understanding of the distinction between kinetic and potential energy and between velocity and acceleration. Explain that the word potential means that the energy is available but it does not mean that it has to be used or will be used. Energy Skate Park Basics 

This simulation shows how kinetic and potential energy are related, in a scenario similar to the roller coaster. Observe the changes in KE and PE by clicking on the bar graph boxes. Also try the three differently shaped skate parks. Drag the skater to the track to start the animation. Click here for the simulation 

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This animation shows the transformations between KE and PE and how speed varies in the process. Later we can refer back to the animation to see how friction converts some of the mechanical energy into heat and how total energy is conserved. 

On an actual roller coaster, there are many ups and downs, and each of these is accompanied by transitions between kinetic and potential energy. Assume that no energy is lost to friction. At any point in the ride, the total mechanical energy is the same, and it is equal to the energy the car had at the top of the first rise. This is a result of the law of conservation of energy , which says that, in a closed system, total energy is conserved (that is, it is constant). Using subscripts 1 and 2 to represent initial and final energy, this law is expressed as: K E 1 + P E 1 = K E 2 + P E 2 K E 1 + P E 1 = K E 2 + P E 2 

Either side equals the total mechanical energy. The phrase in a closed system means we are assuming no energy is lost to the surroundings due to friction and air resistance. If we are making calculations on dense falling objects, this is a good assumption. For the roller coaster, this assumption introduces some inaccuracy to the calculation. Calculations involving Mechanical Energy and Conservation of Energy 

When calculating work or energy, use units of meters for distance, newtons for force, kilograms for mass, and seconds for time. This will assure that the result is expressed in joules. 

[BL] [OL] Impress upon the students the significant amount of work required to get a roller coaster car to the top of the first, highest point. Compare it to the amount of work it would take to walk to the top of the roller coaster. Ask students why they may feel tired if they had to walk or climb to the top of the roller coaster (they have to use energy to exert the force required to move their bodies upwards against the force of gravity). Check if students can correctly predict that the ratio of the mass of the car to a person s mass would be the ratio of work done and energy gained (for example, if the car s mass was 10 times a person s mass, the amount of work needed to move the car to the top of the hill would be 10 times the work needed to walk up the hill). Conservation of Energy 

This video discusses conversion of PE to KE and conservation of energy. The scenario is very similar to the roller coaster and the skate park. It is also a good explanation of the energy changes studied in the snap lab. 

Before showing the video, review all the equations involving kinetic and potential energy and conservation of energy. Also be sure the students have a qualitative understanding of the energy transformation taking place. Refer back to the snap lab and the simulation lab. 

[link] Applying the Law of Conservation of Energy 

A 10 kg rock falls from a 20 m cliff. What are the kinetic and potential energy when the rock has fallen 10 m? Strategy 

Choose the equation: 

K E 1 + P E 1 = K E 2 + P E 2 K E 1 + P E 1 = K E 2 + P E 2 

K E = 1 2 m v 2 ; P E = m g h K E = 1 2 m v 2 ; P E = m g h 

1 2 m v 1 2 + m g h 1 = 1 2 m v 2 2 + m g h 2 1 2 m v 1 2 + m g h 1 = 1 2 m v 2 2 + m g h 2 

List the knowns: 

m = 10 kg, v 1 = 0, g = 9.80 m s 2 m s 2 , h 1 = 20 m, h 2 = 10 m 

Identify the unknowns 

KE 2 and PE 2 

Plug in the knowns. Solution 

P E 2 = m g h 2 = 10 ( 9.80 ) 10 = 980 J P E 2 = m g h 2 = 10 ( 9.80 ) 10 = 980 J 

K E 2 = P E 2 ( K E 1 + P E 1 ) = 980 { [ 0 [ 10 ( 9.80 ) 20 ] ] } = 980 J K E 2 = P E 2 ( K E 1 + P E 1 ) = 980 { [ 0 [ 10 ( 9.80 ) 20 ] ] } = 980 J Discussion 

Alternatively, conservation of energy equation could be solved for v 2 and KE 2 could be calculated. Note that m could also be eliminated. 

Note that we can solve many problems involving conversion between KE and PE without knowing the mass of the object in question. This is because kinetic and potential energy are both proportional to the mass of the object. In a situation where KE = PE , we know that m g h = (1/2) m v 2 . Dividing both sides by m and rearranging, we get the relationship: 

2 g h = v 2 . 

Kinetic and potential energy are both proportional to the mass of the object. In a situation where KE = PE , we know that m g h = (1/2) m v 2 . Dividing both sides by m and rearranging, we get the relationship: 2 g h = v 2 . Practice Problems 

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In this activity, you will calculate the potential energy of an object and predict the object s speed when all that potential energy has been converted to kinetic energy. You will then check your prediction. You will be dropping objects from a height. Be sure to stay a safe distance from the edge. Don t lean over the railing too far. Make sure that you do not drop objects into an area where people or vehicles pass by. Make sure that dropping objects will not cause damage. Four marbles (or similar small, dense objects) Stopwatch Metric measuring tape long enough to measure the chosen height A scale Work with a partner. Find and record the mass of four small, dense objects per group. Choose a location where the objects can be safely dropped from a height of at least 15 meters. A bridge over water with a safe pedestrian walkway will work well. Measure the distance the object will fall. Calculate the potential energy of the object before you drop it using PE = m g h = (9.80) mh. Predict the kinetic energy and velocity of the object when it lands using PE = KE and so, m g h = m v 2 2 ; v = 2 ( 9.80 ) h = 4.43 h m g h = m v 2 2 ; v = 2 ( 9.80 ) h = 4.43 h One partner drops the object while the other measures the time it takes to fall. Take turns being the dropper and the timer until you have made four measurements. Average your drop multiplied by and calculate the velocity of the object when it landed using v = a t = g t = (9.80) t . Compare your results to your prediction. 

Before students begin the lab, find the nearest location where objects can be dropped safely from a height of at least 15 m. 

As students work through the lab, encourage lab partners to discuss their observations. Encourage them to discuss differences in results between partners. Ask if there is any confusion about the equations they are using and whether they seem valid based on what they have already learned about mechanical energy. Ask them to discuss the effect of air resistance and how density is related to that effect. 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which one and direct students to the relevant content. Section Summary Mechanical energy may be either kinetic (energy of motion) or potential (stored energy). Doing work on an object or system changes its energy. Total energy in a closed, isolated system is constant. Key Equations conservation of energy K E 1 + P E 1 = K E 2 + P E 2 K E 1 + P E 1 = K E 2 + P E 2 Concept Items 

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[link] Glossary law of conservation of energy states that energy is neither created nor destroyedSimple Machines Simple Machines Section Learning Objectives 

By the end of this section, you will be able to: Describe simple and complex machines Calculate mechanical advantage and efficiency of simple and complex machines 

The learning objectives in this section will help your students master the following TEKS: (6C) : Describe simple and complex machines and solve problems involving simple machines. (6D) : Define input work, output work, mechanical advantage, and efficiency of machines. Section Key Terms complex machine efficiency output ideal mechanical advantage inclined plane input work lever mechanical advantage output work pulley screw simple machine wedge wheel and axle 

In this section you will apply what you have learned about work to find the mechanical advantage and efficiency of simple machines. 

[BL] [OL] Ask the students what they know about machines and work. Dispel any misconceptions that machines reduce the amount of work. Be sure students do not equate machines and motors by asking for (and, if necessary, providing) examples of machines that are not motorized. Explain that simple machines are often hand-held, and that they reduce force, not work. 

[AL] Ask for recall of the formula W = f d . Explain that the product of force and distance is critical to understanding simple machines. Because the amount of work is not changed, the term f d does not change, but force can decrease if distance increases. This is the underlying principle of all simple machines. Simple Machines 

Simple machines make work easier, but they do not decrease the amount of work you have to do. Why can t simple machines change the amount of work that you do? Recall that in closed systems the total amount of energy is conserved. A machine cannot increase the amount of energy you put into it. So, why is a simple machine useful? Although it cannot change the amount of work you do, a simple machine can change the amount of force you must apply to an object, and the distance over which you apply the force. In most cases, a simple machine is used to reduce the amount of force you must exert to do work. The down side is that you must exert the force over a greater distance, because the product of force and distance, f d , (which equals work) does not change. 

Let s examine how this works in practice. In Figure_09_03_lever(a) , the worker uses a type of lever to exert a small force over a large distance, while the pry bar pulls up on the nail with a large force over a small distance. Figure_09_03_lever(b) shows the how a lever works mathematically. The effort force, applied at F e , lifts the load (the resistance force) which is pushing down at F r . The triangular pivot is called the fulcrum ; the part of the lever between the fulcrum and F e is the effort arm, L e ; and the part to the left is the resistance arm, L r . The mechanical advantage is a number that tells us how many times a simple machine multiplies the effort force. The ideal mechanical advantage , IMA , is the mechanical advantage of a perfect machine with no loss of useful work caused by friction between moving parts. The equation for IMA is shown in Figure_09_03_lever(b) . (a) A pry bar is a type of lever. (b) The ideal mechanical advantage equals the length of the effort arm divided by the length of the resistance arm of a lever. 

In general, the IMA = the resistance force, F r , divided by the effort force, F e . IMA also equals the distance over which the effort is applied, d e , divided by the distance the load travels, d r . I M A = F r F e = d e d r I M A = F r F e = d e d r 

Getting back to conservation of energy, for any simple machine, the work put into the machine, W i , equals the work the machine puts out, W o . Combining this with the information in the paragraphs above, we can write: W i = W o F e d e = F r d r If F e F r , then d e d r W i = W o F e d e = F r d r If F e F r , then d e d r 

The equations show how a simple machine can output the same amount of work while reducing the amount of effort force by increasing the distance over which the effort force is applied. Introduction to Mechanical Advantage 

This video shows how to calculate the IMA of a lever by three different methods: (1) from effort force and resistance force; (2) from the lengths of the lever arms, and; (3) from the distance over which the force is applied and the distance the load moves. 

The beginning of this video may cause more confusion than illumination. It shows a derivation using trig functions that is beyond the scope of this chapter. Interested students may want to work their way through it. Most students should skip to the final two or three minutes which explain the basics of calculating IMA of a lever from different ratios. Review W = f d . 

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Some levers exert a large force to a short effort arm. This results in a smaller force acting over a greater distance at the end of the resistance arm. Examples of this type of lever are baseball bats, hammers, and golf clubs. In another type of lever, the fulcrum is at the end of the lever and the load is in the middle, as in the design of a wheelbarrow. 

[AL] Tell students there are two other classes of levers with different arrangements of load, fulcrum, and effort. Ask them first to try to sketch these. After they have discovered the three kinds, with or without your help, ask if they can think of examples of the types not shown in [link] . 

The simple machine shown in [link] is called a wheel and axle . It is actually a form of lever. The difference is that the effort arm can rotate in a complete circle around the fulcrum, which is the center of the axle. Force applied to the outside of the wheel causes a greater force to be applied to the rope that is wrapped around the axle. As shown in the figure, the ideal mechanical advantage is calculated by dividing the radius of the wheel by the radius of the axle. Any crank-operated device is an example of a wheel and axle Force applied to a wheel exerts a force on its axle. 

[BL] [OL] See if the students grasp the idea that a wheel and axle is really a type of lever. Show them that it looks more like a lever if the wheel is replaced by a crank. Give some examples: hand-powered windlass, steering wheel, door knob, and so on. Ask them why steering wheels had a greater diameter before power steering was invented. 

[AL] Explain that wheels on vehicles are not really simple machines in the same sense as the one in [link] . The axle on a vehicle does not do work on a load. Energy loss to friction is reduced, but nothing is lifted. 

An inclined plane and a wedge are two forms of the same simple machine. A wedge is simply two inclined planes back to back. [link] shows the simple formulas for calculating the IMA s of these machines. All sloping, paved surfaces for walking or driving are inclined planes. Knives and axe heads are examples of wedges. An inclined plane is shown on the left, and a wedge is shown on the right. 

[BL] [OL] Talk about how inclined planes and wedges are similar and different. Note that, when using an inclined plane the load moves, but when using a wedge the load is stationary and the machine moves. Explain why more energy is usually lost to friction with these machines than with other simple machines. 

The screw shown in [link] is actually a lever attached to a circular inclined plane. Wood screws (of course) are also examples of screws. The lever part of these screws is a screw driver. In the formula for IMA , the distance between screw threads is called pitch and has the symbol P . The screw shown here is used to lift very heavy objects, like the corner of a car or a house a short distance. 

[BL] [OL] Suggest that a screw is classified as a separate type of simple machine perhaps because it looks so different from what it really is: an inclined plane which sometimes is turned by a lever. Explain that the combined mechanical advantage can be very great. Devices like the one shown in [link] are used to lift cars and even houses. Have the students compare this screw to a wood screw and a circular stairway. 

[AL] Ask students how the forces exerted by a wood screw are different from those exerted by the screw in [link] . Ask for an explanation of the 2 in the equation for IMA . 

[link] shows three different pulley systems. Of all simple machines, mechanical advantage is easiest to calculate for pulleys. Simply count the number of ropes supporting the load. That is the IMA . Once again we have to exert force over a longer distance to multiply force. To raise a load 1 meter with a pulley system you have to pull N meters of rope. Pulley systems are often used to raise flags and window blinds and are part of the mechanism of construction cranes. Three pulley systems are shown here. 

[BL] [OL] The calculation for IMA of a pulley seems too easy to be true, but it is. Ask students to try to understand why IMA is simply N . Tell them that watching the video should make this point clear. Pulleys were once seen on sailing ships and farms, where they were used lift heavy loads. The overhang you may have seen on the end of old barn roofs is where a pulley was once attached. This way bales of hay could be lifted into the hay loft without getting wet. Pulleys can still be seen in use, most commonly on large building cranes. Mechanical Advantage of Inclined Planes and Pulleys 

The first part of this video shows how to calculate the IMA of pulley systems. The last part shows how to calculate the IMA of an inclined plane. 

Review what was learned about the IMA of inclined planes and pulley systems before watching the video. Remind the students that, for an ideal machine, work in = work out and that W = f d . The video shows how to find the f s and the d s. 

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A complex machine is a combination of two or more simple machines. The wire cutters in [link] combine two levers and two wedges. Bicycles include wheel and axles, levers, screws, and pulleys. Cars and other vehicles are combinations of many machines. Wire cutters are a common complex machine. 

[BL] [OL] Be sure students understand that a complex machine is just a combination of simple machines and is still fairly simple. Don t let them confuse the term with complicated machines such as computers. Note that the IMAs of the individual simple machines in a complex machine usually multiply because the output force of one machine becomes the input force of the other machine. For fun, you could ask the students to search Google images for Rube Goldberg machine. Calculating Mechanical Advantage and Efficiency of Simple Machines 

In general, the IMA = the resistance force, F r , divided by the effort force, F e . IMA also equals the distance over which the effort is applied, d e , divided by the distance the load travels, d r . I M A = F r F e = d e d r I M A = F r F e = d e d r 

Refer back to the discussions of each simple machine for the specific equations for the IMA for each type of machine. 

No simple or complex machines have the actual mechanical advantages calculated by the IMA equations. In real life, some of the applied work always ends up as wasted heat due to friction between moving parts. Both the input work ( W i ) and output work ( W o ) are the result of a force, F , acting over a distance, d . W i = F i d i and W o = F o d o W i = F i d i and W o = F o d o 

The efficiency output of a machine is simply the output work divided by the input work, and is usually multiplied by 100 so that it is expressed as a percent. % efficiency = W o W i 100 % efficiency = W o W i 100 

Look back at the pictures of the simple machines and think about which would have the highest efficiency. Efficiency is related to friction, and friction depends on the smoothness of surfaces and on the area of the surfaces in contact. How would lubrication affect the efficiency of a simple machine? 

[BL] [OL] Review the material on loss of mechanical energy to heat and the law of conservation of energy. Explain how heat lost because of friction assures that W o will always be less than W i preventing efficiency from ever reaching 100%. Efficiency of a Lever 

The input force of 11 N acting on the effort arm of a lever moves 0.4 m, which lifts a 40 N weight resting on the resistance arm a distance of 0.1 m. What is the efficiency of the machine? Strategy 

State the equation for efficiency of a simple machine: % efficiency = W o W i 100 % efficiency = W o W i 100 and calculate W o and W i . Both work values are the product Fd . Solution 

W i = F i d i W i = F i d i = (11)(0.4) = 4.4 J and W o = F o d o W o = F o d o = (40)(0.1) = 4.0 J, then % efficiency = W o W i 100 = 4.0 4.4 100 = 91 % % efficiency = W o W i 100 = 4.0 4.4 100 = 91 % Discussion 

Efficiency in real machines will always be less than 100% because of work that is converted to unavailable heat by friction and air resistance. W o and W i can always be calculated as a force multiplied by a distance, although these quantities are not always as obvious as they are in the case of a lever. 

Teaching tip: When calculating efficiency, it is easy enough to understand what force in and force out are: the force you apply is force in and the weight of the object that is being lifted is force out. The input and output distances are easy to see for the lever, inclined plane and wedge. The other three are not as obvious. For a pulley system, the input distance is how far you pull the rope, and the output distance is the distance the load rises. For a wheel and axle, the input distance is the circumference of the wheel, and the output distance is the circumference of the axle. For a screw, the input distance is the circumference of the circle over which the force is applied, and the output distance is the distance between the screw threads. Practice Problems 

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[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which one and direct students to the relevant content. Section Summary The six types of simple machines make work easier by changing the f d term so that force is reduced at the expense of increased distance. The ratio of output force to input force is a machine s mechanical advantage. Combinations of two or more simple machines are called complex machines. The ratio of output work to input work is a machine s efficiency. Key Equations ideal mechanical advantage (general) I M A = F r F e = d e d r I M A = F r F e = d e d r (lever) I M A = L e L r (wheel and axle) I M A = R r (inclined plane) I M A = L h (wedge) I M A = L t (pulley) I M A = N (screw) I M A = 2 L P (lever) I M A = L e L r (wheel and axle) I M A = R r (inclined plane) I M A = L h (wedge) I M A = L t (pulley) I M A = N (screw) I M A = 2 L P input work W i = F i d i W i = F i d i output work W o = F o d o W o = F o d o efficiency output % efficiency = W o W i 100 % efficiency = W o W i 100 Concept Items 

[link] Critical Thinking 

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Conservation of Energy and Energy Transfer; Cause and Effect; and S EP, Planning and Carrying Out Investigations 

Plan an investigation to measure the mechanical advantage of simple machines and compare to the IMA of the machine. Also measure the efficiency of each machine studied. Design an investigation to make these measurements for these simple machines: lever, inclined plane, wheel and axle and a pulley system. In addition to these machines, include a spring scale, a tape measure, and a weight with a loop on top that can be attached to the hook on the spring scale. A spring scale is shown in [link] . A spring scale measures weight, not mass. 

LEVER: Beginning with the lever, explain how you would measure input force, output force, effort arm, and resistance arm. Also explain how you would find the distance the load travels and the distance over which the effort force is applied. Explain how you would use this data to determine IMA and efficiency. 

INCLINED PLANE: Make measurements to determine IMA and efficiency of an inclined plane. Explain how you would use the data to calculate these values. Which property do you already know? Note that there are no effort and resistance arm measurements, but there are height and length measurements. 

WHEEL AND AXLE: Again, you will need two force measurements and four distance measurements. Explain how you would use these to calculate IMA and efficiency. 

SCREW: You will need two force measurements, two distance traveled measurements, and two length measurements. You may describe a screw like the one shown in [link] or you could use a screw and screw driver. (Measurements would be easier for the former). Explain how you would use these to calculate IMA and efficiency. 

PULLEY SYSTEM: Explain how you would determine the IMA and efficiency of the four-pulley system shown in [link] . Why do you only need two distance measurements for this machine? 

Design a table that compares the efficiency of the five simple machines. Make predictions as to the most and least efficient machines. Test Prep Multiple Choice 

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[link] Test Prep Short Answer 

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[link] Glossary complex machine a machine that combines two or more simple machines efficiency output work divided by input work ideal mechanical advantage the mechanical advantage of an idealized machine that loses no energy to friction inclined plane a simple machine consisting of a slope input work effort force multiplied by the distance over which it is applied lever a simple machine consisting of a rigid arm that pivots on a fulcrum mechanical advantage the number of times the input force is multiplied output work output force multiplied by the distance over which it acts pulley a simple machine consisting of a rope that passes over one or more grooved wheels screw a simple machine consisting of a spiral inclined plane simple machine a machine that makes work easier by changing the amount or direction of force required to move an object wedge a simple machine consisting of two back-to-back inclined planes wheel and axle a simple machine consisting of a rod fixed to the center of a wheelIntroduction Introduction In this chapter you will learn about: Relative Motion, Distance, and Displacementm Speed and Velocity Position vs. Time Graphs Velocity vs. Time Graphs The world s fastest train reached a speed of over 350 miles per hour. At this rate, a train traveling from Boston to Washington, DC, a distance of 439 miles, could make the trip in under an hour and a half. Presently, the fastest train on this route takes over six hours to cover this distance. (credit: Alex Needham, Public Domain) 

Have the students describe the photo of the train and discuss its motion. Tell them they will learn about motion. Start the discussion with how a train moves, and guide them toward discussing concepts of displacement, velocity, and acceleration. Ask questions: How do we know something is moving? What defines motion? What direction does the train move? What adjectives describe its motion? If it was a moving ball instead of a train, how would its motion be different? How would the train s motion change if its wheels were square instead of round or if it had studded tires? Try to uncover what ideas they already have about motion. 

Unless you have flown in an airplane, you have probably never traveled faster than 150 mph. Can you imagine traveling in a train like the one shown in [link] that goes over 300 mph? Despite the high speed, the people riding in this train may not notice that they are moving at all unless they look out the window! This is because motion, even motion at 300 mph, is relative to the observer. 

In this chapter, you will learn why it is important to identify a reference frame in order to clearly describe motion. For now, the motion you describe will be one-dimensional. Within this context, you will learn the difference between distance and displacement as well as the difference between speed and velocity. Then you will look at some graphing and problem-solving techniques. 

Before students begin this chapter, it would be useful to review these concepts: Using significant figures in calculations Demonstrate how to use the proper number of significant figures when adding, subtracting, multiplying, and dividing. Converting units Demonstrate how to convert from km/h to m/s. Calculating average Demonstrate how to average two numbers by dividing their sum by 2. Commonly used terms Explain that "constant" means "unchanging," so "constant speed" refers to speed that is not changing. Explain that "initial" means "starting," so "initial time" is the time at which the action mentioned in a problem begins. Explain that an object that is not moving is often described in physics as being "at rest."Relative Motion, Distance and Displacement Relative Motion, Distance and Displacement Section Learning Objectives 

By the end of this section, you will be able to: Describe motion in different reference frames Define distance and displacement, and distinguish between the two Solve problems involving distance and displacement 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4B) : describe and analyze motion in one dimension using equations with the concepts of distance, displacement, speed, average velocity, instantaneous velocity, and acceleration; (4F) : identify and describe motion relative to different frames of reference. Section Key Terms displacement distance kinematics magnitude position reference frame scalar vector 

[BL] [OL] Start by asking what "position" is and how it is defined. You can use a toy car or other object. Then ask how they know the object has moved. Lead them to the idea of a defined starting point. Then bring in the concept of a numbered line as a way of quantifying motion. 

[AL] Ask students to describe the path of movement and emphasize that direction is a necessary component of a definition of motion. Ask the students to form pairs, and ask each pair to come up with their own definition of motion. Then compare and discuss definitions as a class. What components are necessary for a definition of motion? Defining Motion 

Our study of physics opens with kinematics the study of motion without considering its causes. Objects are in motion everywhere you look. Everything from a tennis game to a space-probe flyby of the planet Neptune involves motion. When you are resting, your heart moves blood through your veins. Even in inanimate objects, atoms are always moving. 

How do you know something is moving? The location of an object at any particular time is its position . More precisely, you need to specify its position relative to a convenient reference frame . Earth is often used as a reference frame, and we often describe the position of an object as it relates to stationary objects in that reference frame. For example, a rocket launch would be described in terms of the position of the rocket with respect to the Earth as a whole, while a professor s position could be described in terms of where she is in relation to the nearby white board. In other cases, we use reference frames that are not stationary but are in motion relative to the Earth. To describe the position of a person in an airplane, for example, we use the airplane, not the Earth, as the reference frame. (See [link] .) Thus, you can only know how fast and in what direction an object's position is changing against a background of something else that is either not moving or moving with a known speed and direction. The reference frame is the coordinate system from which the positions of objects are described. Are clouds a useful reference frame for airplane passengers? Why or why not? (credit: Paul Brennan, Public Domain) 

[OL] [AL] Explain that the word "kinematics" comes from a Greek term meaning motion. It is related to other English words, such as "cinema" (movies, or moving pictures) and "kinesiology" (the study of human motion). 

Your classroom can be used as a reference frame. In the classroom, the walls are not moving. Your motion as you walk to the door, can be measured against the stationary background of the classroom walls. You can also tell if other things in the classroom are moving, such as your classmates entering the classroom or a book falling off a desk. You can also tell in what direction something is moving in the classroom. You might say, The teacher is moving toward the door. Your reference frame allows you to determine not only that something is moving but also the direction of motion. 

You could also serve as a reference frame for others movement. If you remained seated as your classmates left the room, you would measure their movement away from your stationary location. If you and your classmates left the room together, then your perspective of their motion would be change. You, as the reference frame, would be moving in the same direction as your other moving classmates. As you will learn in the Snap Lab, your description of motion can be quite different when viewed from difference reference frames. 

[BL] [OL] You may want to introduce the concept of a reference point as the starting point of motion. Relate this to the origin of a coordinate grid. 

[AL] Explain that the reference frames considered in this chapter are inertial reference frames, which means they are not accelerating. Engage students in a discussion of how it is the difference in motion between the reference frame of the observer and the reference frame of the object that is important in describing motion. The reference frames used in this chapter might be moving at a constant speed relative to each other, but they are not accelerating relative to each other. 

[BL] [OL] [Visual]Misconception: Students may assume that a reference frame is a background of motion instead of the frame from which motion is viewed. Demonstrate the difference by having one student stand at the front of the class. Explain that this student represents the background. Walk once across the room between the student and the rest of the class. Ask the student and others in the class to describe the direction of your motion. The class might describe your motion as "to the right," but the student who is standing as a background to your motion would describe the motion as "to the left." Conclude by reminding students that the reference frame is the viewpoint of the observer, not the background. 

[BL] Have students practice describing simple examples of motion in the class from different reference frames. For example, slide a book across a desk. Ask students to describe its motion from their reference point, from the book's reference point, and from another student's reference point. Looking at Motion from Two Reference Frames 

In this activity you will look at motion from two reference frames. Which reference frame is correct? Choose an open location with lots of space to spread out so there is less chance of tripping or falling due to collision and/or loose basketballs. 1 basketball Work with a partner. Stand about a couple of meters away from your partner. Have your partner turn to the side so that you are looking at your partner s profile. Have your partner begin bouncing the basketball while standing in place. Describe the motion of the ball. Next, have your partner again bounce the ball, but this time your partner should walk forward with the bouncing ball. You will remain stationary. Describe the ball's motion. Again have your partner walk forward with the bouncing ball. This time, you should move alongside your partner while continuing to view your partner s profile. Describe the ball's motion. Switch places with your partner, and repeat Steps 1 3. 

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Before students begin the lab, arrange a location where pairs of students can have ample room to walk forward at least several meters. 

As students work through the lab, encourage lab partners to discuss their observations. In Steps 1 and 3, students should observe the ball move straight up and straight down. In Step 2, students should observe the ball in a zigzag path away from the stationary observer. 

After the lab, lead students in discussing their observations. Ask them which reference frame is the correct one. Then emphasize that there is not a single correct reference frame. All reference frames are equally valid. History: Galileo's Ship Galileo Galilei (1564 1642) studied motion and developed the concept of a reference frame. (credit: Domenico Tintoretto) 

The idea that a description of motion depends on the reference frame of the observer has been known for hundreds of years. The 17th-century astronomer Galileo Galilei ( [link] ) was one of the first scientists to explore this idea. Galileo suggested the following thought experiment. Imagine a windowless ship moving at a constant speed and direction along a perfectly calm sea. Is there a way that a person inside the ship can determine whether the ship is moving? You can extend this thought experiment by also imagining a person standing on the shore. How can a person on the shore determine whether the ship is moving? 

Galileo came to an amazing conclusion. Only by looking at each other can a person in the ship or a person on shore describe the motion of one relative to the other. In addition, their descriptions of motion would be identical. A person inside the ship would describe the person on the land as moving past the ship. The person on shore would describe the ship and the person inside it as moving past. Galileo realized that observers moving at a constant speed and direction relative to each other describe motion in the same way. Galileo had discovered that a description of motion is only meaningful if you specify a reference frame. 

[link] Distance vs. Displacement 

As we study the motion of objects, we must first be able to describe the object s position. Before your parent drives you to school, the car is sitting in your driveway. Your driveway is the starting position for the car. When you reach your high school, the car has changed position. Its new position is your school. Your total change in position is measured from your house to your school. 

Physicists use variables to represent terms. We will use d to represent car s position. We will use a subscript to differentiate between the initial position, d 0 , and the final position, d f . In addition, vectors, which we will discuss later, will be in bold or will have an arrow above the variable. Scalars will be italicized. 

In some books, x or s is used instead of d to describe position. In d 0 , said d naught , the subscript 0 stands for initial . When we begin to talk about two-dimensional motion, sometimes other subscripts will be used to describe horizontal position, d x , or vertical position, d y . So, you might see references to d 0x and d fy . 

Now imagine driving from your house to a friend's house located several kilometers away. How far would you drive? The distance an object moves is the length of the path between its initial position and its final position. The distance you drive to your friend's house depends on your path. As shown in [link] , distance is different from the length of a straight line between two points. The distance you drive to your friend's house is probably longer than the straight line between the two houses. A short line separates the starting and ending points of this motion, but the distance along the path of motion is considerably longer. 

We often want to be more precise when we talk about position. The description of an object s motion often includes more than just the distance it moves. For instance, if it is a five kilometer drive to school, the distance traveled is 5 kilometers. After dropping you off at school and driving back home, your parent will have traveled a total distance of 10 kilometers. The car and your parent will end up in the same starting position in space. The net change in position of an object is its displacement , or d d . The Greek letter delta, , means change in . The total distance that your car travels is 10 miles, but the total displacement is 0. 

Help students learn the difference between distance and displacement by showing examples of motion. As students watch, walk straight across the room and have students estimate the length of your path. Then, at same starting point, walk along a winding path to the same ending point. Again, have students estimate the length of your path. 

Ask: Which motion showed displacement? Which showed distance? Point out that the first motion shows displacement, and the second shows distance along a path. In both cases, the starting and ending points were the same. 

[OL] Be careful that students do not assume that initial position is always zero. Emphasize that although initial position is often zero, motion can start from any position relative to a starting point. 

[Visual]Demonstrate positive and negative displacement by placing two meter sticks on the ground with their zero marks end-to-end. As students watch, place a small car at the zero mark. Slowly move the car to students' right a short distance and ask students what its displacement is. Then move the car to the left of the zero mark. Point out that the car now has a negative displacement. 

Students will learn more about vectors and scalars later when they study two-dimensional motion. For now, it is sufficient to introduce the terms and let students know that a vector includes information about direction. 

[BL] Ask students whether each of the following is a vector quantity or a scalar quantity: temperature (scalar), force (vector), mass (scalar). 

[OL] Ask students to provide examples of vector quantities and scalar quantities. 

[Kinesthetic] Provide students with large arrows cut from construction paper. Have them use the arrows to identify the magnitude (number or length of arrows) and direction of displacement. Emphasize that distance cannot be represented by arrows because distance does not include direction. Distance vs. Displacement 

In this activity you will compare distance and displacement. Which term is more useful when making measurements? 1 recorded song available on a portable device 1 tape measure 3 pieces of masking tape A room (like a gym) with a clear wall that is large and clear enough for all pairs of students to walk back and forth without running into each other. One student from each pair should stand with their back to the longest wall in the classroom. Students should stand at least 0.5 meters away from each other. Mark this starting point with a piece of masking tape. The second student from each pair should stand facing their partner, about two to three meters away. Mark this point with a second piece of masking tape. Student pairs line up at the starting point along the wall. The teacher turns on the music. Each pair walks back and forth from the wall to the second marked point until the music stops playing. Keep count of the number of times you walk across the floor. When the music stops, mark your ending position with the third piece of masking tape. Measure from your starting, initial position to your ending, final position. Measure the length of your path from the starting position to the second marked position. Multiply this measurement by the total number of times you walked across the floor. Then add this number to your measurement from step 6. Compare the two measurements from steps 6 and 7. 

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Choose a room that is large enough for all students to walk unobstructed. Make sure the total path traveled is short enough that students can walk back and forth across it multiple times during the course of a song. Have them measure the distance between the two points and come to a consensus. When students measure their displacement, make sure that they measure forward from the direction they marked as the starting position. After they have completed the lab, have them discuss their results. 

If you are describing only your drive to school, then the distance traveled and the displacement are the same 5 km. When you are describing the entire round trip, distance and displacement are different. When you describe distance, you only include the magnitude , the size or amount, of the distance traveled. However, when you describe the displacement, you take into account both the magnitude of the change in position and the direction of movement. 

In our previous example, the car travels a total of 10 km, but it drives 5 of those kilometers forward towards school and 5 of those kilometers back in the opposite direction. If we ascribe the forward direction a positive (+) and the opposite direction a negative ( ), then the two quantities will cancel each other out when added together. 

A quantity, such as distance, that has magnitude (i.e. how big or how much) but does not take into account direction is called a scalar . A quantity, such as displacement, that has both magnitude and direction is called a vector . Vectors Scalars 

This video introduces and differentiates between vectors and scalars. It also introduces quantities that we will be working with during the study of kinematics. 

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Define the concepts of vectors and scalars before watching the video. 

[OL] [BL] Come up with some examples of vectors and scalars and have the students classify each. 

[AL] Discuss how the concept of direction might be important for the study of motion. Displacement Problems 

Hopefully you now understand the conceptual difference between distance and displacement. Understanding concepts is half the battle in physics. The other half is math. A stumbling block to new physics students is trying to wade through the math of physics while also trying to understand the associated concepts. This struggle may lead to misconceptions and answers that make no sense. Once the concept is mastered, the math is far less confusing. 

So let s review and see if we can make sense of displacement in terms of numbers and equations. You can calculate an object's displacement by subtracting its original position, d 0 , from its final position d f . In math terms that means: d = d f d 0 d = d f d 0 

If the final position is the same as the initial position, then d = 0 d = 0 . 

To assign numbers and/or direction to these quantities, we need to define an axis with a positive and a negative direction. We also need to define an origin, or 0 . In this figure , the axis is in a straight line with home at zero and school in the positive direction. If we left home and drove the opposite way from school, motion would have been in the negative direction. We would have assigned it a negative value. In the round-trip drive, d f and d 0 were both at 0 km. In the one way trip to school, d f was at 5 km and d 0 was at 0 km. So, d d was 5 km. 

You may place your origin wherever you would like. You have to make sure that you calculate all distances consistently from your zero and you define one direction as positive and the other as negative. Therefore, it makes sense to choose the easiest axis, direction, and zero. In the example above, we took home to be zero because it allowed us to avoid having to interpret a solution with a negative sign. Calculating Distance and Displacement 

A cyclist rides 3 km west and then turns around and rides 2 km east. (a) What is her displacement? (b) What distance does she ride? (c) What is the magnitude of her displacement? Strategy 

To solve this problem, we need to find the difference between the final position and the initial position while taking care to note the direction on the axis. The final position is the sum of the two displacements, d 1 d 1 and d 2 d 2 . Solution Displacement: The rider s displacement is d = d f d 0 = 1 km d = d f d 0 = 1 km . Distance: The distance traveled is 3 km + 2 km = 5 km. The magnitude of the displacement is 1 km. Discussion 

The displacement is negative because we chose east to be positive and west to be negative. We could also have described the displacement as 1 km west. When calculating displacement, the direction mattered, but when calculating distance, the direction did not matter. The problem would work the same way if the problem were in the North South or y -direction. 

Physicists like to use standard units so it is easier to compare notes. The standard units for calculations are called SI units (System International). SI units are based on the metric system. The SI unit for displacement is the meter (m), but sometimes you will see a problem with kilometers, miles, feet, or other units of length. If one unit in a problem is an SI unit and another is not, you will need to convert all of your quantities to the same system before you can carry out the calculation. 

Point out to students that the distance for each segment is the absolute value of the displacement along a straight path. Practice Problems 

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[link] Mars Probe Explosion The Mars Climate Orbiter disaster illustrates the importance of using the correct calculations in physics. (credit: NASA) 

Physicists make calculations all the time, but they do not always get the right answers. In 1998, NASA, the National Aeronautics and Space Administration, launched the Mars Climate Orbiter, shown in [link] , a $125-million-dollar satellite designed to monitor the Martian atmosphere. It was supposed to orbit the planet and take readings from a safe distance. The American scientists made calculations in English units (feet, inches, pounds . . .) and forgot to convert their answers to the standard metric SI units. This was a very costly mistake. Instead of orbiting the planet as planned, the Mars Climate Orbiter ended up flying into the Martian atmosphere. The probe disintegrated. It was one of the biggest embarrassments in NASA s history. 

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The text feature describes a real-life miscalculation made by astronomers at NASA. In this case, the Mars Climate Orbiter s orbit needed to be calculated precisely because its machinery was designed to withstand only a certain amount of atmospheric pressure. The orbiter had to be close enough to the planet to take measurements and far enough away that it could remain structurally sound. One way to teach this concept would be to pick an orbital distance from Mars and have the students calculate the distance of the path and the height from the surface both in SI units and in English units. Ask why failure to convert might be a problem. Check Your Understanding 

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Use the questions under Check Your Understanding to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the formative assessment will help direct students to the relevant content. Section Summary A description of motion depends on the reference frame from which it is described. The distance an object moves is the length of the path along which it moves. Displacement is the difference in the initial and final positions of an object. Key Equations Displacement d = d f d 0 d = d f d 0 Concept Items 

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[link] Glossary displacement the change in position of an object against a fixed axis distance the length of the path actually traveled between an initial and a final position kinematics the study of motion without considering its causes magnitude size or amount position the location of an object at any particular time reference frame a coordinate system from which the positions of objects are described scalar a quantity that has magnitude but no direction vector a quantity that has both magnitude and directionSpeed and Velocity Speed and Velocity Section Learning Objectives 

By the end of this section, you will be able to: Calculate the average speed of an object. Relate displacement and average velocity. 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4B) : describe and analyze motion in one dimension using equations with the concepts of distance, displacement, speed, average velocity, instantaneous velocity, and acceleration; Section Key Terms average speed average velocity instantaneous speed instantaneous velocity speed velocity 

In this section, students will apply what they have learned about distance and displacement to the concepts of speed and velocity. 

[BL] [OL] Before students read the section, ask them to give examples of ways they have heard the word speed used. Then ask them if they have heard the word velocity used. Explain that these words are often used interchangeably in everyday life, but their scientific definitions are different. Tell students that they will learn about these differences as they read the section. 

[AL] Explain to students that velocity, like displacement, is a vector quantity. Ask them to speculate about ways that speed is different from velocity. After they share their ideas, follow up with questions that deepen their thought process, such as: Why do you think that? What is an example? How might apply these terms to motion that you see every day? Speed 

There is more to motion than distance and displacement. Questions such as, How long does a foot race take? and What was the runner s speed? cannot be answered without an understanding of other concepts. In this section we will look at time , speed, and velocity to expand our understanding of motion. 

A description of how fast or slow an object moves is its speed. Speed is the rate at which an object changes its location. Like distance, speed is a scalar because it has a magnitude but not a direction. Since speed is a rate, it depends on the time interval of motion. You can calculate the elapsed time or the change in time, t t , of motion as the difference between the ending time and the beginning time: t = t f t 0 t = t f t 0 

The SI unit of time is the second (s), and the SI unit of speed is meters per second (m/s), but sometimes kilometers per hour (km/h), miles per hour (mph) or other units of speed are used. 

When you describe an object's speed, you often describe the average over a time period. Average speed , v avg , is the distance traveled divided by the time during which the motion occurs: v avg = distance time v avg = distance time 

You can, of course, rearrange the equation to solve for either distance or time: time = distance v avg time = distance v avg distance = v avg time distance = v avg time 

Suppose, for example, a car travels 150 kilometers in 3.2 hours. Its average speed for the trip is: v avg = distance time = 150 km 3.2 h = 47 km/h v avg = distance time = 150 km 3.2 h = 47 km/h 

A car's speed would likely increase and decrease many times over a 3.2 hour trip. Its speed at a specific instant in time, however, is its instantaneous speed . A car's speedometer describes its instantaneous speed. 

[OL] [AL] Caution students that average speed is not always the average of an object's initial and final speeds. For example, suppose a car travels a distance of 100 km. The first 50 km it travels 30 km/h and the second 50 km it travels at 60 km/h. Its average speed would be distance /(time interval) = (100 km)/[(50 km)/(30 km/h) + (50 km)/(60 km/h)] = 40 km/h. If the car had spent equal times at 30 km and 60 km rather than equal distances at these speeds, its average speed would have been 45 km/h. 

[BL] [OL] Caution students that the terms speed, average speed, and instantaneous speed are all often referred to simply as speed in everyday language. Emphasize the importance in science to use correct terminology to avoid confusion and to properly communicate ideas. During a 30-minute round trip to the store, the total distance traveled is 6 km. The average speed is 12 km/h. The displacement for the round trip is zero, since there was no net change in position. Calculating Average Speed 

A marble rolls 5.2 m in 1.8 s. What was the marble's average speed? Strategy 

We know the distance the marble travels, 5.2 m, and the time interval, 1.8 s. We can use these values in the average speed equation. Solution v avg = distance time = 5.2 m 1.8 s = 2.9 m/s v avg = distance time = 5.2 m 1.8 s = 2.9 m/s Discussion 

Average speed is a scalar, so we do not include direction in the answer. We can check the reasonableness of the answer by estimating: 5 meters divided by 2 seconds is 2.5 m/s. Since 2.5 m/s is close to 2.9 m/s, the answer is reasonable. This is about the speed of a brisk walk, so it also makes sense. Practice Problems 

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[link] Velocity 

The vector version of speed is velocity. Velocity describes the speed and direction of an object. As with speed, it is useful to describe either the average velocity over a time period or the velocity at a specific moment. Average velocity is displacement divided by the time over which the displacement occurs: v avg = distance time = d t = d f d 0 t f t 0 v avg = distance time = d t = d f d 0 t f t 0 

Velocity, like speed, has SI units of meters per second (m/s), but since it is a vector, you must also include a direction. Furthermore, the variable v for velocity is bold because it is a vector, which is in contrast to the variable v for speed which is italicized because it is a scalar quantity. 

It is important to keep in mind that the average speed is not the same thing as the average velocity without its direction. Like we saw with displacement and distance in the last section, changes in direction over a time interval have a bigger effect on speed and velocity. 

Suppose a passenger moved toward the back of a plane with an average velocity of 4 m/s. We cannot tell from the average velocity whether the passenger stopped momentarily or backed up before he got to the back of the plane. To get more details, we must consider smaller segments of the trip over smaller time intervals such as those shown in [link] . If you consider infinitesimally small intervals, you can define instantaneous velocity , which is the velocity at a specific instant in time. Instantaneous velocity and average velocity are the same if the velocity is constant. The diagram shows a more detailed record of an airplane passenger heading toward the back of the plane, showing smaller segments of his trip. 

Earlier, you have read that distance traveled can be different than the magnitude of displacement. In the same way, speed can be different than the magnitude of velocity. For example, you drive to a store and return home in half an hour. If your car s odometer shows the total distance traveled was 6 km, then your average speed was 12 km/h. Your average velocity, however, was zero, because your displacement for the round trip is zero. Calculating Average Velocity or Speed 

This video reviews vectors and scalars and describes how to calculate average velocity and average speed when you know displacement and change in time. The video also reviews how to convert km/h to m/s. 

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This video does a good job of reinforcing the difference between vectors and scalars. The student is introduced to the idea of using s to denote displacement, which you may or may not wish to encourage. Before students watch the video, point out that the instructor uses s s for displacement instead of d, as used in this text. Explain the use of small arrows over variables is a common way to denote vectors in higher-level physics courses. Caution students that the customary abbreviations for hour and seconds are not used in this video. Remind students that in their own work they should use the abbreviations h for hour and s for seconds. Calculating Average Velocity 

A student has a displacement of 304 m north in 180 s. What was the student's average velocity? Strategy 

We know that the displacement is 304 m north and the time is 180 s. We can use the formula for average velocity to solve the problem. Solution 

v avg = d t = 304 m 180 s = 1.7 m/s north v avg = d t = 304 m 180 s = 1.7 m/s north Discussion 

Since average velocity is a vector quantity, you must include direction as well as magnitude in the answer. Notice, however, that the direction can be omitted until the end to avoid cluttering the problem. Pay attention to the significant figures in the problem. The distance 304 m has three significant figures, but the time interval 180 s has only two, so the quotient should have only two significant figures. 

Note the way scalars and vectors are represented. In this book, d represents distance, and d represents displacement. Similarly, v represents speed, and v represents velocity. A variable that is not bold indicates a scalar quantity, and a bold variable indicates a vector quantity. Vectors are sometimes represented by small arrows above the variable. 

Use this problem to emphasize the importance of using the correct number of significant figures in calculations. Some students have a tendency to include many digits in their final calculations. They incorrectly believe they are improving the accuracy of their answer by writing many of the digits shown on the calculator. Point out that doing this introduces errors into the calculations. In more complicated calculations, these errors can propagate and cause the final answer to be wrong. Instead, remind students to always carry one or two extra digits in intermediate calculations and to round the final answer to the correct number of significant figures. Solving for Displacement when Average Velocity and Time are Known 

Layla jogs with an average velocity of 2.4 m/s east. What is her displacement after 46 seconds? Strategy 

We know that Layla's average velocity is 2.4 m/s east, and the time interval is 46 seconds. We can rearrange the average velocity formula to solve for the displacement. Solution 

v avg = d t d = v a v g t = ( 2.4 m/s)(46 s) = 1.1 10 2 m east v avg = d t d = v a v g t = ( 2.4 m/s)(46 s) = 1.1 10 2 m east Discussion 

The answer is about 110 m east, which is a reasonable displacement for slightly less than a minute of jogging. A calculator shows the answer as 110.4 m. We chose to write the answer using scientific notation because we wanted to make it clear that we only used two significant figures. 

Dimensional analysis is a good way to determine whether you solved a problem correctly. Write the calculation using only units to be sure they match on opposite sides of the equal mark. In the worked example, you have: m = (m/s)(s). Since seconds is in the denominator for the average velocity and in the numerator for the time, the unit cancels out leaving only m and, of course, m = m. Solving for Time when Displacement and Average Velocity are Known 

Phillip walks along a straight path from his house to his school. How long will it take him to get to school if he walks 428 m west with an average velocity of 1.7 m/s west? Strategy 

We know that Phillip's displacement is 428 m west, and his average velocity is 1.7 m/s west. We can calculate the time required for the trip by rearranging the average velocity equation. Solution 

v avg = d t t = d v avg = 428 m 1.7 m/s = 2.5 10 2 s v avg = d t t = d v avg = 428 m 1.7 m/s = 2.5 10 2 s Discussion 

Here again we had to use scientific notation because the answer could only have two significant figures. Since time is a scalar, the answer includes only a magnitude and not a direction. Practice Problems 

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[link] The Walking Man 

In this simulation you will put your cursor on the man and move him first in one direction and then in the opposite direction. Keep the Introduction tab active. You can use the Charts tab after you learn about graphing motion later in this chapter. Carefully watch the sign of the numbers in the position and velocity boxes. Ignore the acceleration box for now. See if you can make the man s position positive while the velocity is negative. Then see if you can do the opposite. Click here for the simulation 

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This is a powerful interactive animation, and it can be used for many lessons. At this point it can be used to show that displacement can be either positive or negative. It can also show that when displacement is negative, velocity can be either positive or negative. Later it can be used to show that velocity and acceleration can have different signs. It is strongly suggested that you keep students on the Introduction tab. The Charts tab can be used after students learn about graphing motion later in this chapter. Check Your Understanding 

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Use the Check Your Understanding questions to assess students achievement of the sections learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which and direct students to the relevant content. Assessment items in TUTOR will allow you to reassess. Section Summary Average speed is a scalar quantity that describes distance traveled divided by the time during which the motion occurs. Velocity is a vector quantity that describes the speed and direction of an object. Average velocity is displacement over the time period during which the displacement occurs. If the velocity is constant, then average velocity and instantaneous velocity are the same. Key Equations Average speed v avg = distance time v avg = distance time Average velocity v avg = d t = d f d 0 t f t 0 v avg = d t = d f d 0 t f t 0 Concept Items 

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[link] Glossary average speed distance traveled divided by time during which motion occurs average velocity displacement divided by time over which displacement occurs instantaneous speed speed at a specific instant in time instantaneous velocity velocity at a specific instant in time speed rate at which an object changes its location velocity the speed and direction of an objectPosition vs. Time Graphs Position vs. Time Graphs Section Learning Objectives 

By the end of this section, you will be able to: Explain the meaning of slope in position vs. time graphs Solve problems using position vs. time graphs 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4A) : generate and interpret graphs and charts describing different types of motion, including the use of real-time technology such as motion detectors or photogates. Section Key Terms dependent variable independent variable tangent 

[BL] [OL] Describe a scenario, for example, in which you launch a water rocket into the air. It goes up 150 ft, stops, and then falls back to the earth. Have the students assess the situation. Where would they put their zero? What is the positive direction, and what is the negative direction? Have a student draw a picture of the scenario on the board. Then draw a position vs. time graph describing the motion. Have students help you complete the graph. Is the line straight? Is it curved? Does it change direction? What can they tell by looking at the graph? 

[AL] Once the students have looked at and analyzed the graph, see if they can describe different scenarios in which the lines would be straight instead of curved? Where the lines would be discontinuous? Graphing Position as a Function of Time 

A graph , like a picture, is worth a thousand words. Graphs not only contain numerical information, they also reveal relationships between physical quantities. In this section, we will investigate kinematics by analyzing graphs of position over time . 

Graphs in this text have perpendicular axes, one horizontal and the other vertical. When two physical quantities are plotted against each other, the horizontal axis is usually considered the independent variable , and the vertical axis is the dependent variable . In algebra, you would have referred to the horizontal axis as the x -axis and the vertical axis as the y -axis. As in [link] , a straight-line graph has the general form y = m x + b y = m x + b . 

Here m is the slope, defined as the rise divided by the run (as seen in the figure) of the straight line. The letter b is the y -intercept which is the point at which the line crosses the vertical, y -axis. In terms of a physical situation in the real world, these quantities will take on a specific significance, as we will see below. The diagram shows a straight-line graph. The equation for the straight line is y equals mx + b . 

In physics, time is usually the independent variable. Other quantities, such as displacement, are said to depend upon it. A graph of position versus time, therefore, would have position on the vertical axis (dependent variable) and time on the horizontal axis (independent variable). In this case, to what would the slope and y -intercept refer? Let s look back at our original example when studying distance and displacement. 

The drive to school was five kilometers from home. Let s assume it took ten minutes to make the drive and that your parent was driving at a constant velocity the whole time. The position versus time graph for this section of the trip would look like that shown in [link] . A graph of position versus time for the drive to school is shown. What would the graph look like if we added the return trip? 

As we said before, d 0 = 0 because we call home our 0 and start calculating from there. In [link] , the line starts at d = 0, as well. This is the b in our equation for a straight line. Our initial position in a position versus time graph is always the place where the graph crosses the x -axis at t = 0. What is the slope? The rise is the change in position, (i.e., displacement) and the run is the change in time. This relationship can also be written: d t d t 

This relationship was how we defined average velocity. Therefore, the slope in a d versus t graph, is the average velocity. 

Sometimes, as is the case where we graph both the trip to school and the return trip, the behavior of the graph looks different during different time intervals. If the graph looks like a series of straight lines, then you can calculate the average velocity for each time interval by looking at the slope. If you then want to calculate the average velocity for the entire trip, you can do a weighted average. 

Let s look at another example. [link] shows a graph of position versus time for a jet-powered car on a very flat dry lake bed in Nevada. The diagram shows a graph of position versus time for a jet-powered car on the Bonneville Salt Flats. 

Using the relationship between dependent and independent variables, we see that the slope in the graph in [link] is average velocity, v avg and the intercept is displacement at time zero that is, d 0 . Substituting these symbols into y = mx + b gives d = v t + d 0 d = v t + d 0 

or d = d 0 + v t . d = d 0 + v t . 

Thus a graph of position versus time gives a general relationship among displacement, velocity, and time, as well as giving detailed numerical information about a specific situation. From the figure we can see that the car has a position of 400 m at t = 0 s, 650 m at t = 1.0 s, and so on. And we can learn about the object s velocity, as well. 

Help students learn what different graphs of displacement vs. time look like. 

[Visual] Set up a meter stick. If you can find a remote control car, have one student record times as you send the car forward along the stick, then backwards, then forward again with a constant velocity. Take the recorded times and the change in position and put them together. Get the students to coach you to draw a position vs. time graph. 

Each leg of the journey should be a straight line with a different slope. The parts where the car was going forward should have a positive slope. The part where it is going backwards would have a negative slope. 

[OL] Ask if the place that they take as zero affects the graph. 

[AL] Is it realistic to draw any position graph that starts at rest without some curve in it? Why might we be able to neglect the curve in some scenarios? 

[All]Discuss what can be uncovered from this graph. Students should be able to read the net displacement, but they can also use the graph to determine the total distance traveled. Then ask how the speed or velocity is reflected in this graph. Direct students in seeing that the steepness of the line (slope) is a measure of the speed and that the direction of the slope is the direction of the motion. 

[AL] Some students might recognize that a curve in the line represents a sort of slope of the slope, a preview of acceleration which they will learn about in the next chapter. Graphing Motion 

In this activity, you will release a ball down a ramp and graph the ball s displacement vs. time. Choose an open location with lots of space to spread out so there is less chance for tripping or falling due to rolling balls. 1 ball 1 board 2 or 3 books 1 stopwatch 1 tape measure 6 pieces of masking tape 1 piece of graph paper 1 pencil Build a ramp by placing one end of the board on top of the stack of books. Adjust location, as necessary, until there is no obstacle along the straight line path from the bottom of the ramp until at least the next 3 meters. Mark distances of 0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, 3.0 m from the bottom of the ramp. Write the distances on the tape. Have one person take the role of the experimenter. This person will release the ball from the top of the ramp. If the ball does not reach the 3.0 m mark, then increase the incline of the ramp by adding another book. Repeat this Step as necessary. Have the experimenter release the ball. Have a second person, the timer, begin timing the trial once the ball reaches the bottom of the ramp and stop the timing once the ball reaches 0.5 m. Have a third person, the recorder, record the time in a data table. Repeat Step 4, stopping the times at the distances of 1.0 m, 1.5 m, 2.0 m, 2.5 m, 3.0 m from the bottom of the ramp. Use your measurements of time and the displacement to make a position vs. time graph of the ball s motion. 

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[BL] [OL] Emphasize that the motion in this lab is the motion of the ball as it rolls along the floor. Ask students where there zero should be. 

[AL] Ask students what the graph would look like if they began timing at the top versus the bottom of the ramp. Why would the graph look different? What might account for the difference? Solving Problems Using Position vs. Time Graphs 

So how do we use graphs to solve for things we want to know like velocity? Using Position Time Graph to Calculate Average Velocity: Jet Car 

Find the average velocity of the car whose position is graphed in this figure . Strategy 

The slope of a graph of d vs. t is average velocity, since slope equals rise over run. slope = d t = v slope = d t = v 

Since the slope is constant here, any two points on the graph can be used to find the slope. Solution Choose two points on the line. In this case, we choose the points labeled on the graph: (6.4 s, 2000 m) and (0.50 s, 525 m). (Note, however, that you could choose any two points.) Substitute the d and t values of the chosen points into the equation. Remember in calculating change ( ) we always use final value minus initial value. 

v = d t = 2000 m 525 m 6.4 s 0.50 s = 250 m/s , v = d t = 2000 m 525 m 6.4 s 0.50 s = 250 m/s , Discussion 

This is an impressively high land speed (900 km/h, or about 560 mi/h): much greater than the typical highway speed limit of 60 mi/h (27 m/s or 96 km/h), but considerably shy of the record of 343 m/s (1234 km/h or 766 mi/h), set in 1997. 

If the graph of position is a straight line, then the only thing students need to know to calculate the average velocity is the slope of the line, rise/run. They can use whichever points on the line are most convenient. 

But what if the graph of the position is more complicated than a straight line? What if the object speeds up or turns around and goes backward? Can we figure out anything about its velocity from a graph of that kind of motion? Let s take another look at the jet-powered car. The graph in [link] shows its motion as it is getting up to speed after starting at rest. Time starts at zero for this motion (as if measured with a stopwatch), and the displacement and velocity are initially 200 m and 15 m/s, respectively. The diagram shows a graph of the position of a jet-powered car during the time span when it is speeding up. The slope of a distance versus time graph is velocity. This is shown at two points. Instantaneous velocity at any point is the slope of the tangent at that point. A U.S. Air Force jet car speeds down a track. (credit: Matt Trostle, Flickr) 

The graph of position versus time in [link] is a curve rather than a straight line. The slope of the curve becomes steeper as time progresses, showing that the velocity is increasing over time. The slope at any point on a position-versus-time graph is the instantaneous velocity at that point. It is found by drawing a straight line tangent to the curve at the point of interest and taking the slope of this straight line. Tangent lines are shown for two points in [link] . The average velocity is the net displacement divided by the time traveled. Using Position Time Graph to Calculate Average Velocity: Jet Car, Take Two 

Calculate the instantaneous velocity of the jet car at a time of 25 s by finding the slope of the tangent line at point Q in this figure . Strategy 

The slope of a curve at a point is equal to the slope of a straight line tangent to the curve at that point. Solution Find the tangent line to the curve at t = 25 s t = 25 s . Determine the endpoints of the tangent. These correspond to a position of 1300 m at time 19 s and a position of 3120 m at time 32 s. Plug these endpoints into the equation to solve for the slope, v . 

slope = v Q = d Q t Q = ( 3120 1300 ) m ( 32 19 ) s = 1820 m 13 s = 140 m/s slope = v Q = d Q t Q = ( 3120 1300 ) m ( 32 19 ) s = 1820 m 13 s = 140 m/s Discussion 

The entire graph of v versus t can be obtained in this fashion. 

A curved line is a more complicated example. Define tangent as a line that touches a curve at only one point. Show that as a straight line changes its angle next to a curve, it actually hits the curve multiple times at the base, but only one line will never touch at all. This line forms a right angle to the radius of curvature, but at this level, they can just kind of eyeball it. The slope of this line gives the instantaneous velocity. The most useful part of this line is that students can tell when the velocity is increasing, decreasing, positive, negative, and zero. 

[AL] You could find the instantaneous velocity at each point along the graph and if you graphed each of those points, you would have a graph of the velocity. Practice Problems 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify direct students to the relevant content. Section Summary Graphs can be used to analyze motion. The slope of a position vs. time graph is the velocity. For a straight line graph of position, the slope is the average velocity. To obtain the instantaneous velocity at a given moment for a curved graph, find the tangent line at that point and take its slope. Key Equations Displacement d = d 0 + v t d = d 0 + v t . Concept Items 

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[link] Glossary dependent variable the variable that changes as the independent variable changes independent variable the variable, usually along the horizontal axis of a graph, that does not change based on human or experimental action; in physics this is usually time tangent a line that touches another at exactly one pointVelocity vs. Time Graphs Velocity vs. Time Graphs 

By the end of this section, you will be able to: Explain the meaning of slope and area in velocity vs. time graphs Solve problems using velocity vs. time graphs 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4A) : generate and interpret graphs and charts describing different types of motion, including the use of real-time technology such as motion detectors or photogates. Section Key Terms acceleration 

Ask students to use their knowledge of position graphs to construct velocity vs. time graphs. Alternatively, provide an example of a velocity time graph and ask students what information can be derived from the graph. Ask: Is it the same information as in a position time graph? How is the information portrayed differently? Is there any new information in a velocity time graph? Graphing Velocity as a Function of Time 

Earlier, we examined graph s of position vs. time . Now, we are going to build on that information as we look at graphs of velocity vs. time. Velocity is the rate of change of displacement . Acceleration is the rate of change of velocity; we will discuss acceleration more in another chapter. These concepts are all very interrelated. Maze Game 

In this simulation you will use a vector diagram to manipulate a ball into a certain location without hitting a wall. You can manipulate the ball directly with position or by changing its velocity. Explore how these factors change the motion. If you would like, you can put it on the a setting, as well. This is acceleration, which measures the rate of change of velocity. We will explore acceleration in more detail later, but it might be interesting to take a look at it here. Click here for the simulation 

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What can we learn about motion by looking at velocity time graphs? Let s return to our drive to school, and look at a graph of position versus time as shown in [link] . A graph of position versus time for the drive to and from school is shown. 

We assumed for our original calculation that your parent drove with a constant velocity to and from school. We now know that the car could not have gone from rest to a constant velocity without speeding up. So the actual graph would be curved on either end, but let s make the same approximation as we did then, anyway. 

It is common in physics, especially at the early learning stages, for certain things to be neglected, as we see here. This is because it makes the concept clearer or the calculation easier. Practicing physicists use these kinds of short-cuts, as well. It works out because usually the thing being neglected is small enough that it does not significantly affect the answer. In the earlier example, the amount of time it takes the car to speed up and reach its cruising velocity is very small compared to the total time traveled. 

Looking at this graph, and given what we learned, we can see that there are two distinct periods to the car s motion the way to school and the way back. The average velocity for the drive to school is 0.5 km/minute. We can see that the average velocity for the drive back is 0.5 km/minute. If we plot the data showing velocity versus time, we get another graph ( [link] ): Graph of velocity versus time for the drive to and from school. 

We can learn a few things. First, we can derive a v versus t graph from a d versus t graph. Second, if we have a straight-line position time graph that is positively or negatively sloped, it will yield a horizontal velocity graph. There are a few other interesting things to note. Just as we could use a position time graph to determine velocity, we can use a velocity time graph to determine position. We know that v = d / t . If we use a little algebra to re-arrange the equation, we see that d = v t . In [link] , we have velocity on the y -axis and time along the x -axis. Let s take just the first half of the motion. We get 0.5 km/minute 10 minutes. The units for "minutes" cancel each other, and we get 5 km, which is the displacement for the trip to school. If we calculate the same for the return trip, we get 5 km. If we add them together, we see that the net displacement for the whole trip is 0 km, which it should be because we started and ended at the same place. 

You can treat units just like you treat numbers, so a km/km=1 (or, we say, it cancels out). This is good because it can tell us whether or not we have calculated everything with the correct units. For instance, if we end up with m s for velocity instead of m/s, we know that something has gone wrong, and we need to check our math. This process is called dimensional analysis, and it is one of the best ways to check if your math makes sense in physics. 

The area under a velocity curve represents the displacement. The velocity curve also tells us whether the car is speeding up. In our earlier example, we stated that the velocity was constant. So, the car is not speeding up. Graphically, you can see that the slope of these two lines is 0. This slope tells us that the car is not speeding up, or accelerating. We will do more with this information in a later chapter. For now, just remember that the area under the graph and the slope are the two important parts of the graph. Just like we could define a linear equation for the motion in a position time graph, we can also define one for a velocity time graph. As we said, the slope equals the acceleration, a . And in this graph, the y -intercept is v 0 . Thus, v = v 0 + a t v = v 0 + a t . 

But what if the velocity is not constant? Let s look back at our Jet-Car example. At the beginning of the motion, as the car is speeding up, we saw that its position is a curve, as shown in [link] . A graph is shown of the position of a jet-powered car during the time span when it is speeding up. The slope of a d vs. t graph is velocity. This is shown at two points. Instantaneous velocity at any point is the slope of the tangent at that point. 

You do not have to do this, but you could, theoretically, take the instantaneous velocity at each point on this graph. If you did, you would get [link] , which is just a straight line with a positive slope. The graph shows the velocity of a jet-powered car during the time span when it is speeding up. 

Again, if we take the slope of the velocity time graph, we get the acceleration, the rate of change of the velocity. And, if we take the area under the slope, we get back to the displacement. 

Return to the scenario of the drive to and from school. Re-draw the V-shaped position graph. Ask the students what the velocity is at different times on that graph. Students should then be able to see that the corresponding velocity graph is a horizontal line at 0.5km/minute and then a horizontal line at 0.5 km/minute. Then draw a few velocity graphs and see if they can get the corresponding position graph. 

[OL] [AL] Have students describe the relationship between the velocity and the position on these graphs. Ask: Can a velocity graph be used to find the position? Can a velocity graph be used to find anything else? 

[AL] What is wrong with this graph? Ask students whether the velocity could actually be constant from rest or shift to negative so quickly. What would more realistic graphs look like? How inaccurate is it to ignore the non-constant portion of the motion? 

[OL] Students should be able to see that if a position graph is a straight line, then the velocity graph will be a horizontal line. Also, the instantaneous velocity can be read off the velocity graph at any moment, but more steps are needed to calculate the average velocity. 

[AL] Guide students in seeing that the area under the velocity curve is actually the position and the slope represents the rate of change of the velocity, just as the slope of the position line represents the rate of change of the position. Solving Problems using Velocity Time Graphs 

Most velocity time graphs will be straight lines. When this is the case, our calculations are fairly simple. Using Velocity Graph to Calculate Some Stuff: Jet Car 

Use this figure to (a) find the displacement of the jet car over the time shown (b) calculate the rate of change (acceleration) of the velocity. (c) give the instantaneous velocity at 5 s, and (d) calculate the average velocity over the interval shown. Strategy The displacement is given by finding the area under the line in the velocity time graph. The acceleration is given by finding the slope of the velocity graph. The instantaneous velocity can just be read off of the graph. To find the average velocity, recall that v avg = d t = d f d 0 t f t 0 v avg = d t = d f d 0 t f t 0 Solution Analyze the shape of the area to be calculated. In this case, the area is made up of a rectangle between 0 and 20 m/s stretching to 30 s. The area of a rectangle is length width. Therefore, the area of this piece is 600 m. Above that is a triangle whose base is 30 s and height is 140 m/s. The area of a triangle is 0.5 length width. The area of this piece, therefore, is 2100 m. Add them together to get a net displacement of 2700 m. Take two points on the velocity line. Say, t = 5 s and t = 25 s. At t = 5 s, the value of v = 40 m/s. At t = 25 s, v = 140 m/s. Find the slope. a = v t = 100 m/s 20 s = 5 m/s 2 a = v t = 100 m/s 20 s = 5 m/s 2 The instantaneous velocity at t = 5 s , as we found in part (b) is just 40 m/s. Find the net displacement, which we found in part (a) was 2700 m. Find the total time which for this case is 30 s. Divide 2700 m/30 s = 90 m/s. Discussion 

The average velocity we calculated here makes sense if we look at the graph. 100m/s falls about halfway across the graph and since it is a straight line, we would expect about half the velocity to be above and half below. 

The quantities solved for are slightly different in the different kinds of graphs, but students should begin to see that the process of analyzing or breaking down any of these graphs is similar. Ask: Where are the turning points in the motion? When is the object moving forward? What does a curve in the graph mean? Also, students should start to have an intuitive understanding of the relationship between position and velocity graphs. 

You can have negative position, velocity, and acceleration on a graph that describes the way the object is moving. You should never see a graph with negative time on an axis. Why? 

Most of the velocity time graphs we will look at will be simple to interpret. Occasionally, we will look at curved graphs of velocity time. More often, these curved graphs occur when something is speeding up, often from rest. Let s look back at a more realistic velocity time graph of the jet car s motion that takes this speeding up stage into account. The graph shows a more accurate graph of the velocity of a jet-powered car during the time span when it is speeding up. Using Curvy Velocity Graph to Calculate Some Stuff: Jet Car, Take Two 

Use [link] to (a) find the approximate displacement of the Jet Car over the time shown, (b) calculate the instantaneous acceleration at t = 30 s, (c) find the instantaneous velocity at 30 s, and (d) calculate the approximate average velocity over the interval shown. Strategy Because this graph is an undefined curve, we have to estimate shapes over smaller intervals in order to find the areas. Like when we were working with a curved displacement graph, we will need to take a tangent line at the instant we are interested and use that to calculate the instantaneous acceleration. The instantaneous velocity can still be read off of the graph. We will find the average velocity the same way we did in the previous example. Solution This problem is more complicated than the last example. To get a good estimate, we should probably break the curve into four sections. 0 10 0 10 s, 10 20 10 20 s, 20 40 20 40 s, and 40 70 40 70 s. Calculate the bottom rectangle (common to all pieces). 165 m/s 70 s=11,550 m. Estimate a triangle at the top, and calculate the area for each section. Section 1=225 m; section 2=100 m + 450 m= 550 m; section 3=150 m + 1300 m=1450 m; section 4=2550 m. Add them together to get a net displacement of 16325 m. Using the tangent line given, we find that the slope is 1 m/s 2 . The instantaneous velocity at t = 30 s, is 240 m/s. Find the net displacement, which we found in part (a), was 16325 m. Find the total time, which for this case is 70 s. Divide 16325 m 70 s 233 m/s 16325 m 70 s 233 m/s Discussion 

This is a much more complicated process than the first problem. If we were to use these estimates to come up with the average velocity over just the first 30 s we would get about 191 m/s. By approximating that curve with a line, we get an average velocity of 202.5 m/s. Depending on our purposes and how precise an answer we need, sometimes calling a curve a straight line is a worthwhile approximation. 

Finding the tangent line can be a challenging concept for high school students, and they need to understand it theoretically. If you drew a regular curve inside of the curve at the point you are interested in, you could draw a radius of that curve. The tangent line would be the line perpendicular to that radius. 

[OL] Have the students compare this problem and the last one. Ask: What is the difference? When would you care about the more accurate picture of the motion? And when would it really not matter? Why would you ever want to look at a less accurate depiction of motion? Practice Problems 

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In this activity, you will graph a moving ball s velocity vs. time. Your graph from the earlier Graphing Motion Snap Lab! 1 Piece of graph paper 1 Pencil Take your graph from the earlier Graphing Motion Snap Lab! and use it to create a graph of velocity vs. time. Use your graph to calculate the displacement. 

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In this lab, students will use the displacement graph they drew in the last snap lab to create a velocity graph. If the rolling ball slowed down in the last snap lab, perhaps due to the ramp being too low, then the graph may not show constant velocity. Check Your Understanding 

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Use the Check Your Understanding questions to assess students achievement of the section s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help direct students to the relevant content. Section Summary The slope of a velocity time graph is the acceleration. The area under a velocity time curve is the displacement. Average velocity can be found in a velocity time graph by taking the weighted average of all the velocities. Key Equations Velocity v = v 0 + a t v = v 0 + a t Acceleration a = v t a = v t Concept Items 

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The National Mall in Washington, DC, is a national park containing most of the highly treasured memorials and museums of the United States. However, the National Mall also hosts many events and concerts. The map in [link] shows the area for a benefit concert during which the president will speak. The concert stage is near the Lincoln Memorial. The seats and standing room for the crowd will stretch from the stage east to near the Washington Monument, as shown on the map. You are planning the logistics for the concert. Use the map scale to measure any distances needed to make the calculations below. 

The park has three new long-distance speakers. They would like to use these speakers to broadcast the concert audio to other parts of the National Mall. The speakers can project sound up to 0.35 miles away but they must be connected to one of the power supplies within the concert area (see map ). What is the minimum amount of wire needed for each speaker, in feet to the nearest foot, in order to project the audio to the following areas? Assume that wire cannot be placed over water, buildings or any memorials. The center of the Jefferson Memorial using power supply 1 The center of the Ellipse using power supply 2 The center of the lawn area between 14th Street and the Smithsonian metro station. How long will it take a concert-goer, in minutes, to travel from the Smithsonian metro to the eastern border of the concert area? Assume visitors are walking at an average speed of 3.0 mi/hour. The president s motorcade will be traveling to the concert from the White House. To avoid concert traffic, the motorcade travels from the White House west down E Street and then turns south on 23rd Street to reach the Lincoln memorial. What minimum speed, in miles per hour to the nearest tenth, would the motorcade have to travel to make the trip in 5 minutes? The president could also simply fly from the White House to the Lincoln Memorial using the presidential helicopter, Marine 1. How long would it take Marine 1, traveling slowly at 30 mph, to travel from directly above the White House landing zone (LZ) to directly above the Lincoln Memorial LZ? Disregard liftoff and landing times and report the travel time in minutes to the nearest minute. 

The content in this chapter will help your students master the following NGSS: 

HS-PS2-1: Analyze data to support the claim that Newton's second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. Test Prep Multiple Choice 

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[link] Glossary acceleration the rate at which velocity changesAngle of Rotation and Angular Velocity Angle of Rotation and Angular Velocity Section Learning Objectives 

By the end of this section, you will be able to: Describe the angle of rotation and relate it to its linear counterpart Describe angular velocity and relate it to its linear counterpart Solve problems involving angle of rotation and angular velocity 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4C) : Analyze and describe accelerated motion in two dimensions using equations, including projectile and circular examples Section Key Terms angle of rotation angular velocity arc length circular motion radius of curvature rotational motion spin tangential velocity Angle of Rotation 

What exactly do we mean by circular motion or rotation ? Rotational motion is the circular motion of an object about an axis of rotation. We will discuss specifically circular motion and spin. Circular motion is when an object moves in a circular path. Examples of circular motion include a race car speeding around a circular curve, a toy attached to a string swinging in a circle around your head, or the circular loop-the-loop on a roller coaster. Spin is rotation about an axis that goes through the center of mass of the object, such as Earth rotating on its axis, a wheel turning on its axle, the spin of a tornado on its path of destruction, or a figure skater spinning during a performance at the Olympics. Sometimes, objects will be spinning while in circular motion, like the Earth spinning on its axis while revolving around the Sun, but we will focus on these two motions separately. 

[BL] [OL] Explain the difference between circular and rotational motions by using the Earth s rotation about its axis and its revolution about the Sun. Explain that Earth s rotation is slightly elliptical, although it is very nearly circular. 

[OL] [AL] Ask students to come up with examples of circular motion. 

When solving problems involving rotational motion, we use variables that are similar to linear variables (distance, velocity, acceleration, and force) but take into account the curvature or rotation of the motion. Here, we define the angle of rotation , which is the angular equivalence of distance; and angular velocity , which is the angular equivalence of linear velocity. 

When objects rotate about some axis for example, when the CD in [link] rotates about its center each point in the object follows a circular path. All points on a CD travel in circular paths. The pits (dots) along a line from the center to the edge all move through the same angle in time t t . 

The arc length , , is the distance traveled along a circular path. The radius of curvature , r , is the radius of the circular path. Both are shown in [link] . The radius ( r ) of a circle is rotated through an angle . The arc length, s s , is the distance covered along the circumference. 

Consider a line from the center of the CD to its edge. In a given time, each pit (used to record information) on this line moves through the same angle. The angle of rotation is the amount of rotation and is the angular analog of distance. The angle of rotation is the arc length divided by the radius of curvature: = s r = s r 

The angle of rotation is often measured by using a unit called the radian . (Radians are actually dimensionless, because a radian is defined as the ratio of two distances, radius and arc length.) A revolution is one complete rotation, where every point on the circle returns to its original position. One revolution covers 2 2 radians (or 360 degrees), and therefore has an angle of rotation of 2 2 radians, and an arc length that is the same as the circumference of the circle. We can convert between radians, revolutions, and degrees using the relationship 

1 revolution = 2 2 rad = 360 . See [link] for the conversion of degrees to radians for some common angles. 

2 rad = 360 1 rad = 360 2 57.3 2 rad = 360 1 rad = 360 2 57.3 Commonly Used Angles in Terms of Degrees and Radians Degree Measures Radian Measures 30 30 6 6 60 60 3 3 90 90 2 2 120 120 2 3 2 3 135 135 3 4 3 4 180 180 Angular Velocity 

[BL] Review displacement, speed, velocity, acceleration. 

[AL] Ask students whether or not velocity changes in uniform circular motion. What about speed? What about acceleration? 

How fast is an object rotating? We can answer this question by using the concept of angular velocity. Consider first the angular speed, , is the rate at which the angle of rotation changes. In equation form, the angular speed is 

= t = t , 

which means that an angular rotation, , occurs in a time, t t . If an object rotates through a greater angle of rotation in a given time, it has a greater angular speed. The units for angular speed are radians per second (rad/s). 

Now let s consider the direction of the angular speed, which means we now must call it the angular velocity. The direction of the angular velocity is along the axis of rotation. For an object rotating clockwise, the angular velocity points away from you along the axis of rotation. For an object rotating counterclockwise, the angular velocity points toward you along the axis of rotation. 

Angular velocity, , is the angular version of linear velocity, v . Tangential velocity is the instantaneous linear velocity of an object in rotational motion . To get the precise relationship between angular velocity and tangential velocity, consider again a pit on the rotating CD. This pit moves through an arc length, s s , in a short time, t t , so its tangential speed is v = s t v = s t 

From the definition of the angle of rotation, = s r = s r , we see that s = r s = r . Substituting this into the expression for v gives v = r t = r v = r t = r 

The equation v = r v = r says that the tangential speed, v, is proportional to the distance r from the center of rotation. Consequently, tangential speed is greater for a point on the outer edge of the CD (with larger r ) than for a point closer to the center of the CD (with smaller r ). This makes sense because a point farther out from the center has to cover a longer arc length in the same amount of time as a point closer to the center. Note that both points will still have the same angular speed, regardless of their distance from the center of rotation. See [link] . Points 1 and 2 rotate through the same angle ( ), but point 2 moves through a greater arc length ( s 2 s 2 ) because it is farther from the center of rotation. 

[AL] Explain that the time period t t in the equation that defines tangential velocity ( v = s t v = s t ) must be short so that the arc described by the moving object can be approximated as a straight line. This allows us to define the direction of the tangential velocity as being tangent to the circle. This approximation becomes increasingly accurate as t t becomes increasingly small. 

Now, consider another example: the tire of a moving car (see [link] ). The faster the tire spins, the faster the car moves large means large v because v = r v = r . Similarly, a larger-radius tire rotating at the same angular velocity, , will produce a greater linear (tangential) velocity, v, for the car. This is because a larger radius means a longer arc length must contact the road, so the car must move farther in the same amount of time. A car moving at a velocity, v, to the right has a tire rotating with angular velocity . The speed of the tread of the tire relative to the axle is v , the same as if the car were jacked up and the wheels spinning without touching the road. Directly below the axle, where the tire touches the road, the tire tread moves backward with respect to the axle with tangential velocity v = r v = r , where r is the tire radius. Because the road is stationary with respect to this point of the tire, the car must move forward at the linear velocity v . A larger angular velocity for the tire means a greater linear velocity for the car. 

However, there are cases where linear velocity and tangential velocity are not equivalent, such as a car spinning its tires on ice. In this case, the linear velocity will be less than the tangential velocity. Due to the lack of friction under the tires of a car on ice, the arc length through which the tire treads move is greater than the linear distance through which the car moves. It s similar to running on a treadmill or pedaling a stationary bike; you are literally going nowhere fast. 

Angular velocity and tangential velocity v are vectors, so we must include magnitude and direction. The direction of the angular velocity is along the axis of rotation, and points away from you for an object rotating clockwise, and toward you for an object rotating counterclockwise. In mathematics this is described by the right-hand rule. Tangential velocity is usually described as up, down, left, right, north, south, east, or west, as shown in [link] . As the fly on the edge of an old-fashioned vinyl record moves in a circle, its instantaneous velocity is always at a tangent to the circle. The direction of the angular velocity is into the page this case. Relationship between Angular Velocity and Speed 

This video reviews the definition and units of angular velocity and relates it to linear speed. It also shows how to convert between revolutions and radians. 

[link] Solving Problems Involving Angle of Rotation and Angular Velocity Measuring Angular Speed 

In this activity, you will create and measure uniform circular motion and then contrast it with circular motions with different radii. 1 string (1 m long) 1 object (2-hole rubber stopper) to tie to the end 1 timer Tie an object to the end of a string. Swing the object around in a horizontal circle above your head (swing from your wrist). It is important that the circle be horizontal! Maintain the object at uniform speed as it swings. Measure the angular speed of the object in this manner. Measure the time it takes for the object to travel 10 revolutions. Divide that time by 10 to get the angular speed in revolutions per second, which you can convert to radians per second. What is the approximate linear speed of the object? Move your hand up the string so that the length of the string is 90 cm. Repeat steps 2 5. Move your hand up the string so that its length is 80 cm. Repeat steps 2 5. Move your hand up the string so that its length is 70 cm. Repeat steps 2 5. Move your hand up the string so that its length is 60 cm. Repeat steps 2 5 Move your hand up the string so that its length is 50 cm. Repeat steps 2 5 Make graphs of angular speed vs. radius (i.e. string length) and linear speed vs. radius. Describe what each graph looks like. 

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Now that we have an understanding of the concepts of angle of rotation and angular velocity, we ll apply them to the real-world situations of a clock tower and a spinning tire. Angle of rotation at a Clock Tower 

The clock on a clock tower has a radius of 1.0 m. (a) What s the angle of rotation between the hour hand of the clock when it moves from 12 pm to 3 pm? (b) What s the arc length along the outermost edge of the clock between the hour hand at these two times? Strategy 

We can figure out the angle of rotation by multiplying a full revolution ( 2 2 radians) by the fraction of the 12 hours covered by the hour hand in going from 12 to 3. Once we have the angle of rotation, we can solve for the arc length by rearranging the equation = s r = s r since the radius is given. Solution to (a) 

In going from 12 to 3, the hour hand covers 1/4 of the 12 hours needed to make a complete revolution. Therefore, the angle between the hour hand at 12 and at 3 is 1 4 2 rad = 2 1 4 2 rad = 2 (i.e., 90 degrees). Solution to (b) 

Rearranging the equation 

= s r = s r , 

we get 

s = r s = r . 

Inserting the known values gives an arc length of 

s = ( 1.0 m ) ( 2 rad ) = 1.6 m s = ( 1.0 m ) ( 2 rad ) = 1.6 m Discussion 

We were able to drop the radians from the final solution to part (b) because radians are actually dimensionless. This is because the radian is defined as the ratio of two distances (radius and arc length). Thus, the formula gives an answer in units of meters, as expected for an arc length. How Fast Does a Car Tire Spin? 

Calculate the angular speed of a 0.300 m radius car tire when the car travels at 15.0 m/s (about 54 km/h). See this figure . Strategy 

In this case, the speed of the tire tread with respect to the tire axle is the same as the speed of the car with respect to the road, so we have v = 15.0 m/s. The radius of the tire is r = 0.300 m. Since we know v and r , we can rearrange the equation v = r v = r , to get = v r = v r and find the angular speed. Solution 

To find the angular speed, we use the relationship: = v r = v r . 

Inserting the known quantities gives: 

= 15.0 m/s 0.300 m = 50.0 rad/s = 15.0 m/s 0.300 m = 50.0 rad/s Discussion 

When we cancel units in the above calculation, we get 50.0/s (i.e., 50.0 per second, which is usually written as 50.0 s 1). But the angular speed must have units of rad/s. Because radians are dimensionless, we can insert them into the answer for the angular speed because we know that the motion is circular. Also note that, if an earth mover with much larger tires, say 1.20 m in radius, were moving at the same speed of 15.0 m/s, its tires would rotate more slowly. They would have an angular speed of 

= 15.0 m/s 1.20 m = 12.5 rad/s = 15.0 m/s 1.20 m = 12.5 rad/s Practice Problems 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the formative assessment will help identify which objective is causing the problem and direct students to the relevant content. Section Summary Circular motion is motion in a circular path. The angle of rotation is defined as the ratio of the arc length to the radius of curvature. The arc length s s is the distance traveled along a circular path and r is the radius of curvature of the circular path. The angle of rotation is measured in units of radians (rad), where 2 rad = 360 = 1 2 rad = 360 = 1 revolution. Angular velocity is the rate of change of an angle, where a rotation occurs in a time t t . The units of angular velocity are radians per second (rad/s). Tangential speed v and angular speed are related by v = r v = r , and tangential velocity has units of m/s. The direction of angular velocity is along the axis of rotation, toward (away) from you for clockwise (counterclockwise) motion. Key Equations Angle of rotation = s r = s r Angular speed: = t = t Tangential speed: v = r v = r Concept Items 

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[link] Glossary angle of rotation the ratio of the arc length to the radius of curvature of a circular path angular velocity ( ) the rate of change in the angular position of an object following a circular path arc length ( s s ) the distance traveled by an object along a circular path circular motion the motion of an object along a circular path radius of curvature the distance between the center of a circular path and the path rotational motion the circular motion of an object about an axis of rotation spin rotation about an axis that goes through the center of mass of the object tangential velocity the instantaneous linear velocity of an object in circular or rotational motionIntroduction Introduction In this chapter you will learn about: Angle of rotation and angular velocity Uniform circular motion Rotational motion class="summary" title="Section Summary" class="key-equations" title="Key Equations" class="concept" title="Concept Items" class="critical-thinking" title="Critical Thinking Items" class="problem" title="Problems" class="performance" title="Performance Task" class="multiple-choice" title="Multiple Choice" class="short-answer" title="Short Answer" class="extended-response" title="Extended Response" This Australian Grand Prix Formula 1 race car moves in a circular path as it makes the turn. Its wheels also spin rapidly. The same physical principles are involved in both of these motions. (credit: Richard Munckton). 

Before students begin this chapter, they may wish to review the concepts of distance, displacement, speed, velocity, acceleration, force and Newton s laws of motion. Address misconception about centrifugal force. 

Point out that we come across circular motion in our everyday lives; for instance, a car tire spinning, a fan rotating, and so forth. This chapter is about the quantities that describe rotational motion and the relationships between them. 

You may recall learning about various aspects of motion along a straight line: kinematics (where we learned about displacement, velocity, and acceleration), projectile motion (a special case of two-dimensional kinematics), force, and Newton s laws of motion. In some ways, this chapter is a continuation of Newton s laws of motion. Recall that Newton s first law tells us that objects move along a straight line at constant speed unless a net external force acts on them. Therefore, if an object moves along a circular path, such as the car in the photo, it must be experiencing an external force. In this chapter, we explore both circular motion and rotational motion.Uniform Circular Motion Uniform Circular Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe centripetal acceleration and relate it to linear acceleration Describe centripetal force and relate it to linear force Solve problems involving centripetal acceleration and centripetal force 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4C) : Analyze and describe accelerated motion in two dimensions using equations, including projectile and circular examples (4D) : Calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects Section Key Terms centrifugal force centripetal acceleration centripetal force uniform circular motion Centripetal Acceleration 

[BL] [OL] Review uniform circular motion. Ask students to give examples of circular motion. Review linear acceleration. 

In the previous section, we defined circular motion . The simplest case of circular motion is uniform circular motion , where an object travels a circular path at a constant speed . Note that, unlike speed, the linear velocity of an object in circular motion is constantly changing because it is always changing direction. We know from kinematics that acceleration is a change in velocity , either in magnitude or in direction or both. Therefore, an object undergoing uniform circular motion is always accelerating, even though the magnitude of its velocity is constant. 

You experience this acceleration yourself every time you ride in a car while it turns a corner. If you hold the steering wheel steady during the turn and move at a constant speed, you are executing uniform circular motion. What you notice is a feeling of sliding (or being flung, depending on the speed) away from the center of the turn. This isn t an actual force that is acting on you it only happens because your body wants to continue moving in a straight line (as per Newton s first law) whereas the car is turning off this straight-line path. Inside the car it appears as if you are forced away from the center of the turn. This fictitious force is known as the centrifugal force . The sharper the curve and the greater your speed, the more noticeable this effect becomes. 

[BL] [OL] [AL] Demonstrate circular motion by tying a weight to a string and twirling it around. Ask students what would happen if you suddenly cut the string? In which direction would the object travel? Why? What does this say about the direction of acceleration? Ask students to give examples of when they have come across centripetal acceleration. 

[link] shows an object moving in a circular path at constant speed. The direction of the instantaneous tangential velocity is shown at two points along the path. Acceleration is in the direction of the change in velocity; in this case it points roughly toward the center of rotation. (The center of rotation is at the center of the circular path). If we imagine s s becoming smaller and smaller, then the acceleration would point exactly toward the center of rotation, but this case is hard to draw. We call the acceleration of an object moving in uniform circular motion the centripetal acceleration a c because centripetal means center seeking. The directions of the velocity of an object at two different points are shown, and the change in velocity v v is seen to point approximately toward the center of curvature (see small inset). For an extremely small value of s s , v v points exactly toward the center of the circle (but this is hard to draw). Because a c = v / t a c = v / t , the acceleration is also toward the center, so a c is called centripetal acceleration. 

Consider [link] . The figure shows an object moving in a circular path at constant speed and the direction of the instantaneous velocity of two points along the path. Acceleration is in the direction of the change in velocity and points toward the center of rotation. This is strictly true only as s s tends to zero. 

Now that we know that the direction of centripetal acceleration is toward the center of rotation, let s discuss the magnitude of centripetal acceleration. For an object traveling at speed v in a circular path with radius r , the magnitude of centripetal acceleration is a c = v 2 r a c = v 2 r 

Centripetal acceleration is greater at high speeds and in sharp curves (smaller radius), as you may have noticed when driving a car, because the car actually pushes you toward the center of the turn. But it is a bit surprising that a c is proportional to the speed squared. This means, for example, that the acceleration is four times greater when you take a curve at 100 km/h than at 50 km/h. 

We can also express a c in terms of the magnitude of angular velocity . Substituting v = r v = r into the equation above, we get a c = ( r ) 2 / r = r 2 a c = ( r ) 2 / r = r 2 . Therefore, the magnitude of centripetal acceleration in terms of the magnitude of angular velocity is a c = r 2 a c = r 2 . 

The equation expressed in the form a c = r 2 is useful for solving problems where you know the angular velocity rather than the tangential velocity. Ladybug Motion in 2D 

In this simulation, you experiment with the position, velocity, and acceleration of a ladybug in circular and elliptical motion. Switch the type of motion from linear to circular and observe the velocity and acceleration vectors. Next, try elliptical motion and notice how the velocity and acceleration vectors differ from those in circular motion. Click here for the simulation 

[link] Centripetal Force 

[BL] [OL] [AL] Using the same demonstration as before, ask students to predict the relationships between the quantities of angular velocity, centripetal acceleration, mass, centripetal force. Invite students to experiment by using various lengths of string and different weights. 

Because an object in uniform circular motion undergoes constant acceleration (by changing direction), we know from Newton s second law of motion that there must be a constant net external force acting on the object. 

Any force or combination of forces can cause a centripetal acceleration. Just a few examples are the tension in the rope on a tether ball, the force of Earth s gravity on the Moon, the friction between a road and the tires of a car as it goes around a curve, or the normal force of a roller coaster track on the cart during a loop the loop. 

Any net force causing uniform circular motion is called a centripetal force . The direction of a centripetal force is toward the center of rotation, the same as for centripetal acceleration. According to Newton s second law of motion, a net force causes the acceleration of mass according to F net = m a . For uniform circular motion, the acceleration is centripetal acceleration: a = a c . Therefore, the magnitude of centripetal force, F c , is F c = m a c F c = m a c . 

By using the two different forms of the equation for the magnitude of centripetal acceleration, a c = v 2 / r a c = v 2 / r and a c = r 2 a c = r 2 , we get two expressions involving the magnitude of the centripetal force F c . The first expression is in terms of tangential speed, the second is in terms of angular speed: F c = m v 2 r F c = m v 2 r and F c = m r 2 F c = m r 2 . 

Both forms of the equation depend on mass, velocity, and the radius of the circular path. You may use whichever expression for centripetal force is more convenient. Newton s second law also states that the object will accelerate in the same direction as the net force. By definition, the centripetal force is directed towards the center of rotation, so the object will also accelerate towards the center. A straight line drawn from the circular path to the center of the circle will always be perpendicular to the tangential velocity. Note that, if you solve the first expression for r , you get: r = m v 2 F c r = m v 2 F c 

From this expression, we see that, for a given mass and velocity, a large centripetal force causes a small radius of curvature that is, a tight curve. In this figure, the frictional force ( f ) serves as the centripetal force ( F c ). Centripetal force is perpendicular to tangential velocity and causes uniform circular motion. The larger the centripetal force F c , the smaller is the radius of curvature r and the sharper is the curve. The lower curve has the same velocity v , but a larger centripetal force F c produces a smaller radius r r . Centripetal Force and Acceleration Intuition 

This video explains why a centripetal force creates centripetal acceleration and uniform circular motion. It also covers the difference between speed and velocity and shows examples of uniform circular motion. 

Some students might be confused between centripetal force and centrifugal force. Centrifugal force is not a real force but the result of an accelerating reference frame, such as a turning car or the spinning Earth. Centrifugal force refers to a fictional center fleeing force. 

[link] Solving Centripetal Acceleration and Centripetal Force Problems 

To get a feel for the typical magnitudes of centripetal acceleration, we ll do a lab estimating the centripetal acceleration of a tennis racket and then, in our first Worked Example, compare the centripetal acceleration of a car rounding a curve to gravitational acceleration. For the second Worked Example, we ll calculate the force required to make a car round a curve. Estimating Centripetal Acceleration 

In this activity, you will measure the swing of a golf club or tennis racket to estimate the centripetal acceleration of the end of the club or racket. You may choose to do this in slow motion. Recall that the equation for centripetal acceleration is a c = v 2 r a c = v 2 r or a c = r 2 a c = r 2 . 1 tennis racket or golf club 1 timer 1 ruler or tape measure Work with a partner. Stand a safe distance away from your partner as he or she swings the golf club or tennis racket. Describe the motion of the swing is this uniform circular motion? Why or why not? Try to get the swing as close to uniform circular motion as possible. What adjustments did your partner need to make? Measure the radius of curvature. What did you physically measure? By using the timer, find either the linear or angular velocity, depending on which equation you decide to use. What is the approximate centripetal acceleration based on these measurements? How accurate do you think they are? Why? How might you and your partner make these measurements more accurate? 

The swing of the golf club or racket can be made very close to uniform circular motion. For this, the person would have to move it at a constant speed, without bending their arm. The length of the arm plus the length of the club or racket is the radius of curvature. Accuracy of measurements of angular velocity and angular acceleration will depend on resolution of the timer used and human observational error.The swing of the golf club or racket can be made very close to uniform circular motion. For this, the person would have to move it at a constant speed, without bending their arm. The length of the arm plus the length of the club or racket is the radius of curvature. Accuracy of measurements of angular velocity and angular acceleration will depend on resolution of the timer used and human observational error. 

[link] Comparing Centripetal Acceleration of a Car Rounding a Curve with Acceleration Due to Gravity 

A car follows a curve of radius 500 m at a speed of 25.0 m/s (about 90 km/h). What is the magnitude of the car s centripetal acceleration? Compare the centripetal acceleration for this fairly gentle curve taken at highway speed with acceleration due to gravity ( g ). Strategy 

Because linear rather than angular speed is given, it is most convenient to use the expression a c = v 2 r a c = v 2 r to find the magnitude of the centripetal acceleration. Solution 

Entering the given values of v = 25.0 m/s and r = 500 m into the expression for a c gives a c = v 2 r = ( 25.0 m/s ) 2 500 m = 1.25 m/s 2 a c = v 2 r = ( 25.0 m/s ) 2 500 m = 1.25 m/s 2 Discussion 

To compare this with the acceleration due to gravity ( g = 9.80 m/s 2 ), we take the ratio a c / g = ( 1.25 m/s 2 ) / ( 9.80 m/s 2 ) = 0.128 a c / g = ( 1.25 m/s 2 ) / ( 9.80 m/s 2 ) = 0.128 . Therefore, a c = 0.128 g a c = 0.128 g , which means that the centripetal acceleration is about one tenth the acceleration due to gravity. This acceleration is still noticeable, especially if you are not wearing a seat belt. Frictional Force on Car Tires Rounding a Curve Calculate the centripetal force exerted on a 900 kg car that rounds a 600-m-radius curve on horizontal ground at 25.0 m/s. Static friction prevents the car from slipping. Find the magnitude of the frictional force between the tires and the road that allows the car to round the curve without sliding off in a straight line. Strategy and Solution for (a) 

We know that F c = m v 2 r F c = m v 2 r . Therefore, F c = m v 2 r = ( 900 kg ) ( 25.0 m/s ) 2 600 m = 938 N F c = m v 2 r = ( 900 kg ) ( 25.0 m/s ) 2 600 m = 938 N Strategy and Solution for (b) 

The image above shows the forces acting on the car while rounding the curve. In this diagram, the car is traveling into the page as shown and is turning to the left. Friction acts toward the left, accelerating the car toward the center of the curve. Because friction is the only horizontal force acting on the car, it provides all of the centripetal force in this case. Therefore, the force of friction is the centripetal force in this situation and points toward the center of the curve. f = F c = 938 N f = F c = 938 N Discussion 

Since we found the force of friction in part (b), we could also solve for the coefficient of friction, since f = s N = s m g f = s N = s m g . Practice Problems 

[link] 

[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, the formative assessment will help identify which objective is causing the problem and direct students to the relevant content. Section Summary Centripetal acceleration a c is the acceleration experienced while in uniform circular motion. Centripetal acceleration force is a center-seeking force that always points toward the center of rotation, perpendicular to the linear velocity, in the same direction as the net force, and in the direction opposite that of the radius vector. The standard unit for centripetal acceleration is m/s 2 . Centripetal force F c is any net force causing uniform circular motion. Key Equations Centripetal acceleration a c = v 2 r a c = v 2 r or a c = r 2 a c = r 2 Centripetal force F c = m a c F c = m a c , F c = m v 2 r F c = m v 2 r , F c = m r 2 F c = m r 2 Concept Items 

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[link] Critical Thinking 

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[link] Glossary centrifugal force a fictitious force that acts in the direction opposite the centripetal acceleration centripetal acceleration the acceleration of an object moving in a circle, directed toward the center of the circle centripetal force any force causing uniform circular motion uniform circular motion the motion of an object in a circular path at constant speedRotational Motion Rotational Motion Section Learning Objectives 

By the end of this section, you will be able to: Describe rotational kinematic variables and equations and relate them to their linear counterparts Describe torque and lever arm Solve problems involving torque and rotational kinematics 

The learning objectives in this section will help your students master the following TEKS: (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (4C) : Analyze and describe accelerated motion in two dimensions using equations, including projectile and circular examples (4D) : Calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects Section Key Terms angular acceleration kinematics of rotational motion lever arm tangential acceleration torque Rotational Kinematics 

[BL] [OL] Review linear kinematic equations. 

Students may get confused between deceleration and increasing acceleration in the negative direction. 

In the section on uniform circular motion, we discussed motion in a circle at constant speed and, therefore, constant angular velocity. However, there are times when angular velocity is not constant rotational motion can speed up, slow down, or reverse directions. Angular velocity is not constant when a spinning skater pulls in her arms, when a child pushes a merry-go-round to make it rotate, or when a CD slows to a halt when switched off. In all these cases, angular acceleration occurs because the angular velocity changes. The faster the change occurs, the greater is the angular acceleration. Angular acceleration is the rate of change of angular velocity. In equation form, angular acceleration is = t = t 

where is the change in angular velocity and t t is the change in time. The units of angular acceleration are (rad/s)/s, or rad/s 2 . If increases, then is positive. If decreases, then is negative. Keep in mind that, by convention, counterclockwise is the positive direction and clockwise is the negative direction. For example, the skater in [link] is rotating counterclockwise as seen from above, so her angular velocity is positive. Acceleration would be negative, for example, when an object that is rotating counterclockwise slows down. It would be positive when an object that is rotating counterclockwise speeds up. A figure skater spins in the counterclockwise direction, so her angular velocity is normally considered to be positive. (credit: Luu, Wikimedia Commons) 

The relationship between the magnitudes of tangential acceleration , a , and angular acceleration, , is a = r or = a r , is a = r or = a r 

These equations mean that the magnitudes of tangential acceleration and angular acceleration are directly proportional to each other. The greater the angular acceleration, the larger the change in tangential acceleration, and vice versa. For example, consider riders in their pods on a Ferris wheel at rest. A Ferris wheel with greater angular acceleration will give the riders greater tangential acceleration because, as the Ferris wheel increases its rate of spinning, it also increases its tangential velocity . Note that the radius of the spinning object also matters. For example, for a given angular acceleration , a smaller Ferris wheel leads to a smaller tangential acceleration for the riders. 

Tangential acceleration is sometimes denoted a t . It is a linear acceleration in a direction tangent to the circle at the point of interest in circular or rotational motion. Remember that tangential acceleration is parallel to the tangential velocity (either in the same direction or in the opposite direction.) Centripetal acceleration is always perpendicular to the tangential velocity. 

So far, we have defined three rotational variables: , , and . These are the angular versions of the linear variables x , v , and a . [link] shows how they are related. Rotational and Linear Variables Rotational Linear Relationship x = x r = x r v = v r = v r a = a r = a r 

We can now begin to see how rotational quantities like , , and are related to each other. For example, if a motorcycle wheel that starts at rest has a large angular acceleration for a fairly long time, it ends up spinning rapidly and rotates through many revolutions. Putting this in terms of the variables, if the wheel s angular acceleration is large for a long period of time t , then the final angular velocity and angle of rotation are large. In the case of linear motion, if an object starts at rest and undergoes a large linear acceleration, then it has a large final velocity and will have traveled a large distance. 

The kinematics of rotational motion describes the relationships between the angle of rotation, angular velocity, angular acceleration, and time. It only describes motion it does not include any forces or masses that may affect rotation (these are part of dynamics). Recall the kinematics equation for linear motion: v = v 0 + a t v = v 0 + a t (constant a ) 

As in linear kinematics, we assume a is constant, which means that angular acceleration is also a constant, because a = r a = r . The equation for the kinematics relationship between , , and t is 

= 0 + t ( constant ) , = 0 + t ( constant ) , 

where 0 0 is the initial angular velocity. Notice that the equation is identical to the linear version, except with angular analogs of the linear variables. In fact, all of the linear kinematics equations have rotational analogs, which are given in [link] . These equations can be used to solve rotational or linear kinematics problem in which a and are constant. Equations for Rotational Kinematics Rotational Linear = t = t x = v t x = v t = 0 + t = 0 + t v = v 0 + t v = v 0 + t constant , a = 0 t + 1 2 t 2 = 0 t + 1 2 t 2 x = v 0 t + 1 2 t 2 x = v 0 t + 1 2 t 2 constant , a 2 = 0 2 + 2 2 = 0 2 + 2 v 2 = v 0 2 + 2 x v 2 = v 0 2 + 2 x constant , a 

In these equations, 0 0 and v 0 v 0 are initial values, t 0 t 0 is zero, and the average angular velocity, and average velocity v v are 

= 0 + 2 and v = v 0 + v 2 = 0 + 2 and v = v 0 + v 2 Storm Chasing Tornadoes descend from clouds in funnel-like shapes that spin violently. (credit: Daphne Zaras, U.S. National Oceanic and Atmospheric Administration) 

Storm chasers tend to fall into one of three groups: Amateurs chasing tornadoes as a hobby, atmospheric scientists gathering data for research, weather watchers for news media, or scientists having fun under the guise of work. Storm chasing is a dangerous pastime because tornadoes can change course rapidly with little warning. Since storm chasers follow in the wake of the destruction left by tornadoes, changing flat tires due to debris left on the highway is common. The most active part of the world for tornadoes, called tornado alley, is in the central United States, between the Rocky Mountains and Appalachian Mountains. 

Tornadoes are perfect examples of rotational motion in action in nature. They come out of severe thunderstorms called supercells, which have a column of air rotating around a horizontal axis, usually about four miles across. The difference in wind speeds between the strong cold winds higher up in the atmosphere in the jet stream and weaker winds traveling north from the Gulf of Mexico causes the column of rotating air to shift so that it spins around a vertical axis, creating a tornado. 

Tornadoes produce wind speeds as high as 500 km/h (approximately 300 miles/h), particularly at the bottom where the funnel is narrowest because the rate of rotation increases as the radius decreases. They blow houses away as if they were made of paper and have been known to pierce tree trunks with pieces of straw. 

[link] Torque 

If you have ever spun a bike wheel or pushed a merry-go-round, you know that force is needed to change angular velocity. The farther the force is applied from the pivot point (or fulcrum ), the greater the angular acceleration. For example, a door opens slowly if you push too close to its hinge, but opens easily if you push far from the hinges. Furthermore, we know that the more massive the door is, the more slowly it opens; this is because angular acceleration is inversely proportional to mass. These relationships are very similar to the relationships between force, mass, and acceleration from Newton s second law of motion. Since we have already covered the angular versions of distance, velocity and time, you may wonder what the angular version of force is, and how it relates to linear force. 

The angular version of force is torque , which is the turning effectiveness of a force. See [link] . The equation for the magnitude of torque is = r F sin , = r F sin , 

where r is the magnitude of the lever arm , F is the magnitude of the linear force, and is the angle between the lever arm and the force. The lever arm is the vector from the point of rotation (pivot point or fulcrum) to the location where force is applied. Since the magnitude of the lever arm is a distance, its units are in meters, and torque has units of N m. Torque is a vector quantity and has the same direction as the angular acceleration that it produces. A man pushes a merry-go-round at its edge and perpendicular to the lever arm to achieve maximum torque. 

Applying a stronger torque will produce a greater angular acceleration. For example, the harder the man pushes the merry-go-round in [link] , the faster it accelerates. Furthermore, the more massive the merry-go-round is, the slower it accelerates for the same torque. If the man wants to maximize the effect of his force on the merry-go-round, he should push as far from the center as possible to get the largest lever arm and, therefore, the greatest torque and angular acceleration. Torque is also maximized when the force is applied perpendicular to the lever arm. 

[BL] [OL] [AL] Demonstrate the physical relationships between torque, force, angle of application of force, and length of lever arm by using levers of different lengths. Help students make the connections between the physical observations and mathematical relationships. For instance, torque is maximum when the force is applied exactly perpendicular to the lever arm because sin = 1 sin = 1 for = 90 = 90 degrees. Solving Rotational Kinematics and Torque Problems 

Just as linear forces can balance to produce zero net force and no linear acceleration, the same is true of rotational motion. When two torques of equal magnitude act in opposing directions, there is no net torque and no angular acceleration, as you can see in the following video. If zero net torque acts on a system spinning at a constant angular velocity, the system will continue to spin at the same angular velocity. Introduction to Torque 

This video defines torque in terms of moment arm (which is the same as lever arm). It also covers a problem with forces acting in opposing directions about a pivot point. (At this stage, you can ignore Sal s references to work and mechanical advantage.) 

[link] 

Now let s look at Examples applying rotational kinematics to a fishing reel and the concept of torque to a merry-go-round. Calculating the Time for a Fishing Reel to Stop Spinning 

A deep-sea fisherman uses a fishing rod with a reel of radius 4.50 cm. A big fish takes the bait and swims away from the boat, pulling the fishing line from his fishing reel. As the fishing line unwinds from the reel, the reel spins at an angular velocity of 220 rad/s. The fisherman applies a brake to the spinning reel, creating an angular acceleration of 300 rad/s 2 . How long does it take the reel to come to a stop? Strategy 

We are asked to find the time t for the reel to come to a stop. The magnitude of the initial angular velocity is 0 = 220 0 = 220 rad/s, and the magnitude of the final angular velocity = 0 = 0 . The signed magnitude of the angular acceleration is = 3 0 0 = 3 0 0 rad/s 2 , where the minus sign indicates that it acts in the direction opposite to the angular velocity. Looking at the rotational kinematic equations, we see all quantities but t are known in the equation = 0 + t = 0 + t , making it the easiest equation to use for this problem. Solution 

The equation to use is = 0 + t = 0 + t . 

We solve the equation algebraically for t , and then insert the known values: t = 0 = 0 220 rad/s 300 rad/s 2 = 0.733 s t = 0 = 0 220 rad/s 300 rad/s 2 = 0.733 s Discussion 

The time to stop the reel is fairly small because the acceleration is fairly large. Fishing lines sometimes snap because of the forces involved, and fishermen often let the fish swim for a while before applying brakes on the reel. A tired fish will be slower, requiring a smaller acceleration and therefore a smaller force. Calculating the Torque on a Merry-Go-Round 

Consider the man pushing the playground merry-go-round in this figure . He exerts a force of 250 N at the edge of the merry-go-round and perpendicular to the radius, which is 1.50 m. How much torque does he produce? Assume that friction acting on the merry-go-round is negligible. Strategy 

To find the torque, note that the applied force is perpendicular to the radius and that friction is negligible. Solution = r F sin = ( 1.50 m ) ( 250 N ) sin ( 2 ) . = 375 N m = r F sin = ( 1.50 m ) ( 250 N ) sin ( 2 ) . = 375 N m Discussion 

The man maximizes the torque by applying force perpendicular to the lever arm, so that = 2 = 2 and sin = 1 sin = 1 . The man also maximizes his torque by pushing at the outer edge of the merry-go-round, so that he gets the largest-possible lever arm. Practice Problems 

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[link] Check Your Understanding 

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Use the Check Your Understanding questions to assess whether students master the learning objectives of this section. If students are struggling with a specific objective, these questions will help identify which objective is causing the problem and direct students to the relevant content. Section Summary Kinematics is the description of motion. The kinematics of rotational motion describes the relationships between rotation angle, angular velocity, angular acceleration, and time. Torque is the effectiveness of a force to change the rotational speed of an object. Torque is the rotational analog of force. The lever arm is the distance between the point of rotation (pivot point) and the location where force is applied. Torque is maximized by applying force perpendicular to the lever arm and at a point as far as possible from the pivot point or fulcrum. If torque is zero, angular acceleration is zero. Key Equations Angular acceleration = t = t Rotational kinematic equations = t = t , = 0 + t = 0 + t , = 0 t + 1 2 t 2 = 0 t + 1 2 t 2 , 2 = 0 2 + 2 2 = 0 2 + 2 Tangential (linear) acceleration a = r a = r Torque = r F sin = r F sin Concept Items 

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[link] Performance Task 

Design a lever arm capable of lifting a 0.5 kg object such as a stone. The force for lifting should be provided by placing coins on the other end of the lever. How many coins would you need? What happens if you shorten or lengthen the lever arm? What does this say about torque? Test Prep Multiple Choice 

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[link] Glossary angular acceleration the rate of change of angular velocity with time kinematics of rotational motion the relationships between rotation angle, angular velocity, angular acceleration, and time lever arm the distance between the point of rotation (pivot point) and the location where force is applied tangential acceleration the acceleration in a direction tangent to the circular path of motion and in the same direction or opposite direction as the tangential velocity torque the effectiveness of a force to change the rotational speed of an object{\rtf1\ansi\ansicpg1252\cocoartf1265\cocoasubrtf210
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\f0\fs24 \cf0 The Project Gutenberg EBook of The Adventures of Sherlock Holmes\
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Title: The Adventures of Sherlock Holmes\
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*** START OF THE PROJECT GUTENBERG EBOOK, THE ADVENTURES OF SHERLOCK HOLMES ***\
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(Additional editing by Jose Menendez)\
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THE ADVENTURES OF\
SHERLOCK HOLMES\
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BY\
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SIR ARTHUR CONAN DOYLE\
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CONTENTS\
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I.	A Scandal in Bohemia\
II.	The Red-Headed League\
III.	A Case of Identity\
IV.	The Boscombe Valley Mystery\
V.	The Five Orange Pips\
VI.	The Man with the Twisted Lip\
VII.	The Adventure of the Blue Carbuncle\
VIII.	The Adventure of the Speckled Band\
IX.	The Adventure of the Engineer's Thumb\
X.	The Adventure of the Noble Bachelor\
XI.	The Adventure of the Beryl Coronet\
XII.	The Adventure of the Copper Beeches\
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ADVENTURE  I.  A SCANDAL IN BOHEMIA\
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I.\
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To Sherlock Holmes she is always the woman. I have seldom heard him mention her under any other name. In his eyes she eclipses and predominates the whole of her sex. It was not that he felt any emotion akin to love for Irene Adler. All emotions, and that one particularly, were abhorrent to his cold, precise but admirably balanced mind. He was, I take it, the most perfect reasoning and observing machine that the world has seen, but as a lover he would have placed himself in a false position. He never spoke of the softer passions, save with a gibe and a sneer. They were admirable things for the observer--excellent for drawing the veil from men's motives and actions. But for the trained reasoner to admit such intrusions into his own delicate and finely adjusted temperament was to introduce a distracting factor which might throw a doubt upon all his mental results. Grit in a sensitive instrument, or a crack in one of his own high-power lenses, would not be more disturbing than a strong emotion in a nature such as his. And yet there was but one woman to him, and that woman was the late Irene Adler, of dubious and questionable memory.\
\
I had seen little of Holmes lately. My marriage had drifted us away from each other. My own complete happiness, and the home-centred interests which rise up around the man who first finds himself master of his own establishment, were sufficient to absorb all my attention, while Holmes, who loathed every form of society with his whole Bohemian soul, remained in our lodgings in Baker Street, buried among his old books, and alternating from week to week between cocaine and ambition, the drowsiness of the drug, and the fierce energy of his own keen nature. He was still, as ever, deeply attracted by the study of crime, and occupied his immense faculties and extraordinary powers of observation in following out those clues, and clearing up those mysteries which had been abandoned as hopeless by the official police. From time to time I heard some vague account of his doings: of his summons to Odessa in the case of the Trepoff murder, of his clearing up of the singular tragedy of the Atkinson brothers at Trincomalee, and finally of the mission which he had accomplished so delicately and successfully for the reigning family of Holland. Beyond these signs of his activity, however, which I merely shared with all the readers of the daily press, I knew little of my former friend and companion.\
\
One night--it was on the twentieth of March, 1888--I was returning from a journey to a patient (for I had now returned to civil practice), when my way led me through Baker Street. As I passed the well-remembered door, which must always be associated in my mind with my wooing, and with the dark incidents of the Study in Scarlet, I was seized with a keen desire to see Holmes again, and to know how he was employing his extraordinary powers. His rooms were brilliantly lit, and, even as I looked up, I saw his tall, spare figure pass twice in a dark silhouette against the blind. He was pacing the room swiftly, eagerly, with his head sunk upon his chest and his hands clasped behind him. To me, who knew his every mood and habit, his attitude and manner told their own story. He was at work again. He had risen out of his drug-created dreams and was hot upon the scent of some new problem. I rang the bell and was shown up to the chamber which had formerly been in part my own.\
\
His manner was not effusive. It seldom was; but he was glad, I think, to see me. With hardly a word spoken, but with a kindly eye, he waved me to an armchair, threw across his case of cigars, and indicated a spirit case and a gasogene in the corner. Then he stood before the fire and looked me over in his singular introspective fashion.\
\
"Wedlock suits you," he remarked. "I think, Watson, that you have put on seven and a half pounds since I saw you."\
\
"Seven!" I answered.\
\
"Indeed, I should have thought a little more. Just a trifle more, I fancy, Watson. And in practice again, I observe. You did not tell me that you intended to go into harness."\
\
"Then, how do you know?"\
\
"I see it, I deduce it. How do I know that you have been getting yourself very wet lately, and that you have a most clumsy and careless servant girl?"\
\
"My dear Holmes," said I, "this is too much. You would certainly have been burned, had you lived a few centuries ago. It is true that I had a country walk on Thursday and came home in a dreadful mess, but as I have changed my clothes I can't imagine how you deduce it. As to Mary Jane, she is incorrigible, and my wife has given her notice, but there, again, I fail to see how you work it out."\
\
He chuckled to himself and rubbed his long, nervous hands together.\
\
"It is simplicity itself," said he; "my eyes tell me that on the inside of your left shoe, just where the firelight strikes it, the leather is scored by six almost parallel cuts. Obviously they have been caused by someone who has very carelessly scraped round the edges of the sole in order to remove crusted mud from it. Hence, you see, my double deduction that you had been out in vile weather, and that you had a particularly malignant boot-slitting specimen of the London slavey. As to your practice, if a gentleman walks into my rooms smelling of iodoform, with a black mark of nitrate of silver upon his right forefinger, and a bulge on the right side of his top-hat to show where he has secreted his stethoscope, I must be dull, indeed, if I do not pronounce him to be an active member of the medical profession."\
\
I could not help laughing at the ease with which he explained his process of deduction. "When I hear you give your reasons," I remarked, "the thing always appears to me to be so ridiculously simple that I could easily do it myself, though at each successive instance of your reasoning I am baffled until you explain your process. And yet I believe that my eyes are as good as yours."\
\
"Quite so," he answered, lighting a cigarette, and throwing himself down into an armchair. "You see, but you do not observe. The distinction is clear. For example, you have frequently seen the steps which lead up from the hall to this room."\
\
"Frequently."\
\
"How often?"\
\
"Well, some hundreds of times."\
\
"Then how many are there?"\
\
"How many? I don't know."\
\
"Quite so! You have not observed. And yet you have seen. That is just my point. Now, I know that there are seventeen steps, because I have both seen and observed. By the way, since you are interested in these little problems, and since you are good enough to chronicle one or two of my trifling experiences, you may be interested in this." He threw over a sheet of thick, pink-tinted notepaper which had been lying open upon the table. "It came by the last post," said he. "Read it aloud."\
\
The note was undated, and without either signature or address.\
\
"There will call upon you to-night, at a quarter to eight o'clock," it said, "a gentleman who desires to consult you upon a matter of the very deepest moment. Your recent services to one of the royal houses of Europe have shown that you are one who may safely be trusted with matters which are of an importance which can hardly be exaggerated. This account of you we have from all quarters received. Be in your chamber then at that hour, and do not take it amiss if your visitor wear a mask."\
\
"This is indeed a mystery," I remarked. "What do you imagine that it means?"\
\
"I have no data yet. It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. But the note itself. What do you deduce from it?"\
\
I carefully examined the writing, and the paper upon which it was written.\
\
"The man who wrote it was presumably well to do," I remarked, endeavouring to imitate my companion's processes. "Such paper could not be bought under half a crown a packet. It is peculiarly strong and stiff."\
\
"Peculiar--that is the very word," said Holmes. "It is not an English paper at all. Hold it up to the light."\
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I did so, and saw a large "E" with a small "g," a "P," and a large "G" with a small "t" woven into the texture of the paper.\
\
"What do you make of that?" asked Holmes.\
\
"The name of the maker, no doubt; or his monogram, rather."\
\
"Not at all. The 'G' with the small 't' stands for 'Gesellschaft,' which is the German for 'Company.' It is a customary contraction like our 'Co.' 'P,' of course, stands for 'Papier.' Now for the 'Eg.' Let us glance at our Continental Gazetteer." He took down a heavy brown volume from his shelves. "Eglow, Eglonitz--here we are, Egria. It is in a German-speaking country--in Bohemia, not far from Carlsbad. 'Remarkable as being the scene of the death of Wallenstein, and for its numerous glass-factories and paper-mills.' Ha, ha, my boy, what do you make of that?" His eyes sparkled, and he sent up a great blue triumphant cloud from his cigarette.\
\
"The paper was made in Bohemia," I said.\
\
"Precisely. And the man who wrote the note is a German. Do you note the peculiar construction of the sentence--'This account of you we have from all quarters received.' A Frenchman or Russian could not have written that. It is the German who is so uncourteous to his verbs. It only remains, therefore, to discover what is wanted by this German who writes upon Bohemian paper and prefers wearing a mask to showing his face. And here he comes, if I am not mistaken, to resolve all our doubts."\
\
As he spoke there was the sharp sound of horses' hoofs and grating wheels against the curb, followed by a sharp pull at the bell. Holmes whistled.\
\
"A pair, by the sound," said he. "Yes," he continued, glancing out of the window. "A nice little brougham and a pair of beauties. A hundred and fifty guineas apiece. There's money in this case, Watson, if there is nothing else."\
\
"I think that I had better go, Holmes."\
\
"Not a bit, Doctor. Stay where you are. I am lost without my Boswell. And this promises to be interesting. It would be a pity to miss it."\
\
"But your client--"\
\
"Never mind him. I may want your help, and so may he. Here he comes. Sit down in that armchair, Doctor, and give us your best attention."\
\
A slow and heavy step, which had been heard upon the stairs and in the passage, paused immediately outside the door. Then there was a loud and authoritative tap.\
\
"Come in!" said Holmes.\
\
A man entered who could hardly have been less than six feet six inches in height, with the chest and limbs of a Hercules. His dress was rich with a richness which would, in England, be looked upon as akin to bad taste. Heavy bands of astrakhan were slashed across the sleeves and fronts of his double-breasted coat, while the deep blue cloak which was thrown over his shoulders was lined with flame-coloured silk and secured at the neck with a brooch which consisted of a single flaming beryl. Boots which extended halfway up his calves, and which were trimmed at the tops with rich brown fur, completed the impression of barbaric opulence which was suggested by his whole appearance. He carried a broad-brimmed hat in his hand, while he wore across the upper part of his face, extending down past the cheekbones, a black vizard mask, which he had apparently adjusted that very moment, for his hand was still raised to it as he entered. From the lower part of the face he appeared to be a man of strong character, with a thick, hanging lip, and a long, straight chin suggestive of resolution pushed to the length of obstinacy.\
\
"You had my note?" he asked with a deep harsh voice and a strongly marked German accent. "I told you that I would call." He looked from one to the other of us, as if uncertain which to address.\
\
"Pray take a seat," said Holmes. "This is my friend and colleague, Dr. Watson, who is occasionally good enough to help me in my cases. Whom have I the honour to address?"\
\
"You may address me as the Count Von Kramm, a Bohemian nobleman. I understand that this gentleman, your friend, is a man of honour and discretion, whom I may trust with a matter of the most extreme importance. If not, I should much prefer to communicate with you alone."\
\
I rose to go, but Holmes caught me by the wrist and pushed me back into my chair. "It is both, or none," said he. "You may say before this gentleman anything which you may say to me."\
\
The Count shrugged his broad shoulders. "Then I must begin," said he, "by binding you both to absolute secrecy for two years; at the end of that time the matter will be of no importance. At present it is not too much to say that it is of such weight it may have an influence upon European history."\
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"I promise," said Holmes.\
\
"And I."\
\
"You will excuse this mask," continued our strange visitor. "The august person who employs me wishes his agent to be unknown to you, and I may confess at once that the title by which I have just called myself is not exactly my own."\
\
"I was aware of it," said Holmes dryly.\
\
"The circumstances are of great delicacy, and every precaution has to be taken to quench what might grow to be an immense scandal and seriously compromise one of the reigning families of Europe. To speak plainly, the matter implicates the great House of Ormstein, hereditary kings of Bohemia."\
\
"I was also aware of that," murmured Holmes, settling himself down in his armchair and closing his eyes.\
\
Our visitor glanced with some apparent surprise at the languid, lounging figure of the man who had been no doubt depicted to him as the most incisive reasoner and most energetic agent in Europe. Holmes slowly reopened his eyes and looked impatiently at his gigantic client.\
\
"If your Majesty would condescend to state your case," he remarked, "I should be better able to advise you."\
\
The man sprang from his chair and paced up and down the room in uncontrollable agitation. Then, with a gesture of desperation, he tore the mask from his face and hurled it upon the ground. "You are right," he cried; "I am the King. Why should I attempt to conceal it?"\
\
"Why, indeed?" murmured Holmes. "Your Majesty had not spoken before I was aware that I was addressing Wilhelm Gottsreich Sigismond von Ormstein, Grand Duke of Cassel-Felstein, and hereditary King of Bohemia."\
\
"But you can understand," said our strange visitor, sitting down once more and passing his hand over his high white forehead, "you can understand that I am not accustomed to doing such business in my own person. Yet the matter was so delicate that I could not confide it to an agent without putting myself in his power. I have come incognito from Prague for the purpose of consulting you."\
\
"Then, pray consult," said Holmes, shutting his eyes once more.\
\
"The facts are briefly these: Some five years ago, during a lengthy visit to Warsaw, I made the acquaintance of the well-known adventuress, Irene Adler. The name is no doubt familiar to you."\
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"Kindly look her up in my index, Doctor," murmured Holmes without opening his eyes. For many years he had adopted a system of docketing all paragraphs concerning men and things, so that it was difficult to name a subject or a person on which he could not at once furnish information. In this case I found her biography sandwiched in between that of a Hebrew rabbi and that of a staff-commander who had written a monograph upon the deep-sea fishes.\
\
"Let me see!" said Holmes. "Hum! Born in New Jersey in the year 1858. Contralto--hum! La Scala, hum! Prima donna Imperial Opera of Warsaw--yes! Retired from operatic stage--ha! Living in London--quite so! Your Majesty, as I understand, became entangled with this young person, wrote her some compromising letters, and is now desirous of getting those letters back."\
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"Precisely so. But how--"\
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"Was there a secret marriage?"\
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"None."\
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"No legal papers or certificates?"\
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"None."\
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"Then I fail to follow your Majesty. If this young person should produce her letters for blackmailing or other purposes, how is she to prove their authenticity?"\
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"There is the writing."\
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"Pooh, pooh! Forgery."\
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"My private note-paper."\
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"Stolen."\
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"My own seal."\
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"Imitated."\
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"My photograph."\
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"Bought."\
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"We were both in the photograph."\
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"Oh, dear! That is very bad! Your Majesty has indeed committed an indiscretion."\
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"I was mad--insane."\
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"You have compromised yourself seriously."\
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"I was only Crown Prince then. I was young. I am but thirty now."\
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"It must be recovered."\
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"We have tried and failed."\
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"Your Majesty must pay. It must be bought."\
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"She will not sell."\
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"Stolen, then."\
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"Five attempts have been made. Twice burglars in my pay ransacked her house. Once we diverted her luggage when she travelled. Twice she has been waylaid. There has been no result."\
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"No sign of it?"\
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"Absolutely none."\
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Holmes laughed. "It is quite a pretty little problem," said he.\
\
"But a very serious one to me," returned the King reproachfully.\
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"Very, indeed. And what does she propose to do with the photograph?"\
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"To ruin me."\
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"But how?"\
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"I am about to be married."\
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"So I have heard."\
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"To Clotilde Lothman von Saxe-Meningen, second daughter of the King of Scandinavia. You may know the strict principles of her family. She is herself the very soul of delicacy. A shadow of a doubt as to my conduct would bring the matter to an end."\
\
"And Irene Adler?"\
\
"Threatens to send them the photograph. And she will do it. I know that she will do it. You do not know her, but she has a soul of steel. She has the face of the most beautiful of women, and the mind of the most resolute of men. Rather than I should marry another woman, there are no lengths to which she would not go--none."\
\
"You are sure that she has not sent it yet?"\
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"I am sure."\
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"And why?"\
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"Because she has said that she would send it on the day when the betrothal was publicly proclaimed. That will be next Monday."\
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"Oh, then we have three days yet," said Holmes with a yawn. "That is very fortunate, as I have one or two matters of importance to look into just at present. Your Majesty will, of course, stay in London for the present?"\
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"Certainly. You will find me at the Langham under the name of the Count Von Kramm."\
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"Then I shall drop you a line to let you know how we progress."\
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"Pray do so. I shall be all anxiety."\
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"Then, as to money?"\
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"You have carte blanche."\
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"Absolutely?"\
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"I tell you that I would give one of the provinces of my kingdom to have that photograph."\
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"And for present expenses?"\
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The King took a heavy chamois leather bag from under his cloak and laid it on the table.\
\
"There are three hundred pounds in gold and seven hundred in notes," he said.\
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Holmes scribbled a receipt upon a sheet of his note-book and handed it to him.\
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"And Mademoiselle's address?" he asked.\
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"Is Briony Lodge, Serpentine Avenue, St. John's Wood."\
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Holmes took a note of it. "One other question," said he. "Was the photograph a cabinet?"\
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"It was."\
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"Then, good-night, your Majesty, and I trust that we shall soon have some good news for you. And good-night, Watson," he added, as the wheels of the royal brougham rolled down the street. "If you will be good enough to call to-morrow afternoon at three o'clock I should like to chat this little matter over with you."\
\
II.\
\
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At three o'clock precisely I was at Baker Street, but Holmes had not yet returned. The landlady informed me that he had left the house shortly after eight o'clock in the morning. I sat down beside the fire, however, with the intention of awaiting him, however long he might be. I was already deeply interested in his inquiry, for, though it was surrounded by none of the grim and strange features which were associated with the two crimes which I have already recorded, still, the nature of the case and the exalted station of his client gave it a character of its own. Indeed, apart from the nature of the investigation which my friend had on hand, there was something in his masterly grasp of a situation, and his keen, incisive reasoning, which made it a pleasure to me to study his system of work, and to follow the quick, subtle methods by which he disentangled the most inextricable mysteries. So accustomed was I to his invariable success that the very possibility of his failing had ceased to enter into my head.\
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It was close upon four before the door opened, and a drunken-looking groom, ill-kempt and side-whiskered, with an inflamed face and disreputable clothes, walked into the room. Accustomed as I was to my friend's amazing powers in the use of disguises, I had to look three times before I was certain that it was indeed he. With a nod he vanished into the bedroom, whence he emerged in five minutes tweed-suited and respectable, as of old. Putting his hands into his pockets, he stretched out his legs in front of the fire and laughed heartily for some minutes.\
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"Well, really!" he cried, and then he choked and laughed again until he was obliged to lie back, limp and helpless, in the chair.\
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"What is it?"\
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"It's quite too funny. I am sure you could never guess how I employed my morning, or what I ended by doing."\
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"I can't imagine. I suppose that you have been watching the habits, and perhaps the house, of Miss Irene Adler."\
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"Quite so; but the sequel was rather unusual. I will tell you, however. I left the house a little after eight o'clock this morning in the character of a groom out of work. There is a wonderful sympathy and freemasonry among horsey men. Be one of them, and you will know all that there is to know. I soon found Briony Lodge. It is a bijou villa, with a garden at the back, but built out in front right up to the road, two stories. Chubb lock to the door. Large sitting-room on the right side, well furnished, with long windows almost to the floor, and those preposterous English window fasteners which a child could open. Behind there was nothing remarkable, save that the passage window could be reached from the top of the coach-house. I walked round it and examined it closely from every point of view, but without noting anything else of interest.\
\
"I then lounged down the street and found, as I expected, that there was a mews in a lane which runs down by one wall of the garden. I lent the ostlers a hand in rubbing down their horses, and received in exchange twopence, a glass of half-and-half, two fills of shag tobacco, and as much information as I could desire about Miss Adler, to say nothing of half a dozen other people in the neighbourhood in whom I was not in the least interested, but whose biographies I was compelled to listen to."\
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"And what of Irene Adler?" I asked.\
\
"Oh, she has turned all the men's heads down in that part. She is the daintiest thing under a bonnet on this planet. So say the Serpentine-mews, to a man. She lives quietly, sings at concerts, drives out at five every day, and returns at seven sharp for dinner. Seldom goes out at other times, except when she sings. Has only one male visitor, but a good deal of him. He is dark, handsome, and dashing, never calls less than once a day, and often twice. He is a Mr. Godfrey Norton, of the Inner Temple. See the advantages of a cabman as a confidant. They had driven him home a dozen times from Serpentine-mews, and knew all about him. When I had listened to all they had to tell, I began to walk up and down near Briony Lodge once more, and to think over my plan of campaign.\
\
"This Godfrey Norton was evidently an important factor in the matter. He was a lawyer. That sounded ominous. What was the relation between them, and what the object of his repeated visits? Was she his client, his friend, or his mistress? If the former, she had probably transferred the photograph to his keeping. If the latter, it was less likely. On the issue of this question depended whether I should continue my work at Briony Lodge, or turn my attention to the gentleman's chambers in the Temple. It was a delicate point, and it widened the field of my inquiry. I fear that I bore you with these details, but I have to let you see my little difficulties, if you are to understand the situation."\
\
"I am following you closely," I answered.\
\
"I was still balancing the matter in my mind when a hansom cab drove up to Briony Lodge, and a gentleman sprang out. He was a remarkably handsome man, dark, aquiline, and moustached--evidently the man of whom I had heard. He appeared to be in a great hurry, shouted to the cabman to wait, and brushed past the maid who opened the door with the air of a man who was thoroughly at home.\
\
"He was in the house about half an hour, and I could catch glimpses of him in the windows of the sitting-room, pacing up and down, talking excitedly, and waving his arms. Of her I could see nothing. Presently he emerged, looking even more flurried than before. As he stepped up to the cab, he pulled a gold watch from his pocket and looked at it earnestly, 'Drive like the devil,' he shouted, 'first to Gross & Hankey's in Regent Street, and then to the Church of St. Monica in the Edgeware Road. Half a guinea if you do it in twenty minutes!'\
\
"Away they went, and I was just wondering whether I should not do well to follow them when up the lane came a neat little landau, the coachman with his coat only half-buttoned, and his tie under his ear, while all the tags of his harness were sticking out of the buckles. It hadn't pulled up before she shot out of the hall door and into it. I only caught a glimpse of her at the moment, but she was a lovely woman, with a face that a man might die for.\
\
" 'The Church of St. Monica, John,' she cried, 'and half a sovereign if you reach it in twenty minutes.'\
\
"This was quite too good to lose, Watson. I was just balancing whether I should run for it, or whether I should perch behind her landau when a cab came through the street. The driver looked twice at such a shabby fare, but I jumped in before he could object. 'The Church of St. Monica,' said I, 'and half a sovereign if you reach it in twenty minutes.' It was twenty-five minutes to twelve, and of course it was clear enough what was in the wind.\
\
"My cabby drove fast. I don't think I ever drove faster, but the others were there before us. The cab and the landau with their steaming horses were in front of the door when I arrived. I paid the man and hurried into the church. There was not a soul there save the two whom I had followed and a surpliced clergyman, who seemed to be expostulating with them. They were all three standing in a knot in front of the altar. I lounged up the side aisle like any other idler who has dropped into a church. Suddenly, to my surprise, the three at the altar faced round to me, and Godfrey Norton came running as hard as he could towards me.\
\
" 'Thank God,' he cried. 'You'll do. Come! Come!'\
\
" 'What then?' I asked.\
\
" 'Come, man, come, only three minutes, or it won't be legal.'\
\
"I was half-dragged up to the altar, and before I knew where I was I found myself mumbling responses which were whispered in my ear, and vouching for things of which I knew nothing, and generally assisting in the secure tying up of Irene Adler, spinster, to Godfrey Norton, bachelor. It was all done in an instant, and there was the gentleman thanking me on the one side and the lady on the other, while the clergyman beamed on me in front. It was the most preposterous position in which I ever found myself in my life, and it was the thought of it that started me laughing just now. It seems that there had been some informality about their license, that the clergyman absolutely refused to marry them without a witness of some sort, and that my lucky appearance saved the bridegroom from having to sally out into the streets in search of a best man. The bride gave me a sovereign, and I mean to wear it on my watch chain in memory of the occasion."\
\
"This is a very unexpected turn of affairs," said I; "and what then?"\
\
"Well, I found my plans very seriously menaced. It looked as if the pair might take an immediate departure, and so necessitate very prompt and energetic measures on my part. At the church door, however, they separated, he driving back to the Temple, and she to her own house. 'I shall drive out in the park at five as usual,' she said as she left him. I heard no more. They drove away in different directions, and I went off to make my own arrangements."\
\
"Which are?"\
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"Some cold beef and a glass of beer," he answered, ringing the bell. "I have been too busy to think of food, and I am likely to be busier still this evening. By the way, Doctor, I shall want your co-operation."\
\
"I shall be delighted."\
\
"You don't mind breaking the law?"\
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"Not in the least."\
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"Nor running a chance of arrest?"\
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"Not in a good cause."\
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"Oh, the cause is excellent!"\
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"Then I am your man."\
\
"I was sure that I might rely on you."\
\
"But what is it you wish?"\
\
"When Mrs. Turner has brought in the tray I will make it clear to you. Now," he said as he turned hungrily on the simple fare that our landlady had provided, "I must discuss it while I eat, for I have not much time. It is nearly five now. In two hours we must be on the scene of action. Miss Irene, or Madame, rather, returns from her drive at seven. We must be at Briony Lodge to meet her."\
\
"And what then?"\
\
"You must leave that to me. I have already arranged what is to occur. There is only one point on which I must insist. You must not interfere, come what may. You understand?"\
\
"I am to be neutral?"\
\
"To do nothing whatever. There will probably be some small unpleasantness. Do not join in it. It will end in my being conveyed into the house. Four or five minutes afterwards the sitting-room window will open. You are to station yourself close to that open window."\
\
"Yes."\
\
"You are to watch me, for I will be visible to you."\
\
"Yes."\
\
"And when I raise my hand--so--you will throw into the room what I give you to throw, and will, at the same time, raise the cry of fire. You quite follow me?"\
\
"Entirely."\
\
"It is nothing very formidable," he said, taking a long cigar-shaped roll from his pocket. "It is an ordinary plumber's smoke-rocket, fitted with a cap at either end to make it self-lighting. Your task is confined to that. When you raise your cry of fire, it will be taken up by quite a number of people. You may then walk to the end of the street, and I will rejoin you in ten minutes. I hope that I have made myself clear?"\
\
"I am to remain neutral, to get near the window, to watch you, and at the signal to throw in this object, then to raise the cry of fire, and to wait you at the corner of the street."\
\
"Precisely."\
\
"Then you may entirely rely on me."\
\
"That is excellent. I think, perhaps, it is almost time that I prepare for the new role I have to play."\
\
He disappeared into his bedroom and returned in a few minutes in the character of an amiable and simple-minded Nonconformist clergyman. His broad black hat, his baggy trousers, his white tie, his sympathetic smile, and general look of peering and benevolent curiosity were such as Mr. John Hare alone could have equalled. It was not merely that Holmes changed his costume. His expression, his manner, his very soul seemed to vary with every fresh part that he assumed. The stage lost a fine actor, even as science lost an acute reasoner, when he became a specialist in crime.\
\
It was a quarter past six when we left Baker Street, and it still wanted ten minutes to the hour when we found ourselves in Serpentine Avenue. It was already dusk, and the lamps were just being lighted as we paced up and down in front of Briony Lodge, waiting for the coming of its occupant. The house was just such as I had pictured it from Sherlock Holmes' succinct description, but the locality appeared to be less private than I expected. On the contrary, for a small street in a quiet neighbourhood, it was remarkably animated. There was a group of shabbily dressed men smoking and laughing in a corner, a scissors-grinder with his wheel, two guardsmen who were flirting with a nurse-girl, and several well-dressed young men who were lounging up and down with cigars in their mouths.\
\
"You see," remarked Holmes, as we paced to and fro in front of the house, "this marriage rather simplifies matters. The photograph becomes a double-edged weapon now. The chances are that she would be as averse to its being seen by Mr. Godfrey Norton, as our client is to its coming to the eyes of his princess. Now the question is, Where are we to find the photograph?"\
\
"Where, indeed?"\
\
"It is most unlikely that she carries it about with her. It is cabinet size. Too large for easy concealment about a woman's dress. She knows that the King is capable of having her waylaid and searched. Two attempts of the sort have already been made. We may take it, then, that she does not carry it about with her."\
\
"Where, then?"\
\
"Her banker or her lawyer. There is that double possibility. But I am inclined to think neither. Women are naturally secretive, and they like to do their own secreting. Why should she hand it over to anyone else? She could trust her own guardianship, but she could not tell what indirect or political influence might be brought to bear upon a business man. Besides, remember that she had resolved to use it within a few days. It must be where she can lay her hands upon it. It must be in her own house."\
\
"But it has twice been burgled."\
\
"Pshaw! They did not know how to look."\
\
"But how will you look?"\
\
"I will not look."\
\
"What then?"\
\
"I will get her to show me."\
\
"But she will refuse."\
\
"She will not be able to. But I hear the rumble of wheels. It is her carriage. Now carry out my orders to the letter."\
\
As he spoke the gleam of the sidelights of a carriage came round the curve of the avenue. It was a smart little landau which rattled up to the door of Briony Lodge. As it pulled up, one of the loafing men at the corner dashed forward to open the door in the hope of earning a copper, but was elbowed away by another loafer, who had rushed up with the same intention. A fierce quarrel broke out, which was increased by the two guardsmen, who took sides with one of the loungers, and by the scissors-grinder, who was equally hot upon the other side. A blow was struck, and in an instant the lady, who had stepped from her carriage, was the centre of a little knot of flushed and struggling men, who struck savagely at each other with their fists and sticks. Holmes dashed into the crowd to protect the lady; but, just as he reached her, he gave a cry and dropped to the ground, with the blood running freely down his face. At his fall the guardsmen took to their heels in one direction and the loungers in the other, while a number of better dressed people, who had watched the scuffle without taking part in it, crowded in to help the lady and to attend to the injured man. Irene Adler, as I will still call her, had hurried up the steps; but she stood at the top with her superb figure outlined against the lights of the hall, looking back into the street.\
\
"Is the poor gentleman much hurt?" she asked.\
\
"He is dead," cried several voices.\
\
"No, no, there's life in him!" shouted another. "But he'll be gone before you can get him to hospital."\
\
"He's a brave fellow," said a woman. "They would have had the lady's purse and watch if it hadn't been for him. They were a gang, and a rough one, too. Ah, he's breathing now."\
\
"He can't lie in the street. May we bring him in, marm?"\
\
"Surely. Bring him into the sitting-room. There is a comfortable sofa. This way, please!"\
\
Slowly and solemnly he was borne into Briony Lodge and laid out in the principal room, while I still observed the proceedings from my post by the window. The lamps had been lit, but the blinds had not been drawn, so that I could see Holmes as he lay upon the couch. I do not know whether he was seized with compunction at that moment for the part he was playing, but I know that I never felt more heartily ashamed of myself in my life than when I saw the beautiful creature against whom I was conspiring, or the grace and kindliness with which she waited upon the injured man. And yet it would be the blackest treachery to Holmes to draw back now from the part which he had intrusted to me. I hardened my heart, and took the smoke-rocket from under my ulster. After all, I thought, we are not injuring her. We are but preventing her from injuring another.\
\
Holmes had sat up upon the couch, and I saw him motion like a man who is in need of air. A maid rushed across and threw open the window. At the same instant I saw him raise his hand and at the signal I tossed my rocket into the room with a cry of "Fire!" The word was no sooner out of my mouth than the whole crowd of spectators, well dressed and ill--gentlemen, ostlers, and servant maids--joined in a general shriek of "Fire!" Thick clouds of smoke curled through the room and out at the open window. I caught a glimpse of rushing figures, and a moment later the voice of Holmes from within assuring them that it was a false alarm. Slipping through the shouting crowd I made my way to the corner of the street, and in ten minutes was rejoiced to find my friend's arm in mine, and to get away from the scene of uproar. He walked swiftly and in silence for some few minutes until we had turned down one of the quiet streets which lead towards the Edgeware Road.\
\
"You did it very nicely, Doctor," he remarked. "Nothing could have been better. It is all right."\
\
"You have the photograph?"\
\
"I know where it is."\
\
"And how did you find out?"\
\
"She showed me, as I told you she would."\
\
"I am still in the dark."\
\
"I do not wish to make a mystery," said he, laughing. "The matter was perfectly simple. You, of course, saw that everyone in the street was an accomplice. They were all engaged for the evening."\
\
"I guessed as much."\
\
"Then, when the row broke out, I had a little moist red paint in the palm of my hand. I rushed forward, fell down, clapped my hand to my face, and became a piteous spectacle. It is an old trick."\
\
"That also I could fathom."\
\
"Then they carried me in. She was bound to have me in. What else could she do? And into her sitting-room, which was the very room which I suspected. It lay between that and her bedroom, and I was determined to see which. They laid me on a couch, I motioned for air, they were compelled to open the window, and you had your chance."\
\
"How did that help you?"\
\
"It was all-important. When a woman thinks that her house is on fire, her instinct is at once to rush to the thing which she values most. It is a perfectly overpowering impulse, and I have more than once taken advantage of it. In the case of the Darlington Substitution Scandal it was of use to me, and also in the Arnsworth Castle business. A married woman grabs at her baby; an unmarried one reaches for her jewel-box. Now it was clear to me that our lady of to-day had nothing in the house more precious to her than what we are in quest of. She would rush to secure it. The alarm of fire was admirably done. The smoke and shouting were enough to shake nerves of steel. She responded beautifully. The photograph is in a recess behind a sliding panel just above the right bell-pull. She was there in an instant, and I caught a glimpse of it as she half drew it out. When I cried out that it was a false alarm, she replaced it, glanced at the rocket, rushed from the room, and I have not seen her since. I rose, and, making my excuses, escaped from the house. I hesitated whether to attempt to secure the photograph at once; but the coachman had come in, and as he was watching me narrowly, it seemed safer to wait. A little over-precipitance may ruin all."\
\
"And now?" I asked.\
\
"Our quest is practically finished. I shall call with the King to-morrow, and with you, if you care to come with us. We will be shown into the sitting-room to wait for the lady, but it is probable that when she comes she may find neither us nor the photograph. It might be a satisfaction to his Majesty to regain it with his own hands."\
\
"And when will you call?"\
\
"At eight in the morning. She will not be up, so that we shall have a clear field. Besides, we must be prompt, for this marriage may mean a complete change in her life and habits. I must wire to the King without delay."\
\
We had reached Baker Street and had stopped at the door. He was searching his pockets for the key when someone passing said:\
\
"Good-night, Mister Sherlock Holmes."\
\
There were several people on the pavement at the time, but the greeting appeared to come from a slim youth in an ulster who had hurried by.\
\
"I've heard that voice before," said Holmes, staring down the dimly lit street. "Now, I wonder who the deuce that could have been."\
\
III.\
\
\
I slept at Baker Street that night, and we were engaged upon our toast and coffee in the morning when the King of Bohemia rushed into the room.\
\
"You have really got it!" he cried, grasping Sherlock Holmes by either shoulder and looking eagerly into his face.\
\
"Not yet."\
\
"But you have hopes?"\
\
"I have hopes."\
\
"Then, come. I am all impatience to be gone."\
\
"We must have a cab."\
\
"No, my brougham is waiting."\
\
"Then that will simplify matters." We descended and started off once more for Briony Lodge.\
\
"Irene Adler is married," remarked Holmes.\
\
"Married! When?"\
\
"Yesterday."\
\
"But to whom?"\
\
"To an English lawyer named Norton."\
\
"But she could not love him."\
\
"I am in hopes that she does."\
\
"And why in hopes?"\
\
"Because it would spare your Majesty all fear of future annoyance. If the lady loves her husband, she does not love your Majesty. If she does not love your Majesty, there is no reason why she should interfere with your Majesty's plan."\
\
"It is true. And yet--! Well! I wish she had been of my own station! What a queen she would have made!" He relapsed into a moody silence, which was not broken until we drew up in Serpentine Avenue.\
\
The door of Briony Lodge was open, and an elderly woman stood upon the steps. She watched us with a sardonic eye as we stepped from the brougham.\
\
"Mr. Sherlock Holmes, I believe?" said she.\
\
"I am Mr. Holmes," answered my companion, looking at her with a questioning and rather startled gaze.\
\
"Indeed! My mistress told me that you were likely to call. She left this morning with her husband by the 5:15 train from Charing Cross for the Continent."\
\
"What!" Sherlock Holmes staggered back, white with chagrin and surprise. "Do you mean that she has left England?"\
\
"Never to return."\
\
"And the papers?" asked the King hoarsely. "All is lost."\
\
"We shall see." He pushed past the servant and rushed into the drawing-room, followed by the King and myself. The furniture was scattered about in every direction, with dismantled shelves and open drawers, as if the lady had hurriedly ransacked them before her flight. Holmes rushed at the bell-pull, tore back a small sliding shutter, and, plunging in his hand, pulled out a photograph and a letter. The photograph was of Irene Adler herself in evening dress, the letter was superscribed to "Sherlock Holmes, Esq. To be left till called for." My friend tore it open, and we all three read it together. It was dated at midnight of the preceding night and ran in this way:\
\
"MY DEAR MR. SHERLOCK HOLMES,--You really did it very well. You took me in completely. Until after the alarm of fire, I had not a suspicion. But then, when I found how I had betrayed myself, I began to think. I had been warned against you months ago. I had been told that, if the King employed an agent, it would certainly be you. And your address had been given me. Yet, with all this, you made me reveal what you wanted to know. Even after I became suspicious, I found it hard to think evil of such a dear, kind old clergyman. But, you know, I have been trained as an actress myself. Male costume is nothing new to me. I often take advantage of the freedom which it gives. I sent John, the coachman, to watch you, ran upstairs, got into my walking clothes, as I call them, and came down just as you departed.\
\
"Well, I followed you to your door, and so made sure that I was really an object of interest to the celebrated Mr. Sherlock Holmes. Then I, rather imprudently, wished you good-night, and started for the Temple to see my husband.\
\
"We both thought the best resource was flight, when pursued by so formidable an antagonist; so you will find the nest empty when you call to-morrow. As to the photograph, your client may rest in peace. I love and am loved by a better man than he. The King may do what he will without hindrance from one whom he has cruelly wronged. I keep it only to safeguard myself, and to preserve a weapon which will always secure me from any steps which he might take in the future. I leave a photograph which he might care to possess; and I remain, dear Mr. Sherlock Holmes,\
\
\
"Very truly yours,              \
"IRENE NORTON, nee ADLER."\
\
"What a woman--oh, what a woman!" cried the King of Bohemia, when we had all three read this epistle. "Did I not tell you how quick and resolute she was? Would she not have made an admirable queen? Is it not a pity that she was not on my level?"\
\
"From what I have seen of the lady, she seems, indeed, to be on a very different level to your Majesty," said Holmes coldly. "I am sorry that I have not been able to bring your Majesty's business to a more successful conclusion."\
\
"On the contrary, my dear sir," cried the King; "nothing could be more successful. I know that her word is inviolate. The photograph is now as safe as if it were in the fire."\
\
"I am glad to hear your Majesty say so."\
\
"I am immensely indebted to you. Pray tell me in what way I can reward you. This ring--" He slipped an emerald snake ring from his finger and held it out upon the palm of his hand.\
\
"Your Majesty has something which I should value even more highly," said Holmes.\
\
"You have but to name it."\
\
"This photograph!"\
\
The King stared at him in amazement.\
\
"Irene's photograph!" he cried. "Certainly, if you wish it."\
\
"I thank your Majesty. Then there is no more to be done in the matter. I have the honour to wish you a very good morning." He bowed, and, turning away without observing the hand which the King had stretched out to him, he set off in my company for his chambers.\
\
And that was how a great scandal threatened to affect the kingdom of Bohemia, and how the best plans of Mr. Sherlock Holmes were beaten by a woman's wit. He used to make merry over the cleverness of women, but I have not heard him do it of late. And when he speaks of Irene Adler, or when he refers to her photograph, it is always under the honourable title of the woman.\
\
ADVENTURE  II.  THE RED-HEADED LEAGUE\
\
\
I had called upon my friend, Mr. Sherlock Holmes, one day in the autumn of last year and found him in deep conversation with a very stout, florid-faced, elderly gentleman with fiery red hair. With an apology for my intrusion, I was about to withdraw when Holmes pulled me abruptly into the room and closed the door behind me.\
\
"You could not possibly have come at a better time, my dear Watson," he said cordially.\
\
"I was afraid that you were engaged."\
\
"So I am. Very much so."\
\
"Then I can wait in the next room."\
\
"Not at all. This gentleman, Mr. Wilson, has been my partner and helper in many of my most successful cases, and I have no doubt that he will be of the utmost use to me in yours also."\
\
The stout gentleman half rose from his chair and gave a bob of greeting, with a quick little questioning glance from his small fat-encircled eyes.\
\
"Try the settee," said Holmes, relapsing into his armchair and putting his fingertips together, as was his custom when in judicial moods. "I know, my dear Watson, that you share my love of all that is bizarre and outside the conventions and humdrum routine of everyday life. You have shown your relish for it by the enthusiasm which has prompted you to chronicle, and, if you will excuse my saying so, somewhat to embellish so many of my own little adventures."\
\
"Your cases have indeed been of the greatest interest to me," I observed.\
\
"You will remember that I remarked the other day, just before we went into the very simple problem presented by Miss Mary Sutherland, that for strange effects and extraordinary combinations we must go to life itself, which is always far more daring than any effort of the imagination."\
\
"A proposition which I took the liberty of doubting."\
\
"You did, Doctor, but none the less you must come round to my view, for otherwise I shall keep on piling fact upon fact on you until your reason breaks down under them and acknowledges me to be right. Now, Mr. Jabez Wilson here has been good enough to call upon me this morning, and to begin a narrative which promises to be one of the most singular which I have listened to for some time. You have heard me remark that the strangest and most unique things are very often connected not with the larger but with the smaller crimes, and occasionally, indeed, where there is room for doubt whether any positive crime has been committed. As far as I have heard, it is impossible for me to say whether the present case is an instance of crime or not, but the course of events is certainly among the most singular that I have ever listened to. Perhaps, Mr. Wilson, you would have the great kindness to recommence your narrative. I ask you not merely because my friend Dr. Watson has not heard the opening part but also because the peculiar nature of the story makes me anxious to have every possible detail from your lips. As a rule, when I have heard some slight indication of the course of events, I am able to guide myself by the thousands of other similar cases which occur to my memory. In the present instance I am forced to admit that the facts are, to the best of my belief, unique."\
\
The portly client puffed out his chest with an appearance of some little pride and pulled a dirty and wrinkled newspaper from the inside pocket of his greatcoat. As he glanced down the advertisement column, with his head thrust forward and the paper flattened out upon his knee, I took a good look at the man and endeavoured, after the fashion of my companion, to read the indications which might be presented by his dress or appearance.\
\
I did not gain very much, however, by my inspection. Our visitor bore every mark of being an average commonplace British tradesman, obese, pompous, and slow. He wore rather baggy grey shepherd's check trousers, a not over-clean black frock-coat, unbuttoned in the front, and a drab waistcoat with a heavy brassy Albert chain, and a square pierced bit of metal dangling down as an ornament. A frayed top-hat and a faded brown overcoat with a wrinkled velvet collar lay upon a chair beside him. Altogether, look as I would, there was nothing remarkable about the man save his blazing red head, and the expression of extreme chagrin and discontent upon his features.\
\
Sherlock Holmes' quick eye took in my occupation, and he shook his head with a smile as he noticed my questioning glances. "Beyond the obvious facts that he has at some time done manual labour, that he takes snuff, that he is a Freemason, that he has been in China, and that he has done a considerable amount of writing lately, I can deduce nothing else."\
\
Mr. Jabez Wilson started up in his chair, with his forefinger upon the paper, but his eyes upon my companion.\
\
"How, in the name of good-fortune, did you know all that, Mr. Holmes?" he asked. "How did you know, for example, that I did manual labour. It's as true as gospel, for I began as a ship's carpenter."\
\
"Your hands, my dear sir. Your right hand is quite a size larger than your left. You have worked with it, and the muscles are more developed."\
\
"Well, the snuff, then, and the Freemasonry?"\
\
"I won't insult your intelligence by telling you how I read that, especially as, rather against the strict rules of your order, you use an arc-and-compass breastpin."\
\
"Ah, of course, I forgot that. But the writing?"\
\
"What else can be indicated by that right cuff so very shiny for five inches, and the left one with the smooth patch near the elbow where you rest it upon the desk?"\
\
"Well, but China?"\
\
"The fish that you have tattooed immediately above your right wrist could only have been done in China. I have made a small study of tattoo marks and have even contributed to the literature of the subject. That trick of staining the fishes' scales of a delicate pink is quite peculiar to China. When, in addition, I see a Chinese coin hanging from your watch-chain, the matter becomes even more simple."\
\
Mr. Jabez Wilson laughed heavily. "Well, I never!" said he. "I thought at first that you had done something clever, but I see that there was nothing in it after all."\
\
"I begin to think, Watson," said Holmes, "that I make a mistake in explaining. 'Omne ignotum pro magnifico,' you know, and my poor little reputation, such as it is, will suffer shipwreck if I am so candid. Can you not find the advertisement, Mr. Wilson?"\
\
"Yes, I have got it now," he answered with his thick red finger planted halfway down the column. "Here it is. This is what began it all. You just read it for yourself, sir."\
\
I took the paper from him and read as follows:\
\
"TO THE RED-HEADED LEAGUE: On account of the bequest of the late Ezekiah Hopkins, of Lebanon, Pennsylvania, U. S. A., there is now another vacancy open which entitles a member of the League to a salary of $4 a week for purely nominal services. All red-headed men who are sound in body and mind and above the age of twenty-one years, are eligible. Apply in person on Monday, at eleven o'clock, to Duncan Ross, at the offices of the League, 7 Pope's Court, Fleet Street."\
\
"What on earth does this mean?" I ejaculated after I had twice read over the extraordinary announcement.\
\
Holmes chuckled and wriggled in his chair, as was his habit when in high spirits. "It is a little off the beaten track, isn't it?" said he. "And now, Mr. Wilson, off you go at scratch and tell us all about yourself, your household, and the effect which this advertisement had upon your fortunes. You will first make a note, Doctor, of the paper and the date."\
\
"It is The Morning Chronicle of April 27, 1890. Just two months ago."\
\
"Very good. Now, Mr. Wilson?"\
\
"Well, it is just as I have been telling you, Mr. Sherlock Holmes," said Jabez Wilson, mopping his forehead; "I have a small pawnbroker's business at Coburg Square, near the City. It's not a very large affair, and of late years it has not done more than just give me a living. I used to be able to keep two assistants, but now I only keep one; and I would have a job to pay him but that he is willing to come for half wages so as to learn the business."\
\
"What is the name of this obliging youth?" asked Sherlock Holmes.\
\
"His name is Vincent Spaulding, and he's not such a youth, either. It's hard to say his age. I should not wish a smarter assistant, Mr. Holmes; and I know very well that he could better himself and earn twice what I am able to give him. But, after all, if he is satisfied, why should I put ideas in his head?"\
\
"Why, indeed? You seem most fortunate in having an employe who comes under the full market price. It is not a common experience among employers in this age. I don't know that your assistant is not as remarkable as your advertisement."\
\
"Oh, he has his faults, too," said Mr. Wilson. "Never was such a fellow for photography. Snapping away with a camera when he ought to be improving his mind, and then diving down into the cellar like a rabbit into its hole to develop his pictures. That is his main fault, but on the whole he's a good worker. There's no vice in him."\
\
"He is still with you, I presume?"\
\
"Yes, sir. He and a girl of fourteen, who does a bit of simple cooking and keeps the place clean--that's all I have in the house, for I am a widower and never had any family. We live very quietly, sir, the three of us; and we keep a roof over our heads and pay our debts, if we do nothing more.\
\
"The first thing that put us out was that advertisement. Spaulding, he came down into the office just this day eight weeks, with this very paper in his hand, and he says:\
\
" 'I wish to the Lord, Mr. Wilson, that I was a red-headed man.'\
\
" 'Why that?' I asks.\
\
" 'Why,' says he, 'here's another vacancy on the League of the Red-headed Men. It's worth quite a little fortune to any man who gets it, and I understand that there are more vacancies than there are men, so that the trustees are at their wits' end what to do with the money. If my hair would only change colour, here's a nice little crib all ready for me to step into.'\
\
" 'Why, what is it, then?' I asked. You see, Mr. Holmes, I am a very stay-at-home man, and as my business came to me instead of my having to go to it, I was often weeks on end without putting my foot over the door-mat. In that way I didn't know much of what was going on outside, and I was always glad of a bit of news.\
\
" 'Have you never heard of the League of the Red-headed Men?' he asked with his eyes open.\
\
" 'Never.'\
\
" 'Why, I wonder at that, for you are eligible yourself for one of the vacancies.'\
\
" 'And what are they worth?' I asked.\
\
" 'Oh, merely a couple of hundred a year, but the work is slight, and it need not interfere very much with one's other occupations.'\
\
"Well, you can easily think that that made me prick up my ears, for the business has not been over good for some years, and an extra couple of hundred would have been very handy.\
\
" 'Tell me all about it,' said I.\
\
" 'Well,' said he, showing me the advertisement, 'you can see for yourself that the League has a vacancy, and there is the address where you should apply for particulars. As far as I can make out, the League was founded by an American millionaire, Ezekiah Hopkins, who was very peculiar in his ways. He was himself red-headed, and he had a great sympathy for all red-headed men; so, when he died, it was found that he had left his enormous fortune in the hands of trustees, with instructions to apply the interest to the providing of easy berths to men whose hair is of that colour. From all I hear it is splendid pay and very little to do.'\
\
" 'But,' said I, 'there would be millions of red-headed men who would apply.'\
\
" 'Not so many as you might think,' he answered. 'You see it is really confined to Londoners, and to grown men. This American had started from London when he was young, and he wanted to do the old town a good turn. Then, again, I have heard it is no use your applying if your hair is light red, or dark red, or anything but real bright, blazing, fiery red. Now, if you cared to apply, Mr. Wilson, you would just walk in; but perhaps it would hardly be worth your while to put yourself out of the way for the sake of a few hundred pounds.'\
\
"Now, it is a fact, gentlemen, as you may see for yourselves, that my hair is of a very full and rich tint, so that it seemed to me that if there was to be any competition in the matter I stood as good a chance as any man that I had ever met. Vincent Spaulding seemed to know so much about it that I thought he might prove useful, so I just ordered him to put up the shutters for the day and to come right away with me. He was very willing to have a holiday, so we shut the business up and started off for the address that was given us in the advertisement.\
\
"I never hope to see such a sight as that again, Mr. Holmes. From north, south, east, and west every man who had a shade of red in his hair had tramped into the city to answer the advertisement. Fleet Street was choked with red-headed folk, and Pope's Court looked like a coster's orange barrow. I should not have thought there were so many in the whole country as were brought together by that single advertisement. Every shade of colour they were--straw, lemon, orange, brick, Irish-setter, liver, clay; but, as Spaulding said, there were not many who had the real vivid flame-coloured tint. When I saw how many were waiting, I would have given it up in despair; but Spaulding would not hear of it. How he did it I could not imagine, but he pushed and pulled and butted until he got me through the crowd, and right up to the steps which led to the office. There was a double stream upon the stair, some going up in hope, and some coming back dejected; but we wedged in as well as we could and soon found ourselves in the office."\
\
"Your experience has been a most entertaining one," remarked Holmes as his client paused and refreshed his memory with a huge pinch of snuff. "Pray continue your very interesting statement."\
\
"There was nothing in the office but a couple of wooden chairs and a deal table, behind which sat a small man with a head that was even redder than mine. He said a few words to each candidate as he came up, and then he always managed to find some fault in them which would disqualify them. Getting a vacancy did not seem to be such a very easy matter, after all. However, when our turn came the little man was much more favourable to me than to any of the others, and he closed the door as we entered, so that he might have a private word with us.\
\
" 'This is Mr. Jabez Wilson,' said my assistant, 'and he is willing to fill a vacancy in the League.'\
\
" 'And he is admirably suited for it,' the other answered. 'He has every requirement. I cannot recall when I have seen anything so fine.' He took a step backward, cocked his head on one side, and gazed at my hair until I felt quite bashful. Then suddenly he plunged forward, wrung my hand, and congratulated me warmly on my success.\
\
" 'It would be injustice to hesitate,' said he. 'You will, however, I am sure, excuse me for taking an obvious precaution.' With that he seized my hair in both his hands, and tugged until I yelled with the pain. 'There is water in your eyes,' said he as he released me. 'I perceive that all is as it should be. But we have to be careful, for we have twice been deceived by wigs and once by paint. I could tell you tales of cobbler's wax which would disgust you with human nature.' He stepped over to the window and shouted through it at the top of his voice that the vacancy was filled. A groan of disappointment came up from below, and the folk all trooped away in different directions until there was not a red-head to be seen except my own and that of the manager.\
\
" 'My name,' said he, 'is Mr. Duncan Ross, and I am myself one of the pensioners upon the fund left by our noble benefactor. Are you a married man, Mr. Wilson? Have you a family?'\
\
"I answered that I had not.\
\
"His face fell immediately.\
\
" 'Dear me!' he said gravely, 'that is very serious indeed! I am sorry to hear you say that. The fund was, of course, for the propagation and spread of the red-heads as well as for their maintenance. It is exceedingly unfortunate that you should be a bachelor.'\
\
"My face lengthened at this, Mr. Holmes, for I thought that I was not to have the vacancy after all; but after thinking it over for a few minutes he said that it would be all right.\
\
" 'In the case of another,' said he, 'the objection might be fatal, but we must stretch a point in favour of a man with such a head of hair as yours. When shall you be able to enter upon your new duties?'\
\
" 'Well, it is a little awkward, for I have a business already,' said I.\
\
" 'Oh, never mind about that, Mr. Wilson!' said Vincent Spaulding. 'I should be able to look after that for you.'\
\
" 'What would be the hours?' I asked.\
\
" 'Ten to two.'\
\
"Now a pawnbroker's business is mostly done of an evening, Mr. Holmes, especially Thursday and Friday evening, which is just before pay-day; so it would suit me very well to earn a little in the mornings. Besides, I knew that my assistant was a good man, and that he would see to anything that turned up.\
\
" 'That would suit me very well,' said I. 'And the pay?'\
\
" 'Is $4 a week.'\
\
" 'And the work?'\
\
" 'Is purely nominal.'\
\
" 'What do you call purely nominal?'\
\
" 'Well, you have to be in the office, or at least in the building, the whole time. If you leave, you forfeit your whole position forever. The will is very clear upon that point. You don't comply with the conditions if you budge from the office during that time.'\
\
" 'It's only four hours a day, and I should not think of leaving,' said I.\
\
" 'No excuse will avail,' said Mr. Duncan Ross; 'neither sickness nor business nor anything else. There you must stay, or you lose your billet.'\
\
" 'And the work?'\
\
" 'Is to copy out the Encyclopaedia Britannica. There is the first volume of it in that press. You must find your own ink, pens, and blotting-paper, but we provide this table and chair. Will you be ready to-morrow?'\
\
" 'Certainly,' I answered.\
\
" 'Then, good-bye, Mr. Jabez Wilson, and let me congratulate you once more on the important position which you have been fortunate enough to gain.' He bowed me out of the room and I went home with my assistant, hardly knowing what to say or do, I was so pleased at my own good fortune.\
\
"Well, I thought over the matter all day, and by evening I was in low spirits again; for I had quite persuaded myself that the whole affair must be some great hoax or fraud, though what its object might be I could not imagine. It seemed altogether past belief that anyone could make such a will, or that they would pay such a sum for doing anything so simple as copying out the Encyclopaedia Britannica. Vincent Spaulding did what he could to cheer me up, but by bedtime I had reasoned myself out of the whole thing. However, in the morning I determined to have a look at it anyhow, so I bought a penny bottle of ink, and with a quill-pen, and seven sheets of foolscap paper, I started off for Pope's Court.\
\
"Well, to my surprise and delight, everything was as right as possible. The table was set out ready for me, and Mr. Duncan Ross was there to see that I got fairly to work. He started me off upon the letter A, and then he left me; but he would drop in from time to time to see that all was right with me. At two o'clock he bade me good-day, complimented me upon the amount that I had written, and locked the door of the office after me.\
\
"This went on day after day, Mr. Holmes, and on Saturday the manager came in and planked down four golden sovereigns for my week's work. It was the same next week, and the same the week after. Every morning I was there at ten, and every afternoon I left at two. By degrees Mr. Duncan Ross took to coming in only once of a morning, and then, after a time, he did not come in at all. Still, of course, I never dared to leave the room for an instant, for I was not sure when he might come, and the billet was such a good one, and suited me so well, that I would not risk the loss of it.\
\
"Eight weeks passed away like this, and I had written about Abbots and Archery and Armour and Architecture and Attica, and hoped with diligence that I might get on to the B's before very long. It cost me something in foolscap, and I had pretty nearly filled a shelf with my writings. And then suddenly the whole business came to an end."\
\
"To an end?"\
\
"Yes, sir. And no later than this morning. I went to my work as usual at ten o'clock, but the door was shut and locked, with a little square of cardboard hammered on to the middle of the panel with a tack. Here it is, and you can read for yourself."\
\
He held up a piece of white cardboard about the size of a sheet of note-paper. It read in this fashion:\
\
\
THE RED-HEADED LEAGUE\
\
IS\
\
DISSOLVED.\
\
October 9, 1890.\
\
\
Sherlock Holmes and I surveyed this curt announcement and the rueful face behind it, until the comical side of the affair so completely overtopped every other consideration that we both burst out into a roar of laughter.\
\
"I cannot see that there is anything very funny," cried our client, flushing up to the roots of his flaming head. "If you can do nothing better than laugh at me, I can go elsewhere."\
\
"No, no," cried Holmes, shoving him back into the chair from which he had half risen. "I really wouldn't miss your case for the world. It is most refreshingly unusual. But there is, if you will excuse my saying so, something just a little funny about it. Pray what steps did you take when you found the card upon the door?"\
\
"I was staggered, sir. I did not know what to do. Then I called at the offices round, but none of them seemed to know anything about it. Finally, I went to the landlord, who is an accountant living on the ground floor, and I asked him if he could tell me what had become of the Red-headed League. He said that he had never heard of any such body. Then I asked him who Mr. Duncan Ross was. He answered that the name was new to him.\
\
" 'Well,' said I, 'the gentleman at No. 4.'\
\
" 'What, the red-headed man?'\
\
" 'Yes.'\
\
" 'Oh,' said he, 'his name was William Morris. He was a solicitor and was using my room as a temporary convenience until his new premises were ready. He moved out yesterday.'\
\
" 'Where could I find him?'\
\
" 'Oh, at his new offices. He did tell me the address. Yes, 17 King Edward Street, near St. Paul's.'\
\
"I started off, Mr. Holmes, but when I got to that address it was a manufactory of artificial knee-caps, and no one in it had ever heard of either Mr. William Morris or Mr. Duncan Ross."\
\
"And what did you do then?" asked Holmes.\
\
"I went home to Saxe-Coburg Square, and I took the advice of my assistant. But he could not help me in any way. He could only say that if I waited I should hear by post. But that was not quite good enough, Mr. Holmes. I did not wish to lose such a place without a struggle, so, as I had heard that you were good enough to give advice to poor folk who were in need of it, I came right away to you."\
\
"And you did very wisely," said Holmes. "Your case is an exceedingly remarkable one, and I shall be happy to look into it. From what you have told me I think that it is possible that graver issues hang from it than might at first sight appear."\
\
"Grave enough!" said Mr. Jabez Wilson. "Why, I have lost four pound a week."\
\
"As far as you are personally concerned," remarked Holmes, "I do not see that you have any grievance against this extraordinary league. On the contrary, you are, as I understand, richer by some $30, to say nothing of the minute knowledge which you have gained on every subject which comes under the letter A. You have lost nothing by them."\
\
"No, sir. But I want to find out about them, and who they are, and what their object was in playing this prank--if it was a prank--upon me. It was a pretty expensive joke for them, for it cost them two and thirty pounds."\
\
"We shall endeavour to clear up these points for you. And, first, one or two questions, Mr. Wilson. This assistant of yours who first called your attention to the advertisement--how long had he been with you?"\
\
"About a month then."\
\
"How did he come?"\
\
"In answer to an advertisement."\
\
"Was he the only applicant?"\
\
"No, I had a dozen."\
\
"Why did you pick him?"\
\
"Because he was handy and would come cheap."\
\
"At half wages, in fact."\
\
"Yes."\
\
"What is he like, this Vincent Spaulding?"\
\
"Small, stout-built, very quick in his ways, no hair on his face, though he's not short of thirty. Has a white splash of acid upon his forehead."\
\
Holmes sat up in his chair in considerable excitement. "I thought as much," said he. "Have you ever observed that his ears are pierced for earrings?"\
\
"Yes, sir. He told me that a gipsy had done it for him when he was a lad."\
\
"Hum!" said Holmes, sinking back in deep thought. "He is still with you?"\
\
"Oh, yes, sir; I have only just left him."\
\
"And has your business been attended to in your absence?"\
\
"Nothing to complain of, sir. There's never very much to do of a morning."\
\
"That will do, Mr. Wilson. I shall be happy to give you an opinion upon the subject in the course of a day or two. To-day is Saturday, and I hope that by Monday we may come to a conclusion."\
\
"Well, Watson," said Holmes when our visitor had left us, "what do you make of it all?"\
\
"I make nothing of it," I answered frankly. "It is a most mysterious business."\
\
"As a rule," said Holmes, "the more bizarre a thing is the less mysterious it proves to be. It is your commonplace, featureless crimes which are really puzzling, just as a commonplace face is the most difficult to identify. But I must be prompt over this matter."\
\
"What are you going to do, then?" I asked.\
\
"To smoke," he answered. "It is quite a three pipe problem, and I beg that you won't speak to me for fifty minutes." He curled himself up in his chair, with his thin knees drawn up to his hawk-like nose, and there he sat with his eyes closed and his black clay pipe thrusting out like the bill of some strange bird. I had come to the conclusion that he had dropped asleep, and indeed was nodding myself, when he suddenly sprang out of his chair with the gesture of a man who has made up his mind and put his pipe down upon the mantelpiece.\
\
"Sarasate plays at the St. James's Hall this afternoon," he remarked. "What do you think, Watson? Could your patients spare you for a few hours?"\
\
"I have nothing to do to-day. My practice is never very absorbing."\
\
"Then put on your hat and come. I am going through the City first, and we can have some lunch on the way. I observe that there is a good deal of German music on the programme, which is rather more to my taste than Italian or French. It is introspective, and I want to introspect. Come along!"\
\
We travelled by the Underground as far as Aldersgate; and a short walk took us to Saxe-Coburg Square, the scene of the singular story which we had listened to in the morning. It was a poky, little, shabby-genteel place, where four lines of dingy two-storied brick houses looked out into a small railed-in enclosure, where a lawn of weedy grass and a few clumps of faded laurel bushes made a hard fight against a smoke-laden and uncongenial atmosphere. Three gilt balls and a brown board with "JABEZ WILSON" in white letters, upon a corner house, announced the place where our red-headed client carried on his business. Sherlock Holmes stopped in front of it with his head on one side and looked it all over, with his eyes shining brightly between puckered lids. Then he walked slowly up the street, and then down again to the corner, still looking keenly at the houses. Finally he returned to the pawnbroker's, and, having thumped vigorously upon the pavement with his stick two or three times, he went up to the door and knocked. It was instantly opened by a bright-looking, clean-shaven young fellow, who asked him to step in.\
\
"Thank you," said Holmes, "I only wished to ask you how you would go from here to the Strand."\
\
"Third right, fourth left," answered the assistant promptly, closing the door.\
\
"Smart fellow, that," observed Holmes as we walked away. "He is, in my judgment, the fourth smartest man in London, and for daring I am not sure that he has not a claim to be third. I have known something of him before."\
\
"Evidently," said I, "Mr. Wilson's assistant counts for a good deal in this mystery of the Red-headed League. I am sure that you inquired your way merely in order that you might see him."\
\
"Not him."\
\
"What then?"\
\
"The knees of his trousers."\
\
"And what did you see?"\
\
"What I expected to see."\
\
"Why did you beat the pavement?"\
\
"My dear doctor, this is a time for observation, not for talk. We are spies in an enemy's country. We know something of Saxe-Coburg Square. Let us now explore the parts which lie behind it."\
\
The road in which we found ourselves as we turned round the corner from the retired Saxe-Coburg Square presented as great a contrast to it as the front of a picture does to the back. It was one of the main arteries which conveyed the traffic of the City to the north and west. The roadway was blocked with the immense stream of commerce flowing in a double tide inward and outward, while the footpaths were black with the hurrying swarm of pedestrians. It was difficult to realise as we looked at the line of fine shops and stately business premises that they really abutted on the other side upon the faded and stagnant square which we had just quitted.\
\
"Let me see," said Holmes, standing at the corner and glancing along the line, "I should like just to remember the order of the houses here. It is a hobby of mine to have an exact knowledge of London. There is Mortimer's, the tobacconist, the little newspaper shop, the Coburg branch of the City and Suburban Bank, the Vegetarian Restaurant, and McFarlane's carriage-building depot. That carries us right on to the other block. And now, Doctor, we've done our work, so it's time we had some play. A sandwich and a cup of coffee, and then off to violin-land, where all is sweetness and delicacy and harmony, and there are no red-headed clients to vex us with their conundrums."\
\
My friend was an enthusiastic musician, being himself not only a very capable performer but a composer of no ordinary merit. All the afternoon he sat in the stalls wrapped in the most perfect happiness, gently waving his long, thin fingers in time to the music, while his gently smiling face and his languid, dreamy eyes were as unlike those of Holmes the sleuth-hound, Holmes the relentless, keen-witted, ready-handed criminal agent, as it was possible to conceive. In his singular character the dual nature alternately asserted itself, and his extreme exactness and astuteness represented, as I have often thought, the reaction against the poetic and contemplative mood which occasionally predominated in him. The swing of his nature took him from extreme languor to devouring energy; and, as I knew well, he was never so truly formidable as when, for days on end, he had been lounging in his armchair amid his improvisations and his black-letter editions. Then it was that the lust of the chase would suddenly come upon him, and that his brilliant reasoning power would rise to the level of intuition, until those who were unacquainted with his methods would look askance at him as on a man whose knowledge was not that of other mortals. When I saw him that afternoon so enwrapped in the music at St. James's Hall I felt that an evil time might be coming upon those whom he had set himself to hunt down.\
\
"You want to go home, no doubt, Doctor," he remarked as we emerged.\
\
"Yes, it would be as well."\
\
"And I have some business to do which will take some hours. This business at Coburg Square is serious."\
\
"Why serious?"\
\
"A considerable crime is in contemplation. I have every reason to believe that we shall be in time to stop it. But to-day being Saturday rather complicates matters. I shall want your help to-night."\
\
"At what time?"\
\
"Ten will be early enough."\
\
"I shall be at Baker Street at ten."\
\
"Very well. And, I say, Doctor, there may be some little danger, so kindly put your army revolver in your pocket." He waved his hand, turned on his heel, and disappeared in an instant among the crowd.\
\
I trust that I am not more dense than my neighbours, but I was always oppressed with a sense of my own stupidity in my dealings with Sherlock Holmes. Here I had heard what he had heard, I had seen what he had seen, and yet from his words it was evident that he saw clearly not only what had happened but what was about to happen, while to me the whole business was still confused and grotesque. As I drove home to my house in Kensington I thought over it all, from the extraordinary story of the red-headed copier of the Encyclopaedia down to the visit to Saxe-Coburg Square, and the ominous words with which he had parted from me. What was this nocturnal expedition, and why should I go armed? Where were we going, and what were we to do? I had the hint from Holmes that this smooth-faced pawnbroker's assistant was a formidable man--a man who might play a deep game. I tried to puzzle it out, but gave it up in despair and set the matter aside until night should bring an explanation.\
\
It was a quarter-past nine when I started from home and made my way across the Park, and so through Oxford Street to Baker Street. Two hansoms were standing at the door, and as I entered the passage I heard the sound of voices from above. On entering his room, I found Holmes in animated conversation with two men, one of whom I recognised as Peter Jones, the official police agent, while the other was a long, thin, sad-faced man, with a very shiny hat and oppressively respectable frock-coat.\
\
"Ha! Our party is complete," said Holmes, buttoning up his pea-jacket and taking his heavy hunting crop from the rack. "Watson, I think you know Mr. Jones, of Scotland Yard? Let me introduce you to Mr. Merryweather, who is to be our companion in to-night's adventure."\
\
"We're hunting in couples again, Doctor, you see," said Jones in his consequential way. "Our friend here is a wonderful man for starting a chase. All he wants is an old dog to help him to do the running down."\
\
"I hope a wild goose may not prove to be the end of our chase," observed Mr. Merryweather gloomily.\
\
"You may place considerable confidence in Mr. Holmes, sir," said the police agent loftily. "He has his own little methods, which are, if he won't mind my saying so, just a little too theoretical and fantastic, but he has the makings of a detective in him. It is not too much to say that once or twice, as in that business of the Sholto murder and the Agra treasure, he has been more nearly correct than the official force."\
\
"Oh, if you say so, Mr. Jones, it is all right," said the stranger with deference. "Still, I confess that I miss my rubber. It is the first Saturday night for seven-and-twenty years that I have not had my rubber."\
\
"I think you will find," said Sherlock Holmes, "that you will play for a higher stake to-night than you have ever done yet, and that the play will be more exciting. For you, Mr. Merryweather, the stake will be some $30,000; and for you, Jones, it will be the man upon whom you wish to lay your hands."\
\
"John Clay, the murderer, thief, smasher, and forger. He's a young man, Mr. Merryweather, but he is at the head of his profession, and I would rather have my bracelets on him than on any criminal in London. He's a remarkable man, is young John Clay. His grandfather was a royal duke, and he himself has been to Eton and Oxford. His brain is as cunning as his fingers, and though we meet signs of him at every turn, we never know where to find the man himself. He'll crack a crib in Scotland one week, and be raising money to build an orphanage in Cornwall the next. I've been on his track for years and have never set eyes on him yet."\
\
"I hope that I may have the pleasure of introducing you to-night. I've had one or two little turns also with Mr. John Clay, and I agree with you that he is at the head of his profession. It is past ten, however, and quite time that we started. If you two will take the first hansom, Watson and I will follow in the second."\
\
Sherlock Holmes was not very communicative during the long drive and lay back in the cab humming the tunes which he had heard in the afternoon. We rattled through an endless labyrinth of gas-lit streets until we emerged into Farrington Street.\
\
"We are close there now," my friend remarked. "This fellow Merryweather is a bank director, and personally interested in the matter. I thought it as well to have Jones with us also. He is not a bad fellow, though an absolute imbecile in his profession. He has one positive virtue. He is as brave as a bulldog and as tenacious as a lobster if he gets his claws upon anyone. Here we are, and they are waiting for us."\
\
We had reached the same crowded thoroughfare in which we had found ourselves in the morning. Our cabs were dismissed, and, following the guidance of Mr. Merryweather, we passed down a narrow passage and through a side door, which he opened for us. Within there was a small corridor, which ended in a very massive iron gate. This also was opened, and led down a flight of winding stone steps, which terminated at another formidable gate. Mr. Merryweather stopped to light a lantern, and then conducted us down a dark, earth-smelling passage, and so, after opening a third door, into a huge vault or cellar, which was piled all round with crates and massive boxes.\
\
"You are not very vulnerable from above," Holmes remarked as he held up the lantern and gazed about him.\
\
"Nor from below," said Mr. Merryweather, striking his stick upon the flags which lined the floor. "Why, dear me, it sounds quite hollow!" he remarked, looking up in surprise.\
\
"I must really ask you to be a little more quiet!" said Holmes severely. "You have already imperilled the whole success of our expedition. Might I beg that you would have the goodness to sit down upon one of those boxes, and not to interfere?"\
\
The solemn Mr. Merryweather perched himself upon a crate, with a very injured expression upon his face, while Holmes fell upon his knees upon the floor and, with the lantern and a magnifying lens, began to examine minutely the cracks between the stones. A few seconds sufficed to satisfy him, for he sprang to his feet again and put his glass in his pocket.\
\
"We have at least an hour before us," he remarked, "for they can hardly take any steps until the good pawnbroker is safely in bed. Then they will not lose a minute, for the sooner they do their work the longer time they will have for their escape. We are at present, Doctor--as no doubt you have divined--in the cellar of the City branch of one of the principal London banks. Mr. Merryweather is the chairman of directors, and he will explain to you that there are reasons why the more daring criminals of London should take a considerable interest in this cellar at present."\
\
"It is our French gold," whispered the director. "We have had several warnings that an attempt might be made upon it."\
\
"Your French gold?"\
\
"Yes. We had occasion some months ago to strengthen our resources and borrowed for that purpose 30,000 napoleons from the Bank of France. It has become known that we have never had occasion to unpack the money, and that it is still lying in our cellar. The crate upon which I sit contains 2,000 napoleons packed between layers of lead foil. Our reserve of bullion is much larger at present than is usually kept in a single branch office, and the directors have had misgivings upon the subject."\
\
"Which were very well justified," observed Holmes. "And now it is time that we arranged our little plans. I expect that within an hour matters will come to a head. In the meantime Mr. Merryweather, we must put the screen over that dark lantern."\
\
"And sit in the dark?"\
\
"I am afraid so. I had brought a pack of cards in my pocket, and I thought that, as we were a partie carree, you might have your rubber after all. But I see that the enemy's preparations have gone so far that we cannot risk the presence of a light. And, first of all, we must choose our positions. These are daring men, and though we shall take them at a disadvantage, they may do us some harm unless we are careful. I shall stand behind this crate, and do you conceal yourselves behind those. Then, when I flash a light upon them, close in swiftly. If they fire, Watson, have no compunction about shooting them down."\
\
I placed my revolver, cocked, upon the top of the wooden case behind which I crouched. Holmes shot the slide across the front of his lantern and left us in pitch darkness--such an absolute darkness as I have never before experienced. The smell of hot metal remained to assure us that the light was still there, ready to flash out at a moment's notice. To me, with my nerves worked up to a pitch of expectancy, there was something depressing and subduing in the sudden gloom, and in the cold dank air of the vault.\
\
"They have but one retreat," whispered Holmes. "That is back through the house into Saxe-Coburg Square. I hope that you have done what I asked you, Jones?"\
\
"I have an inspector and two officers waiting at the front door."\
\
"Then we have stopped all the holes. And now we must be silent and wait."\
\
What a time it seemed! From comparing notes afterwards it was but an hour and a quarter, yet it appeared to me that the night must have almost gone, and the dawn be breaking above us. My limbs were weary and stiff, for I feared to change my position; yet my nerves were worked up to the highest pitch of tension, and my hearing was so acute that I could not only hear the gentle breathing of my companions, but I could distinguish the deeper, heavier in-breath of the bulky Jones from the thin, sighing note of the bank director. From my position I could look over the case in the direction of the floor. Suddenly my eyes caught the glint of a light.\
\
At first it was but a lurid spark upon the stone pavement. Then it lengthened out until it became a yellow line, and then, without any warning or sound, a gash seemed to open and a hand appeared, a white, almost womanly hand, which felt about in the centre of the little area of light. For a minute or more the hand, with its writhing fingers, protruded out of the floor. Then it was withdrawn as suddenly as it appeared, and all was dark again save the single lurid spark which marked a chink between the stones.\
\
Its disappearance, however, was but momentary. With a rending, tearing sound, one of the broad, white stones turned over upon its side and left a square, gaping hole, through which streamed the light of a lantern. Over the edge there peeped a clean-cut, boyish face, which looked keenly about it, and then, with a hand on either side of the aperture, drew itself shoulder-high and waist-high, until one knee rested upon the edge. In another instant he stood at the side of the hole and was hauling after him a companion, lithe and small like himself, with a pale face and a shock of very red hair.\
\
"It's all clear," he whispered. "Have you the chisel and the bags? Great Scott! Jump, Archie, jump, and I'll swing for it!"\
\
Sherlock Holmes had sprung out and seized the intruder by the collar. The other dived down the hole, and I heard the sound of rending cloth as Jones clutched at his skirts. The light flashed upon the barrel of a revolver, but Holmes' hunting crop came down on the man's wrist, and the pistol clinked upon the stone floor.\
\
"It's no use, John Clay," said Holmes blandly. "You have no chance at all."\
\
"So I see," the other answered with the utmost coolness. "I fancy that my pal is all right, though I see you have got his coat-tails."\
\
"There are three men waiting for him at the door," said Holmes.\
\
"Oh, indeed! You seem to have done the thing very completely. I must compliment you."\
\
"And I you," Holmes answered. "Your red-headed idea was very new and effective."\
\
"You'll see your pal again presently," said Jones. "He's quicker at climbing down holes than I am. Just hold out while I fix the derbies."\
\
"I beg that you will not touch me with your filthy hands," remarked our prisoner as the handcuffs clattered upon his wrists. "You may not be aware that I have royal blood in my veins. Have the goodness, also, when you address me always to say 'sir' and 'please.' "\
\
"All right," said Jones with a stare and a snigger. "Well, would you please, sir, march upstairs, where we can get a cab to carry your Highness to the police-station?"\
\
"That is better," said John Clay serenely. He made a sweeping bow to the three of us and walked quietly off in the custody of the detective.\
\
"Really, Mr. Holmes," said Mr. Merryweather as we followed them from the cellar, "I do not know how the bank can thank you or repay you. There is no doubt that you have detected and defeated in the most complete manner one of the most determined attempts at bank robbery that have ever come within my experience."\
\
"I have had one or two little scores of my own to settle with Mr. John Clay," said Holmes. "I have been at some small expense over this matter, which I shall expect the bank to refund, but beyond that I am amply repaid by having had an experience which is in many ways unique, and by hearing the very remarkable narrative of the Red-headed League."\
\
"You see, Watson," he explained in the early hours of the morning as we sat over a glass of whisky and soda in Baker Street, "it was perfectly obvious from the first that the only possible object of this rather fantastic business of the advertisement of the League, and the copying of the Encyclopaedia, must be to get this not over-bright pawnbroker out of the way for a number of hours every day. It was a curious way of managing it, but, really, it would be difficult to suggest a better. The method was no doubt suggested to Clay's ingenious mind by the colour of his accomplice's hair. The $4 a week was a lure which must draw him, and what was it to them, who were playing for thousands? They put in the advertisement, one rogue has the temporary office, the other rogue incites the man to apply for it, and together they manage to secure his absence every morning in the week. From the time that I heard of the assistant having come for half wages, it was obvious to me that he had some strong motive for securing the situation."\
\
"But how could you guess what the motive was?"\
\
"Had there been women in the house, I should have suspected a mere vulgar intrigue. That, however, was out of the question. The man's business was a small one, and there was nothing in his house which could account for such elaborate preparations, and such an expenditure as they were at. It must, then, be something out of the house. What could it be? I thought of the assistant's fondness for photography, and his trick of vanishing into the cellar. The cellar! There was the end of this tangled clue. Then I made inquiries as to this mysterious assistant and found that I had to deal with one of the coolest and most daring criminals in London. He was doing something in the cellar--something which took many hours a day for months on end. What could it be, once more? I could think of nothing save that he was running a tunnel to some other building.\
\
"So far I had got when we went to visit the scene of action. I surprised you by beating upon the pavement with my stick. I was ascertaining whether the cellar stretched out in front or behind. It was not in front. Then I rang the bell, and, as I hoped, the assistant answered it. We have had some skirmishes, but we had never set eyes upon each other before. I hardly looked at his face. His knees were what I wished to see. You must yourself have remarked how worn, wrinkled, and stained they were. They spoke of those hours of burrowing. The only remaining point was what they were burrowing for. I walked round the corner, saw the City and Suburban Bank abutted on our friend's premises, and felt that I had solved my problem. When you drove home after the concert I called upon Scotland Yard and upon the chairman of the bank directors, with the result that you have seen."\
\
"And how could you tell that they would make their attempt to-night?" I asked.\
\
"Well, when they closed their League offices that was a sign that they cared no longer about Mr. Jabez Wilson's presence--in other words, that they had completed their tunnel. But it was essential that they should use it soon, as it might be discovered, or the bullion might be removed. Saturday would suit them better than any other day, as it would give them two days for their escape. For all these reasons I expected them to come to-night."\
\
"You reasoned it out beautifully," I exclaimed in unfeigned admiration. "It is so long a chain, and yet every link rings true."\
\
"It saved me from ennui," he answered, yawning. "Alas! I already feel it closing in upon me. My life is spent in one long effort to escape from the commonplaces of existence. These little problems help me to do so."\
\
"And you are a benefactor of the race," said I.\
\
He shrugged his shoulders. "Well, perhaps, after all, it is of some little use," he remarked. " 'L'homme c'est rien--l'oeuvre c'est tout,' as Gustave Flaubert wrote to George Sand."\
\
ADVENTURE  III.  A CASE OF IDENTITY\
\
\
"My dear fellow," said Sherlock Holmes as we sat on either side of the fire in his lodgings at Baker Street, "life is infinitely stranger than anything which the mind of man could invent. We would not dare to conceive the things which are really mere commonplaces of existence. If we could fly out of that window hand in hand, hover over this great city, gently remove the roofs, and peep in at the queer things which are going on, the strange coincidences, the plannings, the cross-purposes, the wonderful chains of events, working through generations, and leading to the most outre results, it would make all fiction with its conventionalities and foreseen conclusions most stale and unprofitable."\
\
"And yet I am not convinced of it," I answered. "The cases which come to light in the papers are, as a rule, bald enough, and vulgar enough. We have in our police reports realism pushed to its extreme limits, and yet the result is, it must be confessed, neither fascinating nor artistic."\
\
"A certain selection and discretion must be used in producing a realistic effect," remarked Holmes. "This is wanting in the police report, where more stress is laid, perhaps, upon the platitudes of the magistrate than upon the details, which to an observer contain the vital essence of the whole matter. Depend upon it, there is nothing so unnatural as the commonplace."\
\
I smiled and shook my head. "I can quite understand your thinking so." I said. "Of course, in your position of unofficial adviser and helper to everybody who is absolutely puzzled, throughout three continents, you are brought in contact with all that is strange and bizarre. But here"--I picked up the morning paper from the ground--"let us put it to a practical test. Here is the first heading upon which I come. 'A husband's cruelty to his wife.' There is half a column of print, but I know without reading it that it is all perfectly familiar to me. There is, of course, the other woman, the drink, the push, the blow, the bruise, the sympathetic sister or landlady. The crudest of writers could invent nothing more crude."\
\
"Indeed, your example is an unfortunate one for your argument," said Holmes, taking the paper and glancing his eye down it. "This is the Dundas separation case, and, as it happens, I was engaged in clearing up some small points in connection with it. The husband was a teetotaler, there was no other woman, and the conduct complained of was that he had drifted into the habit of winding up every meal by taking out his false teeth and hurling them at his wife, which, you will allow, is not an action likely to occur to the imagination of the average story-teller. Take a pinch of snuff, Doctor, and acknowledge that I have scored over you in your example."\
\
He held out his snuffbox of old gold, with a great amethyst in the centre of the lid. Its splendour was in such contrast to his homely ways and simple life that I could not help commenting upon it.\
\
"Ah," said he, "I forgot that I had not seen you for some weeks. It is a little souvenir from the King of Bohemia in return for my assistance in the case of the Irene Adler papers."\
\
"And the ring?" I asked, glancing at a remarkable brilliant which sparkled upon his finger.\
\
"It was from the reigning family of Holland, though the matter in which I served them was of such delicacy that I cannot confide it even to you, who have been good enough to chronicle one or two of my little problems."\
\
"And have you any on hand just now?" I asked with interest.\
\
"Some ten or twelve, but none which present any feature of interest. They are important, you understand, without being interesting. Indeed, I have found that it is usually in unimportant matters that there is a field for the observation, and for the quick analysis of cause and effect which gives the charm to an investigation. The larger crimes are apt to be the simpler, for the bigger the crime the more obvious, as a rule, is the motive. In these cases, save for one rather intricate matter which has been referred to me from Marseilles, there is nothing which presents any features of interest. It is possible, however, that I may have something better before very many minutes are over, for this is one of my clients, or I am much mistaken."\
\
He had risen from his chair and was standing between the parted blinds gazing down into the dull neutral-tinted London street. Looking over his shoulder, I saw that on the pavement opposite there stood a large woman with a heavy fur boa round her neck, and a large curling red feather in a broad-brimmed hat which was tilted in a coquettish Duchess of Devonshire fashion over her ear. From under this great panoply she peeped up in a nervous, hesitating fashion at our windows, while her body oscillated backward and forward, and her fingers fidgeted with her glove buttons. Suddenly, with a plunge, as of the swimmer who leaves the bank, she hurried across the road, and we heard the sharp clang of the bell.\
\
"I have seen those symptoms before," said Holmes, throwing his cigarette into the fire. "Oscillation upon the pavement always means an affaire de coeur. She would like advice, but is not sure that the matter is not too delicate for communication. And yet even here we may discriminate. When a woman has been seriously wronged by a man she no longer oscillates, and the usual symptom is a broken bell wire. Here we may take it that there is a love matter, but that the maiden is not so much angry as perplexed, or grieved. But here she comes in person to resolve our doubts."\
\
As he spoke there was a tap at the door, and the boy in buttons entered to announce Miss Mary Sutherland, while the lady herself loomed behind his small black figure like a full-sailed merchant-man behind a tiny pilot boat. Sherlock Holmes welcomed her with the easy courtesy for which he was remarkable, and, having closed the door and bowed her into an armchair, he looked her over in the minute and yet abstracted fashion which was peculiar to him.\
\
"Do you not find," he said, "that with your short sight it is a little trying to do so much typewriting?"\
\
"I did at first," she answered, "but now I know where the letters are without looking." Then, suddenly realising the full purport of his words, she gave a violent start and looked up, with fear and astonishment upon her broad, good-humoured face. "You've heard about me, Mr. Holmes," she cried, "else how could you know all that?"\
\
"Never mind," said Holmes, laughing; "it is my business to know things. Perhaps I have trained myself to see what others overlook. If not, why should you come to consult me?"\
\
"I came to you, sir, because I heard of you from Mrs. Etherege, whose husband you found so easy when the police and everyone had given him up for dead. Oh, Mr. Holmes, I wish you would do as much for me. I'm not rich, but still I have a hundred a year in my own right, besides the little that I make by the machine, and I would give it all to know what has become of Mr. Hosmer Angel."\
\
"Why did you come away to consult me in such a hurry?" asked Sherlock Holmes, with his finger-tips together and his eyes to the ceiling.\
\
Again a startled look came over the somewhat vacuous face of Miss Mary Sutherland. "Yes, I did bang out of the house," she said, "for it made me angry to see the easy way in which Mr. Windibank--that is, my father--took it all. He would not go to the police, and he would not go to you, and so at last, as he would do nothing and kept on saying that there was no harm done, it made me mad, and I just on with my things and came right away to you."\
\
"Your father," said Holmes, "your stepfather, surely, since the name is different."\
\
"Yes, my stepfather. I call him father, though it sounds funny, too, for he is only five years and two months older than myself."\
\
"And your mother is alive?"\
\
"Oh, yes, mother is alive and well. I wasn't best pleased, Mr. Holmes, when she married again so soon after father's death, and a man who was nearly fifteen years younger than herself. Father was a plumber in the Tottenham Court Road, and he left a tidy business behind him, which mother carried on with Mr. Hardy, the foreman; but when Mr. Windibank came he made her sell the business, for he was very superior, being a traveller in wines. They got $4700 for the goodwill and interest, which wasn't near as much as father could have got if he had been alive."\
\
I had expected to see Sherlock Holmes impatient under this rambling and inconsequential narrative, but, on the contrary, he had listened with the greatest concentration of attention.\
\
"Your own little income," he asked, "does it come out of the business?"\
\
"Oh, no, sir. It is quite separate and was left me by my uncle Ned in Auckland. It is in New Zealand stock, paying 4 1/4 per cent. Two thousand five hundred pounds was the amount, but I can only touch the interest."\
\
"You interest me extremely," said Holmes. "And since you draw so large a sum as a hundred a year, with what you earn into the bargain, you no doubt travel a little and indulge yourself in every way. I believe that a single lady can get on very nicely upon an income of about $60."\
\
"I could do with much less than that, Mr. Holmes, but you understand that as long as I live at home I don't wish to be a burden to them, and so they have the use of the money just while I am staying with them. Of course, that is only just for the time. Mr. Windibank draws my interest every quarter and pays it over to mother, and I find that I can do pretty well with what I earn at typewriting. It brings me twopence a sheet, and I can often do from fifteen to twenty sheets in a day."\
\
"You have made your position very clear to me," said Holmes. "This is my friend, Dr. Watson, before whom you can speak as freely as before myself. Kindly tell us now all about your connection with Mr. Hosmer Angel."\
\
A flush stole over Miss Sutherland's face, and she picked nervously at the fringe of her jacket. "I met him first at the gasfitters' ball," she said. "They used to send father tickets when he was alive, and then afterwards they remembered us, and sent them to mother. Mr. Windibank did not wish us to go. He never did wish us to go anywhere. He would get quite mad if I wanted so much as to join a Sunday-school treat. But this time I was set on going, and I would go; for what right had he to prevent? He said the folk were not fit for us to know, when all father's friends were to be there. And he said that I had nothing fit to wear, when I had my purple plush that I had never so much as taken out of the drawer. At last, when nothing else would do, he went off to France upon the business of the firm, but we went, mother and I, with Mr. Hardy, who used to be our foreman, and it was there I met Mr. Hosmer Angel."\
\
"I suppose," said Holmes, "that when Mr. Windibank came back from France he was very annoyed at your having gone to the ball."\
\
"Oh, well, he was very good about it. He laughed, I remember, and shrugged his shoulders, and said there was no use denying anything to a woman, for she would have her way."\
\
"I see. Then at the gasfitters' ball you met, as I understand, a gentleman called Mr. Hosmer Angel."\
\
"Yes, sir. I met him that night, and he called next day to ask if we had got home all safe, and after that we met him--that is to say, Mr. Holmes, I met him twice for walks, but after that father came back again, and Mr. Hosmer Angel could not come to the house any more."\
\
"No?"\
\
"Well, you know father didn't like anything of the sort. He wouldn't have any visitors if he could help it, and he used to say that a woman should be happy in her own family circle. But then, as I used to say to mother, a woman wants her own circle to begin with, and I had not got mine yet."\
\
"But how about Mr. Hosmer Angel? Did he make no attempt to see you?"\
\
"Well, father was going off to France again in a week, and Hosmer wrote and said that it would be safer and better not to see each other until he had gone. We could write in the meantime, and he used to write every day. I took the letters in in the morning, so there was no need for father to know."\
\
"Were you engaged to the gentleman at this time?"\
\
"Oh, yes, Mr. Holmes. We were engaged after the first walk that we took. Hosmer--Mr. Angel--was a cashier in an office in Leadenhall Street--and--"\
\
"What office?"\
\
"That's the worst of it, Mr. Holmes, I don't know."\
\
"Where did he live, then?"\
\
"He slept on the premises."\
\
"And you don't know his address?"\
\
"No--except that it was Leadenhall Street."\
\
"Where did you address your letters, then?"\
\
"To the Leadenhall Street Post Office, to be left till called for. He said that if they were sent to the office he would be chaffed by all the other clerks about having letters from a lady, so I offered to typewrite them, like he did his, but he wouldn't have that, for he said that when I wrote them they seemed to come from me, but when they were typewritten he always felt that the machine had come between us. That will just show you how fond he was of me, Mr. Holmes, and the little things that he would think of."\
\
"It was most suggestive," said Holmes. "It has long been an axiom of mine that the little things are infinitely the most important. Can you remember any other little things about Mr. Hosmer Angel?"\
\
"He was a very shy man, Mr. Holmes. He would rather walk with me in the evening than in the daylight, for he said that he hated to be conspicuous. Very retiring and gentlemanly he was. Even his voice was gentle. He'd had the quinsy and swollen glands when he was young, he told me, and it had left him with a weak throat, and a hesitating, whispering fashion of speech. He was always well dressed, very neat and plain, but his eyes were weak, just as mine are, and he wore tinted glasses against the glare."\
\
"Well, and what happened when Mr. Windibank, your stepfather, returned to France?"\
\
"Mr. Hosmer Angel came to the house again and proposed that we should marry before father came back. He was in dreadful earnest and made me swear, with my hands on the Testament, that whatever happened I would always be true to him. Mother said he was quite right to make me swear, and that it was a sign of his passion. Mother was all in his favour from the first and was even fonder of him than I was. Then, when they talked of marrying within the week, I began to ask about father; but they both said never to mind about father, but just to tell him afterwards, and mother said she would make it all right with him. I didn't quite like that, Mr. Holmes. It seemed funny that I should ask his leave, as he was only a few years older than me; but I didn't want to do anything on the sly, so I wrote to father at Bordeaux, where the company has its French offices, but the letter came back to me on the very morning of the wedding."\
\
"It missed him, then?"\
\
"Yes, sir; for he had started to England just before it arrived."\
\
"Ha! that was unfortunate. Your wedding was arranged, then, for the Friday. Was it to be in church?"\
\
"Yes, sir, but very quietly. It was to be at St. Saviour's, near King's Cross, and we were to have breakfast afterwards at the St. Pancras Hotel. Hosmer came for us in a hansom, but as there were two of us he put us both into it and stepped himself into a four-wheeler, which happened to be the only other cab in the street. We got to the church first, and when the four-wheeler drove up we waited for him to step out, but he never did, and when the cabman got down from the box and looked there was no one there! The cabman said that he could not imagine what had become of him, for he had seen him get in with his own eyes. That was last Friday, Mr. Holmes, and I have never seen or heard anything since then to throw any light upon what became of him."\
\
"It seems to me that you have been very shamefully treated," said Holmes.\
\
"Oh, no, sir! He was too good and kind to leave me so. Why, all the morning he was saying to me that, whatever happened, I was to be true; and that even if something quite unforeseen occurred to separate us, I was always to remember that I was pledged to him, and that he would claim his pledge sooner or later. It seemed strange talk for a wedding-morning, but what has happened since gives a meaning to it."\
\
"Most certainly it does. Your own opinion is, then, that some unforeseen catastrophe has occurred to him?"\
\
"Yes, sir. I believe that he foresaw some danger, or else he would not have talked so. And then I think that what he foresaw happened."\
\
"But you have no notion as to what it could have been?"\
\
"None."\
\
"One more question. How did your mother take the matter?"\
\
"She was angry, and said that I was never to speak of the matter again."\
\
"And your father? Did you tell him?"\
\
"Yes; and he seemed to think, with me, that something had happened, and that I should hear of Hosmer again. As he said, what interest could anyone have in bringing me to the doors of the church, and then leaving me? Now, if he had borrowed my money, or if he had married me and got my money settled on him, there might be some reason, but Hosmer was very independent about money and never would look at a shilling of mine. And yet, what could have happened? And why could he not write? Oh, it drives me half-mad to think of it, and I can't sleep a wink at night." She pulled a little handkerchief out of her muff and began to sob heavily into it.\
\
"I shall glance into the case for you," said Holmes, rising, "and I have no doubt that we shall reach some definite result. Let the weight of the matter rest upon me now, and do not let your mind dwell upon it further. Above all, try to let Mr. Hosmer Angel vanish from your memory, as he has done from your life."\
\
"Then you don't think I'll see him again?"\
\
"I fear not."\
\
"Then what has happened to him?"\
\
"You will leave that question in my hands. I should like an accurate description of him and any letters of his which you can spare."\
\
"I advertised for him in last Saturday's Chronicle," said she. "Here is the slip and here are four letters from him."\
\
"Thank you. And your address?"\
\
"No. 31 Lyon Place, Camberwell."\
\
"Mr. Angel's address you never had, I understand. Where is your father's place of business?"\
\
"He travels for Westhouse & Marbank, the great claret importers of Fenchurch Street."\
\
"Thank you. You have made your statement very clearly. You will leave the papers here, and remember the advice which I have given you. Let the whole incident be a sealed book, and do not allow it to affect your life."\
\
"You are very kind, Mr. Holmes, but I cannot do that. I shall be true to Hosmer. He shall find me ready when he comes back."\
\
For all the preposterous hat and the vacuous face, there was something noble in the simple faith of our visitor which compelled our respect. She laid her little bundle of papers upon the table and went her way, with a promise to come again whenever she might be summoned.\
\
Sherlock Holmes sat silent for a few minutes with his fingertips still pressed together, his legs stretched out in front of him, and his gaze directed upward to the ceiling. Then he took down from the rack the old and oily clay pipe, which was to him as a counsellor, and, having lit it, he leaned back in his chair, with the thick blue cloud-wreaths spinning up from him, and a look of infinite languor in his face.\
\
"Quite an interesting study, that maiden," he observed. "I found her more interesting than her little problem, which, by the way, is rather a trite one. You will find parallel cases, if you consult my index, in Andover in '77, and there was something of the sort at The Hague last year. Old as is the idea, however, there were one or two details which were new to me. But the maiden herself was most instructive."\
\
"You appeared to read a good deal upon her which was quite invisible to me," I remarked.\
\
"Not invisible but unnoticed, Watson. You did not know where to look, and so you missed all that was important. I can never bring you to realise the importance of sleeves, the suggestiveness of thumb-nails, or the great issues that may hang from a boot-lace. Now, what did you gather from that woman's appearance? Describe it."\
\
"Well, she had a slate-coloured, broad-brimmed straw hat, with a feather of a brickish red. Her jacket was black, with black beads sewn upon it, and a fringe of little black jet ornaments. Her dress was brown, rather darker than coffee colour, with a little purple plush at the neck and sleeves. Her gloves were greyish and were worn through at the right forefinger. Her boots I didn't observe. She had small round, hanging gold earrings, and a general air of being fairly well-to-do in a vulgar, comfortable, easy-going way."\
\
Sherlock Holmes clapped his hands softly together and chuckled.\
\
" 'Pon my word, Watson, you are coming along wonderfully. You have really done very well indeed. It is true that you have missed everything of importance, but you have hit upon the method, and you have a quick eye for colour. Never trust to general impressions, my boy, but concentrate yourself upon details. My first glance is always at a woman's sleeve. In a man it is perhaps better first to take the knee of the trouser. As you observe, this woman had plush upon her sleeves, which is a most useful material for showing traces. The double line a little above the wrist, where the typewritist presses against the table, was beautifully defined. The sewing-machine, of the hand type, leaves a similar mark, but only on the left arm, and on the side of it farthest from the thumb, instead of being right across the broadest part, as this was. I then glanced at her face, and, observing the dint of a pince-nez at either side of her nose, I ventured a remark upon short sight and typewriting, which seemed to surprise her."\
\
"It surprised me."\
\
"But, surely, it was obvious. I was then much surprised and interested on glancing down to observe that, though the boots which she was wearing were not unlike each other, they were really odd ones; the one having a slightly decorated toe-cap, and the other a plain one. One was buttoned only in the two lower buttons out of five, and the other at the first, third, and fifth. Now, when you see that a young lady, otherwise neatly dressed, has come away from home with odd boots, half-buttoned, it is no great deduction to say that she came away in a hurry."\
\
"And what else?" I asked, keenly interested, as I always was, by my friend's incisive reasoning.\
\
"I noted, in passing, that she had written a note before leaving home but after being fully dressed. You observed that her right glove was torn at the forefinger, but you did not apparently see that both glove and finger were stained with violet ink. She had written in a hurry and dipped her pen too deep. It must have been this morning, or the mark would not remain clear upon the finger. All this is amusing, though rather elementary, but I must go back to business, Watson. Would you mind reading me the advertised description of Mr. Hosmer Angel?"\
\
I held the little printed slip to the light.\
\
"Missing," it said, "on the morning of the fourteenth, a gentleman named Hosmer Angel. About five ft. seven in. in height; strongly built, sallow complexion, black hair, a little bald in the centre, bushy, black side-whiskers and moustache; tinted glasses, slight infirmity of speech. Was dressed, when last seen, in black frock-coat faced with silk, black waistcoat, gold Albert chain, and grey Harris tweed trousers, with brown gaiters over elastic-sided boots. Known to have been employed in an office in Leadenhall Street. Anybody bringing--"\
\
"That will do," said Holmes. "As to the letters," he continued, glancing over them, "they are very commonplace. Absolutely no clue in them to Mr. Angel, save that he quotes Balzac once. There is one remarkable point, however, which will no doubt strike you."\
\
"They are typewritten," I remarked.\
\
"Not only that, but the signature is typewritten. Look at the neat little 'Hosmer Angel' at the bottom. There is a date, you see, but no superscription except Leadenhall Street, which is rather vague. The point about the signature is very suggestive--in fact, we may call it conclusive."\
\
"Of what?"\
\
"My dear fellow, is it possible you do not see how strongly it bears upon the case?"\
\
"I cannot say that I do unless it were that he wished to be able to deny his signature if an action for breach of promise were instituted."\
\
"No, that was not the point. However, I shall write two letters, which should settle the matter. One is to a firm in the City, the other is to the young lady's stepfather, Mr. Windibank, asking him whether he could meet us here at six o'clock to-morrow evening. It is just as well that we should do business with the male relatives. And now, Doctor, we can do nothing until the answers to those letters come, so we may put our little problem upon the shelf for the interim."\
\
I had had so many reasons to believe in my friend's subtle powers of reasoning and extraordinary energy in action that I felt that he must have some solid grounds for the assured and easy demeanour with which he treated the singular mystery which he had been called upon to fathom. Once only had I known him to fail, in the case of the King of Bohemia and of the Irene Adler photograph; but when I looked back to the weird business of the Sign of Four, and the extraordinary circumstances connected with the Study in Scarlet, I felt that it would be a strange tangle indeed which he could not unravel.\
\
I left him then, still puffing at his black clay pipe, with the conviction that when I came again on the next evening I would find that he held in his hands all the clues which would lead up to the identity of the disappearing bridegroom of Miss Mary Sutherland.\
\
A professional case of great gravity was engaging my own attention at the time, and the whole of next day I was busy at the bedside of the sufferer. It was not until close upon six o'clock that I found myself free and was able to spring into a hansom and drive to Baker Street, half afraid that I might be too late to assist at the denouement of the little mystery. I found Sherlock Holmes alone, however, half asleep, with his long, thin form curled up in the recesses of his armchair. A formidable array of bottles and test-tubes, with the pungent cleanly smell of hydrochloric acid, told me that he had spent his day in the chemical work which was so dear to him.\
\
"Well, have you solved it?" I asked as I entered.\
\
"Yes. It was the bisulphate of baryta."\
\
"No, no, the mystery!" I cried.\
\
"Oh, that! I thought of the salt that I have been working upon. There was never any mystery in the matter, though, as I said yesterday, some of the details are of interest. The only drawback is that there is no law, I fear, that can touch the scoundrel."\
\
"Who was he, then, and what was his object in deserting Miss Sutherland?"\
\
The question was hardly out of my mouth, and Holmes had not yet opened his lips to reply, when we heard a heavy footfall in the passage and a tap at the door.\
\
"This is the girl's stepfather, Mr. James Windibank," said Holmes. "He has written to me to say that he would be here at six. Come in!"\
\
The man who entered was a sturdy, middle-sized fellow, some thirty years of age, clean-shaven, and sallow-skinned, with a bland, insinuating manner, and a pair of wonderfully sharp and penetrating grey eyes. He shot a questioning glance at each of us, placed his shiny top-hat upon the sideboard, and with a slight bow sidled down into the nearest chair.\
\
"Good-evening, Mr. James Windibank," said Holmes. "I think that this typewritten letter is from you, in which you made an appointment with me for six o'clock?"\
\
"Yes, sir. I am afraid that I am a little late, but I am not quite my own master, you know. I am sorry that Miss Sutherland has troubled you about this little matter, for I think it is far better not to wash linen of the sort in public. It was quite against my wishes that she came, but she is a very excitable, impulsive girl, as you may have noticed, and she is not easily controlled when she has made up her mind on a point. Of course, I did not mind you so much, as you are not connected with the official police, but it is not pleasant to have a family misfortune like this noised abroad. Besides, it is a useless expense, for how could you possibly find this Hosmer Angel?"\
\
"On the contrary," said Holmes quietly; "I have every reason to believe that I will succeed in discovering Mr. Hosmer Angel."\
\
Mr. Windibank gave a violent start and dropped his gloves. "I am delighted to hear it," he said.\
\
"It is a curious thing," remarked Holmes, "that a typewriter has really quite as much individuality as a man's handwriting. Unless they are quite new, no two of them write exactly alike. Some letters get more worn than others, and some wear only on one side. Now, you remark in this note of yours, Mr. Windibank, that in every case there is some little slurring over of the 'e,' and a slight defect in the tail of the 'r.' There are fourteen other characteristics, but those are the more obvious."\
\
"We do all our correspondence with this machine at the office, and no doubt it is a little worn," our visitor answered, glancing keenly at Holmes with his bright little eyes.\
\
"And now I will show you what is really a very interesting study, Mr. Windibank," Holmes continued. "I think of writing another little monograph some of these days on the typewriter and its relation to crime. It is a subject to which I have devoted some little attention. I have here four letters which purport to come from the missing man. They are all typewritten. In each case, not only are the 'e's' slurred and the 'r's' tailless, but you will observe, if you care to use my magnifying lens, that the fourteen other characteristics to which I have alluded are there as well."\
\
Mr. Windibank sprang out of his chair and picked up his hat. "I cannot waste time over this sort of fantastic talk, Mr. Holmes," he said. "If you can catch the man, catch him, and let me know when you have done it."\
\
"Certainly," said Holmes, stepping over and turning the key in the door. "I let you know, then, that I have caught him!"\
\
"What! where?" shouted Mr. Windibank, turning white to his lips and glancing about him like a rat in a trap.\
\
"Oh, it won't do--really it won't," said Holmes suavely. "There is no possible getting out of it, Mr. Windibank. It is quite too transparent, and it was a very bad compliment when you said that it was impossible for me to solve so simple a question. That's right! Sit down and let us talk it over."\
\
Our visitor collapsed into a chair, with a ghastly face and a glitter of moisture on his brow. "It--it's not actionable," he stammered.\
\
"I am very much afraid that it is not. But between ourselves, Windibank, it was as cruel and selfish and heartless a trick in a petty way as ever came before me. Now, let me just run over the course of events, and you will contradict me if I go wrong."\
\
The man sat huddled up in his chair, with his head sunk upon his breast, like one who is utterly crushed. Holmes stuck his feet up on the corner of the mantelpiece and, leaning back with his hands in his pockets, began talking, rather to himself, as it seemed, than to us.\
\
"The man married a woman very much older than himself for her money," said he, "and he enjoyed the use of the money of the daughter as long as she lived with them. It was a considerable sum, for people in their position, and the loss of it would have made a serious difference. It was worth an effort to preserve it. The daughter was of a good, amiable disposition, but affectionate and warm-hearted in her ways, so that it was evident that with her fair personal advantages, and her little income, she would not be allowed to remain single long. Now her marriage would mean, of course, the loss of a hundred a year, so what does her stepfather do to prevent it? He takes the obvious course of keeping her at home and forbidding her to seek the company of people of her own age. But soon he found that that would not answer forever. She became restive, insisted upon her rights, and finally announced her positive intention of going to a certain ball. What does her clever stepfather do then? He conceives an idea more creditable to his head than to his heart. With the connivance and assistance of his wife he disguised himself, covered those keen eyes with tinted glasses, masked the face with a moustache and a pair of bushy whiskers, sunk that clear voice into an insinuating whisper, and doubly secure on account of the girl's short sight, he appears as Mr. Hosmer Angel, and keeps off other lovers by making love himself."\
\
"It was only a joke at first," groaned our visitor. "We never thought that she would have been so carried away."\
\
"Very likely not. However that may be, the young lady was very decidedly carried away, and, having quite made up her mind that her stepfather was in France, the suspicion of treachery never for an instant entered her mind. She was flattered by the gentleman's attentions, and the effect was increased by the loudly expressed admiration of her mother. Then Mr. Angel began to call, for it was obvious that the matter should be pushed as far as it would go if a real effect were to be produced. There were meetings, and an engagement, which would finally secure the girl's affections from turning towards anyone else. But the deception could not be kept up forever. These pretended journeys to France were rather cumbrous. The thing to do was clearly to bring the business to an end in such a dramatic manner that it would leave a permanent impression upon the young lady's mind and prevent her from looking upon any other suitor for some time to come. Hence those vows of fidelity exacted upon a Testament, and hence also the allusions to a possibility of something happening on the very morning of the wedding. James Windibank wished Miss Sutherland to be so bound to Hosmer Angel, and so uncertain as to his fate, that for ten years to come, at any rate, she would not listen to another man. As far as the church door he brought her, and then, as he could go no farther, he conveniently vanished away by the old trick of stepping in at one door of a four-wheeler and out at the other. I think that was the chain of events, Mr. Windibank!"\
\
Our visitor had recovered something of his assurance while Holmes had been talking, and he rose from his chair now with a cold sneer upon his pale face.\
\
"It may be so, or it may not, Mr. Holmes," said he, "but if you are so very sharp you ought to be sharp enough to know that it is you who are breaking the law now, and not me. I have done nothing actionable from the first, but as long as you keep that door locked you lay yourself open to an action for assault and illegal constraint."\
\
"The law cannot, as you say, touch you," said Holmes, unlocking and throwing open the door, "yet there never was a man who deserved punishment more. If the young lady has a brother or a friend, he ought to lay a whip across your shoulders. By Jove!" he continued, flushing up at the sight of the bitter sneer upon the man's face, "it is not part of my duties to my client, but here's a hunting crop handy, and I think I shall just treat myself to--" He took two swift steps to the whip, but before he could grasp it there was a wild clatter of steps upon the stairs, the heavy hall door banged, and from the window we could see Mr. James Windibank running at the top of his speed down the road.\
\
"There's a cold-blooded scoundrel!" said Holmes, laughing, as he threw himself down into his chair once more. "That fellow will rise from crime to crime until he does something very bad, and ends on a gallows. The case has, in some respects, been not entirely devoid of interest."\
\
"I cannot now entirely see all the steps of your reasoning," I remarked.\
\
"Well, of course it was obvious from the first that this Mr. Hosmer Angel must have some strong object for his curious conduct, and it was equally clear that the only man who really profited by the incident, as far as we could see, was the stepfather. Then the fact that the two men were never together, but that the one always appeared when the other was away, was suggestive. So were the tinted spectacles and the curious voice, which both hinted at a disguise, as did the bushy whiskers. My suspicions were all confirmed by his peculiar action in typewriting his signature, which, of course, inferred that his handwriting was so familiar to her that she would recognise even the smallest sample of it. You see all these isolated facts, together with many minor ones, all pointed in the same direction."\
\
"And how did you verify them?"\
\
"Having once spotted my man, it was easy to get corroboration. I knew the firm for which this man worked. Having taken the printed description. I eliminated everything from it which could be the result of a disguise--the whiskers, the glasses, the voice, and I sent it to the firm, with a request that they would inform me whether it answered to the description of any of their travellers. I had already noticed the peculiarities of the typewriter, and I wrote to the man himself at his business address asking him if he would come here. As I expected, his reply was typewritten and revealed the same trivial but characteristic defects. The same post brought me a letter from Westhouse & Marbank, of Fenchurch Street, to say that the description tallied in every respect with that of their employe, James Windibank. Voila tout!"\
\
"And Miss Sutherland?"\
\
"If I tell her she will not believe me. You may remember the old Persian saying, 'There is danger for him who taketh the tiger cub, and danger also for whoso snatches a delusion from a woman.' There is as much sense in Hafiz as in Horace, and as much knowledge of the world."\
\
ADVENTURE IV. THE BOSCOMBE VALLEY MYSTERY\
\
\
We were seated at breakfast one morning, my wife and I, when the maid brought in a telegram. It was from Sherlock Holmes and ran in this way:\
\
"Have you a couple of days to spare? Have just been wired for from the west of England in connection with Boscombe Valley tragedy. Shall be glad if you will come with me. Air and scenery perfect. Leave Paddington by the 11:15."\
\
"What do you say, dear?" said my wife, looking across at me. "Will you go?"\
\
"I really don't know what to say. I have a fairly long list at present."\
\
"Oh, Anstruther would do your work for you. You have been looking a little pale lately. I think that the change would do you good, and you are always so interested in Mr. Sherlock Holmes' cases."\
\
"I should be ungrateful if I were not, seeing what I gained through one of them," I answered. "But if I am to go, I must pack at once, for I have only half an hour."\
\
My experience of camp life in Afghanistan had at least had the effect of making me a prompt and ready traveller. My wants were few and simple, so that in less than the time stated I was in a cab with my valise, rattling away to Paddington Station. Sherlock Holmes was pacing up and down the platform, his tall, gaunt figure made even gaunter and taller by his long grey travelling-cloak and close-fitting cloth cap.\
\
"It is really very good of you to come, Watson," said he. "It makes a considerable difference to me, having someone with me on whom I can thoroughly rely. Local aid is always either worthless or else biassed. If you will keep the two corner seats I shall get the tickets."\
\
We had the carriage to ourselves save for an immense litter of papers which Holmes had brought with him. Among these he rummaged and read, with intervals of note-taking and of meditation, until we were past Reading. Then he suddenly rolled them all into a gigantic ball and tossed them up onto the rack.\
\
"Have you heard anything of the case?" he asked.\
\
"Not a word. I have not seen a paper for some days."\
\
"The London press has not had very full accounts. I have just been looking through all the recent papers in order to master the particulars. It seems, from what I gather, to be one of those simple cases which are so extremely difficult."\
\
"That sounds a little paradoxical."\
\
"But it is profoundly true. Singularity is almost invariably a clue. The more featureless and commonplace a crime is, the more difficult it is to bring it home. In this case, however, they have established a very serious case against the son of the murdered man."\
\
"It is a murder, then?"\
\
"Well, it is conjectured to be so. I shall take nothing for granted until I have the opportunity of looking personally into it. I will explain the state of things to you, as far as I have been able to understand it, in a very few words.\
\
"Boscombe Valley is a country district not very far from Ross, in Herefordshire. The largest landed proprietor in that part is a Mr. John Turner, who made his money in Australia and returned some years ago to the old country. One of the farms which he held, that of Hatherley, was let to Mr. Charles McCarthy, who was also an ex-Australian. The men had known each other in the colonies, so that it was not unnatural that when they came to settle down they should do so as near each other as possible. Turner was apparently the richer man, so McCarthy became his tenant but still remained, it seems, upon terms of perfect equality, as they were frequently together. McCarthy had one son, a lad of eighteen, and Turner had an only daughter of the same age, but neither of them had wives living. They appear to have avoided the society of the neighbouring English families and to have led retired lives, though both the McCarthys were fond of sport and were frequently seen at the race-meetings of the neighbourhood. McCarthy kept two servants--a man and a girl. Turner had a considerable household, some half-dozen at the least. That is as much as I have been able to gather about the families. Now for the facts.\
\
"On June 3rd, that is, on Monday last, McCarthy left his house at Hatherley about three in the afternoon and walked down to the Boscombe Pool, which is a small lake formed by the spreading out of the stream which runs down the Boscombe Valley. He had been out with his serving-man in the morning at Ross, and he had told the man that he must hurry, as he had an appointment of importance to keep at three. From that appointment he never came back alive.\
\
"From Hatherley Farmhouse to the Boscombe Pool is a quarter of a mile, and two people saw him as he passed over this ground. One was an old woman, whose name is not mentioned, and the other was William Crowder, a game-keeper in the employ of Mr. Turner. Both these witnesses depose that Mr. McCarthy was walking alone. The game-keeper adds that within a few minutes of his seeing Mr. McCarthy pass he had seen his son, Mr. James McCarthy, going the same way with a gun under his arm. To the best of his belief, the father was actually in sight at the time, and the son was following him. He thought no more of the matter until he heard in the evening of the tragedy that had occurred.\
\
"The two McCarthys were seen after the time when William Crowder, the game-keeper, lost sight of them. The Boscombe Pool is thickly wooded round, with just a fringe of grass and of reeds round the edge. A girl of fourteen, Patience Moran, who is the daughter of the lodge-keeper of the Boscombe Valley estate, was in one of the woods picking flowers. She states that while she was there she saw, at the border of the wood and close by the lake, Mr. McCarthy and his son, and that they appeared to be having a violent quarrel. She heard Mr. McCarthy the elder using very strong language to his son, and she saw the latter raise up his hand as if to strike his father. She was so frightened by their violence that she ran away and told her mother when she reached home that she had left the two McCarthys quarrelling near Boscombe Pool, and that she was afraid that they were going to fight. She had hardly said the words when young Mr. McCarthy came running up to the lodge to say that he had found his father dead in the wood, and to ask for the help of the lodge-keeper. He was much excited, without either his gun or his hat, and his right hand and sleeve were observed to be stained with fresh blood. On following him they found the dead body stretched out upon the grass beside the pool. The head had been beaten in by repeated blows of some heavy and blunt weapon. The injuries were such as might very well have been inflicted by the butt-end of his son's gun, which was found lying on the grass within a few paces of the body. Under these circumstances the young man was instantly arrested, and a verdict of 'wilful murder' having been returned at the inquest on Tuesday, he was on Wednesday brought before the magistrates at Ross, who have referred the case to the next Assizes. Those are the main facts of the case as they came out before the coroner and the police-court."\
\
"I could hardly imagine a more damning case," I remarked. "If ever circumstantial evidence pointed to a criminal it does so here."\
\
"Circumstantial evidence is a very tricky thing," answered Holmes thoughtfully. "It may seem to point very straight to one thing, but if you shift your own point of view a little, you may find it pointing in an equally uncompromising manner to something entirely different. It must be confessed, however, that the case looks exceedingly grave against the young man, and it is very possible that he is indeed the culprit. There are several people in the neighbourhood, however, and among them Miss Turner, the daughter of the neighbouring landowner, who believe in his innocence, and who have retained Lestrade, whom you may recollect in connection with the Study in Scarlet, to work out the case in his interest. Lestrade, being rather puzzled, has referred the case to me, and hence it is that two middle-aged gentlemen are flying westward at fifty miles an hour instead of quietly digesting their breakfasts at home."\
\
"I am afraid," said I, "that the facts are so obvious that you will find little credit to be gained out of this case."\
\
"There is nothing more deceptive than an obvious fact," he answered, laughing. "Besides, we may chance to hit upon some other obvious facts which may have been by no means obvious to Mr. Lestrade. You know me too well to think that I am boasting when I say that I shall either confirm or destroy his theory by means which he is quite incapable of employing, or even of understanding. To take the first example to hand, I very clearly perceive that in your bedroom the window is upon the right-hand side, and yet I question whether Mr. Lestrade would have noted even so self-evident a thing as that."\
\
"How on earth--"\
\
"My dear fellow, I know you well. I know the military neatness which characterises you. You shave every morning, and in this season you shave by the sunlight; but since your shaving is less and less complete as we get farther back on the left side, until it becomes positively slovenly as we get round the angle of the jaw, it is surely very clear that that side is less illuminated than the other. I could not imagine a man of your habits looking at himself in an equal light and being satisfied with such a result. I only quote this as a trivial example of observation and inference. Therein lies my metier, and it is just possible that it may be of some service in the investigation which lies before us. There are one or two minor points which were brought out in the inquest, and which are worth considering."\
\
"What are they?"\
\
"It appears that his arrest did not take place at once, but after the return to Hatherley Farm. On the inspector of constabulary informing him that he was a prisoner, he remarked that he was not surprised to hear it, and that it was no more than his deserts. This observation of his had the natural effect of removing any traces of doubt which might have remained in the minds of the coroner's jury."\
\
"It was a confession," I ejaculated.\
\
"No, for it was followed by a protestation of innocence."\
\
"Coming on the top of such a damning series of events, it was at least a most suspicious remark."\
\
"On the contrary," said Holmes, "it is the brightest rift which I can at present see in the clouds. However innocent he might be, he could not be such an absolute imbecile as not to see that the circumstances were very black against him. Had he appeared surprised at his own arrest, or feigned indignation at it, I should have looked upon it as highly suspicious, because such surprise or anger would not be natural under the circumstances, and yet might appear to be the best policy to a scheming man. His frank acceptance of the situation marks him as either an innocent man, or else as a man of considerable self-restraint and firmness. As to his remark about his deserts, it was also not unnatural if you consider that he stood beside the dead body of his father, and that there is no doubt that he had that very day so far forgotten his filial duty as to bandy words with him, and even, according to the little girl whose evidence is so important, to raise his hand as if to strike him. The self-reproach and contrition which are displayed in his remark appear to me to be the signs of a healthy mind rather than of a guilty one."\
\
I shook my head. "Many men have been hanged on far slighter evidence," I remarked.\
\
"So they have. And many men have been wrongfully hanged."\
\
"What is the young man's own account of the matter?"\
\
"It is, I am afraid, not very encouraging to his supporters, though there are one or two points in it which are suggestive. You will find it here, and may read it for yourself."\
\
He picked out from his bundle a copy of the local Herefordshire paper, and having turned down the sheet he pointed out the paragraph in which the unfortunate young man had given his own statement of what had occurred. I settled myself down in the corner of the carriage and read it very carefully. It ran in this way:\
\
"Mr. James McCarthy, the only son of the deceased, was then called and gave evidence as follows: 'I had been away from home for three days at Bristol, and had only just returned upon the morning of last Monday, the 3rd. My father was absent from home at the time of my arrival, and I was informed by the maid that he had driven over to Ross with John Cobb, the groom. Shortly after my return I heard the wheels of his trap in the yard, and, looking out of my window, I saw him get out and walk rapidly out of the yard, though I was not aware in which direction he was going. I then took my gun and strolled out in the direction of the Boscombe Pool, with the intention of visiting the rabbit warren which is upon the other side. On my way I saw William Crowder, the game-keeper, as he had stated in his evidence; but he is mistaken in thinking that I was following my father. I had no idea that he was in front of me. When about a hundred yards from the pool I heard a cry of "Cooee!" which was a usual signal between my father and myself. I then hurried forward, and found him standing by the pool. He appeared to be much surprised at seeing me and asked me rather roughly what I was doing there. A conversation ensued which led to high words and almost to blows, for my father was a man of a very violent temper. Seeing that his passion was becoming ungovernable, I left him and returned towards Hatherley Farm. I had not gone more than 150 yards, however, when I heard a hideous outcry behind me, which caused me to run back again. I found my father expiring upon the ground, with his head terribly injured. I dropped my gun and held him in my arms, but he almost instantly expired. I knelt beside him for some minutes, and then made my way to Mr. Turner's lodge-keeper, his house being the nearest, to ask for assistance. I saw no one near my father when I returned, and I have no idea how he came by his injuries. He was not a popular man, being somewhat cold and forbidding in his manners, but he had, as far as I know, no active enemies. I know nothing further of the matter.'\
\
"The Coroner: Did your father make any statement to you before he died?\
\
"Witness: He mumbled a few words, but I could only catch some allusion to a rat.\
\
"The Coroner: What did you understand by that?\
\
"Witness: It conveyed no meaning to me. I thought that he was delirious.\
\
"The Coroner: What was the point upon which you and your father had this final quarrel?\
\
"Witness: I should prefer not to answer.\
\
"The Coroner: I am afraid that I must press it.\
\
"Witness: It is really impossible for me to tell you. I can assure you that it has nothing to do with the sad tragedy which followed.\
\
"The Coroner: That is for the court to decide. I need not point out to you that your refusal to answer will prejudice your case considerably in any future proceedings which may arise.\
\
"Witness: I must still refuse.\
\
"The Coroner: I understand that the cry of 'Cooee' was a common signal between you and your father?\
\
"Witness: It was.\
\
"The Coroner: How was it, then, that he uttered it before he saw you, and before he even knew that you had returned from Bristol?\
\
"Witness (with considerable confusion): I do not know.\
\
"A Juryman: Did you see nothing which aroused your suspicions when you returned on hearing the cry and found your father fatally injured?\
\
"Witness: Nothing definite.\
\
"The Coroner: What do you mean?\
\
"Witness: I was so disturbed and excited as I rushed out into the open, that I could think of nothing except of my father. Yet I have a vague impression that as I ran forward something lay upon the ground to the left of me. It seemed to me to be something grey in colour, a coat of some sort, or a plaid perhaps. When I rose from my father I looked round for it, but it was gone.\
\
" 'Do you mean that it disappeared before you went for help?'\
\
" 'Yes, it was gone.'\
\
" 'You cannot say what it was?'\
\
" 'No, I had a feeling something was there.'\
\
" 'How far from the body?'\
\
" 'A dozen yards or so.'\
\
" 'And how far from the edge of the wood?'\
\
" 'About the same.'\
\
" 'Then if it was removed it was while you were within a dozen yards of it?'\
\
" 'Yes, but with my back towards it.'\
\
"This concluded the examination of the witness."\
\
"I see," said I as I glanced down the column, "that the coroner in his concluding remarks was rather severe upon young McCarthy. He calls attention, and with reason, to the discrepancy about his father having signalled to him before seeing him, also to his refusal to give details of his conversation with his father, and his singular account of his father's dying words. They are all, as he remarks, very much against the son."\
\
Holmes laughed softly to himself and stretched himself out upon the cushioned seat. "Both you and the coroner have been at some pains," said he, "to single out the very strongest points in the young man's favour. Don't you see that you alternately give him credit for having too much imagination and too little? Too little, if he could not invent a cause of quarrel which would give him the sympathy of the jury; too much, if he evolved from his own inner consciousness anything so outre as a dying reference to a rat, and the incident of the vanishing cloth. No, sir, I shall approach this case from the point of view that what this young man says is true, and we shall see whither that hypothesis will lead us. And now here is my pocket Petrarch, and not another word shall I say of this case until we are on the scene of action. We lunch at Swindon, and I see that we shall be there in twenty minutes."\
\
It was nearly four o'clock when we at last, after passing through the beautiful Stroud Valley, and over the broad gleaming Severn, found ourselves at the pretty little country-town of Ross. A lean, ferret-like man, furtive and sly-looking, was waiting for us upon the platform. In spite of the light brown dustcoat and leather-leggings which he wore in deference to his rustic surroundings, I had no difficulty in recognising Lestrade, of Scotland Yard. With him we drove to the Hereford Arms where a room had already been engaged for us.\
\
"I have ordered a carriage," said Lestrade as we sat over a cup of tea. "I knew your energetic nature, and that you would not be happy until you had been on the scene of the crime."\
\
"It was very nice and complimentary of you," Holmes answered. "It is entirely a question of barometric pressure."\
\
Lestrade looked startled. "I do not quite follow," he said.\
\
"How is the glass? Twenty-nine, I see. No wind, and not a cloud in the sky. I have a caseful of cigarettes here which need smoking, and the sofa is very much superior to the usual country hotel abomination. I do not think that it is probable that I shall use the carriage to-night."\
\
Lestrade laughed indulgently. "You have, no doubt, already formed your conclusions from the newspapers," he said. "The case is as plain as a pikestaff, and the more one goes into it the plainer it becomes. Still, of course, one can't refuse a lady, and such a very positive one, too. She has heard of you, and would have your opinion, though I repeatedly told her that there was nothing which you could do which I had not already done. Why, bless my soul! here is her carriage at the door."\
\
He had hardly spoken before there rushed into the room one of the most lovely young women that I have ever seen in my life. Her violet eyes shining, her lips parted, a pink flush upon her cheeks, all thought of her natural reserve lost in her overpowering excitement and concern.\
\
"Oh, Mr. Sherlock Holmes!" she cried, glancing from one to the other of us, and finally, with a woman's quick intuition, fastening upon my companion, "I am so glad that you have come. I have driven down to tell you so. I know that James didn't do it. I know it, and I want you to start upon your work knowing it, too. Never let yourself doubt upon that point. We have known each other since we were little children, and I know his faults as no one else does; but he is too tender-hearted to hurt a fly. Such a charge is absurd to anyone who really knows him."\
\
"I hope we may clear him, Miss Turner," said Sherlock Holmes. "You may rely upon my doing all that I can."\
\
"But you have read the evidence. You have formed some conclusion? Do you not see some loophole, some flaw? Do you not yourself think that he is innocent?"\
\
"I think that it is very probable."\
\
"There, now!" she cried, throwing back her head and looking defiantly at Lestrade. "You hear! He gives me hopes."\
\
Lestrade shrugged his shoulders. "I am afraid that my colleague has been a little quick in forming his conclusions," he said.\
\
"But he is right. Oh! I know that he is right. James never did it. And about his quarrel with his father, I am sure that the reason why he would not speak about it to the coroner was because I was concerned in it."\
\
"In what way?" asked Holmes.\
\
"It is no time for me to hide anything. James and his father had many disagreements about me. Mr. McCarthy was very anxious that there should be a marriage between us. James and I have always loved each other as brother and sister; but of course he is young and has seen very little of life yet, and--and--well, he naturally did not wish to do anything like that yet. So there were quarrels, and this, I am sure, was one of them."\
\
"And your father?" asked Holmes. "Was he in favour of such a union?"\
\
"No, he was averse to it also. No one but Mr. McCarthy was in favour of it." A quick blush passed over her fresh young face as Holmes shot one of his keen, questioning glances at her.\
\
"Thank you for this information," said he. "May I see your father if I call to-morrow?"\
\
"I am afraid the doctor won't allow it."\
\
"The doctor?"\
\
"Yes, have you not heard? Poor father has never been strong for years back, but this has broken him down completely. He has taken to his bed, and Dr. Willows says that he is a wreck and that his nervous system is shattered. Mr. McCarthy was the only man alive who had known dad in the old days in Victoria."\
\
"Ha! In Victoria! That is important."\
\
"Yes, at the mines."\
\
"Quite so; at the gold-mines, where, as I understand, Mr. Turner made his money."\
\
"Yes, certainly."\
\
"Thank you, Miss Turner. You have been of material assistance to me."\
\
"You will tell me if you have any news to-morrow. No doubt you will go to the prison to see James. Oh, if you do, Mr. Holmes, do tell him that I know him to be innocent."\
\
"I will, Miss Turner."\
\
"I must go home now, for dad is very ill, and he misses me so if I leave him. Good-bye, and God help you in your undertaking." She hurried from the room as impulsively as she had entered, and we heard the wheels of her carriage rattle off down the street.\
\
"I am ashamed of you, Holmes," said Lestrade with dignity after a few minutes' silence. "Why should you raise up hopes which you are bound to disappoint? I am not over-tender of heart, but I call it cruel."\
\
"I think that I see my way to clearing James McCarthy," said Holmes. "Have you an order to see him in prison?"\
\
"Yes, but only for you and me."\
\
"Then I shall reconsider my resolution about going out. We have still time to take a train to Hereford and see him to-night?"\
\
"Ample."\
\
"Then let us do so. Watson, I fear that you will find it very slow, but I shall only be away a couple of hours."\
\
I walked down to the station with them, and then wandered through the streets of the little town, finally returning to the hotel, where I lay upon the sofa and tried to interest myself in a yellow-backed novel. The puny plot of the story was so thin, however, when compared to the deep mystery through which we were groping, and I found my attention wander so continually from the action to the fact, that I at last flung it across the room and gave myself up entirely to a consideration of the events of the day. Supposing that this unhappy young man's story were absolutely true, then what hellish thing, what absolutely unforeseen and extraordinary calamity could have occurred between the time when he parted from his father, and the moment when, drawn back by his screams, he rushed into the glade? It was something terrible and deadly. What could it be? Might not the nature of the injuries reveal something to my medical instincts? I rang the bell and called for the weekly county paper, which contained a verbatim account of the inquest. In the surgeon's deposition it was stated that the posterior third of the left parietal bone and the left half of the occipital bone had been shattered by a heavy blow from a blunt weapon. I marked the spot upon my own head. Clearly such a blow must have been struck from behind. That was to some extent in favour of the accused, as when seen quarrelling he was face to face with his father. Still, it did not go for very much, for the older man might have turned his back before the blow fell. Still, it might be worth while to call Holmes' attention to it. Then there was the peculiar dying reference to a rat. What could that mean? It could not be delirium. A man dying from a sudden blow does not commonly become delirious. No, it was more likely to be an attempt to explain how he met his fate. But what could it indicate? I cudgelled my brains to find some possible explanation. And then the incident of the grey cloth seen by young McCarthy. If that were true the murderer must have dropped some part of his dress, presumably his overcoat, in his flight, and must have had the hardihood to return and to carry it away at the instant when the son was kneeling with his back turned not a dozen paces off. What a tissue of mysteries and improbabilities the whole thing was! I did not wonder at Lestrade's opinion, and yet I had so much faith in Sherlock Holmes' insight that I could not lose hope as long as every fresh fact seemed to strengthen his conviction of young McCarthy's innocence.\
\
It was late before Sherlock Holmes returned. He came back alone, for Lestrade was staying in lodgings in the town.\
\
"The glass still keeps very high," he remarked as he sat down. "It is of importance that it should not rain before we are able to go over the ground. On the other hand, a man should be at his very best and keenest for such nice work as that, and I did not wish to do it when fagged by a long journey. I have seen young McCarthy."\
\
"And what did you learn from him?"\
\
"Nothing."\
\
"Could he throw no light?"\
\
"None at all. I was inclined to think at one time that he knew who had done it and was screening him or her, but I am convinced now that he is as puzzled as everyone else. He is not a very quick-witted youth, though comely to look at and, I should think, sound at heart."\
\
"I cannot admire his taste," I remarked, "if it is indeed a fact that he was averse to a marriage with so charming a young lady as this Miss Turner."\
\
"Ah, thereby hangs a rather painful tale. This fellow is madly, insanely, in love with her, but some two years ago, when he was only a lad, and before he really knew her, for she had been away five years at a boarding-school, what does the idiot do but get into the clutches of a barmaid in Bristol and marry her at a registry office? No one knows a word of the matter, but you can imagine how maddening it must be to him to be upbraided for not doing what he would give his very eyes to do, but what he knows to be absolutely impossible. It was sheer frenzy of this sort which made him throw his hands up into the air when his father, at their last interview, was goading him on to propose to Miss Turner. On the other hand, he had no means of supporting himself, and his father, who was by all accounts a very hard man, would have thrown him over utterly had he known the truth. It was with his barmaid wife that he had spent the last three days in Bristol, and his father did not know where he was. Mark that point. It is of importance. Good has come out of evil, however, for the barmaid, finding from the papers that he is in serious trouble and likely to be hanged, has thrown him over utterly and has written to him to say that she has a husband already in the Bermuda Dockyard, so that there is really no tie between them. I think that that bit of news has consoled young McCarthy for all that he has suffered."\
\
"But if he is innocent, who has done it?"\
\
"Ah! who? I would call your attention very particularly to two points. One is that the murdered man had an appointment with someone at the pool, and that the someone could not have been his son, for his son was away, and he did not know when he would return. The second is that the murdered man was heard to cry 'Cooee!' before he knew that his son had returned. Those are the crucial points upon which the case depends. And now let us talk about George Meredith, if you please, and we shall leave all minor matters until to-morrow."\
\
There was no rain, as Holmes had foretold, and the morning broke bright and cloudless. At nine o'clock Lestrade called for us with the carriage, and we set off for Hatherley Farm and the Boscombe Pool.\
\
"There is serious news this morning," Lestrade observed. "It is said that Mr. Turner, of the Hall, is so ill that his life is despaired of."\
\
"An elderly man, I presume?" said Holmes.\
\
"About sixty; but his constitution has been shattered by his life abroad, and he has been in failing health for some time. This business has had a very bad effect upon him. He was an old friend of McCarthy's, and, I may add, a great benefactor to him, for I have learned that he gave him Hatherley Farm rent free."\
\
"Indeed! That is interesting," said Holmes.\
\
"Oh, yes! In a hundred other ways he has helped him. Everybody about here speaks of his kindness to him."\
\
"Really! Does it not strike you as a little singular that this McCarthy, who appears to have had little of his own, and to have been under such obligations to Turner, should still talk of marrying his son to Turner's daughter, who is, presumably, heiress to the estate, and that in such a very cocksure manner, as if it were merely a case of a proposal and all else would follow? It is the more strange, since we know that Turner himself was averse to the idea. The daughter told us as much. Do you not deduce something from that?"\
\
"We have got to the deductions and the inferences," said Lestrade, winking at me. "I find it hard enough to tackle facts, Holmes, without flying away after theories and fancies."\
\
"You are right," said Holmes demurely; "you do find it very hard to tackle the facts."\
\
"Anyhow, I have grasped one fact which you seem to find it difficult to get hold of," replied Lestrade with some warmth.\
\
"And that is--"\
\
"That McCarthy senior met his death from McCarthy junior and that all theories to the contrary are the merest moonshine."\
\
"Well, moonshine is a brighter thing than fog," said Holmes, laughing. "But I am very much mistaken if this is not Hatherley Farm upon the left."\
\
"Yes, that is it." It was a widespread, comfortable-looking building, two-storied, slate-roofed, with great yellow blotches of lichen upon the grey walls. The drawn blinds and the smokeless chimneys, however, gave it a stricken look, as though the weight of this horror still lay heavy upon it. We called at the door, when the maid, at Holmes' request, showed us the boots which her master wore at the time of his death, and also a pair of the son's, though not the pair which he had then had. Having measured these very carefully from seven or eight different points, Holmes desired to be led to the court-yard, from which we all followed the winding track which led to Boscombe Pool.\
\
Sherlock Holmes was transformed when he was hot upon such a scent as this. Men who had only known the quiet thinker and logician of Baker Street would have failed to recognise him. His face flushed and darkened. His brows were drawn into two hard black lines, while his eyes shone out from beneath them with a steely glitter. His face was bent downward, his shoulders bowed, his lips compressed, and the veins stood out like whipcord in his long, sinewy neck. His nostrils seemed to dilate with a purely animal lust for the chase, and his mind was so absolutely concentrated upon the matter before him that a question or remark fell unheeded upon his ears, or, at the most, only provoked a quick, impatient snarl in reply. Swiftly and silently he made his way along the track which ran through the meadows, and so by way of the woods to the Boscombe Pool. It was damp, marshy ground, as is all that district, and there were marks of many feet, both upon the path and amid the short grass which bounded it on either side. Sometimes Holmes would hurry on, sometimes stop dead, and once he made quite a little detour into the meadow. Lestrade and I walked behind him, the detective indifferent and contemptuous, while I watched my friend with the interest which sprang from the conviction that every one of his actions was directed towards a definite end.\
\
The Boscombe Pool, which is a little reed-girt sheet of water some fifty yards across, is situated at the boundary between the Hatherley Farm and the private park of the wealthy Mr. Turner. Above the woods which lined it upon the farther side we could see the red, jutting pinnacles which marked the site of the rich landowner's dwelling. On the Hatherley side of the pool the woods grew very thick, and there was a narrow belt of sodden grass twenty paces across between the edge of the trees and the reeds which lined the lake. Lestrade showed us the exact spot at which the body had been found, and, indeed, so moist was the ground, that I could plainly see the traces which had been left by the fall of the stricken man. To Holmes, as I could see by his eager face and peering eyes, very many other things were to be read upon the trampled grass. He ran round, like a dog who is picking up a scent, and then turned upon my companion.\
\
"What did you go into the pool for?" he asked.\
\
"I fished about with a rake. I thought there might be some weapon or other trace. But how on earth--"\
\
"Oh, tut, tut! I have no time! That left foot of yours with its inward twist is all over the place. A mole could trace it, and there it vanishes among the reeds. Oh, how simple it would all have been had I been here before they came like a herd of buffalo and wallowed all over it. Here is where the party with the lodge-keeper came, and they have covered all tracks for six or eight feet round the body. But here are three separate tracks of the same feet." He drew out a lens and lay down upon his waterproof to have a better view, talking all the time rather to himself than to us. "These are young McCarthy's feet. Twice he was walking, and once he ran swiftly, so that the soles are deeply marked and the heels hardly visible. That bears out his story. He ran when he saw his father on the ground. Then here are the father's feet as he paced up and down. What is this, then? It is the butt-end of the gun as the son stood listening. And this? Ha, ha! What have we here? Tiptoes! tiptoes! Square, too, quite unusual boots! They come, they go, they come again--of course that was for the cloak. Now where did they come from?" He ran up and down, sometimes losing, sometimes finding the track until we were well within the edge of the wood and under the shadow of a great beech, the largest tree in the neighbourhood. Holmes traced his way to the farther side of this and lay down once more upon his face with a little cry of satisfaction. For a long time he remained there, turning over the leaves and dried sticks, gathering up what seemed to me to be dust into an envelope and examining with his lens not only the ground but even the bark of the tree as far as he could reach. A jagged stone was lying among the moss, and this also he carefully examined and retained. Then he followed a pathway through the wood until he came to the highroad, where all traces were lost.\
\
"It has been a case of considerable interest," he remarked, returning to his natural manner. "I fancy that this grey house on the right must be the lodge. I think that I will go in and have a word with Moran, and perhaps write a little note. Having done that, we may drive back to our luncheon. You may walk to the cab, and I shall be with you presently."\
\
It was about ten minutes before we regained our cab and drove back into Ross, Holmes still carrying with him the stone which he had picked up in the wood.\
\
"This may interest you, Lestrade," he remarked, holding it out. "The murder was done with it."\
\
"I see no marks."\
\
"There are none."\
\
"How do you know, then?"\
\
"The grass was growing under it. It had only lain there a few days. There was no sign of a place whence it had been taken. It corresponds with the injuries. There is no sign of any other weapon."\
\
"And the murderer?"\
\
"Is a tall man, left-handed, limps with the right leg, wears thick-soled shooting-boots and a grey cloak, smokes Indian cigars, uses a cigar-holder, and carries a blunt pen-knife in his pocket. There are several other indications, but these may be enough to aid us in our search."\
\
Lestrade laughed. "I am afraid that I am still a sceptic," he said. "Theories are all very well, but we have to deal with a hard-headed British jury."\
\
"Nous verrons," answered Holmes calmly. "You work your own method, and I shall work mine. I shall be busy this afternoon, and shall probably return to London by the evening train."\
\
"And leave your case unfinished?"\
\
"No, finished."\
\
"But the mystery?"\
\
"It is solved."\
\
"Who was the criminal, then?"\
\
"The gentleman I describe."\
\
"But who is he?"\
\
"Surely it would not be difficult to find out. This is not such a populous neighbourhood."\
\
Lestrade shrugged his shoulders. "I am a practical man," he said, "and I really cannot undertake to go about the country looking for a left-handed gentleman with a game leg. I should become the laughing-stock of Scotland Yard."\
\
"All right," said Holmes quietly. "I have given you the chance. Here are your lodgings. Good-bye. I shall drop you a line before I leave."\
\
Having left Lestrade at his rooms, we drove to our hotel, where we found lunch upon the table. Holmes was silent and buried in thought with a pained expression upon his face, as one who finds himself in a perplexing position.\
\
"Look here, Watson," he said when the cloth was cleared "just sit down in this chair and let me preach to you for a little. I don't know quite what to do, and I should value your advice. Light a cigar and let me expound."\
\
"Pray do so."\
\
"Well, now, in considering this case there are two points about young McCarthy's narrative which struck us both instantly, although they impressed me in his favour and you against him. One was the fact that his father should, according to his account, cry 'Cooee!' before seeing him. The other was his singular dying reference to a rat. He mumbled several words, you understand, but that was all that caught the son's ear. Now from this double point our research must commence, and we will begin it by presuming that what the lad says is absolutely true."\
\
"What of this 'Cooee!' then?"\
\
"Well, obviously it could not have been meant for the son. The son, as far as he knew, was in Bristol. It was mere chance that he was within earshot. The 'Cooee!' was meant to attract the attention of whoever it was that he had the appointment with. But 'Cooee' is a distinctly Australian cry, and one which is used between Australians. There is a strong presumption that the person whom McCarthy expected to meet him at Boscombe Pool was someone who had been in Australia."\
\
"What of the rat, then?"\
\
Sherlock Holmes took a folded paper from his pocket and flattened it out on the table. "This is a map of the Colony of Victoria," he said. "I wired to Bristol for it last night." He put his hand over part of the map. "What do you read?"\
\
"ARAT," I read.\
\
"And now?" He raised his hand.\
\
"BALLARAT."\
\
"Quite so. That was the word the man uttered, and of which his son only caught the last two syllables. He was trying to utter the name of his murderer. So and so, of Ballarat."\
\
"It is wonderful!" I exclaimed.\
\
"It is obvious. And now, you see, I had narrowed the field down considerably. The possession of a grey garment was a third point which, granting the son's statement to be correct, was a certainty. We have come now out of mere vagueness to the definite conception of an Australian from Ballarat with a grey cloak."\
\
"Certainly."\
\
"And one who was at home in the district, for the pool can only be approached by the farm or by the estate, where strangers could hardly wander."\
\
"Quite so."\
\
"Then comes our expedition of to-day. By an examination of the ground I gained the trifling details which I gave to that imbecile Lestrade, as to the personality of the criminal."\
\
"But how did you gain them?"\
\
"You know my method. It is founded upon the observation of trifles."\
\
"His height I know that you might roughly judge from the length of his stride. His boots, too, might be told from their traces."\
\
"Yes, they were peculiar boots."\
\
"But his lameness?"\
\
"The impression of his right foot was always less distinct than his left. He put less weight upon it. Why? Because he limped--he was lame."\
\
"But his left-handedness."\
\
"You were yourself struck by the nature of the injury as recorded by the surgeon at the inquest. The blow was struck from immediately behind, and yet was upon the left side. Now, how can that be unless it were by a left-handed man? He had stood behind that tree during the interview between the father and son. He had even smoked there. I found the ash of a cigar, which my special knowledge of tobacco ashes enables me to pronounce as an Indian cigar. I have, as you know, devoted some attention to this, and written a little monograph on the ashes of 140 different varieties of pipe, cigar, and cigarette tobacco. Having found the ash, I then looked round and discovered the stump among the moss where he had tossed it. It was an Indian cigar, of the variety which are rolled in Rotterdam."\
\
"And the cigar-holder?"\
\
"I could see that the end had not been in his mouth. Therefore he used a holder. The tip had been cut off, not bitten off, but the cut was not a clean one, so I deduced a blunt pen-knife."\
\
"Holmes," I said, "you have drawn a net round this man from which he cannot escape, and you have saved an innocent human life as truly as if you had cut the cord which was hanging him. I see the direction in which all this points. The culprit is--"\
\
"Mr. John Turner," cried the hotel waiter, opening the door of our sitting-room, and ushering in a visitor.\
\
The man who entered was a strange and impressive figure. His slow, limping step and bowed shoulders gave the appearance of decrepitude, and yet his hard, deep-lined, craggy features, and his enormous limbs showed that he was possessed of unusual strength of body and of character. His tangled beard, grizzled hair, and outstanding, drooping eyebrows combined to give an air of dignity and power to his appearance, but his face was of an ashen white, while his lips and the corners of his nostrils were tinged with a shade of blue. It was clear to me at a glance that he was in the grip of some deadly and chronic disease.\
\
"Pray sit down on the sofa," said Holmes gently. "You had my note?"\
\
"Yes, the lodge-keeper brought it up. You said that you wished to see me here to avoid scandal."\
\
"I thought people would talk if I went to the Hall."\
\
"And why did you wish to see me?" He looked across at my companion with despair in his weary eyes, as though his question was already answered.\
\
"Yes," said Holmes, answering the look rather than the words. "It is so. I know all about McCarthy."\
\
The old man sank his face in his hands. "God help me!" he cried. "But I would not have let the young man come to harm. I give you my word that I would have spoken out if it went against him at the Assizes."\
\
"I am glad to hear you say so," said Holmes gravely.\
\
"I would have spoken now had it not been for my dear girl. It would break her heart--it will break her heart when she hears that I am arrested."\
\
"It may not come to that," said Holmes.\
\
"What?"\
\
"I am no official agent. I understand that it was your daughter who required my presence here, and I am acting in her interests. Young McCarthy must be got off, however."\
\
"I am a dying man," said old Turner. "I have had diabetes for years. My doctor says it is a question whether I shall live a month. Yet I would rather die under my own roof than in a gaol."\
\
Holmes rose and sat down at the table with his pen in his hand and a bundle of paper before him. "Just tell us the truth," he said. "I shall jot down the facts. You will sign it, and Watson here can witness it. Then I could produce your confession at the last extremity to save young McCarthy. I promise you that I shall not use it unless it is absolutely needed."\
\
"It's as well," said the old man; "it's a question whether I shall live to the Assizes, so it matters little to me, but I should wish to spare Alice the shock. And now I will make the thing clear to you; it has been a long time in the acting, but will not take me long to tell.\
\
"You didn't know this dead man, McCarthy. He was a devil incarnate. I tell you that. God keep you out of the clutches of such a man as he. His grip has been upon me these twenty years, and he has blasted my life. I'll tell you first how I came to be in his power.\
\
"It was in the early '60's at the diggings. I was a young chap then, hot-blooded and reckless, ready to turn my hand at anything; I got among bad companions, took to drink, had no luck with my claim, took to the bush, and in a word became what you would call over here a highway robber. There were six of us, and we had a wild, free life of it, sticking up a station from time to time, or stopping the wagons on the road to the diggings. Black Jack of Ballarat was the name I went under, and our party is still remembered in the colony as the Ballarat Gang.\
\
"One day a gold convoy came down from Ballarat to Melbourne, and we lay in wait for it and attacked it. There were six troopers and six of us, so it was a close thing, but we emptied four of their saddles at the first volley. Three of our boys were killed, however, before we got the swag. I put my pistol to the head of the wagon-driver, who was this very man McCarthy. I wish to the Lord that I had shot him then, but I spared him, though I saw his wicked little eyes fixed on my face, as though to remember every feature. We got away with the gold, became wealthy men, and made our way over to England without being suspected. There I parted from my old pals and determined to settle down to a quiet and respectable life. I bought this estate, which chanced to be in the market, and I set myself to do a little good with my money, to make up for the way in which I had earned it. I married, too, and though my wife died young she left me my dear little Alice. Even when she was just a baby her wee hand seemed to lead me down the right path as nothing else had ever done. In a word, I turned over a new leaf and did my best to make up for the past. All was going well when McCarthy laid his grip upon me.\
\
"I had gone up to town about an investment, and I met him in Regent Street with hardly a coat to his back or a boot to his foot.\
\
" 'Here we are, Jack,' says he, touching me on the arm; 'we'll be as good as a family to you. There's two of us, me and my son, and you can have the keeping of us. If you don't--it's a fine, law-abiding country is England, and there's always a policeman within hail.'\
\
"Well, down they came to the west country, there was no shaking them off, and there they have lived rent free on my best land ever since. There was no rest for me, no peace, no forgetfulness; turn where I would, there was his cunning, grinning face at my elbow. It grew worse as Alice grew up, for he soon saw I was more afraid of her knowing my past than of the police. Whatever he wanted he must have, and whatever it was I gave him without question, land, money, houses, until at last he asked a thing which I could not give. He asked for Alice.\
\
"His son, you see, had grown up, and so had my girl, and as I was known to be in weak health, it seemed a fine stroke to him that his lad should step into the whole property. But there I was firm. I would not have his cursed stock mixed with mine; not that I had any dislike to the lad, but his blood was in him, and that was enough. I stood firm. McCarthy threatened. I braved him to do his worst. We were to meet at the pool midway between our houses to talk it over.\
\
"When I went down there I found him talking with his son, so I smoked a cigar and waited behind a tree until he should be alone. But as I listened to his talk all that was black and bitter in me seemed to come uppermost. He was urging his son to marry my daughter with as little regard for what she might think as if she were a slut from off the streets. It drove me mad to think that I and all that I held most dear should be in the power of such a man as this. Could I not snap the bond? I was already a dying and a desperate man. Though clear of mind and fairly strong of limb, I knew that my own fate was sealed. But my memory and my girl! Both could be saved if I could but silence that foul tongue. I did it, Mr. Holmes. I would do it again. Deeply as I have sinned, I have led a life of martyrdom to atone for it. But that my girl should be entangled in the same meshes which held me was more than I could suffer. I struck him down with no more compunction than if he had been some foul and venomous beast. His cry brought back his son; but I had gained the cover of the wood, though I was forced to go back to fetch the cloak which I had dropped in my flight. That is the true story, gentlemen, of all that occurred."\
\
"Well, it is not for me to judge you," said Holmes as the old man signed the statement which had been drawn out. "I pray that we may never be exposed to such a temptation."\
\
"I pray not, sir. And what do you intend to do?"\
\
"In view of your health, nothing. You are yourself aware that you will soon have to answer for your deed at a higher court than the Assizes. I will keep your confession, and if McCarthy is condemned I shall be forced to use it. If not, it shall never be seen by mortal eye; and your secret, whether you be alive or dead, shall be safe with us."\
\
"Farewell, then," said the old man solemnly. "Your own deathbeds, when they come, will be the easier for the thought of the peace which you have given to mine." Tottering and shaking in all his giant frame, he stumbled slowly from the room.\
\
"God help us!" said Holmes after a long silence. "Why does fate play such tricks with poor, helpless worms? I never hear of such a case as this that I do not think of Baxter's words, and say, 'There, but for the grace of God, goes Sherlock Holmes.' "\
\
James McCarthy was acquitted at the Assizes on the strength of a number of objections which had been drawn out by Holmes and submitted to the defending counsel. Old Turner lived for seven months after our interview, but he is now dead; and there is every prospect that the son and daughter may come to live happily together in ignorance of the black cloud which rests upon their past.\
\
ADVENTURE  V.  THE FIVE ORANGE PIPS\
\
\
When I glance over my notes and records of the Sherlock Holmes cases between the years '82 and '90, I am faced by so many which present strange and interesting features that it is no easy matter to know which to choose and which to leave. Some, however, have already gained publicity through the papers, and others have not offered a field for those peculiar qualities which my friend possessed in so high a degree, and which it is the object of these papers to illustrate. Some, too, have baffled his analytical skill, and would be, as narratives, beginnings without an ending, while others have been but partially cleared up, and have their explanations founded rather upon conjecture and surmise than on that absolute logical proof which was so dear to him. There is, however, one of these last which was so remarkable in its details and so startling in its results that I am tempted to give some account of it in spite of the fact that there are points in connection with it which never have been, and probably never will be, entirely cleared up.\
\
The year '87 furnished us with a long series of cases of greater or less interest, of which I retain the records. Among my headings under this one twelve months I find an account of the adventure of the Paradol Chamber, of the Amateur Mendicant Society, who held a luxurious club in the lower vault of a furniture warehouse, of the facts connected with the loss of the British barque Sophy Anderson, of the singular adventures of the Grice Patersons in the island of Uffa, and finally of the Camberwell poisoning case. In the latter, as may be remembered, Sherlock Holmes was able, by winding up the dead man's watch, to prove that it had been wound up two hours before, and that therefore the deceased had gone to bed within that time--a deduction which was of the greatest importance in clearing up the case. All these I may sketch out at some future date, but none of them present such singular features as the strange train of circumstances which I have now taken up my pen to describe.\
\
It was in the latter days of September, and the equinoctial gales had set in with exceptional violence. All day the wind had screamed and the rain had beaten against the windows, so that even here in the heart of great, hand-made London we were forced to raise our minds for the instant from the routine of life and to recognise the presence of those great elemental forces which shriek at mankind through the bars of his civilisation, like untamed beasts in a cage. As evening drew in, the storm grew higher and louder, and the wind cried and sobbed like a child in the chimney. Sherlock Holmes sat moodily at one side of the fireplace cross-indexing his records of crime, while I at the other was deep in one of Clark Russell's fine sea-stories until the howl of the gale from without seemed to blend with the text, and the splash of the rain to lengthen out into the long swash of the sea waves. My wife was on a visit to her mother's, and for a few days I was a dweller once more in my old quarters at Baker Street.\
\
"Why," said I, glancing up at my companion, "that was surely the bell. Who could come to-night? Some friend of yours, perhaps?"\
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"Except yourself I have none," he answered. "I do not encourage visitors."\
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"A client, then?"\
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"If so, it is a serious case. Nothing less would bring a man out on such a day and at such an hour. But I take it that it is more likely to be some crony of the landlady's."\
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Sherlock Holmes was wrong in his conjecture, however, for there came a step in the passage and a tapping at the door. He stretched out his long arm to turn the lamp away from himself and towards the vacant chair upon which a newcomer must sit.\
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"Come in!" said he.\
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The man who entered was young, some two-and-twenty at the outside, well-groomed and trimly clad, with something of refinement and delicacy in his bearing. The streaming umbrella which he held in his hand, and his long shining waterproof told of the fierce weather through which he had come. He looked about him anxiously in the glare of the lamp, and I could see that his face was pale and his eyes heavy, like those of a man who is weighed down with some great anxiety.\
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"I owe you an apology," he said, raising his golden pince-nez to his eyes. "I trust that I am not intruding. I fear that I have brought some traces of the storm and rain into your snug chamber."\
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"Give me your coat and umbrella," said Holmes. "They may rest here on the hook and will be dry presently. You have come up from the south-west, I see."\
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"Yes, from Horsham."\
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"That clay and chalk mixture which I see upon your toe caps is quite distinctive."\
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"I have come for advice."\
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"That is easily got."\
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"And help."\
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"That is not always so easy."\
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"I have heard of you, Mr. Holmes. I heard from Major Prendergast how you saved him in the Tankerville Club scandal."\
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"Ah, of course. He was wrongfully accused of cheating at cards."\
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"He said that you could solve anything."\
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"He said too much."\
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"That you are never beaten."\
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"I have been beaten four times--three times by men, and once by a woman."\
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"But what is that compared with the number of your successes?"\
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"It is true that I have been generally successful."\
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"Then you may be so with me."\
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"I beg that you will draw your chair up to the fire and favour me with some details as to your case."\
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"It is no ordinary one."\
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"None of those which come to me are. I am the last court of appeal."\
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"And yet I question, sir, whether, in all your experience, you have ever listened to a more mysterious and inexplicable chain of events than those which have happened in my own family."\
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"You fill me with interest," said Holmes. "Pray give us the essential facts from the commencement, and I can afterwards question you as to those details which seem to me to be most important."\
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The young man pulled his chair up and pushed his wet feet out towards the blaze.\
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"My name," said he, "is John Openshaw, but my own affairs have, as far as I can understand, little to do with this awful business. It is a hereditary matter; so in order to give you an idea of the facts, I must go back to the commencement of the affair.\
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"You must know that my grandfather had two sons--my uncle Elias and my father Joseph. My father had a small factory at Coventry, which he enlarged at the time of the invention of bicycling. He was a patentee of the Openshaw unbreakable tire, and his business met with such success that he was able to sell it and to retire upon a handsome competence.\
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"My uncle Elias emigrated to America when he was a young man and became a planter in Florida, where he was reported to have done very well. At the time of the war he fought in Jackson's army, and afterwards under Hood, where he rose to be a colonel. When Lee laid down his arms my uncle returned to his plantation, where he remained for three or four years. About 1869 or 1870 he came back to Europe and took a small estate in Sussex, near Horsham. He had made a very considerable fortune in the States, and his reason for leaving them was his aversion to the negroes, and his dislike of the Republican policy in extending the franchise to them. He was a singular man, fierce and quick-tempered, very foul-mouthed when he was angry, and of a most retiring disposition. During all the years that he lived at Horsham, I doubt if ever he set foot in the town. He had a garden and two or three fields round his house, and there he would take his exercise, though very often for weeks on end he would never leave his room. He drank a great deal of brandy and smoked very heavily, but he would see no society and did not want any friends, not even his own brother.\
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"He didn't mind me; in fact, he took a fancy to me, for at the time when he saw me first I was a youngster of twelve or so. This would be in the year 1878, after he had been eight or nine years in England. He begged my father to let me live with him and he was very kind to me in his way. When he was sober he used to be fond of playing backgammon and draughts with me, and he would make me his representative both with the servants and with the tradespeople, so that by the time that I was sixteen I was quite master of the house. I kept all the keys and could go where I liked and do what I liked, so long as I did not disturb him in his privacy. There was one singular exception, however, for he had a single room, a lumber-room up among the attics, which was invariably locked, and which he would never permit either me or anyone else to enter. With a boy's curiosity I have peeped through the keyhole, but I was never able to see more than such a collection of old trunks and bundles as would be expected in such a room.\
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"One day--it was in March, 1883--a letter with a foreign stamp lay upon the table in front of the colonel's plate. It was not a common thing for him to receive letters, for his bills were all paid in ready money, and he had no friends of any sort. 'From India!' said he as he took it up, 'Pondicherry postmark! What can this be?' Opening it hurriedly, out there jumped five little dried orange pips, which pattered down upon his plate. I began to laugh at this, but the laugh was struck from my lips at the sight of his face. His lip had fallen, his eyes were protruding, his skin the colour of putty, and he glared at the envelope which he still held in his trembling hand, 'K. K. K.!' he shrieked, and then, 'My God, my God, my sins have overtaken me!'\
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" 'What is it, uncle?' I cried.\
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" 'Death,' said he, and rising from the table he retired to his room, leaving me palpitating with horror. I took up the envelope and saw scrawled in red ink upon the inner flap, just above the gum, the letter K three times repeated. There was nothing else save the five dried pips. What could be the reason of his overpowering terror? I left the breakfast-table, and as I ascended the stair I met him coming down with an old rusty key, which must have belonged to the attic, in one hand, and a small brass box, like a cashbox, in the other.\
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" 'They may do what they like, but I'll checkmate them still,' said he with an oath. 'Tell Mary that I shall want a fire in my room to-day, and send down to Fordham, the Horsham lawyer.'\
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"I did as he ordered, and when the lawyer arrived I was asked to step up to the room. The fire was burning brightly, and in the grate there was a mass of black, fluffy ashes, as of burned paper, while the brass box stood open and empty beside it. As I glanced at the box I noticed, with a start, that upon the lid was printed the treble K which I had read in the morning upon the envelope.\
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" 'I wish you, John,' said my uncle, 'to witness my will. I leave my estate, with all its advantages and all its disadvantages, to my brother, your father, whence it will, no doubt, descend to you. If you can enjoy it in peace, well and good! If you find you cannot, take my advice, my boy, and leave it to your deadliest enemy. I am sorry to give you such a two-edged thing, but I can't say what turn things are going to take. Kindly sign the paper where Mr. Fordham shows you.'\
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"I signed the paper as directed, and the lawyer took it away with him. The singular incident made, as you may think, the deepest impression upon me, and I pondered over it and turned it every way in my mind without being able to make anything of it. Yet I could not shake off the vague feeling of dread which it left behind, though the sensation grew less keen as the weeks passed and nothing happened to disturb the usual routine of our lives. I could see a change in my uncle, however. He drank more than ever, and he was less inclined for any sort of society. Most of his time he would spend in his room, with the door locked upon the inside, but sometimes he would emerge in a sort of drunken frenzy and would burst out of the house and tear about the garden with a revolver in his hand, screaming out that he was afraid of no man, and that he was not to be cooped up, like a sheep in a pen, by man or devil. When these hot fits were over, however, he would rush tumultuously in at the door and lock and bar it behind him, like a man who can brazen it out no longer against the terror which lies at the roots of his soul. At such times I have seen his face, even on a cold day, glisten with moisture, as though it were new raised from a basin.\
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"Well, to come to an end of the matter, Mr. Holmes, and not to abuse your patience, there came a night when he made one of those drunken sallies from which he never came back. We found him, when we went to search for him, face downward in a little green-scummed pool, which lay at the foot of the garden. There was no sign of any violence, and the water was but two feet deep, so that the jury, having regard to his known eccentricity, brought in a verdict of 'suicide.' But I, who knew how he winced from the very thought of death, had much ado to persuade myself that he had gone out of his way to meet it. The matter passed, however, and my father entered into possession of the estate, and of some $14,000, which lay to his credit at the bank."\
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"One moment," Holmes interposed, "your statement is, I foresee, one of the most remarkable to which I have ever listened. Let me have the date of the reception by your uncle of the letter, and the date of his supposed suicide."\
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"The letter arrived on March 10, 1883. His death was seven weeks later, upon the night of May 2nd."\
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"Thank you. Pray proceed."\
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"When my father took over the Horsham property, he, at my request, made a careful examination of the attic, which had been always locked up. We found the brass box there, although its contents had been destroyed. On the inside of the cover was a paper label, with the initials of K. K. K. repeated upon it, and 'Letters, memoranda, receipts, and a register' written beneath. These, we presume, indicated the nature of the papers which had been destroyed by Colonel Openshaw. For the rest, there was nothing of much importance in the attic save a great many scattered papers and note-books bearing upon my uncle's life in America. Some of them were of the war time and showed that he had done his duty well and had borne the repute of a brave soldier. Others were of a date during the reconstruction of the Southern states, and were mostly concerned with politics, for he had evidently taken a strong part in opposing the carpet-bag politicians who had been sent down from the North.\
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"Well, it was the beginning of '84 when my father came to live at Horsham, and all went as well as possible with us until the January of '85. On the fourth day after the new year I heard my father give a sharp cry of surprise as we sat together at the breakfast-table. There he was, sitting with a newly opened envelope in one hand and five dried orange pips in the outstretched palm of the other one. He had always laughed at what he called my cock-and-bull story about the colonel, but he looked very scared and puzzled now that the same thing had come upon himself.\
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" 'Why, what on earth does this mean, John?' he stammered.\
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"My heart had turned to lead. 'It is K. K. K.,' said I.\
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"He looked inside the envelope. 'So it is,' he cried. 'Here are the very letters. But what is this written above them?'\
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" 'Put the papers on the sundial,' I read, peeping over his shoulder.\
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" 'What papers? What sundial?' he asked.\
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" 'The sundial in the garden. There is no other,' said I; 'but the papers must be those that are destroyed.'\
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" 'Pooh!' said he, gripping hard at his courage. 'We are in a civilised land here, and we can't have tomfoolery of this kind. Where does the thing come from?'\
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" 'From Dundee,' I answered, glancing at the postmark.\
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" 'Some preposterous practical joke,' said he. 'What have I to do with sundials and papers? I shall take no notice of such nonsense.'\
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" 'I should certainly speak to the police,' I said.\
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" 'And be laughed at for my pains. Nothing of the sort.'\
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" 'Then let me do so?'\
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" 'No, I forbid you. I won't have a fuss made about such nonsense.'\
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"It was in vain to argue with him, for he was a very obstinate man. I went about, however, with a heart which was full of forebodings.\
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"On the third day after the coming of the letter my father went from home to visit an old friend of his, Major Freebody, who is in command of one of the forts upon Portsdown Hill. I was glad that he should go, for it seemed to me that he was farther from danger when he was away from home. In that, however, I was in error. Upon the second day of his absence I received a telegram from the major, imploring me to come at once. My father had fallen over one of the deep chalk-pits which abound in the neighbourhood, and was lying senseless, with a shattered skull. I hurried to him, but he passed away without having ever recovered his consciousness. He had, as it appears, been returning from Fareham in the twilight, and as the country was unknown to him, and the chalk-pit unfenced, the jury had no hesitation in bringing in a verdict of 'death from accidental causes.' Carefully as I examined every fact connected with his death, I was unable to find anything which could suggest the idea of murder. There were no signs of violence, no footmarks, no robbery, no record of strangers having been seen upon the roads. And yet I need not tell you that my mind was far from at ease, and that I was well-nigh certain that some foul plot had been woven round him.\
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"In this sinister way I came into my inheritance. You will ask me why I did not dispose of it? I answer, because I was well convinced that our troubles were in some way dependent upon an incident in my uncle's life, and that the danger would be as pressing in one house as in another.\
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"It was in January, '85, that my poor father met his end, and two years and eight months have elapsed since then. During that time I have lived happily at Horsham, and I had begun to hope that this curse had passed away from the family, and that it had ended with the last generation. I had begun to take comfort too soon, however; yesterday morning the blow fell in the very shape in which it had come upon my father."\
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The young man took from his waistcoat a crumpled envelope, and turning to the table he shook out upon it five little dried orange pips.\
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"This is the envelope," he continued. "The postmark is London--eastern division. Within are the very words which were upon my father's last message: 'K. K. K.'; and then 'Put the papers on the sundial.' "\
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"What have you done?" asked Holmes.\
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"Nothing."\
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"Nothing?"\
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"To tell the truth"--he sank his face into his thin, white hands--"I have felt helpless. I have felt like one of those poor rabbits when the snake is writhing towards it. I seem to be in the grasp of some resistless, inexorable evil, which no foresight and no precautions can guard against."\
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"Tut! tut!" cried Sherlock Holmes. "You must act, man, or you are lost. Nothing but energy can save you. This is no time for despair."\
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"I have seen the police."\
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"Ah!"\
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"But they listened to my story with a smile. I am convinced that the inspector has formed the opinion that the letters are all practical jokes, and that the deaths of my relations were really accidents, as the jury stated, and were not to be connected with the warnings."\
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Holmes shook his clenched hands in the air. "Incredible imbecility!" he cried.\
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"They have, however, allowed me a policeman, who may remain in the house with me."\
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"Has he come with you to-night?"\
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"No. His orders were to stay in the house."\
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Again Holmes raved in the air.\
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"Why did you come to me," he cried, "and, above all, why did you not come at once?"\
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"I did not know. It was only to-day that I spoke to Major Prendergast about my troubles and was advised by him to come to you."\
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"It is really two days since you had the letter. We should have acted before this. You have no further evidence, I suppose, than that which you have placed before us--no suggestive detail which might help us?"\
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"There is one thing," said John Openshaw. He rummaged in his coat pocket, and, drawing out a piece of discoloured, blue-tinted paper, he laid it out upon the table. "I have some remembrance," said he, "that on the day when my uncle burned the papers I observed that the small, unburned margins which lay amid the ashes were of this particular colour. I found this single sheet upon the floor of his room, and I am inclined to think that it may be one of the papers which has, perhaps, fluttered out from among the others, and in that way has escaped destruction. Beyond the mention of pips, I do not see that it helps us much. I think myself that it is a page from some private diary. The writing is undoubtedly my uncle's."\
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Holmes moved the lamp, and we both bent over the sheet of paper, which showed by its ragged edge that it had indeed been torn from a book. It was headed, "March, 1869," and beneath were the following enigmatical notices:\
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"4th. Hudson came. Same old platform.\
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"7th. Set the pips on McCauley, Paramore, and\
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        John Swain, of St. Augustine.\
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"9th. McCauley cleared.\
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"10th. John Swain cleared.\
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"12th. Visited Paramore. All well."\
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"Thank you!" said Holmes, folding up the paper and returning it to our visitor. "And now you must on no account lose another instant. We cannot spare time even to discuss what you have told me. You must get home instantly and act."\
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"What shall I do?"\
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"There is but one thing to do. It must be done at once. You must put this piece of paper which you have shown us into the brass box which you have described. You must also put in a note to say that all the other papers were burned by your uncle, and that this is the only one which remains. You must assert that in such words as will carry conviction with them. Having done this, you must at once put the box out upon the sundial, as directed. Do you understand?"\
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"Entirely."\
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"Do not think of revenge, or anything of the sort, at present. I think that we may gain that by means of the law; but we have our web to weave, while theirs is already woven. The first consideration is to remove the pressing danger which threatens you. The second is to clear up the mystery and to punish the guilty parties."\
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"I thank you," said the young man, rising and pulling on his overcoat. "You have given me fresh life and hope. I shall certainly do as you advise."\
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"Do not lose an instant. And, above all, take care of yourself in the meanwhile, for I do not think that there can be a doubt that you are threatened by a very real and imminent danger. How do you go back?"\
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"By train from Waterloo."\
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"It is not yet nine. The streets will be crowded, so I trust that you may be in safety. And yet you cannot guard yourself too closely."\
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"I am armed."\
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"That is well. To-morrow I shall set to work upon your case."\
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"I shall see you at Horsham, then?"\
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"No, your secret lies in London. It is there that I shall seek it."\
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"Then I shall call upon you in a day, or in two days, with news as to the box and the papers. I shall take your advice in every particular." He shook hands with us and took his leave. Outside the wind still screamed and the rain splashed and pattered against the windows. This strange, wild story seemed to have come to us from amid the mad elements--blown in upon us like a sheet of sea-weed in a gale--and now to have been reabsorbed by them once more.\
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Sherlock Holmes sat for some time in silence, with his head sunk forward and his eyes bent upon the red glow of the fire. Then he lit his pipe, and leaning back in his chair he watched the blue smoke-rings as they chased each other up to the ceiling.\
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"I think, Watson," he remarked at last, "that of all our cases we have had none more fantastic than this."\
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"Save, perhaps, the Sign of Four."\
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"Well, yes. Save, perhaps, that. And yet this John Openshaw seems to me to be walking amid even greater perils than did the Sholtos."\
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"But have you," I asked, "formed any definite conception as to what these perils are?"\
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"There can be no question as to their nature," he answered.\
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"Then what are they? Who is this K. K. K., and why does he pursue this unhappy family?"\
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Sherlock Holmes closed his eyes and placed his elbows upon the arms of his chair, with his finger-tips together. "The ideal reasoner," he remarked, "would, when he had once been shown a single fact in all its bearings, deduce from it not only all the chain of events which led up to it but also all the results which would follow from it. As Cuvier could correctly describe a whole animal by the contemplation of a single bone, so the observer who has thoroughly understood one link in a series of incidents should be able to accurately state all the other ones, both before and after. We have not yet grasped the results which the reason alone can attain to. Problems may be solved in the study which have baffled all those who have sought a solution by the aid of their senses. To carry the art, however, to its highest pitch, it is necessary that the reasoner should be able to utilise all the facts which have come to his knowledge; and this in itself implies, as you will readily see, a possession of all knowledge, which, even in these days of free education and encyclopaedias, is a somewhat rare accomplishment. It is not so impossible, however, that a man should possess all knowledge which is likely to be useful to him in his work, and this I have endeavoured in my case to do. If I remember rightly, you on one occasion, in the early days of our friendship, defined my limits in a very precise fashion."\
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"Yes," I answered, laughing. "It was a singular document. Philosophy, astronomy, and politics were marked at zero, I remember. Botany variable, geology profound as regards the mud-stains from any region within fifty miles of town, chemistry eccentric, anatomy unsystematic, sensational literature and crime records unique, violin-player, boxer, swordsman, lawyer, and self-poisoner by cocaine and tobacco. Those, I think, were the main points of my analysis."\
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Holmes grinned at the last item. "Well," he said, "I say now, as I said then, that a man should keep his little brain-attic stocked with all the furniture that he is likely to use, and the rest he can put away in the lumber-room of his library, where he can get it if he wants it. Now, for such a case as the one which has been submitted to us to-night, we need certainly to muster all our resources. Kindly hand me down the letter K of the American Encyclopaedia which stands upon the shelf beside you. Thank you. Now let us consider the situation and see what may be deduced from it. In the first place, we may start with a strong presumption that Colonel Openshaw had some very strong reason for leaving America. Men at his time of life do not change all their habits and exchange willingly the charming climate of Florida for the lonely life of an English provincial town. His extreme love of solitude in England suggests the idea that he was in fear of someone or something, so we may assume as a working hypothesis that it was fear of someone or something which drove him from America. As to what it was he feared, we can only deduce that by considering the formidable letters which were received by himself and his successors. Did you remark the postmarks of those letters?"\
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"The first was from Pondicherry, the second from Dundee, and the third from London."\
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"From East London. What do you deduce from that?"\
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"They are all seaports. That the writer was on board of a ship."\
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"Excellent. We have already a clue. There can be no doubt that the probability--the strong probability--is that the writer was on board of a ship. And now let us consider another point. In the case of Pondicherry, seven weeks elapsed between the threat and its fulfilment, in Dundee it was only some three or four days. Does that suggest anything?"\
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"A greater distance to travel."\
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"But the letter had also a greater distance to come."\
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"Then I do not see the point."\
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"There is at least a presumption that the vessel in which the man or men are is a sailing-ship. It looks as if they always send their singular warning or token before them when starting upon their mission. You see how quickly the deed followed the sign when it came from Dundee. If they had come from Pondicherry in a steamer they would have arrived almost as soon as their letter. But, as a matter of fact, seven weeks elapsed. I think that those seven weeks represented the difference between the mail-boat which brought the letter and the sailing vessel which brought the writer."\
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"It is possible."\
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"More than that. It is probable. And now you see the deadly urgency of this new case, and why I urged young Openshaw to caution. The blow has always fallen at the end of the time which it would take the senders to travel the distance. But this one comes from London, and therefore we cannot count upon delay."\
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"Good God!" I cried. "What can it mean, this relentless persecution?"\
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"The papers which Openshaw carried are obviously of vital importance to the person or persons in the sailing-ship. I think that it is quite clear that there must be more than one of them. A single man could not have carried out two deaths in such a way as to deceive a coroner's jury. There must have been several in it, and they must have been men of resource and determination. Their papers they mean to have, be the holder of them who it may. In this way you see K. K. K. ceases to be the initials of an individual and becomes the badge of a society."\
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"But of what society?"\
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"Have you never--" said Sherlock Holmes, bending forward and sinking his voice--"have you never heard of the Ku Klux Klan?"\
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"I never have."\
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Holmes turned over the leaves of the book upon his knee. "Here it is," said he presently:\
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" 'Ku Klux Klan. A name derived from the fanciful resemblance to the sound produced by cocking a rifle. This terrible secret society was formed by some ex-Confederate soldiers in the Southern states after the Civil War, and it rapidly formed local branches in different parts of the country, notably in Tennessee, Louisiana, the Carolinas, Georgia, and Florida. Its power was used for political purposes, principally for the terrorising of the negro voters and the murdering and driving from the country of those who were opposed to its views. Its outrages were usually preceded by a warning sent to the marked man in some fantastic but generally recognised shape--a sprig of oak-leaves in some parts, melon seeds or orange pips in others. On receiving this the victim might either openly abjure his former ways, or might fly from the country. If he braved the matter out, death would unfailingly come upon him, and usually in some strange and unforeseen manner. So perfect was the organisation of the society, and so systematic its methods, that there is hardly a case upon record where any man succeeded in braving it with impunity, or in which any of its outrages were traced home to the perpetrators. For some years the organisation flourished in spite of the efforts of the United States government and of the better classes of the community in the South. Eventually, in the year 1869, the movement rather suddenly collapsed, although there have been sporadic outbreaks of the same sort since that date.'\
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"You will observe," said Holmes, laying down the volume, "that the sudden breaking up of the society was coincident with the disappearance of Openshaw from America with their papers. It may well have been cause and effect. It is no wonder that he and his family have some of the more implacable spirits upon their track. You can understand that this register and diary may implicate some of the first men in the South, and that there may be many who will not sleep easy at night until it is recovered."\
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"Then the page we have seen--"\
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"Is such as we might expect. It ran, if I remember right, 'sent the pips to A, B, and C'--that is, sent the society's warning to them. Then there are successive entries that A and B cleared, or left the country, and finally that C was visited, with, I fear, a sinister result for C. Well, I think, Doctor, that we may let some light into this dark place, and I believe that the only chance young Openshaw has in the meantime is to do what I have told him. There is nothing more to be said or to be done to-night, so hand me over my violin and let us try to forget for half an hour the miserable weather and the still more miserable ways of our fellow men."\
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It had cleared in the morning, and the sun was shining with a subdued brightness through the dim veil which hangs over the great city. Sherlock Holmes was already at breakfast when I came down.\
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"You will excuse me for not waiting for you," said he; "I have, I foresee, a very busy day before me in looking into this case of young Openshaw's."\
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"What steps will you take?" I asked.\
\
"It will very much depend upon the results of my first inquiries. I may have to go down to Horsham, after all."\
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"You will not go there first?"\
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"No, I shall commence with the City. Just ring the bell and the maid will bring up your coffee."\
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As I waited, I lifted the unopened newspaper from the table and glanced my eye over it. It rested upon a heading which sent a chill to my heart.\
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"Holmes," I cried, "you are too late."\
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"Ah!" said he, laying down his cup, "I feared as much. How was it done?" He spoke calmly, but I could see that he was deeply moved.\
\
"My eye caught the name of Openshaw, and the heading 'Tragedy Near Waterloo Bridge.' Here is the account:\
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" 'Between nine and ten last night Police-Constable Cook, of the H Division, on duty near Waterloo Bridge, heard a cry for help and a splash in the water. The night, however, was extremely dark and stormy, so that, in spite of the help of several passers-by, it was quite impossible to effect a rescue. The alarm, however, was given, and, by the aid of the water-police, the body was eventually recovered. It proved to be that of a young gentleman whose name, as it appears from an envelope which was found in his pocket, was John Openshaw, and whose residence is near Horsham. It is conjectured that he may have been hurrying down to catch the last train from Waterloo Station, and that in his haste and the extreme darkness he missed his path and walked over the edge of one of the small landing-places for river steamboats. The body exhibited no traces of violence, and there can be no doubt that the deceased had been the victim of an unfortunate accident, which should have the effect of calling the attention of the authorities to the condition of the riverside landing-stages.' "\
\
We sat in silence for some minutes, Holmes more depressed and shaken than I had ever seen him.\
\
"That hurts my pride, Watson," he said at last. "It is a petty feeling, no doubt, but it hurts my pride. It becomes a personal matter with me now, and, if God sends me health, I shall set my hand upon this gang. That he should come to me for help, and that I should send him away to his death--!" He sprang from his chair and paced about the room in uncontrollable agitation, with a flush upon his sallow cheeks and a nervous clasping and unclasping of his long thin hands.\
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"They must be cunning devils," he exclaimed at last. "How could they have decoyed him down there? The Embankment is not on the direct line to the station. The bridge, no doubt, was too crowded, even on such a night, for their purpose. Well, Watson, we shall see who will win in the long run. I am going out now!"\
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"To the police?"\
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"No; I shall be my own police. When I have spun the web they may take the flies, but not before."\
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All day I was engaged in my professional work, and it was late in the evening before I returned to Baker Street. Sherlock Holmes had not come back yet. It was nearly ten o'clock before he entered, looking pale and worn. He walked up to the sideboard, and tearing a piece from the loaf he devoured it voraciously, washing it down with a long draught of water.\
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"You are hungry," I remarked.\
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"Starving. It had escaped my memory. I have had nothing since breakfast."\
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"Nothing?"\
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"Not a bite. I had no time to think of it."\
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"And how have you succeeded?"\
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"Well."\
\
"You have a clue?"\
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"I have them in the hollow of my hand. Young Openshaw shall not long remain unavenged. Why, Watson, let us put their own devilish trade-mark upon them. It is well thought of!"\
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"What do you mean?"\
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He took an orange from the cupboard, and tearing it to pieces he squeezed out the pips upon the table. Of these he took five and thrust them into an envelope. On the inside of the flap he wrote "S. H. for J. O." Then he sealed it and addressed it to "Captain James Calhoun, Barque Lone Star, Savannah, Georgia."\
\
"That will await him when he enters port," said he, chuckling. "It may give him a sleepless night. He will find it as sure a precursor of his fate as Openshaw did before him."\
\
"And who is this Captain Calhoun?"\
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"The leader of the gang. I shall have the others, but he first."\
\
"How did you trace it, then?"\
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He took a large sheet of paper from his pocket, all covered with dates and names.\
\
"I have spent the whole day," said he, "over Lloyd's registers and files of the old papers, following the future career of every vessel which touched at Pondicherry in January and February in '83. There were thirty-six ships of fair tonnage which were reported there during those months. Of these, one, the Lone Star, instantly attracted my attention, since, although it was reported as having cleared from London, the name is that which is given to one of the states of the Union."\
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"Texas, I think."\
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"I was not and am not sure which; but I knew that the ship must have an American origin."\
\
"What then?"\
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"I searched the Dundee records, and when I found that the barque Lone Star was there in January, '85, my suspicion became a certainty. I then inquired as to the vessels which lay at present in the port of London."\
\
"Yes?"\
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"The Lone Star had arrived here last week. I went down to the Albert Dock and found that she had been taken down the river by the early tide this morning, homeward bound to Savannah. I wired to Gravesend and learned that she had passed some time ago, and as the wind is easterly I have no doubt that she is now past the Goodwins and not very far from the Isle of Wight."\
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"What will you do, then?"\
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"Oh, I have my hand upon him. He and the two mates, are as I learn, the only native-born Americans in the ship. The others are Finns and Germans. I know, also, that they were all three away from the ship last night. I had it from the stevedore who has been loading their cargo. By the time that their sailing-ship reaches Savannah the mail-boat will have carried this letter, and the cable will have informed the police of Savannah that these three gentlemen are badly wanted here upon a charge of murder."\
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There is ever a flaw, however, in the best laid of human plans, and the murderers of John Openshaw were never to receive the orange pips which would show them that another, as cunning and as resolute as themselves, was upon their track. Very long and very severe were the equinoctial gales that year. We waited long for news of the Lone Star of Savannah, but none ever reached us. We did at last hear that somewhere far out in the Atlantic a shattered stern-post of a boat was seen swinging in the trough of a wave, with the letters "L. S." carved upon it, and that is all which we shall ever know of the fate of the Lone Star.\
\
ADVENTURE  VI.  THE MAN WITH THE TWISTED LIP\
\
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Isa Whitney, brother of the late Elias Whitney, D.D., Principal of the Theological College of St. George's, was much addicted to opium. The habit grew upon him, as I understand, from some foolish freak when he was at college; for having read De Quincey's description of his dreams and sensations, he had drenched his tobacco with laudanum in an attempt to produce the same effects. He found, as so many more have done, that the practice is easier to attain than to get rid of, and for many years he continued to be a slave to the drug, an object of mingled horror and pity to his friends and relatives. I can see him now, with yellow, pasty face, drooping lids, and pin-point pupils, all huddled in a chair, the wreck and ruin of a noble man.\
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One night--it was in June, '89--there came a ring to my bell, about the hour when a man gives his first yawn and glances at the clock. I sat up in my chair, and my wife laid her needle-work down in her lap and made a little face of disappointment.\
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"A patient!" said she. "You'll have to go out."\
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I groaned, for I was newly come back from a weary day.\
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We heard the door open, a few hurried words, and then quick steps upon the linoleum. Our own door flew open, and a lady, clad in some dark-coloured stuff, with a black veil, entered the room.\
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"You will excuse my calling so late," she began, and then, suddenly losing her self-control, she ran forward, threw her arms about my wife's neck, and sobbed upon her shoulder. "Oh, I'm in such trouble!" she cried; "I do so want a little help."\
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"Why," said my wife, pulling up her veil, "it is Kate Whitney. How you startled me, Kate! I had not an idea who you were when you came in."\
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"I didn't know what to do, so I came straight to you." That was always the way. Folk who were in grief came to my wife like birds to a light-house.\
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"It was very sweet of you to come. Now, you must have some wine and water, and sit here comfortably and tell us all about it. Or should you rather that I sent James off to bed?"\
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"Oh, no, no! I want the doctor's advice and help, too. It's about Isa. He has not been home for two days. I am so frightened about him!"\
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It was not the first time that she had spoken to us of her husband's trouble, to me as a doctor, to my wife as an old friend and school companion. We soothed and comforted her by such words as we could find. Did she know where her husband was? Was it possible that we could bring him back to her?\
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It seems that it was. She had the surest information that of late he had, when the fit was on him, made use of an opium den in the farthest east of the City. Hitherto his orgies had always been confined to one day, and he had come back, twitching and shattered, in the evening. But now the spell had been upon him eight-and-forty hours, and he lay there, doubtless among the dregs of the docks, breathing in the poison or sleeping off the effects. There he was to be found, she was sure of it, at the Bar of Gold, in Upper Swandam Lane. But what was she to do? How could she, a young and timid woman, make her way into such a place and pluck her husband out from among the ruffians who surrounded him?\
\
There was the case, and of course there was but one way out of it. Might I not escort her to this place? And then, as a second thought, why should she come at all? I was Isa Whitney's medical adviser, and as such I had influence over him. I could manage it better if I were alone. I promised her on my word that I would send him home in a cab within two hours if he were indeed at the address which she had given me. And so in ten minutes I had left my armchair and cheery sitting-room behind me, and was speeding eastward in a hansom on a strange errand, as it seemed to me at the time, though the future only could show how strange it was to be.\
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But there was no great difficulty in the first stage of my adventure. Upper Swandam Lane is a vile alley lurking behind the high wharves which line the north side of the river to the east of London Bridge. Between a slop-shop and a gin-shop, approached by a steep flight of steps leading down to a black gap like the mouth of a cave, I found the den of which I was in search. Ordering my cab to wait, I passed down the steps, worn hollow in the centre by the ceaseless tread of drunken feet; and by the light of a flickering oil-lamp above the door I found the latch and made my way into a long, low room, thick and heavy with the brown opium smoke, and terraced with wooden berths, like the forecastle of an emigrant ship.\
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Through the gloom one could dimly catch a glimpse of bodies lying in strange fantastic poses, bowed shoulders, bent knees, heads thrown back, and chins pointing upward, with here and there a dark, lack-lustre eye turned upon the newcomer. Out of the black shadows there glimmered little red circles of light, now bright, now faint, as the burning poison waxed or waned in the bowls of the metal pipes. The most lay silent, but some muttered to themselves, and others talked together in a strange, low, monotonous voice, their conversation coming in gushes, and then suddenly tailing off into silence, each mumbling out his own thoughts and paying little heed to the words of his neighbour. At the farther end was a small brazier of burning charcoal, beside which on a three-legged wooden stool there sat a tall, thin old man, with his jaw resting upon his two fists, and his elbows upon his knees, staring into the fire.\
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As I entered, a sallow Malay attendant had hurried up with a pipe for me and a supply of the drug, beckoning me to an empty berth.\
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"Thank you. I have not come to stay," said I. "There is a friend of mine here, Mr. Isa Whitney, and I wish to speak with him."\
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There was a movement and an exclamation from my right, and peering through the gloom, I saw Whitney, pale, haggard, and unkempt, staring out at me.\
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"My God! It's Watson," said he. He was in a pitiable state of reaction, with every nerve in a twitter. "I say, Watson, what o'clock is it?"\
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"Nearly eleven."\
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"Of what day?"\
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"Of Friday, June 19th."\
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"Good heavens! I thought it was Wednesday. It is Wednesday. What d'you want to frighten a chap for?" He sank his face onto his arms and began to sob in a high treble key.\
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"I tell you that it is Friday, man. Your wife has been waiting this two days for you. You should be ashamed of yourself!"\
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"So I am. But you've got mixed, Watson, for I have only been here a few hours, three pipes, four pipes--I forget how many. But I'll go home with you. I wouldn't frighten Kate--poor little Kate. Give me your hand! Have you a cab?"\
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"Yes, I have one waiting."\
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"Then I shall go in it. But I must owe something. Find what I owe, Watson. I am all off colour. I can do nothing for myself."\
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I walked down the narrow passage between the double row of sleepers, holding my breath to keep out the vile, stupefying fumes of the drug, and looking about for the manager. As I passed the tall man who sat by the brazier I felt a sudden pluck at my skirt, and a low voice whispered, "Walk past me, and then look back at me." The words fell quite distinctly upon my ear. I glanced down. They could only have come from the old man at my side, and yet he sat now as absorbed as ever, very thin, very wrinkled, bent with age, an opium pipe dangling down from between his knees, as though it had dropped in sheer lassitude from his fingers. I took two steps forward and looked back. It took all my self-control to prevent me from breaking out into a cry of astonishment. He had turned his back so that none could see him but I. His form had filled out, his wrinkles were gone, the dull eyes had regained their fire, and there, sitting by the fire and grinning at my surprise, was none other than Sherlock Holmes. He made a slight motion to me to approach him, and instantly, as he turned his face half round to the company once more, subsided into a doddering, loose-lipped senility.\
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"Holmes!" I whispered, "what on earth are you doing in this den?"\
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"As low as you can," he answered; "I have excellent ears. If you would have the great kindness to get rid of that sottish friend of yours I should be exceedingly glad to have a little talk with you."\
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"I have a cab outside."\
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"Then pray send him home in it. You may safely trust him, for he appears to be too limp to get into any mischief. I should recommend you also to send a note by the cabman to your wife to say that you have thrown in your lot with me. If you will wait outside, I shall be with you in five minutes."\
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It was difficult to refuse any of Sherlock Holmes' requests, for they were always so exceedingly definite, and put forward with such a quiet air of mastery. I felt, however, that when Whitney was once confined in the cab my mission was practically accomplished; and for the rest, I could not wish anything better than to be associated with my friend in one of those singular adventures which were the normal condition of his existence. In a few minutes I had written my note, paid Whitney's bill, led him out to the cab, and seen him driven through the darkness. In a very short time a decrepit figure had emerged from the opium den, and I was walking down the street with Sherlock Holmes. For two streets he shuffled along with a bent back and an uncertain foot. Then, glancing quickly round, he straightened himself out and burst into a hearty fit of laughter.\
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"I suppose, Watson," said he, "that you imagine that I have added opium-smoking to cocaine injections, and all the other little weaknesses on which you have favoured me with your medical views."\
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"I was certainly surprised to find you there."\
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"But not more so than I to find you."\
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"I came to find a friend."\
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"And I to find an enemy."\
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"An enemy?"\
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"Yes; one of my natural enemies, or, shall I say, my natural prey. Briefly, Watson, I am in the midst of a very remarkable inquiry, and I have hoped to find a clue in the incoherent ramblings of these sots, as I have done before now. Had I been recognised in that den my life would not have been worth an hour's purchase; for I have used it before now for my own purposes, and the rascally Lascar who runs it has sworn to have vengeance upon me. There is a trap-door at the back of that building, near the corner of Paul's Wharf, which could tell some strange tales of what has passed through it upon the moonless nights."\
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"What! You do not mean bodies?"\
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"Ay, bodies, Watson. We should be rich men if we had $1000 for every poor devil who has been done to death in that den. It is the vilest murder-trap on the whole riverside, and I fear that Neville St. Clair has entered it never to leave it more. But our trap should be here." He put his two forefingers between his teeth and whistled shrilly--a signal which was answered by a similar whistle from the distance, followed shortly by the rattle of wheels and the clink of horses' hoofs.\
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"Now, Watson," said Holmes, as a tall dog-cart dashed up through the gloom, throwing out two golden tunnels of yellow light from its side lanterns. "You'll come with me, won't you?"\
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"If I can be of use."\
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"Oh, a trusty comrade is always of use; and a chronicler still more so. My room at The Cedars is a double-bedded one."\
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"The Cedars?"\
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"Yes; that is Mr. St. Clair's house. I am staying there while I conduct the inquiry."\
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"Where is it, then?"\
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"Near Lee, in Kent. We have a seven-mile drive before us."\
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"But I am all in the dark."\
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"Of course you are. You'll know all about it presently. Jump up here. All right, John; we shall not need you. Here's half a crown. Look out for me to-morrow, about eleven. Give her her head. So long, then!"\
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He flicked the horse with his whip, and we dashed away through the endless succession of sombre and deserted streets, which widened gradually, until we were flying across a broad balustraded bridge, with the murky river flowing sluggishly beneath us. Beyond lay another dull wilderness of bricks and mortar, its silence broken only by the heavy, regular footfall of the policeman, or the songs and shouts of some belated party of revellers. A dull wrack was drifting slowly across the sky, and a star or two twinkled dimly here and there through the rifts of the clouds. Holmes drove in silence, with his head sunk upon his breast, and the air of a man who is lost in thought, while I sat beside him, curious to learn what this new quest might be which seemed to tax his powers so sorely, and yet afraid to break in upon the current of his thoughts. We had driven several miles, and were beginning to get to the fringe of the belt of suburban villas, when he shook himself, shrugged his shoulders, and lit up his pipe with the air of a man who has satisfied himself that he is acting for the best.\
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"You have a grand gift of silence, Watson," said he. "It makes you quite invaluable as a companion. 'Pon my word, it is a great thing for me to have someone to talk to, for my own thoughts are not over-pleasant. I was wondering what I should say to this dear little woman to-night when she meets me at the door."\
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"You forget that I know nothing about it."\
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"I shall just have time to tell you the facts of the case before we get to Lee. It seems absurdly simple, and yet, somehow I can get nothing to go upon. There's plenty of thread, no doubt, but I can't get the end of it into my hand. Now, I'll state the case clearly and concisely to you, Watson, and maybe you can see a spark where all is dark to me."\
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"Proceed, then."\
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"Some years ago--to be definite, in May, 1884--there came to Lee a gentleman, Neville St. Clair by name, who appeared to have plenty of money. He took a large villa, laid out the grounds very nicely, and lived generally in good style. By degrees he made friends in the neighbourhood, and in 1887 he married the daughter of a local brewer, by whom he now has two children. He had no occupation, but was interested in several companies and went into town as a rule in the morning, returning by the 5:14 from Cannon Street every night. Mr. St. Clair is now thirty-seven years of age, is a man of temperate habits, a good husband, a very affectionate father, and a man who is popular with all who know him. I may add that his whole debts at the present moment, as far as we have been able to ascertain, amount to $88 10s., while he has $220 standing to his credit in the Capital and Counties Bank. There is no reason, therefore, to think that money troubles have been weighing upon his mind.\
\
"Last Monday Mr. Neville St. Clair went into town rather earlier than usual, remarking before he started that he had two important commissions to perform, and that he would bring his little boy home a box of bricks. Now, by the merest chance, his wife received a telegram upon this same Monday, very shortly after his departure, to the effect that a small parcel of considerable value which she had been expecting was waiting for her at the offices of the Aberdeen Shipping Company. Now, if you are well up in your London, you will know that the office of the company is in Fresno Street, which branches out of Upper Swandam Lane, where you found me to-night. Mrs. St. Clair had her lunch, started for the City, did some shopping, proceeded to the company's office, got her packet, and found herself at exactly 4:35 walking through Swandam Lane on her way back to the station. Have you followed me so far?"\
\
"It is very clear."\
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"If you remember, Monday was an exceedingly hot day, and Mrs. St. Clair walked slowly, glancing about in the hope of seeing a cab, as she did not like the neighbourhood in which she found herself. While she was walking in this way down Swandam Lane, she suddenly heard an ejaculation or cry, and was struck cold to see her husband looking down at her and, as it seemed to her, beckoning to her from a second-floor window. The window was open, and she distinctly saw his face, which she describes as being terribly agitated. He waved his hands frantically to her, and then vanished from the window so suddenly that it seemed to her that he had been plucked back by some irresistible force from behind. One singular point which struck her quick feminine eye was that although he wore some dark coat, such as he had started to town in, he had on neither collar nor necktie.\
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"Convinced that something was amiss with him, she rushed down the steps--for the house was none other than the opium den in which you found me to-night--and running through the front room she attempted to ascend the stairs which led to the first floor. At the foot of the stairs, however, she met this Lascar scoundrel of whom I have spoken, who thrust her back and, aided by a Dane, who acts as assistant there, pushed her out into the street. Filled with the most maddening doubts and fears, she rushed down the lane and, by rare good-fortune, met in Fresno Street a number of constables with an inspector, all on their way to their beat. The inspector and two men accompanied her back, and in spite of the continued resistance of the proprietor, they made their way to the room in which Mr. St. Clair had last been seen. There was no sign of him there. In fact, in the whole of that floor there was no one to be found save a crippled wretch of hideous aspect, who, it seems, made his home there. Both he and the Lascar stoutly swore that no one else had been in the front room during the afternoon. So determined was their denial that the inspector was staggered, and had almost come to believe that Mrs. St. Clair had been deluded when, with a cry, she sprang at a small deal box which lay upon the table and tore the lid from it. Out there fell a cascade of children's bricks. It was the toy which he had promised to bring home.\
\
"This discovery, and the evident confusion which the cripple showed, made the inspector realise that the matter was serious. The rooms were carefully examined, and results all pointed to an abominable crime. The front room was plainly furnished as a sitting-room and led into a small bedroom, which looked out upon the back of one of the wharves. Between the wharf and the bedroom window is a narrow strip, which is dry at low tide but is covered at high tide with at least four and a half feet of water. The bedroom window was a broad one and opened from below. On examination traces of blood were to be seen upon the windowsill, and several scattered drops were visible upon the wooden floor of the bedroom. Thrust away behind a curtain in the front room were all the clothes of Mr. Neville St. Clair, with the exception of his coat. His boots, his socks, his hat, and his watch--all were there. There were no signs of violence upon any of these garments, and there were no other traces of Mr. Neville St. Clair. Out of the window he must apparently have gone for no other exit could be discovered, and the ominous bloodstains upon the sill gave little promise that he could save himself by swimming, for the tide was at its very highest at the moment of the tragedy.\
\
"And now as to the villains who seemed to be immediately implicated in the matter. The Lascar was known to be a man of the vilest antecedents, but as, by Mrs. St. Clair's story, he was known to have been at the foot of the stair within a very few seconds of her husband's appearance at the window, he could hardly have been more than an accessory to the crime. His defence was one of absolute ignorance, and he protested that he had no knowledge as to the doings of Hugh Boone, his lodger, and that he could not account in any way for the presence of the missing gentleman's clothes.\
\
"So much for the Lascar manager. Now for the sinister cripple who lives upon the second floor of the opium den, and who was certainly the last human being whose eyes rested upon Neville St. Clair. His name is Hugh Boone, and his hideous face is one which is familiar to every man who goes much to the City. He is a professional beggar, though in order to avoid the police regulations he pretends to a small trade in wax vestas. Some little distance down Threadneedle Street, upon the left-hand side, there is, as you may have remarked, a small angle in the wall. Here it is that this creature takes his daily seat, cross-legged with his tiny stock of matches on his lap, and as he is a piteous spectacle a small rain of charity descends into the greasy leather cap which lies upon the pavement beside him. I have watched the fellow more than once before ever I thought of making his professional acquaintance, and I have been surprised at the harvest which he has reaped in a short time. His appearance, you see, is so remarkable that no one can pass him without observing him. A shock of orange hair, a pale face disfigured by a horrible scar, which, by its contraction, has turned up the outer edge of his upper lip, a bulldog chin, and a pair of very penetrating dark eyes, which present a singular contrast to the colour of his hair, all mark him out from amid the common crowd of mendicants and so, too, does his wit, for he is ever ready with a reply to any piece of chaff which may be thrown at him by the passers-by. This is the man whom we now learn to have been the lodger at the opium den, and to have been the last man to see the gentleman of whom we are in quest."\
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"But a cripple!" said I. "What could he have done single-handed against a man in the prime of life?"\
\
"He is a cripple in the sense that he walks with a limp; but in other respects he appears to be a powerful and well-nurtured man. Surely your medical experience would tell you, Watson, that weakness in one limb is often compensated for by exceptional strength in the others."\
\
"Pray continue your narrative."\
\
"Mrs. St. Clair had fainted at the sight of the blood upon the window, and she was escorted home in a cab by the police, as her presence could be of no help to them in their investigations. Inspector Barton, who had charge of the case, made a very careful examination of the premises, but without finding anything which threw any light upon the matter. One mistake had been made in not arresting Boone instantly, as he was allowed some few minutes during which he might have communicated with his friend the Lascar, but this fault was soon remedied, and he was seized and searched, without anything being found which could incriminate him. There were, it is true, some blood-stains upon his right shirt-sleeve, but he pointed to his ring-finger, which had been cut near the nail, and explained that the bleeding came from there, adding that he had been to the window not long before, and that the stains which had been observed there came doubtless from the same source. He denied strenuously having ever seen Mr. Neville St. Clair and swore that the presence of the clothes in his room was as much a mystery to him as to the police. As to Mrs. St. Clair's assertion that she had actually seen her husband at the window, he declared that she must have been either mad or dreaming. He was removed, loudly protesting, to the police-station, while the inspector remained upon the premises in the hope that the ebbing tide might afford some fresh clue.\
\
"And it did, though they hardly found upon the mud-bank what they had feared to find. It was Neville St. Clair's coat, and not Neville St. Clair, which lay uncovered as the tide receded. And what do you think they found in the pockets?"\
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"I cannot imagine."\
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"No, I don't think you would guess. Every pocket stuffed with pennies and half-pennies--421 pennies and 270 half-pennies. It was no wonder that it had not been swept away by the tide. But a human body is a different matter. There is a fierce eddy between the wharf and the house. It seemed likely enough that the weighted coat had remained when the stripped body had been sucked away into the river."\
\
"But I understand that all the other clothes were found in the room. Would the body be dressed in a coat alone?"\
\
"No, sir, but the facts might be met speciously enough. Suppose that this man Boone had thrust Neville St. Clair through the window, there is no human eye which could have seen the deed. What would he do then? It would of course instantly strike him that he must get rid of the tell-tale garments. He would seize the coat, then, and be in the act of throwing it out, when it would occur to him that it would swim and not sink. He has little time, for he has heard the scuffle downstairs when the wife tried to force her way up, and perhaps he has already heard from his Lascar confederate that the police are hurrying up the street. There is not an instant to be lost. He rushes to some secret hoard, where he has accumulated the fruits of his beggary, and he stuffs all the coins upon which he can lay his hands into the pockets to make sure of the coat's sinking. He throws it out, and would have done the same with the other garments had not he heard the rush of steps below, and only just had time to close the window when the police appeared."\
\
"It certainly sounds feasible."\
\
"Well, we will take it as a working hypothesis for want of a better. Boone, as I have told you, was arrested and taken to the station, but it could not be shown that there had ever before been anything against him. He had for years been known as a professional beggar, but his life appeared to have been a very quiet and innocent one. There the matter stands at present, and the questions which have to be solved--what Neville St. Clair was doing in the opium den, what happened to him when there, where is he now, and what Hugh Boone had to do with his disappearance--are all as far from a solution as ever. I confess that I cannot recall any case within my experience which looked at the first glance so simple and yet which presented such difficulties."\
\
While Sherlock Holmes had been detailing this singular series of events, we had been whirling through the outskirts of the great town until the last straggling houses had been left behind, and we rattled along with a country hedge upon either side of us. Just as he finished, however, we drove through two scattered villages, where a few lights still glimmered in the windows.\
\
"We are on the outskirts of Lee," said my companion. "We have touched on three English counties in our short drive, starting in Middlesex, passing over an angle of Surrey, and ending in Kent. See that light among the trees? That is The Cedars, and beside that lamp sits a woman whose anxious ears have already, I have little doubt, caught the clink of our horse's feet."\
\
"But why are you not conducting the case from Baker Street?" I asked.\
\
"Because there are many inquiries which must be made out here. Mrs. St. Clair has most kindly put two rooms at my disposal, and you may rest assured that she will have nothing but a welcome for my friend and colleague. I hate to meet her, Watson, when I have no news of her husband. Here we are. Whoa, there, whoa!"\
\
We had pulled up in front of a large villa which stood within its own grounds. A stable-boy had run out to the horse's head, and springing down, I followed Holmes up the small, winding gravel-drive which led to the house. As we approached, the door flew open, and a little blonde woman stood in the opening, clad in some sort of light mousseline de soie, with a touch of fluffy pink chiffon at her neck and wrists. She stood with her figure outlined against the flood of light, one hand upon the door, one half-raised in her eagerness, her body slightly bent, her head and face protruded, with eager eyes and parted lips, a standing question.\
\
"Well?" she cried, "well?" And then, seeing that there were two of us, she gave a cry of hope which sank into a groan as she saw that my companion shook his head and shrugged his shoulders.\
\
"No good news?"\
\
"None."\
\
"No bad?"\
\
"No."\
\
"Thank God for that. But come in. You must be weary, for you have had a long day."\
\
"This is my friend, Dr. Watson. He has been of most vital use to me in several of my cases, and a lucky chance has made it possible for me to bring him out and associate him with this investigation."\
\
"I am delighted to see you," said she, pressing my hand warmly. "You will, I am sure, forgive anything that may be wanting in our arrangements, when you consider the blow which has come so suddenly upon us."\
\
"My dear madam," said I, "I am an old campaigner, and if I were not I can very well see that no apology is needed. If I can be of any assistance, either to you or to my friend here, I shall be indeed happy."\
\
"Now, Mr. Sherlock Holmes," said the lady as we entered a well-lit dining-room, upon the table of which a cold supper had been laid out, "I should very much like to ask you one or two plain questions, to which I beg that you will give a plain answer."\
\
"Certainly, madam."\
\
"Do not trouble about my feelings. I am not hysterical, nor given to fainting. I simply wish to hear your real, real opinion."\
\
"Upon what point?"\
\
"In your heart of hearts, do you think that Neville is alive?"\
\
Sherlock Holmes seemed to be embarrassed by the question. "Frankly, now!" she repeated, standing upon the rug and looking keenly down at him as he leaned back in a basket-chair.\
\
"Frankly, then, madam, I do not."\
\
"You think that he is dead?"\
\
"I do."\
\
"Murdered?"\
\
"I don't say that. Perhaps."\
\
"And on what day did he meet his death?"\
\
"On Monday."\
\
"Then perhaps, Mr. Holmes, you will be good enough to explain how it is that I have received a letter from him to-day."\
\
Sherlock Holmes sprang out of his chair as if he had been galvanised.\
\
"What!" he roared.\
\
"Yes, to-day." She stood smiling, holding up a little slip of paper in the air.\
\
"May I see it?"\
\
"Certainly."\
\
He snatched it from her in his eagerness, and smoothing it out upon the table he drew over the lamp and examined it intently. I had left my chair and was gazing at it over his shoulder. The envelope was a very coarse one and was stamped with the Gravesend postmark and with the date of that very day, or rather of the day before, for it was considerably after midnight.\
\
"Coarse writing," murmured Holmes. "Surely this is not your husband's writing, madam."\
\
"No, but the enclosure is."\
\
"I perceive also that whoever addressed the envelope had to go and inquire as to the address."\
\
"How can you tell that?"\
\
"The name, you see, is in perfectly black ink, which has dried itself. The rest is of the greyish colour, which shows that blotting-paper has been used. If it had been written straight off, and then blotted, none would be of a deep black shade. This man has written the name, and there has then been a pause before he wrote the address, which can only mean that he was not familiar with it. It is, of course, a trifle, but there is nothing so important as trifles. Let us now see the letter. Ha! there has been an enclosure here!"\
\
"Yes, there was a ring. His signet-ring."\
\
"And you are sure that this is your husband's hand?"\
\
"One of his hands."\
\
"One?"\
\
"His hand when he wrote hurriedly. It is very unlike his usual writing, and yet I know it well."\
\
" 'Dearest do not be frightened. All will come well. There is a huge error which it may take some little time to rectify. Wait in patience.--NEVILLE.' Written in pencil upon the fly-leaf of a book, octavo size, no water-mark. Hum! Posted to-day in Gravesend by a man with a dirty thumb. Ha! And the flap has been gummed, if I am not very much in error, by a person who had been chewing tobacco. And you have no doubt that it is your husband's hand, madam?"\
\
"None. Neville wrote those words."\
\
"And they were posted to-day at Gravesend. Well, Mrs. St. Clair, the clouds lighten, though I should not venture to say that the danger is over."\
\
"But he must be alive, Mr. Holmes."\
\
"Unless this is a clever forgery to put us on the wrong scent. The ring, after all, proves nothing. It may have been taken from him."\
\
"No, no; it is, it is his very own writing!"\
\
"Very well. It may, however, have been written on Monday and only posted to-day."\
\
"That is possible."\
\
"If so, much may have happened between."\
\
"Oh, you must not discourage me, Mr. Holmes. I know that all is well with him. There is so keen a sympathy between us that I should know if evil came upon him. On the very day that I saw him last he cut himself in the bedroom, and yet I in the dining-room rushed upstairs instantly with the utmost certainty that something had happened. Do you think that I would respond to such a trifle and yet be ignorant of his death?"\
\
"I have seen too much not to know that the impression of a woman may be more valuable than the conclusion of an analytical reasoner. And in this letter you certainly have a very strong piece of evidence to corroborate your view. But if your husband is alive and able to write letters, why should he remain away from you?"\
\
"I cannot imagine. It is unthinkable."\
\
"And on Monday he made no remarks before leaving you?"\
\
"No."\
\
"And you were surprised to see him in Swandam Lane?"\
\
"Very much so."\
\
"Was the window open?"\
\
"Yes."\
\
"Then he might have called to you?"\
\
"He might."\
\
"He only, as I understand, gave an inarticulate cry?"\
\
"Yes."\
\
"A call for help, you thought?"\
\
"Yes. He waved his hands."\
\
"But it might have been a cry of surprise. Astonishment at the unexpected sight of you might cause him to throw up his hands?"\
\
"It is possible."\
\
"And you thought he was pulled back?"\
\
"He disappeared so suddenly."\
\
"He might have leaped back. You did not see anyone else in the room?"\
\
"No, but this horrible man confessed to having been there, and the Lascar was at the foot of the stairs."\
\
"Quite so. Your husband, as far as you could see, had his ordinary clothes on?"\
\
"But without his collar or tie. I distinctly saw his bare throat."\
\
"Had he ever spoken of Swandam Lane?"\
\
"Never."\
\
"Had he ever showed any signs of having taken opium?"\
\
"Never."\
\
"Thank you, Mrs. St. Clair. Those are the principal points about which I wished to be absolutely clear. We shall now have a little supper and then retire, for we may have a very busy day to-morrow."\
\
A large and comfortable double-bedded room had been placed at our disposal, and I was quickly between the sheets, for I was weary after my night of adventure. Sherlock Holmes was a man, however, who, when he had an unsolved problem upon his mind, would go for days, and even for a week, without rest, turning it over, rearranging his facts, looking at it from every point of view until he had either fathomed it or convinced himself that his data were insufficient. It was soon evident to me that he was now preparing for an all-night sitting. He took off his coat and waistcoat, put on a large blue dressing-gown, and then wandered about the room collecting pillows from his bed and cushions from the sofa and armchairs. With these he constructed a sort of Eastern divan, upon which he perched himself cross-legged, with an ounce of shag tobacco and a box of matches laid out in front of him. In the dim light of the lamp I saw him sitting there, an old briar pipe between his lips, his eyes fixed vacantly upon the corner of the ceiling, the blue smoke curling up from him, silent, motionless, with the light shining upon his strong-set aquiline features. So he sat as I dropped off to sleep, and so he sat when a sudden ejaculation caused me to wake up, and I found the summer sun shining into the apartment. The pipe was still between his lips, the smoke still curled upward, and the room was full of a dense tobacco haze, but nothing remained of the heap of shag which I had seen upon the previous night.\
\
"Awake, Watson?" he asked.\
\
"Yes."\
\
"Game for a morning drive?"\
\
"Certainly."\
\
"Then dress. No one is stirring yet, but I know where the stable-boy sleeps, and we shall soon have the trap out." He chuckled to himself as he spoke, his eyes twinkled, and he seemed a different man to the sombre thinker of the previous night.\
\
As I dressed I glanced at my watch. It was no wonder that no one was stirring. It was twenty-five minutes past four. I had hardly finished when Holmes returned with the news that the boy was putting in the horse.\
\
"I want to test a little theory of mine," said he, pulling on his boots. "I think, Watson, that you are now standing in the presence of one of the most absolute fools in Europe. I deserve to be kicked from here to Charing Cross. But I think I have the key of the affair now."\
\
"And where is it?" I asked, smiling.\
\
"In the bathroom," he answered. "Oh, yes, I am not joking," he continued, seeing my look of incredulity. "I have just been there, and I have taken it out, and I have got it in this Gladstone bag. Come on, my boy, and we shall see whether it will not fit the lock."\
\
We made our way downstairs as quietly as possible, and out into the bright morning sunshine. In the road stood our horse and trap, with the half-clad stable-boy waiting at the head. We both sprang in, and away we dashed down the London Road. A few country carts were stirring, bearing in vegetables to the metropolis, but the lines of villas on either side were as silent and lifeless as some city in a dream.\
\
"It has been in some points a singular case," said Holmes, flicking the horse on into a gallop. "I confess that I have been as blind as a mole, but it is better to learn wisdom late than never to learn it at all."\
\
In town the earliest risers were just beginning to look sleepily from their windows as we drove through the streets of the Surrey side. Passing down the Waterloo Bridge Road we crossed over the river, and dashing up Wellington Street wheeled sharply to the right and found ourselves in Bow Street. Sherlock Holmes was well known to the force, and the two constables at the door saluted him. One of them held the horse's head while the other led us in.\
\
"Who is on duty?" asked Holmes.\
\
"Inspector Bradstreet, sir."\
\
"Ah, Bradstreet, how are you?" A tall, stout official had come down the stone-flagged passage, in a peaked cap and frogged jacket. "I wish to have a quiet word with you, Bradstreet." "Certainly, Mr. Holmes. Step into my room here." It was a small, office-like room, with a huge ledger upon the table, and a telephone projecting from the wall. The inspector sat down at his desk.\
\
"What can I do for you, Mr. Holmes?"\
\
"I called about that beggarman, Boone--the one who was charged with being concerned in the disappearance of Mr. Neville St. Clair, of Lee."\
\
"Yes. He was brought up and remanded for further inquiries."\
\
"So I heard. You have him here?"\
\
"In the cells."\
\
"Is he quiet?"\
\
"Oh, he gives no trouble. But he is a dirty scoundrel."\
\
"Dirty?"\
\
"Yes, it is all we can do to make him wash his hands, and his face is as black as a tinker's. Well, when once his case has been settled, he will have a regular prison bath; and I think, if you saw him, you would agree with me that he needed it."\
\
"I should like to see him very much."\
\
"Would you? That is easily done. Come this way. You can leave your bag."\
\
"No, I think that I'll take it."\
\
"Very good. Come this way, if you please." He led us down a passage, opened a barred door, passed down a winding stair, and brought us to a whitewashed corridor with a line of doors on each side.\
\
"The third on the right is his," said the inspector. "Here it is!" He quietly shot back a panel in the upper part of the door and glanced through.\
\
"He is asleep," said he. "You can see him very well."\
\
We both put our eyes to the grating. The prisoner lay with his face towards us, in a very deep sleep, breathing slowly and heavily. He was a middle-sized man, coarsely clad as became his calling, with a coloured shirt protruding through the rent in his tattered coat. He was, as the inspector had said, extremely dirty, but the grime which covered his face could not conceal its repulsive ugliness. A broad wheal from an old scar ran right across it from eye to chin, and by its contraction had turned up one side of the upper lip, so that three teeth were exposed in a perpetual snarl. A shock of very bright red hair grew low over his eyes and forehead.\
\
"He's a beauty, isn't he?" said the inspector.\
\
"He certainly needs a wash," remarked Holmes. "I had an idea that he might, and I took the liberty of bringing the tools with me." He opened the Gladstone bag as he spoke, and took out, to my astonishment, a very large bath-sponge.\
\
"He! he! You are a funny one," chuckled the inspector.\
\
"Now, if you will have the great goodness to open that door very quietly, we will soon make him cut a much more respectable figure."\
\
"Well, I don't know why not," said the inspector. "He doesn't look a credit to the Bow Street cells, does he?" He slipped his key into the lock, and we all very quietly entered the cell. The sleeper half turned, and then settled down once more into a deep slumber. Holmes stooped to the water-jug, moistened his sponge, and then rubbed it twice vigorously across and down the prisoner's face.\
\
"Let me introduce you," he shouted, "to Mr. Neville St. Clair, of Lee, in the county of Kent."\
\
Never in my life have I seen such a sight. The man's face peeled off under the sponge like the bark from a tree. Gone was the coarse brown tint! Gone, too, was the horrid scar which had seamed it across, and the twisted lip which had given the repulsive sneer to the face! A twitch brought away the tangled red hair, and there, sitting up in his bed, was a pale, sad-faced, refined-looking man, black-haired and smooth-skinned, rubbing his eyes and staring about him with sleepy bewilderment. Then suddenly realising the exposure, he broke into a scream and threw himself down with his face to the pillow.\
\
"Great heavens!" cried the inspector, "it is, indeed, the missing man. I know him from the photograph."\
\
The prisoner turned with the reckless air of a man who abandons himself to his destiny. "Be it so," said he. "And pray what am I charged with?"\
\
"With making away with Mr. Neville St.-- Oh, come, you can't be charged with that unless they make a case of attempted suicide of it," said the inspector with a grin. "Well, I have been twenty-seven years in the force, but this really takes the cake."\
\
"If I am Mr. Neville St. Clair, then it is obvious that no crime has been committed, and that, therefore, I am illegally detained."\
\
"No crime, but a very great error has been committed," said Holmes. "You would have done better to have trusted you wife."\
\
"It was not the wife; it was the children," groaned the prisoner. "God help me, I would not have them ashamed of their father. My God! What an exposure! What can I do?"\
\
Sherlock Holmes sat down beside him on the couch and patted him kindly on the shoulder.\
\
"If you leave it to a court of law to clear the matter up," said he, "of course you can hardly avoid publicity. On the other hand, if you convince the police authorities that there is no possible case against you, I do not know that there is any reason that the details should find their way into the papers. Inspector Bradstreet would, I am sure, make notes upon anything which you might tell us and submit it to the proper authorities. The case would then never go into court at all."\
\
"God bless you!" cried the prisoner passionately. "I would have endured imprisonment, ay, even execution, rather than have left my miserable secret as a family blot to my children.\
\
"You are the first who have ever heard my story. My father was a schoolmaster in Chesterfield, where I received an excellent education. I travelled in my youth, took to the stage, and finally became a reporter on an evening paper in London. One day my editor wished to have a series of articles upon begging in the metropolis, and I volunteered to supply them. There was the point from which all my adventures started. It was only by trying begging as an amateur that I could get the facts upon which to base my articles. When an actor I had, of course, learned all the secrets of making up, and had been famous in the green-room for my skill. I took advantage now of my attainments. I painted my face, and to make myself as pitiable as possible I made a good scar and fixed one side of my lip in a twist by the aid of a small slip of flesh-coloured plaster. Then with a red head of hair, and an appropriate dress, I took my station in the business part of the city, ostensibly as a match-seller but really as a beggar. For seven hours I plied my trade, and when I returned home in the evening I found to my surprise that I had received no less than 26s. 4d.\
\
"I wrote my articles and thought little more of the matter until, some time later, I backed a bill for a friend and had a writ served upon me for $25. I was at my wit's end where to get the money, but a sudden idea came to me. I begged a fortnight's grace from the creditor, asked for a holiday from my employers, and spent the time in begging in the City under my disguise. In ten days I had the money and had paid the debt.\
\
"Well, you can imagine how hard it was to settle down to arduous work at $2 a week when I knew that I could earn as much in a day by smearing my face with a little paint, laying my cap on the ground, and sitting still. It was a long fight between my pride and the money, but the dollars won at last, and I threw up reporting and sat day after day in the corner which I had first chosen, inspiring pity by my ghastly face and filling my pockets with coppers. Only one man knew my secret. He was the keeper of a low den in which I used to lodge in Swandam Lane, where I could every morning emerge as a squalid beggar and in the evenings transform myself into a well-dressed man about town. This fellow, a Lascar, was well paid by me for his rooms, so that I knew that my secret was safe in his possession.\
\
"Well, very soon I found that I was saving considerable sums of money. I do not mean that any beggar in the streets of London could earn $700 a year--which is less than my average takings--but I had exceptional advantages in my power of making up, and also in a facility of repartee, which improved by practice and made me quite a recognised character in the City. All day a stream of pennies, varied by silver, poured in upon me, and it was a very bad day in which I failed to take $2.\
\
"As I grew richer I grew more ambitious, took a house in the country, and eventually married, without anyone having a suspicion as to my real occupation. My dear wife knew that I had business in the City. She little knew what.\
\
"Last Monday I had finished for the day and was dressing in my room above the opium den when I looked out of my window and saw, to my horror and astonishment, that my wife was standing in the street, with her eyes fixed full upon me. I gave a cry of surprise, threw up my arms to cover my face, and, rushing to my confidant, the Lascar, entreated him to prevent anyone from coming up to me. I heard her voice downstairs, but I knew that she could not ascend. Swiftly I threw off my clothes, pulled on those of a beggar, and put on my pigments and wig. Even a wife's eyes could not pierce so complete a disguise. But then it occurred to me that there might be a search in the room, and that the clothes might betray me. I threw open the window, reopening by my violence a small cut which I had inflicted upon myself in the bedroom that morning. Then I seized my coat, which was weighted by the coppers which I had just transferred to it from the leather bag in which I carried my takings. I hurled it out of the window, and it disappeared into the Thames. The other clothes would have followed, but at that moment there was a rush of constables up the stair, and a few minutes after I found, rather, I confess, to my relief, that instead of being identified as Mr. Neville St. Clair, I was arrested as his murderer.\
\
"I do not know that there is anything else for me to explain. I was determined to preserve my disguise as long as possible, and hence my preference for a dirty face. Knowing that my wife would be terribly anxious, I slipped off my ring and confided it to the Lascar at a moment when no constable was watching me, together with a hurried scrawl, telling her that she had no cause to fear."\
\
"That note only reached her yesterday," said Holmes.\
\
"Good God! What a week she must have spent!"\
\
"The police have watched this Lascar," said Inspector Bradstreet, "and I can quite understand that he might find it difficult to post a letter unobserved. Probably he handed it to some sailor customer of his, who forgot all about it for some days."\
\
"That was it," said Holmes, nodding approvingly; "I have no doubt of it. But have you never been prosecuted for begging?"\
\
"Many times; but what was a fine to me?"\
\
"It must stop here, however," said Bradstreet. "If the police are to hush this thing up, there must be no more of Hugh Boone."\
\
"I have sworn it by the most solemn oaths which a man can take."\
\
"In that case I think that it is probable that no further steps may be taken. But if you are found again, then all must come out. I am sure, Mr. Holmes, that we are very much indebted to you for having cleared the matter up. I wish I knew how you reach your results."\
\
"I reached this one," said my friend, "by sitting upon five pillows and consuming an ounce of shag. I think, Watson, that if we drive to Baker Street we shall just be in time for breakfast."\
\
VII.  THE ADVENTURE OF THE BLUE CARBUNCLE\
\
\
I had called upon my friend Sherlock Holmes upon the second morning after Christmas, with the intention of wishing him the compliments of the season. He was lounging upon the sofa in a purple dressing-gown, a pipe-rack within his reach upon the right, and a pile of crumpled morning papers, evidently newly studied, near at hand. Beside the couch was a wooden chair, and on the angle of the back hung a very seedy and disreputable hard-felt hat, much the worse for wear, and cracked in several places. A lens and a forceps lying upon the seat of the chair suggested that the hat had been suspended in this manner for the purpose of examination.\
\
"You are engaged," said I; "perhaps I interrupt you."\
\
"Not at all. I am glad to have a friend with whom I can discuss my results. The matter is a perfectly trivial one"--he jerked his thumb in the direction of the old hat--"but there are points in connection with it which are not entirely devoid of interest and even of instruction."\
\
I seated myself in his armchair and warmed my hands before his crackling fire, for a sharp frost had set in, and the windows were thick with the ice crystals. "I suppose," I remarked, "that, homely as it looks, this thing has some deadly story linked on to it--that it is the clue which will guide you in the solution of some mystery and the punishment of some crime."\
\
"No, no. No crime," said Sherlock Holmes, laughing. "Only one of those whimsical little incidents which will happen when you have four million human beings all jostling each other within the space of a few square miles. Amid the action and reaction of so dense a swarm of humanity, every possible combination of events may be expected to take place, and many a little problem will be presented which may be striking and bizarre without being criminal. We have already had experience of such."\
\
"So much so," I remarked, "that of the last six cases which I have added to my notes, three have been entirely free of any legal crime."\
\
"Precisely. You allude to my attempt to recover the Irene Adler papers, to the singular case of Miss Mary Sutherland, and to the adventure of the man with the twisted lip. Well, I have no doubt that this small matter will fall into the same innocent category. You know Peterson, the commissionaire?"\
\
"Yes."\
\
"It is to him that this trophy belongs."\
\
"It is his hat."\
\
"No, no, he found it. Its owner is unknown. I beg that you will look upon it not as a battered billycock but as an intellectual problem. And, first, as to how it came here. It arrived upon Christmas morning, in company with a good fat goose, which is, I have no doubt, roasting at this moment in front of Peterson's fire. The facts are these: about four o'clock on Christmas morning, Peterson, who, as you know, is a very honest fellow, was returning from some small jollification and was making his way homeward down Tottenham Court Road. In front of him he saw, in the gaslight, a tallish man, walking with a slight stagger, and carrying a white goose slung over his shoulder. As he reached the corner of Goodge Street, a row broke out between this stranger and a little knot of roughs. One of the latter knocked off the man's hat, on which he raised his stick to defend himself and, swinging it over his head, smashed the shop window behind him. Peterson had rushed forward to protect the stranger from his assailants; but the man, shocked at having broken the window, and seeing an official-looking person in uniform rushing towards him, dropped his goose, took to his heels, and vanished amid the labyrinth of small streets which lie at the back of Tottenham Court Road. The roughs had also fled at the appearance of Peterson, so that he was left in possession of the field of battle, and also of the spoils of victory in the shape of this battered hat and a most unimpeachable Christmas goose."\
\
"Which surely he restored to their owner?"\
\
"My dear fellow, there lies the problem. It is true that 'For Mrs. Henry Baker' was printed upon a small card which was tied to the bird's left leg, and it is also true that the initials 'H. B.' are legible upon the lining of this hat, but as there are some thousands of Bakers, and some hundreds of Henry Bakers in this city of ours, it is not easy to restore lost property to any one of them."\
\
"What, then, did Peterson do?"\
\
"He brought round both hat and goose to me on Christmas morning, knowing that even the smallest problems are of interest to me. The goose we retained until this morning, when there were signs that, in spite of the slight frost, it would be well that it should be eaten without unnecessary delay. Its finder has carried it off, therefore, to fulfil the ultimate destiny of a goose, while I continue to retain the hat of the unknown gentleman who lost his Christmas dinner."\
\
"Did he not advertise?"\
\
"No."\
\
"Then, what clue could you have as to his identity?"\
\
"Only as much as we can deduce."\
\
"From his hat?"\
\
"Precisely."\
\
"But you are joking. What can you gather from this old battered felt?"\
\
"Here is my lens. You know my methods. What can you gather yourself as to the individuality of the man who has worn this article?"\
\
I took the tattered object in my hands and turned it over rather ruefully. It was a very ordinary black hat of the usual round shape, hard and much the worse for wear. The lining had been of red silk, but was a good deal discoloured. There was no maker's name; but, as Holmes had remarked, the initials "H. B." were scrawled upon one side. It was pierced in the brim for a hat-securer, but the elastic was missing. For the rest, it was cracked, exceedingly dusty, and spotted in several places, although there seemed to have been some attempt to hide the discoloured patches by smearing them with ink.\
\
"I can see nothing," said I, handing it back to my friend.\
\
"On the contrary, Watson, you can see everything. You fail, however, to reason from what you see. You are too timid in drawing your inferences."\
\
"Then, pray tell me what it is that you can infer from this hat?"\
\
He picked it up and gazed at it in the peculiar introspective fashion which was characteristic of him. "It is perhaps less suggestive than it might have been," he remarked, "and yet there are a few inferences which are very distinct, and a few others which represent at least a strong balance of probability. That the man was highly intellectual is of course obvious upon the face of it, and also that he was fairly well-to-do within the last three years, although he has now fallen upon evil days. He had foresight, but has less now than formerly, pointing to a moral retrogression, which, when taken with the decline of his fortunes, seems to indicate some evil influence, probably drink, at work upon him. This may account also for the obvious fact that his wife has ceased to love him."\
\
"My dear Holmes!"\
\
"He has, however, retained some degree of self-respect," he continued, disregarding my remonstrance. "He is a man who leads a sedentary life, goes out little, is out of training entirely, is middle-aged, has grizzled hair which he has had cut within the last few days, and which he anoints with lime-cream. These are the more patent facts which are to be deduced from his hat. Also, by the way, that it is extremely improbable that he has gas laid on in his house."\
\
"You are certainly joking, Holmes."\
\
"Not in the least. Is it possible that even now, when I give you these results, you are unable to see how they are attained?"\
\
"I have no doubt that I am very stupid, but I must confess that I am unable to follow you. For example, how did you deduce that this man was intellectual?"\
\
For answer Holmes clapped the hat upon his head. It came right over the forehead and settled upon the bridge of his nose. "It is a question of cubic capacity," said he; "a man with so large a brain must have something in it."\
\
"The decline of his fortunes, then?"\
\
"This hat is three years old. These flat brims curled at the edge came in then. It is a hat of the very best quality. Look at the band of ribbed silk and the excellent lining. If this man could afford to buy so expensive a hat three years ago, and has had no hat since, then he has assuredly gone down in the world."\
\
"Well, that is clear enough, certainly. But how about the foresight and the moral retrogression?"\
\
Sherlock Holmes laughed. "Here is the foresight," said he putting his finger upon the little disc and loop of the hat-securer. "They are never sold upon hats. If this man ordered one, it is a sign of a certain amount of foresight, since he went out of his way to take this precaution against the wind. But since we see that he has broken the elastic and has not troubled to replace it, it is obvious that he has less foresight now than formerly, which is a distinct proof of a weakening nature. On the other hand, he has endeavoured to conceal some of these stains upon the felt by daubing them with ink, which is a sign that he has not entirely lost his self-respect."\
\
"Your reasoning is certainly plausible."\
\
"The further points, that he is middle-aged, that his hair is grizzled, that it has been recently cut, and that he uses lime-cream, are all to be gathered from a close examination of the lower part of the lining. The lens discloses a large number of hair-ends, clean cut by the scissors of the barber. They all appear to be adhesive, and there is a distinct odour of lime-cream. This dust, you will observe, is not the gritty, grey dust of the street but the fluffy brown dust of the house, showing that it has been hung up indoors most of the time, while the marks of moisture upon the inside are proof positive that the wearer perspired very freely, and could therefore, hardly be in the best of training."\
\
"But his wife--you said that she had ceased to love him."\
\
"This hat has not been brushed for weeks. When I see you, my dear Watson, with a week's accumulation of dust upon your hat, and when your wife allows you to go out in such a state, I shall fear that you also have been unfortunate enough to lose your wife's affection."\
\
"But he might be a bachelor."\
\
"Nay, he was bringing home the goose as a peace-offering to his wife. Remember the card upon the bird's leg."\
\
"You have an answer to everything. But how on earth do you deduce that the gas is not laid on in his house?"\
\
"One tallow stain, or even two, might come by chance; but when I see no less than five, I think that there can be little doubt that the individual must be brought into frequent contact with burning tallow--walks upstairs at night probably with his hat in one hand and a guttering candle in the other. Anyhow, he never got tallow-stains from a gas-jet. Are you satisfied?"\
\
"Well, it is very ingenious," said I, laughing; "but since, as you said just now, there has been no crime committed, and no harm done save the loss of a goose, all this seems to be rather a waste of energy."\
\
Sherlock Holmes had opened his mouth to reply, when the door flew open, and Peterson, the commissionaire, rushed into the apartment with flushed cheeks and the face of a man who is dazed with astonishment.\
\
"The goose, Mr. Holmes! The goose, sir!" he gasped.\
\
"Eh? What of it, then? Has it returned to life and flapped off through the kitchen window?" Holmes twisted himself round upon the sofa to get a fairer view of the man's excited face.\
\
"See here, sir! See what my wife found in its crop!" He held out his hand and displayed upon the centre of the palm a brilliantly scintillating blue stone, rather smaller than a bean in size, but of such purity and radiance that it twinkled like an electric point in the dark hollow of his hand.\
\
Sherlock Holmes sat up with a whistle. "By Jove, Peterson!" said he, "this is treasure trove indeed. I suppose you know what you have got?"\
\
"A diamond, sir? A precious stone. It cuts into glass as though it were putty."\
\
"It's more than a precious stone. It is the precious stone."\
\
"Not the Countess of Morcar's blue carbuncle!" I ejaculated.\
\
"Precisely so. I ought to know its size and shape, seeing that I have read the advertisement about it in The Times every day lately. It is absolutely unique, and its value can only be conjectured, but the reward offered of $1000 is certainly not within a twentieth part of the market price."\
\
"A thousand pounds! Great Lord of mercy!" The commissionaire plumped down into a chair and stared from one to the other of us.\
\
"That is the reward, and I have reason to know that there are sentimental considerations in the background which would induce the Countess to part with half her fortune if she could but recover the gem."\
\
"It was lost, if I remember aright, at the Hotel Cosmopolitan," I remarked.\
\
"Precisely so, on December 22nd, just five days ago. John Horner, a plumber, was accused of having abstracted it from the lady's jewel-case. The evidence against him was so strong that the case has been referred to the Assizes. I have some account of the matter here, I believe." He rummaged amid his newspapers, glancing over the dates, until at last he smoothed one out, doubled it over, and read the following paragraph:\
\
"Hotel Cosmopolitan Jewel Robbery. John Horner, 26, plumber, was brought up upon the charge of having upon the 22nd inst., abstracted from the jewel-case of the Countess of Morcar the valuable gem known as the blue carbuncle. James Ryder, upper-attendant at the hotel, gave his evidence to the effect that he had shown Horner up to the dressing-room of the Countess of Morcar upon the day of the robbery in order that he might solder the second bar of the grate, which was loose. He had remained with Horner some little time, but had finally been called away. On returning, he found that Horner had disappeared, that the bureau had been forced open, and that the small morocco casket in which, as it afterwards transpired, the Countess was accustomed to keep her jewel, was lying empty upon the dressing-table. Ryder instantly gave the alarm, and Horner was arrested the same evening; but the stone could not be found either upon his person or in his rooms. Catherine Cusack, maid to the Countess, deposed to having heard Ryder's cry of dismay on discovering the robbery, and to having rushed into the room, where she found matters as described by the last witness. Inspector Bradstreet, B division, gave evidence as to the arrest of Horner, who struggled frantically, and protested his innocence in the strongest terms. Evidence of a previous conviction for robbery having been given against the prisoner, the magistrate refused to deal summarily with the offence, but referred it to the Assizes. Horner, who had shown signs of intense emotion during the proceedings, fainted away at the conclusion and was carried out of court."\
\
"Hum! So much for the police-court," said Holmes thoughtfully, tossing aside the paper. "The question for us now to solve is the sequence of events leading from a rifled jewel-case at one end to the crop of a goose in Tottenham Court Road at the other. You see, Watson, our little deductions have suddenly assumed a much more important and less innocent aspect. Here is the stone; the stone came from the goose, and the goose came from Mr. Henry Baker, the gentleman with the bad hat and all the other characteristics with which I have bored you. So now we must set ourselves very seriously to finding this gentleman and ascertaining what part he has played in this little mystery. To do this, we must try the simplest means first, and these lie undoubtedly in an advertisement in all the evening papers. If this fail, I shall have recourse to other methods."\
\
"What will you say?"\
\
"Give me a pencil and that slip of paper. Now, then: 'Found at the corner of Goodge Street, a goose and a black felt hat. Mr. Henry Baker can have the same by applying at 6:30 this evening at 221B, Baker Street.' That is clear and concise."\
\
"Very. But will he see it?"\
\
"Well, he is sure to keep an eye on the papers, since, to a poor man, the loss was a heavy one. He was clearly so scared by his mischance in breaking the window and by the approach of Peterson that he thought of nothing but flight, but since then he must have bitterly regretted the impulse which caused him to drop his bird. Then, again, the introduction of his name will cause him to see it, for everyone who knows him will direct his attention to it. Here you are, Peterson, run down to the advertising agency and have this put in the evening papers."\
\
"In which, sir?"\
\
"Oh, in the Globe, Star, Pall Mall, St. James's, Evening News, Standard, Echo, and any others that occur to you."\
\
"Very well, sir. And this stone?"\
\
"Ah, yes, I shall keep the stone. Thank you. And, I say, Peterson, just buy a goose on your way back and leave it here with me, for we must have one to give to this gentleman in place of the one which your family is now devouring."\
\
When the commissionaire had gone, Holmes took up the stone and held it against the light. "It's a bonny thing," said he. "Just see how it glints and sparkles. Of course it is a nucleus and focus of crime. Every good stone is. They are the devil's pet baits. In the larger and older jewels every facet may stand for a bloody deed. This stone is not yet twenty years old. It was found in the banks of the Amoy River in southern China and is remarkable in having every characteristic of the carbuncle, save that it is blue in shade instead of ruby red. In spite of its youth, it has already a sinister history. There have been two murders, a vitriol-throwing, a suicide, and several robberies brought about for the sake of this forty-grain weight of crystallised charcoal. Who would think that so pretty a toy would be a purveyor to the gallows and the prison? I'll lock it up in my strong box now and drop a line to the Countess to say that we have it."\
\
"Do you think that this man Horner is innocent?"\
\
"I cannot tell."\
\
"Well, then, do you imagine that this other one, Henry Baker, had anything to do with the matter?"\
\
"It is, I think, much more likely that Henry Baker is an absolutely innocent man, who had no idea that the bird which he was carrying was of considerably more value than if it were made of solid gold. That, however, I shall determine by a very simple test if we have an answer to our advertisement."\
\
"And you can do nothing until then?"\
\
"Nothing."\
\
"In that case I shall continue my professional round. But I shall come back in the evening at the hour you have mentioned, for I should like to see the solution of so tangled a business."\
\
"Very glad to see you. I dine at seven. There is a woodcock, I believe. By the way, in view of recent occurrences, perhaps I ought to ask Mrs. Hudson to examine its crop."\
\
I had been delayed at a case, and it was a little after half-past six when I found myself in Baker Street once more. As I approached the house I saw a tall man in a Scotch bonnet with a coat which was buttoned up to his chin waiting outside in the bright semicircle which was thrown from the fanlight. Just as I arrived the door was opened, and we were shown up together to Holmes' room.\
\
"Mr. Henry Baker, I believe," said he, rising from his armchair and greeting his visitor with the easy air of geniality which he could so readily assume. "Pray take this chair by the fire, Mr. Baker. It is a cold night, and I observe that your circulation is more adapted for summer than for winter. Ah, Watson, you have just come at the right time. Is that your hat, Mr. Baker?"\
\
"Yes, sir, that is undoubtedly my hat."\
\
He was a large man with rounded shoulders, a massive head, and a broad, intelligent face, sloping down to a pointed beard of grizzled brown. A touch of red in nose and cheeks, with a slight tremor of his extended hand, recalled Holmes' surmise as to his habits. His rusty black frock-coat was buttoned right up in front, with the collar turned up, and his lank wrists protruded from his sleeves without a sign of cuff or shirt. He spoke in a slow staccato fashion, choosing his words with care, and gave the impression generally of a man of learning and letters who had had ill-usage at the hands of fortune.\
\
"We have retained these things for some days," said Holmes, "because we expected to see an advertisement from you giving your address. I am at a loss to know now why you did not advertise."\
\
Our visitor gave a rather shamefaced laugh. "Shillings have not been so plentiful with me as they once were," he remarked. "I had no doubt that the gang of roughs who assaulted me had carried off both my hat and the bird. I did not care to spend more money in a hopeless attempt at recovering them."\
\
"Very naturally. By the way, about the bird, we were compelled to eat it."\
\
"To eat it!" Our visitor half rose from his chair in his excitement.\
\
"Yes, it would have been of no use to anyone had we not done so. But I presume that this other goose upon the sideboard, which is about the same weight and perfectly fresh, will answer your purpose equally well?"\
\
"Oh, certainly, certainly," answered Mr. Baker with a sigh of relief.\
\
"Of course, we still have the feathers, legs, crop, and so on of your own bird, so if you wish--"\
\
The man burst into a hearty laugh. "They might be useful to me as relics of my adventure," said he, "but beyond that I can hardly see what use the disjecta membra of my late acquaintance are going to be to me. No, sir, I think that, with your permission, I will confine my attentions to the excellent bird which I perceive upon the sideboard."\
\
Sherlock Holmes glanced sharply across at me with a slight shrug of his shoulders.\
\
"There is your hat, then, and there your bird," said he. "By the way, would it bore you to tell me where you got the other one from? I am somewhat of a fowl fancier, and I have seldom seen a better grown goose."\
\
"Certainly, sir," said Baker, who had risen and tucked his newly gained property under his arm. "There are a few of us who frequent the Alpha Inn, near the Museum--we are to be found in the Museum itself during the day, you understand. This year our good host, Windigate by name, instituted a goose club, by which, on consideration of some few pence every week, we were each to receive a bird at Christmas. My pence were duly paid, and the rest is familiar to you. I am much indebted to you, sir, for a Scotch bonnet is fitted neither to my years nor my gravity." With a comical pomposity of manner he bowed solemnly to both of us and strode off upon his way.\
\
"So much for Mr. Henry Baker," said Holmes when he had closed the door behind him. "It is quite certain that he knows nothing whatever about the matter. Are you hungry, Watson?"\
\
"Not particularly."\
\
"Then I suggest that we turn our dinner into a supper and follow up this clue while it is still hot."\
\
"By all means."\
\
It was a bitter night, so we drew on our ulsters and wrapped cravats about our throats. Outside, the stars were shining coldly in a cloudless sky, and the breath of the passers-by blew out into smoke like so many pistol shots. Our footfalls rang out crisply and loudly as we swung through the doctors' quarter, Wimpole Street, Harley Street, and so through Wigmore Street into Oxford Street. In a quarter of an hour we were in Bloomsbury at the Alpha Inn, which is a small public-house at the corner of one of the streets which runs down into Holborn. Holmes pushed open the door of the private bar and ordered two glasses of beer from the ruddy-faced, white-aproned landlord.\
\
"Your beer should be excellent if it is as good as your geese," said he.\
\
"My geese!" The man seemed surprised.\
\
"Yes. I was speaking only half an hour ago to Mr. Henry Baker, who was a member of your goose club."\
\
"Ah! yes, I see. But you see, sir, them's not our geese."\
\
"Indeed! Whose, then?"\
\
"Well, I got the two dozen from a salesman in Covent Garden."\
\
"Indeed? I know some of them. Which was it?"\
\
"Breckinridge is his name."\
\
"Ah! I don't know him. Well, here's your good health landlord, and prosperity to your house. Good-night."\
\
"Now for Mr. Breckinridge," he continued, buttoning up his coat as we came out into the frosty air. "Remember, Watson that though we have so homely a thing as a goose at one end of this chain, we have at the other a man who will certainly get seven years' penal servitude unless we can establish his innocence. It is possible that our inquiry may but confirm his guilt; but, in any case, we have a line of investigation which has been missed by the police, and which a singular chance has placed in our hands. Let us follow it out to the bitter end. Faces to the south, then, and quick march!"\
\
We passed across Holborn, down Endell Street, and so through a zigzag of slums to Covent Garden Market. One of the largest stalls bore the name of Breckinridge upon it, and the proprietor a horsey-looking man, with a sharp face and trim side-whiskers was helping a boy to put up the shutters.\
\
"Good-evening. It's a cold night," said Holmes.\
\
The salesman nodded and shot a questioning glance at my companion.\
\
"Sold out of geese, I see," continued Holmes, pointing at the bare slabs of marble.\
\
"Let you have five hundred to-morrow morning."\
\
"That's no good."\
\
"Well, there are some on the stall with the gas-flare."\
\
"Ah, but I was recommended to you."\
\
"Who by?"\
\
"The landlord of the Alpha."\
\
"Oh, yes; I sent him a couple of dozen."\
\
"Fine birds they were, too. Now where did you get them from?"\
\
To my surprise the question provoked a burst of anger from the salesman.\
\
"Now, then, mister," said he, with his head cocked and his arms akimbo, "what are you driving at? Let's have it straight, now."\
\
"It is straight enough. I should like to know who sold you the geese which you supplied to the Alpha."\
\
"Well then, I shan't tell you. So now!"\
\
"Oh, it is a matter of no importance; but I don't know why you should be so warm over such a trifle."\
\
"Warm! You'd be as warm, maybe, if you were as pestered as I am. When I pay good money for a good article there should be an end of the business; but it's 'Where are the geese?' and 'Who did you sell the geese to?' and 'What will you take for the geese?' One would think they were the only geese in the world, to hear the fuss that is made over them."\
\
"Well, I have no connection with any other people who have been making inquiries," said Holmes carelessly. "If you won't tell us the bet is off, that is all. But I'm always ready to back my opinion on a matter of fowls, and I have a fiver on it that the bird I ate is country bred."\
\
"Well, then, you've lost your fiver, for it's town bred," snapped the salesman.\
\
"It's nothing of the kind."\
\
"I say it is."\
\
"I don't believe it."\
\
"D'you think you know more about fowls than I, who have handled them ever since I was a nipper? I tell you, all those birds that went to the Alpha were town bred."\
\
"You'll never persuade me to believe that."\
\
"Will you bet, then?"\
\
"It's merely taking your money, for I know that I am right. But I'll have a sovereign on with you, just to teach you not to be obstinate."\
\
The salesman chuckled grimly. "Bring me the books, Bill," said he.\
\
The small boy brought round a small thin volume and a great greasy-backed one, laying them out together beneath the hanging lamp.\
\
"Now then, Mr. Cocksure," said the salesman, "I thought that I was out of geese, but before I finish you'll find that there is still one left in my shop. You see this little book?"\
\
"Well?"\
\
"That's the list of the folk from whom I buy. D'you see? Well, then, here on this page are the country folk, and the numbers after their names are where their accounts are in the big ledger. Now, then! You see this other page in red ink? Well, that is a list of my town suppliers. Now, look at that third name. Just read it out to me."\
\
"Mrs. Oakshott, 117, Brixton Road--249," read Holmes.\
\
"Quite so. Now turn that up in the ledger."\
\
Holmes turned to the page indicated. "Here you are, 'Mrs. Oakshott, 117, Brixton Road, egg and poultry supplier.' "\
\
"Now, then, what's the last entry?"\
\
" 'December 22nd. Twenty-four geese at 7s. 6d.' "\
\
"Quite so. There you are. And underneath?"\
\
" 'Sold to Mr. Windigate of the Alpha, at 12s.' "\
\
"What have you to say now?"\
\
Sherlock Holmes looked deeply chagrined. He drew a sovereign from his pocket and threw it down upon the slab, turning away with the air of a man whose disgust is too deep for words. A few yards off he stopped under a lamp-post and laughed in the hearty, noiseless fashion which was peculiar to him.\
\
"When you see a man with whiskers of that cut and the 'Pink 'un' protruding out of his pocket, you can always draw him by a bet," said he. "I daresay that if I had put $100 down in front of him, that man would not have given me such complete information as was drawn from him by the idea that he was doing me on a wager. Well, Watson, we are, I fancy, nearing the end of our quest, and the only point which remains to be determined is whether we should go on to this Mrs. Oakshott to-night, or whether we should reserve it for to-morrow. It is clear from what that surly fellow said that there are others besides ourselves who are anxious about the matter, and I should--"\
\
His remarks were suddenly cut short by a loud hubbub which broke out from the stall which we had just left. Turning round we saw a little rat-faced fellow standing in the centre of the circle of yellow light which was thrown by the swinging lamp, while Breckinridge, the salesman, framed in the door of his stall, was shaking his fists fiercely at the cringing figure.\
\
"I've had enough of you and your geese," he shouted. "I wish you were all at the devil together. If you come pestering me any more with your silly talk I'll set the dog at you. You bring Mrs. Oakshott here and I'll answer her, but what have you to do with it? Did I buy the geese off you?"\
\
"No; but one of them was mine all the same," whined the little man.\
\
"Well, then, ask Mrs. Oakshott for it."\
\
"She told me to ask you."\
\
"Well, you can ask the King of Proosia, for all I care. I've had enough of it. Get out of this!" He rushed fiercely forward, and the inquirer flitted away into the darkness.\
\
"Ha! this may save us a visit to Brixton Road," whispered Holmes. "Come with me, and we will see what is to be made of this fellow." Striding through the scattered knots of people who lounged round the flaring stalls, my companion speedily overtook the little man and touched him upon the shoulder. He sprang round, and I could see in the gas-light that every vestige of colour had been driven from his face.\
\
"Who are you, then? What do you want?" he asked in a quavering voice.\
\
"You will excuse me," said Holmes blandly, "but I could not help overhearing the questions which you put to the salesman just now. I think that I could be of assistance to you."\
\
"You? Who are you? How could you know anything of the matter?"\
\
"My name is Sherlock Holmes. It is my business to know what other people don't know."\
\
"But you can know nothing of this?"\
\
"Excuse me, I know everything of it. You are endeavouring to trace some geese which were sold by Mrs. Oakshott, of Brixton Road, to a salesman named Breckinridge, by him in turn to Mr. Windigate, of the Alpha, and by him to his club, of which Mr. Henry Baker is a member."\
\
"Oh, sir, you are the very man whom I have longed to meet," cried the little fellow with outstretched hands and quivering fingers. "I can hardly explain to you how interested I am in this matter."\
\
Sherlock Holmes hailed a four-wheeler which was passing. "In that case we had better discuss it in a cosy room rather than in this wind-swept market-place," said he. "But pray tell me, before we go farther, who it is that I have the pleasure of assisting."\
\
The man hesitated for an instant. "My name is John Robinson," he answered with a sidelong glance.\
\
"No, no; the real name," said Holmes sweetly. "It is always awkward doing business with an alias."\
\
A flush sprang to the white cheeks of the stranger. "Well then," said he, "my real name is James Ryder."\
\
"Precisely so. Head attendant at the Hotel Cosmopolitan. Pray step into the cab, and I shall soon be able to tell you everything which you would wish to know."\
\
The little man stood glancing from one to the other of us with half-frightened, half-hopeful eyes, as one who is not sure whether he is on the verge of a windfall or of a catastrophe. Then he stepped into the cab, and in half an hour we were back in the sitting-room at Baker Street. Nothing had been said during our drive, but the high, thin breathing of our new companion, and the claspings and unclaspings of his hands, spoke of the nervous tension within him.\
\
"Here we are!" said Holmes cheerily as we filed into the room. "The fire looks very seasonable in this weather. You look cold, Mr. Ryder. Pray take the basket-chair. I will just put on my slippers before we settle this little matter of yours. Now, then! You want to know what became of those geese?"\
\
"Yes, sir."\
\
"Or rather, I fancy, of that goose. It was one bird, I imagine in which you were interested--white, with a black bar across the tail."\
\
Ryder quivered with emotion. "Oh, sir," he cried, "can you tell me where it went to?"\
\
"It came here."\
\
"Here?"\
\
"Yes, and a most remarkable bird it proved. I don't wonder that you should take an interest in it. It laid an egg after it was dead--the bonniest, brightest little blue egg that ever was seen. I have it here in my museum."\
\
Our visitor staggered to his feet and clutched the mantelpiece with his right hand. Holmes unlocked his strong-box and held up the blue carbuncle, which shone out like a star, with a cold, brilliant, many-pointed radiance. Ryder stood glaring with a drawn face, uncertain whether to claim or to disown it.\
\
"The game's up, Ryder," said Holmes quietly. "Hold up, man, or you'll be into the fire! Give him an arm back into his chair, Watson. He's not got blood enough to go in for felony with impunity. Give him a dash of brandy. So! Now he looks a little more human. What a shrimp it is, to be sure!"\
\
For a moment he had staggered and nearly fallen, but the brandy brought a tinge of colour into his cheeks, and he sat staring with frightened eyes at his accuser.\
\
"I have almost every link in my hands, and all the proofs which I could possibly need, so there is little which you need tell me. Still, that little may as well be cleared up to make the case complete. You had heard, Ryder, of this blue stone of the Countess of Morcar's?"\
\
"It was Catherine Cusack who told me of it," said he in a crackling voice.\
\
"I see--her ladyship's waiting-maid. Well, the temptation of sudden wealth so easily acquired was too much for you, as it has been for better men before you; but you were not very scrupulous in the means you used. It seems to me, Ryder, that there is the making of a very pretty villain in you. You knew that this man Horner, the plumber, had been concerned in some such matter before, and that suspicion would rest the more readily upon him. What did you do, then? You made some small job in my lady's room--you and your confederate Cusack--and you managed that he should be the man sent for. Then, when he had left, you rifled the jewel-case, raised the alarm, and had this unfortunate man arrested. You then--"\
\
Ryder threw himself down suddenly upon the rug and clutched at my companion's knees. "For God's sake, have mercy!" he shrieked. "Think of my father! Of my mother! It would break their hearts. I never went wrong before! I never will again. I swear it. I'll swear it on a Bible. Oh, don't bring it into court! For Christ's sake, don't!"\
\
"Get back into your chair!" said Holmes sternly. "It is very well to cringe and crawl now, but you thought little enough of this poor Horner in the dock for a crime of which he knew nothing."\
\
"I will fly, Mr. Holmes. I will leave the country, sir. Then the charge against him will break down."\
\
"Hum! We will talk about that. And now let us hear a true account of the next act. How came the stone into the goose, and how came the goose into the open market? Tell us the truth, for there lies your only hope of safety."\
\
Ryder passed his tongue over his parched lips. "I will tell you it just as it happened, sir," said he. "When Horner had been arrested, it seemed to me that it would be best for me to get away with the stone at once, for I did not know at what moment the police might not take it into their heads to search me and my room. There was no place about the hotel where it would be safe. I went out, as if on some commission, and I made for my sister's house. She had married a man named Oakshott, and lived in Brixton Road, where she fattened fowls for the market. All the way there every man I met seemed to me to be a policeman or a detective; and, for all that it was a cold night, the sweat was pouring down my face before I came to the Brixton Road. My sister asked me what was the matter, and why I was so pale; but I told her that I had been upset by the jewel robbery at the hotel. Then I went into the back yard and smoked a pipe and wondered what it would be best to do.\
\
"I had a friend once called Maudsley, who went to the bad, and has just been serving his time in Pentonville. One day he had met me, and fell into talk about the ways of thieves, and how they could get rid of what they stole. I knew that he would be true to me, for I knew one or two things about him; so I made up my mind to go right on to Kilburn, where he lived, and take him into my confidence. He would show me how to turn the stone into money. But how to get to him in safety? I thought of the agonies I had gone through in coming from the hotel. I might at any moment be seized and searched, and there would be the stone in my waistcoat pocket. I was leaning against the wall at the time and looking at the geese which were waddling about round my feet, and suddenly an idea came into my head which showed me how I could beat the best detective that ever lived.\
\
"My sister had told me some weeks before that I might have the pick of her geese for a Christmas present, and I knew that she was always as good as her word. I would take my goose now, and in it I would carry my stone to Kilburn. There was a little shed in the yard, and behind this I drove one of the birds--a fine big one, white, with a barred tail. I caught it, and prying its bill open, I thrust the stone down its throat as far as my finger could reach. The bird gave a gulp, and I felt the stone pass along its gullet and down into its crop. But the creature flapped and struggled, and out came my sister to know what was the matter. As I turned to speak to her the brute broke loose and fluttered off among the others.\
\
" 'Whatever were you doing with that bird, Jem?' says she.\
\
" 'Well,' said I, 'you said you'd give me one for Christmas, and I was feeling which was the fattest.'\
\
" 'Oh,' says she, 'we've set yours aside for you--Jem's bird, we call it. It's the big white one over yonder. There's twenty-six of them, which makes one for you, and one for us, and two dozen for the market.'\
\
" 'Thank you, Maggie,' says I; 'but if it is all the same to you, I'd rather have that one I was handling just now.'\
\
" 'The other is a good three pound heavier,' said she, 'and we fattened it expressly for you.'\
\
" 'Never mind. I'll have the other, and I'll take it now,' said I.\
\
" 'Oh, just as you like,' said she, a little huffed. 'Which is it you want, then?'\
\
" 'That white one with the barred tail, right in the middle of the flock.'\
\
" 'Oh, very well. Kill it and take it with you.'\
\
"Well, I did what she said, Mr. Holmes, and I carried the bird all the way to Kilburn. I told my pal what I had done, for he was a man that it was easy to tell a thing like that to. He laughed until he choked, and we got a knife and opened the goose. My heart turned to water, for there was no sign of the stone, and I knew that some terrible mistake had occurred. I left the bird, rushed back to my sister's, and hurried into the back yard. There was not a bird to be seen there.\
\
" 'Where are they all, Maggie?' I cried.\
\
" 'Gone to the dealer's, Jem.'\
\
" 'Which dealer's?'\
\
" 'Breckinridge, of Covent Garden.'\
\
" 'But was there another with a barred tail?' I asked, 'the same as the one I chose?'\
\
" 'Yes, Jem; there were two barred-tailed ones, and I could never tell them apart.'\
\
"Well, then, of course I saw it all, and I ran off as hard as my feet would carry me to this man Breckinridge; but he had sold the lot at once, and not one word would he tell me as to where they had gone. You heard him yourselves to-night. Well, he has always answered me like that. My sister thinks that I am going mad. Sometimes I think that I am myself. And now--and now I am myself a branded thief, without ever having touched the wealth for which I sold my character. God help me! God help me!" He burst into convulsive sobbing, with his face buried in his hands.\
\
There was a long silence, broken only by his heavy breathing and by the measured tapping of Sherlock Holmes' finger-tips upon the edge of the table. Then my friend rose and threw open the door.\
\
"Get out!" said he.\
\
"What, sir! Oh, Heaven bless you!"\
\
"No more words. Get out!"\
\
And no more words were needed. There was a rush, a clatter upon the stairs, the bang of a door, and the crisp rattle of running footfalls from the street.\
\
"After all, Watson," said Holmes, reaching up his hand for his clay pipe, "I am not retained by the police to supply their deficiencies. If Horner were in danger it would be another thing; but this fellow will not appear against him, and the case must collapse. I suppose that I am commuting a felony, but it is just possible that I am saving a soul. This fellow will not go wrong again; he is too terribly frightened. Send him to gaol now, and you make him a gaol-bird for life. Besides, it is the season of forgiveness. Chance has put in our way a most singular and whimsical problem, and its solution is its own reward. If you will have the goodness to touch the bell, Doctor, we will begin another investigation, in which, also a bird will be the chief feature."\
\
VIII.  THE ADVENTURE OF THE SPECKLED BAND\
\
\
On glancing over my notes of the seventy odd cases in which I have during the last eight years studied the methods of my friend Sherlock Holmes, I find many tragic, some comic, a large number merely strange, but none commonplace; for, working as he did rather for the love of his art than for the acquirement of wealth, he refused to associate himself with any investigation which did not tend towards the unusual, and even the fantastic. Of all these varied cases, however, I cannot recall any which presented more singular features than that which was associated with the well-known Surrey family of the Roylotts of Stoke Moran. The events in question occurred in the early days of my association with Holmes, when we were sharing rooms as bachelors in Baker Street. It is possible that I might have placed them upon record before, but a promise of secrecy was made at the time, from which I have only been freed during the last month by the untimely death of the lady to whom the pledge was given. It is perhaps as well that the facts should now come to light, for I have reasons to know that there are widespread rumours as to the death of Dr. Grimesby Roylott which tend to make the matter even more terrible than the truth.\
\
It was early in April in the year '83 that I woke one morning to find Sherlock Holmes standing, fully dressed, by the side of my bed. He was a late riser, as a rule, and as the clock on the mantelpiece showed me that it was only a quarter-past seven, I blinked up at him in some surprise, and perhaps just a little resentment, for I was myself regular in my habits.\
\
"Very sorry to knock you up, Watson," said he, "but it's the common lot this morning. Mrs. Hudson has been knocked up, she retorted upon me, and I on you."\
\
"What is it, then--a fire?"\
\
"No; a client. It seems that a young lady has arrived in a considerable state of excitement, who insists upon seeing me. She is waiting now in the sitting-room. Now, when young ladies wander about the metropolis at this hour of the morning, and knock sleepy people up out of their beds, I presume that it is something very pressing which they have to communicate. Should it prove to be an interesting case, you would, I am sure, wish to follow it from the outset. I thought, at any rate, that I should call you and give you the chance."\
\
"My dear fellow, I would not miss it for anything."\
\
I had no keener pleasure than in following Holmes in his professional investigations, and in admiring the rapid deductions, as swift as intuitions, and yet always founded on a logical basis with which he unravelled the problems which were submitted to him. I rapidly threw on my clothes and was ready in a few minutes to accompany my friend down to the sitting-room. A lady dressed in black and heavily veiled, who had been sitting in the window, rose as we entered.\
\
"Good-morning, madam," said Holmes cheerily. "My name is Sherlock Holmes. This is my intimate friend and associate, Dr. Watson, before whom you can speak as freely as before myself. Ha! I am glad to see that Mrs. Hudson has had the good sense to light the fire. Pray draw up to it, and I shall order you a cup of hot coffee, for I observe that you are shivering."\
\
"It is not cold which makes me shiver," said the woman in a low voice, changing her seat as requested.\
\
"What, then?"\
\
"It is fear, Mr. Holmes. It is terror." She raised her veil as she spoke, and we could see that she was indeed in a pitiable state of agitation, her face all drawn and grey, with restless frightened eyes, like those of some hunted animal. Her features and figure were those of a woman of thirty, but her hair was shot with premature grey, and her expression was weary and haggard. Sherlock Holmes ran her over with one of his quick, all-comprehensive glances.\
\
"You must not fear," said he soothingly, bending forward and patting her forearm. "We shall soon set matters right, I have no doubt. You have come in by train this morning, I see."\
\
"You know me, then?"\
\
"No, but I observe the second half of a return ticket in the palm of your left glove. You must have started early, and yet you had a good drive in a dog-cart, along heavy roads, before you reached the station."\
\
The lady gave a violent start and stared in bewilderment at my companion.\
\
"There is no mystery, my dear madam," said he, smiling. "The left arm of your jacket is spattered with mud in no less than seven places. The marks are perfectly fresh. There is no vehicle save a dog-cart which throws up mud in that way, and then only when you sit on the left-hand side of the driver."\
\
"Whatever your reasons may be, you are perfectly correct," said she. "I started from home before six, reached Leatherhead at twenty past, and came in by the first train to Waterloo. Sir, I can stand this strain no longer; I shall go mad if it continues. I have no one to turn to--none, save only one, who cares for me, and he, poor fellow, can be of little aid. I have heard of you, Mr. Holmes; I have heard of you from Mrs. Farintosh, whom you helped in the hour of her sore need. It was from her that I had your address. Oh, sir, do you not think that you could help me, too, and at least throw a little light through the dense darkness which surrounds me? At present it is out of my power to reward you for your services, but in a month or six weeks I shall be married, with the control of my own income, and then at least you shall not find me ungrateful."\
\
Holmes turned to his desk and, unlocking it, drew out a small case-book, which he consulted.\
\
"Farintosh," said he. "Ah yes, I recall the case; it was concerned with an opal tiara. I think it was before your time, Watson. I can only say, madam, that I shall be happy to devote the same care to your case as I did to that of your friend. As to reward, my profession is its own reward; but you are at liberty to defray whatever expenses I may be put to, at the time which suits you best. And now I beg that you will lay before us everything that may help us in forming an opinion upon the matter."\
\
"Alas!" replied our visitor, "the very horror of my situation lies in the fact that my fears are so vague, and my suspicions depend so entirely upon small points, which might seem trivial to another, that even he to whom of all others I have a right to look for help and advice looks upon all that I tell him about it as the fancies of a nervous woman. He does not say so, but I can read it from his soothing answers and averted eyes. But I have heard, Mr. Holmes, that you can see deeply into the manifold wickedness of the human heart. You may advise me how to walk amid the dangers which encompass me."\
\
"I am all attention, madam."\
\
"My name is Helen Stoner, and I am living with my stepfather, who is the last survivor of one of the oldest Saxon families in England, the Roylotts of Stoke Moran, on the western border of Surrey."\
\
Holmes nodded his head. "The name is familiar to me," said he.\
\
"The family was at one time among the richest in England, and the estates extended over the borders into Berkshire in the north, and Hampshire in the west. In the last century, however, four successive heirs were of a dissolute and wasteful disposition, and the family ruin was eventually completed by a gambler in the days of the Regency. Nothing was left save a few acres of ground, and the two-hundred-year-old house, which is itself crushed under a heavy mortgage. The last squire dragged out his existence there, living the horrible life of an aristocratic pauper; but his only son, my stepfather, seeing that he must adapt himself to the new conditions, obtained an advance from a relative, which enabled him to take a medical degree and went out to Calcutta, where, by his professional skill and his force of character, he established a large practice. In a fit of anger, however, caused by some robberies which had been perpetrated in the house, he beat his native butler to death and narrowly escaped a capital sentence. As it was, he suffered a long term of imprisonment and afterwards returned to England a morose and disappointed man.\
\
"When Dr. Roylott was in India he married my mother, Mrs. Stoner, the young widow of Major-General Stoner, of the Bengal Artillery. My sister Julia and I were twins, and we were only two years old at the time of my mother's re-marriage. She had a considerable sum of money--not less than $1000 a year--and this she bequeathed to Dr. Roylott entirely while we resided with him, with a provision that a certain annual sum should be allowed to each of us in the event of our marriage. Shortly after our return to England my mother died--she was killed eight years ago in a railway accident near Crewe. Dr. Roylott then abandoned his attempts to establish himself in practice in London and took us to live with him in the old ancestral house at Stoke Moran. The money which my mother had left was enough for all our wants, and there seemed to be no obstacle to our happiness.\
\
"But a terrible change came over our stepfather about this time. Instead of making friends and exchanging visits with our neighbours, who had at first been overjoyed to see a Roylott of Stoke Moran back in the old family seat, he shut himself up in his house and seldom came out save to indulge in ferocious quarrels with whoever might cross his path. Violence of temper approaching to mania has been hereditary in the men of the family, and in my stepfather's case it had, I believe, been intensified by his long residence in the tropics. A series of disgraceful brawls took place, two of which ended in the police-court, until at last he became the terror of the village, and the folks would fly at his approach, for he is a man of immense strength, and absolutely uncontrollable in his anger.\
\
"Last week he hurled the local blacksmith over a parapet into a stream, and it was only by paying over all the money which I could gather together that I was able to avert another public exposure. He had no friends at all save the wandering gipsies, and he would give these vagabonds leave to encamp upon the few acres of bramble-covered land which represent the family estate, and would accept in return the hospitality of their tents, wandering away with them sometimes for weeks on end. He has a passion also for Indian animals, which are sent over to him by a correspondent, and he has at this moment a cheetah and a baboon, which wander freely over his grounds and are feared by the villagers almost as much as their master.\
\
"You can imagine from what I say that my poor sister Julia and I had no great pleasure in our lives. No servant would stay with us, and for a long time we did all the work of the house. She was but thirty at the time of her death, and yet her hair had already begun to whiten, even as mine has."\
\
"Your sister is dead, then?"\
\
"She died just two years ago, and it is of her death that I wish to speak to you. You can understand that, living the life which I have described, we were little likely to see anyone of our own age and position. We had, however, an aunt, my mother's maiden sister, Miss Honoria Westphail, who lives near Harrow, and we were occasionally allowed to pay short visits at this lady's house. Julia went there at Christmas two years ago, and met there a half-pay major of marines, to whom she became engaged. My stepfather learned of the engagement when my sister returned and offered no objection to the marriage; but within a fortnight of the day which had been fixed for the wedding, the terrible event occurred which has deprived me of my only companion."\
\
Sherlock Holmes had been leaning back in his chair with his eyes closed and his head sunk in a cushion, but he half opened his lids now and glanced across at his visitor.\
\
"Pray be precise as to details," said he.\
\
"It is easy for me to be so, for every event of that dreadful time is seared into my memory. The manor-house is, as I have already said, very old, and only one wing is now inhabited. The bedrooms in this wing are on the ground floor, the sitting-rooms being in the central block of the buildings. Of these bedrooms the first is Dr. Roylott's, the second my sister's, and the third my own. There is no communication between them, but they all open out into the same corridor. Do I make myself plain?"\
\
"Perfectly so."\
\
"The windows of the three rooms open out upon the lawn. That fatal night Dr. Roylott had gone to his room early, though we knew that he had not retired to rest, for my sister was troubled by the smell of the strong Indian cigars which it was his custom to smoke. She left her room, therefore, and came into mine, where she sat for some time, chatting about her approaching wedding. At eleven o'clock she rose to leave me, but she paused at the door and looked back.\
\
" 'Tell me, Helen,' said she, 'have you ever heard anyone whistle in the dead of the night?'\
\
" 'Never,' said I.\
\
" 'I suppose that you could not possibly whistle, yourself, in your sleep?'\
\
" 'Certainly not. But why?'\
\
" 'Because during the last few nights I have always, about three in the morning, heard a low, clear whistle. I am a light sleeper, and it has awakened me. I cannot tell where it came from--perhaps from the next room, perhaps from the lawn. I thought that I would just ask you whether you had heard it.'\
\
" 'No, I have not. It must be those wretched gipsies in the plantation.'\
\
" 'Very likely. And yet if it were on the lawn, I wonder that you did not hear it also.'\
\
" 'Ah, but I sleep more heavily than you.'\
\
" 'Well, it is of no great consequence, at any rate.' She smiled back at me, closed my door, and a few moments later I heard her key turn in the lock."\
\
"Indeed," said Holmes. "Was it your custom always to lock yourselves in at night?"\
\
"Always."\
\
"And why?"\
\
"I think that I mentioned to you that the doctor kept a cheetah and a baboon. We had no feeling of security unless our doors were locked."\
\
"Quite so. Pray proceed with your statement."\
\
"I could not sleep that night. A vague feeling of impending misfortune impressed me. My sister and I, you will recollect, were twins, and you know how subtle are the links which bind two souls which are so closely allied. It was a wild night. The wind was howling outside, and the rain was beating and splashing against the windows. Suddenly, amid all the hubbub of the gale, there burst forth the wild scream of a terrified woman. I knew that it was my sister's voice. I sprang from my bed, wrapped a shawl round me, and rushed into the corridor. As I opened my door I seemed to hear a low whistle, such as my sister described, and a few moments later a clanging sound, as if a mass of metal had fallen. As I ran down the passage, my sister's door was unlocked, and revolved slowly upon its hinges. I stared at it horror-stricken, not knowing what was about to issue from it. By the light of the corridor-lamp I saw my sister appear at the opening, her face blanched with terror, her hands groping for help, her whole figure swaying to and fro like that of a drunkard. I ran to her and threw my arms round her, but at that moment her knees seemed to give way and she fell to the ground. She writhed as one who is in terrible pain, and her limbs were dreadfully convulsed. At first I thought that she had not recognised me, but as I bent over her she suddenly shrieked out in a voice which I shall never forget, 'Oh, my God! Helen! It was the band! The speckled band!' There was something else which she would fain have said, and she stabbed with her finger into the air in the direction of the doctor's room, but a fresh convulsion seized her and choked her words. I rushed out, calling loudly for my stepfather, and I met him hastening from his room in his dressing-gown. When he reached my sister's side she was unconscious, and though he poured brandy down her throat and sent for medical aid from the village, all efforts were in vain, for she slowly sank and died without having recovered her consciousness. Such was the dreadful end of my beloved sister."\
\
"One moment," said Holmes, "are you sure about this whistle and metallic sound? Could you swear to it?"\
\
"That was what the county coroner asked me at the inquiry. It is my strong impression that I heard it, and yet, among the crash of the gale and the creaking of an old house, I may possibly have been deceived."\
\
"Was your sister dressed?"\
\
"No, she was in her night-dress. In her right hand was found the charred stump of a match, and in her left a match-box."\
\
"Showing that she had struck a light and looked about her when the alarm took place. That is important. And what conclusions did the coroner come to?"\
\
"He investigated the case with great care, for Dr. Roylott's conduct had long been notorious in the county, but he was unable to find any satisfactory cause of death. My evidence showed that the door had been fastened upon the inner side, and the windows were blocked by old-fashioned shutters with broad iron bars, which were secured every night. The walls were carefully sounded, and were shown to be quite solid all round, and the flooring was also thoroughly examined, with the same result. The chimney is wide, but is barred up by four large staples. It is certain, therefore, that my sister was quite alone when she met her end. Besides, there were no marks of any violence upon her."\
\
"How about poison?"\
\
"The doctors examined her for it, but without success."\
\
"What do you think that this unfortunate lady died of, then?"\
\
"It is my belief that she died of pure fear and nervous shock, though what it was that frightened her I cannot imagine."\
\
"Were there gipsies in the plantation at the time?"\
\
"Yes, there are nearly always some there."\
\
"Ah, and what did you gather from this allusion to a band--a speckled band?"\
\
"Sometimes I have thought that it was merely the wild talk of delirium, sometimes that it may have referred to some band of people, perhaps to these very gipsies in the plantation. I do not know whether the spotted handkerchiefs which so many of them wear over their heads might have suggested the strange adjective which she used."\
\
Holmes shook his head like a man who is far from being satisfied.\
\
"These are very deep waters," said he; "pray go on with your narrative."\
\
"Two years have passed since then, and my life has been until lately lonelier than ever. A month ago, however, a dear friend, whom I have known for many years, has done me the honour to ask my hand in marriage. His name is Armitage--Percy Armitage--the second son of Mr. Armitage, of Crane Water, near Reading. My stepfather has offered no opposition to the match, and we are to be married in the course of the spring. Two days ago some repairs were started in the west wing of the building, and my bedroom wall has been pierced, so that I have had to move into the chamber in which my sister died, and to sleep in the very bed in which she slept. Imagine, then, my thrill of terror when last night, as I lay awake, thinking over her terrible fate, I suddenly heard in the silence of the night the low whistle which had been the herald of her own death. I sprang up and lit the lamp, but nothing was to be seen in the room. I was too shaken to go to bed again, however, so I dressed, and as soon as it was daylight I slipped down, got a dog-cart at the Crown Inn, which is opposite, and drove to Leatherhead, from whence I have come on this morning with the one object of seeing you and asking your advice."\
\
"You have done wisely," said my friend. "But have you told me all?"\
\
"Yes, all."\
\
"Miss Roylott, you have not. You are screening your stepfather."\
\
"Why, what do you mean?"\
\
For answer Holmes pushed back the frill of black lace which fringed the hand that lay upon our visitor's knee. Five little livid spots, the marks of four fingers and a thumb, were printed upon the white wrist.\
\
"You have been cruelly used," said Holmes.\
\
The lady coloured deeply and covered over her injured wrist. "He is a hard man," she said, "and perhaps he hardly knows his own strength."\
\
There was a long silence, during which Holmes leaned his chin upon his hands and stared into the crackling fire.\
\
"This is a very deep business," he said at last. "There are a thousand details which I should desire to know before I decide upon our course of action. Yet we have not a moment to lose. If we were to come to Stoke Moran to-day, would it be possible for us to see over these rooms without the knowledge of your stepfather?"\
\
"As it happens, he spoke of coming into town to-day upon some most important business. It is probable that he will be away all day, and that there would be nothing to disturb you. We have a housekeeper now, but she is old and foolish, and I could easily get her out of the way."\
\
"Excellent. You are not averse to this trip, Watson?"\
\
"By no means."\
\
"Then we shall both come. What are you going to do yourself?"\
\
"I have one or two things which I would wish to do now that I am in town. But I shall return by the twelve o'clock train, so as to be there in time for your coming."\
\
"And you may expect us early in the afternoon. I have myself some small business matters to attend to. Will you not wait and breakfast?"\
\
"No, I must go. My heart is lightened already since I have confided my trouble to you. I shall look forward to seeing you again this afternoon." She dropped her thick black veil over her face and glided from the room.\
\
"And what do you think of it all, Watson?" asked Sherlock Holmes, leaning back in his chair.\
\
"It seems to me to be a most dark and sinister business."\
\
"Dark enough and sinister enough."\
\
"Yet if the lady is correct in saying that the flooring and walls are sound, and that the door, window, and chimney are impassable, then her sister must have been undoubtedly alone when she met her mysterious end."\
\
"What becomes, then, of these nocturnal whistles, and what of the very peculiar words of the dying woman?"\
\
"I cannot think."\
\
"When you combine the ideas of whistles at night, the presence of a band of gipsies who are on intimate terms with this old doctor, the fact that we have every reason to believe that the doctor has an interest in preventing his stepdaughter's marriage, the dying allusion to a band, and, finally, the fact that Miss Helen Stoner heard a metallic clang, which might have been caused by one of those metal bars that secured the shutters falling back into its place, I think that there is good ground to think that the mystery may be cleared along those lines."\
\
"But what, then, did the gipsies do?"\
\
"I cannot imagine."\
\
"I see many objections to any such theory."\
\
"And so do I. It is precisely for that reason that we are going to Stoke Moran this day. I want to see whether the objections are fatal, or if they may be explained away. But what in the name of the devil!"\
\
The ejaculation had been drawn from my companion by the fact that our door had been suddenly dashed open, and that a huge man had framed himself in the aperture. His costume was a peculiar mixture of the professional and of the agricultural, having a black top-hat, a long frock-coat, and a pair of high gaiters, with a hunting-crop swinging in his hand. So tall was he that his hat actually brushed the cross bar of the doorway, and his breadth seemed to span it across from side to side. A large face, seared with a thousand wrinkles, burned yellow with the sun, and marked with every evil passion, was turned from one to the other of us, while his deep-set, bile-shot eyes, and his high, thin, fleshless nose, gave him somewhat the resemblance to a fierce old bird of prey.\
\
"Which of you is Holmes?" asked this apparition.\
\
"My name, sir; but you have the advantage of me," said my companion quietly.\
\
"I am Dr. Grimesby Roylott, of Stoke Moran."\
\
"Indeed, Doctor," said Holmes blandly. "Pray take a seat."\
\
"I will do nothing of the kind. My stepdaughter has been here. I have traced her. What has she been saying to you?"\
\
"It is a little cold for the time of the year," said Holmes.\
\
"What has she been saying to you?" screamed the old man furiously.\
\
"But I have heard that the crocuses promise well," continued my companion imperturbably.\
\
"Ha! You put me off, do you?" said our new visitor, taking a step forward and shaking his hunting-crop. "I know you, you scoundrel! I have heard of you before. You are Holmes, the meddler."\
\
My friend smiled.\
\
"Holmes, the busybody!"\
\
His smile broadened.\
\
"Holmes, the Scotland Yard Jack-in-office!"\
\
Holmes chuckled heartily. "Your conversation is most entertaining," said he. "When you go out close the door, for there is a decided draught."\
\
"I will go when I have said my say. Don't you dare to meddle with my affairs. I know that Miss Stoner has been here. I traced her! I am a dangerous man to fall foul of! See here." He stepped swiftly forward, seized the poker, and bent it into a curve with his huge brown hands.\
\
"See that you keep yourself out of my grip," he snarled, and hurling the twisted poker into the fireplace he strode out of the room.\
\
"He seems a very amiable person," said Holmes, laughing. "I am not quite so bulky, but if he had remained I might have shown him that my grip was not much more feeble than his own." As he spoke he picked up the steel poker and, with a sudden effort, straightened it out again.\
\
"Fancy his having the insolence to confound me with the official detective force! This incident gives zest to our investigation, however, and I only trust that our little friend will not suffer from her imprudence in allowing this brute to trace her. And now, Watson, we shall order breakfast, and afterwards I shall walk down to Doctors' Commons, where I hope to get some data which may help us in this matter."\
\
It was nearly one o'clock when Sherlock Holmes returned from his excursion. He held in his hand a sheet of blue paper, scrawled over with notes and figures.\
\
"I have seen the will of the deceased wife," said he. "To determine its exact meaning I have been obliged to work out the present prices of the investments with which it is concerned. The total income, which at the time of the wife's death was little short of $1100, is now, through the fall in agricultural prices, not more than $750. Each daughter can claim an income of $250, in case of marriage. It is evident, therefore, that if both girls had married, this beauty would have had a mere pittance, while even one of them would cripple him to a very serious extent. My morning's work has not been wasted, since it has proved that he has the very strongest motives for standing in the way of anything of the sort. And now, Watson, this is too serious for dawdling, especially as the old man is aware that we are interesting ourselves in his affairs; so if you are ready, we shall call a cab and drive to Waterloo. I should be very much obliged if you would slip your revolver into your pocket. An Eley's No. 2 is an excellent argument with gentlemen who can twist steel pokers into knots. That and a tooth-brush are, I think, all that we need."\
\
At Waterloo we were fortunate in catching a train for Leatherhead, where we hired a trap at the station inn and drove for four or five miles through the lovely Surrey lanes. It was a perfect day, with a bright sun and a few fleecy clouds in the heavens. The trees and wayside hedges were just throwing out their first green shoots, and the air was full of the pleasant smell of the moist earth. To me at least there was a strange contrast between the sweet promise of the spring and this sinister quest upon which we were engaged. My companion sat in the front of the trap, his arms folded, his hat pulled down over his eyes, and his chin sunk upon his breast, buried in the deepest thought. Suddenly, however, he started, tapped me on the shoulder, and pointed over the meadows.\
\
"Look there!" said he.\
\
A heavily timbered park stretched up in a gentle slope, thickening into a grove at the highest point. From amid the branches there jutted out the grey gables and high roof-tree of a very old mansion.\
\
"Stoke Moran?" said he.\
\
"Yes, sir, that be the house of Dr. Grimesby Roylott," remarked the driver.\
\
"There is some building going on there," said Holmes; "that is where we are going."\
\
"There's the village," said the driver, pointing to a cluster of roofs some distance to the left; "but if you want to get to the house, you'll find it shorter to get over this stile, and so by the foot-path over the fields. There it is, where the lady is walking."\
\
"And the lady, I fancy, is Miss Stoner," observed Holmes, shading his eyes. "Yes, I think we had better do as you suggest."\
\
We got off, paid our fare, and the trap rattled back on its way to Leatherhead.\
\
"I thought it as well," said Holmes as we climbed the stile, "that this fellow should think we had come here as architects, or on some definite business. It may stop his gossip. Good-afternoon, Miss Stoner. You see that we have been as good as our word."\
\
Our client of the morning had hurried forward to meet us with a face which spoke her joy. "I have been waiting so eagerly for you," she cried, shaking hands with us warmly. "All has turned out splendidly. Dr. Roylott has gone to town, and it is unlikely that he will be back before evening."\
\
"We have had the pleasure of making the doctor's acquaintance," said Holmes, and in a few words he sketched out what had occurred. Miss Stoner turned white to the lips as she listened.\
\
"Good heavens!" she cried, "he has followed me, then."\
\
"So it appears."\
\
"He is so cunning that I never know when I am safe from him. What will he say when he returns?"\
\
"He must guard himself, for he may find that there is someone more cunning than himself upon his track. You must lock yourself up from him to-night. If he is violent, we shall take you away to your aunt's at Harrow. Now, we must make the best use of our time, so kindly take us at once to the rooms which we are to examine."\
\
The building was of grey, lichen-blotched stone, with a high central portion and two curving wings, like the claws of a crab, thrown out on each side. In one of these wings the windows were broken and blocked with wooden boards, while the roof was partly caved in, a picture of ruin. The central portion was in little better repair, but the right-hand block was comparatively modern, and the blinds in the windows, with the blue smoke curling up from the chimneys, showed that this was where the family resided. Some scaffolding had been erected against the end wall, and the stone-work had been broken into, but there were no signs of any workmen at the moment of our visit. Holmes walked slowly up and down the ill-trimmed lawn and examined with deep attention the outsides of the windows.\
\
"This, I take it, belongs to the room in which you used to sleep, the centre one to your sister's, and the one next to the main building to Dr. Roylott's chamber?"\
\
"Exactly so. But I am now sleeping in the middle one."\
\
"Pending the alterations, as I understand. By the way, there does not seem to be any very pressing need for repairs at that end wall."\
\
"There were none. I believe that it was an excuse to move me from my room."\
\
"Ah! that is suggestive. Now, on the other side of this narrow wing runs the corridor from which these three rooms open. There are windows in it, of course?"\
\
"Yes, but very small ones. Too narrow for anyone to pass through."\
\
"As you both locked your doors at night, your rooms were unapproachable from that side. Now, would you have the kindness to go into your room and bar your shutters?"\
\
Miss Stoner did so, and Holmes, after a careful examination through the open window, endeavoured in every way to force the shutter open, but without success. There was no slit through which a knife could be passed to raise the bar. Then with his lens he tested the hinges, but they were of solid iron, built firmly into the massive masonry. "Hum!" said he, scratching his chin in some perplexity, "my theory certainly presents some difficulties. No one could pass these shutters if they were bolted. Well, we shall see if the inside throws any light upon the matter."\
\
A small side door led into the whitewashed corridor from which the three bedrooms opened. Holmes refused to examine the third chamber, so we passed at once to the second, that in which Miss Stoner was now sleeping, and in which her sister had met with her fate. It was a homely little room, with a low ceiling and a gaping fireplace, after the fashion of old country-houses. A brown chest of drawers stood in one corner, a narrow white-counterpaned bed in another, and a dressing-table on the left-hand side of the window. These articles, with two small wicker-work chairs, made up all the furniture in the room save for a square of Wilton carpet in the centre. The boards round and the panelling of the walls were of brown, worm-eaten oak, so old and discoloured that it may have dated from the original building of the house. Holmes drew one of the chairs into a corner and sat silent, while his eyes travelled round and round and up and down, taking in every detail of the apartment.\
\
"Where does that bell communicate with?" he asked at last pointing to a thick bell-rope which hung down beside the bed, the tassel actually lying upon the pillow.\
\
"It goes to the housekeeper's room."\
\
"It looks newer than the other things?"\
\
"Yes, it was only put there a couple of years ago."\
\
"Your sister asked for it, I suppose?"\
\
"No, I never heard of her using it. We used always to get what we wanted for ourselves."\
\
"Indeed, it seemed unnecessary to put so nice a bell-pull there. You will excuse me for a few minutes while I satisfy myself as to this floor." He threw himself down upon his face with his lens in his hand and crawled swiftly backward and forward, examining minutely the cracks between the boards. Then he did the same with the wood-work with which the chamber was panelled. Finally he walked over to the bed and spent some time in staring at it and in running his eye up and down the wall. Finally he took the bell-rope in his hand and gave it a brisk tug.\
\
"Why, it's a dummy," said he.\
\
"Won't it ring?"\
\
"No, it is not even attached to a wire. This is very interesting. You can see now that it is fastened to a hook just above where the little opening for the ventilator is."\
\
"How very absurd! I never noticed that before."\
\
"Very strange!" muttered Holmes, pulling at the rope. "There are one or two very singular points about this room. For example, what a fool a builder must be to open a ventilator into another room, when, with the same trouble, he might have communicated with the outside air!"\
\
"That is also quite modern," said the lady.\
\
"Done about the same time as the bell-rope?" remarked Holmes.\
\
"Yes, there were several little changes carried out about that time."\
\
"They seem to have been of a most interesting character--dummy bell-ropes, and ventilators which do not ventilate. With your permission, Miss Stoner, we shall now carry our researches into the inner apartment."\
\
Dr. Grimesby Roylott's chamber was larger than that of his step-daughter, but was as plainly furnished. A camp-bed, a small wooden shelf full of books, mostly of a technical character, an armchair beside the bed, a plain wooden chair against the wall, a round table, and a large iron safe were the principal things which met the eye. Holmes walked slowly round and examined each and all of them with the keenest interest.\
\
"What's in here?" he asked, tapping the safe.\
\
"My stepfather's business papers."\
\
"Oh! you have seen inside, then?"\
\
"Only once, some years ago. I remember that it was full of papers."\
\
"There isn't a cat in it, for example?"\
\
"No. What a strange idea!"\
\
"Well, look at this!" He took up a small saucer of milk which stood on the top of it.\
\
"No; we don't keep a cat. But there is a cheetah and a baboon."\
\
"Ah, yes, of course! Well, a cheetah is just a big cat, and yet a saucer of milk does not go very far in satisfying its wants, I daresay. There is one point which I should wish to determine." He squatted down in front of the wooden chair and examined the seat of it with the greatest attention.\
\
"Thank you. That is quite settled," said he, rising and putting his lens in his pocket. "Hullo! Here is something interesting!"\
\
The object which had caught his eye was a small dog lash hung on one corner of the bed. The lash, however, was curled upon itself and tied so as to make a loop of whipcord.\
\
"What do you make of that, Watson?"\
\
"It's a common enough lash. But I don't know why it should be tied."\
\
"That is not quite so common, is it? Ah, me! it's a wicked world, and when a clever man turns his brains to crime it is the worst of all. I think that I have seen enough now, Miss Stoner, and with your permission we shall walk out upon the lawn."\
\
I had never seen my friend's face so grim or his brow so dark as it was when we turned from the scene of this investigation. We had walked several times up and down the lawn, neither Miss Stoner nor myself liking to break in upon his thoughts before he roused himself from his reverie.\
\
"It is very essential, Miss Stoner," said he, "that you should absolutely follow my advice in every respect."\
\
"I shall most certainly do so."\
\
"The matter is too serious for any hesitation. Your life may depend upon your compliance."\
\
"I assure you that I am in your hands."\
\
"In the first place, both my friend and I must spend the night in your room."\
\
Both Miss Stoner and I gazed at him in astonishment.\
\
"Yes, it must be so. Let me explain. I believe that that is the village inn over there?"\
\
"Yes, that is the Crown."\
\
"Very good. Your windows would be visible from there?"\
\
"Certainly."\
\
"You must confine yourself to your room, on pretence of a headache, when your stepfather comes back. Then when you hear him retire for the night, you must open the shutters of your window, undo the hasp, put your lamp there as a signal to us, and then withdraw quietly with everything which you are likely to want into the room which you used to occupy. I have no doubt that, in spite of the repairs, you could manage there for one night."\
\
"Oh, yes, easily."\
\
"The rest you will leave in our hands."\
\
"But what will you do?"\
\
"We shall spend the night in your room, and we shall investigate the cause of this noise which has disturbed you."\
\
"I believe, Mr. Holmes, that you have already made up your mind," said Miss Stoner, laying her hand upon my companion's sleeve.\
\
"Perhaps I have."\
\
"Then, for pity's sake, tell me what was the cause of my sister's death."\
\
"I should prefer to have clearer proofs before I speak."\
\
"You can at least tell me whether my own thought is correct, and if she died from some sudden fright."\
\
"No, I do not think so. I think that there was probably some more tangible cause. And now, Miss Stoner, we must leave you for if Dr. Roylott returned and saw us our journey would be in vain. Good-bye, and be brave, for if you will do what I have told you, you may rest assured that we shall soon drive away the dangers that threaten you."\
\
Sherlock Holmes and I had no difficulty in engaging a bedroom and sitting-room at the Crown Inn. They were on the upper floor, and from our window we could command a view of the avenue gate, and of the inhabited wing of Stoke Moran Manor House. At dusk we saw Dr. Grimesby Roylott drive past, his huge form looming up beside the little figure of the lad who drove him. The boy had some slight difficulty in undoing the heavy iron gates, and we heard the hoarse roar of the doctor's voice and saw the fury with which he shook his clinched fists at him. The trap drove on, and a few minutes later we saw a sudden light spring up among the trees as the lamp was lit in one of the sitting-rooms.\
\
"Do you know, Watson," said Holmes as we sat together in the gathering darkness, "I have really some scruples as to taking you to-night. There is a distinct element of danger."\
\
"Can I be of assistance?"\
\
"Your presence might be invaluable."\
\
"Then I shall certainly come."\
\
"It is very kind of you."\
\
"You speak of danger. You have evidently seen more in these rooms than was visible to me."\
\
"No, but I fancy that I may have deduced a little more. I imagine that you saw all that I did."\
\
"I saw nothing remarkable save the bell-rope, and what purpose that could answer I confess is more than I can imagine."\
\
"You saw the ventilator, too?"\
\
"Yes, but I do not think that it is such a very unusual thing to have a small opening between two rooms. It was so small that a rat could hardly pass through."\
\
"I knew that we should find a ventilator before ever we came to Stoke Moran."\
\
"My dear Holmes!"\
\
"Oh, yes, I did. You remember in her statement she said that her sister could smell Dr. Roylott's cigar. Now, of course that suggested at once that there must be a communication between the two rooms. It could only be a small one, or it would have been remarked upon at the coroner's inquiry. I deduced a ventilator."\
\
"But what harm can there be in that?"\
\
"Well, there is at least a curious coincidence of dates. A ventilator is made, a cord is hung, and a lady who sleeps in the bed dies. Does not that strike you?"\
\
"I cannot as yet see any connection."\
\
"Did you observe anything very peculiar about that bed?"\
\
"No."\
\
"It was clamped to the floor. Did you ever see a bed fastened like that before?"\
\
"I cannot say that I have."\
\
"The lady could not move her bed. It must always be in the same relative position to the ventilator and to the rope--or so we may call it, since it was clearly never meant for a bell-pull."\
\
"Holmes," I cried, "I seem to see dimly what you are hinting at. We are only just in time to prevent some subtle and horrible crime."\
\
"Subtle enough and horrible enough. When a doctor does go wrong he is the first of criminals. He has nerve and he has knowledge. Palmer and Pritchard were among the heads of their profession. This man strikes even deeper, but I think, Watson, that we shall be able to strike deeper still. But we shall have horrors enough before the night is over; for goodness' sake let us have a quiet pipe and turn our minds for a few hours to something more cheerful."\
\
About nine o'clock the light among the trees was extinguished, and all was dark in the direction of the Manor House. Two hours passed slowly away, and then, suddenly, just at the stroke of eleven, a single bright light shone out right in front of us.\
\
"That is our signal," said Holmes, springing to his feet; "it comes from the middle window."\
\
As we passed out he exchanged a few words with the landlord, explaining that we were going on a late visit to an acquaintance, and that it was possible that we might spend the night there. A moment later we were out on the dark road, a chill wind blowing in our faces, and one yellow light twinkling in front of us through the gloom to guide us on our sombre errand.\
\
There was little difficulty in entering the grounds, for unrepaired breaches gaped in the old park wall. Making our way among the trees, we reached the lawn, crossed it, and were about to enter through the window when out from a clump of laurel bushes there darted what seemed to be a hideous and distorted child, who threw itself upon the grass with writhing limbs and then ran swiftly across the lawn into the darkness.\
\
"My God!" I whispered; "did you see it?"\
\
Holmes was for the moment as startled as I. His hand closed like a vice upon my wrist in his agitation. Then he broke into a low laugh and put his lips to my ear.\
\
"It is a nice household," he murmured. "That is the baboon."\
\
I had forgotten the strange pets which the doctor affected. There was a cheetah, too; perhaps we might find it upon our shoulders at any moment. I confess that I felt easier in my mind when, after following Holmes' example and slipping off my shoes, I found myself inside the bedroom. My companion noiselessly closed the shutters, moved the lamp onto the table, and cast his eyes round the room. All was as we had seen it in the daytime. Then creeping up to me and making a trumpet of his hand, he whispered into my ear again so gently that it was all that I could do to distinguish the words:\
\
"The least sound would be fatal to our plans."\
\
I nodded to show that I had heard.\
\
"We must sit without light. He would see it through the ventilator."\
\
I nodded again.\
\
"Do not go asleep; your very life may depend upon it. Have your pistol ready in case we should need it. I will sit on the side of the bed, and you in that chair."\
\
I took out my revolver and laid it on the corner of the table.\
\
Holmes had brought up a long thin cane, and this he placed upon the bed beside him. By it he laid the box of matches and the stump of a candle. Then he turned down the lamp, and we were left in darkness.\
\
How shall I ever forget that dreadful vigil? I could not hear a sound, not even the drawing of a breath, and yet I knew that my companion sat open-eyed, within a few feet of me, in the same state of nervous tension in which I was myself. The shutters cut off the least ray of light, and we waited in absolute darkness.\
\
From outside came the occasional cry of a night-bird, and once at our very window a long drawn catlike whine, which told us that the cheetah was indeed at liberty. Far away we could hear the deep tones of the parish clock, which boomed out every quarter of an hour. How long they seemed, those quarters! Twelve struck, and one and two and three, and still we sat waiting silently for whatever might befall.\
\
Suddenly there was the momentary gleam of a light up in the direction of the ventilator, which vanished immediately, but was succeeded by a strong smell of burning oil and heated metal. Someone in the next room had lit a dark-lantern. I heard a gentle sound of movement, and then all was silent once more, though the smell grew stronger. For half an hour I sat with straining ears. Then suddenly another sound became audible--a very gentle, soothing sound, like that of a small jet of steam escaping continually from a kettle. The instant that we heard it, Holmes sprang from the bed, struck a match, and lashed furiously with his cane at the bell-pull.\
\
"You see it, Watson?" he yelled. "You see it?"\
\
But I saw nothing. At the moment when Holmes struck the light I heard a low, clear whistle, but the sudden glare flashing into my weary eyes made it impossible for me to tell what it was at which my friend lashed so savagely. I could, however, see that his face was deadly pale and filled with horror and loathing. He had ceased to strike and was gazing up at the ventilator when suddenly there broke from the silence of the night the most horrible cry to which I have ever listened. It swelled up louder and louder, a hoarse yell of pain and fear and anger all mingled in the one dreadful shriek. They say that away down in the village, and even in the distant parsonage, that cry raised the sleepers from their beds. It struck cold to our hearts, and I stood gazing at Holmes, and he at me, until the last echoes of it had died away into the silence from which it rose.\
\
"What can it mean?" I gasped.\
\
"It means that it is all over," Holmes answered. "And perhaps, after all, it is for the best. Take your pistol, and we will enter Dr. Roylott's room."\
\
With a grave face he lit the lamp and led the way down the corridor. Twice he struck at the chamber door without any reply from within. Then he turned the handle and entered, I at his heels, with the cocked pistol in my hand.\
\
It was a singular sight which met our eyes. On the table stood a dark-lantern with the shutter half open, throwing a brilliant beam of light upon the iron safe, the door of which was ajar. Beside this table, on the wooden chair, sat Dr. Grimesby Roylott clad in a long grey dressing-gown, his bare ankles protruding beneath, and his feet thrust into red heelless Turkish slippers. Across his lap lay the short stock with the long lash which we had noticed during the day. His chin was cocked upward and his eyes were fixed in a dreadful, rigid stare at the corner of the ceiling. Round his brow he had a peculiar yellow band, with brownish speckles, which seemed to be bound tightly round his head. As we entered he made neither sound nor motion.\
\
"The band! the speckled band!" whispered Holmes.\
\
I took a step forward. In an instant his strange headgear began to move, and there reared itself from among his hair the squat diamond-shaped head and puffed neck of a loathsome serpent.\
\
"It is a swamp adder!" cried Holmes; "the deadliest snake in India. He has died within ten seconds of being bitten. Violence does, in truth, recoil upon the violent, and the schemer falls into the pit which he digs for another. Let us thrust this creature back into its den, and we can then remove Miss Stoner to some place of shelter and let the county police know what has happened."\
\
As he spoke he drew the dog-whip swiftly from the dead man's lap, and throwing the noose round the reptile's neck he drew it from its horrid perch and, carrying it at arm's length, threw it into the iron safe, which he closed upon it.\
\
Such are the true facts of the death of Dr. Grimesby Roylott, of Stoke Moran. It is not necessary that I should prolong a narrative which has already run to too great a length by telling how we broke the sad news to the terrified girl, how we conveyed her by the morning train to the care of her good aunt at Harrow, of how the slow process of official inquiry came to the conclusion that the doctor met his fate while indiscreetly playing with a dangerous pet. The little which I had yet to learn of the case was told me by Sherlock Holmes as we travelled back next day.\
\
"I had," said he, "come to an entirely erroneous conclusion which shows, my dear Watson, how dangerous it always is to reason from insufficient data. The presence of the gipsies, and the use of the word 'band,' which was used by the poor girl, no doubt, to explain the appearance which she had caught a hurried glimpse of by the light of her match, were sufficient to put me upon an entirely wrong scent. I can only claim the merit that I instantly reconsidered my position when, however, it became clear to me that whatever danger threatened an occupant of the room could not come either from the window or the door. My attention was speedily drawn, as I have already remarked to you, to this ventilator, and to the bell-rope which hung down to the bed. The discovery that this was a dummy, and that the bed was clamped to the floor, instantly gave rise to the suspicion that the rope was there as a bridge for something passing through the hole and coming to the bed. The idea of a snake instantly occurred to me, and when I coupled it with my knowledge that the doctor was furnished with a supply of creatures from India, I felt that I was probably on the right track. The idea of using a form of poison which could not possibly be discovered by any chemical test was just such a one as would occur to a clever and ruthless man who had had an Eastern training. The rapidity with which such a poison would take effect would also, from his point of view, be an advantage. It would be a sharp-eyed coroner, indeed, who could distinguish the two little dark punctures which would show where the poison fangs had done their work. Then I thought of the whistle. Of course he must recall the snake before the morning light revealed it to the victim. He had trained it, probably by the use of the milk which we saw, to return to him when summoned. He would put it through this ventilator at the hour that he thought best, with the certainty that it would crawl down the rope and land on the bed. It might or might not bite the occupant, perhaps she might escape every night for a week, but sooner or later she must fall a victim.\
\
"I had come to these conclusions before ever I had entered his room. An inspection of his chair showed me that he had been in the habit of standing on it, which of course would be necessary in order that he should reach the ventilator. The sight of the safe, the saucer of milk, and the loop of whipcord were enough to finally dispel any doubts which may have remained. The metallic clang heard by Miss Stoner was obviously caused by her stepfather hastily closing the door of his safe upon its terrible occupant. Having once made up my mind, you know the steps which I took in order to put the matter to the proof. I heard the creature hiss as I have no doubt that you did also, and I instantly lit the light and attacked it."\
\
"With the result of driving it through the ventilator."\
\
"And also with the result of causing it to turn upon its master at the other side. Some of the blows of my cane came home and roused its snakish temper, so that it flew upon the first person it saw. In this way I am no doubt indirectly responsible for Dr. Grimesby Roylott's death, and I cannot say that it is likely to weigh very heavily upon my conscience."\
\
IX.  THE ADVENTURE OF THE ENGINEER'S THUMB\
\
\
Of all the problems which have been submitted to my friend, Mr. Sherlock Holmes, for solution during the years of our intimacy, there were only two which I was the means of introducing to his notice--that of Mr. Hatherley's thumb, and that of Colonel Warburton's madness. Of these the latter may have afforded a finer field for an acute and original observer, but the other was so strange in its inception and so dramatic in its details that it may be the more worthy of being placed upon record, even if it gave my friend fewer openings for those deductive methods of reasoning by which he achieved such remarkable results. The story has, I believe, been told more than once in the newspapers, but, like all such narratives, its effect is much less striking when set forth en bloc in a single half-column of print than when the facts slowly evolve before your own eyes, and the mystery clears gradually away as each new discovery furnishes a step which leads on to the complete truth. At the time the circumstances made a deep impression upon me, and the lapse of two years has hardly served to weaken the effect.\
\
It was in the summer of '89, not long after my marriage, that the events occurred which I am now about to summarise. I had returned to civil practice and had finally abandoned Holmes in his Baker Street rooms, although I continually visited him and occasionally even persuaded him to forgo his Bohemian habits so far as to come and visit us. My practice had steadily increased, and as I happened to live at no very great distance from Paddington Station, I got a few patients from among the officials. One of these, whom I had cured of a painful and lingering disease, was never weary of advertising my virtues and of endeavouring to send me on every sufferer over whom he might have any influence.\
\
One morning, at a little before seven o'clock, I was awakened by the maid tapping at the door to announce that two men had come from Paddington and were waiting in the consulting-room. I dressed hurriedly, for I knew by experience that railway cases were seldom trivial, and hastened downstairs. As I descended, my old ally, the guard, came out of the room and closed the door tightly behind him.\
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"I've got him here," he whispered, jerking his thumb over his shoulder; "he's all right."\
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"What is it, then?" I asked, for his manner suggested that it was some strange creature which he had caged up in my room.\
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"It's a new patient," he whispered. "I thought I'd bring him round myself; then he couldn't slip away. There he is, all safe and sound. I must go now, Doctor; I have my dooties, just the same as you." And off he went, this trusty tout, without even giving me time to thank him.\
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I entered my consulting-room and found a gentleman seated by the table. He was quietly dressed in a suit of heather tweed with a soft cloth cap which he had laid down upon my books. Round one of his hands he had a handkerchief wrapped, which was mottled all over with bloodstains. He was young, not more than five-and-twenty, I should say, with a strong, masculine face; but he was exceedingly pale and gave me the impression of a man who was suffering from some strong agitation, which it took all his strength of mind to control.\
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"I am sorry to knock you up so early, Doctor," said he, "but I have had a very serious accident during the night. I came in by train this morning, and on inquiring at Paddington as to where I might find a doctor, a worthy fellow very kindly escorted me here. I gave the maid a card, but I see that she has left it upon the side-table."\
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I took it up and glanced at it. "Mr. Victor Hatherley, hydraulic engineer, 16A, Victoria Street (3rd floor)." That was the name, style, and abode of my morning visitor. "I regret that I have kept you waiting," said I, sitting down in my library-chair. "You are fresh from a night journey, I understand, which is in itself a monotonous occupation."\
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"Oh, my night could not be called monotonous," said he, and laughed. He laughed very heartily, with a high, ringing note, leaning back in his chair and shaking his sides. All my medical instincts rose up against that laugh.\
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"Stop it!" I cried; "pull yourself together!" and I poured out some water from a caraffe.\
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It was useless, however. He was off in one of those hysterical outbursts which come upon a strong nature when some great crisis is over and gone. Presently he came to himself once more, very weary and pale-looking.\
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"I have been making a fool of myself," he gasped.\
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"Not at all. Drink this." I dashed some brandy into the water, and the colour began to come back to his bloodless cheeks.\
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"That's better!" said he. "And now, Doctor, perhaps you would kindly attend to my thumb, or rather to the place where my thumb used to be."\
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He unwound the handkerchief and held out his hand. It gave even my hardened nerves a shudder to look at it. There were four protruding fingers and a horrid red, spongy surface where the thumb should have been. It had been hacked or torn right out from the roots.\
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"Good heavens!" I cried, "this is a terrible injury. It must have bled considerably."\
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"Yes, it did. I fainted when it was done, and I think that I must have been senseless for a long time. When I came to I found that it was still bleeding, so I tied one end of my handkerchief very tightly round the wrist and braced it up with a twig."\
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"Excellent! You should have been a surgeon."\
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"It is a question of hydraulics, you see, and came within my own province."\
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"This has been done," said I, examining the wound, "by a very heavy and sharp instrument."\
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"A thing like a cleaver," said he.\
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"An accident, I presume?"\
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"By no means."\
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"What! a murderous attack?"\
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"Very murderous indeed."\
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"You horrify me."\
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I sponged the wound, cleaned it, dressed it, and finally covered it over with cotton wadding and carbolised bandages. He lay back without wincing, though he bit his lip from time to time.\
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"How is that?" I asked when I had finished.\
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"Capital! Between your brandy and your bandage, I feel a new man. I was very weak, but I have had a good deal to go through."\
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"Perhaps you had better not speak of the matter. It is evidently trying to your nerves."\
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"Oh, no, not now. I shall have to tell my tale to the police; but, between ourselves, if it were not for the convincing evidence of this wound of mine, I should be surprised if they believed my statement, for it is a very extraordinary one, and I have not much in the way of proof with which to back it up; and, even if they believe me, the clues which I can give them are so vague that it is a question whether justice will be done."\
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"Ha!" cried I, "if it is anything in the nature of a problem which you desire to see solved, I should strongly recommend you to come to my friend, Mr. Sherlock Holmes, before you go to the official police."\
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"Oh, I have heard of that fellow," answered my visitor, "and I should be very glad if he would take the matter up, though of course I must use the official police as well. Would you give me an introduction to him?"\
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"I'll do better. I'll take you round to him myself."\
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"I should be immensely obliged to you."\
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"We'll call a cab and go together. We shall just be in time to have a little breakfast with him. Do you feel equal to it?"\
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"Yes; I shall not feel easy until I have told my story."\
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"Then my servant will call a cab, and I shall be with you in an instant." I rushed upstairs, explained the matter shortly to my wife, and in five minutes was inside a hansom, driving with my new acquaintance to Baker Street.\
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Sherlock Holmes was, as I expected, lounging about his sitting-room in his dressing-gown, reading the agony column of The Times and smoking his before-breakfast pipe, which was composed of all the plugs and dottles left from his smokes of the day before, all carefully dried and collected on the corner of the mantelpiece. He received us in his quietly genial fashion, ordered fresh rashers and eggs, and joined us in a hearty meal. When it was concluded he settled our new acquaintance upon the sofa, placed a pillow beneath his head, and laid a glass of brandy and water within his reach.\
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"It is easy to see that your experience has been no common one, Mr. Hatherley," said he. "Pray, lie down there and make yourself absolutely at home. Tell us what you can, but stop when you are tired and keep up your strength with a little stimulant."\
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"Thank you," said my patient. "but I have felt another man since the doctor bandaged me, and I think that your breakfast has completed the cure. I shall take up as little of your valuable time as possible, so I shall start at once upon my peculiar experiences."\
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Holmes sat in his big armchair with the weary, heavy-lidded expression which veiled his keen and eager nature, while I sat opposite to him, and we listened in silence to the strange story which our visitor detailed to us.\
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"You must know," said he, "that I am an orphan and a bachelor, residing alone in lodgings in London. By profession I am a hydraulic engineer, and I have had considerable experience of my work during the seven years that I was apprenticed to Venner & Matheson, the well-known firm, of Greenwich. Two years ago, having served my time, and having also come into a fair sum of money through my poor father's death, I determined to start in business for myself and took professional chambers in Victoria Street.\
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"I suppose that everyone finds his first independent start in business a dreary experience. To me it has been exceptionally so. During two years I have had three consultations and one small job, and that is absolutely all that my profession has brought me. My gross takings amount to $27 10s. Every day, from nine in the morning until four in the afternoon, I waited in my little den, until at last my heart began to sink, and I came to believe that I should never have any practice at all.\
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"Yesterday, however, just as I was thinking of leaving the office, my clerk entered to say there was a gentleman waiting who wished to see me upon business. He brought up a card, too, with the name of 'Colonel Lysander Stark' engraved upon it. Close at his heels came the colonel himself, a man rather over the middle size, but of an exceeding thinness. I do not think that I have ever seen so thin a man. His whole face sharpened away into nose and chin, and the skin of his cheeks was drawn quite tense over his outstanding bones. Yet this emaciation seemed to be his natural habit, and due to no disease, for his eye was bright, his step brisk, and his bearing assured. He was plainly but neatly dressed, and his age, I should judge, would be nearer forty than thirty.\
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" 'Mr. Hatherley?' said he, with something of a German accent. 'You have been recommended to me, Mr. Hatherley, as being a man who is not only proficient in his profession but is also discreet and capable of preserving a secret.'\
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"I bowed, feeling as flattered as any young man would at such an address. 'May I ask who it was who gave me so good a character?'\
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" 'Well, perhaps it is better that I should not tell you that just at this moment. I have it from the same source that you are both an orphan and a bachelor and are residing alone in London.'\
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" 'That is quite correct,' I answered; 'but you will excuse me if I say that I cannot see how all this bears upon my professional qualifications. I understand that it was on a professional matter that you wished to speak to me?'\
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" 'Undoubtedly so. But you will find that all I say is really to the point. I have a professional commission for you, but absolute secrecy is quite essential--absolute secrecy, you understand, and of course we may expect that more from a man who is alone than from one who lives in the bosom of his family.'\
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" 'If I promise to keep a secret,' said I, 'you may absolutely depend upon my doing so.'\
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"He looked very hard at me as I spoke, and it seemed to me that I had never seen so suspicious and questioning an eye.\
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" 'Do you promise, then?' said he at last.\
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" 'Yes, I promise.'\
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" 'Absolute and complete silence before, during, and after? No reference to the matter at all, either in word or writing?'\
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" 'I have already given you my word.'\
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" 'Very good.' He suddenly sprang up, and darting like lightning across the room he flung open the door. The passage outside was empty.\
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" 'That's all right,' said he, coming back. 'I know that clerks are sometimes curious as to their master's affairs. Now we can talk in safety.' He drew up his chair very close to mine and began to stare at me again with the same questioning and thoughtful look.\
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"A feeling of repulsion, and of something akin to fear had begun to rise within me at the strange antics of this fleshless man. Even my dread of losing a client could not restrain me from showing my impatience.\
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" 'I beg that you will state your business, sir,' said I; 'my time is of value.' Heaven forgive me for that last sentence, but the words came to my lips.\
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" 'How would fifty guineas for a night's work suit you?' he asked.\
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" 'Most admirably.'\
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" 'I say a night's work, but an hour's would be nearer the mark. I simply want your opinion about a hydraulic stamping machine which has got out of gear. If you show us what is wrong we shall soon set it right ourselves. What do you think of such a commission as that?'\
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" 'The work appears to be light and the pay munificent.'\
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" 'Precisely so. We shall want you to come to-night by the last train.'\
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" 'Where to?'\
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" 'To Eyford, in Berkshire. It is a little place near the borders of Oxfordshire, and within seven miles of Reading. There is a train from Paddington which would bring you there at about 11:15.'\
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" 'Very good.'\
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" 'I shall come down in a carriage to meet you.'\
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" 'There is a drive, then?'\
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" 'Yes, our little place is quite out in the country. It is a good seven miles from Eyford Station.'\
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" 'Then we can hardly get there before midnight. I suppose there would be no chance of a train back. I should be compelled to stop the night.'\
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" 'Yes, we could easily give you a shake-down.'\
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" 'That is very awkward. Could I not come at some more convenient hour?'\
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" 'We have judged it best that you should come late. It is to recompense you for any inconvenience that we are paying to you, a young and unknown man, a fee which would buy an opinion from the very heads of your profession. Still, of course, if you would like to draw out of the business, there is plenty of time to do so.'\
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"I thought of the fifty guineas, and of how very useful they would be to me. 'Not at all,' said I, 'I shall be very happy to accommodate myself to your wishes. I should like, however, to understand a little more clearly what it is that you wish me to do.'\
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" 'Quite so. It is very natural that the pledge of secrecy which we have exacted from you should have aroused your curiosity. I have no wish to commit you to anything without your having it all laid before you. I suppose that we are absolutely safe from eavesdroppers?'\
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" 'Entirely.'\
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" 'Then the matter stands thus. You are probably aware that fuller's-earth is a valuable product, and that it is only found in one or two places in England?'\
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" 'I have heard so.'\
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" 'Some little time ago I bought a small place--a very small place--within ten miles of Reading. I was fortunate enough to discover that there was a deposit of fuller's-earth in one of my fields. On examining it, however, I found that this deposit was a comparatively small one, and that it formed a link between two very much larger ones upon the right and left--both of them, however, in the grounds of my neighbours. These good people were absolutely ignorant that their land contained that which was quite as valuable as a gold-mine. Naturally, it was to my interest to buy their land before they discovered its true value, but unfortunately I had no capital by which I could do this. I took a few of my friends into the secret, however, and they suggested that we should quietly and secretly work our own little deposit and that in this way we should earn the money which would enable us to buy the neighbouring fields. This we have now been doing for some time, and in order to help us in our operations we erected a hydraulic press. This press, as I have already explained, has got out of order, and we wish your advice upon the subject. We guard our secret very jealously, however, and if it once became known that we had hydraulic engineers coming to our little house, it would soon rouse inquiry, and then, if the facts came out, it would be good-bye to any chance of getting these fields and carrying out our plans. That is why I have made you promise me that you will not tell a human being that you are going to Eyford to-night. I hope that I make it all plain?'\
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" 'I quite follow you,' said I. 'The only point which I could not quite understand was what use you could make of a hydraulic press in excavating fuller's-earth, which, as I understand, is dug out like gravel from a pit.'\
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" 'Ah!' said he carelessly, 'we have our own process. We compress the earth into bricks, so as to remove them without revealing what they are. But that is a mere detail. I have taken you fully into my confidence now, Mr. Hatherley, and I have shown you how I trust you.' He rose as he spoke. 'I shall expect you, then, at Eyford at 11:15.'\
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" 'I shall certainly be there.'\
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" 'And not a word to a soul.' He looked at me with a last long, questioning gaze, and then, pressing my hand in a cold, dank grasp, he hurried from the room.\
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"Well, when I came to think it all over in cool blood I was very much astonished, as you may both think, at this sudden commission which had been intrusted to me. On the one hand, of course, I was glad, for the fee was at least tenfold what I should have asked had I set a price upon my own services, and it was possible that this order might lead to other ones. On the other hand, the face and manner of my patron had made an unpleasant impression upon me, and I could not think that his explanation of the fuller's-earth was sufficient to explain the necessity for my coming at midnight, and his extreme anxiety lest I should tell anyone of my errand. However, I threw all fears to the winds, ate a hearty supper, drove to Paddington, and started off, having obeyed to the letter the injunction as to holding my tongue.\
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"At Reading I had to change not only my carriage but my station. However, I was in time for the last train to Eyford, and I reached the little dim-lit station after eleven o'clock. I was the only passenger who got out there, and there was no one upon the platform save a single sleepy porter with a lantern. As I passed out through the wicket gate, however, I found my acquaintance of the morning waiting in the shadow upon the other side. Without a word he grasped my arm and hurried me into a carriage, the door of which was standing open. He drew up the windows on either side, tapped on the wood-work, and away we went as fast as the horse could go."\
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"One horse?" interjected Holmes.\
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"Yes, only one."\
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"Did you observe the colour?"\
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"Yes, I saw it by the side-lights when I was stepping into the carriage. It was a chestnut."\
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"Tired-looking or fresh?"\
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"Oh, fresh and glossy."\
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"Thank you. I am sorry to have interrupted you. Pray continue your most interesting statement."\
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"Away we went then, and we drove for at least an hour. Colonel Lysander Stark had said that it was only seven miles, but I should think, from the rate that we seemed to go, and from the time that we took, that it must have been nearer twelve. He sat at my side in silence all the time, and I was aware, more than once when I glanced in his direction, that he was looking at me with great intensity. The country roads seem to be not very good in that part of the world, for we lurched and jolted terribly. I tried to look out of the windows to see something of where we were, but they were made of frosted glass, and I could make out nothing save the occasional bright blur of a passing light. Now and then I hazarded some remark to break the monotony of the journey, but the colonel answered only in monosyllables, and the conversation soon flagged. At last, however, the bumping of the road was exchanged for the crisp smoothness of a gravel-drive, and the carriage came to a stand. Colonel Lysander Stark sprang out, and, as I followed after him, pulled me swiftly into a porch which gaped in front of us. We stepped, as it were, right out of the carriage and into the hall, so that I failed to catch the most fleeting glance of the front of the house. The instant that I had crossed the threshold the door slammed heavily behind us, and I heard faintly the rattle of the wheels as the carriage drove away.\
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"It was pitch dark inside the house, and the colonel fumbled about looking for matches and muttering under his breath. Suddenly a door opened at the other end of the passage, and a long, golden bar of light shot out in our direction. It grew broader, and a woman appeared with a lamp in her hand, which she held above her head, pushing her face forward and peering at us. I could see that she was pretty, and from the gloss with which the light shone upon her dark dress I knew that it was a rich material. She spoke a few words in a foreign tongue in a tone as though asking a question, and when my companion answered in a gruff monosyllable she gave such a start that the lamp nearly fell from her hand. Colonel Stark went up to her, whispered something in her ear, and then, pushing her back into the room from whence she had come, he walked towards me again with the lamp in his hand.\
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" 'Perhaps you will have the kindness to wait in this room for a few minutes,' said he, throwing open another door. It was a quiet, little, plainly furnished room, with a round table in the centre, on which several German books were scattered. Colonel Stark laid down the lamp on the top of a harmonium beside the door. 'I shall not keep you waiting an instant,' said he, and vanished into the darkness.\
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"I glanced at the books upon the table, and in spite of my ignorance of German I could see that two of them were treatises on science, the others being volumes of poetry. Then I walked across to the window, hoping that I might catch some glimpse of the country-side, but an oak shutter, heavily barred, was folded across it. It was a wonderfully silent house. There was an old clock ticking loudly somewhere in the passage, but otherwise everything was deadly still. A vague feeling of uneasiness began to steal over me. Who were these German people, and what were they doing living in this strange, out-of-the-way place? And where was the place? I was ten miles or so from Eyford, that was all I knew, but whether north, south, east, or west I had no idea. For that matter, Reading, and possibly other large towns, were within that radius, so the place might not be so secluded, after all. Yet it was quite certain, from the absolute stillness, that we were in the country. I paced up and down the room, humming a tune under my breath to keep up my spirits and feeling that I was thoroughly earning my fifty-guinea fee.\
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"Suddenly, without any preliminary sound in the midst of the utter stillness, the door of my room swung slowly open. The woman was standing in the aperture, the darkness of the hall behind her, the yellow light from my lamp beating upon her eager and beautiful face. I could see at a glance that she was sick with fear, and the sight sent a chill to my own heart. She held up one shaking finger to warn me to be silent, and she shot a few whispered words of broken English at me, her eyes glancing back, like those of a frightened horse, into the gloom behind her.\
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" 'I would go,' said she, trying hard, as it seemed to me, to speak calmly; 'I would go. I should not stay here. There is no good for you to do.'\
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" 'But, madam,' said I, 'I have not yet done what I came for. I cannot possibly leave until I have seen the machine.'\
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" 'It is not worth your while to wait,' she went on. 'You can pass through the door; no one hinders.' And then, seeing that I smiled and shook my head, she suddenly threw aside her constraint and made a step forward, with her hands wrung together. 'For the love of Heaven!' she whispered, 'get away from here before it is too late!'\
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"But I am somewhat headstrong by nature, and the more ready to engage in an affair when there is some obstacle in the way. I thought of my fifty-guinea fee, of my wearisome journey, and of the unpleasant night which seemed to be before me. Was it all to go for nothing? Why should I slink away without having carried out my commission, and without the payment which was my due? This woman might, for all I knew, be a monomaniac. With a stout bearing, therefore, though her manner had shaken me more than I cared to confess, I still shook my head and declared my intention of remaining where I was. She was about to renew her entreaties when a door slammed overhead, and the sound of several footsteps was heard upon the stairs. She listened for an instant, threw up her hands with a despairing gesture, and vanished as suddenly and as noiselessly as she had come.\
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"The newcomers were Colonel Lysander Stark and a short thick man with a chinchilla beard growing out of the creases of his double chin, who was introduced to me as Mr. Ferguson.\
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" 'This is my secretary and manager,' said the colonel. 'By the way, I was under the impression that I left this door shut just now. I fear that you have felt the draught.'\
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" 'On the contrary,' said I, 'I opened the door myself because I felt the room to be a little close.'\
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"He shot one of his suspicious looks at me. 'Perhaps we had better proceed to business, then,' said he. 'Mr. Ferguson and I will take you up to see the machine.'\
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" 'I had better put my hat on, I suppose.'\
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" 'Oh, no, it is in the house.'\
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" 'What, you dig fuller's-earth in the house?'\
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" 'No, no. This is only where we compress it. But never mind that. All we wish you to do is to examine the machine and to let us know what is wrong with it.'\
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"We went upstairs together, the colonel first with the lamp, the fat manager and I behind him. It was a labyrinth of an old house, with corridors, passages, narrow winding staircases, and little low doors, the thresholds of which were hollowed out by the generations who had crossed them. There were no carpets and no signs of any furniture above the ground floor, while the plaster was peeling off the walls, and the damp was breaking through in green, unhealthy blotches. I tried to put on as unconcerned an air as possible, but I had not forgotten the warnings of the lady, even though I disregarded them, and I kept a keen eye upon my two companions. Ferguson appeared to be a morose and silent man, but I could see from the little that he said that he was at least a fellow-countryman.\
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"Colonel Lysander Stark stopped at last before a low door, which he unlocked. Within was a small, square room, in which the three of us could hardly get at one time. Ferguson remained outside, and the colonel ushered me in.\
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" 'We are now,' said he, 'actually within the hydraulic press, and it would be a particularly unpleasant thing for us if anyone were to turn it on. The ceiling of this small chamber is really the end of the descending piston, and it comes down with the force of many tons upon this metal floor. There are small lateral columns of water outside which receive the force, and which transmit and multiply it in the manner which is familiar to you. The machine goes readily enough, but there is some stiffness in the working of it, and it has lost a little of its force. Perhaps you will have the goodness to look it over and to show us how we can set it right.'\
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"I took the lamp from him, and I examined the machine very thoroughly. It was indeed a gigantic one, and capable of exercising enormous pressure. When I passed outside, however, and pressed down the levers which controlled it, I knew at once by the whishing sound that there was a slight leakage, which allowed a regurgitation of water through one of the side cylinders. An examination showed that one of the india-rubber bands which was round the head of a driving-rod had shrunk so as not quite to fill the socket along which it worked. This was clearly the cause of the loss of power, and I pointed it out to my companions, who followed my remarks very carefully and asked several practical questions as to how they should proceed to set it right. When I had made it clear to them, I returned to the main chamber of the machine and took a good look at it to satisfy my own curiosity. It was obvious at a glance that the story of the fuller's-earth was the merest fabrication, for it would be absurd to suppose that so powerful an engine could be designed for so inadequate a purpose. The walls were of wood, but the floor consisted of a large iron trough, and when I came to examine it I could see a crust of metallic deposit all over it. I had stooped and was scraping at this to see exactly what it was when I heard a muttered exclamation in German and saw the cadaverous face of the colonel looking down at me.\
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" 'What are you doing there?' he asked.\
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"I felt angry at having been tricked by so elaborate a story as that which he had told me. 'I was admiring your fuller's-earth,' said I; 'I think that I should be better able to advise you as to your machine if I knew what the exact purpose was for which it was used.'\
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"The instant that I uttered the words I regretted the rashness of my speech. His face set hard, and a baleful light sprang up in his grey eyes.\
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" 'Very well,' said he, 'you shall know all about the machine.' He took a step backward, slammed the little door, and turned the key in the lock. I rushed towards it and pulled at the handle, but it was quite secure, and did not give in the least to my kicks and shoves. 'Hullo!' I yelled. 'Hullo! Colonel! Let me out!'\
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"And then suddenly in the silence I heard a sound which sent my heart into my mouth. It was the clank of the levers and the swish of the leaking cylinder. He had set the engine at work. The lamp still stood upon the floor where I had placed it when examining the trough. By its light I saw that the black ceiling was coming down upon me, slowly, jerkily, but, as none knew better than myself, with a force which must within a minute grind me to a shapeless pulp. I threw myself, screaming, against the door, and dragged with my nails at the lock. I implored the colonel to let me out, but the remorseless clanking of the levers drowned my cries. The ceiling was only a foot or two above my head, and with my hand upraised I could feel its hard, rough surface. Then it flashed through my mind that the pain of my death would depend very much upon the position in which I met it. If I lay on my face the weight would come upon my spine, and I shuddered to think of that dreadful snap. Easier the other way, perhaps; and yet, had I the nerve to lie and look up at that deadly black shadow wavering down upon me? Already I was unable to stand erect, when my eye caught something which brought a gush of hope back to my heart.\
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"I have said that though the floor and ceiling were of iron, the walls were of wood. As I gave a last hurried glance around, I saw a thin line of yellow light between two of the boards, which broadened and broadened as a small panel was pushed backward. For an instant I could hardly believe that here was indeed a door which led away from death. The next instant I threw myself through, and lay half-fainting upon the other side. The panel had closed again behind me, but the crash of the lamp, and a few moments afterwards the clang of the two slabs of metal, told me how narrow had been my escape.\
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"I was recalled to myself by a frantic plucking at my wrist, and I found myself lying upon the stone floor of a narrow corridor, while a woman bent over me and tugged at me with her left hand, while she held a candle in her right. It was the same good friend whose warning I had so foolishly rejected.\
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" 'Come! come!' she cried breathlessly. 'They will be here in a moment. They will see that you are not there. Oh, do not waste the so-precious time, but come!'\
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"This time, at least, I did not scorn her advice. I staggered to my feet and ran with her along the corridor and down a winding stair. The latter led to another broad passage, and just as we reached it we heard the sound of running feet and the shouting of two voices, one answering the other from the floor on which we were and from the one beneath. My guide stopped and looked about her like one who is at her wit's end. Then she threw open a door which led into a bedroom, through the window of which the moon was shining brightly.\
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" 'It is your only chance,' said she. 'It is high, but it may be that you can jump it.'\
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"As she spoke a light sprang into view at the further end of the passage, and I saw the lean figure of Colonel Lysander Stark rushing forward with a lantern in one hand and a weapon like a butcher's cleaver in the other. I rushed across the bedroom, flung open the window, and looked out. How quiet and sweet and wholesome the garden looked in the moonlight, and it could not be more than thirty feet down. I clambered out upon the sill, but I hesitated to jump until I should have heard what passed between my saviour and the ruffian who pursued me. If she were ill-used, then at any risks I was determined to go back to her assistance. The thought had hardly flashed through my mind before he was at the door, pushing his way past her; but she threw her arms round him and tried to hold him back.\
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" 'Fritz! Fritz!' she cried in English, 'remember your promise after the last time. You said it should not be again. He will be silent! Oh, he will be silent!'\
\
" 'You are mad, Elise!' he shouted, struggling to break away from her. 'You will be the ruin of us. He has seen too much. Let me pass, I say!' He dashed her to one side, and, rushing to the window, cut at me with his heavy weapon. I had let myself go, and was hanging by the hands to the sill, when his blow fell. I was conscious of a dull pain, my grip loosened, and I fell into the garden below.\
\
"I was shaken but not hurt by the fall; so I picked myself up and rushed off among the bushes as hard as I could run, for I understood that I was far from being out of danger yet. Suddenly, however, as I ran, a deadly dizziness and sickness came over me. I glanced down at my hand, which was throbbing painfully, and then, for the first time, saw that my thumb had been cut off and that the blood was pouring from my wound. I endeavoured to tie my handkerchief round it, but there came a sudden buzzing in my ears, and next moment I fell in a dead faint among the rose-bushes.\
\
"How long I remained unconscious I cannot tell. It must have been a very long time, for the moon had sunk, and a bright morning was breaking when I came to myself. My clothes were all sodden with dew, and my coat-sleeve was drenched with blood from my wounded thumb. The smarting of it recalled in an instant all the particulars of my night's adventure, and I sprang to my feet with the feeling that I might hardly yet be safe from my pursuers. But to my astonishment, when I came to look round me, neither house nor garden were to be seen. I had been lying in an angle of the hedge close by the highroad, and just a little lower down was a long building, which proved, upon my approaching it, to be the very station at which I had arrived upon the previous night. Were it not for the ugly wound upon my hand, all that had passed during those dreadful hours might have been an evil dream.\
\
"Half dazed, I went into the station and asked about the morning train. There would be one to Reading in less than an hour. The same porter was on duty, I found, as had been there when I arrived. I inquired of him whether he had ever heard of Colonel Lysander Stark. The name was strange to him. Had he observed a carriage the night before waiting for me? No, he had not. Was there a police-station anywhere near? There was one about three miles off.\
\
"It was too far for me to go, weak and ill as I was. I determined to wait until I got back to town before telling my story to the police. It was a little past six when I arrived, so I went first to have my wound dressed, and then the doctor was kind enough to bring me along here. I put the case into your hands and shall do exactly what you advise."\
\
We both sat in silence for some little time after listening to this extraordinary narrative. Then Sherlock Holmes pulled down from the shelf one of the ponderous commonplace books in which he placed his cuttings.\
\
"Here is an advertisement which will interest you," said he. "It appeared in all the papers about a year ago. Listen to this: 'Lost, on the 9th inst., Mr. Jeremiah Hayling, aged twenty-six, a hydraulic engineer. Left his lodgings at ten o'clock at night, and has not been heard of since. Was dressed in,' etc., etc. Ha! That represents the last time that the colonel needed to have his machine overhauled, I fancy."\
\
"Good heavens!" cried my patient. "Then that explains what the girl said."\
\
"Undoubtedly. It is quite clear that the colonel was a cool and desperate man, who was absolutely determined that nothing should stand in the way of his little game, like those out-and-out pirates who will leave no survivor from a captured ship. Well, every moment now is precious, so if you feel equal to it we shall go down to Scotland Yard at once as a preliminary to starting for Eyford."\
\
Some three hours or so afterwards we were all in the train together, bound from Reading to the little Berkshire village. There were Sherlock Holmes, the hydraulic engineer, Inspector Bradstreet, of Scotland Yard, a plain-clothes man, and myself. Bradstreet had spread an ordnance map of the county out upon the seat and was busy with his compasses drawing a circle with Eyford for its centre.\
\
"There you are," said he. "That circle is drawn at a radius of ten miles from the village. The place we want must be somewhere near that line. You said ten miles, I think, sir."\
\
"It was an hour's good drive."\
\
"And you think that they brought you back all that way when you were unconscious?"\
\
"They must have done so. I have a confused memory, too, of having been lifted and conveyed somewhere."\
\
"What I cannot understand," said I, "is why they should have spared you when they found you lying fainting in the garden. Perhaps the villain was softened by the woman's entreaties."\
\
"I hardly think that likely. I never saw a more inexorable face in my life."\
\
"Oh, we shall soon clear up all that," said Bradstreet. "Well, I have drawn my circle, and I only wish I knew at what point upon it the folk that we are in search of are to be found."\
\
"I think I could lay my finger on it," said Holmes quietly.\
\
"Really, now!" cried the inspector, "you have formed your opinion! Come, now, we shall see who agrees with you. I say it is south, for the country is more deserted there."\
\
"And I say east," said my patient.\
\
"I am for west," remarked the plain-clothes man. "There are several quiet little villages up there."\
\
"And I am for north," said I, "because there are no hills there, and our friend says that he did not notice the carriage go up any."\
\
"Come," cried the inspector, laughing; "it's a very pretty diversity of opinion. We have boxed the compass among us. Who do you give your casting vote to?"\
\
"You are all wrong."\
\
"But we can't all be."\
\
"Oh, yes, you can. This is my point." He placed his finger in the centre of the circle. "This is where we shall find them."\
\
"But the twelve-mile drive?" gasped Hatherley.\
\
"Six out and six back. Nothing simpler. You say yourself that the horse was fresh and glossy when you got in. How could it be that if it had gone twelve miles over heavy roads?"\
\
"Indeed, it is a likely ruse enough," observed Bradstreet thoughtfully. "Of course there can be no doubt as to the nature of this gang."\
\
"None at all," said Holmes. "They are coiners on a large scale, and have used the machine to form the amalgam which has taken the place of silver."\
\
"We have known for some time that a clever gang was at work," said the inspector. "They have been turning out half-crowns by the thousand. We even traced them as far as Reading, but could get no farther, for they had covered their traces in a way that showed that they were very old hands. But now, thanks to this lucky chance, I think that we have got them right enough."\
\
But the inspector was mistaken, for those criminals were not destined to fall into the hands of justice. As we rolled into Eyford Station we saw a gigantic column of smoke which streamed up from behind a small clump of trees in the neighbourhood and hung like an immense ostrich feather over the landscape.\
\
"A house on fire?" asked Bradstreet as the train steamed off again on its way.\
\
"Yes, sir!" said the station-master.\
\
"When did it break out?"\
\
"I hear that it was during the night, sir, but it has got worse, and the whole place is in a blaze."\
\
"Whose house is it?"\
\
"Dr. Becher's."\
\
"Tell me," broke in the engineer, "is Dr. Becher a German, very thin, with a long, sharp nose?"\
\
The station-master laughed heartily. "No, sir, Dr. Becher is an Englishman, and there isn't a man in the parish who has a better-lined waistcoat. But he has a gentleman staying with him, a patient, as I understand, who is a foreigner, and he looks as if a little good Berkshire beef would do him no harm."\
\
The station-master had not finished his speech before we were all hastening in the direction of the fire. The road topped a low hill, and there was a great widespread whitewashed building in front of us, spouting fire at every chink and window, while in the garden in front three fire-engines were vainly striving to keep the flames under.\
\
"That's it!" cried Hatherley, in intense excitement. "There is the gravel-drive, and there are the rose-bushes where I lay. That second window is the one that I jumped from."\
\
"Well, at least," said Holmes, "you have had your revenge upon them. There can be no question that it was your oil-lamp which, when it was crushed in the press, set fire to the wooden walls, though no doubt they were too excited in the chase after you to observe it at the time. Now keep your eyes open in this crowd for your friends of last night, though I very much fear that they are a good hundred miles off by now."\
\
And Holmes' fears came to be realised, for from that day to this no word has ever been heard either of the beautiful woman, the sinister German, or the morose Englishman. Early that morning a peasant had met a cart containing several people and some very bulky boxes driving rapidly in the direction of Reading, but there all traces of the fugitives disappeared, and even Holmes' ingenuity failed ever to discover the least clue as to their whereabouts.\
\
The firemen had been much perturbed at the strange arrangements which they had found within, and still more so by discovering a newly severed human thumb upon a window-sill of the second floor. About sunset, however, their efforts were at last successful, and they subdued the flames, but not before the roof had fallen in, and the whole place been reduced to such absolute ruin that, save some twisted cylinders and iron piping, not a trace remained of the machinery which had cost our unfortunate acquaintance so dearly. Large masses of nickel and of tin were discovered stored in an out-house, but no coins were to be found, which may have explained the presence of those bulky boxes which have been already referred to.\
\
How our hydraulic engineer had been conveyed from the garden to the spot where he recovered his senses might have remained forever a mystery were it not for the soft mould, which told us a very plain tale. He had evidently been carried down by two persons, one of whom had remarkably small feet and the other unusually large ones. On the whole, it was most probable that the silent Englishman, being less bold or less murderous than his companion, had assisted the woman to bear the unconscious man out of the way of danger.\
\
"Well," said our engineer ruefully as we took our seats to return once more to London, "it has been a pretty business for me! I have lost my thumb and I have lost a fifty-guinea fee, and what have I gained?"\
\
"Experience," said Holmes, laughing. "Indirectly it may be of value, you know; you have only to put it into words to gain the reputation of being excellent company for the remainder of your existence."\
\
X.  THE ADVENTURE OF THE NOBLE BACHELOR\
\
\
The Lord St. Simon marriage, and its curious termination, have long ceased to be a subject of interest in those exalted circles in which the unfortunate bridegroom moves. Fresh scandals have eclipsed it, and their more piquant details have drawn the gossips away from this four-year-old drama. As I have reason to believe, however, that the full facts have never been revealed to the general public, and as my friend Sherlock Holmes had a considerable share in clearing the matter up, I feel that no memoir of him would be complete without some little sketch of this remarkable episode.\
\
It was a few weeks before my own marriage, during the days when I was still sharing rooms with Holmes in Baker Street, that he came home from an afternoon stroll to find a letter on the table waiting for him. I had remained indoors all day, for the weather had taken a sudden turn to rain, with high autumnal winds, and the Jezail bullet which I had brought back in one of my limbs as a relic of my Afghan campaign throbbed with dull persistence. With my body in one easy-chair and my legs upon another, I had surrounded myself with a cloud of newspapers until at last, saturated with the news of the day, I tossed them all aside and lay listless, watching the huge crest and monogram upon the envelope upon the table and wondering lazily who my friend's noble correspondent could be.\
\
"Here is a very fashionable epistle," I remarked as he entered. "Your morning letters, if I remember right, were from a fish-monger and a tide-waiter."\
\
"Yes, my correspondence has certainly the charm of variety," he answered, smiling, "and the humbler are usually the more interesting. This looks like one of those unwelcome social summonses which call upon a man either to be bored or to lie."\
\
He broke the seal and glanced over the contents.\
\
"Oh, come, it may prove to be something of interest, after all."\
\
"Not social, then?"\
\
"No, distinctly professional."\
\
"And from a noble client?"\
\
"One of the highest in England."\
\
"My dear fellow, I congratulate you."\
\
"I assure you, Watson, without affectation, that the status of my client is a matter of less moment to me than the interest of his case. It is just possible, however, that that also may not be wanting in this new investigation. You have been reading the papers diligently of late, have you not?"\
\
"It looks like it," said I ruefully, pointing to a huge bundle in the corner. "I have had nothing else to do."\
\
"It is fortunate, for you will perhaps be able to post me up. I read nothing except the criminal news and the agony column. The latter is always instructive. But if you have followed recent events so closely you must have read about Lord St. Simon and his wedding?"\
\
"Oh, yes, with the deepest interest."\
\
"That is well. The letter which I hold in my hand is from Lord St. Simon. I will read it to you, and in return you must turn over these papers and let me have whatever bears upon the matter. This is what he says:\
\
" 'MY DEAR MR. SHERLOCK HOLMES:--Lord Backwater tells me that I may place implicit reliance upon your judgment and discretion. I have determined, therefore, to call upon you and to consult you in reference to the very painful event which has occurred in connection with my wedding. Mr. Lestrade, of Scotland Yard, is acting already in the matter, but he assures me that he sees no objection to your co-operation, and that he even thinks that it might be of some assistance. I will call at four o'clock in the afternoon, and, should you have any other engagement at that time, I hope that you will postpone it, as this matter is of paramount importance. Yours faithfully,\
\
\
" 'ST. SIMON.'\
\
"It is dated from Grosvenor Mansions, written with a quill pen, and the noble lord has had the misfortune to get a smear of ink upon the outer side of his right little finger," remarked Holmes as he folded up the epistle.\
\
"He says four o'clock. It is three now. He will be here in an hour."\
\
"Then I have just time, with your assistance, to get clear upon the subject. Turn over those papers and arrange the extracts in their order of time, while I take a glance as to who our client is." He picked a red-covered volume from a line of books of reference beside the mantelpiece. "Here he is," said he, sitting down and flattening it out upon his knee. " 'Lord Robert Walsingham de Vere St. Simon, second son of the Duke of Balmoral.' Hum! 'Arms: Azure, three caltrops in chief over a fess sable. Born in 1846.' He's forty-one years of age, which is mature for marriage. Was Under-Secretary for the colonies in a late administration. The Duke, his father, was at one time Secretary for Foreign Affairs. They inherit Plantagenet blood by direct descent, and Tudor on the distaff side. Ha! Well, there is nothing very instructive in all this. I think that I must turn to you Watson, for something more solid."\
\
"I have very little difficulty in finding what I want," said I, "for the facts are quite recent, and the matter struck me as remarkable. I feared to refer them to you, however, as I knew that you had an inquiry on hand and that you disliked the intrusion of other matters."\
\
"Oh, you mean the little problem of the Grosvenor Square furniture van. That is quite cleared up now--though, indeed, it was obvious from the first. Pray give me the results of your newspaper selections."\
\
"Here is the first notice which I can find. It is in the personal column of the Morning Post, and dates, as you see, some weeks back: 'A marriage has been arranged,' it says, 'and will, if rumour is correct, very shortly take place, between Lord Robert St. Simon, second son of the Duke of Balmoral, and Miss Hatty Doran, the only daughter of Aloysius Doran. Esq., of San Francisco, Cal., U.S.A.' That is all."\
\
"Terse and to the point," remarked Holmes, stretching his long, thin legs towards the fire.\
\
"There was a paragraph amplifying this in one of the society papers of the same week. Ah, here it is: 'There will soon be a call for protection in the marriage market, for the present free-trade principle appears to tell heavily against our home product. One by one the management of the noble houses of Great Britain is passing into the hands of our fair cousins from across the Atlantic. An important addition has been made during the last week to the list of the prizes which have been borne away by these charming invaders. Lord St. Simon, who has shown himself for over twenty years proof against the little god's arrows, has now definitely announced his approaching marriage with Miss Hatty Doran, the fascinating daughter of a California millionaire. Miss Doran, whose graceful figure and striking face attracted much attention at the Westbury House festivities, is an only child, and it is currently reported that her dowry will run to considerably over the six figures, with expectancies for the future. As it is an open secret that the Duke of Balmoral has been compelled to sell his pictures within the last few years, and as Lord St. Simon has no property of his own save the small estate of Birchmoor, it is obvious that the Californian heiress is not the only gainer by an alliance which will enable her to make the easy and common transition from a Republican lady to a British peeress.' "\
\
"Anything else?" asked Holmes, yawning.\
\
"Oh, yes; plenty. Then there is another note in the Morning Post to say that the marriage would be an absolutely quiet one, that it would be at St. George's, Hanover Square, that only half a dozen intimate friends would be invited, and that the party would return to the furnished house at Lancaster Gate which has been taken by Mr. Aloysius Doran. Two days later--that is, on Wednesday last--there is a curt announcement that the wedding had taken place, and that the honeymoon would be passed at Lord Backwater's place, near Petersfield. Those are all the notices which appeared before the disappearance of the bride."\
\
"Before the what?" asked Holmes with a start.\
\
"The vanishing of the lady."\
\
"When did she vanish, then?"\
\
"At the wedding breakfast."\
\
"Indeed. This is more interesting than it promised to be; quite dramatic, in fact."\
\
"Yes; it struck me as being a little out of the common."\
\
"They often vanish before the ceremony, and occasionally during the honeymoon; but I cannot call to mind anything quite so prompt as this. Pray let me have the details."\
\
"I warn you that they are very incomplete."\
\
"Perhaps we may make them less so."\
\
"Such as they are, they are set forth in a single article of a morning paper of yesterday, which I will read to you. It is headed, 'Singular Occurrence at a Fashionable Wedding':\
\
" 'The family of Lord Robert St. Simon has been thrown into the greatest consternation by the strange and painful episodes which have taken place in connection with his wedding. The ceremony, as shortly announced in the papers of yesterday, occurred on the previous morning; but it is only now that it has been possible to confirm the strange rumours which have been so persistently floating about. In spite of the attempts of the friends to hush the matter up, so much public attention has now been drawn to it that no good purpose can be served by affecting to disregard what is a common subject for conversation.\
\
" 'The ceremony, which was performed at St. George's, Hanover Square, was a very quiet one, no one being present save the father of the bride, Mr. Aloysius Doran, the Duchess of Balmoral, Lord Backwater, Lord Eustace and Lady Clara St. Simon (the younger brother and sister of the bridegroom), and Lady Alicia Whittington. The whole party proceeded afterwards to the house of Mr. Aloysius Doran, at Lancaster Gate, where breakfast had been prepared. It appears that some little trouble was caused by a woman, whose name has not been ascertained, who endeavoured to force her way into the house after the bridal party, alleging that she had some claim upon Lord St. Simon. It was only after a painful and prolonged scene that she was ejected by the butler and the footman. The bride, who had fortunately entered the house before this unpleasant interruption, had sat down to breakfast with the rest, when she complained of a sudden indisposition and retired to her room. Her prolonged absence having caused some comment, her father followed her, but learned from her maid that she had only come up to her chamber for an instant, caught up an ulster and bonnet, and hurried down to the passage. One of the footmen declared that he had seen a lady leave the house thus apparelled, but had refused to credit that it was his mistress, believing her to be with the company. On ascertaining that his daughter had disappeared, Mr. Aloysius Doran, in conjunction with the bridegroom, instantly put themselves in communication with the police, and very energetic inquiries are being made, which will probably result in a speedy clearing up of this very singular business. Up to a late hour last night, however, nothing had transpired as to the whereabouts of the missing lady. There are rumours of foul play in the matter, and it is said that the police have caused the arrest of the woman who had caused the original disturbance, in the belief that, from jealousy or some other motive, she may have been concerned in the strange disappearance of the bride.' "\
\
"And is that all?"\
\
"Only one little item in another of the morning papers, but it is a suggestive one."\
\
"And it is--"\
\
"That Miss Flora Millar, the lady who had caused the disturbance, has actually been arrested. It appears that she was formerly a danseuse at the Allegro, and that she has known the bridegroom for some years. There are no further particulars, and the whole case is in your hands now--so far as it has been set forth in the public press."\
\
"And an exceedingly interesting case it appears to be. I would not have missed it for worlds. But there is a ring at the bell, Watson, and as the clock makes it a few minutes after four, I have no doubt that this will prove to be our noble client. Do not dream of going, Watson, for I very much prefer having a witness, if only as a check to my own memory."\
\
"Lord Robert St. Simon," announced our page-boy, throwing open the door. A gentleman entered, with a pleasant, cultured face, high-nosed and pale, with something perhaps of petulance about the mouth, and with the steady, well-opened eye of a man whose pleasant lot it had ever been to command and to be obeyed. His manner was brisk, and yet his general appearance gave an undue impression of age, for he had a slight forward stoop and a little bend of the knees as he walked. His hair, too, as he swept off his very curly-brimmed hat, was grizzled round the edges and thin upon the top. As to his dress, it was careful to the verge of foppishness, with high collar, black frock-coat, white waistcoat, yellow gloves, patent-leather shoes, and light-coloured gaiters. He advanced slowly into the room, turning his head from left to right, and swinging in his right hand the cord which held his golden eyeglasses.\
\
"Good-day, Lord St. Simon," said Holmes, rising and bowing. "Pray take the basket-chair. This is my friend and colleague, Dr. Watson. Draw up a little to the fire, and we will talk this matter over."\
\
"A most painful matter to me, as you can most readily imagine, Mr. Holmes. I have been cut to the quick. I understand that you have already managed several delicate cases of this sort, sir, though I presume that they were hardly from the same class of society."\
\
"No, I am descending."\
\
"I beg pardon."\
\
"My last client of the sort was a king."\
\
"Oh, really! I had no idea. And which king?"\
\
"The King of Scandinavia."\
\
"What! Had he lost his wife?"\
\
"You can understand," said Holmes suavely, "that I extend to the affairs of my other clients the same secrecy which I promise to you in yours."\
\
"Of course! Very right! very right! I'm sure I beg pardon. As to my own case, I am ready to give you any information which may assist you in forming an opinion."\
\
"Thank you. I have already learned all that is in the public prints, nothing more. I presume that I may take it as correct--this article, for example, as to the disappearance of the bride."\
\
Lord St. Simon glanced over it. "Yes, it is correct, as far as it goes."\
\
"But it needs a great deal of supplementing before anyone could offer an opinion. I think that I may arrive at my facts most directly by questioning you."\
\
"Pray do so."\
\
"When did you first meet Miss Hatty Doran?"\
\
"In San Francisco, a year ago."\
\
"You were travelling in the States?"\
\
"Yes."\
\
"Did you become engaged then?"\
\
"No."\
\
"But you were on a friendly footing?"\
\
"I was amused by her society, and she could see that I was amused."\
\
"Her father is very rich?"\
\
"He is said to be the richest man on the Pacific slope."\
\
"And how did he make his money?"\
\
"In mining. He had nothing a few years ago. Then he struck gold, invested it, and came up by leaps and bounds."\
\
"Now, what is your own impression as to the young lady's--your wife's character?"\
\
The nobleman swung his glasses a little faster and stared down into the fire. "You see, Mr. Holmes," said he, "my wife was twenty before her father became a rich man. During that time she ran free in a mining camp and wandered through woods or mountains, so that her education has come from Nature rather than from the schoolmaster. She is what we call in England a tomboy, with a strong nature, wild and free, unfettered by any sort of traditions. She is impetuous--volcanic, I was about to say. She is swift in making up her mind and fearless in carrying out her resolutions. On the other hand, I would not have given her the name which I have the honour to bear"--he gave a little stately cough--"had I not thought her to be at bottom a noble woman. I believe that she is capable of heroic self-sacrifice and that anything dishonourable would be repugnant to her."\
\
"Have you her photograph?"\
\
"I brought this with me." He opened a locket and showed us the full face of a very lovely woman. It was not a photograph but an ivory miniature, and the artist had brought out the full effect of the lustrous black hair, the large dark eyes, and the exquisite mouth. Holmes gazed long and earnestly at it. Then he closed the locket and handed it back to Lord St. Simon.\
\
"The young lady came to London, then, and you renewed your acquaintance?"\
\
"Yes, her father brought her over for this last London season. I met her several times, became engaged to her, and have now married her."\
\
"She brought, I understand, a considerable dowry?"\
\
"A fair dowry. Not more than is usual in my family."\
\
"And this, of course, remains to you, since the marriage is a fait accompli?"\
\
"I really have made no inquiries on the subject."\
\
"Very naturally not. Did you see Miss Doran on the day before the wedding?"\
\
"Yes."\
\
"Was she in good spirits?"\
\
"Never better. She kept talking of what we should do in our future lives."\
\
"Indeed! That is very interesting. And on the morning of the wedding?"\
\
"She was as bright as possible--at least until after the ceremony."\
\
"And did you observe any change in her then?"\
\
"Well, to tell the truth, I saw then the first signs that I had ever seen that her temper was just a little sharp. The incident however, was too trivial to relate and can have no possible bearing upon the case."\
\
"Pray let us have it, for all that."\
\
"Oh, it is childish. She dropped her bouquet as we went towards the vestry. She was passing the front pew at the time, and it fell over into the pew. There was a moment's delay, but the gentleman in the pew handed it up to her again, and it did not appear to be the worse for the fall. Yet when I spoke to her of the matter, she answered me abruptly; and in the carriage, on our way home, she seemed absurdly agitated over this trifling cause."\
\
"Indeed! You say that there was a gentleman in the pew. Some of the general public were present, then?"\
\
"Oh, yes. It is impossible to exclude them when the church is open."\
\
"This gentleman was not one of your wife's friends?"\
\
"No, no; I call him a gentleman by courtesy, but he was quite a common-looking person. I hardly noticed his appearance. But really I think that we are wandering rather far from the point."\
\
"Lady St. Simon, then, returned from the wedding in a less cheerful frame of mind than she had gone to it. What did she do on re-entering her father's house?"\
\
"I saw her in conversation with her maid."\
\
"And who is her maid?"\
\
"Alice is her name. She is an American and came from California with her."\
\
"A confidential servant?"\
\
"A little too much so. It seemed to me that her mistress allowed her to take great liberties. Still, of course, in America they look upon these things in a different way."\
\
"How long did she speak to this Alice?"\
\
"Oh, a few minutes. I had something else to think of."\
\
"You did not overhear what they said?"\
\
"Lady St. Simon said something about 'jumping a claim.' She was accustomed to use slang of the kind. I have no idea what she meant."\
\
"American slang is very expressive sometimes. And what did your wife do when she finished speaking to her maid?"\
\
"She walked into the breakfast-room."\
\
"On your arm?"\
\
"No, alone. She was very independent in little matters like that. Then, after we had sat down for ten minutes or so, she rose hurriedly, muttered some words of apology, and left the room. She never came back."\
\
"But this maid, Alice, as I understand, deposes that she went to her room, covered her bride's dress with a long ulster, put on a bonnet, and went out."\
\
"Quite so. And she was afterwards seen walking into Hyde Park in company with Flora Millar, a woman who is now in custody, and who had already made a disturbance at Mr. Doran's house that morning."\
\
"Ah, yes. I should like a few particulars as to this young lady, and your relations to her."\
\
Lord St. Simon shrugged his shoulders and raised his eyebrows. "We have been on a friendly footing for some years--I may say on a very friendly footing. She used to be at the Allegro. I have not treated her ungenerously, and she had no just cause of complaint against me, but you know what women are, Mr. Holmes. Flora was a dear little thing, but exceedingly hot-headed and devotedly attached to me. She wrote me dreadful letters when she heard that I was about to be married, and, to tell the truth, the reason why I had the marriage celebrated so quietly was that I feared lest there might be a scandal in the church. She came to Mr. Doran's door just after we returned, and she endeavoured to push her way in, uttering very abusive expressions towards my wife, and even threatening her, but I had foreseen the possibility of something of the sort, and I had two police fellows there in private clothes, who soon pushed her out again. She was quiet when she saw that there was no good in making a row."\
\
"Did your wife hear all this?"\
\
"No, thank goodness, she did not."\
\
"And she was seen walking with this very woman afterwards?"\
\
"Yes. That is what Mr. Lestrade, of Scotland Yard, looks upon as so serious. It is thought that Flora decoyed my wife out and laid some terrible trap for her."\
\
"Well, it is a possible supposition."\
\
"You think so, too?"\
\
"I did not say a probable one. But you do not yourself look upon this as likely?"\
\
"I do not think Flora would hurt a fly."\
\
"Still, jealousy is a strange transformer of characters. Pray what is your own theory as to what took place?"\
\
"Well, really, I came to seek a theory, not to propound one. I have given you all the facts. Since you ask me, however, I may say that it has occurred to me as possible that the excitement of this affair, the consciousness that she had made so immense a social stride, had the effect of causing some little nervous disturbance in my wife."\
\
"In short, that she had become suddenly deranged?"\
\
"Well, really, when I consider that she has turned her back--I will not say upon me, but upon so much that many have aspired to without success--I can hardly explain it in any other fashion."\
\
"Well, certainly that is also a conceivable hypothesis," said Holmes, smiling. "And now, Lord St. Simon, I think that I have nearly all my data. May I ask whether you were seated at the breakfast-table so that you could see out of the window?"\
\
"We could see the other side of the road and the Park."\
\
"Quite so. Then I do not think that I need to detain you longer. I shall communicate with you."\
\
"Should you be fortunate enough to solve this problem," said our client, rising.\
\
"I have solved it."\
\
"Eh? What was that?"\
\
"I say that I have solved it."\
\
"Where, then, is my wife?"\
\
"That is a detail which I shall speedily supply."\
\
Lord St. Simon shook his head. "I am afraid that it will take wiser heads than yours or mine," he remarked, and bowing in a stately, old-fashioned manner he departed.\
\
"It is very good of Lord St. Simon to honour my head by putting it on a level with his own," said Sherlock Holmes, laughing. "I think that I shall have a whisky and soda and a cigar after all this cross-questioning. I had formed my conclusions as to the case before our client came into the room."\
\
"My dear Holmes!"\
\
"I have notes of several similar cases, though none, as I remarked before, which were quite as prompt. My whole examination served to turn my conjecture into a certainty. Circumstantial evidence is occasionally very convincing, as when you find a trout in the milk, to quote Thoreau's example."\
\
"But I have heard all that you have heard."\
\
"Without, however, the knowledge of pre-existing cases which serves me so well. There was a parallel instance in Aberdeen some years back, and something on very much the same lines at Munich the year after the Franco-Prussian War. It is one of these cases--but, hullo, here is Lestrade! Good-afternoon, Lestrade! You will find an extra tumbler upon the sideboard, and there are cigars in the box."\
\
The official detective was attired in a pea-jacket and cravat, which gave him a decidedly nautical appearance, and he carried a black canvas bag in his hand. With a short greeting he seated himself and lit the cigar which had been offered to him.\
\
"What's up, then?" asked Holmes with a twinkle in his eye. "You look dissatisfied."\
\
"And I feel dissatisfied. It is this infernal St. Simon marriage case. I can make neither head nor tail of the business."\
\
"Really! You surprise me."\
\
"Who ever heard of such a mixed affair? Every clue seems to slip through my fingers. I have been at work upon it all day."\
\
"And very wet it seems to have made you," said Holmes laying his hand upon the arm of the pea-jacket.\
\
"Yes, I have been dragging the Serpentine."\
\
"In heaven's name, what for?"\
\
"In search of the body of Lady St. Simon."\
\
Sherlock Holmes leaned back in his chair and laughed heartily.\
\
"Have you dragged the basin of Trafalgar Square fountain?" he asked.\
\
"Why? What do you mean?"\
\
"Because you have just as good a chance of finding this lady in the one as in the other."\
\
Lestrade shot an angry glance at my companion. "I suppose you know all about it," he snarled.\
\
"Well, I have only just heard the facts, but my mind is made up."\
\
"Oh, indeed! Then you think that the Serpentine plays no part in the matter?"\
\
"I think it very unlikely."\
\
"Then perhaps you will kindly explain how it is that we found this in it?" He opened his bag as he spoke, and tumbled onto the floor a wedding-dress of watered silk, a pair of white satin shoes and a bride's wreath and veil, all discoloured and soaked in water. "There," said he, putting a new wedding-ring upon the top of the pile. "There is a little nut for you to crack, Master Holmes."\
\
"Oh, indeed!" said my friend, blowing blue rings into the air. "You dragged them from the Serpentine?"\
\
"No. They were found floating near the margin by a park-keeper. They have been identified as her clothes, and it seemed to me that if the clothes were there the body would not be far off."\
\
"By the same brilliant reasoning, every man's body is to be found in the neighbourhood of his wardrobe. And pray what did you hope to arrive at through this?"\
\
"At some evidence implicating Flora Millar in the disappearance."\
\
"I am afraid that you will find it difficult."\
\
"Are you, indeed, now?" cried Lestrade with some bitterness. "I am afraid, Holmes, that you are not very practical with your deductions and your inferences. You have made two blunders in as many minutes. This dress does implicate Miss Flora Millar."\
\
"And how?"\
\
"In the dress is a pocket. In the pocket is a card-case. In the card-case is a note. And here is the very note." He slapped it down upon the table in front of him. "Listen to this: 'You will see me when all is ready. Come at once. F. H. M.' Now my theory all along has been that Lady St. Simon was decoyed away by Flora Millar, and that she, with confederates, no doubt, was responsible for her disappearance. Here, signed with her initials, is the very note which was no doubt quietly slipped into her hand at the door and which lured her within their reach."\
\
"Very good, Lestrade," said Holmes, laughing. "You really are very fine indeed. Let me see it." He took up the paper in a listless way, but his attention instantly became riveted, and he gave a little cry of satisfaction. "This is indeed important," said he.\
\
"Ha! you find it so?"\
\
"Extremely so. I congratulate you warmly."\
\
Lestrade rose in his triumph and bent his head to look. "Why," he shrieked, "you're looking at the wrong side!"\
\
"On the contrary, this is the right side."\
\
"The right side? You're mad! Here is the note written in pencil over here."\
\
"And over here is what appears to be the fragment of a hotel bill, which interests me deeply."\
\
"There's nothing in it. I looked at it before," said Lestrade. " 'Oct. 4th, rooms 8s., breakfast 2s. 6d., cocktail 1s., lunch 2s. 6d., glass sherry, 8d.' I see nothing in that."\
\
"Very likely not. It is most important, all the same. As to the note, it is important also, or at least the initials are, so I congratulate you again."\
\
"I've wasted time enough," said Lestrade, rising. "I believe in hard work and not in sitting by the fire spinning fine theories. Good-day, Mr. Holmes, and we shall see which gets to the bottom of the matter first." He gathered up the garments, thrust them into the bag, and made for the door.\
\
"Just one hint to you, Lestrade," drawled Holmes before his rival vanished; "I will tell you the true solution of the matter. Lady St. Simon is a myth. There is not, and there never has been, any such person."\
\
Lestrade looked sadly at my companion. Then he turned to me, tapped his forehead three times, shook his head solemnly, and hurried away.\
\
He had hardly shut the door behind him when Holmes rose to put on his overcoat. "There is something in what the fellow says about outdoor work," he remarked, "so I think, Watson, that I must leave you to your papers for a little."\
\
It was after five o'clock when Sherlock Holmes left me, but I had no time to be lonely, for within an hour there arrived a confectioner's man with a very large flat box. This he unpacked with the help of a youth whom he had brought with him, and presently, to my very great astonishment, a quite epicurean little cold supper began to be laid out upon our humble lodging-house mahogany. There were a couple of brace of cold woodcock, a pheasant, a pate de foie gras pie with a group of ancient and cobwebby bottles. Having laid out all these luxuries, my two visitors vanished away, like the genii of the Arabian Nights, with no explanation save that the things had been paid for and were ordered to this address.\
\
Just before nine o'clock Sherlock Holmes stepped briskly into the room. His features were gravely set, but there was a light in his eye which made me think that he had not been disappointed in his conclusions.\
\
"They have laid the supper, then," he said, rubbing his hands.\
\
"You seem to expect company. They have laid for five."\
\
"Yes, I fancy we may have some company dropping in," said he. "I am surprised that Lord St. Simon has not already arrived. Ha! I fancy that I hear his step now upon the stairs."\
\
It was indeed our visitor of the afternoon who came bustling in, dangling his glasses more vigorously than ever, and with a very perturbed expression upon his aristocratic features.\
\
"My messenger reached you, then?" asked Holmes.\
\
"Yes, and I confess that the contents startled me beyond measure. Have you good authority for what you say?"\
\
"The best possible."\
\
Lord St. Simon sank into a chair and passed his hand over his forehead.\
\
"What will the Duke say," he murmured, "when he hears that one of the family has been subjected to such humiliation?"\
\
"It is the purest accident. I cannot allow that there is any humiliation."\
\
"Ah, you look on these things from another standpoint."\
\
"I fail to see that anyone is to blame. I can hardly see how the lady could have acted otherwise, though her abrupt method of doing it was undoubtedly to be regretted. Having no mother, she had no one to advise her at such a crisis."\
\
"It was a slight, sir, a public slight," said Lord St. Simon, tapping his fingers upon the table.\
\
"You must make allowance for this poor girl, placed in so unprecedented a position."\
\
"I will make no allowance. I am very angry indeed, and I have been shamefully used."\
\
"I think that I heard a ring," said Holmes. "Yes, there are steps on the landing. If I cannot persuade you to take a lenient view of the matter, Lord St. Simon, I have brought an advocate here who may be more successful." He opened the door and ushered in a lady and gentleman. "Lord St. Simon," said he "allow me to introduce you to Mr. and Mrs. Francis Hay Moulton. The lady, I think, you have already met."\
\
At the sight of these newcomers our client had sprung from his seat and stood very erect, with his eyes cast down and his hand thrust into the breast of his frock-coat, a picture of offended dignity. The lady had taken a quick step forward and had held out her hand to him, but he still refused to raise his eyes. It was as well for his resolution, perhaps, for her pleading face was one which it was hard to resist.\
\
"You're angry, Robert," said she. "Well, I guess you have every cause to be."\
\
"Pray make no apology to me," said Lord St. Simon bitterly.\
\
"Oh, yes, I know that I have treated you real bad and that I should have spoken to you before I went; but I was kind of rattled, and from the time when I saw Frank here again I just didn't know what I was doing or saying. I only wonder I didn't fall down and do a faint right there before the altar."\
\
"Perhaps, Mrs. Moulton, you would like my friend and me to leave the room while you explain this matter?"\
\
"If I may give an opinion," remarked the strange gentleman, "we've had just a little too much secrecy over this business already. For my part, I should like all Europe and America to hear the rights of it." He was a small, wiry, sunburnt man, clean-shaven, with a sharp face and alert manner.\
\
"Then I'll tell our story right away," said the lady. "Frank here and I met in '84, in McQuire's camp, near the Rockies, where Pa was working a claim. We were engaged to each other, Frank and I; but then one day father struck a rich pocket and made a pile, while poor Frank here had a claim that petered out and came to nothing. The richer Pa grew the poorer was Frank; so at last Pa wouldn't hear of our engagement lasting any longer, and he took me away to 'Frisco. Frank wouldn't throw up his hand, though; so he followed me there, and he saw me without Pa knowing anything about it. It would only have made him mad to know, so we just fixed it all up for ourselves. Frank said that he would go and make his pile, too, and never come back to claim me until he had as much as Pa. So then I promised to wait for him to the end of time and pledged myself not to marry anyone else while he lived. 'Why shouldn't we be married right away, then,' said he, 'and then I will feel sure of you; and I won't claim to be your husband until I come back?' Well, we talked it over, and he had fixed it all up so nicely, with a clergyman all ready in waiting, that we just did it right there; and then Frank went off to seek his fortune, and I went back to Pa.\
\
"The next I heard of Frank was that he was in Montana, and then he went prospecting in Arizona, and then I heard of him from New Mexico. After that came a long newspaper story about how a miners' camp had been attacked by Apache Indians, and there was my Frank's name among the killed. I fainted dead away, and I was very sick for months after. Pa thought I had a decline and took me to half the doctors in 'Frisco. Not a word of news came for a year and more, so that I never doubted that Frank was really dead. Then Lord St. Simon came to 'Frisco, and we came to London, and a marriage was arranged, and Pa was very pleased, but I felt all the time that no man on this earth would ever take the place in my heart that had been given to my poor Frank.\
\
"Still, if I had married Lord St. Simon, of course I'd have done my duty by him. We can't command our love, but we can our actions. I went to the altar with him with the intention to make him just as good a wife as it was in me to be. But you may imagine what I felt when, just as I came to the altar rails, I glanced back and saw Frank standing and looking at me out of the first pew. I thought it was his ghost at first; but when I looked again there he was still, with a kind of question in his eyes, as if to ask me whether I were glad or sorry to see him. I wonder I didn't drop. I know that everything was turning round, and the words of the clergyman were just like the buzz of a bee in my ear. I didn't know what to do. Should I stop the service and make a scene in the church? I glanced at him again, and he seemed to know what I was thinking, for he raised his finger to his lips to tell me to be still. Then I saw him scribble on a piece of paper, and I knew that he was writing me a note. As I passed his pew on the way out I dropped my bouquet over to him, and he slipped the note into my hand when he returned me the flowers. It was only a line asking me to join him when he made the sign to me to do so. Of course I never doubted for a moment that my first duty was now to him, and I determined to do just whatever he might direct.\
\
"When I got back I told my maid, who had known him in California, and had always been his friend. I ordered her to say nothing, but to get a few things packed and my ulster ready. I know I ought to have spoken to Lord St. Simon, but it was dreadful hard before his mother and all those great people. I just made up my mind to run away and explain afterwards. I hadn't been at the table ten minutes before I saw Frank out of the window at the other side of the road. He beckoned to me and then began walking into the Park. I slipped out, put on my things, and followed him. Some woman came talking something or other about Lord St. Simon to me--seemed to me from the little I heard as if he had a little secret of his own before marriage also--but I managed to get away from her and soon overtook Frank. We got into a cab together, and away we drove to some lodgings he had taken in Gordon Square, and that was my true wedding after all those years of waiting. Frank had been a prisoner among the Apaches, had escaped, came on to 'Frisco, found that I had given him up for dead and had gone to England, followed me there, and had come upon me at last on the very morning of my second wedding."\
\
"I saw it in a paper," explained the American. "It gave the name and the church but not where the lady lived."\
\
"Then we had a talk as to what we should do, and Frank was all for openness, but I was so ashamed of it all that I felt as if I should like to vanish away and never see any of them again--just sending a line to Pa, perhaps, to show him that I was alive. It was awful to me to think of all those lords and ladies sitting round that breakfast-table and waiting for me to come back. So Frank took my wedding-clothes and things and made a bundle of them, so that I should not be traced, and dropped them away somewhere where no one could find them. It is likely that we should have gone on to Paris to-morrow, only that this good gentleman, Mr. Holmes, came round to us this evening, though how he found us is more than I can think, and he showed us very clearly and kindly that I was wrong and that Frank was right, and that we should be putting ourselves in the wrong if we were so secret. Then he offered to give us a chance of talking to Lord St. Simon alone, and so we came right away round to his rooms at once. Now, Robert, you have heard it all, and I am very sorry if I have given you pain, and I hope that you do not think very meanly of me."\
\
Lord St. Simon had by no means relaxed his rigid attitude, but had listened with a frowning brow and a compressed lip to this long narrative.\
\
"Excuse me," he said, "but it is not my custom to discuss my most intimate personal affairs in this public manner."\
\
"Then you won't forgive me? You won't shake hands before I go?"\
\
"Oh, certainly, if it would give you any pleasure." He put out his hand and coldly grasped that which she extended to him.\
\
"I had hoped," suggested Holmes, "that you would have joined us in a friendly supper."\
\
"I think that there you ask a little too much," responded his Lordship. "I may be forced to acquiesce in these recent developments, but I can hardly be expected to make merry over them. I think that with your permission I will now wish you all a very good-night." He included us all in a sweeping bow and stalked out of the room.\
\
"Then I trust that you at least will honour me with your company," said Sherlock Holmes. "It is always a joy to meet an American, Mr. Moulton, for I am one of those who believe that the folly of a monarch and the blundering of a minister in far-gone years will not prevent our children from being some day citizens of the same world-wide country under a flag which shall be a quartering of the Union Jack with the Stars and Stripes."\
\
"The case has been an interesting one," remarked Holmes when our visitors had left us, "because it serves to show very clearly how simple the explanation may be of an affair which at first sight seems to be almost inexplicable. Nothing could be more natural than the sequence of events as narrated by this lady, and nothing stranger than the result when viewed, for instance, by Mr. Lestrade of Scotland Yard."\
\
"You were not yourself at fault at all, then?"\
\
"From the first, two facts were very obvious to me, the one that the lady had been quite willing to undergo the wedding ceremony, the other that she had repented of it within a few minutes of returning home. Obviously something had occurred during the morning, then, to cause her to change her mind. What could that something be? She could not have spoken to anyone when she was out, for she had been in the company of the bridegroom. Had she seen someone, then? If she had, it must be someone from America because she had spent so short a time in this country that she could hardly have allowed anyone to acquire so deep an influence over her that the mere sight of him would induce her to change her plans so completely. You see we have already arrived, by a process of exclusion, at the idea that she might have seen an American. Then who could this American be, and why should he possess so much influence over her? It might be a lover; it might be a husband. Her young womanhood had, I knew, been spent in rough scenes and under strange conditions. So far I had got before I ever heard Lord St. Simon's narrative. When he told us of a man in a pew, of the change in the bride's manner, of so transparent a device for obtaining a note as the dropping of a bouquet, of her resort to her confidential maid, and of her very significant allusion to claim-jumping--which in miners' parlance means taking possession of that which another person has a prior claim to--the whole situation became absolutely clear. She had gone off with a man, and the man was either a lover or was a previous husband--the chances being in favour of the latter."\
\
"And how in the world did you find them?"\
\
"It might have been difficult, but friend Lestrade held information in his hands the value of which he did not himself know. The initials were, of course, of the highest importance, but more valuable still was it to know that within a week he had settled his bill at one of the most select London hotels."\
\
"How did you deduce the select?"\
\
"By the select prices. Eight shillings for a bed and eightpence for a glass of sherry pointed to one of the most expensive hotels. There are not many in London which charge at that rate. In the second one which I visited in Northumberland Avenue, I learned by an inspection of the book that Francis H. Moulton, an American gentleman, had left only the day before, and on looking over the entries against him, I came upon the very items which I had seen in the duplicate bill. His letters were to be forwarded to 226 Gordon Square; so thither I travelled, and being fortunate enough to find the loving couple at home, I ventured to give them some paternal advice and to point out to them that it would be better in every way that they should make their position a little clearer both to the general public and to Lord St. Simon in particular. I invited them to meet him here, and, as you see, I made him keep the appointment."\
\
"But with no very good result," I remarked. "His conduct was certainly not very gracious."\
\
"Ah, Watson," said Holmes, smiling, "perhaps you would not be very gracious either, if, after all the trouble of wooing and wedding, you found yourself deprived in an instant of wife and of fortune. I think that we may judge Lord St. Simon very mercifully and thank our stars that we are never likely to find ourselves in the same position. Draw your chair up and hand me my violin, for the only problem we have still to solve is how to while away these bleak autumnal evenings."\
\
XI.  THE ADVENTURE OF THE BERYL CORONET\
\
\
"Holmes," said I as I stood one morning in our bow-window looking down the street, "here is a madman coming along. It seems rather sad that his relatives should allow him to come out alone."\
\
My friend rose lazily from his armchair and stood with his hands in the pockets of his dressing-gown, looking over my shoulder. It was a bright, crisp February morning, and the snow of the day before still lay deep upon the ground, shimmering brightly in the wintry sun. Down the centre of Baker Street it had been ploughed into a brown crumbly band by the traffic, but at either side and on the heaped-up edges of the foot-paths it still lay as white as when it fell. The grey pavement had been cleaned and scraped, but was still dangerously slippery, so that there were fewer passengers than usual. Indeed, from the direction of the Metropolitan Station no one was coming save the single gentleman whose eccentric conduct had drawn my attention.\
\
He was a man of about fifty, tall, portly, and imposing, with a massive, strongly marked face and a commanding figure. He was dressed in a sombre yet rich style, in black frock-coat, shining hat, neat brown gaiters, and well-cut pearl-grey trousers. Yet his actions were in absurd contrast to the dignity of his dress and features, for he was running hard, with occasional little springs, such as a weary man gives who is little accustomed to set any tax upon his legs. As he ran he jerked his hands up and down, waggled his head, and writhed his face into the most extraordinary contortions.\
\
"What on earth can be the matter with him?" I asked. "He is looking up at the numbers of the houses."\
\
"I believe that he is coming here," said Holmes, rubbing his hands.\
\
"Here?"\
\
"Yes; I rather think he is coming to consult me professionally. I think that I recognise the symptoms. Ha! did I not tell you?" As he spoke, the man, puffing and blowing, rushed at our door and pulled at our bell until the whole house resounded with the clanging.\
\
A few moments later he was in our room, still puffing, still gesticulating, but with so fixed a look of grief and despair in his eyes that our smiles were turned in an instant to horror and pity. For a while he could not get his words out, but swayed his body and plucked at his hair like one who has been driven to the extreme limits of his reason. Then, suddenly springing to his feet, he beat his head against the wall with such force that we both rushed upon him and tore him away to the centre of the room. Sherlock Holmes pushed him down into the easy-chair and, sitting beside him, patted his hand and chatted with him in the easy, soothing tones which he knew so well how to employ.\
\
"You have come to me to tell your story, have you not?" said he. "You are fatigued with your haste. Pray wait until you have recovered yourself, and then I shall be most happy to look into any little problem which you may submit to me."\
\
The man sat for a minute or more with a heaving chest, fighting against his emotion. Then he passed his handkerchief over his brow, set his lips tight, and turned his face towards us.\
\
"No doubt you think me mad?" said he.\
\
"I see that you have had some great trouble," responded Holmes.\
\
"God knows I have!--a trouble which is enough to unseat my reason, so sudden and so terrible is it. Public disgrace I might have faced, although I am a man whose character has never yet borne a stain. Private affliction also is the lot of every man; but the two coming together, and in so frightful a form, have been enough to shake my very soul. Besides, it is not I alone. The very noblest in the land may suffer unless some way be found out of this horrible affair."\
\
"Pray compose yourself, sir," said Holmes, "and let me have a clear account of who you are and what it is that has befallen you."\
\
"My name," answered our visitor, "is probably familiar to your ears. I am Alexander Holder, of the banking firm of Holder & Stevenson, of Threadneedle Street."\
\
The name was indeed well known to us as belonging to the senior partner in the second largest private banking concern in the City of London. What could have happened, then, to bring one of the foremost citizens of London to this most pitiable pass? We waited, all curiosity, until with another effort he braced himself to tell his story.\
\
"I feel that time is of value," said he; "that is why I hastened here when the police inspector suggested that I should secure your co-operation. I came to Baker Street by the Underground and hurried from there on foot, for the cabs go slowly through this snow. That is why I was so out of breath, for I am a man who takes very little exercise. I feel better now, and I will put the facts before you as shortly and yet as clearly as I can.\
\
"It is, of course, well known to you that in a successful banking business as much depends upon our being able to find remunerative investments for our funds as upon our increasing our connection and the number of our depositors. One of our most lucrative means of laying out money is in the shape of loans, where the security is unimpeachable. We have done a good deal in this direction during the last few years, and there are many noble families to whom we have advanced large sums upon the security of their pictures, libraries, or plate.\
\
"Yesterday morning I was seated in my office at the bank when a card was brought in to me by one of the clerks. I started when I saw the name, for it was that of none other than--well, perhaps even to you I had better say no more than that it was a name which is a household word all over the earth--one of the highest, noblest, most exalted names in England. I was overwhelmed by the honour and attempted, when he entered, to say so, but he plunged at once into business with the air of a man who wishes to hurry quickly through a disagreeable task.\
\
" 'Mr. Holder,' said he, 'I have been informed that you are in the habit of advancing money.'\
\
" 'The firm does so when the security is good.' I answered.\
\
" 'It is absolutely essential to me,' said he, 'that I should have $50,000 at once. I could, of course, borrow so trifling a sum ten times over from my friends, but I much prefer to make it a matter of business and to carry out that business myself. In my position you can readily understand that it is unwise to place one's self under obligations.'\
\
" 'For how long, may I ask, do you want this sum?' I asked.\
\
" 'Next Monday I have a large sum due to me, and I shall then most certainly repay what you advance, with whatever interest you think it right to charge. But it is very essential to me that the money should be paid at once.'\
\
" 'I should be happy to advance it without further parley from my own private purse,' said I, 'were it not that the strain would be rather more than it could bear. If, on the other hand, I am to do it in the name of the firm, then in justice to my partner I must insist that, even in your case, every businesslike precaution should be taken.'\
\
" 'I should much prefer to have it so,' said he, raising up a square, black morocco case which he had laid beside his chair. 'You have doubtless heard of the Beryl Coronet?'\
\
" 'One of the most precious public possessions of the empire,' said I.\
\
" 'Precisely.' He opened the case, and there, imbedded in soft, flesh-coloured velvet, lay the magnificent piece of jewellery which he had named. 'There are thirty-nine enormous beryls,' said he, 'and the price of the gold chasing is incalculable. The lowest estimate would put the worth of the coronet at double the sum which I have asked. I am prepared to leave it with you as my security.'\
\
"I took the precious case into my hands and looked in some perplexity from it to my illustrious client.\
\
" 'You doubt its value?' he asked.\
\
" 'Not at all. I only doubt--'\
\
" 'The propriety of my leaving it. You may set your mind at rest about that. I should not dream of doing so were it not absolutely certain that I should be able in four days to reclaim it. It is a pure matter of form. Is the security sufficient?'\
\
" 'Ample.'\
\
" 'You understand, Mr. Holder, that I am giving you a strong proof of the confidence which I have in you, founded upon all that I have heard of you. I rely upon you not only to be discreet and to refrain from all gossip upon the matter but, above all, to preserve this coronet with every possible precaution because I need not say that a great public scandal would be caused if any harm were to befall it. Any injury to it would be almost as serious as its complete loss, for there are no beryls in the world to match these, and it would be impossible to replace them. I leave it with you, however, with every confidence, and I shall call for it in person on Monday morning.'\
\
"Seeing that my client was anxious to leave, I said no more but, calling for my cashier, I ordered him to pay over fifty $1000 notes. When I was alone once more, however, with the precious case lying upon the table in front of me, I could not but think with some misgivings of the immense responsibility which it entailed upon me. There could be no doubt that, as it was a national possession, a horrible scandal would ensue if any misfortune should occur to it. I already regretted having ever consented to take charge of it. However, it was too late to alter the matter now, so I locked it up in my private safe and turned once more to my work.\
\
"When evening came I felt that it would be an imprudence to leave so precious a thing in the office behind me. Bankers' safes had been forced before now, and why should not mine be? If so, how terrible would be the position in which I should find myself! I determined, therefore, that for the next few days I would always carry the case backward and forward with me, so that it might never be really out of my reach. With this intention, I called a cab and drove out to my house at Streatham, carrying the jewel with me. I did not breathe freely until I had taken it upstairs and locked it in the bureau of my dressing-room.\
\
"And now a word as to my household, Mr. Holmes, for I wish you to thoroughly understand the situation. My groom and my page sleep out of the house, and may be set aside altogether. I have three maid-servants who have been with me a number of years and whose absolute reliability is quite above suspicion. Another, Lucy Parr, the second waiting-maid, has only been in my service a few months. She came with an excellent character, however, and has always given me satisfaction. She is a very pretty girl and has attracted admirers who have occasionally hung about the place. That is the only drawback which we have found to her, but we believe her to be a thoroughly good girl in every way.\
\
"So much for the servants. My family itself is so small that it will not take me long to describe it. I am a widower and have an only son, Arthur. He has been a disappointment to me, Mr. Holmes--a grievous disappointment. I have no doubt that I am myself to blame. People tell me that I have spoiled him. Very likely I have. When my dear wife died I felt that he was all I had to love. I could not bear to see the smile fade even for a moment from his face. I have never denied him a wish. Perhaps it would have been better for both of us had I been sterner, but I meant it for the best.\
\
"It was naturally my intention that he should succeed me in my business, but he was not of a business turn. He was wild, wayward, and, to speak the truth, I could not trust him in the handling of large sums of money. When he was young he became a member of an aristocratic club, and there, having charming manners, he was soon the intimate of a number of men with long purses and expensive habits. He learned to play heavily at cards and to squander money on the turf, until he had again and again to come to me and implore me to give him an advance upon his allowance, that he might settle his debts of honour. He tried more than once to break away from the dangerous company which he was keeping, but each time the influence of his friend, Sir George Burnwell, was enough to draw him back again.\
\
"And, indeed, I could not wonder that such a man as Sir George Burnwell should gain an influence over him, for he has frequently brought him to my house, and I have found myself that I could hardly resist the fascination of his manner. He is older than Arthur, a man of the world to his finger-tips, one who had been everywhere, seen everything, a brilliant talker, and a man of great personal beauty. Yet when I think of him in cold blood, far away from the glamour of his presence, I am convinced from his cynical speech and the look which I have caught in his eyes that he is one who should be deeply distrusted. So I think, and so, too, thinks my little Mary, who has a woman's quick insight into character.\
\
"And now there is only she to be described. She is my niece; but when my brother died five years ago and left her alone in the world I adopted her, and have looked upon her ever since as my daughter. She is a sunbeam in my house--sweet, loving, beautiful, a wonderful manager and housekeeper, yet as tender and quiet and gentle as a woman could be. She is my right hand. I do not know what I could do without her. In only one matter has she ever gone against my wishes. Twice my boy has asked her to marry him, for he loves her devotedly, but each time she has refused him. I think that if anyone could have drawn him into the right path it would have been she, and that his marriage might have changed his whole life; but now, alas! it is too late--forever too late!\
\
"Now, Mr. Holmes, you know the people who live under my roof, and I shall continue with my miserable story.\
\
"When we were taking coffee in the drawing-room that night after dinner, I told Arthur and Mary my experience, and of the precious treasure which we had under our roof, suppressing only the name of my client. Lucy Parr, who had brought in the coffee, had, I am sure, left the room; but I cannot swear that the door was closed. Mary and Arthur were much interested and wished to see the famous coronet, but I thought it better not to disturb it.\
\
" 'Where have you put it?' asked Arthur.\
\
" 'In my own bureau.'\
\
" 'Well, I hope to goodness the house won't be burgled during the night.' said he.\
\
" 'It is locked up,' I answered.\
\
" 'Oh, any old key will fit that bureau. When I was a youngster I have opened it myself with the key of the box-room cupboard.'\
\
"He often had a wild way of talking, so that I thought little of what he said. He followed me to my room, however, that night with a very grave face.\
\
" 'Look here, dad,' said he with his eyes cast down, 'can you let me have $200?'\
\
" 'No, I cannot!' I answered sharply. 'I have been far too generous with you in money matters.'\
\
" 'You have been very kind,' said he, 'but I must have this money, or else I can never show my face inside the club again.'\
\
" 'And a very good thing, too!' I cried.\
\
" 'Yes, but you would not have me leave it a dishonoured man,' said he. 'I could not bear the disgrace. I must raise the money in some way, and if you will not let me have it, then I must try other means.'\
\
"I was very angry, for this was the third demand during the month. 'You shall not have a farthing from me,' I cried, on which he bowed and left the room without another word.\
\
"When he was gone I unlocked my bureau, made sure that my treasure was safe, and locked it again. Then I started to go round the house to see that all was secure--a duty which I usually leave to Mary but which I thought it well to perform myself that night. As I came down the stairs I saw Mary herself at the side window of the hall, which she closed and fastened as I approached.\
\
" 'Tell me, dad,' said she, looking, I thought, a little disturbed, 'did you give Lucy, the maid, leave to go out to-night?'\
\
" 'Certainly not.'\
\
" 'She came in just now by the back door. I have no doubt that she has only been to the side gate to see someone, but I think that it is hardly safe and should be stopped.'\
\
" 'You must speak to her in the morning, or I will if you prefer it. Are you sure that everything is fastened?'\
\
" 'Quite sure, dad.'\
\
" 'Then, good-night.' I kissed her and went up to my bedroom again, where I was soon asleep.\
\
"I am endeavouring to tell you everything, Mr. Holmes, which may have any bearing upon the case, but I beg that you will question me upon any point which I do not make clear."\
\
"On the contrary, your statement is singularly lucid."\
\
"I come to a part of my story now in which I should wish to be particularly so. I am not a very heavy sleeper, and the anxiety in my mind tended, no doubt, to make me even less so than usual. About two in the morning, then, I was awakened by some sound in the house. It had ceased ere I was wide awake, but it had left an impression behind it as though a window had gently closed somewhere. I lay listening with all my ears. Suddenly, to my horror, there was a distinct sound of footsteps moving softly in the next room. I slipped out of bed, all palpitating with fear, and peeped round the corner of my dressing-room door.\
\
" 'Arthur!' I screamed, 'you villain! you thief! How dare you touch that coronet?'\
\
"The gas was half up, as I had left it, and my unhappy boy, dressed only in his shirt and trousers, was standing beside the light, holding the coronet in his hands. He appeared to be wrenching at it, or bending it with all his strength. At my cry he dropped it from his grasp and turned as pale as death. I snatched it up and examined it. One of the gold corners, with three of the beryls in it, was missing.\
\
" 'You blackguard!' I shouted, beside myself with rage. 'You have destroyed it! You have dishonoured me forever! Where are the jewels which you have stolen?'\
\
" 'Stolen!' he cried.\
\
" 'Yes, thief!' I roared, shaking him by the shoulder.\
\
" 'There are none missing. There cannot be any missing,' said he.\
\
" 'There are three missing. And you know where they are. Must I call you a liar as well as a thief? Did I not see you trying to tear off another piece?'\
\
" 'You have called me names enough,' said he, 'I will not stand it any longer. I shall not say another word about this business, since you have chosen to insult me. I will leave your house in the morning and make my own way in the world.'\
\
" 'You shall leave it in the hands of the police!' I cried half-mad with grief and rage. 'I shall have this matter probed to the bottom.'\
\
" 'You shall learn nothing from me,' said he with a passion such as I should not have thought was in his nature. 'If you choose to call the police, let the police find what they can.'\
\
"By this time the whole house was astir, for I had raised my voice in my anger. Mary was the first to rush into my room, and, at the sight of the coronet and of Arthur's face, she read the whole story and, with a scream, fell down senseless on the ground. I sent the house-maid for the police and put the investigation into their hands at once. When the inspector and a constable entered the house, Arthur, who had stood sullenly with his arms folded, asked me whether it was my intention to charge him with theft. I answered that it had ceased to be a private matter, but had become a public one, since the ruined coronet was national property. I was determined that the law should have its way in everything.\
\
" 'At least,' said he, 'you will not have me arrested at once. It would be to your advantage as well as mine if I might leave the house for five minutes.'\
\
" 'That you may get away, or perhaps that you may conceal what you have stolen,' said I. And then, realising the dreadful position in which I was placed, I implored him to remember that not only my honour but that of one who was far greater than I was at stake; and that he threatened to raise a scandal which would convulse the nation. He might avert it all if he would but tell me what he had done with the three missing stones.\
\
" 'You may as well face the matter,' said I; 'you have been caught in the act, and no confession could make your guilt more heinous. If you but make such reparation as is in your power, by telling us where the beryls are, all shall be forgiven and forgotten.'\
\
" 'Keep your forgiveness for those who ask for it,' he answered, turning away from me with a sneer. I saw that he was too hardened for any words of mine to influence him. There was but one way for it. I called in the inspector and gave him into custody. A search was made at once not only of his person but of his room and of every portion of the house where he could possibly have concealed the gems; but no trace of them could be found, nor would the wretched boy open his mouth for all our persuasions and our threats. This morning he was removed to a cell, and I, after going through all the police formalities, have hurried round to you to implore you to use your skill in unravelling the matter. The police have openly confessed that they can at present make nothing of it. You may go to any expense which you think necessary. I have already offered a reward of $1000. My God, what shall I do! I have lost my honour, my gems, and my son in one night. Oh, what shall I do!"\
\
He put a hand on either side of his head and rocked himself to and fro, droning to himself like a child whose grief has got beyond words.\
\
Sherlock Holmes sat silent for some few minutes, with his brows knitted and his eyes fixed upon the fire.\
\
"Do you receive much company?" he asked.\
\
"None save my partner with his family and an occasional friend of Arthur's. Sir George Burnwell has been several times lately. No one else, I think."\
\
"Do you go out much in society?"\
\
"Arthur does. Mary and I stay at home. We neither of us care for it."\
\
"That is unusual in a young girl."\
\
"She is of a quiet nature. Besides, she is not so very young. She is four-and-twenty."\
\
"This matter, from what you say, seems to have been a shock to her also."\
\
"Terrible! She is even more affected than I."\
\
"You have neither of you any doubt as to your son's guilt?"\
\
"How can we have when I saw him with my own eyes with the coronet in his hands."\
\
"I hardly consider that a conclusive proof. Was the remainder of the coronet at all injured?"\
\
"Yes, it was twisted."\
\
"Do you not think, then, that he might have been trying to straighten it?"\
\
"God bless you! You are doing what you can for him and for me. But it is too heavy a task. What was he doing there at all? If his purpose were innocent, why did he not say so?"\
\
"Precisely. And if it were guilty, why did he not invent a lie? His silence appears to me to cut both ways. There are several singular points about the case. What did the police think of the noise which awoke you from your sleep?"\
\
"They considered that it might be caused by Arthur's closing his bedroom door."\
\
"A likely story! As if a man bent on felony would slam his door so as to wake a household. What did they say, then, of the disappearance of these gems?"\
\
"They are still sounding the planking and probing the furniture in the hope of finding them."\
\
"Have they thought of looking outside the house?"\
\
"Yes, they have shown extraordinary energy. The whole garden has already been minutely examined."\
\
"Now, my dear sir," said Holmes. "is it not obvious to you now that this matter really strikes very much deeper than either you or the police were at first inclined to think? It appeared to you to be a simple case; to me it seems exceedingly complex. Consider what is involved by your theory. You suppose that your son came down from his bed, went, at great risk, to your dressing-room, opened your bureau, took out your coronet, broke off by main force a small portion of it, went off to some other place, concealed three gems out of the thirty-nine, with such skill that nobody can find them, and then returned with the other thirty-six into the room in which he exposed himself to the greatest danger of being discovered. I ask you now, is such a theory tenable?"\
\
"But what other is there?" cried the banker with a gesture of despair. "If his motives were innocent, why does he not explain them?"\
\
"It is our task to find that out," replied Holmes; "so now, if you please, Mr. Holder, we will set off for Streatham together, and devote an hour to glancing a little more closely into details."\
\
My friend insisted upon my accompanying them in their expedition, which I was eager enough to do, for my curiosity and sympathy were deeply stirred by the story to which we had listened. I confess that the guilt of the banker's son appeared to me to be as obvious as it did to his unhappy father, but still I had such faith in Holmes' judgment that I felt that there must be some grounds for hope as long as he was dissatisfied with the accepted explanation. He hardly spoke a word the whole way out to the southern suburb, but sat with his chin upon his breast and his hat drawn over his eyes, sunk in the deepest thought. Our client appeared to have taken fresh heart at the little glimpse of hope which had been presented to him, and he even broke into a desultory chat with me over his business affairs. A short railway journey and a shorter walk brought us to Fairbank, the modest residence of the great financier.\
\
Fairbank was a good-sized square house of white stone, standing back a little from the road. A double carriage-sweep, with a snow-clad lawn, stretched down in front to two large iron gates which closed the entrance. On the right side was a small wooden thicket, which led into a narrow path between two neat hedges stretching from the road to the kitchen door, and forming the tradesmen's entrance. On the left ran a lane which led to the stables, and was not itself within the grounds at all, being a public, though little used, thoroughfare. Holmes left us standing at the door and walked slowly all round the house, across the front, down the tradesmen's path, and so round by the garden behind into the stable lane. So long was he that Mr. Holder and I went into the dining-room and waited by the fire until he should return. We were sitting there in silence when the door opened and a young lady came in. She was rather above the middle height, slim, with dark hair and eyes, which seemed the darker against the absolute pallor of her skin. I do not think that I have ever seen such deadly paleness in a woman's face. Her lips, too, were bloodless, but her eyes were flushed with crying. As she swept silently into the room she impressed me with a greater sense of grief than the banker had done in the morning, and it was the more striking in her as she was evidently a woman of strong character, with immense capacity for self-restraint. Disregarding my presence, she went straight to her uncle and passed her hand over his head with a sweet womanly caress.\
\
"You have given orders that Arthur should be liberated, have you not, dad?" she asked.\
\
"No, no, my girl, the matter must be probed to the bottom."\
\
"But I am so sure that he is innocent. You know what woman's instincts are. I know that he has done no harm and that you will be sorry for having acted so harshly."\
\
"Why is he silent, then, if he is innocent?"\
\
"Who knows? Perhaps because he was so angry that you should suspect him."\
\
"How could I help suspecting him, when I actually saw him with the coronet in his hand?"\
\
"Oh, but he had only picked it up to look at it. Oh, do, do take my word for it that he is innocent. Let the matter drop and say no more. It is so dreadful to think of our dear Arthur in prison!"\
\
"I shall never let it drop until the gems are found--never, Mary! Your affection for Arthur blinds you as to the awful consequences to me. Far from hushing the thing up, I have brought a gentleman down from London to inquire more deeply into it."\
\
"This gentleman?" she asked, facing round to me.\
\
"No, his friend. He wished us to leave him alone. He is round in the stable lane now."\
\
"The stable lane?" She raised her dark eyebrows. "What can he hope to find there? Ah! this, I suppose, is he. I trust, sir, that you will succeed in proving, what I feel sure is the truth, that my cousin Arthur is innocent of this crime."\
\
"I fully share your opinion, and I trust, with you, that we may prove it," returned Holmes, going back to the mat to knock the snow from his shoes. "I believe I have the honour of addressing Miss Mary Holder. Might I ask you a question or two?"\
\
"Pray do, sir, if it may help to clear this horrible affair up."\
\
"You heard nothing yourself last night?"\
\
"Nothing, until my uncle here began to speak loudly. I heard that, and I came down."\
\
"You shut up the windows and doors the night before. Did you fasten all the windows?"\
\
"Yes."\
\
"Were they all fastened this morning?"\
\
"Yes."\
\
"You have a maid who has a sweetheart? I think that you remarked to your uncle last night that she had been out to see him?"\
\
"Yes, and she was the girl who waited in the drawing-room, and who may have heard uncle's remarks about the coronet."\
\
"I see. You infer that she may have gone out to tell her sweetheart, and that the two may have planned the robbery."\
\
"But what is the good of all these vague theories," cried the banker impatiently, "when I have told you that I saw Arthur with the coronet in his hands?"\
\
"Wait a little, Mr. Holder. We must come back to that. About this girl, Miss Holder. You saw her return by the kitchen door, I presume?"\
\
"Yes; when I went to see if the door was fastened for the night I met her slipping in. I saw the man, too, in the gloom."\
\
"Do you know him?"\
\
"Oh, yes! he is the green-grocer who brings our vegetables round. His name is Francis Prosper."\
\
"He stood," said Holmes, "to the left of the door--that is to say, farther up the path than is necessary to reach the door?"\
\
"Yes, he did."\
\
"And he is a man with a wooden leg?"\
\
Something like fear sprang up in the young lady's expressive black eyes. "Why, you are like a magician," said she. "How do you know that?" She smiled, but there was no answering smile in Holmes' thin, eager face.\
\
"I should be very glad now to go upstairs," said he. "I shall probably wish to go over the outside of the house again. Perhaps I had better take a look at the lower windows before I go up."\
\
He walked swiftly round from one to the other, pausing only at the large one which looked from the hall onto the stable lane. This he opened and made a very careful examination of the sill with his powerful magnifying lens. "Now we shall go upstairs," said he at last.\
\
The banker's dressing-room was a plainly furnished little chamber, with a grey carpet, a large bureau, and a long mirror. Holmes went to the bureau first and looked hard at the lock.\
\
"Which key was used to open it?" he asked.\
\
"That which my son himself indicated--that of the cupboard of the lumber-room."\
\
"Have you it here?"\
\
"That is it on the dressing-table."\
\
Sherlock Holmes took it up and opened the bureau.\
\
"It is a noiseless lock," said he. "It is no wonder that it did not wake you. This case, I presume, contains the coronet. We must have a look at it." He opened the case, and taking out the diadem he laid it upon the table. It was a magnificent specimen of the jeweller's art, and the thirty-six stones were the finest that I have ever seen. At one side of the coronet was a cracked edge, where a corner holding three gems had been torn away.\
\
"Now, Mr. Holder," said Holmes, "here is the corner which corresponds to that which has been so unfortunately lost. Might I beg that you will break it off."\
\
The banker recoiled in horror. "I should not dream of trying," said he.\
\
"Then I will." Holmes suddenly bent his strength upon it, but without result. "I feel it give a little," said he; "but, though I am exceptionally strong in the fingers, it would take me all my time to break it. An ordinary man could not do it. Now, what do you think would happen if I did break it, Mr. Holder? There would be a noise like a pistol shot. Do you tell me that all this happened within a few yards of your bed and that you heard nothing of it?"\
\
"I do not know what to think. It is all dark to me."\
\
"But perhaps it may grow lighter as we go. What do you think, Miss Holder?"\
\
"I confess that I still share my uncle's perplexity."\
\
"Your son had no shoes or slippers on when you saw him?"\
\
"He had nothing on save only his trousers and shirt."\
\
"Thank you. We have certainly been favoured with extraordinary luck during this inquiry, and it will be entirely our own fault if we do not succeed in clearing the matter up. With your permission, Mr. Holder, I shall now continue my investigations outside."\
\
He went alone, at his own request, for he explained that any unnecessary footmarks might make his task more difficult. For an hour or more he was at work, returning at last with his feet heavy with snow and his features as inscrutable as ever.\
\
"I think that I have seen now all that there is to see, Mr. Holder," said he; "I can serve you best by returning to my rooms."\
\
"But the gems, Mr. Holmes. Where are they?"\
\
"I cannot tell."\
\
The banker wrung his hands. "I shall never see them again!" he cried. "And my son? You give me hopes?"\
\
"My opinion is in no way altered."\
\
"Then, for God's sake, what was this dark business which was acted in my house last night?"\
\
"If you can call upon me at my Baker Street rooms to-morrow morning between nine and ten I shall be happy to do what I can to make it clearer. I understand that you give me carte blanche to act for you, provided only that I get back the gems, and that you place no limit on the sum I may draw."\
\
"I would give my fortune to have them back."\
\
"Very good. I shall look into the matter between this and then. Good-bye; it is just possible that I may have to come over here again before evening."\
\
It was obvious to me that my companion's mind was now made up about the case, although what his conclusions were was more than I could even dimly imagine. Several times during our homeward journey I endeavoured to sound him upon the point, but he always glided away to some other topic, until at last I gave it over in despair. It was not yet three when we found ourselves in our rooms once more. He hurried to his chamber and was down again in a few minutes dressed as a common loafer. With his collar turned up, his shiny, seedy coat, his red cravat, and his worn boots, he was a perfect sample of the class.\
\
"I think that this should do," said he, glancing into the glass above the fireplace. "I only wish that you could come with me, Watson, but I fear that it won't do. I may be on the trail in this matter, or I may be following a will-o'-the-wisp, but I shall soon know which it is. I hope that I may be back in a few hours." He cut a slice of beef from the joint upon the sideboard, sandwiched it between two rounds of bread, and thrusting this rude meal into his pocket he started off upon his expedition.\
\
I had just finished my tea when he returned, evidently in excellent spirits, swinging an old elastic-sided boot in his hand. He chucked it down into a corner and helped himself to a cup of tea.\
\
"I only looked in as I passed," said he. "I am going right on."\
\
"Where to?"\
\
"Oh, to the other side of the West End. It may be some time before I get back. Don't wait up for me in case I should be late."\
\
"How are you getting on?"\
\
"Oh, so so. Nothing to complain of. I have been out to Streatham since I saw you last, but I did not call at the house. It is a very sweet little problem, and I would not have missed it for a good deal. However, I must not sit gossiping here, but must get these disreputable clothes off and return to my highly respectable self."\
\
I could see by his manner that he had stronger reasons for satisfaction than his words alone would imply. His eyes twinkled, and there was even a touch of colour upon his sallow cheeks. He hastened upstairs, and a few minutes later I heard the slam of the hall door, which told me that he was off once more upon his congenial hunt.\
\
I waited until midnight, but there was no sign of his return, so I retired to my room. It was no uncommon thing for him to be away for days and nights on end when he was hot upon a scent, so that his lateness caused me no surprise. I do not know at what hour he came in, but when I came down to breakfast in the morning there he was with a cup of coffee in one hand and the paper in the other, as fresh and trim as possible.\
\
"You will excuse my beginning without you, Watson," said he, "but you remember that our client has rather an early appointment this morning."\
\
"Why, it is after nine now," I answered. "I should not be surprised if that were he. I thought I heard a ring."\
\
It was, indeed, our friend the financier. I was shocked by the change which had come over him, for his face which was naturally of a broad and massive mould, was now pinched and fallen in, while his hair seemed to me at least a shade whiter. He entered with a weariness and lethargy which was even more painful than his violence of the morning before, and he dropped heavily into the armchair which I pushed forward for him.\
\
"I do not know what I have done to be so severely tried," said he. "Only two days ago I was a happy and prosperous man, without a care in the world. Now I am left to a lonely and dishonoured age. One sorrow comes close upon the heels of another. My niece, Mary, has deserted me."\
\
"Deserted you?"\
\
"Yes. Her bed this morning had not been slept in, her room was empty, and a note for me lay upon the hall table. I had said to her last night, in sorrow and not in anger, that if she had married my boy all might have been well with him. Perhaps it was thoughtless of me to say so. It is to that remark that she refers in this note:\
\
" 'MY DEAREST UNCLE:--I feel that I have brought trouble upon you, and that if I had acted differently this terrible misfortune might never have occurred. I cannot, with this thought in my mind, ever again be happy under your roof, and I feel that I must leave you forever. Do not worry about my future, for that is provided for; and, above all, do not search for me, for it will be fruitless labour and an ill-service to me. In life or in death, I am ever your loving\
\
\
" 'MARY.'\
\
"What could she mean by that note, Mr. Holmes? Do you think it points to suicide?"\
\
"No, no, nothing of the kind. It is perhaps the best possible solution. I trust, Mr. Holder, that you are nearing the end of your troubles."\
\
"Ha! You say so! You have heard something, Mr. Holmes; you have learned something! Where are the gems?"\
\
"You would not think $1000 apiece an excessive sum for them?"\
\
"I would pay ten."\
\
"That would be unnecessary. Three thousand will cover the matter. And there is a little reward, I fancy. Have you your check-book? Here is a pen. Better make it out for $4000."\
\
With a dazed face the banker made out the required check. Holmes walked over to his desk, took out a little triangular piece of gold with three gems in it, and threw it down upon the table.\
\
With a shriek of joy our client clutched it up.\
\
"You have it!" he gasped. "I am saved! I am saved!"\
\
The reaction of joy was as passionate as his grief had been, and he hugged his recovered gems to his bosom.\
\
"There is one other thing you owe, Mr. Holder," said Sherlock Holmes rather sternly.\
\
"Owe!" He caught up a pen. "Name the sum, and I will pay it."\
\
"No, the debt is not to me. You owe a very humble apology to that noble lad, your son, who has carried himself in this matter as I should be proud to see my own son do, should I ever chance to have one."\
\
"Then it was not Arthur who took them?"\
\
"I told you yesterday, and I repeat to-day, that it was not."\
\
"You are sure of it! Then let us hurry to him at once to let him know that the truth is known."\
\
"He knows it already. When I had cleared it all up I had an interview with him, and finding that he would not tell me the story, I told it to him, on which he had to confess that I was right and to add the very few details which were not yet quite clear to me. Your news of this morning, however, may open his lips."\
\
"For heaven's sake, tell me, then, what is this extraordinary mystery!"\
\
"I will do so, and I will show you the steps by which I reached it. And let me say to you, first, that which it is hardest for me to say and for you to hear: there has been an understanding between Sir George Burnwell and your niece Mary. They have now fled together."\
\
"My Mary? Impossible!"\
\
"It is unfortunately more than possible; it is certain. Neither you nor your son knew the true character of this man when you admitted him into your family circle. He is one of the most dangerous men in England--a ruined gambler, an absolutely desperate villain, a man without heart or conscience. Your niece knew nothing of such men. When he breathed his vows to her, as he had done to a hundred before her, she flattered herself that she alone had touched his heart. The devil knows best what he said, but at least she became his tool and was in the habit of seeing him nearly every evening."\
\
"I cannot, and I will not, believe it!" cried the banker with an ashen face.\
\
"I will tell you, then, what occurred in your house last night. Your niece, when you had, as she thought, gone to your room, slipped down and talked to her lover through the window which leads into the stable lane. His footmarks had pressed right through the snow, so long had he stood there. She told him of the coronet. His wicked lust for gold kindled at the news, and he bent her to his will. I have no doubt that she loved you, but there are women in whom the love of a lover extinguishes all other loves, and I think that she must have been one. She had hardly listened to his instructions when she saw you coming downstairs, on which she closed the window rapidly and told you about one of the servants' escapade with her wooden-legged lover, which was all perfectly true.\
\
"Your boy, Arthur, went to bed after his interview with you but he slept badly on account of his uneasiness about his club debts. In the middle of the night he heard a soft tread pass his door, so he rose and, looking out, was surprised to see his cousin walking very stealthily along the passage until she disappeared into your dressing-room. Petrified with astonishment, the lad slipped on some clothes and waited there in the dark to see what would come of this strange affair. Presently she emerged from the room again, and in the light of the passage-lamp your son saw that she carried the precious coronet in her hands. She passed down the stairs, and he, thrilling with horror, ran along and slipped behind the curtain near your door, whence he could see what passed in the hall beneath. He saw her stealthily open the window, hand out the coronet to someone in the gloom, and then closing it once more hurry back to her room, passing quite close to where he stood hid behind the curtain.\
\
"As long as she was on the scene he could not take any action without a horrible exposure of the woman whom he loved. But the instant that she was gone he realised how crushing a misfortune this would be for you, and how all-important it was to set it right. He rushed down, just as he was, in his bare feet, opened the window, sprang out into the snow, and ran down the lane, where he could see a dark figure in the moonlight. Sir George Burnwell tried to get away, but Arthur caught him, and there was a struggle between them, your lad tugging at one side of the coronet, and his opponent at the other. In the scuffle, your son struck Sir George and cut him over the eye. Then something suddenly snapped, and your son, finding that he had the coronet in his hands, rushed back, closed the window, ascended to your room, and had just observed that the coronet had been twisted in the struggle and was endeavouring to straighten it when you appeared upon the scene."\
\
"Is it possible?" gasped the banker.\
\
"You then roused his anger by calling him names at a moment when he felt that he had deserved your warmest thanks. He could not explain the true state of affairs without betraying one who certainly deserved little enough consideration at his hands. He took the more chivalrous view, however, and preserved her secret."\
\
"And that was why she shrieked and fainted when she saw the coronet," cried Mr. Holder. "Oh, my God! what a blind fool I have been! And his asking to be allowed to go out for five minutes! The dear fellow wanted to see if the missing piece were at the scene of the struggle. How cruelly I have misjudged him!"\
\
"When I arrived at the house," continued Holmes, "I at once went very carefully round it to observe if there were any traces in the snow which might help me. I knew that none had fallen since the evening before, and also that there had been a strong frost to preserve impressions. I passed along the tradesmen's path, but found it all trampled down and indistinguishable. Just beyond it, however, at the far side of the kitchen door, a woman had stood and talked with a man, whose round impressions on one side showed that he had a wooden leg. I could even tell that they had been disturbed, for the woman had run back swiftly to the door, as was shown by the deep toe and light heel marks, while Wooden-leg had waited a little, and then had gone away. I thought at the time that this might be the maid and her sweetheart, of whom you had already spoken to me, and inquiry showed it was so. I passed round the garden without seeing anything more than random tracks, which I took to be the police; but when I got into the stable lane a very long and complex story was written in the snow in front of me.\
\
"There was a double line of tracks of a booted man, and a second double line which I saw with delight belonged to a man with naked feet. I was at once convinced from what you had told me that the latter was your son. The first had walked both ways, but the other had run swiftly, and as his tread was marked in places over the depression of the boot, it was obvious that he had passed after the other. I followed them up and found they led to the hall window, where Boots had worn all the snow away while waiting. Then I walked to the other end, which was a hundred yards or more down the lane. I saw where Boots had faced round, where the snow was cut up as though there had been a struggle, and, finally, where a few drops of blood had fallen, to show me that I was not mistaken. Boots had then run down the lane, and another little smudge of blood showed that it was he who had been hurt. When he came to the highroad at the other end, I found that the pavement had been cleared, so there was an end to that clue.\
\
"On entering the house, however, I examined, as you remember, the sill and framework of the hall window with my lens, and I could at once see that someone had passed out. I could distinguish the outline of an instep where the wet foot had been placed in coming in. I was then beginning to be able to form an opinion as to what had occurred. A man had waited outside the window; someone had brought the gems; the deed had been overseen by your son; he had pursued the thief; had struggled with him; they had each tugged at the coronet, their united strength causing injuries which neither alone could have effected. He had returned with the prize, but had left a fragment in the grasp of his opponent. So far I was clear. The question now was, who was the man and who was it brought him the coronet?\
\
"It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. Now, I knew that it was not you who had brought it down, so there only remained your niece and the maids. But if it were the maids, why should your son allow himself to be accused in their place? There could be no possible reason. As he loved his cousin, however, there was an excellent explanation why he should retain her secret--the more so as the secret was a disgraceful one. When I remembered that you had seen her at that window, and how she had fainted on seeing the coronet again, my conjecture became a certainty.\
\
"And who could it be who was her confederate? A lover evidently, for who else could outweigh the love and gratitude which she must feel to you? I knew that you went out little, and that your circle of friends was a very limited one. But among them was Sir George Burnwell. I had heard of him before as being a man of evil reputation among women. It must have been he who wore those boots and retained the missing gems. Even though he knew that Arthur had discovered him, he might still flatter himself that he was safe, for the lad could not say a word without compromising his own family.\
\
"Well, your own good sense will suggest what measures I took next. I went in the shape of a loafer to Sir George's house, managed to pick up an acquaintance with his valet, learned that his master had cut his head the night before, and, finally, at the expense of six shillings, made all sure by buying a pair of his cast-off shoes. With these I journeyed down to Streatham and saw that they exactly fitted the tracks."\
\
"I saw an ill-dressed vagabond in the lane yesterday evening," said Mr. Holder.\
\
"Precisely. It was I. I found that I had my man, so I came home and changed my clothes. It was a delicate part which I had to play then, for I saw that a prosecution must be avoided to avert scandal, and I knew that so astute a villain would see that our hands were tied in the matter. I went and saw him. At first, of course, he denied everything. But when I gave him every particular that had occurred, he tried to bluster and took down a life-preserver from the wall. I knew my man, however, and I clapped a pistol to his head before he could strike. Then he became a little more reasonable. I told him that we would give him a price for the stones he held--$1000 apiece. That brought out the first signs of grief that he had shown. 'Why, dash it all!' said he, 'I've let them go at six hundred for the three!' I soon managed to get the address of the receiver who had them, on promising him that there would be no prosecution. Off I set to him, and after much chaffering I got our stones at $1000 apiece. Then I looked in upon your son, told him that all was right, and eventually got to my bed about two o'clock, after what I may call a really hard day's work."\
\
"A day which has saved England from a great public scandal," said the banker, rising. "Sir, I cannot find words to thank you, but you shall not find me ungrateful for what you have done. Your skill has indeed exceeded all that I have heard of it. And now I must fly to my dear boy to apologise to him for the wrong which I have done him. As to what you tell me of poor Mary, it goes to my very heart. Not even your skill can inform me where she is now."\
\
"I think that we may safely say," returned Holmes, "that she is wherever Sir George Burnwell is. It is equally certain, too, that whatever her sins are, they will soon receive a more than sufficient punishment."\
\
XII.  THE ADVENTURE OF THE COPPER BEECHES\
\
\
"To the man who loves art for its own sake," remarked Sherlock Holmes, tossing aside the advertisement sheet of the Daily Telegraph, "it is frequently in its least important and lowliest manifestations that the keenest pleasure is to be derived. It is pleasant to me to observe, Watson, that you have so far grasped this truth that in these little records of our cases which you have been good enough to draw up, and, I am bound to say, occasionally to embellish, you have given prominence not so much to the many causes celebres and sensational trials in which I have figured but rather to those incidents which may have been trivial in themselves, but which have given room for those faculties of deduction and of logical synthesis which I have made my special province."\
\
"And yet," said I, smiling, "I cannot quite hold myself absolved from the charge of sensationalism which has been urged against my records."\
\
"You have erred, perhaps," he observed, taking up a glowing cinder with the tongs and lighting with it the long cherry-wood pipe which was wont to replace his clay when he was in a disputatious rather than a meditative mood--"you have erred perhaps in attempting to put colour and life into each of your statements instead of confining yourself to the task of placing upon record that severe reasoning from cause to effect which is really the only notable feature about the thing."\
\
"It seems to me that I have done you full justice in the matter," I remarked with some coldness, for I was repelled by the egotism which I had more than once observed to be a strong factor in my friend's singular character.\
\
"No, it is not selfishness or conceit," said he, answering, as was his wont, my thoughts rather than my words. "If I claim full justice for my art, it is because it is an impersonal thing--a thing beyond myself. Crime is common. Logic is rare. Therefore it is upon the logic rather than upon the crime that you should dwell. You have degraded what should have been a course of lectures into a series of tales."\
\
It was a cold morning of the early spring, and we sat after breakfast on either side of a cheery fire in the old room at Baker Street. A thick fog rolled down between the lines of dun-coloured houses, and the opposing windows loomed like dark, shapeless blurs through the heavy yellow wreaths. Our gas was lit and shone on the white cloth and glimmer of china and metal, for the table had not been cleared yet. Sherlock Holmes had been silent all the morning, dipping continuously into the advertisement columns of a succession of papers until at last, having apparently given up his search, he had emerged in no very sweet temper to lecture me upon my literary shortcomings.\
\
"At the same time," he remarked after a pause, during which he had sat puffing at his long pipe and gazing down into the fire, "you can hardly be open to a charge of sensationalism, for out of these cases which you have been so kind as to interest yourself in, a fair proportion do not treat of crime, in its legal sense, at all. The small matter in which I endeavoured to help the King of Bohemia, the singular experience of Miss Mary Sutherland, the problem connected with the man with the twisted lip, and the incident of the noble bachelor, were all matters which are outside the pale of the law. But in avoiding the sensational, I fear that you may have bordered on the trivial."\
\
"The end may have been so," I answered, "but the methods I hold to have been novel and of interest."\
\
"Pshaw, my dear fellow, what do the public, the great unobservant public, who could hardly tell a weaver by his tooth or a compositor by his left thumb, care about the finer shades of analysis and deduction! But, indeed, if you are trivial. I cannot blame you, for the days of the great cases are past. Man, or at least criminal man, has lost all enterprise and originality. As to my own little practice, it seems to be degenerating into an agency for recovering lost lead pencils and giving advice to young ladies from boarding-schools. I think that I have touched bottom at last, however. This note I had this morning marks my zero-point, I fancy. Read it!" He tossed a crumpled letter across to me.\
\
It was dated from Montague Place upon the preceding evening, and ran thus:\
\
"DEAR MR. HOLMES:--I am very anxious to consult you as to whether I should or should not accept a situation which has been offered to me as governess. I shall call at half-past ten to-morrow if I do not inconvenience you. Yours faithfully,\
\
\
"VIOLET HUNTER."\
\
"Do you know the young lady?" I asked.\
\
"Not I."\
\
"It is half-past ten now."\
\
"Yes, and I have no doubt that is her ring."\
\
"It may turn out to be of more interest than you think. You remember that the affair of the blue carbuncle, which appeared to be a mere whim at first, developed into a serious investigation. It may be so in this case, also."\
\
"Well, let us hope so. But our doubts will very soon be solved, for here, unless I am much mistaken, is the person in question."\
\
As he spoke the door opened and a young lady entered the room. She was plainly but neatly dressed, with a bright, quick face, freckled like a plover's egg, and with the brisk manner of a woman who has had her own way to make in the world.\
\
"You will excuse my troubling you, I am sure," said she, as my companion rose to greet her, "but I have had a very strange experience, and as I have no parents or relations of any sort from whom I could ask advice, I thought that perhaps you would be kind enough to tell me what I should do."\
\
"Pray take a seat, Miss Hunter. I shall be happy to do anything that I can to serve you."\
\
I could see that Holmes was favourably impressed by the manner and speech of his new client. He looked her over in his searching fashion, and then composed himself, with his lids drooping and his finger-tips together, to listen to her story.\
\
"I have been a governess for five years," said she, "in the family of Colonel Spence Munro, but two months ago the colonel received an appointment at Halifax, in Nova Scotia, and took his children over to America with him, so that I found myself without a situation. I advertised, and I answered advertisements, but without success. At last the little money which I had saved began to run short, and I was at my wit's end as to what I should do.\
\
"There is a well-known agency for governesses in the West End called Westaway's, and there I used to call about once a week in order to see whether anything had turned up which might suit me. Westaway was the name of the founder of the business, but it is really managed by Miss Stoper. She sits in her own little office, and the ladies who are seeking employment wait in an anteroom, and are then shown in one by one, when she consults her ledgers and sees whether she has anything which would suit them.\
\
"Well, when I called last week I was shown into the little office as usual, but I found that Miss Stoper was not alone. A prodigiously stout man with a very smiling face and a great heavy chin which rolled down in fold upon fold over his throat sat at her elbow with a pair of glasses on his nose, looking very earnestly at the ladies who entered. As I came in he gave quite a jump in his chair and turned quickly to Miss Stoper.\
\
" 'That will do,' said he; 'I could not ask for anything better. Capital! capital!' He seemed quite enthusiastic and rubbed his hands together in the most genial fashion. He was such a comfortable-looking man that it was quite a pleasure to look at him.\
\
" 'You are looking for a situation, miss?' he asked.\
\
" 'Yes, sir.'\
\
" 'As governess?'\
\
" 'Yes, sir.'\
\
" 'And what salary do you ask?'\
\
" 'I had $4 a month in my last place with Colonel Spence Munro.'\
\
" 'Oh, tut, tut! sweating--rank sweating!' he cried, throwing his fat hands out into the air like a man who is in a boiling passion. 'How could anyone offer so pitiful a sum to a lady with such attractions and accomplishments?'\
\
" 'My accomplishments, sir, may be less than you imagine,' said I. 'A little French, a little German, music, and drawing--'\
\
" 'Tut, tut!' he cried. 'This is all quite beside the question. The point is, have you or have you not the bearing and deportment of a lady? There it is in a nutshell. If you have not, you are not fitted for the rearing of a child who may some day play a considerable part in the history of the country. But if you have why, then, how could any gentleman ask you to condescend to accept anything under the three figures? Your salary with me, madam, would commence at $100 a year.'\
\
"You may imagine, Mr. Holmes, that to me, destitute as I was, such an offer seemed almost too good to be true. The gentleman, however, seeing perhaps the look of incredulity upon my face, opened a pocket-book and took out a note.\
\
" 'It is also my custom,' said he, smiling in the most pleasant fashion until his eyes were just two little shining slits amid the white creases of his face, 'to advance to my young ladies half their salary beforehand, so that they may meet any little expenses of their journey and their wardrobe.'\
\
"It seemed to me that I had never met so fascinating and so thoughtful a man. As I was already in debt to my tradesmen, the advance was a great convenience, and yet there was something unnatural about the whole transaction which made me wish to know a little more before I quite committed myself.\
\
" 'May I ask where you live, sir?' said I.\
\
" 'Hampshire. Charming rural place. The Copper Beeches, five miles on the far side of Winchester. It is the most lovely country, my dear young lady, and the dearest old country-house.'\
\
" 'And my duties, sir? I should be glad to know what they would be.'\
\
" 'One child--one dear little romper just six years old. Oh, if you could see him killing cockroaches with a slipper! Smack! smack! smack! Three gone before you could wink!' He leaned back in his chair and laughed his eyes into his head again.\
\
"I was a little startled at the nature of the child's amusement, but the father's laughter made me think that perhaps he was joking.\
\
" 'My sole duties, then,' I asked, 'are to take charge of a single child?'\
\
" 'No, no, not the sole, not the sole, my dear young lady,' he cried. 'Your duty would be, as I am sure your good sense would suggest, to obey any little commands my wife might give, provided always that they were such commands as a lady might with propriety obey. You see no difficulty, heh?'\
\
" 'I should be happy to make myself useful.'\
\
" 'Quite so. In dress now, for example. We are faddy people, you know--faddy but kind-hearted. If you were asked to wear any dress which we might give you, you would not object to our little whim. Heh?'\
\
" 'No,' said I, considerably astonished at his words.\
\
" 'Or to sit here, or sit there, that would not be offensive to you?'\
\
" 'Oh, no.'\
\
" 'Or to cut your hair quite short before you come to us?'\
\
"I could hardly believe my ears. As you may observe, Mr. Holmes, my hair is somewhat luxuriant, and of a rather peculiar tint of chestnut. It has been considered artistic. I could not dream of sacrificing it in this offhand fashion.\
\
" 'I am afraid that that is quite impossible,' said I. He had been watching me eagerly out of his small eyes, and I could see a shadow pass over his face as I spoke.\
\
" 'I am afraid that it is quite essential,' said he. 'It is a little fancy of my wife's, and ladies' fancies, you know, madam, ladies' fancies must be consulted. And so you won't cut your hair?'\
\
" 'No, sir, I really could not,' I answered firmly.\
\
" 'Ah, very well; then that quite settles the matter. It is a pity, because in other respects you would really have done very nicely. In that case, Miss Stoper, I had best inspect a few more of your young ladies.'\
\
"The manageress had sat all this while busy with her papers without a word to either of us, but she glanced at me now with so much annoyance upon her face that I could not help suspecting that she had lost a handsome commission through my refusal.\
\
" 'Do you desire your name to be kept upon the books?' she asked.\
\
" 'If you please, Miss Stoper.'\
\
" 'Well, really, it seems rather useless, since you refuse the most excellent offers in this fashion,' said she sharply. 'You can hardly expect us to exert ourselves to find another such opening for you. Good-day to you, Miss Hunter.' She struck a gong upon the table, and I was shown out by the page.\
\
"Well, Mr. Holmes, when I got back to my lodgings and found little enough in the cupboard, and two or three bills upon the table. I began to ask myself whether I had not done a very foolish thing. After all, if these people had strange fads and expected obedience on the most extraordinary matters, they were at least ready to pay for their eccentricity. Very few governesses in England are getting $100 a year. Besides, what use was my hair to me? Many people are improved by wearing it short and perhaps I should be among the number. Next day I was inclined to think that I had made a mistake, and by the day after I was sure of it. I had almost overcome my pride so far as to go back to the agency and inquire whether the place was still open when I received this letter from the gentleman himself. I have it here and I will read it to you:\
\
\
" 'The Copper Beeches, near Winchester.\
\
" 'DEAR MISS HUNTER:--Miss Stoper has very kindly given me your address, and I write from here to ask you whether you have reconsidered your decision. My wife is very anxious that you should come, for she has been much attracted by my description of you. We are willing to give $30 a quarter, or $120 a year, so as to recompense you for any little inconvenience which our fads may cause you. They are not very exacting, after all. My wife is fond of a particular shade of electric blue and would like you to wear such a dress indoors in the morning. You need not, however, go to the expense of purchasing one, as we have one belonging to my dear daughter Alice (now in Philadelphia), which would, I should think, fit you very well. Then, as to sitting here or there, or amusing yourself in any manner indicated, that need cause you no inconvenience. As regards your hair, it is no doubt a pity, especially as I could not help remarking its beauty during our short interview, but I am afraid that I must remain firm upon this point, and I only hope that the increased salary may recompense you for the loss. Your duties, as far as the child is concerned, are very light. Now do try to come, and I shall meet you with the dog-cart at Winchester. Let me know your train. Yours faithfully,\
\
\
" 'JEPHRO RUCASTLE.'\
\
"That is the letter which I have just received, Mr. Holmes, and my mind is made up that I will accept it. I thought, however, that before taking the final step I should like to submit the whole matter to your consideration."\
\
"Well, Miss Hunter, if your mind is made up, that settles the question," said Holmes, smiling.\
\
"But you would not advise me to refuse?"\
\
"I confess that it is not the situation which I should like to see a sister of mine apply for."\
\
"What is the meaning of it all, Mr. Holmes?"\
\
"Ah, I have no data. I cannot tell. Perhaps you have yourself formed some opinion?"\
\
"Well, there seems to me to be only one possible solution. Mr. Rucastle seemed to be a very kind, good-natured man. Is it not possible that his wife is a lunatic, that he desires to keep the matter quiet for fear she should be taken to an asylum, and that he humours her fancies in every way in order to prevent an outbreak?"\
\
"That is a possible solution--in fact, as matters stand, it is the most probable one. But in any case it does not seem to be a nice household for a young lady."\
\
"But the money, Mr. Holmes, the money!"\
\
"Well, yes, of course the pay is good--too good. That is what makes me uneasy. Why should they give you $120 a year, when they could have their pick for $40? There must be some strong reason behind."\
\
"I thought that if I told you the circumstances you would understand afterwards if I wanted your help. I should feel so much stronger if I felt that you were at the back of me."\
\
"Oh, you may carry that feeling away with you. I assure you that your little problem promises to be the most interesting which has come my way for some months. There is something distinctly novel about some of the features. If you should find yourself in doubt or in danger--"\
\
"Danger! What danger do you foresee?"\
\
Holmes shook his head gravely. "It would cease to be a danger if we could define it," said he. "But at any time, day or night, a telegram would bring me down to your help."\
\
"That is enough." She rose briskly from her chair with the anxiety all swept from her face. "I shall go down to Hampshire quite easy in my mind now. I shall write to Mr. Rucastle at once, sacrifice my poor hair to-night, and start for Winchester to-morrow." With a few grateful words to Holmes she bade us both good-night and bustled off upon her way.\
\
"At least," said I as we heard her quick, firm steps descending the stairs, "she seems to be a young lady who is very well able to take care of herself."\
\
"And she would need to be," said Holmes gravely. "I am much mistaken if we do not hear from her before many days are past."\
\
It was not very long before my friend's prediction was fulfilled. A fortnight went by, during which I frequently found my thoughts turning in her direction and wondering what strange side-alley of human experience this lonely woman had strayed into. The unusual salary, the curious conditions, the light duties, all pointed to something abnormal, though whether a fad or a plot, or whether the man were a philanthropist or a villain, it was quite beyond my powers to determine. As to Holmes, I observed that he sat frequently for half an hour on end, with knitted brows and an abstracted air, but he swept the matter away with a wave of his hand when I mentioned it. "Data! data! data!" he cried impatiently. "I can't make bricks without clay." And yet he would always wind up by muttering that no sister of his should ever have accepted such a situation.\
\
The telegram which we eventually received came late one night just as I was thinking of turning in and Holmes was settling down to one of those all-night chemical researches which he frequently indulged in, when I would leave him stooping over a retort and a test-tube at night and find him in the same position when I came down to breakfast in the morning. He opened the yellow envelope, and then, glancing at the message, threw it across to me.\
\
"Just look up the trains in Bradshaw," said he, and turned back to his chemical studies.\
\
The summons was a brief and urgent one.\
\
"Please be at the Black Swan Hotel at Winchester at midday to-morrow," it said. "Do come! I am at my wit's end.\
\
\
"HUNTER."\
\
"Will you come with me?" asked Holmes, glancing up.\
\
"I should wish to."\
\
"Just look it up, then."\
\
"There is a train at half-past nine," said I, glancing over my Bradshaw. "It is due at Winchester at 11:30."\
\
"That will do very nicely. Then perhaps I had better postpone my analysis of the acetones, as we may need to be at our best in the morning."\
\
By eleven o'clock the next day we were well upon our way to the old English capital. Holmes had been buried in the morning papers all the way down, but after we had passed the Hampshire border he threw them down and began to admire the scenery. It was an ideal spring day, a light blue sky, flecked with little fleecy white clouds drifting across from west to east. The sun was shining very brightly, and yet there was an exhilarating nip in the air, which set an edge to a man's energy. All over the countryside, away to the rolling hills around Aldershot, the little red and grey roofs of the farm-steadings peeped out from amid the light green of the new foliage.\
\
"Are they not fresh and beautiful?" I cried with all the enthusiasm of a man fresh from the fogs of Baker Street.\
\
But Holmes shook his head gravely.\
\
"Do you know, Watson," said he, "that it is one of the curses of a mind with a turn like mine that I must look at everything with reference to my own special subject. You look at these scattered houses, and you are impressed by their beauty. I look at them, and the only thought which comes to me is a feeling of their isolation and of the impunity with which crime may be committed there."\
\
"Good heavens!" I cried. "Who would associate crime with these dear old homesteads?"\
\
"They always fill me with a certain horror. It is my belief, Watson, founded upon my experience, that the lowest and vilest alleys in London do not present a more dreadful record of sin than does the smiling and beautiful countryside."\
\
"You horrify me!"\
\
"But the reason is very obvious. The pressure of public opinion can do in the town what the law cannot accomplish. There is no lane so vile that the scream of a tortured child, or the thud of a drunkard's blow, does not beget sympathy and indignation among the neighbours, and then the whole machinery of justice is ever so close that a word of complaint can set it going, and there is but a step between the crime and the dock. But look at these lonely houses, each in its own fields, filled for the most part with poor ignorant folk who know little of the law. Think of the deeds of hellish cruelty, the hidden wickedness which may go on, year in, year out, in such places, and none the wiser. Had this lady who appeals to us for help gone to live in Winchester, I should never have had a fear for her. It is the five miles of country which makes the danger. Still, it is clear that she is not personally threatened."\
\
"No. If she can come to Winchester to meet us she can get away."\
\
"Quite so. She has her freedom."\
\
"What can be the matter, then? Can you suggest no explanation?"\
\
"I have devised seven separate explanations, each of which would cover the facts as far as we know them. But which of these is correct can only be determined by the fresh information which we shall no doubt find waiting for us. Well, there is the tower of the cathedral, and we shall soon learn all that Miss Hunter has to tell."\
\
The Black Swan is an inn of repute in the High Street, at no distance from the station, and there we found the young lady waiting for us. She had engaged a sitting-room, and our lunch awaited us upon the table.\
\
"I am so delighted that you have come," she said earnestly. "It is so very kind of you both; but indeed I do not know what I should do. Your advice will be altogether invaluable to me."\
\
"Pray tell us what has happened to you."\
\
"I will do so, and I must be quick, for I have promised Mr. Rucastle to be back before three. I got his leave to come into town this morning, though he little knew for what purpose."\
\
"Let us have everything in its due order." Holmes thrust his long thin legs out towards the fire and composed himself to listen.\
\
"In the first place, I may say that I have met, on the whole, with no actual ill-treatment from Mr. and Mrs. Rucastle. It is only fair to them to say that. But I cannot understand them, and I am not easy in my mind about them."\
\
"What can you not understand?"\
\
"Their reasons for their conduct. But you shall have it all just as it occurred. When I came down, Mr. Rucastle met me here and drove me in his dog-cart to the Copper Beeches. It is, as he said, beautifully situated, but it is not beautiful in itself, for it is a large square block of a house, whitewashed, but all stained and streaked with damp and bad weather. There are grounds round it, woods on three sides, and on the fourth a field which slopes down to the Southampton highroad, which curves past about a hundred yards from the front door. This ground in front belongs to the house, but the woods all round are part of Lord Southerton's preserves. A clump of copper beeches immediately in front of the hall door has given its name to the place.\
\
"I was driven over by my employer, who was as amiable as ever, and was introduced by him that evening to his wife and the child. There was no truth, Mr. Holmes, in the conjecture which seemed to us to be probable in your rooms at Baker Street. Mrs. Rucastle is not mad. I found her to be a silent, pale-faced woman, much younger than her husband, not more than thirty, I should think, while he can hardly be less than forty-five. From their conversation I have gathered that they have been married about seven years, that he was a widower, and that his only child by the first wife was the daughter who has gone to Philadelphia. Mr. Rucastle told me in private that the reason why she had left them was that she had an unreasoning aversion to her stepmother. As the daughter could not have been less than twenty, I can quite imagine that her position must have been uncomfortable with her father's young wife.\
\
"Mrs. Rucastle seemed to me to be colourless in mind as well as in feature. She impressed me neither favourably nor the reverse. She was a nonentity. It was easy to see that she was passionately devoted both to her husband and to her little son. Her light grey eyes wandered continually from one to the other, noting every little want and forestalling it if possible. He was kind to her also in his bluff, boisterous fashion, and on the whole they seemed to be a happy couple. And yet she had some secret sorrow, this woman. She would often be lost in deep thought, with the saddest look upon her face. More than once I have surprised her in tears. I have thought sometimes that it was the disposition of her child which weighed upon her mind, for I have never met so utterly spoiled and so ill-natured a little creature. He is small for his age, with a head which is quite disproportionately large. His whole life appears to be spent in an alternation between savage fits of passion and gloomy intervals of sulking. Giving pain to any creature weaker than himself seems to be his one idea of amusement, and he shows quite remarkable talent in planning the capture of mice, little birds, and insects. But I would rather not talk about the creature, Mr. Holmes, and, indeed, he has little to do with my story."\
\
"I am glad of all details," remarked my friend, "whether they seem to you to be relevant or not."\
\
"I shall try not to miss anything of importance. The one unpleasant thing about the house, which struck me at once, was the appearance and conduct of the servants. There are only two, a man and his wife. Toller, for that is his name, is a rough, uncouth man, with grizzled hair and whiskers, and a perpetual smell of drink. Twice since I have been with them he has been quite drunk, and yet Mr. Rucastle seemed to take no notice of it. His wife is a very tall and strong woman with a sour face, as silent as Mrs. Rucastle and much less amiable. They are a most unpleasant couple, but fortunately I spend most of my time in the nursery and my own room, which are next to each other in one corner of the building.\
\
"For two days after my arrival at the Copper Beeches my life was very quiet; on the third, Mrs. Rucastle came down just after breakfast and whispered something to her husband.\
\
" 'Oh, yes,' said he, turning to me, 'we are very much obliged to you, Miss Hunter, for falling in with our whims so far as to cut your hair. I assure you that it has not detracted in the tiniest iota from your appearance. We shall now see how the electric-blue dress will become you. You will find it laid out upon the bed in your room, and if you would be so good as to put it on we should both be extremely obliged.'\
\
"The dress which I found waiting for me was of a peculiar shade of blue. It was of excellent material, a sort of beige, but it bore unmistakable signs of having been worn before. It could not have been a better fit if I had been measured for it. Both Mr. and Mrs. Rucastle expressed a delight at the look of it, which seemed quite exaggerated in its vehemence. They were waiting for me in the drawing-room, which is a very large room, stretching along the entire front of the house, with three long windows reaching down to the floor. A chair had been placed close to the central window, with its back turned towards it. In this I was asked to sit, and then Mr. Rucastle, walking up and down on the other side of the room, began to tell me a series of the funniest stories that I have ever listened to. You cannot imagine how comical he was, and I laughed until I was quite weary. Mrs. Rucastle, however, who has evidently no sense of humour, never so much as smiled, but sat with her hands in her lap, and a sad, anxious look upon her face. After an hour or so, Mr. Rucastle suddenly remarked that it was time to commence the duties of the day, and that I might change my dress and go to little Edward in the nursery.\
\
"Two days later this same performance was gone through under exactly similar circumstances. Again I changed my dress, again I sat in the window, and again I laughed very heartily at the funny stories of which my employer had an immense repertoire, and which he told inimitably. Then he handed me a yellow-backed novel, and moving my chair a little sideways, that my own shadow might not fall upon the page, he begged me to read aloud to him. I read for about ten minutes, beginning in the heart of a chapter, and then suddenly, in the middle of a sentence, he ordered me to cease and to change my dress.\
\
"You can easily imagine, Mr. Holmes, how curious I became as to what the meaning of this extraordinary performance could possibly be. They were always very careful, I observed, to turn my face away from the window, so that I became consumed with the desire to see what was going on behind my back. At first it seemed to be impossible, but I soon devised a means. My hand-mirror had been broken, so a happy thought seized me, and I concealed a piece of the glass in my handkerchief. On the next occasion, in the midst of my laughter, I put my handkerchief up to my eyes, and was able with a little management to see all that there was behind me. I confess that I was disappointed. There was nothing. At least that was my first impression. At the second glance, however, I perceived that there was a man standing in the Southampton Road, a small bearded man in a grey suit, who seemed to be looking in my direction. The road is an important highway, and there are usually people there. This man, however, was leaning against the railings which bordered our field and was looking earnestly up. I lowered my handkerchief and glanced at Mrs. Rucastle to find her eyes fixed upon me with a most searching gaze. She said nothing, but I am convinced that she had divined that I had a mirror in my hand and had seen what was behind me. She rose at once.\
\
" 'Jephro,' said she, 'there is an impertinent fellow upon the road there who stares up at Miss Hunter.'\
\
" 'No friend of yours, Miss Hunter?' he asked.\
\
" 'No, I know no one in these parts.'\
\
" 'Dear me! How very impertinent! Kindly turn round and motion to him to go away.'\
\
" 'Surely it would be better to take no notice.'\
\
" 'No, no, we should have him loitering here always. Kindly turn round and wave him away like that.'\
\
"I did as I was told, and at the same instant Mrs. Rucastle drew down the blind. That was a week ago, and from that time I have not sat again in the window, nor have I worn the blue dress, nor seen the man in the road."\
\
"Pray continue," said Holmes. "Your narrative promises to be a most interesting one."\
\
"You will find it rather disconnected, I fear, and there may prove to be little relation between the different incidents of which I speak. On the very first day that I was at the Copper Beeches, Mr. Rucastle took me to a small outhouse which stands near the kitchen door. As we approached it I heard the sharp rattling of a chain, and the sound as of a large animal moving about.\
\
" 'Look in here!' said Mr. Rucastle, showing me a slit between two planks. 'Is he not a beauty?'\
\
"I looked through and was conscious of two glowing eyes, and of a vague figure huddled up in the darkness.\
\
" 'Don't be frightened,' said my employer, laughing at the start which I had given. 'It's only Carlo, my mastiff. I call him mine, but really old Toller, my groom, is the only man who can do anything with him. We feed him once a day, and not too much then, so that he is always as keen as mustard. Toller lets him loose every night, and God help the trespasser whom he lays his fangs upon. For goodness' sake don't you ever on any pretext set your foot over the threshold at night, for it's as much as your life is worth.'\
\
"The warning was no idle one, for two nights later I happened to look out of my bedroom window about two o'clock in the morning. It was a beautiful moonlight night, and the lawn in front of the house was silvered over and almost as bright as day. I was standing, rapt in the peaceful beauty of the scene, when I was aware that something was moving under the shadow of the copper beeches. As it emerged into the moonshine I saw what it was. It was a giant dog, as large as a calf, tawny tinted, with hanging jowl, black muzzle, and huge projecting bones. It walked slowly across the lawn and vanished into the shadow upon the other side. That dreadful sentinel sent a chill to my heart which I do not think that any burglar could have done.\
\
"And now I have a very strange experience to tell you. I had, as you know, cut off my hair in London, and I had placed it in a great coil at the bottom of my trunk. One evening, after the child was in bed, I began to amuse myself by examining the furniture of my room and by rearranging my own little things. There was an old chest of drawers in the room, the two upper ones empty and open, the lower one locked. I had filled the first two with my linen, and as I had still much to pack away I was naturally annoyed at not having the use of the third drawer. It struck me that it might have been fastened by a mere oversight, so I took out my bunch of keys and tried to open it. The very first key fitted to perfection, and I drew the drawer open. There was only one thing in it, but I am sure that you would never guess what it was. It was my coil of hair.\
\
"I took it up and examined it. It was of the same peculiar tint, and the same thickness. But then the impossibility of the thing obtruded itself upon me. How could my hair have been locked in the drawer? With trembling hands I undid my trunk, turned out the contents, and drew from the bottom my own hair. I laid the two tresses together, and I assure you that they were identical. Was it not extraordinary? Puzzle as I would, I could make nothing at all of what it meant. I returned the strange hair to the drawer, and I said nothing of the matter to the Rucastles as I felt that I had put myself in the wrong by opening a drawer which they had locked.\
\
"I am naturally observant, as you may have remarked, Mr. Holmes, and I soon had a pretty good plan of the whole house in my head. There was one wing, however, which appeared not to be inhabited at all. A door which faced that which led into the quarters of the Tollers opened into this suite, but it was invariably locked. One day, however, as I ascended the stair, I met Mr. Rucastle coming out through this door, his keys in his hand, and a look on his face which made him a very different person to the round, jovial man to whom I was accustomed. His cheeks were red, his brow was all crinkled with anger, and the veins stood out at his temples with passion. He locked the door and hurried past me without a word or a look.\
\
"This aroused my curiosity, so when I went out for a walk in the grounds with my charge, I strolled round to the side from which I could see the windows of this part of the house. There were four of them in a row, three of which were simply dirty, while the fourth was shuttered up. They were evidently all deserted. As I strolled up and down, glancing at them occasionally, Mr. Rucastle came out to me, looking as merry and jovial as ever.\
\
" 'Ah!' said he, 'you must not think me rude if I passed you without a word, my dear young lady. I was preoccupied with business matters.'\
\
"I assured him that I was not offended. 'By the way,' said I, 'you seem to have quite a suite of spare rooms up there, and one of them has the shutters up.'\
\
"He looked surprised and, as it seemed to me, a little startled at my remark.\
\
" 'Photography is one of my hobbies,' said he. 'I have made my dark room up there. But, dear me! what an observant young lady we have come upon. Who would have believed it? Who would have ever believed it?' He spoke in a jesting tone, but there was no jest in his eyes as he looked at me. I read suspicion there and annoyance, but no jest.\
\
"Well, Mr. Holmes, from the moment that I understood that there was something about that suite of rooms which I was not to know, I was all on fire to go over them. It was not mere curiosity, though I have my share of that. It was more a feeling of duty--a feeling that some good might come from my penetrating to this place. They talk of woman's instinct; perhaps it was woman's instinct which gave me that feeling. At any rate, it was there, and I was keenly on the lookout for any chance to pass the forbidden door.\
\
"It was only yesterday that the chance came. I may tell you that, besides Mr. Rucastle, both Toller and his wife find something to do in these deserted rooms, and I once saw him carrying a large black linen bag with him through the door. Recently he has been drinking hard, and yesterday evening he was very drunk; and when I came upstairs there was the key in the door. I have no doubt at all that he had left it there. Mr. and Mrs. Rucastle were both downstairs, and the child was with them, so that I had an admirable opportunity. I turned the key gently in the lock, opened the door, and slipped through.\
\
"There was a little passage in front of me, unpapered and uncarpeted, which turned at a right angle at the farther end. Round this corner were three doors in a line, the first and third of which were open. They each led into an empty room, dusty and cheerless, with two windows in the one and one in the other, so thick with dirt that the evening light glimmered dimly through them. The centre door was closed, and across the outside of it had been fastened one of the broad bars of an iron bed, padlocked at one end to a ring in the wall, and fastened at the other with stout cord. The door itself was locked as well, and the key was not there. This barricaded door corresponded clearly with the shuttered window outside, and yet I could see by the glimmer from beneath it that the room was not in darkness. Evidently there was a skylight which let in light from above. As I stood in the passage gazing at the sinister door and wondering what secret it might veil, I suddenly heard the sound of steps within the room and saw a shadow pass backward and forward against the little slit of dim light which shone out from under the door. A mad, unreasoning terror rose up in me at the sight, Mr. Holmes. My overstrung nerves failed me suddenly, and I turned and ran--ran as though some dreadful hand were behind me clutching at the skirt of my dress. I rushed down the passage, through the door, and straight into the arms of Mr. Rucastle, who was waiting outside.\
\
" 'So,' said he, smiling, 'it was you, then. I thought that it must be when I saw the door open.'\
\
" 'Oh, I am so frightened!' I panted.\
\
" 'My dear young lady! my dear young lady!'--you cannot think how caressing and soothing his manner was--'and what has frightened you, my dear young lady?'\
\
"But his voice was just a little too coaxing. He overdid it. I was keenly on my guard against him.\
\
" 'I was foolish enough to go into the empty wing,' I answered. 'But it is so lonely and eerie in this dim light that I was frightened and ran out again. Oh, it is so dreadfully still in there!'\
\
" 'Only that?' said he, looking at me keenly.\
\
" 'Why, what did you think?' I asked.\
\
" 'Why do you think that I lock this door?'\
\
" 'I am sure that I do not know.'\
\
" 'It is to keep people out who have no business there. Do you see?' He was still smiling in the most amiable manner.\
\
" 'I am sure if I had known--'\
\
" 'Well, then, you know now. And if you ever put your foot over that threshold again'--here in an instant the smile hardened into a grin of rage, and he glared down at me with the face of a demon--'I'll throw you to the mastiff.'\
\
"I was so terrified that I do not know what I did. I suppose that I must have rushed past him into my room. I remember nothing until I found myself lying on my bed trembling all over. Then I thought of you, Mr. Holmes. I could not live there longer without some advice. I was frightened of the house, of the man, of the woman, of the servants, even of the child. They were all horrible to me. If I could only bring you down all would be well. Of course I might have fled from the house, but my curiosity was almost as strong as my fears. My mind was soon made up. I would send you a wire. I put on my hat and cloak, went down to the office, which is about half a mile from the house, and then returned, feeling very much easier. A horrible doubt came into my mind as I approached the door lest the dog might be loose, but I remembered that Toller had drunk himself into a state of insensibility that evening, and I knew that he was the only one in the household who had any influence with the savage creature, or who would venture to set him free. I slipped in in safety and lay awake half the night in my joy at the thought of seeing you. I had no difficulty in getting leave to come into Winchester this morning, but I must be back before three o'clock, for Mr. and Mrs. Rucastle are going on a visit, and will be away all the evening, so that I must look after the child. Now I have told you all my adventures, Mr. Holmes, and I should be very glad if you could tell me what it all means, and, above all, what I should do."\
\
Holmes and I had listened spellbound to this extraordinary story. My friend rose now and paced up and down the room, his hands in his pockets, and an expression of the most profound gravity upon his face.\
\
"Is Toller still drunk?" he asked.\
\
"Yes. I heard his wife tell Mrs. Rucastle that she could do nothing with him."\
\
"That is well. And the Rucastles go out to-night?"\
\
"Yes."\
\
"Is there a cellar with a good strong lock?"\
\
"Yes, the wine-cellar."\
\
"You seem to me to have acted all through this matter like a very brave and sensible girl, Miss Hunter. Do you think that you could perform one more feat? I should not ask it of you if I did not think you a quite exceptional woman."\
\
"I will try. What is it?"\
\
"We shall be at the Copper Beeches by seven o'clock, my friend and I. The Rucastles will be gone by that time, and Toller will, we hope, be incapable. There only remains Mrs. Toller, who might give the alarm. If you could send her into the cellar on some errand, and then turn the key upon her, you would facilitate matters immensely."\
\
"I will do it."\
\
"Excellent! We shall then look thoroughly into the affair. Of course there is only one feasible explanation. You have been brought there to personate someone, and the real person is imprisoned in this chamber. That is obvious. As to who this prisoner is, I have no doubt that it is the daughter, Miss Alice Rucastle, if I remember right, who was said to have gone to America. You were chosen, doubtless, as resembling her in height, figure, and the colour of your hair. Hers had been cut off, very possibly in some illness through which she has passed, and so, of course, yours had to be sacrificed also. By a curious chance you came upon her tresses. The man in the road was undoubtedly some friend of hers--possibly her fiance--and no doubt, as you wore the girl's dress and were so like her, he was convinced from your laughter, whenever he saw you, and afterwards from your gesture, that Miss Rucastle was perfectly happy, and that she no longer desired his attentions. The dog is let loose at night to prevent him from endeavouring to communicate with her. So much is fairly clear. The most serious point in the case is the disposition of the child."\
\
"What on earth has that to do with it?" I ejaculated.\
\
"My dear Watson, you as a medical man are continually gaining light as to the tendencies of a child by the study of the parents. Don't you see that the converse is equally valid. I have frequently gained my first real insight into the character of parents by studying their children. This child's disposition is abnormally cruel, merely for cruelty's sake, and whether he derives this from his smiling father, as I should suspect, or from his mother, it bodes evil for the poor girl who is in their power."\
\
"I am sure that you are right, Mr. Holmes," cried our client. "A thousand things come back to me which make me certain that you have hit it. Oh, let us lose not an instant in bringing help to this poor creature."\
\
"We must be circumspect, for we are dealing with a very cunning man. We can do nothing until seven o'clock. At that hour we shall be with you, and it will not be long before we solve the mystery."\
\
We were as good as our word, for it was just seven when we reached the Copper Beeches, having put up our trap at a wayside public-house. The group of trees, with their dark leaves shining like burnished metal in the light of the setting sun, were sufficient to mark the house even had Miss Hunter not been standing smiling on the door-step.\
\
"Have you managed it?" asked Holmes.\
\
A loud thudding noise came from somewhere downstairs. "That is Mrs. Toller in the cellar," said she. "Her husband lies snoring on the kitchen rug. Here are his keys, which are the duplicates of Mr. Rucastle's."\
\
"You have done well indeed!" cried Holmes with enthusiasm. "Now lead the way, and we shall soon see the end of this black business."\
\
We passed up the stair, unlocked the door, followed on down a passage, and found ourselves in front of the barricade which Miss Hunter had described. Holmes cut the cord and removed the transverse bar. Then he tried the various keys in the lock, but without success. No sound came from within, and at the silence Holmes' face clouded over.\
\
"I trust that we are not too late," said he. "I think, Miss Hunter, that we had better go in without you. Now, Watson, put your shoulder to it, and we shall see whether we cannot make our way in."\
\
It was an old rickety door and gave at once before our united strength. Together we rushed into the room. It was empty. There was no furniture save a little pallet bed, a small table, and a basketful of linen. The skylight above was open, and the prisoner gone.\
\
"There has been some villainy here," said Holmes; "this beauty has guessed Miss Hunter's intentions and has carried his victim off."\
\
"But how?"\
\
"Through the skylight. We shall soon see how he managed it." He swung himself up onto the roof. "Ah, yes," he cried, "here's the end of a long light ladder against the eaves. That is how he did it."\
\
"But it is impossible," said Miss Hunter; "the ladder was not there when the Rucastles went away."\
\
"He has come back and done it. I tell you that he is a clever and dangerous man. I should not be very much surprised if this were he whose step I hear now upon the stair. I think, Watson, that it would be as well for you to have your pistol ready."\
\
The words were hardly out of his mouth before a man appeared at the door of the room, a very fat and burly man, with a heavy stick in his hand. Miss Hunter screamed and shrunk against the wall at the sight of him, but Sherlock Holmes sprang forward and confronted him.\
\
"You villain!" said he, "where's your daughter?"\
\
The fat man cast his eyes round, and then up at the open skylight.\
\
"It is for me to ask you that," he shrieked, "you thieves! Spies and thieves! I have caught you, have I? You are in my power. I'll serve you!" He turned and clattered down the stairs as hard as he could go.\
\
"He's gone for the dog!" cried Miss Hunter.\
\
"I have my revolver," said I.\
\
"Better close the front door," cried Holmes, and we all rushed down the stairs together. We had hardly reached the hall when we heard the baying of a hound, and then a scream of agony, with a horrible worrying sound which it was dreadful to listen to. An elderly man with a red face and shaking limbs came staggering out at a side door.\
\
"My God!" he cried. "Someone has loosed the dog. It's not been fed for two days. Quick, quick, or it'll be too late!"\
\
Holmes and I rushed out and round the angle of the house, with Toller hurrying behind us. There was the huge famished brute, its black muzzle buried in Rucastle's throat, while he writhed and screamed upon the ground. Running up, I blew its brains out, and it fell over with its keen white teeth still meeting in the great creases of his neck. With much labour we separated them and carried him, living but horribly mangled, into the house. We laid him upon the drawing-room sofa, and having dispatched the sobered Toller to bear the news to his wife, I did what I could to relieve his pain. We were all assembled round him when the door opened, and a tall, gaunt woman entered the room.\
\
"Mrs. Toller!" cried Miss Hunter.\
\
"Yes, miss. Mr. Rucastle let me out when he came back before he went up to you. Ah, miss, it is a pity you didn't let me know what you were planning, for I would have told you that your pains were wasted."\
\
"Ha!" said Holmes, looking keenly at her. "It is clear that Mrs. Toller knows more about this matter than anyone else."\
\
"Yes, sir, I do, and I am ready enough to tell what I know."\
\
"Then, pray, sit down, and let us hear it for there are several points on which I must confess that I am still in the dark."\
\
"I will soon make it clear to you," said she; "and I'd have done so before now if I could ha' got out from the cellar. If there's police-court business over this, you'll remember that I was the one that stood your friend, and that I was Miss Alice's friend too.\
\
"She was never happy at home, Miss Alice wasn't, from the time that her father married again. She was slighted like and had no say in anything, but it never really became bad for her until after she met Mr. Fowler at a friend's house. As well as I could learn, Miss Alice had rights of her own by will, but she was so quiet and patient, she was, that she never said a word about them but just left everything in Mr. Rucastle's hands. He knew he was safe with her; but when there was a chance of a husband coming forward, who would ask for all that the law would give him, then her father thought it time to put a stop on it. He wanted her to sign a paper, so that whether she married or not, he could use her money. When she wouldn't do it, he kept on worrying her until she got brain-fever, and for six weeks was at death's door. Then she got better at last, all worn to a shadow, and with her beautiful hair cut off; but that didn't make no change in her young man, and he stuck to her as true as man could be."\
\
"Ah," said Holmes, "I think that what you have been good enough to tell us makes the matter fairly clear, and that I can deduce all that remains. Mr. Rucastle then, I presume, took to this system of imprisonment?"\
\
"Yes, sir."\
\
"And brought Miss Hunter down from London in order to get rid of the disagreeable persistence of Mr. Fowler."\
\
"That was it, sir."\
\
"But Mr. Fowler being a persevering man, as a good seaman should be, blockaded the house, and having met you succeeded by certain arguments, metallic or otherwise, in convincing you that your interests were the same as his."\
\
"Mr. Fowler was a very kind-spoken, free-handed gentleman," said Mrs. Toller serenely.\
\
"And in this way he managed that your good man should have no want of drink, and that a ladder should be ready at the moment when your master had gone out."\
\
"You have it, sir, just as it happened."\
\
"I am sure we owe you an apology, Mrs. Toller," said Holmes, "for you have certainly cleared up everything which puzzled us. And here comes the country surgeon and Mrs. Rucastle, so I think, Watson, that we had best escort Miss Hunter back to Winchester, as it seems to me that our locus standi now is rather a questionable one."\
\
And thus was solved the mystery of the sinister house with the copper beeches in front of the door. Mr. Rucastle survived, but was always a broken man, kept alive solely through the care of his devoted wife. They still live with their old servants, who probably know so much of Rucastle's past life that he finds it difficult to part from them. Mr. Fowler and Miss Rucastle were married, by special license, in Southampton the day after their flight, and he is now the holder of a government appointment in the island of Mauritius. As to Miss Violet Hunter, my friend Holmes, rather to my disappointment, manifested no further interest in her when once she had ceased to be the centre of one of his problems, and she is now the head of a private school at Walsall, where I believe that she has met with considerable success.\
\
*** END OF THE PROJECT GUTENBERG EBOOK, THE ADVENTURES OF SHERLOCK HOLMES ***\
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by Charles A. Beard and Mary R. Beard\
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Title: History of the United States\
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Author: Charles A. Beard and Mary R. Beard\
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Release Date: October 28, 2005 [EBook #16960]\
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Language: English\
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Character set encoding: ISO-8859-1\
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*** START OF THIS PROJECT GUTENBERG EBOOK HISTORY OF THE UNITED STATES ***\
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Produced by Curtis Weyant, M and the Online Distributed\
Proofreading Team at http://www.pgdp.net\
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\
\
\
\
\
\
HISTORY\
\
OF THE\
\
UNITED STATES\
\
\
BY\
\
\
CHARLES A. BEARD\
\
AND\
\
MARY R. BEARD\
\
\
\
New York\
\
THE MACMILLAN COMPANY\
\
1921\
\
_All rights reserved_\
\
COPYRIGHT, 1921,\
\
BY THE MACMILLAN COMPANY.\
\
\
Set up and electrotyped. Published March, 1921.\
\
\
\
\
Norwood Press\
\
J.S. Cushing Co.--Berwick & Smith Co.\
\
NORWOOD, MASS., U.S.A.\
\
\
\
\
PREFACE\
\
\
As things now stand, the course of instruction in American history in\
our public schools embraces three distinct treatments of the subject.\
Three separate books are used. First, there is the primary book, which\
is usually a very condensed narrative with emphasis on biographies and\
anecdotes. Second, there is the advanced text for the seventh or eighth\
grade, generally speaking, an expansion of the elementary book by the\
addition of forty or fifty thousand words. Finally, there is the high\
school manual. This, too, ordinarily follows the beaten path, giving\
fuller accounts of the same events and characters. To put it bluntly, we\
do not assume that our children obtain permanent possessions from their\
study of history in the lower grades. If mathematicians followed the\
same method, high school texts on algebra and geometry would include the\
multiplication table and fractions.\
\
There is, of course, a ready answer to the criticism advanced above. It\
is that teachers have learned from bitter experience how little history\
their pupils retain as they pass along the regular route. No teacher of\
history will deny this. Still it is a standing challenge to existing\
methods of historical instruction. If the study of history cannot be\
made truly progressive like the study of mathematics, science, and\
languages, then the historians assume a grave responsibility in adding\
their subject to the already overloaded curriculum. If the successive\
historical texts are only enlarged editions of the first text--more\
facts, more dates, more words--then history deserves most of the sharp\
criticism which it is receiving from teachers of science, civics, and\
economics.\
\
In this condition of affairs we find our justification for offering a\
new high school text in American history. Our first contribution is one\
of omission. The time-honored stories of exploration and the\
biographies of heroes are left out. We frankly hold that, if pupils know\
little or nothing about Columbus, Cortes, Magellan, or Captain John\
Smith by the time they reach the high school, it is useless to tell the\
same stories for perhaps the fourth time. It is worse than useless. It\
is an offense against the teachers of those subjects that are\
demonstrated to be progressive in character.\
\
In the next place we have omitted all descriptions of battles. Our\
reasons for this are simple. The strategy of a campaign or of a single\
battle is a highly technical, and usually a highly controversial, matter\
about which experts differ widely. In the field of military and naval\
operations most writers and teachers of history are mere novices. To\
dispose of Gettysburg or the Wilderness in ten lines or ten pages is\
equally absurd to the serious student of military affairs. Any one who\
compares the ordinary textbook account of a single Civil War campaign\
with the account given by Ropes, for instance, will ask for no further\
comment. No youth called upon to serve our country in arms would think\
of turning to a high school manual for information about the art of\
warfare. The dramatic scene or episode, so useful in arousing the\
interest of the immature pupil, seems out of place in a book that\
deliberately appeals to boys and girls on the very threshold of life's\
serious responsibilities.\
\
It is not upon negative features, however, that we rest our case. It is\
rather upon constructive features.\
\
_First._ We have written a topical, not a narrative, history. We have\
tried to set forth the important aspects, problems, and movements of\
each period, bringing in the narrative rather by way of illustration.\
\
_Second._ We have emphasized those historical topics which help to\
explain how our nation has come to be what it is to-day.\
\
_Third._ We have dwelt fully upon the social and economic aspects of our\
history, especially in relation to the politics of each period.\
\
_Fourth._ We have treated the causes and results of wars, the problems\
of financing and sustaining armed forces, rather than military strategy.\
These are the subjects which belong to a history for civilians. These\
are matters which civilians can understand--matters which they must\
understand, if they are to play well their part in war and peace.\
\
_Fifth._ By omitting the period of exploration, we have been able to\
enlarge the treatment of our own time. We have given special attention\
to the history of those current questions which must form the subject\
matter of sound instruction in citizenship.\
\
_Sixth._ We have borne in mind that America, with all her unique\
characteristics, is a part of a general civilization. Accordingly we\
have given diplomacy, foreign affairs, world relations, and the\
reciprocal influences of nations their appropriate place.\
\
_Seventh._ We have deliberately aimed at standards of maturity. The\
study of a mere narrative calls mainly for the use of the memory. We\
have aimed to stimulate habits of analysis, comparison, association,\
reflection, and generalization--habits calculated to enlarge as well as\
inform the mind. We have been at great pains to make our text clear,\
simple, and direct; but we have earnestly sought to stretch the\
intellects of our readers--to put them upon their mettle. Most of them\
will receive the last of their formal instruction in the high school.\
The world will soon expect maturity from them. Their achievements will\
depend upon the possession of other powers than memory alone. The\
effectiveness of their citizenship in our republic will be measured by\
the excellence of their judgment as well as the fullness of their\
information.\
\
     C.A.B.\
     M.R.B.\
\
     NEW YORK CITY,\
     February 8, 1921.\
\
\
\
\
=A SMALL LIBRARY IN AMERICAN HISTORY=\
\
\
_=SINGLE VOLUMES:=_\
\
BASSETT, J.S. _A Short History of the United States_\
ELSON, H.W. _History of the United States of America_\
\
\
_=SERIES:=_\
\
"EPOCHS OF AMERICAN HISTORY," EDITED BY A.B. HART\
\
HART, A.B. _Formation of the Union_\
THWAITES, R.G. _The Colonies_\
WILSON, WOODROW. _Division and Reunion_\
\
"RIVERSIDE SERIES," EDITED BY W.E. DODD\
\
BECKER, C.L. _Beginnings of the American People_\
DODD, W.E. _Expansion and Conflict_\
JOHNSON, A. _Union and Democracy_\
PAXSON, F.L. _The New Nation_\
\
\
\
\
CONTENTS\
\
\
PART I. THE COLONIAL PERIOD\
\
CHAPTER                                                           PAGE\
    I.  THE GREAT MIGRATION TO AMERICA                               1\
          The Agencies of American Colonization                      2\
          The Colonial Peoples                                       6\
          The Process of Colonization                               12\
\
   II.  COLONIAL AGRICULTURE, INDUSTRY, AND COMMERCE                20\
          The Land and the Westward Movement                        20\
          Industrial and Commercial Development                     28\
\
  III.  SOCIAL AND POLITICAL PROGRESS                               38\
          The Leadership of the Churches                            39\
          Schools and Colleges                                      43\
          The Colonial Press                                        46\
          The Evolution in Political Institutions                   48\
\
   IV.  THE DEVELOPMENT OF COLONIAL NATIONALISM                     56\
          Relations with the Indians and the French                 57\
          The Effects of Warfare on the Colonies                    61\
          Colonial Relations with the British Government            64\
          Summary of Colonial Period                                73\
\
\
PART II. CONFLICT AND INDEPENDENCE\
\
    V.  THE NEW COURSE IN BRITISH IMPERIAL POLICY                   77\
          George III and His System                                 77\
          George III's Ministers and Their Colonial Policies        79\
          Colonial Resistance Forces Repeal                         83\
          Resumption of British Revenue and Commercial Policies     87\
          Renewed Resistance in America                             90\
          Retaliation by the British Government                     93\
          From Reform to Revolution in America                      95\
\
   VI.  THE AMERICAN REVOLUTION                                     99\
          Resistance and Retaliation                                99\
          American Independence                                    101\
          The Establishment of Government and the New Allegiance   108\
          Military Affairs                                         116\
          The Finances of the Revolution                           125\
          The Diplomacy of the Revolution                          127\
          Peace at Last                                            132\
          Summary of the Revolutionary Period                      135\
\
\
PART III. FOUNDATIONS OF THE UNION AND NATIONAL POLITICS\
\
  VII.  THE FORMATION OF THE CONSTITUTION                          139\
          The Promise and the Difficulties of America              139\
          The Calling of a Constitutional Convention               143\
          The Framing of the Constitution                          146\
          The Struggle over Ratification                           157\
\
 VIII.  THE CLASH OF POLITICAL PARTIES                             162\
          The Men and Measures of the New Government               162\
          The Rise of Political Parties                            168\
          Foreign Influences and Domestic Politics                 171\
\
   IX.  THE JEFFERSONIAN REPUBLICANS IN POWER                      186\
          Republican Principles and Policies                       186\
          The Republicans and the Great West                       188\
          The Republican War for Commercial Independence           193\
          The Republicans Nationalized                             201\
          The National Decisions of Chief Justice Marshall         208\
          Summary of Union and National Politics                   212\
\
\
PART IV. THE WEST AND JACKSONIAN DEMOCRACY\
\
    X.  THE FARMERS BEYOND THE APPALACHIANS                        217\
          Preparation for Western Settlement                       217\
          The Western Migration and New States                     221\
          The Spirit of the Frontier                               228\
          The West and the East Meet                               230\
\
   XI.  JACKSONIAN DEMOCRACY                                       238\
          The Democratic Movement in the East                      238\
          The New Democracy Enters the Arena                       244\
          The New Democracy at Washington                          250\
          The Rise of the Whigs                                    260\
          The Interaction of American and European Opinion         265\
\
  XII.  THE MIDDLE BORDER AND THE GREAT WEST                       271\
          The Advance of the Middle Border                         271\
          On to the Pacific--Texas and the Mexican War             276\
          The Pacific Coast and Utah                               284\
          Summary of Western Development and National Politics     292\
\
\
PART V. SECTIONAL CONFLICT AND RECONSTRUCTION\
\
 XIII.  THE RISE OF THE INDUSTRIAL SYSTEM                          295\
          The Industrial Revolution                                296\
          The Industrial Revolution and National Politics          307\
\
  XIV.  THE PLANTING SYSTEM AND NATIONAL POLITICS                  316\
          Slavery--North and South                                 316\
          Slavery in National Politics                             324\
          The Drift of Events toward the Irrepressible Conflict    332\
\
   XV.  THE CIVIL WAR AND RECONSTRUCTION                           344\
          The Southern Confederacy                                 344\
          The War Measures of the Federal Government               350\
          The Results of the Civil War                             365\
          Reconstruction in the South                              370\
          Summary of the Sectional Conflict                        375\
\
\
PART VI. NATIONAL GROWTH AND WORLD POLITICS\
\
  XVI.  THE POLITICAL AND ECONOMIC EVOLUTION OF THE SOUTH          379\
          The South at the Close of the War                        379\
          The Restoration of White Supremacy                       382\
          The Economic Advance of the South                        389\
\
 XVII.  BUSINESS ENTERPRISE AND THE REPUBLICAN PARTY               401\
          Railways and Industry                                    401\
          The Supremacy of the Republican Party (1861-1885)        412\
          The Growth of Opposition to Republican Rule              417\
\
XVIII.  THE DEVELOPMENT OF THE GREAT WEST                          425\
          The Railways as Trail Blazers                            425\
          The Evolution of Grazing and Agriculture                 431\
          Mining and Manufacturing in the West                     436\
          The Admission of New States                              440\
          The Influence of the Far West on National Life           443\
\
  XIX.  DOMESTIC ISSUES BEFORE THE COUNTRY (1865-1897)             451\
          The Currency Question                                    452\
          The Protective Tariff and Taxation                       459\
          The Railways and Trusts                                  460\
          The Minor Parties and Unrest                             462\
          The Sound Money Battle of 1896                           466\
          Republican Measures and Results                          472\
\
   XX.  AMERICA A WORLD POWER (1865-1900)                          477\
          American Foreign Relations (1865-1898)                   478\
          Cuba and the Spanish War                                 485\
          American Policies in the Philippines and the Orient      497\
          Summary of National Growth and World Politics            504\
\
\
PART VII. PROGRESSIVE DEMOCRACY AND THE WORLD WAR\
\
  XXI.  THE EVOLUTION OF REPUBLICAN POLICIES (1901-1913)           507\
          Foreign Affairs                                          508\
          Colonial Administration                                  515\
          The Roosevelt Domestic Policies                          519\
          Legislative and Executive Activities                     523\
          The Administration of President Taft                     527\
          Progressive Insurgency and the Election of 1912          530\
\
 XXII.  THE SPIRIT OF REFORM IN AMERICA                            536\
          An Age of Criticism                                      536\
          Political Reforms                                        538\
          Measures of Economic Reform                              546\
\
XXIII.  THE NEW POLITICAL DEMOCRACY                                554\
          The Rise of the Woman Movement                           555\
          The National Struggle for Woman Suffrage                 562\
\
 XXIV.  INDUSTRIAL DEMOCRACY                                       570\
          Cooperation between Employers and Employees              571\
          The Rise and Growth of Organized Labor                   575\
          The Wider Relations of Organized Labor                   577\
          Immigration and Americanization                          582\
\
  XXV.  PRESIDENT WILSON AND THE WORLD WAR                         588\
          Domestic Legislation                                     588\
          Colonial and Foreign Policies                            592\
          The United States and the European War                   596\
          The United States at War                                 604\
          The Settlement at Paris                                  612\
          Summary of Democracy and the World War                   620\
\
APPENDIX                                                           627\
\
A TOPICAL SYLLABUS                                                 645\
\
INDEX                                                              655\
\
\
\
\
MAPS\
\
\
                                                                   PAGE\
The Original Grants (color map)                         _Facing_     4\
\
German and Scotch-Irish Settlements                                  8\
\
Distribution of Population in 1790                                  27\
\
English, French, and Spanish Possessions in America, 1750\
      (color map)                                      _Facing_     59\
\
The Colonies at the Time of the Declaration of Independence\
      (color map)                                     _Facing_     108\
\
North America according to the Treaty of 1783\
      (color map)                                     _Facing_     134\
\
The United States in 1805 (color map)                 _Facing_     193\
\
Roads and Trails into Western Territory (color map)   _Facing_     224\
\
The Cumberland Road                                                233\
\
Distribution of Population in 1830                                 235\
\
Texas and the Territory in Dispute                                 282\
\
The Oregon Country and the Disputed Boundary                       285\
\
The Overland Trails                                                287\
\
Distribution of Slaves in Southern States                          323\
\
The Missouri Compromise                                            326\
\
Slave and Free Soil on the Eve of the Civil War                    335\
\
The United States in 1861 (color map)                 _Facing_     345\
\
Railroads of the United States in 1918                             405\
\
The United States in 1870 (color map)                _Facing_      427\
\
The United States in 1912 (color map)                _Facing_      443\
\
American Dominions in the Pacific (color map)        _Facing_      500\
\
The Caribbean Region (color map)                     _Facing_      592\
\
Battle Lines of the Various Years of the World War                 613\
\
Europe in 1919 (color map)                         _Between_   618-619\
\
     "THE NATIONS OF THE WEST" (popularly called "The\
     Pioneers"), designed by A. Stirling Calder and modeled by\
     Mr. Calder, F.G.R. Roth, and Leo Lentelli, topped the Arch\
     of the Setting Sun at the Panama-Pacific Exposition held at\
     San Francisco in 1915. Facing the Court of the Universe\
     moves a group of men and women typical of those who have\
     made our civilization. From left to right appear the\
     French-Canadian, the Alaskan, the Latin-American, the\
     German, the Italian, the Anglo-American, and the American\
     Indian, squaw and warrior. In the place of honor in the\
     center of the group, standing between the oxen on the tongue\
     of the prairie schooner, is a figure, beautiful and almost\
     girlish, but strong, dignified, and womanly, the Mother of\
     To-morrow. Above the group rides the Spirit of Enterprise,\
     flanked right and left by the Hopes of the Future in the\
     person of two boys. The group as a whole is beautifully\
     symbolic of the westward march of American civilization.\
\
[Illustration: _Photograph by Cardinell-Vincent Co., San Francisco_\
\
"THE NATIONS OF THE WEST"]\
\
\
\
\
HISTORY OF THE UNITED STATES\
\
\
\
\
PART I. THE COLONIAL PERIOD\
\
\
\
\
CHAPTER I\
\
THE GREAT MIGRATION TO AMERICA\
\
\
The tide of migration that set in toward the shores of North America\
during the early years of the seventeenth century was but one phase in\
the restless and eternal movement of mankind upon the surface of the\
earth. The ancient Greeks flung out their colonies in every direction,\
westward as far as Gaul, across the Mediterranean, and eastward into\
Asia Minor, perhaps to the very confines of India. The Romans, supported\
by their armies and their government, spread their dominion beyond the\
narrow lands of Italy until it stretched from the heather of Scotland to\
the sands of Arabia. The Teutonic tribes, from their home beyond the\
Danube and the Rhine, poured into the empire of the Caesars and made the\
beginnings of modern Europe. Of this great sweep of races and empires\
the settlement of America was merely a part. And it was, moreover, only\
one aspect of the expansion which finally carried the peoples, the\
institutions, and the trade of Europe to the very ends of the earth.\
\
In one vital point, it must be noted, American colonization differed\
from that of the ancients. The Greeks usually carried with them\
affection for the government they left behind and sacred fire from the\
altar of the parent city; but thousands of the immigrants who came to\
America disliked the state and disowned the church of the mother\
country. They established compacts of government for themselves and set\
up altars of their own. They sought not only new soil to till but also\
political and religious liberty for themselves and their children.\
\
\
THE AGENCIES OF AMERICAN COLONIZATION\
\
It was no light matter for the English to cross three thousand miles of\
water and found homes in the American wilderness at the opening of the\
seventeenth century. Ships, tools, and supplies called for huge outlays\
of money. Stores had to be furnished in quantities sufficient to sustain\
the life of the settlers until they could gather harvests of their own.\
Artisans and laborers of skill and industry had to be induced to risk\
the hazards of the new world. Soldiers were required for defense and\
mariners for the exploration of inland waters. Leaders of good judgment,\
adept in managing men, had to be discovered. Altogether such an\
enterprise demanded capital larger than the ordinary merchant or\
gentleman could amass and involved risks more imminent than he dared to\
assume. Though in later days, after initial tests had been made, wealthy\
proprietors were able to establish colonies on their own account, it was\
the corporation that furnished the capital and leadership in the\
beginning.\
\
=The Trading Company.=--English pioneers in exploration found an\
instrument for colonization in companies of merchant adventurers, which\
had long been employed in carrying on commerce with foreign countries.\
Such a corporation was composed of many persons of different ranks of\
society--noblemen, merchants, and gentlemen--who banded together for a\
particular undertaking, each contributing a sum of money and sharing in\
the profits of the venture. It was organized under royal authority; it\
received its charter, its grant of land, and its trading privileges from\
the king and carried on its operations under his supervision and\
control. The charter named all the persons originally included in the\
corporation and gave them certain powers in the management of its\
affairs, including the right to admit new members. The company was in\
fact a little government set up by the king. When the members of the\
corporation remained in England, as in the case of the Virginia Company,\
they operated through agents sent to the colony. When they came over the\
seas themselves and settled in America, as in the case of Massachusetts,\
they became the direct government of the country they possessed. The\
stockholders in that instance became the voters and the governor, the\
chief magistrate.\
\
[Illustration: JOHN WINTHROP, GOVERNOR OF THE MASSACHUSETTS BAY\
COMPANY]\
\
Four of the thirteen colonies in America owed their origins to the\
trading corporation. It was the London Company, created by King James I,\
in 1606, that laid during the following year the foundations of Virginia\
at Jamestown. It was under the auspices of their West India Company,\
chartered in 1621, that the Dutch planted the settlements of the New\
Netherland in the valley of the Hudson. The founders of Massachusetts\
were Puritan leaders and men of affairs whom King Charles I incorporated\
in 1629 under the title: "The governor and company of the Massachusetts\
Bay in New England." In this case the law did but incorporate a group\
drawn together by religious ties. "We must be knit together as one man,"\
wrote John Winthrop, the first Puritan governor in America. Far to the\
south, on the banks of the Delaware River, a Swedish commercial company\
in 1638 made the beginnings of a settlement, christened New Sweden; it\
was destined to pass under the rule of the Dutch, and finally under the\
rule of William Penn as the proprietary colony of Delaware.\
\
In a certain sense, Georgia may be included among the "company\
colonies." It was, however, originally conceived by the moving spirit,\
James Oglethorpe, as an asylum for poor men, especially those imprisoned\
for debt. To realize this humane purpose, he secured from King George\
II, in 1732, a royal charter uniting several gentlemen, including\
himself, into "one body politic and corporate," known as the "Trustees\
for establishing the colony of Georgia in America." In the structure of\
their organization and their methods of government, the trustees did not\
differ materially from the regular companies created for trade and\
colonization. Though their purposes were benevolent, their transactions\
had to be under the forms of law and according to the rules of business.\
\
=The Religious Congregation.=--A second agency which figured largely in\
the settlement of America was the religious brotherhood, or\
congregation, of men and women brought together in the bonds of a common\
religious faith. By one of the strange fortunes of history, this\
institution, founded in the early days of Christianity, proved to be a\
potent force in the origin and growth of self-government in a land far\
away from Galilee. "And the multitude of them that believed were of one\
heart and of one soul," we are told in the Acts describing the Church at\
Jerusalem. "We are knit together as a body in a most sacred covenant of\
the Lord ... by virtue of which we hold ourselves strictly tied to all\
care of each other's good and of the whole," wrote John Robinson, a\
leader among the Pilgrims who founded their tiny colony of Plymouth in\
1620. The Mayflower Compact, so famous in American history, was but a\
written and signed agreement, incorporating the spirit of obedience to\
the common good, which served as a guide to self-government until\
Plymouth was annexed to Massachusetts in 1691.\
\
[Illustration: THE ORIGINAL GRANTS]\
\
Three other colonies, all of which retained their identity until the eve\
of the American Revolution, likewise sprang directly from the\
congregations of the faithful: Rhode Island, Connecticut, and New\
Hampshire, mainly offshoots from Massachusetts. They were founded by\
small bodies of men and women, "united in solemn covenants with the\
Lord," who planted their settlements in the wilderness. Not until many a\
year after Roger Williams and Anne Hutchinson conducted their followers\
to the Narragansett country was Rhode Island granted a charter of\
incorporation (1663) by the crown. Not until long after the congregation\
of Thomas Hooker from Newtown blazed the way into the Connecticut River\
Valley did the king of England give Connecticut a charter of its own\
(1662) and a place among the colonies. Half a century elapsed before the\
towns laid out beyond the Merrimac River by emigrants from Massachusetts\
were formed into the royal province of New Hampshire in 1679.\
\
Even when Connecticut was chartered, the parchment and sealing wax of\
the royal lawyers did but confirm rights and habits of self-government\
and obedience to law previously established by the congregations. The\
towns of Hartford, Windsor, and Wethersfield had long lived happily\
under their "Fundamental Orders" drawn up by themselves in 1639; so had\
the settlers dwelt peacefully at New Haven under their "Fundamental\
Articles" drafted in the same year. The pioneers on the Connecticut\
shore had no difficulty in agreeing that "the Scriptures do hold forth a\
perfect rule for the direction and government of all men."\
\
=The Proprietor.=--A third and very important colonial agency was the\
proprietor, or proprietary. As the name, associated with the word\
"property," implies, the proprietor was a person to whom the king\
granted property in lands in North America to have, hold, use, and enjoy\
for his own benefit and profit, with the right to hand the estate down\
to his heirs in perpetual succession. The proprietor was a rich and\
powerful person, prepared to furnish or secure the capital, collect the\
ships, supply the stores, and assemble the settlers necessary to found\
and sustain a plantation beyond the seas. Sometimes the proprietor\
worked alone. Sometimes two or more were associated like partners in the\
common undertaking.\
\
Five colonies, Maryland, Pennsylvania, New Jersey, and the Carolinas,\
owe their formal origins, though not always their first settlements, nor\
in most cases their prosperity, to the proprietary system. Maryland,\
established in 1634 under a Catholic nobleman, Lord Baltimore, and\
blessed with religious toleration by the act of 1649, flourished under\
the mild rule of proprietors until it became a state in the American\
union. New Jersey, beginning its career under two proprietors, Berkeley\
and Carteret, in 1664, passed under the direct government of the crown\
in 1702. Pennsylvania was, in a very large measure, the product of the\
generous spirit and tireless labors of its first proprietor, the leader\
of the Friends, William Penn, to whom it was granted in 1681 and in\
whose family it remained until 1776. The two Carolinas were first\
organized as one colony in 1663 under the government and patronage of\
eight proprietors, including Lord Clarendon; but after more than half a\
century both became royal provinces governed by the king.\
\
[Illustration: WILLIAM PENN, PROPRIETOR OF PENNSYLVANIA]\
\
\
THE COLONIAL PEOPLES\
\
=The English.=--In leadership and origin the thirteen colonies, except\
New York and Delaware, were English. During the early days of all, save\
these two, the main, if not the sole, current of immigration was from\
England. The colonists came from every walk of life. They were men,\
women, and children of "all sorts and conditions." The major portion\
were yeomen, or small land owners, farm laborers, and artisans. With\
them were merchants and gentlemen who brought their stocks of goods or\
their fortunes to the New World. Scholars came from Oxford and\
Cambridge to preach the gospel or to teach. Now and then the son of an\
English nobleman left his baronial hall behind and cast his lot with\
America. The people represented every religious faith--members of the\
Established Church of England; Puritans who had labored to reform that\
church; Separatists, Baptists, and Friends, who had left it altogether;\
and Catholics, who clung to the religion of their fathers.\
\
New England was almost purely English. During the years between 1629 and\
1640, the period of arbitrary Stuart government, about twenty thousand\
Puritans emigrated to America, settling in the colonies of the far\
North. Although minor additions were made from time to time, the greater\
portion of the New England people sprang from this original stock.\
Virginia, too, for a long time drew nearly all her immigrants from\
England alone. Not until the eve of the Revolution did other\
nationalities, mainly the Scotch-Irish and Germans, rival the English in\
numbers.\
\
The populations of later English colonies--the Carolinas, New York,\
Pennsylvania, and Georgia--while receiving a steady stream of\
immigration from England, were constantly augmented by wanderers from\
the older settlements. New York was invaded by Puritans from New England\
in such numbers as to cause the Anglican clergymen there to lament that\
"free thinking spreads almost as fast as the Church." North Carolina was\
first settled toward the northern border by immigrants from Virginia.\
Some of the North Carolinians, particularly the Quakers, came all the\
way from New England, tarrying in Virginia only long enough to learn how\
little they were wanted in that Anglican colony.\
\
=The Scotch-Irish.=--Next to the English in numbers and influence were\
the Scotch-Irish, Presbyterians in belief, English in tongue. Both\
religious and economic reasons sent them across the sea. Their Scotch\
ancestors, in the days of Cromwell, had settled in the north of Ireland\
whence the native Irish had been driven by the conqueror's sword. There\
the Scotch nourished for many years enjoying in peace their own form of\
religion and growing prosperous in the manufacture of fine linen and\
woolen cloth. Then the blow fell. Toward the end of the seventeenth\
century their religious worship was put under the ban and the export of\
their cloth was forbidden by the English Parliament. Within two decades\
twenty thousand Scotch-Irish left Ulster alone, for America; and all\
during the eighteenth century the migration continued to be heavy.\
Although no exact record was kept, it is reckoned that the Scotch-Irish\
and the Scotch who came directly from Scotland, composed one-sixth of\
the entire American population on the eve of the Revolution.\
\
[Illustration: SETTLEMENTS OF GERMAN AND SCOTCH-IRISH\
IMMIGRANTS]\
\
These newcomers in America made their homes chiefly in New Jersey,\
Pennsylvania, Maryland, Virginia, and the Carolinas. Coming late upon\
the scene, they found much of the land immediately upon the seaboard\
already taken up. For this reason most of them became frontier people\
settling the interior and upland regions. There they cleared the land,\
laid out their small farms, and worked as "sturdy yeomen on the soil,"\
hardy, industrious, and independent in spirit, sharing neither the\
luxuries of the rich planters nor the easy life of the leisurely\
merchants. To their agriculture they added woolen and linen\
manufactures, which, flourishing in the supple fingers of their tireless\
women, made heavy inroads upon the trade of the English merchants in\
the colonies. Of their labors a poet has sung:\
\
        "O, willing hands to toil;\
    Strong natures tuned to the harvest-song and bound to the kindly soil;\
    Bold pioneers for the wilderness, defenders in the field."\
\
=The Germans.=--Third among the colonists in order of numerical\
importance were the Germans. From the very beginning, they appeared in\
colonial records. A number of the artisans and carpenters in the first\
Jamestown colony were of German descent. Peter Minuit, the famous\
governor of New Motherland, was a German from Wesel on the Rhine, and\
Jacob Leisler, leader of a popular uprising against the provincial\
administration of New York, was a German from Frankfort-on-Main. The\
wholesale migration of Germans began with the founding of Pennsylvania.\
Penn was diligent in searching for thrifty farmers to cultivate his\
lands and he made a special effort to attract peasants from the Rhine\
country. A great association, known as the Frankfort Company, bought\
more than twenty thousand acres from him and in 1684 established a\
center at Germantown for the distribution of German immigrants. In old\
New York, Rhinebeck-on-the-Hudson became a similar center for\
distribution. All the way from Maine to Georgia inducements were offered\
to the German farmers and in nearly every colony were to be found, in\
time, German settlements. In fact the migration became so large that\
German princes were frightened at the loss of so many subjects and\
England was alarmed by the influx of foreigners into her overseas\
dominions. Yet nothing could stop the movement. By the end of the\
colonial period, the number of Germans had risen to more than two\
hundred thousand.\
\
The majority of them were Protestants from the Rhine region, and South\
Germany. Wars, religious controversies, oppression, and poverty drove\
them forth to America. Though most of them were farmers, there were also\
among them skilled artisans who contributed to the rapid growth of\
industries in Pennsylvania. Their iron, glass, paper, and woolen mills,\
dotted here and there among the thickly settled regions, added to the\
wealth and independence of the province.\
\
[Illustration: _From an old print_\
\
A GLIMPSE OF OLD GERMANTOWN]\
\
Unlike the Scotch-Irish, the Germans did not speak the language of the\
original colonists or mingle freely with them. They kept to themselves,\
built their own schools, founded their own newspapers, and published\
their own books. Their clannish habits often irritated their neighbors\
and led to occasional agitations against "foreigners." However, no\
serious collisions seem to have occurred; and in the days of the\
Revolution, German soldiers from Pennsylvania fought in the patriot\
armies side by side with soldiers from the English and Scotch-Irish\
sections.\
\
=Other Nationalities.=--Though the English, the Scotch-Irish, and the\
Germans made up the bulk of the colonial population, there were other\
racial strains as well, varying in numerical importance but contributing\
their share to colonial life.\
\
From France came the Huguenots fleeing from the decree of the king which\
inflicted terrible penalties upon Protestants.\
\
From "Old Ireland" came thousands of native Irish, Celtic in race and\
Catholic in religion. Like their Scotch-Irish neighbors to the north,\
they revered neither the government nor the church of England imposed\
upon them by the sword. How many came we do not know, but shipping\
records of the colonial period show that boatload after boatload left\
the southern and eastern shores of Ireland for the New World.\
Undoubtedly thousands of their passengers were Irish of the native\
stock. This surmise is well sustained by the constant appearance of\
Celtic names in the records of various colonies.\
\
[Illustration:_From an old print_\
\
OLD DUTCH FORT AND ENGLISH CHURCH NEAR ALBANY]\
\
The Jews, then as ever engaged in their age-long battle for religious\
and economic toleration, found in the American colonies, not complete\
liberty, but certainly more freedom than they enjoyed in England,\
France, Spain, or Portugal. The English law did not actually recognize\
their right to live in any of the dominions, but owing to the easy-going\
habits of the Americans they were allowed to filter into the seaboard\
towns. The treatment they received there varied. On one occasion the\
mayor and council of New York forbade them to sell by retail and on\
another prohibited the exercise of their religious worship. Newport,\
Philadelphia, and Charleston were more hospitable, and there large\
Jewish colonies, consisting principally of merchants and their families,\
flourished in spite of nominal prohibitions of the law.\
\
Though the small Swedish colony in Delaware was quickly submerged\
beneath the tide of English migration, the Dutch in New York continued\
to hold their own for more than a hundred years after the English\
conquest in 1664. At the end of the colonial period over one-half of the\
170,000 inhabitants of the province were descendants of the original\
Dutch--still distinct enough to give a decided cast to the life and\
manners of New York. Many of them clung as tenaciously to their mother\
tongue as they did to their capacious farmhouses or their Dutch ovens;\
but they were slowly losing their identity as the English pressed in\
beside them to farm and trade.\
\
The melting pot had begun its historic mission.\
\
\
THE PROCESS OF COLONIZATION\
\
Considered from one side, colonization, whatever the motives of the\
emigrants, was an economic matter. It involved the use of capital to pay\
for their passage, to sustain them on the voyage, and to start them on\
the way of production. Under this stern economic necessity, Puritans,\
Scotch-Irish, Germans, and all were alike laid.\
\
=Immigrants Who Paid Their Own Way.=--Many of the immigrants to America\
in colonial days were capitalists themselves, in a small or a large way,\
and paid their own passage. What proportion of the colonists were able\
to finance their voyage across the sea is a matter of pure conjecture.\
Undoubtedly a very considerable number could do so, for we can trace the\
family fortunes of many early settlers. Henry Cabot Lodge is authority\
for the statement that "the settlers of New England were drawn from the\
country gentlemen, small farmers, and yeomanry of the mother\
country.... Many of the emigrants were men of wealth, as the old lists\
show, and all of them, with few exceptions, were men of property and\
good standing. They did not belong to the classes from which emigration\
is usually supplied, for they all had a stake in the country they left\
behind." Though it would be interesting to know how accurate this\
statement is or how applicable to the other colonies, no study has as\
yet been made to gratify that interest. For the present it is an\
unsolved problem just how many of the colonists were able to bear the\
cost of their own transfer to the New World.\
\
=Indentured Servants.=--That at least tens of thousands of immigrants\
were unable to pay for their passage is established beyond the shadow of\
a doubt by the shipping records that have come down to us. The great\
barrier in the way of the poor who wanted to go to America was the cost\
of the sea voyage. To overcome this difficulty a plan was worked out\
whereby shipowners and other persons of means furnished the passage\
money to immigrants in return for their promise, or bond, to work for a\
term of years to repay the sum advanced. This system was called\
indentured servitude.\
\
It is probable that the number of bond servants exceeded the original\
twenty thousand Puritans, the yeomen, the Virginia gentlemen, and the\
Huguenots combined. All the way down the coast from Massachusetts to\
Georgia were to be found in the fields, kitchens, and workshops, men,\
women, and children serving out terms of bondage generally ranging from\
five to seven years. In the proprietary colonies the proportion of bond\
servants was very high. The Baltimores, Penns, Carterets, and other\
promoters anxiously sought for workers of every nationality to till\
their fields, for land without labor was worth no more than land in the\
moon. Hence the gates of the proprietary colonies were flung wide open.\
Every inducement was offered to immigrants in the form of cheap land,\
and special efforts were made to increase the population by importing\
servants. In Pennsylvania, it was not uncommon to find a master with\
fifty bond servants on his estate. It has been estimated that two-thirds\
of all the immigrants into Pennsylvania between the opening of the\
eighteenth century and the outbreak of the Revolution were in bondage.\
In the other Middle colonies the number was doubtless not so large; but\
it formed a considerable part of the population.\
\
The story of this traffic in white servants is one of the most striking\
things in the history of labor. Bondmen differed from the serfs of the\
feudal age in that they were not bound to the soil but to the master.\
They likewise differed from the negro slaves in that their servitude had\
a time limit. Still they were subject to many special disabilities. It\
was, for instance, a common practice to impose on them penalties far\
heavier than were imposed upon freemen for the same offense. A free\
citizen of Pennsylvania who indulged in horse racing and gambling was\
let off with a fine; a white servant guilty of the same unlawful conduct\
was whipped at the post and fined as well.\
\
The ordinary life of the white servant was also severely restricted. A\
bondman could not marry without his master's consent; nor engage in\
trade; nor refuse work assigned to him. For an attempt to escape or\
indeed for any infraction of the law, the term of service was extended.\
The condition of white bondmen in Virginia, according to Lodge, "was\
little better than that of slaves. Loose indentures and harsh laws put\
them at the mercy of their masters." It would not be unfair to add that\
such was their lot in all other colonies. Their fate depended upon the\
temper of their masters.\
\
Cruel as was the system in many ways, it gave thousands of people in the\
Old World a chance to reach the New--an opportunity to wrestle with fate\
for freedom and a home of their own. When their weary years of servitude\
were over, if they survived, they might obtain land of their own or\
settle as free mechanics in the towns. For many a bondman the gamble\
proved to be a losing venture because he found himself unable to rise\
out of the state of poverty and dependence into which his servitude\
carried him. For thousands, on the contrary, bondage proved to be a real\
avenue to freedom and prosperity. Some of the best citizens of America\
have the blood of indentured servants in their veins.\
\
=The Transported--Involuntary Servitude.=--In their anxiety to secure\
settlers, the companies and proprietors having colonies in America\
either resorted to or connived at the practice of kidnapping men, women,\
and children from the streets of English cities. In 1680 it was\
officially estimated that "ten thousand persons were spirited away" to\
America. Many of the victims of the practice were young children, for\
the traffic in them was highly profitable. Orphans and dependents were\
sometimes disposed of in America by relatives unwilling to support them.\
In a single year, 1627, about fifteen hundred children were shipped to\
Virginia.\
\
In this gruesome business there lurked many tragedies, and very few\
romances. Parents were separated from their children and husbands from\
their wives. Hundreds of skilled artisans--carpenters, smiths, and\
weavers--utterly disappeared as if swallowed up by death. A few thus\
dragged off to the New World to be sold into servitude for a term of\
five or seven years later became prosperous and returned home with\
fortunes. In one case a young man who was forcibly carried over the sea\
lived to make his way back to England and establish his claim to a\
peerage.\
\
Akin to the kidnapped, at least in economic position, were convicts\
deported to the colonies for life in lieu of fines and imprisonment. The\
Americans protested vigorously but ineffectually against this practice.\
Indeed, they exaggerated its evils, for many of the "criminals" were\
only mild offenders against unduly harsh and cruel laws. A peasant\
caught shooting a rabbit on a lord's estate or a luckless servant girl\
who purloined a pocket handkerchief was branded as a criminal along with\
sturdy thieves and incorrigible rascals. Other transported offenders\
were "political criminals"; that is, persons who criticized or opposed\
the government. This class included now Irish who revolted against\
British rule in Ireland; now Cavaliers who championed the king against\
the Puritan revolutionists; Puritans, in turn, dispatched after the\
monarchy was restored; and Scotch and English subjects in general who\
joined in political uprisings against the king.\
\
=The African Slaves.=--Rivaling in numbers, in the course of time, the\
indentured servants and whites carried to America against their will\
were the African negroes brought to America and sold into slavery. When\
this form of bondage was first introduced into Virginia in 1619, it was\
looked upon as a temporary necessity to be discarded with the increase\
of the white population. Moreover it does not appear that those planters\
who first bought negroes at the auction block intended to establish a\
system of permanent bondage. Only by a slow process did chattel slavery\
take firm root and become recognized as the leading source of the labor\
supply. In 1650, thirty years after the introduction of slavery, there\
were only three hundred Africans in Virginia.\
\
The great increase in later years was due in no small measure to the\
inordinate zeal for profits that seized slave traders both in Old and in\
New England. Finding it relatively easy to secure negroes in Africa,\
they crowded the Southern ports with their vessels. The English Royal\
African Company sent to America annually between 1713 and 1743 from five\
to ten thousand slaves. The ship owners of New England were not far\
behind their English brethren in pushing this extraordinary traffic.\
\
As the proportion of the negroes to the free white population steadily\
rose, and as whole sections were overrun with slaves and slave traders,\
the Southern colonies grew alarmed. In 1710, Virginia sought to curtail\
the importation by placing a duty of $5 on each slave. This effort was\
futile, for the royal governor promptly vetoed it. From time to time\
similar bills were passed, only to meet with royal disapproval. South\
Carolina, in 1760, absolutely prohibited importation; but the measure\
was killed by the British crown. As late as 1772, Virginia, not daunted\
by a century of rebuffs, sent to George III a petition in this vein:\
"The importation of slaves into the colonies from the coast of Africa\
hath long been considered as a trade of great inhumanity and under its\
present encouragement, we have too much reason to fear, will endanger\
the very existence of Your Majesty's American dominions.... Deeply\
impressed with these sentiments, we most humbly beseech Your Majesty to\
remove all those restraints on Your Majesty's governors of this colony\
which inhibit their assenting to such laws as might check so very\
pernicious a commerce."\
\
All such protests were without avail. The negro population grew by leaps\
and bounds, until on the eve of the Revolution it amounted to more than\
half a million. In five states--Maryland, Virginia, the two Carolinas,\
and Georgia--the slaves nearly equalled or actually exceeded the whites\
in number. In South Carolina they formed almost two-thirds of the\
population. Even in the Middle colonies of Delaware and Pennsylvania\
about one-fifth of the inhabitants were from Africa. To the North, the\
proportion of slaves steadily diminished although chattel servitude was\
on the same legal footing as in the South. In New York approximately one\
in six and in New England one in fifty were negroes, including a few\
freedmen.\
\
The climate, the soil, the commerce, and the industry of the North were\
all unfavorable to the growth of a servile population. Still, slavery,\
though sectional, was a part of the national system of economy. Northern\
ships carried slaves to the Southern colonies and the produce of the\
plantations to Europe. "If the Northern states will consult their\
interest, they will not oppose the increase in slaves which will\
increase the commodities of which they will become the carriers," said\
John Rutledge, of South Carolina, in the convention which framed the\
Constitution of the United States. "What enriches a part enriches the\
whole and the states are the best judges of their particular interest,"\
responded Oliver Ellsworth, the distinguished spokesman of Connecticut.\
\
=References=\
\
E. Charming, _History of the United States_, Vols. I and II.\
\
J.A. Doyle, _The English Colonies in America_ (5 vols.).\
\
J. Fiske, _Old Virginia and Her Neighbors_ (2 vols.).\
\
A.B. Faust, _The German Element in the United States_ (2 vols.).\
\
H.J. Ford, _The Scotch-Irish in America_.\
\
L. Tyler, _England in America_ (American Nation Series).\
\
R. Usher, _The Pilgrims and Their History_.\
\
\
=Questions=\
\
1. America has been called a nation of immigrants. Explain why.\
\
2. Why were individuals unable to go alone to America in the beginning?\
What agencies made colonization possible? Discuss each of them.\
\
3. Make a table of the colonies, showing the methods employed in their\
settlement.\
\
4. Why were capital and leadership so very important in early\
colonization?\
\
5. What is meant by the "melting pot"? What nationalities were\
represented among the early colonists?\
\
6. Compare the way immigrants come to-day with the way they came in\
colonial times.\
\
7. Contrast indentured servitude with slavery and serfdom.\
\
8. Account for the anxiety of companies and proprietors to secure\
colonists.\
\
9. What forces favored the heavy importation of slaves?\
\
10. In what way did the North derive advantages from slavery?\
\
\
=Research Topics=\
\
=The Chartered Company.=--Compare the first and third charters of\
Virginia in Macdonald, _Documentary Source Book of American History_,\
1606-1898, pp. 1-14. Analyze the first and second Massachusetts charters\
in Macdonald, pp. 22-84. Special reference: W.A.S. Hewins, _English\
Trading Companies_.\
\
=Congregations and Compacts for Self-government.=--A study of the\
Mayflower Compact, the Fundamental Orders of Connecticut and the\
Fundamental Articles of New Haven in Macdonald, pp. 19, 36, 39.\
Reference: Charles Borgeaud, _Rise of Modern Democracy_, and C.S.\
Lobingier, _The People's Law_, Chaps. I-VII.\
\
=The Proprietary System.=--Analysis of Penn's charter of 1681, in\
Macdonald, p. 80. Reference: Lodge, _Short History of the English\
Colonies in America_, p. 211.\
\
=Studies of Individual Colonies.=--Review of outstanding events in\
history of each colony, using Elson, _History of the United States_, pp.\
55-159, as the basis.\
\
=Biographical Studies.=--John Smith, John Winthrop, William Penn, Lord\
Baltimore, William Bradford, Roger Williams, Anne Hutchinson, Thomas\
Hooker, and Peter Stuyvesant, using any good encyclopedia.\
\
=Indentured Servitude.=--In Virginia, Lodge, _Short History_, pp. 69-72;\
in Pennsylvania, pp. 242-244. Contemporary account in Callender,\
_Economic History of the United States_, pp. 44-51. Special reference:\
Karl Geiser, _Redemptioners and Indentured Servants_ (Yale Review, X,\
No. 2 Supplement).\
\
=Slavery.=--In Virginia, Lodge, _Short History_, pp. 67-69; in the\
Northern colonies, pp. 241, 275, 322, 408, 442.\
\
=The People of the Colonies.=--Virginia, Lodge, _Short History_, pp.\
67-73; New England, pp. 406-409, 441-450; Pennsylvania, pp. 227-229,\
240-250; New York, pp. 312-313, 322-335.\
\
\
\
\
CHAPTER II\
\
COLONIAL AGRICULTURE, INDUSTRY, AND COMMERCE\
\
THE LAND AND THE WESTWARD MOVEMENT\
\
\
=The Significance of Land Tenure.=--The way in which land may be\
acquired, held, divided among heirs, and bought and sold exercises a\
deep influence on the life and culture of a people. The feudal and\
aristocratic societies of Europe were founded on a system of landlordism\
which was characterized by two distinct features. In the first place,\
the land was nearly all held in great estates, each owned by a single\
proprietor. In the second place, every estate was kept intact under the\
law of primogeniture, which at the death of a lord transferred all his\
landed property to his eldest son. This prevented the subdivision of\
estates and the growth of a large body of small farmers or freeholders\
owning their own land. It made a form of tenantry or servitude\
inevitable for the mass of those who labored on the land. It also\
enabled the landlords to maintain themselves in power as a governing\
class and kept the tenants and laborers subject to their economic and\
political control. If land tenure was so significant in Europe, it was\
equally important in the development of America, where practically all\
the first immigrants were forced by circumstances to derive their\
livelihood from the soil.\
\
=Experiments in Common Tillage.=--In the New World, with its broad\
extent of land awaiting the white man's plow, it was impossible to\
introduce in its entirety and over the whole area the system of lords\
and tenants that existed across the sea. So it happened that almost\
every kind of experiment in land tenure, from communism to feudalism,\
was tried. In the early days of the Jamestown colony, the land, though\
owned by the London Company, was tilled in common by the settlers. No\
man had a separate plot of his own. The motto of the community was:\
"Labor and share alike." All were supposed to work in the fields and\
receive an equal share of the produce. At Plymouth, the Pilgrims\
attempted a similar experiment, laying out the fields in common and\
distributing the joint produce of their labor with rough equality among\
the workers.\
\
In both colonies the communistic experiments were failures. Angry at the\
lazy men in Jamestown who idled their time away and yet expected regular\
meals, Captain John Smith issued a manifesto: "Everyone that gathereth\
not every day as much as I do, the next day shall be set beyond the\
river and forever banished from the fort and live there or starve." Even\
this terrible threat did not bring a change in production. Not until\
each man was given a plot of his own to till, not until each gathered\
the fruits of his own labor, did the colony prosper. In Plymouth, where\
the communal experiment lasted for five years, the results were similar\
to those in Virginia, and the system was given up for one of separate\
fields in which every person could "set corn for his own particular."\
Some other New England towns, refusing to profit by the experience of\
their Plymouth neighbor, also made excursions into common ownership and\
labor, only to abandon the idea and go in for individual ownership of\
the land. "By degrees it was seen that even the Lord's people could not\
carry the complicated communist legislation into perfect and wholesome\
practice."\
\
=Feudal Elements in the Colonies--Quit Rents, Manors, and\
Plantations.=--At the other end of the scale were the feudal elements of\
land tenure found in the proprietary colonies, in the seaboard regions\
of the South, and to some extent in New York. The proprietor was in fact\
a powerful feudal lord, owning land granted to him by royal charter. He\
could retain any part of it for his personal use or dispose of it all in\
large or small lots. While he generally kept for himself an estate of\
baronial proportions, it was impossible for him to manage directly any\
considerable part of the land in his dominion. Consequently he either\
sold it in parcels for lump sums or granted it to individuals on\
condition that they make to him an annual payment in money, known as\
"quit rent." In Maryland, the proprietor sometimes collected as high as\
$9000 (equal to about $500,000 to-day) in a single year from this\
source. In Pennsylvania, the quit rents brought a handsome annual\
tribute into the exchequer of the Penn family. In the royal provinces,\
the king of England claimed all revenues collected in this form from the\
land, a sum amounting to $19,000 at the time of the Revolution. The quit\
rent,--"really a feudal payment from freeholders,"--was thus a material\
source of income for the crown as well as for the proprietors. Wherever\
it was laid, however, it proved to be a burden, a source of constant\
irritation; and it became a formidable item in the long list of\
grievances which led to the American Revolution.\
\
Something still more like the feudal system of the Old World appeared in\
the numerous manors or the huge landed estates granted by the crown, the\
companies, or the proprietors. In the colony of Maryland alone there\
were sixty manors of three thousand acres each, owned by wealthy men and\
tilled by tenants holding small plots under certain restrictions of\
tenure. In New York also there were many manors of wide extent, most of\
which originated in the days of the Dutch West India Company, when\
extensive concessions were made to patroons to induce them to bring over\
settlers. The Van Rensselaer, the Van Cortlandt, and the Livingston\
manors were so large and populous that each was entitled to send a\
representative to the provincial legislature. The tenants on the New\
York manors were in somewhat the same position as serfs on old European\
estates. They were bound to pay the owner a rent in money and kind; they\
ground their grain at his mill; and they were subject to his judicial\
power because he held court and meted out justice, in some instances\
extending to capital punishment.\
\
The manors of New York or Maryland were, however, of slight consequence\
as compared with the vast plantations of the Southern seaboard--huge\
estates, far wider in expanse than many a European barony and tilled by\
slaves more servile than any feudal tenants. It must not be forgotten\
that this system of land tenure became the dominant feature of a large\
section and gave a decided bent to the economic and political life of\
America.\
\
[Illustration: SOUTHERN PLANTATION MANSION]\
\
=The Small Freehold.=--In the upland regions of the South, however, and\
throughout most of the North, the drift was against all forms of\
servitude and tenantry and in the direction of the freehold; that is,\
the small farm owned outright and tilled by the possessor and his\
family. This was favored by natural circumstances and the spirit of the\
immigrants. For one thing, the abundance of land and the scarcity of\
labor made it impossible for the companies, the proprietors, or the\
crown to develop over the whole continent a network of vast estates. In\
many sections, particularly in New England, the climate, the stony soil,\
the hills, and the narrow valleys conspired to keep the farms within a\
moderate compass. For another thing, the English, Scotch-Irish, and\
German peasants, even if they had been tenants in the Old World, did not\
propose to accept permanent dependency of any kind in the New. If they\
could not get freeholds, they would not settle at all; thus they forced\
proprietors and companies to bid for their enterprise by selling land in\
small lots. So it happened that the freehold of modest proportions\
became the cherished unit of American farmers. The people who tilled the\
farms were drawn from every quarter of western Europe; but the freehold\
system gave a uniform cast to their economic and social life in America.\
\
[Illustration: _From an old print_\
\
A NEW ENGLAND FARMHOUSE]\
\
=Social Effects of Land Tenure.=--Land tenure and the process of western\
settlement thus developed two distinct types of people engaged in the\
same pursuit--agriculture. They had a common tie in that they both\
cultivated the soil and possessed the local interest and independence\
which arise from that occupation. Their methods and their culture,\
however, differed widely.\
\
The Southern planter, on his broad acres tilled by slaves, resembled the\
English landlord on his estates more than he did the colonial farmer who\
labored with his own hands in the fields and forests. He sold his rice\
and tobacco in large amounts directly to English factors, who took his\
entire crop in exchange for goods and cash. His fine clothes,\
silverware, china, and cutlery he bought in English markets. Loving the\
ripe old culture of the mother country, he often sent his sons to Oxford\
or Cambridge for their education. In short, he depended very largely for\
his prosperity and his enjoyment of life upon close relations with the\
Old World. He did not even need market towns in which to buy native\
goods, for they were made on his own plantation by his own artisans who\
were usually gifted slaves.\
\
The economic condition of the small farmer was totally different. His\
crops were not big enough to warrant direct connection with English\
factors or the personal maintenance of a corps of artisans. He needed\
local markets, and they sprang up to meet the need. Smiths, hatters,\
weavers, wagon-makers, and potters at neighboring towns supplied him\
with the rough products of their native skill. The finer goods, bought\
by the rich planter in England, the small farmer ordinarily could not\
buy. His wants were restricted to staples like tea and sugar, and\
between him and the European market stood the merchant. His community\
was therefore more self-sufficient than the seaboard line of great\
plantations. It was more isolated, more provincial, more independent,\
more American. The planter faced the Old East. The farmer faced the New\
West.\
\
=The Westward Movement.=--Yeoman and planter nevertheless were alike in\
one respect. Their land hunger was never appeased. Each had the eye of\
an expert for new and fertile soil; and so, north and south, as soon as\
a foothold was secured on the Atlantic coast, the current of migration\
set in westward, creeping through forests, across rivers, and over\
mountains. Many of the later immigrants, in their search for cheap\
lands, were compelled to go to the border; but in a large part the path\
breakers to the West were native Americans of the second and third\
generations. Explorers, fired by curiosity and the lure of the\
mysterious unknown, and hunters, fur traders, and squatters, following\
their own sweet wills, blazed the trail, opening paths and sending back\
stories of the new regions they traversed. Then came the regular\
settlers with lawful titles to the lands they had purchased, sometimes\
singly and sometimes in companies.\
\
In Massachusetts, the westward movement is recorded in the founding of\
Springfield in 1636 and Great Barrington in 1725. By the opening of the\
eighteenth century the pioneers of Connecticut had pushed north and west\
until their outpost towns adjoined the Hudson Valley settlements. In New\
York, the inland movement was directed by the Hudson River to Albany,\
and from that old Dutch center it radiated in every direction,\
particularly westward through the Mohawk Valley. New Jersey was early\
filled to its borders, the beginnings of the present city of New\
Brunswick being made in 1681 and those of Trenton in 1685. In\
Pennsylvania, as in New York, the waterways determined the main lines of\
advance. Pioneers, pushing up through the valley of the Schuylkill,\
spread over the fertile lands of Berks and Lancaster counties, laying\
out Reading in 1748. Another current of migration was directed by the\
Susquehanna, and, in 1726, the first farmhouse was built on the bank\
where Harrisburg was later founded. Along the southern tier of counties\
a thin line of settlements stretched westward to Pittsburgh, reaching\
the upper waters of the Ohio while the colony was still under the Penn\
family.\
\
In the South the westward march was equally swift. The seaboard was\
quickly occupied by large planters and their slaves engaged in the\
cultivation of tobacco and rice. The Piedmont Plateau, lying back from\
the coast all the way from Maryland to Georgia, was fed by two streams\
of migration, one westward from the sea and the other southward from the\
other colonies--Germans from Pennsylvania and Scotch-Irish furnishing\
the main supply. "By 1770, tide-water Virginia was full to overflowing\
and the 'back country' of the Blue Ridge and the Shenandoah was fully\
occupied. Even the mountain valleys ... were claimed by sturdy pioneers.\
Before the Declaration of Independence, the oncoming tide of\
home-seekers had reached the crest of the Alleghanies."\
\
[Illustration: DISTRIBUTION OF POPULATION, 1790]\
\
Beyond the mountains pioneers had already ventured, harbingers of an\
invasion that was about to break in upon Kentucky and Tennessee. As\
early as 1769 that mighty Nimrod, Daniel Boone, curious to hunt\
buffaloes, of which he had heard weird reports, passed through the\
Cumberland Gap and brought back news of a wonderful country awaiting the\
plow. A hint was sufficient. Singly, in pairs, and in groups, settlers\
followed the trail he had blazed. A great land corporation, the\
Transylvania Company, emulating the merchant adventurers of earlier\
times, secured a huge grant of territory and sought profits in quit\
rents from lands sold to farmers. By the outbreak of the Revolution\
there were several hundred people in the Kentucky region. Like the older\
colonists, they did not relish quit rents, and their opposition wrecked\
the Transylvania Company. They even carried their protests into the\
Continental Congress in 1776, for by that time they were our "embryo\
fourteenth colony."\
\
\
INDUSTRIAL AND COMMERCIAL DEVELOPMENT\
\
Though the labor of the colonists was mainly spent in farming, there was\
a steady growth in industrial and commercial pursuits. Most of the\
staple industries of to-day, not omitting iron and textiles, have their\
beginnings in colonial times. Manufacturing and trade soon gave rise to\
towns which enjoyed an importance all out of proportion to their\
numbers. The great centers of commerce and finance on the seaboard\
originated in the days when the king of England was "lord of these\
dominions."\
\
[Illustration: DOMESTIC INDUSTRY: DIPPING TALLOW CANDLES]\
\
=Textile Manufacture as a Domestic Industry.=--Colonial women, in\
addition to sharing every hardship of pioneering, often the heavy labor\
of the open field, developed in the course of time a national industry\
which was almost exclusively their own. Wool and flax were raised in\
abundance in the North and South. "Every farm house," says Coman, the\
economic historian, "was a workshop where the women spun and wove the\
serges, kerseys, and linsey-woolseys which served for the common wear."\
By the close of the seventeenth century, New England manufactured cloth\
in sufficient quantities to export it to the Southern colonies and to\
the West Indies. As the industry developed, mills were erected for the\
more difficult process of dyeing, weaving, and fulling, but carding and\
spinning continued to be done in the home. The Dutch of New Netherland,\
the Swedes of Delaware, and the Scotch-Irish of the interior "were not\
one whit behind their Yankee neighbors."\
\
The importance of this enterprise to British economic life can hardly be\
overestimated. For many a century the English had employed their fine\
woolen cloth as the chief staple in a lucrative foreign trade, and the\
government had come to look upon it as an object of special interest and\
protection. When the colonies were established, both merchants and\
statesmen naturally expected to maintain a monopoly of increasing value;\
but before long the Americans, instead of buying cloth, especially of\
the coarser varieties, were making it to sell. In the place of\
customers, here were rivals. In the place of helpless reliance upon\
English markets, here was the germ of economic independence.\
\
If British merchants had not discovered it in the ordinary course of\
trade, observant officers in the provinces would have conveyed the news\
to them. Even in the early years of the eighteenth century the royal\
governor of New York wrote of the industrious Americans to his home\
government: "The consequence will be that if they can clothe themselves\
once, not only comfortably, but handsomely too, without the help of\
England, they who already are not very fond of submitting to government\
will soon think of putting in execution designs they have long harboured\
in their breasts. This will not seem strange when you consider what sort\
of people this country is inhabited by."\
\
=The Iron Industry.=--Almost equally widespread was the art of iron\
working--one of the earliest and most picturesque of colonial\
industries. Lynn, Massachusetts, had a forge and skilled artisans within\
fifteen years after the founding of Boston. The smelting of iron began\
at New London and New Haven about 1658; in Litchfield county,\
Connecticut, a few years later; at Great Barrington, Massachusetts, in\
1731; and near by at Lenox some thirty years after that. New Jersey had\
iron works at Shrewsbury within ten years after the founding of the\
colony in 1665. Iron forges appeared in the valleys of the Delaware and\
the Susquehanna early in the following century, and iron masters then\
laid the foundations of fortunes in a region destined to become one of\
the great iron centers of the world. Virginia began iron working in the\
year that saw the introduction of slavery. Although the industry soon\
lapsed, it was renewed and flourished in the eighteenth century.\
Governor Spotswood was called the "Tubal Cain" of the Old Dominion\
because he placed the industry on a firm foundation. Indeed it seems\
that every colony, except Georgia, had its iron foundry. Nails, wire,\
metallic ware, chains, anchors, bar and pig iron were made in large\
quantities; and Great Britain, by an act in 1750, encouraged the\
colonists to export rough iron to the British Islands.\
\
=Shipbuilding.=--Of all the specialized industries in the colonies,\
shipbuilding was the most important. The abundance of fir for masts, oak\
for timbers and boards, pitch for tar and turpentine, and hemp for rope\
made the way of the shipbuilder easy. Early in the seventeenth century a\
ship was built at New Amsterdam, and by the middle of that century\
shipyards were scattered along the New England coast at Newburyport,\
Salem, New Bedford, Newport, Providence, New London, and New Haven.\
Yards at Albany and Poughkeepsie in New York built ships for the trade\
of that colony with England and the Indies. Wilmington and Philadelphia\
soon entered the race and outdistanced New York, though unable to equal\
the pace set by New England. While Maryland, Virginia, and South\
Carolina also built ships, Southern interest was mainly confined to the\
lucrative business of producing ship materials: fir, cedar, hemp, and\
tar.\
\
=Fishing.=--The greatest single economic resource of New England outside\
of agriculture was the fisheries. This industry, started by hardy\
sailors from Europe, long before the landing of the Pilgrims, flourished\
under the indomitable seamanship of the Puritans, who labored with the\
net and the harpoon in almost every quarter of the Atlantic. "Look,"\
exclaimed Edmund Burke, in the House of Commons, "at the manner in\
which the people of New England have of late carried on the whale\
fishery. Whilst we follow them among the tumbling mountains of ice and\
behold them penetrating into the deepest frozen recesses of Hudson's Bay\
and Davis's Straits, while we are looking for them beneath the arctic\
circle, we hear that they have pierced into the opposite region of polar\
cold, that they are at the antipodes and engaged under the frozen\
serpent of the south.... Nor is the equinoctial heat more discouraging\
to them than the accumulated winter of both poles. We know that, whilst\
some of them draw the line and strike the harpoon on the coast of\
Africa, others run the longitude and pursue their gigantic game along\
the coast of Brazil. No sea but what is vexed by their fisheries. No\
climate that is not witness to their toils. Neither the perseverance of\
Holland nor the activity of France nor the dexterous and firm sagacity\
of English enterprise ever carried this most perilous mode of hard\
industry to the extent to which it has been pushed by this recent\
people."\
\
The influence of the business was widespread. A large and lucrative\
European trade was built upon it. The better quality of the fish caught\
for food was sold in the markets of Spain, Portugal, and Italy, or\
exchanged for salt, lemons, and raisins for the American market. The\
lower grades of fish were carried to the West Indies for slave\
consumption, and in part traded for sugar and molasses, which furnished\
the raw materials for the thriving rum industry of New England. These\
activities, in turn, stimulated shipbuilding, steadily enlarging the\
demand for fishing and merchant craft of every kind and thus keeping the\
shipwrights, calkers, rope makers, and other artisans of the seaport\
towns rushed with work. They also increased trade with the mother\
country for, out of the cash collected in the fish markets of Europe and\
the West Indies, the colonists paid for English manufactures. So an\
ever-widening circle of American enterprise centered around this single\
industry, the nursery of seamanship and the maritime spirit.\
\
=Oceanic Commerce and American Merchants.=--All through the eighteenth\
century, the commerce of the American colonies spread in every direction\
until it rivaled in the number of people employed, the capital engaged,\
and the profits gleaned, the commerce of European nations. A modern\
historian has said: "The enterprising merchants of New England developed\
a network of trade routes that covered well-nigh half the world." This\
commerce, destined to be of such significance in the conflict with the\
mother country, presented, broadly speaking, two aspects.\
\
On the one side, it involved the export of raw materials and\
agricultural produce. The Southern colonies produced for shipping,\
tobacco, rice, tar, pitch, and pine; the Middle colonies, grain, flour,\
furs, lumber, and salt pork; New England, fish, flour, rum, furs, shoes,\
and small articles of manufacture. The variety of products was in fact\
astounding. A sarcastic writer, while sneering at the idea of an\
American union, once remarked of colonial trade: "What sort of dish will\
you make? New England will throw in fish and onions. The middle states,\
flax-seed and flour. Maryland and Virginia will add tobacco. North\
Carolina, pitch, tar, and turpentine. South Carolina, rice and indigo,\
and Georgia will sprinkle the whole composition with sawdust. Such an\
absurd jumble will you make if you attempt to form a union among such\
discordant materials as the thirteen British provinces."\
\
On the other side, American commerce involved the import trade,\
consisting principally of English and continental manufactures, tea, and\
"India goods." Sugar and molasses, brought from the West Indies,\
supplied the flourishing distilleries of Massachusetts, Rhode Island,\
and Connecticut. The carriage of slaves from Africa to the Southern\
colonies engaged hundreds of New England's sailors and thousands of\
pounds of her capital.\
\
The disposition of imported goods in the colonies, though in part\
controlled by English factors located in America, employed also a large\
and important body of American merchants like the Willings and Morrises\
of Philadelphia; the Amorys, Hancocks, and Faneuils of Boston; and the\
Livingstons and Lows of New York. In their zeal and enterprise, they\
were worthy rivals of their English competitors, so celebrated for\
world-wide commercial operations. Though fully aware of the advantages\
they enjoyed in British markets and under the protection of the British\
navy, the American merchants were high-spirited and mettlesome, ready to\
contend with royal officers in order to shield American interests\
against outside interference.\
\
[Illustration: THE DUTCH WEST INDIA WAREHOUSE IN NEW AMSTERDAM\
(NEW YORK CITY)]\
\
Measured against the immense business of modern times, colonial commerce\
seems perhaps trivial. That, however, is not the test of its\
significance. It must be considered in relation to the growth of English\
colonial trade in its entirety--a relation which can be shown by a few\
startling figures. The whole export trade of England, including that to\
the colonies, was, in 1704, $6,509,000. On the eve of the American\
Revolution, namely, in 1772, English exports to the American colonies\
alone amounted to $6,024,000; in other words, almost as much as the\
whole foreign business of England two generations before. At the first\
date, colonial trade was but one-twelfth of the English export business;\
at the second date, it was considerably more than one-third. In 1704,\
Pennsylvania bought in English markets goods to the value of $11,459; in\
1772 the purchases of the same colony amounted to $507,909. In short,\
Pennsylvania imports increased fifty times within sixty-eight years,\
amounting in 1772 to almost the entire export trade of England to the\
colonies at the opening of the century. The American colonies were\
indeed a great source of wealth to English merchants.\
\
=Intercolonial Commerce.=--Although the bad roads of colonial times made\
overland transportation difficult and costly, the many rivers and\
harbors along the coast favored a lively water-borne trade among the\
colonies. The Connecticut, Hudson, Delaware, and Susquehanna rivers in\
the North and the many smaller rivers in the South made it possible for\
goods to be brought from, and carried to, the interior regions in little\
sailing vessels with comparative ease. Sloops laden with manufactures,\
domestic and foreign, collected at some city like Providence, New York,\
or Philadelphia, skirted the coasts, visited small ports, and sailed up\
the navigable rivers to trade with local merchants who had for exchange\
the raw materials which they had gathered in from neighboring farms.\
Larger ships carried the grain, live stock, cloth, and hardware of New\
England to the Southern colonies, where they were traded for tobacco,\
leather, tar, and ship timber. From the harbors along the Connecticut\
shores there were frequent sailings down through Long Island Sound to\
Maryland, Virginia, and the distant Carolinas.\
\
=Growth of Towns.=--In connection with this thriving trade and industry\
there grew up along the coast a number of prosperous commercial centers\
which were soon reckoned among the first commercial towns of the whole\
British empire, comparing favorably in numbers and wealth with such\
ports as Liverpool and Bristol. The statistical records of that time are\
mainly guesses; but we know that Philadelphia stood first in size among\
these towns. Serving as the port of entry for Pennsylvania, Delaware,\
and western Jersey, it had drawn within its borders, just before the\
Revolution, about 25,000 inhabitants. Boston was second in rank, with\
somewhat more than 20,000 people. New York, the "commercial capital of\
Connecticut and old East Jersey," was slightly smaller than Boston, but\
growing at a steady rate. The fourth town in size was Charleston, South\
Carolina, with about 10,000 inhabitants. Newport in Rhode Island, a\
center of rum manufacture and shipping, stood fifth, with a population\
of about 7000. Baltimore and Norfolk were counted as "considerable\
towns." In the interior, Hartford in Connecticut, Lancaster and York in\
Pennsylvania, and Albany in New York, with growing populations and\
increasing trade, gave prophecy of an urban America away from the\
seaboard. The other towns were straggling villages. Williamsburg,\
Virginia, for example, had about two hundred houses, in which dwelt a\
dozen families of the gentry and a few score of tradesmen. Inland county\
seats often consisted of nothing more than a log courthouse, a prison,\
and one wretched inn to house judges, lawyers, and litigants during the\
sessions of the court.\
\
The leading towns exercised an influence on colonial opinion all out of\
proportion to their population. They were the centers of wealth, for one\
thing; of the press and political activity, for another. Merchants and\
artisans could readily take concerted action on public questions arising\
from their commercial operations. The towns were also centers for news,\
gossip, religious controversy, and political discussion. In the market\
places the farmers from the countryside learned of British policies and\
laws, and so, mingling with the townsmen, were drawn into the main\
currents of opinion which set in toward colonial nationalism and\
independence.\
\
\
=References=\
\
J. Bishop, _History of American Manufactures_ (2 vols.).\
\
E.L. Bogart, _Economic History of the United States_.\
\
P.A. Bruce, _Economic History of Virginia_ (2 vols.).\
\
E. Semple, _American History and Its Geographical Conditions_.\
\
W. Weeden, _Economic and Social History of New England_. (2 vols.).\
\
\
=Questions=\
\
1. Is land in your community parceled out into small farms? Contrast the\
system in your community with the feudal system of land tenure.\
\
2. Are any things owned and used in common in your community? Why did\
common tillage fail in colonial times?\
\
3. Describe the elements akin to feudalism which were introduced in the\
colonies.\
\
4. Explain the success of freehold tillage.\
\
5. Compare the life of the planter with that of the farmer.\
\
6. How far had the western frontier advanced by 1776?\
\
7. What colonial industry was mainly developed by women? Why was it very\
important both to the Americans and to the English?\
\
8. What were the centers for iron working? Ship building?\
\
9. Explain how the fisheries affected many branches of trade and\
industry.\
\
10. Show how American trade formed a vital part of English business.\
\
11. How was interstate commerce mainly carried on?\
\
12. What were the leading towns? Did they compare in importance with\
British towns of the same period?\
\
\
=Research Topics=\
\
=Land Tenure.=--Coman, _Industrial History_ (rev. ed.), pp. 32-38.\
Special reference: Bruce, _Economic History of Virginia_, Vol. I, Chap.\
VIII.\
\
=Tobacco Planting in Virginia.=--Callender, _Economic History of the\
United States_, pp. 22-28.\
\
=Colonial Agriculture.=--Coman, pp. 48-63. Callender, pp. 69-74.\
Reference: J.R.H. Moore, _Industrial History of the American People_,\
pp. 131-162.\
\
=Colonial Manufactures.=--Coman, pp. 63-73. Callender, pp. 29-44.\
Special reference: Weeden, _Economic and Social History of New England_.\
\
=Colonial Commerce.=--Coman, pp. 73-85. Callender, pp. 51-63, 78-84.\
Moore, pp. 163-208. Lodge, _Short History of the English Colonies_, pp.\
409-412, 229-231, 312-314.\
\
\
\
\
Chapter III\
\
SOCIAL AND POLITICAL PROGRESS\
\
\
Colonial life, crowded as it was with hard and unremitting toil, left\
scant leisure for the cultivation of the arts and sciences. There was\
little money in private purses or public treasuries to be dedicated to\
schools, libraries, and museums. Few there were with time to read long\
and widely, and fewer still who could devote their lives to things that\
delight the eye and the mind. And yet, poor and meager as the\
intellectual life of the colonists may seem by way of comparison, heroic\
efforts were made in every community to lift the people above the plane\
of mere existence. After the first clearings were opened in the forests\
those efforts were redoubled, and with lengthening years told upon the\
thought and spirit of the land. The appearance, during the struggle with\
England, of an extraordinary group of leaders familiar with history,\
political philosophy, and the arts of war, government, and diplomacy\
itself bore eloquent testimony to the high quality of the American\
intellect. No one, not even the most critical, can run through the\
writings of distinguished Americans scattered from Massachusetts to\
Georgia--the Adamses, Ellsworth, the Morrises, the Livingstons,\
Hamilton, Franklin, Washington, Madison, Marshall, Henry, the Randolphs,\
and the Pinckneys--without coming to the conclusion that there was\
something in American colonial life which fostered minds of depth and\
power. Women surmounted even greater difficulties than the men in the\
process of self-education, and their keen interest in public issues is\
evident in many a record like the _Letters_ of Mrs. John Adams to her\
husband during the Revolution; the writings of Mrs. Mercy Otis Warren,\
the sister of James Otis, who measured her pen with the British\
propagandists; and the patriot newspapers founded and managed by women.\
\
\
THE LEADERSHIP OF THE CHURCHES\
\
In the intellectual life of America, the churches assumed a role of high\
importance. There were abundant reasons for this. In many of the\
colonies--Maryland, Pennsylvania, and New England--the religious impulse\
had been one of the impelling motives in stimulating immigration. In all\
the colonies, the clergy, at least in the beginning, formed the only\
class with any leisure to devote to matters of the spirit. They preached\
on Sundays and taught school on week days. They led in the discussion of\
local problems and in the formation of political opinion, so much of\
which was concerned with the relation between church and state. They\
wrote books and pamphlets. They filled most of the chairs in the\
colleges; under clerical guidance, intellectual and spiritual, the\
Americans received their formal education. In several of the provinces\
the Anglican Church was established by law. In New England the Puritans\
were supreme, notwithstanding the efforts of the crown to overbear their\
authority. In the Middle colonies, particularly, the multiplication of\
sects made the dominance of any single denomination impossible; and in\
all of them there was a growing diversity of faith, which promised in\
time a separation of church and state and freedom of opinion.\
\
=The Church of England.=--Virginia was the stronghold of the English\
system of church and state. The Anglican faith and worship were\
prescribed by law, sustained by taxes imposed on all, and favored by the\
governor, the provincial councilors, and the richest planters. "The\
Established Church," says Lodge, "was one of the appendages of the\
Virginia aristocracy. They controlled the vestries and the ministers,\
and the parish church stood not infrequently on the estate of the\
planter who built and managed it." As in England, Catholics and\
Protestant Dissenters were at first laid under heavy disabilities. Only\
slowly and on sufferance were they admitted to the province; but when\
once they were even covertly tolerated, they pressed steadily in, until,\
by the Revolution, they outnumbered the adherents of the established\
order.\
\
The Church was also sanctioned by law and supported by taxes in the\
Carolinas after 1704, and in Georgia after that colony passed directly\
under the crown in 1754--this in spite of the fact that the majority of\
the inhabitants were Dissenters. Against the protests of the Catholics\
it was likewise established in Maryland. In New York, too,\
notwithstanding the resistance of the Dutch, the Established Church was\
fostered by the provincial officials, and the Anglicans, embracing about\
one-fifteenth of the population, exerted an influence all out of\
proportion to their numbers.\
\
Many factors helped to enhance the power of the English Church in the\
colonies. It was supported by the British government and the official\
class sent out to the provinces. Its bishops and archbishops in England\
were appointed by the king, and its faith and service were set forth by\
acts of Parliament. Having its seat of power in the English monarchy, it\
could hold its clergy and missionaries loyal to the crown and so\
counteract to some extent the independent spirit that was growing up in\
America. The Church, always a strong bulwark of the state, therefore had\
a political role to play here as in England. Able bishops and far-seeing\
leaders firmly grasped this fact about the middle of the eighteenth\
century and redoubled their efforts to augment the influence of the\
Church in provincial affairs. Unhappily for their plans they failed to\
calculate in advance the effect of their methods upon dissenting\
Protestants, who still cherished memories of bitter religious conflicts\
in the mother country.\
\
=Puritanism in New England.=--If the established faith made for imperial\
unity, the same could not be said of Puritanism. The Plymouth Pilgrims\
had cast off all allegiance to the Anglican Church and established a\
separate and independent congregation before they came to America. The\
Puritans, essaying at first the task of reformers within the Church,\
soon after their arrival in Massachusetts, likewise flung off their yoke\
of union with the Anglicans. In each town a separate congregation was\
organized, the male members choosing the pastor, the teachers, and the\
other officers. They also composed the voters in the town meeting, where\
secular matters were determined. The union of church and government was\
thus complete, and uniformity of faith and life prescribed by law and\
enforced by civil authorities; but this worked for local autonomy\
instead of imperial unity.\
\
The clergy became a powerful class, dominant through their learning and\
their fearful denunciations of the faithless. They wrote the books for\
the people to read--the famous Cotton Mather having three hundred and\
eighty-three books and pamphlets to his credit. In cooperation with the\
civil officers they enforced a strict observance of the Puritan\
Sabbath--a day of rest that began at six o'clock on Saturday evening and\
lasted until sunset on Sunday. All work, all trading, all amusement, and\
all worldly conversation were absolutely prohibited during those hours.\
A thoughtless maid servant who for some earthly reason smiled in church\
was in danger of being banished as a vagabond. Robert Pike, a devout\
Puritan, thinking the sun had gone to rest, ventured forth on horseback\
one Sunday evening and was luckless enough to have a ray of light strike\
him through a rift in the clouds. The next day he was brought into court\
and fined for "his ungodly conduct." With persons accused of witchcraft\
the Puritans were still more ruthless. When a mania of persecution swept\
over Massachusetts in 1692, eighteen people were hanged, one was pressed\
to death, many suffered imprisonment, and two died in jail.\
\
Just about this time, however, there came a break in the uniformity of\
Puritan rule. The crown and church in England had long looked upon it\
with disfavor, and in 1684 King Charles II annulled the old charter of\
the Massachusetts Bay Company. A new document issued seven years later\
wrested from the Puritans of the colony the right to elect their own\
governor and reserved the power of appointment to the king. It also\
abolished the rule limiting the suffrage to church members, substituting\
for it a simple property qualification. Thus a royal governor and an\
official family, certain to be Episcopalian in faith and monarchist in\
sympathies, were forced upon Massachusetts; and members of all religious\
denominations, if they had the required amount of property, were\
permitted to take part in elections. By this act in the name of the\
crown, the Puritan monopoly was broken down in Massachusetts, and that\
province was brought into line with Connecticut, Rhode Island, and New\
Hampshire, where property, not religious faith, was the test for the\
suffrage.\
\
=Growth of Religious Toleration.=--Though neither the Anglicans of\
Virginia nor the Puritans of Massachusetts believed in toleration for\
other denominations, that principle was strictly applied in Rhode\
Island. There, under the leadership of Roger Williams, liberty in\
matters of conscience was established in the beginning. Maryland, by\
granting in 1649 freedom to those who professed to believe in Jesus\
Christ, opened its gates to all Christians; and Pennsylvania, true to\
the tenets of the Friends, gave freedom of conscience to those "who\
confess and acknowledge the one Almighty and Eternal God to be the\
creator, upholder, and ruler of the World." By one circumstance or\
another, the Middle colonies were thus early characterized by diversity\
rather than uniformity of opinion. Dutch Protestants, Huguenots,\
Quakers, Baptists, Presbyterians, New Lights, Moravians, Lutherans,\
Catholics, and other denominations became too strongly intrenched and\
too widely scattered to permit any one of them to rule, if it had\
desired to do so. There were communities and indeed whole sections where\
one or another church prevailed, but in no colony was a legislature\
steadily controlled by a single group. Toleration encouraged diversity,\
and diversity, in turn, worked for greater toleration.\
\
The government and faith of the dissenting denominations conspired with\
economic and political tendencies to draw America away from the English\
state. Presbyterians, Quakers, Baptists, and Puritans had no hierarchy\
of bishops and archbishops to bind them to the seat of power in London.\
Neither did they look to that metropolis for guidance in interpreting\
articles of faith. Local self-government in matters ecclesiastical\
helped to train them for local self-government in matters political. The\
spirit of independence which led Dissenters to revolt in the Old World,\
nourished as it was amid favorable circumstances in the New World, made\
them all the more zealous in the defense of every right against\
authority imposed from without.\
\
\
SCHOOLS AND COLLEGES\
\
=Religion and Local Schools.=--One of the first cares of each Protestant\
denomination was the education of the children in the faith. In this\
work the Bible became the center of interest. The English version was\
indeed the one book of the people. Farmers, shopkeepers, and artisans,\
whose life had once been bounded by the daily routine of labor, found in\
the Scriptures not only an inspiration to religious conduct, but also a\
book of romance, travel, and history. "Legend and annal," says John\
Richard Green, "war-song and psalm, state-roll and biography, the mighty\
voices of prophets, the parables of Evangelists, stories of mission\
journeys, of perils by sea and among the heathen, philosophic arguments,\
apocalyptic visions, all were flung broadcast over minds unoccupied for\
the most part by any rival learning.... As a mere literary monument, the\
English version of the Bible remains the noblest example of the English\
tongue." It was the King James version just from the press that the\
Pilgrims brought across the sea with them.\
\
For the authority of the Established Church was substituted the\
authority of the Scriptures. The Puritans devised a catechism based upon\
their interpretation of the Bible, and, very soon after their arrival in\
America, they ordered all parents and masters of servants to be diligent\
in seeing that their children and wards were taught to read religious\
works and give answers to the religious questions. Massachusetts was\
scarcely twenty years old before education of this character was\
declared to be compulsory, and provision was made for public schools\
where those not taught at home could receive instruction in reading and\
writing.\
\
[Illustration: A PAGE FROM A FAMOUS SCHOOLBOOK\
\
\
     A In ADAM'S Fall\
       We sinned all.\
\
     B Heaven to find,\
       The Bible Mind.\
\
     C Christ crucify'd\
       For sinners dy'd.\
\
     D The Deluge drown'd\
       The Earth around.\
\
     E ELIJAH hid\
       by Ravens fed.\
\
     F The judgment made\
       FELIX afraid.]\
\
\
\
Outside of New England the idea of compulsory education was not regarded\
with the same favor; but the whole land was nevertheless dotted with\
little schools kept by "dames, itinerant teachers, or local parsons."\
Whether we turn to the life of Franklin in the North or Washington in\
the South, we read of tiny schoolhouses, where boys, and sometimes\
girls, were taught to read and write. Where there were no schools,\
fathers and mothers of the better kind gave their children the rudiments\
of learning. Though illiteracy was widespread, there is evidence to show\
that the diffusion of knowledge among the masses was making steady\
progress all through the eighteenth century.\
\
=Religion and Higher Learning.=--Religious motives entered into the\
establishment of colleges as well as local schools. Harvard, founded in\
1636, and Yale, opened in 1718, were intended primarily to train\
"learned and godly ministers" for the Puritan churches of New England.\
To the far North, Dartmouth, chartered in 1769, was designed first as a\
mission to the Indians and then as a college for the sons of New England\
farmers preparing to preach, teach, or practice law. The College of New\
Jersey, organized in 1746 and removed to Princeton eleven years later,\
was sustained by the Presbyterians. Two colleges looked to the\
Established Church as their source of inspiration and support: William\
and Mary, founded in Virginia in 1693, and King's College, now Columbia\
University, chartered by King George II in 1754, on an appeal from the\
New York Anglicans, alarmed at the growth of religious dissent and the\
"republican tendencies" of the age. Two colleges revealed a drift away\
from sectarianism. Brown, established in Rhode Island in 1764, and the\
Philadelphia Academy, forerunner of the University of Pennsylvania,\
organized by Benjamin Franklin, reflected the spirit of toleration by\
giving representation on the board of trustees to several religious\
sects. It was Franklin's idea that his college should prepare young men\
to serve in public office as leaders of the people and ornaments to\
their country.\
\
=Self-education in America.=--Important as were these institutions of\
learning, higher education was by no means confined within their walls.\
Many well-to-do families sent their sons to Oxford or Cambridge in\
England. Private tutoring in the home was common. In still more families\
there were intelligent children who grew up in the great colonial school\
of adversity and who trained themselves until, in every contest of mind\
and wit, they could vie with the sons of Harvard or William and Mary or\
any other college. Such, for example, was Benjamin Franklin, whose\
charming autobiography, in addition to being an American classic, is a\
fine record of self-education. His formal training in the classroom was\
limited to a few years at a local school in Boston; but his\
self-education continued throughout his life. He early manifested a zeal\
for reading, and devoured, he tells us, his father's dry library on\
theology, Bunyan's works, Defoe's writings, Plutarch's _Lives_, Locke's\
_On the Human Understanding_, and innumerable volumes dealing with\
secular subjects. His literary style, perhaps the best of his time,\
Franklin acquired by the diligent and repeated analysis of the\
_Spectator_. In a life crowded with labors, he found time to read widely\
in natural science and to win single-handed recognition at the hands of\
European savants for his discoveries in electricity. By his own efforts\
he "attained an acquaintance" with Latin, Italian, French, and Spanish,\
thus unconsciously preparing himself for the day when he was to speak\
for all America at the court of the king of France.\
\
Lesser lights than Franklin, educated by the same process, were found\
all over colonial America. From this fruitful source of native ability,\
self-educated, the American cause drew great strength in the trials of\
the Revolution.\
\
\
THE COLONIAL PRESS\
\
=The Rise of the Newspaper.=--The evolution of American democracy into a\
government by public opinion, enlightened by the open discussion of\
political questions, was in no small measure aided by a free press. That\
too, like education, was a matter of slow growth. A printing press was\
brought to Massachusetts in 1639, but it was put in charge of an\
official censor and limited to the publication of religious works. Forty\
years elapsed before the first newspaper appeared, bearing the curious\
title, _Public Occurrences Both Foreign and Domestic_, and it had not\
been running very long before the government of Massachusetts suppressed\
it for discussing a political question.\
\
Publishing, indeed, seemed to be a precarious business; but in 1704\
there came a second venture in journalism, _The Boston News-Letter_,\
which proved to be a more lasting enterprise because it refrained from\
criticizing the authorities. Still the public interest languished. When\
Franklin's brother, James, began to issue his _New England Courant_\
about 1720, his friends sought to dissuade him, saying that one\
newspaper was enough for America. Nevertheless he continued it; and his\
confidence in the future was rewarded. In nearly every colony a gazette\
or chronicle appeared within the next thirty years or more. Benjamin\
Franklin was able to record in 1771 that America had twenty-five\
newspapers. Boston led with five. Philadelphia had three: two in English\
and one in German.\
\
=Censorship and Restraints on the Press.=--The idea of printing,\
unlicensed by the government and uncontrolled by the church, was,\
however, slow in taking form. The founders of the American colonies had\
never known what it was to have the free and open publication of books,\
pamphlets, broadsides, and newspapers. When the art of printing was\
first discovered, the control of publishing was vested in clerical\
authorities. After the establishment of the State Church in England in\
the reign of Elizabeth, censorship of the press became a part of royal\
prerogative. Printing was restricted to Oxford, Cambridge, and London;\
and no one could publish anything without previous approval of the\
official censor. When the Puritans were in power, the popular party,\
with a zeal which rivaled that of the crown, sought, in turn, to silence\
royalist and clerical writers by a vigorous censorship. After the\
restoration of the monarchy, control of the press was once more placed\
in royal hands, where it remained until 1695, when Parliament, by\
failing to renew the licensing act, did away entirely with the official\
\
censorship. By that time political parties were so powerful and so\
active and printing presses were so numerous that official review of all\
published matter became a sheer impossibility.\
\
In America, likewise, some troublesome questions arose in connection\
with freedom of the press. The Puritans of Massachusetts were no less\
anxious than King Charles or the Archbishop of London to shut out from\
the prying eyes of the people all literature "not mete for them to\
read"; and so they established a system of official licensing for\
presses, which lasted until 1755. In the other colonies where there was\
more diversity of opinion and publishers could set up in business with\
impunity, they were nevertheless constantly liable to arrest for\
printing anything displeasing to the colonial governments. In 1721 the\
editor of the _Mercury_ in Philadelphia was called before the\
proprietary council and ordered to apologize for a political article,\
and for a later offense of a similar character he was thrown into jail.\
A still more famous case was that of Peter Zenger, a New York publisher,\
who was arrested in 1735 for criticising the administration. Lawyers who\
ventured to defend the unlucky editor were deprived of their licenses to\
practice, and it became necessary to bring an attorney all the way from\
Philadelphia. By this time the tension of feeling was high, and the\
approbation of the public was forthcoming when the lawyer for the\
defense exclaimed to the jury that the very cause of liberty itself, not\
that of the poor printer, was on trial! The verdict for Zenger, when it\
finally came, was the signal for an outburst of popular rejoicing.\
Already the people of King George's province knew how precious a thing\
is the freedom of the press.\
\
Thanks to the schools, few and scattered as they were, and to the\
vigilance of parents, a very large portion, perhaps nearly one-half, of\
the colonists could read. Through the newspapers, pamphlets, and\
almanacs that streamed from the types, the people could follow the\
course of public events and grasp the significance of political\
arguments. An American opinion was in the process of making--an\
independent opinion nourished by the press and enriched by discussions\
around the fireside and at the taverns. When the day of resistance to\
British rule came, government by opinion was at hand. For every person\
who could hear the voice of Patrick Henry and Samuel Adams, there were a\
thousand who could see their appeals on the printed page. Men who had\
spelled out their letters while poring over Franklin's _Poor Richard's\
Almanac_ lived to read Thomas Paine's thrilling call to arms.\
\
\
THE EVOLUTION IN POLITICAL INSTITUTIONS\
\
Two very distinct lines of development appeared in colonial politics.\
The one, exalting royal rights and aristocratic privileges, was the\
drift toward provincial government through royal officers appointed in\
England. The other, leading toward democracy and self-government, was\
the growth in the power of the popular legislative assembly. Each\
movement gave impetus to the other, with increasing force during the\
passing years, until at last the final collision between the two ideals\
of government came in the war of independence.\
\
=The Royal Provinces.=--Of the thirteen English colonies eight were\
royal provinces in 1776, with governors appointed by the king. Virginia\
passed under the direct rule of the crown in 1624, when the charter of\
the London Company was annulled. The Massachusetts Bay corporation lost\
its charter in 1684, and the new instrument granted seven years later\
stripped the colonists of the right to choose their chief executive. In\
the early decades of the eighteenth century both the Carolinas were\
given the provincial instead of the proprietary form. New Hampshire,\
severed from Massachusetts in 1679, and Georgia, surrendered by the\
trustees in 1752, went into the hands of the crown. New York,\
transferred to the Duke of York on its capture from the Dutch in 1664,\
became a province when he took the title of James II in 1685. New\
Jersey, after remaining for nearly forty years under proprietors, was\
brought directly under the king in 1702. Maryland, Pennsylvania, and\
Delaware, although they retained their proprietary character until the\
Revolution, were in some respects like the royal colonies, for their\
governors were as independent of popular choice as were the appointees\
of King George. Only two colonies, Rhode Island and Connecticut,\
retained full self-government on the eve of the Revolution. They alone\
had governors and legislatures entirely of their own choosing.\
\
The chief officer of the royal province was the governor, who enjoyed\
high and important powers which he naturally sought to augment at every\
turn. He enforced the laws and, usually with the consent of a council,\
appointed the civil and military officers. He granted pardons and\
reprieves; he was head of the highest court; he was commander-in-chief\
of the militia; he levied troops for defense and enforced martial law in\
time of invasion, war, and rebellion. In all the provinces, except\
Massachusetts, he named the councilors who composed the upper house of\
the legislature and was likely to choose those who favored his claims.\
He summoned, adjourned, and dissolved the popular assembly, or the lower\
house; he laid before it the projects of law desired by the crown; and\
he vetoed measures which he thought objectionable. Here were in America\
all the elements of royal prerogative against which Hampden had\
protested and Cromwell had battled in England.\
\
[Illustration: THE ROYAL GOVERNOR'S PALACE AT NEW BERNE]\
\
The colonial governors were generally surrounded by a body of\
office-seekers and hunters for land grants. Some of them were noblemen\
of broken estates who had come to America to improve their fortunes. The\
pretensions of this circle grated on colonial nerves, and privileges\
granted to them, often at the expense of colonists, did much to deepen\
popular antipathy to the British government. Favors extended to\
adherents of the Established Church displeased Dissenters. The\
reappearance of this formidable union of church and state, from which\
they had fled, stirred anew the ancient wrath against that combination.\
\
=The Colonial Assembly.=--Coincident with the drift toward\
administration through royal governors was the second and opposite\
tendency, namely, a steady growth in the practice of self-government.\
The voters of England had long been accustomed to share in taxation and\
law-making through representatives in Parliament, and the idea was early\
introduced in America. Virginia was only twelve years old (1619) when\
its first representative assembly appeared. As the towns of\
Massachusetts multiplied and it became impossible for all the members of\
the corporation to meet at one place, the representative idea was\
adopted, in 1633. The river towns of Connecticut formed a representative\
system under their "Fundamental Orders" of 1639, and the entire colony\
was given a royal charter in 1662. Generosity, as well as practical\
considerations, induced such proprietors as Lord Baltimore and William\
Penn to invite their colonists to share in the government as soon as any\
considerable settlements were made. Thus by one process or another every\
one of the colonies secured a popular assembly.\
\
It is true that in the provision for popular elections, the suffrage was\
finally restricted to property owners or taxpayers, with a leaning\
toward the freehold qualification. In Virginia, the rural voter had to\
be a freeholder owning at least fifty acres of land, if there was no\
house on it, or twenty-five acres with a house twenty-five feet square.\
In Massachusetts, the voter for member of the assembly under the charter\
of 1691 had to be a freeholder of an estate worth forty shillings a year\
at least or of other property to the value of forty pounds sterling. In\
Pennsylvania, the suffrage was granted to freeholders owning fifty acres\
or more of land well seated, twelve acres cleared, and to other persons\
worth at least fifty pounds in lawful money.\
\
Restrictions like these undoubtedly excluded from the suffrage a very\
considerable number of men, particularly the mechanics and artisans of\
the towns, who were by no means content with their position.\
Nevertheless, it was relatively easy for any man to acquire a small\
freehold, so cheap and abundant was land; and in fact a large proportion\
of the colonists were land owners. Thus the assemblies, in spite of the\
limited suffrage, acquired a democratic tone.\
\
The popular character of the assemblies increased as they became engaged\
in battles with the royal and proprietary governors. When called upon by\
the executive to make provision for the support of the administration,\
the legislature took advantage of the opportunity to make terms in the\
interest of the taxpayers. It made annual, not permanent, grants of\
money to pay official salaries and then insisted upon electing a\
treasurer to dole it out. Thus the colonists learned some of the\
mysteries of public finance, as well as the management of rapacious\
officials. The legislature also used its power over money grants to\
force the governor to sign bills which he would otherwise have vetoed.\
\
=Contests between Legislatures and Governors.=--As may be imagined, many\
and bitter were the contests between the royal and proprietary governors\
and the colonial assemblies. Franklin relates an amusing story of how\
the Pennsylvania assembly held in one hand a bill for the executive to\
sign and, in the other hand, the money to pay his salary. Then, with sly\
humor, Franklin adds: "Do not, my courteous reader, take pet at our\
proprietary constitution for these our bargain and sale proceedings in\
legislation. It is a happy country where justice and what was your own\
before can be had for ready money. It is another addition to the value\
of money and of course another spur to industry. Every land is not so\
blessed."\
\
It must not be thought, however, that every governor got off as easily\
as Franklin's tale implies. On the contrary, the legislatures, like\
Caesar, fed upon meat that made them great and steadily encroached upon\
executive prerogatives as they tried out and found their strength. If\
we may believe contemporary laments, the power of the crown in America\
was diminishing when it was struck down altogether. In New York, the\
friends of the governor complained in 1747 that "the inhabitants of\
plantations are generally educated in republican principles; upon\
republican principles all is conducted. Little more than a shadow of\
royal authority remains in the Northern colonies." "Here," echoed the\
governor of South Carolina, the following year, "levelling principles\
prevail; the frame of the civil government is unhinged; a governor, if\
he would be idolized, must betray his trust; the people have got their\
whole administration in their hands; the election of the members of the\
assembly is by ballot; not civil posts only, but all ecclesiastical\
preferments, are in the disposal or election of the people."\
\
Though baffled by the "levelling principles" of the colonial assemblies,\
the governors did not give up the case as hopeless. Instead they evolved\
a system of policy and action which they thought could bring the\
obstinate provincials to terms. That system, traceable in their letters\
to the government in London, consisted of three parts: (1) the royal\
officers in the colonies were to be made independent of the legislatures\
by taxes imposed by acts of Parliament; (2) a British standing army was\
to be maintained in America; (3) the remaining colonial charters were to\
be revoked and government by direct royal authority was to be enlarged.\
\
Such a system seemed plausible enough to King George III and to many\
ministers of the crown in London. With governors, courts, and an army\
independent of the colonists, they imagined it would be easy to carry\
out both royal orders and acts of Parliament. This reasoning seemed both\
practical and logical. Nor was it founded on theory, for it came fresh\
from the governors themselves. It was wanting in one respect only. It\
failed to take account of the fact that the American people were growing\
strong in the practice of self-government and could dispense with the\
tutelage of the British ministry, no matter how excellent it might be or\
how benevolent its intentions.\
\
\
=References=\
\
A.M. Earle, _Home Life in Colonial Days_.\
\
A.L. Cross, _The Anglican Episcopate and the American Colonies_ (Harvard\
Studies).\
\
E.G. Dexter, _History of Education in the United States_.\
\
C.A. Duniway, _Freedom of the Press in Massachusetts_.\
\
Benjamin Franklin, _Autobiography_.\
\
E.B. Greene, _The Provincial Governor_ (Harvard Studies).\
\
A.E. McKinley, _The Suffrage Franchise in the Thirteen English Colonies_\
(Pennsylvania University Studies).\
\
M.C. Tyler, _History of American Literature during the Colonial Times_\
(2 vols.).\
\
\
=Questions=\
\
1. Why is leisure necessary for the production of art and literature?\
How may leisure be secured?\
\
2. Explain the position of the church in colonial life.\
\
3. Contrast the political roles of Puritanism and the Established\
Church.\
\
4. How did diversity of opinion work for toleration?\
\
5. Show the connection between religion and learning in colonial times.\
\
6. Why is a "free press" such an important thing to American democracy?\
\
7. Relate some of the troubles of early American publishers.\
\
8. Give the undemocratic features of provincial government.\
\
9. How did the colonial assemblies help to create an independent\
American spirit, in spite of a restricted suffrage?\
\
10. Explain the nature of the contests between the governors and the\
legislatures.\
\
\
=Research Topics=\
\
=Religious and Intellectual Life.=--Lodge, _Short History of the English\
Colonies_: (1) in New England, pp. 418-438, 465-475; (2) in Virginia,\
pp. 54-61, 87-89; (3) in Pennsylvania, pp. 232-237, 253-257; (4) in New\
York, pp. 316-321. Interesting source materials in Hart, _American\
History Told by Contemporaries_, Vol. II, pp. 255-275, 276-290.\
\
=The Government of a Royal Province, Virginia.=--Lodge, pp. 43-50.\
Special Reference: E.B. Greene, _The Provincial Governor_ (Harvard\
Studies).\
\
=The Government of a Proprietary Colony, Pennsylvania.=--Lodge, pp.\
230-232.\
\
=Government in New England.=--Lodge, pp. 412-417.\
\
=The Colonial Press.=--Special Reference: G.H. Payne, _History of\
Journalism in the United States_ (1920).\
\
=Colonial Life in General.=--John Fiske, _Old Virginia and Her\
Neighbors_, Vol. II, pp. 174-269; Elson, _History of the United States_,\
pp. 197-210.\
\
=Colonial Government in General.=--Elson, pp. 210-216.\
\
\
\
\
CHAPTER IV\
\
THE DEVELOPMENT OF COLONIAL NATIONALISM\
\
\
It is one of the well-known facts of history that a people loosely\
united by domestic ties of a political and economic nature, even a\
people torn by domestic strife, may be welded into a solid and compact\
body by an attack from a foreign power. The imperative call to common\
defense, the habit of sharing common burdens, the fusing force of common\
service--these things, induced by the necessity of resisting outside\
interference, act as an amalgam drawing together all elements, except,\
perhaps, the most discordant. The presence of the enemy allays the most\
virulent of quarrels, temporarily at least. "Politics," runs an old\
saying, "stops at the water's edge."\
\
This ancient political principle, so well understood in diplomatic\
circles, applied nearly as well to the original thirteen American\
colonies as to the countries of Europe. The necessity for common\
defense, if not equally great, was certainly always pressing. Though it\
has long been the practice to speak of the early settlements as founded\
in "a wilderness," this was not actually the case. From the earliest\
days of Jamestown on through the years, the American people were\
confronted by dangers from without. All about their tiny settlements\
were Indians, growing more and more hostile as the frontier advanced and\
as sharp conflicts over land aroused angry passions. To the south and\
west was the power of Spain, humiliated, it is true, by the disaster to\
the Armada, but still presenting an imposing front to the British\
empire. To the north and west were the French, ambitious, energetic,\
imperial in temper, and prepared to contest on land and water the\
advance of British dominion in America.\
\
\
RELATIONS WITH THE INDIANS AND THE FRENCH\
\
=Indian Affairs.=--It is difficult to make general statements about the\
relations of the colonists to the Indians. The problem was presented in\
different shape in different sections of America. It was not handled\
according to any coherent or uniform plan by the British government,\
which alone could speak for all the provinces at the same time. Neither\
did the proprietors and the governors who succeeded one another, in an\
irregular train, have the consistent policy or the matured experience\
necessary for dealing wisely with Indian matters. As the difficulties\
arose mainly on the frontiers, where the restless and pushing pioneers\
were making their way with gun and ax, nearly everything that happened\
was the result of chance rather than of calculation. A personal quarrel\
between traders and an Indian, a jug of whisky, a keg of gunpowder, the\
exchange of guns for furs, personal treachery, or a flash of bad temper\
often set in motion destructive forces of the most terrible character.\
\
On one side of the ledger may be set innumerable generous records--of\
Squanto and Samoset teaching the Pilgrims the ways of the wilds; of\
Roger Williams buying his lands from the friendly natives; or of William\
Penn treating with them on his arrival in America. On the other side of\
the ledger must be recorded many a cruel and bloody conflict as the\
frontier rolled westward with deadly precision. The Pequots on the\
Connecticut border, sensing their doom, fell upon the tiny settlements\
with awful fury in 1637 only to meet with equally terrible punishment. A\
generation later, King Philip, son of Massasoit, the friend of the\
Pilgrims, called his tribesmen to a war of extermination which brought\
the strength of all New England to the field and ended in his own\
destruction. In New York, the relations with the Indians, especially\
with the Algonquins and the Mohawks, were marked by periodic and\
desperate wars. Virginia and her Southern neighbors suffered as did New\
England. In 1622 Opecacano, a brother of Powhatan, the friend of the\
Jamestown settlers, launched a general massacre; and in 1644 he\
attempted a war of extermination. In 1675 the whole frontier was ablaze.\
Nathaniel Bacon vainly attempted to stir the colonial governor to put up\
an adequate defense and, failing in that plea, himself headed a revolt\
and a successful expedition against the Indians. As the Virginia\
outposts advanced into the Kentucky country, the strife with the natives\
was transferred to that "dark and bloody ground"; while to the\
southeast, a desperate struggle with the Tuscaroras called forth the\
combined forces of the two Carolinas and Virginia.\
\
[Illustration: _From an old print._\
\
VIRGINIANS DEFENDING THEMSELVES AGAINST THE INDIANS]\
\
From such horrors New Jersey and Delaware were saved on account of their\
geographical location. Pennsylvania, consistently following a policy of\
conciliation, was likewise spared until her western vanguard came into\
full conflict with the allied French and Indians. Georgia, by clever\
negotiations and treaties of alliance, managed to keep on fair terms\
with her belligerent Cherokees and Creeks. But neither diplomacy nor\
generosity could stay the inevitable conflict as the frontier advanced,\
especially after the French soldiers enlisted the Indians in their\
imperial enterprises. It was then that desultory fighting became general\
warfare.\
\
[Illustration: ENGLISH, FRENCH, AND SPANISH POSSESSIONS IN AMERICA,\
1750]\
\
=Early Relations with the French.=--During the first decades of French\
exploration and settlement in the St. Lawrence country, the English\
colonies, engrossed with their own problems, gave little or no thought\
to their distant neighbors. Quebec, founded in 1608, and Montreal, in\
1642, were too far away, too small in population, and too slight in\
strength to be much of a menace to Boston, Hartford, or New York. It was\
the statesmen in France and England, rather than the colonists in\
America, who first grasped the significance of the slowly converging\
empires in North America. It was the ambition of Louis XIV of France,\
rather than the labors of Jesuit missionaries and French rangers, that\
sounded the first note of colonial alarm.\
\
Evidence of this lies in the fact that three conflicts between the\
English and the French occurred before their advancing frontiers met on\
the Pennsylvania border. King William's War (1689-1697), Queen Anne's\
War (1701-1713), and King George's War (1744-1748) owed their origins\
and their endings mainly to the intrigues and rivalries of European\
powers, although they all involved the American colonies in struggles\
with the French and their savage allies.\
\
=The Clash in the Ohio Valley.=--The second of these wars had hardly\
closed, however, before the English colonists themselves began to be\
seriously alarmed about the rapidly expanding French dominion in the\
West. Marquette and Joliet, who opened the Lake region, and La Salle,\
who in 1682 had gone down the Mississippi to the Gulf, had been followed\
by the builders of forts. In 1718, the French founded New Orleans, thus\
taking possession of the gateway to the Mississippi as well as the St.\
Lawrence. A few years later they built Fort Niagara; in 1731 they\
occupied Crown Point; in 1749 they formally announced their dominion\
over all the territory drained by the Ohio River. Having asserted this\
lofty claim, they set out to make it good by constructing in the years\
1752-1754 Fort Le Boeuf near Lake Erie, Fort Venango on the upper\
waters of the Allegheny, and Fort Duquesne at the junction of the\
streams forming the Ohio. Though they were warned by George Washington,\
in the name of the governor of Virginia, to keep out of territory "so\
notoriously known to be property of the crown of Great Britain," the\
French showed no signs of relinquishing their pretensions.\
\
[Illustration: _From an old print_\
\
BRADDOCK'S RETREAT]\
\
=The Final Phase--the French and Indian War.=--Thus it happened that the\
shot which opened the Seven Years' War, known in America as the French\
and Indian War, was fired in the wilds of Pennsylvania. There began the\
conflict that spread to Europe and even Asia and finally involved\
England and Prussia, on the one side, and France, Austria, Spain, and\
minor powers on the other. On American soil, the defeat of Braddock in\
1755 and Wolfe's exploit in capturing Quebec four years later were the\
dramatic features. On the continent of Europe, England subsidized\
Prussian arms to hold France at bay. In India, on the banks of the\
Ganges, as on the banks of the St. Lawrence, British arms were\
triumphant. Well could the historian write: "Conquests equaling in\
rapidity and far surpassing in magnitude those of Cortes and Pizarro had\
been achieved in the East." Well could the merchants of London declare\
that under the administration of William Pitt, the imperial genius of\
this world-wide conflict, commerce had been "united with and made to\
flourish by war."\
\
From the point of view of the British empire, the results of the war\
were momentous. By the peace of 1763, Canada and the territory east of\
the Mississippi, except New Orleans, passed under the British flag. The\
remainder of the Louisiana territory was transferred to Spain and French\
imperial ambitions on the American continent were laid to rest. In\
exchange for Havana, which the British had seized during the war, Spain\
ceded to King George the colony of Florida. Not without warrant did\
Macaulay write in after years that Pitt "was the first Englishman of his\
time; and he had made England the first country in the world."\
\
\
THE EFFECTS OF WARFARE ON THE COLONIES\
\
The various wars with the French and the Indians, trivial in detail as\
they seem to-day, had a profound influence on colonial life and on the\
destiny of America. Circumstances beyond the control of popular\
assemblies, jealous of their individual powers, compelled cooperation\
among them, grudging and stingy no doubt, but still cooperation. The\
American people, more eager to be busy in their fields or at their\
trades, were simply forced to raise and support armies, to learn the\
arts of warfare, and to practice, if in a small theater, the science of\
statecraft. These forces, all cumulative, drove the colonists, so\
tenaciously provincial in their habits, in the direction of nationalism.\
\
=The New England Confederation.=--It was in their efforts to deal with\
the problems presented by the Indian and French menace that the\
Americans took the first steps toward union. Though there were many\
common ties among the settlers of New England, it required a deadly\
fear of the Indians to produce in 1643 the New England Confederation,\
composed of Massachusetts, Plymouth, Connecticut, and New Haven. The\
colonies so united were bound together in "a firm and perpetual league\
of friendship and amity for offense and defense, mutual service and\
succor, upon all just occasions." They made provision for distributing\
the burdens of wars among the members and provided for a congress of\
commissioners from each colony to determine upon common policies. For\
some twenty years the Confederation was active and it continued to hold\
meetings until after the extinction of the Indian peril on the immediate\
border.\
\
Virginia, no less than Massachusetts, was aware of the importance of\
intercolonial cooperation. In the middle of the seventeenth century, the\
Old Dominion began treaties of commerce and amity with New York and the\
colonies of New England. In 1684 delegates from Virginia met at Albany\
with the agents of New York and Massachusetts to discuss problems of\
mutual defense. A few years later the Old Dominion cooperated loyally\
with the Carolinas in defending their borders against Indian forays.\
\
=The Albany Plan of Union.=--An attempt at a general colonial union was\
made in 1754. On the suggestion of the Lords of Trade in England, a\
conference was held at Albany to consider Indian relations, to devise\
measures of defense against the French, and to enter into "articles of\
union and confederation for the general defense of his Majesty's\
subjects and interests in North America as well in time of peace as of\
war." New Hampshire, Massachusetts, Connecticut, Rhode Island, New York,\
Pennsylvania, and Maryland were represented. After a long discussion, a\
plan of union, drafted mainly, it seems, by Benjamin Franklin, was\
adopted and sent to the colonies and the crown for approval. The\
colonies, jealous of their individual rights, refused to accept the\
scheme and the king disapproved it for the reason, Franklin said, that\
it had "too much weight in the democratic part of the constitution."\
Though the Albany union failed, the document is still worthy of study\
because it forecast many of the perplexing problems that were not solved\
until thirty-three years afterward, when another convention of which\
also Franklin was a member drafted the Constitution of the United\
States.\
\
[Illustration: BENJAMIN FRANKLIN]\
\
=The Military Education of the Colonists.=--The same wars that showed\
the provincials the meaning of union likewise instructed them in the art\
of defending their institutions. Particularly was this true of the last\
French and Indian conflict, which stretched all the way from Maine to\
the Carolinas and made heavy calls upon them all for troops. The answer,\
it is admitted, was far from satisfactory to the British government and\
the conduct of the militiamen was far from professional; but thousands\
of Americans got a taste, a strong taste, of actual fighting in the\
field. Men like George Washington and Daniel Morgan learned lessons that\
were not forgotten in after years. They saw what American militiamen\
could do under favorable circumstances and they watched British regulars\
operating on American soil. "This whole transaction," shrewdly remarked\
Franklin of Braddock's campaign, "gave us Americans the first suspicion\
that our exalted ideas of the prowess of British regular troops had not\
been well founded." It was no mere accident that the Virginia colonel\
who drew his sword under the elm at Cambridge and took command of the\
army of the Revolution was the brave officer who had "spurned the\
whistle of bullets" at the memorable battle in western Pennsylvania.\
\
=Financial Burdens and Commercial Disorder.=--While the provincials were\
learning lessons in warfare they were also paying the bills. All the\
conflicts were costly in treasure as in blood. King Philip's war left\
New England weak and almost bankrupt. The French and Indian struggle was\
especially expensive. The twenty-five thousand men put in the field by\
the colonies were sustained only by huge outlays of money. Paper\
currency streamed from the press and debts were accumulated. Commerce\
was driven from its usual channels and prices were enhanced. When the\
end came, both England and America were staggering under heavy\
liabilities, and to make matters worse there was a fall of prices\
accompanied by a commercial depression which extended over a period of\
ten years. It was in the midst of this crisis that measures of taxation\
had to be devised to pay the cost of the war, precipitating the quarrel\
which led to American independence.\
\
=The Expulsion of French Power from North America.=--The effects of the\
defeat administered to France, as time proved, were difficult to\
estimate. Some British statesmen regarded it as a happy circumstance\
that the colonists, already restive under their administration, had no\
foreign power at hand to aid them in case they struck for independence.\
American leaders, on the other hand, now that the soldiers of King Louis\
were driven from the continent, thought that they had no other country\
to fear if they cast off British sovereignty. At all events, France,\
though defeated, was not out of the sphere of American influence; for,\
as events proved, it was the fortunate French alliance negotiated by\
Franklin that assured the triumph of American arms in the War of the\
Revolution.\
\
\
COLONIAL RELATIONS WITH THE BRITISH GOVERNMENT\
\
It was neither the Indian wars nor the French wars that finally brought\
forth American nationality. That was the product of the long strife\
with the mother country which culminated in union for the war of\
independence. The forces that created this nation did not operate in the\
colonies alone. The character of the English sovereigns, the course of\
events in English domestic politics, and English measures of control\
over the colonies--executive, legislative, and judicial--must all be\
taken into account.\
\
=The Last of the Stuarts.=--The struggles between Charles I (1625-49)\
and the parliamentary party and the turmoil of the Puritan regime\
(1649-60) so engrossed the attention of Englishmen at home that they had\
little time to think of colonial policies or to interfere with colonial\
affairs. The restoration of the monarchy in 1660, accompanied by\
internal peace and the increasing power of the mercantile classes in the\
House of Commons, changed all that. In the reign of Charles II\
(1660-85), himself an easy-going person, the policy of regulating trade\
by act of Parliament was developed into a closely knit system and\
powerful agencies to supervise the colonies were created. At the same\
time a system of stricter control over the dominions was ushered in by\
the annulment of the old charter of Massachusetts which conferred so\
much self-government on the Puritans.\
\
Charles' successor, James II, a man of sterner stuff and jealous of his\
authority in the colonies as well as at home, continued the policy thus\
inaugurated and enlarged upon it. If he could have kept his throne, he\
would have bent the Americans under a harsh rule or brought on in his\
dominions a revolution like that which he precipitated at home in 1688.\
He determined to unite the Northern colonies and introduce a more\
efficient administration based on the pattern of the royal provinces. He\
made a martinet, Sir Edmund Andros, governor of all New England, New\
York, and New Jersey. The charter of Massachusetts, annulled in the last\
days of his brother's reign, he continued to ignore, and that of\
Connecticut would have been seized if it had not been spirited away and\
hidden, according to tradition, in a hollow oak.\
\
For several months, Andros gave the Northern colonies a taste of\
ill-tempered despotism. He wrung quit rents from land owners not\
accustomed to feudal dues; he abrogated titles to land where, in his\
opinion, they were unlawful; he forced the Episcopal service upon the\
Old South Church in Boston; and he denied the writ of _habeas corpus_ to\
a preacher who denounced taxation without representation. In the middle\
of his arbitrary course, however, his hand was stayed. The news came\
that King James had been dethroned by his angry subjects, and the people\
of Boston, kindling a fire on Beacon Hill, summoned the countryside to\
dispose of Andros. The response was prompt and hearty. The hated\
governor was arrested, imprisoned, and sent back across the sea under\
guard.\
\
The overthrow of James, followed by the accession of William and Mary\
and by assured parliamentary supremacy, had an immediate effect in the\
colonies. The new order was greeted with thanksgiving. Massachusetts was\
given another charter which, though not so liberal as the first,\
restored the spirit if not the entire letter of self-government. In the\
other colonies where Andros had been operating, the old course of\
affairs was resumed.\
\
=The Indifference of the First Two Georges.=--On the death in 1714 of\
Queen Anne, the successor of King William, the throne passed to a\
Hanoverian prince who, though grateful for English honors and revenues,\
was more interested in Hanover than in England. George I and George II,\
whose combined reigns extended from 1714 to 1760, never even learned to\
speak the English language, at least without an accent. The necessity of\
taking thought about colonial affairs bored both of them so that the\
stoutest defender of popular privileges in Boston or Charleston had no\
ground to complain of the exercise of personal prerogatives by the king.\
Moreover, during a large part of this period, the direction of affairs\
was in the hands of an astute leader, Sir Robert Walpole, who betrayed\
his somewhat cynical view of politics by adopting as his motto: "Let\
sleeping dogs lie." He revealed his appreciation of popular sentiment\
by exclaiming: "I will not be the minister to enforce taxes at the\
expense of blood." Such kings and such ministers were not likely to\
arouse the slumbering resistance of the thirteen colonies across the\
sea.\
\
=Control of the Crown over the Colonies.=--While no English ruler from\
James II to George III ventured to interfere with colonial matters\
personally, constant control over the colonies was exercised by royal\
officers acting under the authority of the crown. Systematic supervision\
began in 1660, when there was created by royal order a committee of the\
king's council to meet on Mondays and Thursdays of each week to consider\
petitions, memorials, and addresses respecting the plantations. In 1696\
a regular board was established, known as the "Lords of Trade and\
Plantations," which continued, until the American Revolution, to\
scrutinize closely colonial business. The chief duties of the board were\
to examine acts of colonial legislatures, to recommend measures to those\
assemblies for adoption, and to hear memorials and petitions from the\
colonies relative to their affairs.\
\
The methods employed by this board were varied. All laws passed by\
American legislatures came before it for review as a matter of routine.\
If it found an act unsatisfactory, it recommended to the king the\
exercise of his veto power, known as the royal disallowance. Any person\
who believed his personal or property rights injured by a colonial law\
could be heard by the board in person or by attorney; in such cases it\
was the practice to hear at the same time the agent of the colony so\
involved. The royal veto power over colonial legislation was not,\
therefore, a formal affair, but was constantly employed on the\
suggestion of a highly efficient agency of the crown. All this was in\
addition to the powers exercised by the governors in the royal\
provinces.\
\
=Judicial Control.=--Supplementing this administrative control over the\
colonies was a constant supervision by the English courts of law. The\
king, by virtue of his inherent authority, claimed and exercised high\
appellate powers over all judicial tribunals in the empire. The right\
of appeal from local courts, expressly set forth in some charters, was,\
on the eve of the Revolution, maintained in every colony. Any subject in\
England or America, who, in the regular legal course, was aggrieved by\
any act of a colonial legislature or any decision of a colonial court,\
had the right, subject to certain regulations, to carry his case to the\
king in council, forcing his opponent to follow him across the sea. In\
the exercise of appellate power, the king in council acting as a court\
could, and frequently did, declare acts of colonial legislatures duly\
enacted and approved, null and void, on the ground that they were\
contrary to English law.\
\
=Imperial Control in Operation.=--Day after day, week after week, year\
after year, the machinery for political and judicial control over\
colonial affairs was in operation. At one time the British governors in\
the colonies were ordered not to approve any colonial law imposing a\
duty on European goods imported in English vessels. Again, when North\
Carolina laid a tax on peddlers, the council objected to it as\
"restrictive upon the trade and dispersion of English manufactures\
throughout the continent." At other times, Indian trade was regulated in\
the interests of the whole empire or grants of lands by a colonial\
legislature were set aside. Virginia was forbidden to close her ports to\
North Carolina lest there should be retaliation.\
\
In short, foreign and intercolonial trade were subjected to a control\
higher than that of the colony, foreshadowing a day when the\
Constitution of the United States was to commit to Congress the power to\
regulate interstate and foreign commerce and commerce with the Indians.\
A superior judicial power, towering above that of the colonies, as the\
Supreme Court at Washington now towers above the states, kept the\
colonial legislatures within the metes and bounds of established law. In\
the thousands of appeals, memorials, petitions, and complaints, and the\
rulings and decisions upon them, were written the real history of\
British imperial control over the American colonies.\
\
So great was the business before the Lords of Trade that the colonies\
had to keep skilled agents in London to protect their interests. As\
common grievances against the operation of this machinery of control\
arose, there appeared in each colony a considerable body of men, with\
the merchants in the lead, who chafed at the restraints imposed on their\
enterprise. Only a powerful blow was needed to weld these bodies into a\
common mass nourishing the spirit of colonial nationalism. When to the\
repeated minor irritations were added general and sweeping measures of\
Parliament applying to every colony, the rebound came in the Revolution.\
\
=Parliamentary Control over Colonial Affairs.=--As soon as Parliament\
gained in power at the expense of the king, it reached out to bring the\
American colonies under its sway as well. Between the execution of\
Charles I and the accession of George III, there was enacted an immense\
body of legislation regulating the shipping, trade, and manufactures of\
America. All of it, based on the "mercantile" theory then prevalent in\
all countries of Europe, was designed to control the overseas\
plantations in such a way as to foster the commercial and business\
interests of the mother country, where merchants and men of finance had\
got the upper hand. According to this theory, the colonies of the\
British empire should be confined to agriculture and the production of\
raw materials, and forced to buy their manufactured goods of England.\
\
_The Navigation Acts._--In the first rank among these measures of\
British colonial policy must be placed the navigation laws framed for\
the purpose of building up the British merchant marine and navy--arms so\
essential in defending the colonies against the Spanish, Dutch, and\
French. The beginning of this type of legislation was made in 1651 and\
it was worked out into a system early in the reign of Charles II\
(1660-85).\
\
The Navigation Acts, in effect, gave a monopoly of colonial commerce to\
British ships. No trade could be carried on between Great Britain and\
her dominions save in vessels built and manned by British subjects. No\
European goods could be brought to America save in the ships of the\
country that produced them or in English ships. These laws, which were\
almost fatal to Dutch shipping in America, fell with severity upon the\
colonists, compelling them to pay higher freight rates. The adverse\
effect, however, was short-lived, for the measures stimulated\
shipbuilding in the colonies, where the abundance of raw materials gave\
the master builders of America an advantage over those of the mother\
country. Thus the colonists in the end profited from the restrictive\
policy written into the Navigation Acts.\
\
_The Acts against Manufactures._--The second group of laws was\
deliberately aimed to prevent colonial industries from competing too\
sharply with those of England. Among the earliest of these measures may\
be counted the Woolen Act of 1699, forbidding the exportation of woolen\
goods from the colonies and even the woolen trade between towns and\
colonies. When Parliament learned, as the result of an inquiry, that New\
England and New York were making thousands of hats a year and sending\
large numbers annually to the Southern colonies and to Ireland, Spain,\
and Portugal, it enacted in 1732 a law declaring that "no hats or felts,\
dyed or undyed, finished or unfinished" should be "put upon any vessel\
or laden upon any horse or cart with intent to export to any place\
whatever." The effect of this measure upon the hat industry was almost\
ruinous. A few years later a similar blow was given to the iron\
industry. By an act of 1750, pig and bar iron from the colonies were\
given free entry to England to encourage the production of the raw\
material; but at the same time the law provided that "no mill or other\
engine for slitting or rolling of iron, no plating forge to work with a\
tilt hammer, and no furnace for making steel" should be built in the\
colonies. As for those already built, they were declared public\
nuisances and ordered closed. Thus three important economic interests of\
the colonists, the woolen, hat, and iron industries, were laid under the\
ban.\
\
_The Trade Laws._--The third group of restrictive measures passed by the\
British Parliament related to the sale of colonial produce. An act of\
1663 required the colonies to export certain articles to Great Britain\
or to her dominions alone; while sugar, tobacco, and ginger consigned to\
the continent of Europe had to pass through a British port paying custom\
duties and through a British merchant's hands paying the usual\
commission. At first tobacco was the only one of the "enumerated\
articles" which seriously concerned the American colonies, the rest\
coming mainly from the British West Indies. In the course of time,\
however, other commodities were added to the list of enumerated\
articles, until by 1764 it embraced rice, naval stores, copper, furs,\
hides, iron, lumber, and pearl ashes. This was not all. The colonies\
were compelled to bring their European purchases back through English\
ports, paying duties to the government and commissions to merchants\
again.\
\
_The Molasses Act._--Not content with laws enacted in the interest of\
English merchants and manufacturers, Parliament sought to protect the\
British West Indies against competition from their French and Dutch\
neighbors. New England merchants had long carried on a lucrative trade\
with the French islands in the West Indies and Dutch Guiana, where sugar\
and molasses could be obtained in large quantities at low prices. Acting\
on the protests of English planters in the Barbadoes and Jamaica,\
Parliament, in 1733, passed the famous Molasses Act imposing duties on\
sugar and molasses imported into the colonies from foreign\
countries--rates which would have destroyed the American trade with the\
French and Dutch if the law had been enforced. The duties, however, were\
not collected. The molasses and sugar trade with the foreigners went on\
merrily, smuggling taking the place of lawful traffic.\
\
=Effect of the Laws in America.=--As compared with the strict monopoly\
of her colonial trade which Spain consistently sought to maintain, the\
policy of England was both moderate and liberal. Furthermore, the\
restrictive laws were supplemented by many measures intended to be\
favorable to colonial prosperity. The Navigation Acts, for example,\
redounded to the advantage of American shipbuilders and the producers\
of hemp, tar, lumber, and ship stores in general. Favors in British\
ports were granted to colonial producers as against foreign competitors\
and in some instances bounties were paid by England to encourage\
colonial enterprise. Taken all in all, there is much justification in\
the argument advanced by some modern scholars to the effect that the\
colonists gained more than they lost by British trade and industrial\
legislation. Certainly after the establishment of independence, when\
free from these old restrictions, the Americans found themselves\
handicapped by being treated as foreigners rather than favored traders\
and the recipients of bounties in English markets.\
\
Be that as it may, it appears that the colonists felt little irritation\
against the mother country on account of the trade and navigation laws\
enacted previous to the close of the French and Indian war. Relatively\
few were engaged in the hat and iron industries as compared with those\
in farming and planting, so that England's policy of restricting America\
to agriculture did not conflict with the interests of the majority of\
the inhabitants. The woolen industry was largely in the hands of women\
and carried on in connection with their domestic duties, so that it was\
not the sole support of any considerable number of people.\
\
As a matter of fact, moreover, the restrictive laws, especially those\
relating to trade, were not rigidly enforced. Cargoes of tobacco were\
boldly sent to continental ports without even so much as a bow to the\
English government, to which duties should have been paid. Sugar and\
molasses from the French and Dutch colonies were shipped into New\
England in spite of the law. Royal officers sometimes protested against\
smuggling and sometimes connived at it; but at no time did they succeed\
in stopping it. Taken all in all, very little was heard of "the galling\
restraints of trade" until after the French war, when the British\
government suddenly entered upon a new course.\
\
\
SUMMARY OF THE COLONIAL PERIOD\
\
In the period between the landing of the English at Jamestown, Virginia,\
in 1607, and the close of the French and Indian war in 1763--a period of\
a century and a half--a new nation was being prepared on this continent\
to take its place among the powers of the earth. It was an epoch of\
migration. Western Europe contributed emigrants of many races and\
nationalities. The English led the way. Next to them in numerical\
importance were the Scotch-Irish and the Germans. Into the melting pot\
were also cast Dutch, Swedes, French, Jews, Welsh, and Irish. Thousands\
of negroes were brought from Africa to till Southern fields or labor as\
domestic servants in the North.\
\
Why did they come? The reasons are various. Some of them, the Pilgrims\
and Puritans of New England, the French Huguenots, Scotch-Irish and\
Irish, and the Catholics of Maryland, fled from intolerant governments\
that denied them the right to worship God according to the dictates of\
their consciences. Thousands came to escape the bondage of poverty in\
the Old World and to find free homes in America. Thousands, like the\
negroes from Africa, were dragged here against their will. The lure of\
adventure appealed to the restless and the lure of profits to the\
enterprising merchants.\
\
How did they come? In some cases religious brotherhoods banded together\
and borrowed or furnished the funds necessary to pay the way. In other\
cases great trading companies were organized to found colonies. Again it\
was the wealthy proprietor, like Lord Baltimore or William Penn, who\
undertook to plant settlements. Many immigrants were able to pay their\
own way across the sea. Others bound themselves out for a term of years\
in exchange for the cost of the passage. Negroes were brought on account\
of the profits derived from their sale as slaves.\
\
Whatever the motive for their coming, however, they managed to get\
across the sea. The immigrants set to work with a will. They cut down\
forests, built houses, and laid out fields. They founded churches,\
schools, and colleges. They set up forges and workshops. They spun and\
wove. They fashioned ships and sailed the seas. They bartered and\
traded. Here and there on favorable harbors they established centers of\
commerce--Boston, Providence, New York, Philadelphia, Baltimore, and\
Charleston. As soon as a firm foothold was secured on the shore line\
they pressed westward until, by the close of the colonial period, they\
were already on the crest of the Alleghanies.\
\
Though they were widely scattered along a thousand miles of seacoast,\
the colonists were united in spirit by many common ties. The major\
portion of them were Protestants. The language, the law, and the\
literature of England furnished the basis of national unity. Most of the\
colonists were engaged in the same hard task; that of conquering a\
wilderness. To ties of kinship and language were added ties created by\
necessity. They had to unite in defense; first, against the Indians and\
later against the French. They were all subjects of the same\
sovereign--the king of England. The English Parliament made laws for\
them and the English government supervised their local affairs, their\
trade, and their manufactures. Common forces assailed them. Common\
grievances vexed them. Common hopes inspired them.\
\
Many of the things which tended to unite them likewise tended to throw\
them into opposition to the British Crown and Parliament. Most of them\
were freeholders; that is, farmers who owned their own land and tilled\
it with their own hands. A free soil nourished the spirit of freedom.\
The majority of them were Dissenters, critics, not friends, of the\
Church of England, that stanch defender of the British monarchy. Each\
colony in time developed its own legislature elected by the voters; it\
grew accustomed to making laws and laying taxes for itself. Here was a\
people learning self-reliance and self-government. The attempts to\
strengthen the Church of England in America and the transformation of\
colonies into royal provinces only fanned the spirit of independence\
which they were designed to quench.\
\
Nevertheless, the Americans owed much of their prosperity to the\
assistance of the government that irritated them. It was the protection\
of the British navy that prevented Holland, Spain, and France from\
wiping out their settlements. Though their manufacture and trade were\
controlled in the interests of the mother country, they also enjoyed\
great advantages in her markets. Free trade existed nowhere upon the\
earth; but the broad empire of Britain was open to American ships and\
merchandise. It could be said, with good reason, that the disadvantages\
which the colonists suffered through British regulation of their\
industry and trade were more than offset by the privileges they enjoyed.\
Still that is somewhat beside the point, for mere economic advantage is\
not necessarily the determining factor in the fate of peoples. A\
thousand circumstances had helped to develop on this continent a nation,\
to inspire it with a passion for independence, and to prepare it for a\
destiny greater than that of a prosperous dominion of the British\
empire. The economists, who tried to prove by logic unassailable that\
America would be richer under the British flag, could not change the\
spirit of Patrick Henry, Samuel Adams, Benjamin Franklin, or George\
Washington.\
\
\
=References=\
\
G.L. Beer, _Origin of the British Colonial System_ and _The Old Colonial\
System_.\
\
A. Bradley, _The Fight for Canada in North America_.\
\
C.M. Andrews, _Colonial Self-Government_ (American Nation Series).\
\
H. Egerton, _Short History of British Colonial Policy_.\
\
F. Parkman, _France and England in North America_ (12 vols.).\
\
R. Thwaites, _France in America_ (American Nation Series).\
\
J. Winsor, _The Mississippi Valley_ and _Cartier to Frontenac_.\
\
\
=Questions=\
\
1. How would you define "nationalism"?\
\
2. Can you give any illustrations of the way that war promotes\
nationalism?\
\
3. Why was it impossible to establish and maintain a uniform policy in\
dealing with the Indians?\
\
4. What was the outcome of the final clash with the French?\
\
5. Enumerate the five chief results of the wars with the French and the\
Indians. Discuss each in detail.\
\
6. Explain why it was that the character of the English king mattered to\
the colonists.\
\
7. Contrast England under the Stuarts with England under the\
Hanoverians.\
\
8. Explain how the English Crown, Courts, and Parliament controlled the\
colonies.\
\
9. Name the three important classes of English legislation affecting the\
colonies. Explain each.\
\
10. Do you think the English legislation was beneficial or injurious to\
the colonies? Why?\
\
\
=Research Topics=\
\
=Rise of French Power in North America.=--Special reference: Francis\
Parkman, _Struggle for a Continent_.\
\
=The French and Indian Wars.=--Special reference: W.M. Sloane, _French\
War and the Revolution_, Chaps. VI-IX. Parkman, _Montcalm and Wolfe_,\
Vol. II, pp. 195-299. Elson, _History of the United States_, pp.\
171-196.\
\
=English Navigation Acts.=--Macdonald, _Documentary Source Book_, pp.\
55, 72, 78, 90, 103. Coman, _Industrial History_, pp. 79-85.\
\
=British Colonial Policy.=--Callender, _Economic History of the United\
States_, pp. 102-108.\
\
=The New England Confederation.=--Analyze the document in Macdonald,\
_Source Book_, p. 45. Special reference: Fiske, _Beginnings of New\
England_, pp. 140-198.\
\
=The Administration of Andros.=--Fiske, _Beginnings_, pp. 242-278.\
\
=Biographical Studies.=--William Pitt and Sir Robert Walpole. Consult\
Green, _Short History of England_, on their policies, using the index.\
\
\
\
\
PART II. CONFLICT AND INDEPENDENCE\
\
\
\
\
CHAPTER V\
\
THE NEW COURSE IN BRITISH IMPERIAL POLICY\
\
\
On October 25, 1760, King George II died and the British crown passed to\
his young grandson. The first George, the son of the Elector of Hanover\
and Sophia the granddaughter of James I, was a thorough German who never\
even learned to speak the language of the land over which he reigned.\
The second George never saw England until he was a man. He spoke English\
with an accent and until his death preferred his German home. During\
their reign, the principle had become well established that the king did\
not govern but acted only through ministers representing the majority in\
Parliament.\
\
\
GEORGE III AND HIS SYSTEM\
\
=The Character of the New King.=--The third George rudely broke the\
German tradition of his family. He resented the imputation that he was a\
foreigner and on all occasions made a display of his British sympathies.\
To the draft of his first speech to Parliament, he added the popular\
phrase: "Born and educated in this country, I glory in the name of\
Briton." Macaulay, the English historian, certainly of no liking for\
high royal prerogative, said of George: "The young king was a born\
Englishman. All his tastes and habits, good and bad, were English. No\
portion of his subjects had anything to reproach him with.... His age,\
his appearance, and all that was known of his character conciliated\
public favor. He was in the bloom of youth; his person and address were\
pleasing; scandal imputed to him no vice; and flattery might without\
glaring absurdity ascribe to him many princely virtues."\
\
Nevertheless George III had been spoiled by his mother, his tutors, and\
his courtiers. Under their influence he developed high and mighty\
notions about the sacredness of royal authority and his duty to check\
the pretensions of Parliament and the ministers dependent upon it. His\
mother had dinned into his ears the slogan: "George, be king!" Lord\
Bute, his teacher and adviser, had told him that his honor required him\
to take an active part in the shaping of public policy and the making of\
laws. Thus educated, he surrounded himself with courtiers who encouraged\
him in the determination to rule as well as reign, to subdue all\
parties, and to place himself at the head of the nation and empire.\
\
[Illustration: _From an old print._\
\
GEORGE III]\
\
=Political Parties and George III.=--The state of the political parties\
favored the plans of the king to restore some of the ancient luster of\
the crown. The Whigs, who were composed mainly of the smaller\
freeholders, merchants, inhabitants of towns, and Protestant\
non-conformists, had grown haughty and overbearing through long\
continuance in power and had as a consequence raised up many enemies in\
their own ranks. Their opponents, the Tories, had by this time given up\
all hope of restoring to the throne the direct Stuart line; but they\
still cherished their old notions about divine right. With the\
accession of George III the coveted opportunity came to them to rally\
around the throne again. George received his Tory friends with open\
arms, gave them offices, and bought them seats in the House of Commons.\
\
=The British Parliamentary System.=--The peculiarities of the British\
Parliament at the time made smooth the way for the king and his allies\
with their designs for controlling the entire government. In the first\
place, the House of Lords was composed mainly of hereditary nobles whose\
number the king could increase by the appointment of his favorites, as\
of old. Though the members of the House of Commons were elected by\
popular vote, they did not speak for the mass of English people. Great\
towns like Leeds, Manchester, and Birmingham, for example, had no\
representatives at all. While there were about eight million inhabitants\
in Great Britain, there were in 1768 only about 160,000 voters; that is\
to say, only about one in every ten adult males had a voice in the\
government. Many boroughs returned one or more members to the Commons\
although they had merely a handful of voters or in some instances no\
voters at all. Furthermore, these tiny boroughs were often controlled by\
lords who openly sold the right of representation to the highest bidder.\
The "rotten-boroughs," as they were called by reformers, were a public\
scandal, but George III readily made use of them to get his friends into\
the House of Commons.\
\
\
GEORGE III'S MINISTERS AND THEIR COLONIAL POLICIES\
\
=Grenville and the War Debt.=--Within a year after the accession of\
George III, William Pitt was turned out of office, the king treating him\
with "gross incivility" and the crowds shouting "Pitt forever!" The\
direction of affairs was entrusted to men enjoying the king's\
confidence. Leadership in the House of Commons fell to George Grenville,\
a grave and laborious man who for years had groaned over the increasing\
cost of government.\
\
The first task after the conclusion of peace in 1763 was the adjustment\
of the disordered finances of the kingdom. The debt stood at the highest\
point in the history of the country. More revenue was absolutely\
necessary and Grenville began to search for it, turning his attention\
finally to the American colonies. In this quest he had the aid of a\
zealous colleague, Charles Townshend, who had long been in public\
service and was familiar with the difficulties encountered by royal\
governors in America. These two men, with the support of the entire\
ministry, inaugurated in February, 1763, "a new system of colonial\
government. It was announced by authority that there were to be no more\
requisitions from the king to the colonial assemblies for supplies, but\
that the colonies were to be taxed instead by act of Parliament.\
Colonial governors and judges were to be paid by the Crown; they were to\
be supported by a standing army of twenty regiments; and all the\
expenses of this force were to be met by parliamentary taxation."\
\
=Restriction of Paper Money (1763).=--Among the many complaints filed\
before the board of trade were vigorous protests against the issuance of\
paper money by the colonial legislatures. The new ministry provided a\
remedy in the act of 1763, which declared void all colonial laws\
authorizing paper money or extending the life of outstanding bills. This\
law was aimed at the "cheap money" which the Americans were fond of\
making when specie was scarce--money which they tried to force on their\
English creditors in return for goods and in payment of the interest and\
principal of debts. Thus the first chapter was written in the long\
battle over sound money on this continent.\
\
=Limitation on Western Land Sales.=--Later in the same year (1763)\
George III issued a royal proclamation providing, among other things,\
for the government of the territory recently acquired by the treaty of\
Paris from the French. One of the provisions in this royal decree\
touched frontiersmen to the quick. The contests between the king's\
officers and the colonists over the disposition of western lands had\
been long and sharp. The Americans chafed at restrictions on\
settlement. The more adventurous were continually moving west and\
"squatting" on land purchased from the Indians or simply seized without\
authority. To put an end to this, the king forbade all further purchases\
from the Indians, reserving to the crown the right to acquire such lands\
and dispose of them for settlement. A second provision in the same\
proclamation vested the power of licensing trade with the Indians,\
including the lucrative fur business, in the hands of royal officers in\
the colonies. These two limitations on American freedom and enterprise\
were declared to be in the interest of the crown and for the\
preservation of the rights of the Indians against fraud and abuses.\
\
=The Sugar Act of 1764.=--King George's ministers next turned their\
attention to measures of taxation and trade. Since the heavy debt under\
which England was laboring had been largely incurred in the defense of\
America, nothing seemed more reasonable to them than the proposition\
that the colonies should help to bear the burden which fell so heavily\
upon the English taxpayer. The Sugar Act of 1764 was the result of this\
reasoning. There was no doubt about the purpose of this law, for it was\
set forth clearly in the title: "An act for granting certain duties in\
the British colonies and plantations in America ... for applying the\
produce of such duties ... towards defraying the expenses of defending,\
protecting and securing the said colonies and plantations ... and for\
more effectually preventing the clandestine conveyance of goods to and\
from the said colonies and plantations and improving and securing the\
trade between the same and Great Britain." The old Molasses Act had been\
prohibitive; the Sugar Act of 1764 was clearly intended as a revenue\
measure. Specified duties were laid upon sugar, indigo, calico, silks,\
and many other commodities imported into the colonies. The enforcement\
of the Molasses Act had been utterly neglected; but this Sugar Act had\
"teeth in it." Special precautions as to bonds, security, and\
registration of ship masters, accompanied by heavy penalties, promised\
a vigorous execution of the new revenue law.\
\
The strict terms of the Sugar Act were strengthened by administrative\
measures. Under a law of the previous year the commanders of armed\
vessels stationed along the American coast were authorized to stop,\
search, and, on suspicion, seize merchant ships approaching colonial\
ports. By supplementary orders, the entire British official force in\
America was instructed to be diligent in the execution of all trade and\
navigation laws. Revenue collectors, officers of the army and navy, and\
royal governors were curtly ordered to the front to do their full duty\
in the matter of law enforcement. The ordinary motives for the discharge\
of official obligations were sharpened by an appeal to avarice, for\
naval officers who seized offenders against the law were rewarded by\
large prizes out of the forfeitures and penalties.\
\
=The Stamp Act (1765).=--The Grenville-Townshend combination moved\
steadily towards its goal. While the Sugar Act was under consideration\
in Parliament, Grenville announced a plan for a stamp bill. The next\
year it went through both Houses with a speed that must have astounded\
its authors. The vote in the Commons stood 205 in favor to 49 against;\
while in the Lords it was not even necessary to go through the formality\
of a count. As George III was temporarily insane, the measure received\
royal assent by a commission acting as a board of regency. Protests of\
colonial agents in London were futile. "We might as well have hindered\
the sun's progress!" exclaimed Franklin. Protests of a few opponents in\
the Commons were equally vain. The ministry was firm in its course and\
from all appearances the Stamp Act hardly roused as much as a languid\
interest in the city of London. In fact, it is recorded that the fateful\
measure attracted less notice than a bill providing for a commission to\
act for the king when he was incapacitated.\
\
The Stamp Act, like the Sugar Act, declared the purpose of the British\
government to raise revenue in America "towards defraying the expenses\
of defending, protecting, and securing the British colonies and\
plantations in America." It was a long measure of more than fifty\
sections, carefully planned and skillfully drawn. By its provisions\
duties were imposed on practically all papers used in legal\
transactions,--deeds, mortgages, inventories, writs, bail bonds,--on\
licenses to practice law and sell liquor, on college diplomas, playing\
cards, dice, pamphlets, newspapers, almanacs, calendars, and\
advertisements. The drag net was closely knit, for scarcely anything\
escaped.\
\
=The Quartering Act (1765).=--The ministers were aware that the Stamp\
Act would rouse opposition in America--how great they could not\
conjecture. While the measure was being debated, a friend of General\
Wolfe, Colonel Barre, who knew America well, gave them an ominous\
warning in the Commons. "Believe me--remember I this day told you so--"\
he exclaimed, "the same spirit of freedom which actuated that people at\
first will accompany them still ... a people jealous of their liberties\
and who will vindicate them, if ever they should be violated." The\
answer of the ministry to a prophecy of force was a threat of force.\
Preparations were accordingly made to dispatch a larger number of\
soldiers than usual to the colonies, and the ink was hardly dry on the\
Stamp Act when Parliament passed the Quartering Act ordering the\
colonists to provide accommodations for the soldiers who were to enforce\
the new laws. "We have the power to tax them," said one of the ministry,\
"and we will tax them."\
\
\
COLONIAL RESISTANCE FORCES REPEAL\
\
=Popular Opposition.=--The Stamp Act was greeted in America by an\
outburst of denunciation. The merchants of the seaboard cities took the\
lead in making a dignified but unmistakable protest, agreeing not to\
import British goods while the hated law stood upon the books. Lawyers,\
some of them incensed at the heavy taxes on their operations and others\
intimidated by patriots who refused to permit them to use stamped\
papers, joined with the merchants. Aristocratic colonial Whigs, who had\
long grumbled at the administration of royal governors, protested\
against taxation without their consent, as the Whigs had done in old\
England. There were Tories, however, in the colonies as in England--many\
of them of the official class--who denounced the merchants, lawyers, and\
Whig aristocrats as "seditious, factious and republican." Yet the\
opposition to the Stamp Act and its accompanying measure, the Quartering\
Act, grew steadily all through the summer of 1765.\
\
In a little while it was taken up in the streets and along the\
countryside. All through the North and in some of the Southern colonies,\
there sprang up, as if by magic, committees and societies pledged to\
resist the Stamp Act to the bitter end. These popular societies were\
known as Sons of Liberty and Daughters of Liberty: the former including\
artisans, mechanics, and laborers; and the latter, patriotic women. Both\
groups were alike in that they had as yet taken little part in public\
affairs. Many artisans, as well as all the women, were excluded from the\
right to vote for colonial assemblymen.\
\
While the merchants and Whig gentlemen confined their efforts chiefly to\
drafting well-phrased protests against British measures, the Sons of\
Liberty operated in the streets and chose rougher measures. They stirred\
up riots in Boston, New York, Philadelphia, and Charleston when attempts\
were made to sell the stamps. They sacked and burned the residences of\
high royal officers. They organized committees of inquisition who by\
threats and intimidation curtailed the sale of British goods and the use\
of stamped papers. In fact, the Sons of Liberty carried their operations\
to such excesses that many mild opponents of the stamp tax were\
frightened and drew back in astonishment at the forces they had\
unloosed. The Daughters of Liberty in a quieter way were making a very\
effective resistance to the sale of the hated goods by spurring on\
domestic industries, their own particular province being the manufacture\
of clothing, and devising substitutes for taxed foods. They helped to\
feed and clothe their families without buying British goods.\
\
=Legislative Action against the Stamp Act.=--Leaders in the colonial\
assemblies, accustomed to battle against British policies, supported the\
popular protest. The Stamp Act was signed on March 22, 1765. On May 30,\
the Virginia House of Burgesses passed a set of resolutions declaring\
that the General Assembly of the colony alone had the right to lay taxes\
upon the inhabitants and that attempts to impose them otherwise were\
"illegal, unconstitutional, and unjust." It was in support of these\
resolutions that Patrick Henry uttered the immortal challenge: "Caesar\
had his Brutus, Charles I his Cromwell, and George III...." Cries of\
"Treason" were calmly met by the orator who finished: "George III may\
profit by their example. If that be treason, make the most of it."\
\
[Illustration: PATRICK HENRY]\
\
=The Stamp Act Congress.=--The Massachusetts Assembly answered the call\
of Virginia by inviting the colonies to elect delegates to a Congress to\
be held in New York to discuss the situation. Nine colonies responded\
and sent representatives. The delegates, while professing the warmest\
affection for the king's person and government, firmly spread on record\
a series of resolutions that admitted of no double meaning. They\
declared that taxes could not be imposed without their consent, given\
through their respective colonial assemblies; that the Stamp Act showed\
a tendency to subvert their rights and liberties; that the recent trade\
acts were burdensome and grievous; and that the right to petition the\
king and Parliament was their heritage. They thereupon made "humble\
supplication" for the repeal of the Stamp Act.\
\
The Stamp Act Congress was more than an assembly of protest. It marked\
the rise of a new agency of government to express the will of America.\
It was the germ of a government which in time was to supersede the\
government of George III in the colonies. It foreshadowed the Congress\
of the United States under the Constitution. It was a successful attempt\
at union. "There ought to be no New England men," declared Christopher\
Gadsden, in the Stamp Act Congress, "no New Yorkers known on the\
Continent, but all of us Americans."\
\
=The Repeal of the Stamp Act and the Sugar Act.=--The effect of American\
resistance on opinion in England was telling. Commerce with the colonies\
had been effectively boycotted by the Americans; ships lay idly swinging\
at the wharves; bankruptcy threatened hundreds of merchants in London,\
Bristol, and Liverpool. Workingmen in the manufacturing towns of England\
were thrown out of employment. The government had sown folly and was\
reaping, in place of the coveted revenue, rebellion.\
\
Perplexed by the storm they had raised, the ministers summoned to the\
bar of the House of Commons, Benjamin Franklin, the agent for\
Pennsylvania, who was in London. "Do you think it right," asked\
Grenville, "that America should be protected by this country and pay no\
part of the expenses?" The answer was brief: "That is not the case; the\
colonies raised, clothed, and paid during the last war twenty-five\
thousand men and spent many millions." Then came an inquiry whether the\
colonists would accept a modified stamp act. "No, never," replied\
Franklin, "never! They will never submit to it!" It was next suggested\
that military force might compel obedience to law. Franklin had a ready\
answer. "They cannot force a man to take stamps.... They may not find a\
rebellion; they may, indeed, make one."\
\
The repeal of the Stamp Act was moved in the House of Commons a few days\
later. The sponsor for the repeal spoke of commerce interrupted, debts\
due British merchants placed in jeopardy, Manchester industries closed,\
workingmen unemployed, oppression instituted, and the loss of the\
colonies threatened. Pitt and Edmund Burke, the former near the close\
of his career, the latter just beginning his, argued cogently in favor\
of retracing the steps taken the year before. Grenville refused.\
"America must learn," he wailed, "that prayers are not to be brought to\
Caesar through riot and sedition." His protests were idle. The Commons\
agreed to the repeal on February 22, 1766, amid the cheers of the\
victorious majority. It was carried through the Lords in the face of\
strong opposition and, on March 18, reluctantly signed by the king, now\
restored to his right mind.\
\
In rescinding the Stamp Act, Parliament did not admit the contention of\
the Americans that it was without power to tax them. On the contrary, it\
accompanied the repeal with a Declaratory Act. It announced that the\
colonies were subordinate to the crown and Parliament of Great Britain;\
that the king and Parliament therefore had undoubted authority to make\
laws binding the colonies in all cases whatsoever; and that the\
resolutions and proceedings of the colonists denying such authority were\
null and void.\
\
The repeal was greeted by the colonists with great popular\
demonstrations. Bells were rung; toasts to the king were drunk; and\
trade resumed its normal course. The Declaratory Act, as a mere paper\
resolution, did not disturb the good humor of those who again cheered\
the name of King George. Their confidence was soon strengthened by the\
news that even the Sugar Act had been repealed, thus practically\
restoring the condition of affairs before Grenville and Townshend\
inaugurated their policy of "thoroughness."\
\
\
RESUMPTION OF BRITISH REVENUE AND COMMERCIAL POLICIES\
\
=The Townshend Acts (1767).=--The triumph of the colonists was brief.\
Though Pitt, the friend of America, was once more prime minister, and\
seated in the House of Lords as the Earl of Chatham, his severe illness\
gave to Townshend and the Tory party practical control over Parliament.\
Unconvinced by the experience with the Stamp Act, Townshend brought\
forward and pushed through both Houses of Parliament three measures,\
which to this day are associated with his name. First among his\
restrictive laws was that of June 29, 1767, which placed the enforcement\
of the collection of duties and customs on colonial imports and exports\
in the hands of British commissioners appointed by the king, resident in\
the colonies, paid from the British treasury, and independent of all\
control by the colonists. The second measure of the same date imposed a\
tax on lead, glass, paint, tea, and a few other articles imported into\
the colonies, the revenue derived from the duties to be applied toward\
the payment of the salaries and other expenses of royal colonial\
officials. A third measure was the Tea Act of July 2, 1767, aimed at the\
tea trade which the Americans carried on illegally with foreigners. This\
law abolished the duty which the East India Company had to pay in\
England on tea exported to America, for it was thought that English tea\
merchants might thus find it possible to undersell American tea\
smugglers.\
\
=Writs of Assistance Legalized by Parliament.=--Had Parliament been\
content with laying duties, just as a manifestation of power and right,\
and neglected their collection, perhaps little would have been heard of\
the Townshend Acts. It provided, however, for the strict, even the\
harsh, enforcement of the law. It ordered customs officers to remain at\
their posts and put an end to smuggling. In the revenue act of June 29,\
1767, it expressly authorized the superior courts of the colonies to\
issue "writs of assistance," empowering customs officers to enter "any\
house, warehouse, shop, cellar, or other place in the British colonies\
or plantations in America to search for and seize" prohibited or\
smuggled goods.\
\
The writ of assistance, which was a general search warrant issued to\
revenue officers, was an ancient device hateful to a people who\
cherished the spirit of personal independence and who had made actual\
gains in the practice of civil liberty. To allow a "minion of the law"\
to enter a man's house and search his papers and premises, was too much\
for the emotions of people who had fled to America in a quest for\
self-government and free homes, who had braved such hardships to\
establish them, and who wanted to trade without official interference.\
\
The writ of assistance had been used in Massachusetts in 1755 to prevent\
illicit trade with Canada and had aroused a violent hostility at that\
time. In 1761 it was again the subject of a bitter controversy which\
arose in connection with the application of a customs officer to a\
Massachusetts court for writs of assistance "as usual." This application\
was vainly opposed by James Otis in a speech of five hours' duration--a\
speech of such fire and eloquence that it sent every man who heard it\
away "ready to take up arms against writs of assistance." Otis denounced\
the practice as an exercise of arbitrary power which had cost one king\
his head and another his throne, a tyrant's device which placed the\
liberty of every man in jeopardy, enabling any petty officer to work\
possible malice on any innocent citizen on the merest suspicion, and to\
spread terror and desolation through the land. "What a scene," he\
exclaimed, "does this open! Every man, prompted by revenge, ill-humor,\
or wantonness to inspect the inside of his neighbor's house, may get a\
writ of assistance. Others will ask it from self-defense; one arbitrary\
exertion will provoke another until society is involved in tumult and\
blood." He did more than attack the writ itself. He said that Parliament\
could not establish it because it was against the British constitution.\
This was an assertion resting on slender foundation, but it was quickly\
echoed by the people. Then and there James Otis sounded the call to\
America to resist the exercise of arbitrary power by royal officers.\
"Then and there," wrote John Adams, "the child Independence was born."\
Such was the hated writ that Townshend proposed to put into the hands of\
customs officers in his grim determination to enforce the law.\
\
=The New York Assembly Suspended.=--In the very month that Townshend's\
Acts were signed by the king, Parliament took a still more drastic step.\
The assembly of New York, protesting against the "ruinous and\
insupportable" expense involved, had failed to make provision for the\
care of British troops in accordance with the terms of the Quartering\
Act. Parliament therefore suspended the assembly until it promised to\
obey the law. It was not until a third election was held that compliance\
with the Quartering Act was wrung from the reluctant province. In the\
meantime, all the colonies had learned on how frail a foundation their\
representative bodies rested.\
\
\
RENEWED RESISTANCE IN AMERICA\
\
=The Massachusetts Circular (1768).=--Massachusetts, under the\
leadership of Samuel Adams, resolved to resist the policy of renewed\
intervention in America. At his suggestion the assembly adopted a\
Circular Letter addressed to the assemblies of the other colonies\
informing them of the state of affairs in Massachusetts and roundly\
condemning the whole British program. The Circular Letter declared that\
Parliament had no right to lay taxes on Americans without their consent\
and that the colonists could not, from the nature of the case, be\
represented in Parliament. It went on shrewdly to submit to\
consideration the question as to whether any people could be called free\
who were subjected to governors and judges appointed by the crown and\
paid out of funds raised independently. It invited the other colonies,\
in the most temperate tones, to take thought about the common\
predicament in which they were all placed.\
\
[Illustration: _From an old print._\
\
SAMUEL ADAMS]\
\
=The Dissolution of Assemblies.=--The governor of Massachusetts, hearing\
of the Circular Letter, ordered the assembly to rescind its appeal. On\
meeting refusal, he promptly dissolved it. The Maryland, Georgia, and\
South Carolina assemblies indorsed the Circular Letter and were also\
dissolved at once. The Virginia House of Burgesses, thoroughly aroused,\
passed resolutions on May 16, 1769, declaring that the sole right of\
imposing taxes in Virginia was vested in its legislature, asserting anew\
the right of petition to the crown, condemning the transportation of\
persons accused of crimes or trial beyond the seas, and beseeching the\
king for a redress of the general grievances. The immediate dissolution\
of the Virginia assembly, in its turn, was the answer of the royal\
governor.\
\
=The Boston Massacre.=--American opposition to the British authorities\
kept steadily rising as assemblies were dissolved, the houses of\
citizens searched, and troops distributed in increasing numbers among\
the centers of discontent. Merchants again agreed not to import British\
goods, the Sons of Liberty renewed their agitation, and women set about\
the patronage of home products still more loyally.\
\
On the night of March 5, 1770, a crowd on the streets of Boston began to\
jostle and tease some British regulars stationed in the town. Things\
went from bad to worse until some "boys and young fellows" began to\
throw snowballs and stones. Then the exasperated soldiers fired into the\
crowd, killing five and wounding half a dozen more. The day after the\
"massacre," a mass meeting was held in the town and Samuel Adams was\
sent to demand the withdrawal of the soldiers. The governor hesitated\
and tried to compromise. Finding Adams relentless, the governor yielded\
and ordered the regulars away.\
\
The Boston Massacre stirred the country from New Hampshire to Georgia.\
Popular passions ran high. The guilty soldiers were charged with murder.\
Their defense was undertaken, in spite of the wrath of the populace, by\
John Adams and Josiah Quincy, who as lawyers thought even the worst\
\
offenders entitled to their full rights in law. In his speech to the\
jury, however, Adams warned the British government against its course,\
saying, that "from the nature of things soldiers quartered in a populous\
town will always occasion two mobs where they will prevent one." Two of\
the soldiers were convicted and lightly punished.\
\
=Resistance in the South.=--The year following the Boston Massacre some\
citizens of North Carolina, goaded by the conduct of the royal governor,\
openly resisted his authority. Many were killed as a result and seven\
who were taken prisoners were hanged as traitors. A little later royal\
troops and local militia met in a pitched battle near Alamance River,\
called the "Lexington of the South."\
\
=The _Gaspee_ Affair and the Virginia Resolutions of 1773.=--On sea as\
well as on land, friction between the royal officers and the colonists\
broke out into overt acts. While patrolling Narragansett Bay looking for\
smugglers one day in 1772, the armed ship, _Gaspee_, ran ashore and was\
caught fast. During the night several men from Providence boarded the\
vessel and, after seizing the crew, set it on fire. A royal commission,\
sent to Rhode Island to discover the offenders and bring them to\
account, failed because it could not find a single informer. The very\
appointment of such a commission aroused the patriots of Virginia to\
action; and in March, 1773, the House of Burgesses passed a resolution\
creating a standing committee of correspondence to develop cooperation\
among the colonies in resistance to British measures.\
\
=The Boston Tea Party.=--Although the British government, finding the\
Townshend revenue act a failure, repealed in 1770 all the duties except\
that on tea, it in no way relaxed its resolve to enforce the other\
commercial regulations it had imposed on the colonies. Moreover,\
Parliament decided to relieve the British East India Company of the\
financial difficulties into which it had fallen partly by reason of the\
Tea Act and the colonial boycott that followed. In 1773 it agreed to\
return to the Company the regular import duties, levied in England, on\
all tea transshipped to America. A small impost of three pence, to be\
collected in America, was left as a reminder of the principle laid down\
in the Declaratory Act that Parliament had the right to tax the\
colonists.\
\
This arrangement with the East India Company was obnoxious to the\
colonists for several reasons. It was an act of favoritism for one\
thing, in the interest of a great monopoly. For another thing, it\
promised to dump on the American market, suddenly, an immense amount of\
cheap tea and so cause heavy losses to American merchants who had large\
stocks on hand. It threatened with ruin the business of all those who\
were engaged in clandestine trade with the Dutch. It carried with it an\
irritating tax of three pence on imports. In Charleston, Annapolis, New\
York, and Boston, captains of ships who brought tea under this act were\
roughly handled. One night in December, 1773, a band of Boston citizens,\
disguised as Indians, boarded the hated tea ships and dumped the cargo\
into the harbor. This was serious business, for it was open, flagrant,\
determined violation of the law. As such the British government viewed\
it.\
\
\
RETALIATION BY THE BRITISH GOVERNMENT\
\
=Reception of the News of the Tea Riot.=--The news of the tea riot in\
Boston confirmed King George in his conviction that there should be no\
soft policy in dealing with his American subjects. "The die is cast," he\
stated with evident satisfaction. "The colonies must either triumph or\
submit.... If we take the resolute part, they will undoubtedly be very\
meek." Lord George Germain characterized the tea party as "the\
proceedings of a tumultuous and riotous rabble who ought, if they had\
the least prudence, to follow their mercantile employments and not\
trouble themselves with politics and government, which they do not\
understand." This expressed, in concise form, exactly the sentiments of\
Lord North, who had then for three years been the king's chief minister.\
Even Pitt, Lord Chatham, was prepared to support the government in\
upholding its authority.\
\
=The Five Intolerable Acts.=--Parliament, beginning on March 31, 1774,\
passed five stringent measures, known in American history as the five\
"intolerable acts." They were aimed at curing the unrest in America. The\
_first_ of them was a bill absolutely shutting the port of Boston to\
commerce with the outside world. The _second_, following closely,\
revoked the Massachusetts charter of 1691 and provided furthermore that\
the councilors should be appointed by the king, that all judges should\
be named by the royal governor, and that town meetings (except to elect\
certain officers) could not be held without the governor's consent. A\
_third_ measure, after denouncing the "utter subversion of all lawful\
government" in the provinces, authorized royal agents to transfer to\
Great Britain or to other colonies the trials of officers or other\
persons accused of murder in connection with the enforcement of the law.\
The _fourth_ act legalized the quartering of troops in Massachusetts\
towns. The _fifth_ of the measures was the Quebec Act, which granted\
religious toleration to the Catholics in Canada, extended the boundaries\
of Quebec southward to the Ohio River, and established, in this western\
region, government by a viceroy.\
\
The intolerable acts went through Parliament with extraordinary\
celerity. There was an opposition, alert and informed; but it was\
ineffective. Burke spoke eloquently against the Boston port bill,\
condemning it roundly for punishing the innocent with the guilty, and\
showing how likely it was to bring grave consequences in its train. He\
was heard with respect and his pleas were rejected. The bill passed both\
houses without a division, the entry "unanimous" being made upon their\
journals although it did not accurately represent the state of opinion.\
The law destroying the charter of Massachusetts passed the Commons by a\
vote of three to one; and the third intolerable act by a vote of four to\
one. The triumph of the ministry was complete. "What passed in Boston,"\
exclaimed the great jurist, Lord Mansfield, "is the overt act of High\
Treason proceeding from our over lenity and want of foresight." The\
crown and Parliament were united in resorting to punitive measures.\
\
In the colonies the laws were received with consternation. To the\
American Protestants, the Quebec Act was the most offensive. That\
project they viewed not as an act of grace or of mercy but as a direct\
attempt to enlist French Canadians on the side of Great Britain. The\
British government did not grant religious toleration to Catholics\
either at home or in Ireland and the Americans could see no good motive\
in granting it in North America. The act was also offensive because\
Massachusetts, Connecticut, and Virginia had, under their charters,\
large claims in the territory thus annexed to Quebec.\
\
To enforce these intolerable acts the military arm of the British\
government was brought into play. The commander-in-chief of the armed\
forces in America, General Gage, was appointed governor of\
Massachusetts. Reinforcements were brought to the colonies, for now King\
George was to give "the rebels," as he called them, a taste of strong\
medicine. The majesty of his law was to be vindicated by force.\
\
\
FROM REFORM TO REVOLUTION IN AMERICA\
\
=The Doctrine of Natural Rights.=--The dissolution of assemblies, the\
destruction of charters, and the use of troops produced in the colonies\
a new phase in the struggle. In the early days of the contest with the\
British ministry, the Americans spoke of their "rights as Englishmen"\
and condemned the acts of Parliament as unlawful, as violating the\
principles of the English constitution under which they all lived. When\
they saw that such arguments had no effect on Parliament, they turned\
for support to their "natural rights." The latter doctrine, in the form\
in which it was employed by the colonists, was as English as the\
constitutional argument. John Locke had used it with good effect in\
defense of the English revolution in the seventeenth century. American\
leaders, familiar with the writings of Locke, also took up his thesis in\
the hour of their distress. They openly declared that their rights did\
not rest after all upon the English constitution or a charter from the\
crown. "Old Magna Carta was not the beginning of all things," retorted\
Otis when the constitutional argument failed. "A time may come when\
Parliament shall declare every American charter void, but the natural,\
inherent, and inseparable rights of the colonists as men and as citizens\
would remain and whatever became of charters can never be abolished\
until the general conflagration." Of the same opinion was the young and\
impetuous Alexander Hamilton. "The sacred rights of mankind," he\
exclaimed, "are not to be rummaged for among old parchments or musty\
records. They are written as with a sunbeam in the whole volume of human\
destiny by the hand of divinity itself, and can never be erased or\
obscured by mortal power."\
\
Firm as the American leaders were in the statement and defense of their\
rights, there is every reason for believing that in the beginning they\
hoped to confine the conflict to the realm of opinion. They constantly\
avowed that they were loyal to the king when protesting in the strongest\
language against his policies. Even Otis, regarded by the loyalists as a\
firebrand, was in fact attempting to avert revolution by winning\
concessions from England. "I argue this cause with the greater\
pleasure," he solemnly urged in his speech against the writs of\
assistance, "as it is in favor of British liberty ... and as it is in\
opposition to a kind of power, the exercise of which in former periods\
cost one king of England his head and another his throne."\
\
=Burke Offers the Doctrine of Conciliation.=--The flooding tide of\
American sentiment was correctly measured by one Englishman at least,\
Edmund Burke, who quickly saw that attempts to restrain the rise of\
American democracy were efforts to reverse the processes of nature. He\
saw how fixed and rooted in the nature of things was the American\
spirit--how inevitable, how irresistible. He warned his countrymen that\
there were three ways of handling the delicate situation--and only\
three. One was to remove the cause of friction by changing the spirit of\
the colonists--an utter impossibility because that spirit was grounded\
in the essential circumstances of American life. The second was to\
prosecute American leaders as criminals; of this he begged his\
countrymen to beware lest the colonists declare that "a government\
against which a claim of liberty is tantamount to high treason is a\
government to which submission is equivalent to slavery." The third and\
right way to meet the problem, Burke concluded, was to accept the\
American spirit, repeal the obnoxious measures, and receive the colonies\
into equal partnership.\
\
=Events Produce the Great Decision.=--The right way, indicated by Burke,\
was equally impossible to George III and the majority in Parliament. To\
their narrow minds, American opinion was contemptible and American\
resistance unlawful, riotous, and treasonable. The correct way, in their\
view, was to dispatch more troops to crush the "rebels"; and that very\
act took the contest from the realm of opinion. As John Adams said:\
"Facts are stubborn things." Opinions were unseen, but marching soldiers\
were visible to the veriest street urchin. "Now," said Gouverneur\
Morris, "the sheep, simple as they are, cannot be gulled as heretofore."\
It was too late to talk about the excellence of the British\
constitution. If any one is bewildered by the controversies of modern\
historians as to why the crisis came at last, he can clarify his\
understanding by reading again Edmund Burke's stately oration, _On\
Conciliation with America_.\
\
\
=References=\
\
G.L. Beer, _British Colonial Policy_ (1754-63).\
\
E. Channing, _History of the United States_, Vol. III.\
\
R. Frothingham, _Rise of the Republic_.\
\
G.E. Howard, _Preliminaries of the Revolution_ (American Nation Series).\
\
J.K. Hosmer, _Samuel Adams_.\
\
J.T. Morse, _Benjamin Franklin_.\
\
M.C. Tyler, _Patrick Henry_.\
\
J.A. Woodburn (editor), _The American Revolution_ (Selections from the\
English work by Lecky).\
\
\
=Questions=\
\
1. Show how the character of George III made for trouble with the\
colonies.\
\
2. Explain why the party and parliamentary systems of England favored\
the plans of George III.\
\
3. How did the state of English finances affect English policy?\
\
4. Enumerate five important measures of the English government affecting\
the colonies between 1763 and 1765. Explain each in detail.\
\
5. Describe American resistance to the Stamp Act. What was the outcome?\
\
6. Show how England renewed her policy of regulation in 1767.\
\
7. Summarize the events connected with American resistance.\
\
8. With what measures did Great Britain retaliate?\
\
9. Contrast "constitutional" with "natural" rights.\
\
10. What solution did Burke offer? Why was it rejected?\
\
\
=Research Topics=\
\
=Powers Conferred on Revenue Officers by Writs of Assistance.=--See a\
writ in Macdonald, _Source Book_, p. 109.\
\
=The Acts of Parliament Respecting America.=--Macdonald, pp. 117-146.\
Assign one to each student for report and comment.\
\
=Source Studies on the Stamp Act.=--Hart, _American History Told by\
Contemporaries_, Vol. II, pp. 394-412.\
\
=Source Studies of the Townshend Acts.=--Hart, Vol. II, pp. 413-433.\
\
=American Principles.=--Prepare a table of them from the Resolutions of\
the Stamp Act Congress and the Massachusetts Circular. Macdonald, pp.\
136-146.\
\
=An English Historian's View of the Period.=--Green, _Short History of\
England_, Chap. X.\
\
=English Policy Not Injurious to America.=--Callender, _Economic\
History_, pp. 85-121.\
\
=A Review of English Policy.=--Woodrow Wilson, _History of the American\
People_, Vol. II, pp. 129-170.\
\
=The Opening of the Revolution.=--Elson, _History of the United States_,\
pp. 220-235.\
\
\
\
\
CHAPTER VI\
\
THE AMERICAN REVOLUTION\
\
\
RESISTANCE AND RETALIATION\
\
=The Continental Congress.=--When the news of the "intolerable acts"\
reached America, every one knew what strong medicine Parliament was\
prepared to administer to all those who resisted its authority. The\
cause of Massachusetts became the cause of all the colonies. Opposition\
to British policy, hitherto local and spasmodic, now took on a national\
character. To local committees and provincial conventions was added a\
Continental Congress, appropriately called by Massachusetts on June 17,\
1774, at the instigation of Samuel Adams. The response to the summons\
was electric. By hurried and irregular methods delegates were elected\
during the summer, and on September 5 the Congress duly assembled in\
Carpenter's Hall in Philadelphia. Many of the greatest men in America\
were there--George Washington and Patrick Henry from Virginia and John\
and Samuel Adams from Massachusetts. Every shade of opinion was\
represented. Some were impatient with mild devices; the majority favored\
moderation.\
\
The Congress drew up a declaration of American rights and stated in\
clear and dignified language the grievances of the colonists. It\
approved the resistance to British measures offered by Massachusetts and\
promised the united support of all sections. It prepared an address to\
King George and another to the people of England, disavowing the idea of\
independence but firmly attacking the policies pursued by the British\
government.\
\
=The Non-Importation Agreement.=--The Congress was not content, however,\
with professions of faith and with petitions. It took one revolutionary\
step. It agreed to stop the importation of British goods into America,\
and the enforcement of this agreement it placed in the hands of local\
"committees of safety and inspection," to be elected by the qualified\
voters. The significance of this action is obvious. Congress threw\
itself athwart British law. It made a rule to bind American citizens and\
to be carried into effect by American officers. It set up a state within\
the British state and laid down a test of allegiance to the new order.\
The colonists, who up to this moment had been wavering, had to choose\
one authority or the other. They were for the enforcement of the\
non-importation agreement or they were against it. They either bought\
English goods or they did not. In the spirit of the toast--"May Britain\
be wise and America be free"--the first Continental Congress adjourned\
in October, having appointed the tenth of May following for the meeting\
of a second Congress, should necessity require.\
\
=Lord North's "Olive Branch."=--When the news of the action of the\
American Congress reached England, Pitt and Burke warmly urged a repeal\
of the obnoxious laws, but in vain. All they could wring from the prime\
minister, Lord North, was a set of "conciliatory resolutions" proposing\
to relieve from taxation any colony that would assume its share of\
imperial defense and make provision for supporting the local officers of\
the crown. This "olive branch" was accompanied by a resolution assuring\
the king of support at all hazards in suppressing the rebellion and by\
the restraining act of March 30, 1775, which in effect destroyed the\
commerce of New England.\
\
=Bloodshed at Lexington and Concord (April 19, 1775).=--Meanwhile the\
British authorities in Massachusetts relaxed none of their efforts in\
upholding British sovereignty. General Gage, hearing that military\
stores had been collected at Concord, dispatched a small force to seize\
them. By this act he precipitated the conflict he had sought to avoid.\
At Lexington, on the road to Concord, occurred "the little thing" that\
produced "the great event." An unexpected collision beyond the thought\
or purpose of any man had transferred the contest from the forum to the\
battle field.\
\
=The Second Continental Congress.=--Though blood had been shed and war\
was actually at hand, the second Continental Congress, which met at\
Philadelphia in May, 1775, was not yet convinced that conciliation was\
beyond human power. It petitioned the king to interpose on behalf of the\
colonists in order that the empire might avoid the calamities of civil\
war. On the last day of July, it made a temperate but firm answer to\
Lord North's offer of conciliation, stating that the proposal was\
unsatisfactory because it did not renounce the right to tax or repeal\
the offensive acts of Parliament.\
\
=Force, the British Answer.=--Just as the representatives of America\
were about to present the last petition of Congress to the king on\
August 23, 1775, George III issued a proclamation of rebellion. This\
announcement declared that the colonists, "misled by dangerous and\
ill-designing men," were in a state of insurrection; it called on the\
civil and military powers to bring "the traitors to justice"; and it\
threatened with "condign punishment the authors, perpetrators, and\
abettors of such traitorous designs." It closed with the usual prayer:\
"God, save the king." Later in the year, Parliament passed a sweeping\
act destroying all trade and intercourse with America. Congress was\
silent at last. Force was also America's answer.\
\
\
AMERICAN INDEPENDENCE\
\
=Drifting into War.=--Although the Congress had not given up all hope of\
reconciliation in the spring and summer of 1775, it had firmly resolved\
to defend American rights by arms if necessary. It transformed the\
militiamen who had assembled near Boston, after the battle of Lexington,\
into a Continental army and selected Washington as commander-in-chief.\
It assumed the powers of a government and prepared to raise money, wage\
war, and carry on diplomatic relations with foreign countries.\
\
[Illustration: _From an old print_\
\
SPIRIT OF 1776]\
\
Events followed thick and fast. On June 17, the American militia, by\
the stubborn defense of Bunker Hill, showed that it could make British\
regulars pay dearly for all they got. On July 3, Washington took command\
of the army at Cambridge. In January, 1776, after bitter disappointments\
in drumming up recruits for its army in England, Scotland, and Ireland,\
the British government concluded a treaty with the Landgrave of\
Hesse-Cassel in Germany contracting, at a handsome figure, for thousands\
of soldiers and many pieces of cannon. This was the crowning insult to\
America. Such was the view of all friends of the colonies on both sides\
of the water. Such was, long afterward, the judgment of the conservative\
historian Lecky: "The conduct of England in hiring German mercenaries to\
subdue the essentially English population beyond the Atlantic made\
reconciliation hopeless and independence inevitable." The news of this\
wretched transaction in German soldiers had hardly reached America\
before there ran all down the coast the thrilling story that Washington\
had taken Boston, on March 17, 1776, compelling Lord Howe to sail with\
his entire army for Halifax.\
\
=The Growth of Public Sentiment in Favor of Independence.=--Events were\
bearing the Americans away from their old position under the British\
constitution toward a final separation. Slowly and against their\
desires, prudent and honorable men, who cherished the ties that united\
them to the old order and dreaded with genuine horror all thought of\
revolution, were drawn into the path that led to the great decision. In\
all parts of the country and among all classes, the question of the hour\
was being debated. "American independence," as the historian Bancroft\
says, "was not an act of sudden passion nor the work of one man or one\
assembly. It had been discussed in every part of the country by farmers\
and merchants, by mechanics and planters, by the fishermen along the\
coast and the backwoodsmen of the West; in town meetings and from the\
pulpit; at social gatherings and around the camp fires; in county\
conventions and conferences or committees; in colonial congresses and\
assemblies."\
\
[Illustration: _From an old print_\
\
THOMAS PAINE]\
\
=Paine's "Commonsense."=--In the midst of this ferment of American\
opinion, a bold and eloquent pamphleteer broke in upon the hesitating\
public with a program for absolute independence, without fears and\
without apologies. In the early days of 1776, Thomas Paine issued the\
first of his famous tracts, "Commonsense," a passionate attack upon the\
British monarchy and an equally passionate plea for American liberty.\
Casting aside the language of petition with which Americans had hitherto\
addressed George III, Paine went to the other extreme and assailed him\
with many a violent epithet. He condemned monarchy itself as a system\
which had laid the world "in blood and ashes." Instead of praising the\
British constitution under which colonists had been claiming their\
rights, he brushed it aside as ridiculous, protesting that it was "owing\
to the constitution of the people, not to the constitution of the\
government, that the Crown is not as oppressive in England as in\
Turkey."\
\
Having thus summarily swept away the grounds of allegiance to the old\
order, Paine proceeded relentlessly to an argument for immediate\
separation from Great Britain. There was nothing in the sphere of\
practical interest, he insisted, which should bind the colonies to the\
mother country. Allegiance to her had been responsible for the many wars\
in which they had been involved. Reasons of trade were not less weighty\
in behalf of independence. "Our corn will fetch its price in any market\
in Europe and our imported goods must be paid for, buy them where we\
will." As to matters of government, "it is not in the power of Britain\
to do this continent justice; the business of it will soon be too\
weighty and intricate to be managed with any tolerable degree of\
convenience by a power so distant from us and so very ignorant of us."\
\
There is accordingly no alternative to independence for America.\
"Everything that is right or natural pleads for separation. The blood of\
the slain, the weeping voice of nature cries ''tis time to part.' ...\
Arms, the last resort, must decide the contest; the appeal was the\
choice of the king and the continent hath accepted the challenge.... The\
sun never shone on a cause of greater worth. 'Tis not the affair of a\
city, a county, a province or a kingdom, but of a continent.... 'Tis not\
the concern of a day, a year or an age; posterity is involved in the\
contest and will be more or less affected to the end of time by the\
proceedings now. Now is the seed-time of Continental union, faith, and\
honor.... O! ye that love mankind! Ye that dare oppose not only the\
tyranny, but the tyrant, stand forth.... Let names of Whig and Tory be\
extinct. Let none other be heard among us than those of a good citizen,\
an open and resolute friend, and a virtuous supporter of the rights of\
mankind and of the free and independent states of America." As more than\
100,000 copies were scattered broadcast over the country, patriots\
exclaimed with Washington: "Sound doctrine and unanswerable reason!"\
\
=The Drift of Events toward Independence.=--Official support for the\
idea of independence began to come from many quarters. On the tenth of\
February, 1776, Gadsden, in the provincial convention of South Carolina,\
advocated a new constitution for the colony and absolute independence\
for all America. The convention balked at the latter but went half way\
by abolishing the system of royal administration and establishing a\
complete plan of self-government. A month later, on April 12, the\
neighboring state of North Carolina uttered the daring phrase from which\
others shrank. It empowered its representatives in the Congress to\
concur with the delegates of the other colonies in declaring\
independence. Rhode Island, Massachusetts, and Virginia quickly\
responded to the challenge. The convention of the Old Dominion, on May\
15, instructed its delegates at Philadelphia to propose the independence\
of the United Colonies and to give the assent of Virginia to the act of\
separation. When the resolution was carried the British flag on the\
state house was lowered for all time.\
\
Meanwhile the Continental Congress was alive to the course of events\
outside. The subject of independence was constantly being raised. "Are\
we rebels?" exclaimed Wyeth of Virginia during a debate in February.\
"No: we must declare ourselves a free people." Others hesitated and\
spoke of waiting for the arrival of commissioners of conciliation. "Is\
not America already independent?" asked Samuel Adams a few weeks later.\
"Why not then declare it?" Still there was uncertainty and delegates\
avoided the direct word. A few more weeks elapsed. At last, on May 10,\
Congress declared that the authority of the British crown in America\
must be suppressed and advised the colonies to set up governments of\
their own.\
\
[Illustration: _From an old print_\
\
THOMAS JEFFERSON READING HIS DRAFT OF THE DECLARATION OF\
INDEPENDENCE TO THE COMMITTEE OF CONGRESS]\
\
=Independence Declared.=--The way was fully prepared, therefore, when,\
on June 7, the Virginia delegation in the Congress moved that "these\
united colonies are and of right ought to be free and independent\
states." A committee was immediately appointed to draft a formal\
document setting forth the reasons for the act, and on July 2 all the\
states save New York went on record in favor of severing their political\
connection with Great Britain. Two days later, July 4, Jefferson's draft\
of the Declaration of Independence, changed in some slight particulars,\
was adopted. The old bell in Independence Hall, as it is now known, rang\
out the glad tidings; couriers swiftly carried the news to the uttermost\
hamlet and farm. A new nation announced its will to have a place among\
the powers of the world.\
\
To some documents is given immortality. The Declaration of Independence\
is one of them. American patriotism is forever associated with it; but\
patriotism alone does not make it immortal. Neither does the vigor of\
its language or the severity of its indictment give it a secure place in\
the records of time. The secret of its greatness lies in the simple fact\
that it is one of the memorable landmarks in the history of a political\
ideal which for three centuries has been taking form and spreading\
throughout the earth, challenging kings and potentates, shaking down\
thrones and aristocracies, breaking the armies of irresponsible power on\
battle fields as far apart as Marston Moor and Chateau-Thierry. That\
ideal, now so familiar, then so novel, is summed up in the simple\
sentence: "Governments derive their just powers from the consent of the\
governed."\
\
Written in a "decent respect for the opinions of mankind," to set forth\
the causes which impelled the American colonists to separate from\
Britain, the Declaration contained a long list of "abuses and\
usurpations" which had induced them to throw off the government of King\
George. That section of the Declaration has passed into "ancient"\
history and is seldom read. It is the part laying down a new basis for\
government and giving a new dignity to the common man that has become a\
household phrase in the Old World as in the New.\
\
In the more enduring passages there are four fundamental ideas which,\
from the standpoint of the old system of government, were the essence of\
revolution: (1) all men are created equal and are endowed by their\
Creator with certain unalienable rights including life, liberty, and the\
pursuit of happiness; (2) the purpose of government is to secure these\
rights; (3) governments derive their just powers from the consent of the\
governed; (4) whenever any form of government becomes destructive of\
these ends it is the right of the people to alter or abolish it and\
institute new government, laying its foundations on such principles and\
organizing its powers in such form as to them shall seem most likely to\
effect their safety and happiness. Here was the prelude to the historic\
drama of democracy--a challenge to every form of government and every\
privilege not founded on popular assent.\
\
\
THE ESTABLISHMENT OF GOVERNMENT AND THE NEW ALLEGIANCE\
\
=The Committees of Correspondence.=--As soon as debate had passed into\
armed resistance, the patriots found it necessary to consolidate their\
forces by organizing civil government. This was readily effected, for\
the means were at hand in town meetings, provincial legislatures, and\
committees of correspondence. The working tools of the Revolution were\
in fact the committees of correspondence--small, local, unofficial\
groups of patriots formed to exchange views and create public sentiment.\
As early as November, 1772, such a committee had been created in Boston\
under the leadership of Samuel Adams. It held regular meetings, sent\
emissaries to neighboring towns, and carried on a campaign of education\
in the doctrines of liberty.\
\
[Illustration: THE COLONIES OF NORTH AMERICA AT THE TIME OF THE\
DECLARATION OF INDEPENDENCE]\
\
Upon local organizations similar in character to the Boston committee\
were built county committees and then the larger colonial committees,\
congresses, and conventions, all unofficial and representing the\
revolutionary elements. Ordinarily the provincial convention was merely\
the old legislative assembly freed from all royalist sympathizers and\
controlled by patriots. Finally, upon these colonial assemblies was\
built the Continental Congress, the precursor of union under the\
Articles of Confederation and ultimately under the Constitution of the\
United States. This was the revolutionary government set up within the\
British empire in America.\
\
=State Constitutions Framed.=--With the rise of these new assemblies of\
the people, the old colonial governments broke down. From the royal\
provinces the governor, the judges, and the high officers fled in haste,\
and it became necessary to substitute patriot authorities. The appeal to\
the colonies advising them to adopt a new form of government for\
themselves, issued by the Congress in May, 1776, was quickly acted upon.\
Before the expiration of a year, Virginia, New Jersey, Pennsylvania,\
Delaware, Maryland, Georgia, and New York had drafted new constitutions\
as states, not as colonies uncertain of their destinies. Connecticut and\
Rhode Island, holding that their ancient charters were equal to their\
needs, merely renounced their allegiance to the king and went on as\
before so far as the form of government was concerned. South Carolina,\
which had drafted a temporary plan early in 1776, drew up a new and more\
complete constitution in 1778. Two years later Massachusetts with much\
deliberation put into force its fundamental law, which in most of its\
essential features remains unchanged to-day.\
\
The new state constitutions in their broad outlines followed colonial\
models. For the royal governor was substituted a governor or president\
chosen usually by the legislature; but in two instances, New York and\
Massachusetts, by popular vote. For the provincial council there was\
substituted, except in Georgia, a senate; while the lower house, or\
assembly, was continued virtually without change. The old property\
restriction on the suffrage, though lowered slightly in some states, was\
continued in full force to the great discontent of the mechanics thus\
deprived of the ballot. The special qualifications, laid down in several\
constitutions, for governors, senators, and representatives, indicated\
that the revolutionary leaders were not prepared for any radical\
experiments in democracy. The protests of a few women, like Mrs. John\
Adams of Massachusetts and Mrs. Henry Corbin of Virginia, against a\
government which excluded them from political rights were treated as\
mild curiosities of no significance, although in New Jersey women were\
allowed to vote for many years on the same terms as men.\
\
By the new state constitutions the signs and symbols of royal power, of\
authority derived from any source save "the people," were swept aside\
and republican governments on an imposing scale presented for the first\
time to the modern world. Copies of these remarkable documents prepared\
by plain citizens were translated into French and widely circulated in\
Europe. There they were destined to serve as a guide and inspiration to\
a generation of constitution-makers whose mission it was to begin the\
democratic revolution in the Old World.\
\
=The Articles of Confederation.=--The formation of state constitutions\
was an easy task for the revolutionary leaders. They had only to build\
on foundations already laid. The establishment of a national system of\
government was another matter. There had always been, it must be\
remembered, a system of central control over the colonies, but Americans\
had had little experience in its operation. When the supervision of the\
crown of Great Britain was suddenly broken, the patriot leaders,\
accustomed merely to provincial statesmanship, were poorly trained for\
action on a national stage.\
\
Many forces worked against those who, like Franklin, had a vision of\
national destiny. There were differences in economic interest--commerce\
and industry in the North and the planting system of the South. There\
were contests over the apportionment of taxes and the quotas of troops\
for common defense. To these practical difficulties were added local\
pride, the vested rights of state and village politicians in their\
provincial dignity, and the scarcity of men with a large outlook upon\
the common enterprise.\
\
Nevertheless, necessity compelled them to consider some sort of\
federation. The second Continental Congress had hardly opened its work\
before the most sagacious leaders began to urge the desirability of a\
permanent connection. As early as July, 1775, Congress resolved to go\
into a committee of the whole on the state of the union, and Franklin,\
undaunted by the fate of his Albany plan of twenty years before, again\
presented a draft of a constitution. Long and desultory debates followed\
and it was not until late in 1777 that Congress presented to the states\
the Articles of Confederation. Provincial jealousies delayed\
ratification, and it was the spring of 1781, a few months before the\
surrender of Cornwallis at Yorktown, when Maryland, the last of the\
states, approved the Articles. This plan of union, though it was all\
that could be wrung from the reluctant states, provided for neither a\
chief executive nor a system of federal courts. It created simply a\
Congress of delegates in which each state had an equal voice and gave it\
the right to call upon the state legislatures for the sinews of\
government--money and soldiers.\
\
=The Application of Tests of Allegiance.=--As the successive steps were\
taken in the direction of independent government, the patriots devised\
and applied tests designed to discover who were for and who were against\
the new nation in the process of making. When the first Continental\
Congress agreed not to allow the importation of British goods, it\
provided for the creation of local committees to enforce the rules. Such\
agencies were duly formed by the choice of men favoring the scheme, all\
opponents being excluded from the elections. Before these bodies those\
who persisted in buying British goods were summoned and warned or\
punished according to circumstances. As soon as the new state\
constitutions were put into effect, local committees set to work in the\
same way to ferret out all who were not outspoken in their support of\
the new order of things.\
\
[Illustration: MOBBING THE TORIES]\
\
These patriot agencies, bearing different names in different sections,\
were sometimes ruthless in their methods. They called upon all men to\
sign the test of loyalty, frequently known as the "association test."\
Those who refused were promptly branded as outlaws, while some of the\
more dangerous were thrown into jail. The prison camp in Connecticut at\
one time held the former governor of New Jersey and the mayor of New\
York. Thousands were black-listed and subjected to espionage. The\
black-list of Pennsylvania contained the names of nearly five hundred\
persons of prominence who were under suspicion. Loyalists or Tories who\
were bold enough to speak and write against the Revolution were\
suppressed and their pamphlets burned. In many places, particularly in\
the North, the property of the loyalists was confiscated and the\
proceeds applied to the cause of the Revolution.\
\
The work of the official agencies for suppression of opposition was\
sometimes supplemented by mob violence. A few Tories were hanged without\
trial, and others were tarred and feathered. One was placed upon a cake\
of ice and held there "until his loyalty to King George might cool."\
Whole families were driven out of their homes to find their way as best\
they could within the British lines or into Canada, where the British\
government gave them lands. Such excesses were deplored by Washington,\
but they were defended on the ground that in effect a civil war, as well\
as a war for independence, was being waged.\
\
=The Patriots and Tories.=--Thus, by one process or another, those who\
were to be citizens of the new republic were separated from those who\
preferred to be subjects of King George. Just what proportion of the\
Americans favored independence and what share remained loyal to the\
British monarchy there is no way of knowing. The question of revolution\
was not submitted to popular vote, and on the point of numbers we have\
conflicting evidence. On the patriot side, there is the testimony of a\
careful and informed observer, John Adams, who asserted that two-thirds\
of the people were for the American cause and not more than one-third\
opposed the Revolution at all stages.\
\
On behalf of the loyalists, or Tories as they were popularly known,\
extravagant claims were made. Joseph Galloway, who had been a member of\
the first Continental Congress and had fled to England when he saw its\
temper, testified before a committee of Parliament in 1779 that not\
one-fifth of the American people supported the insurrection and that\
"many more than four-fifths of the people prefer a union with Great\
Britain upon constitutional principles to independence." At the same\
time General Robertson, who had lived in America twenty-four years,\
declared that "more than two-thirds of the people would prefer the\
king's government to the Congress' tyranny." In an address to the king\
in that year a committee of American loyalists asserted that "the number\
of Americans in his Majesty's army exceeded the number of troops\
enlisted by Congress to oppose them."\
\
=The Character of the Loyalists.=--When General Howe evacuated Boston,\
more than a thousand people fled with him. This great company, according\
to a careful historian, "formed the aristocracy of the province by\
virtue of their official rank; of their dignified callings and\
professions; of their hereditary wealth and of their culture." The act\
of banishment passed by Massachusetts in 1778, listing over 300 Tories,\
"reads like the social register of the oldest and noblest families of\
New England," more than one out of five being graduates of Harvard\
College. The same was true of New York and Philadelphia; namely, that\
the leading loyalists were prominent officials of the old order,\
clergymen and wealthy merchants. With passion the loyalists fought\
against the inevitable or with anguish of heart they left as refugees\
for a life of uncertainty in Canada or the mother country.\
\
=Tories Assail the Patriots.=--The Tories who remained in America joined\
the British army by the thousands or in other ways aided the royal\
cause. Those who were skillful with the pen assailed the patriots in\
editorials, rhymes, satires, and political catechisms. They declared\
that the members of Congress were "obscure, pettifogging attorneys,\
bankrupt shopkeepers, outlawed smugglers, etc." The people and their\
leaders they characterized as "wretched banditti ... the refuse and\
dregs of mankind." The generals in the army they sneered at as "men of\
rank and honor nearly on a par with those of the Congress."\
\
=Patriot Writers Arouse the National Spirit.=--Stung by Tory taunts,\
patriot writers devoted themselves to creating and sustaining a public\
opinion favorable to the American cause. Moreover, they had to combat\
the depression that grew out of the misfortunes in the early days of the\
war. A terrible disaster befell Generals Arnold and Montgomery in the\
winter of 1775 as they attempted to bring Canada into the revolution--a\
disaster that cost 5000 men; repeated calamities harassed Washington in\
1776 as he was defeated on Long Island, driven out of New York City, and\
beaten at Harlem Heights and White Plains. These reverses were almost\
too great for the stoutest patriots.\
\
Pamphleteers, preachers, and publicists rose, however, to meet the needs\
of the hour. John Witherspoon, provost of the College of New Jersey,\
forsook the classroom for the field of political controversy. The poet,\
Philip Freneau, flung taunts of cowardice at the Tories and celebrated\
the spirit of liberty in many a stirring poem. Songs, ballads, plays,\
and satires flowed from the press in an unending stream. Fast days,\
battle anniversaries, celebrations of important steps taken by Congress\
afforded to patriotic clergymen abundant opportunities for sermons.\
"Does Mr. Wiberd preach against oppression?" anxiously inquired John\
Adams in a letter to his wife. The answer was decisive. "The clergy of\
every denomination, not excepting the Episcopalian, thunder and lighten\
every Sabbath. They pray for Boston and Massachusetts. They thank God\
most explicitly and fervently for our remarkable successes. They pray\
for the American army."\
\
Thomas Paine never let his pen rest. He had been with the forces of\
Washington when they retreated from Fort Lee and were harried from New\
Jersey into Pennsylvania. He knew the effect of such reverses on the\
army as well as on the public. In December, 1776, he made a second great\
appeal to his countrymen in his pamphlet, "The Crisis," the first part\
of which he had written while defeat and gloom were all about him. This\
tract was a cry for continued support of the Revolution. "These are the\
times that try men's souls," he opened. "The summer soldier and the\
sunshine patriot will, in this crisis, shrink from the service of his\
country; but he that stands it now deserves the love and thanks of men\
and women." Paine laid his lash fiercely on the Tories, branding every\
one as a coward grounded in "servile, slavish, self-interested fear." He\
deplored the inadequacy of the militia and called for a real army. He\
refuted the charge that the retreat through New Jersey was a disaster\
and he promised victory soon. "By perseverance and fortitude," he\
concluded, "we have the prospect of a glorious issue; by cowardice and\
submission the sad choice of a variety of evils--a ravaged country, a\
depopulated city, habitations without safety and slavery without\
hope.... Look on this picture and weep over it." His ringing call to\
arms was followed by another and another until the long contest was\
over.\
\
\
MILITARY AFFAIRS\
\
=The Two Phases of the War.=--The war which opened with the battle of\
Lexington, on April 19, 1775, and closed with the surrender of\
Cornwallis at Yorktown on October 19, 1781, passed through two distinct\
phases--the first lasting until the treaty of alliance with France, in\
1778, and the second until the end of the struggle. During the first\
phase, the war was confined mainly to the North. The outstanding\
features of the contest were the evacuation of Boston by the British,\
the expulsion of American forces from New York and their retreat through\
New Jersey, the battle of Trenton, the seizure of Philadelphia by the\
British (September, 1777), the invasion of New York by Burgoyne and his\
capture at Saratoga in October, 1777, and the encampment of American\
forces at Valley Forge for the terrible winter of 1777-78.\
\
The final phase of the war, opening with the treaty of alliance with\
France on February 6, 1778, was confined mainly to the Middle states,\
the West, and the South. In the first sphere of action the chief events\
were the withdrawal of the British from Philadelphia, the battle of\
Monmouth, and the inclosure of the British in New York by deploying\
American forces from Morristown, New Jersey, up to West Point. In the\
West, George Rogers Clark, by his famous march into the Illinois\
country, secured Kaskaskia and Vincennes and laid a firm grip on the\
country between the Ohio and the Great Lakes. In the South, the second\
period opened with successes for the British. They captured Savannah,\
conquered Georgia, and restored the royal governor. In 1780 they seized\
Charleston, administered a crushing defeat to the American forces under\
Gates at Camden, and overran South Carolina, though meeting reverses at\
Cowpens and King's Mountain. Then came the closing scenes. Cornwallis\
began the last of his operations. He pursued General Greene far into\
North Carolina, clashed with him at Guilford Court House, retired to the\
coast, took charge of British forces engaged in plundering Virginia, and\
fortified Yorktown, where he was penned up by the French fleet from the\
sea and the combined French and American forces on land.\
\
=The Geographical Aspects of the War.=--For the British the theater of\
the war offered many problems. From first to last it extended from\
Massachusetts to Georgia, a distance of almost a thousand miles. It was\
nearly three thousand miles from the main base of supplies and, though\
the British navy kept the channel open, transports were constantly\
falling prey to daring privateers and fleet American war vessels. The\
sea, on the other hand, offered an easy means of transportation between\
points along the coast and gave ready access to the American centers of\
wealth and population. Of this the British made good use. Though early\
forced to give up Boston, they seized New York and kept it until the end\
of the war; they took Philadelphia and retained it until threatened by\
the approach of the French fleet; and they captured and held both\
Savannah and Charleston. Wars, however, are seldom won by the conquest\
of cities.\
\
Particularly was this true in the case of the Revolution. Only a small\
portion of the American people lived in towns. Countrymen back from the\
coast were in no way dependent upon them for a livelihood. They lived on\
the produce of the soil, not upon the profits of trade. This very fact\
gave strength to them in the contest. Whenever the British ventured far\
from the ports of entry, they encountered reverses. Burgoyne was forced\
to surrender at Saratoga because he was surrounded and cut off from his\
base of supplies. As soon as the British got away from Charleston, they\
were harassed and worried by the guerrilla warriors of Marion, Sumter,\
and Pickens. Cornwallis could technically defeat Greene at Guilford far\
in the interior; but he could not hold the inland region he had invaded.\
Sustained by their own labor, possessing the interior to which their\
armies could readily retreat, supplied mainly from native resources, the\
Americans could not be hemmed in, penned up, and destroyed at one fell\
blow.\
\
=The Sea Power.=--The British made good use of their fleet in cutting\
off American trade, but control of the sea did not seriously affect the\
United States. As an agricultural country, the ruin of its commerce was\
not such a vital matter. All the materials for a comfortable though\
somewhat rude life were right at hand. It made little difference to a\
nation fighting for existence, if silks, fine linens, and chinaware were\
cut off. This was an evil to which submission was necessary.\
\
Nor did the brilliant exploits of John Paul Jones and Captain John Barry\
materially change the situation. They demonstrated the skill of American\
seamen and their courage as fighting men. They raised the rates of\
British marine insurance, but they did not dethrone the mistress of the\
seas. Less spectacular, and more distinctive, were the deeds of the\
hundreds of privateers and minor captains who overhauled British supply\
ships and kept British merchantmen in constant anxiety. Not until the\
French fleet was thrown into the scale, were the British compelled to\
reckon seriously with the enemy on the sea and make plans based upon the\
possibilities of a maritime disaster.\
\
=Commanding Officers.=--On the score of military leadership it is\
difficult to compare the contending forces in the revolutionary contest.\
There is no doubt that all the British commanders were men of experience\
in the art of warfare. Sir William Howe had served in America during the\
French War and was accounted an excellent officer, a strict\
disciplinarian, and a gallant gentleman. Nevertheless he loved ease,\
society, and good living, and his expulsion from Boston, his failure to\
overwhelm Washington by sallies from his comfortable bases at New York\
and Philadelphia, destroyed every shred of his military reputation. John\
Burgoyne, to whom was given the task of penetrating New York from\
Canada, had likewise seen service in the French War both in America and\
Europe. He had, however, a touch of the theatrical in his nature and\
after the collapse of his plans and the surrender of his army in 1777,\
he devoted his time mainly to light literature. Sir Henry Clinton, who\
directed the movement which ended in the capture of Charleston in 1780,\
had "learned his trade on the continent," and was regarded as a man of\
discretion and understanding in military matters. Lord Cornwallis, whose\
achievements at Camden and Guilford were blotted out by his surrender at\
Yorktown, had seen service in the Seven Years' War and had undoubted\
talents which he afterward displayed with great credit to himself in\
India. Though none of them, perhaps, were men of first-rate ability,\
they all had training and experience to guide them.\
\
[Illustration: GEORGE WASHINGTON]\
\
The Americans had a host in Washington himself. He had long been\
interested in military strategy and had tested his coolness under fire\
during the first clashes with the French nearly twenty years before. He\
had no doubts about the justice of his cause, such as plagued some of\
the British generals. He was a stern but reasonable disciplinarian. He\
was reserved and patient, little given to exaltation at success or\
depression at reverses. In the dark hour of the Revolution, "what held\
the patriot forces together?" asks Beveridge in his _Life of John\
Marshall_. Then he answers: "George Washington and he alone. Had he\
died or been seriously disabled, the Revolution would have ended....\
Washington was the soul of the American cause. Washington was the\
government. Washington was the Revolution." The weakness of Congress in\
furnishing men and supplies, the indolence of civilians, who lived at\
ease while the army starved, the intrigues of army officers against him\
such as the "Conway cabal," the cowardice of Lee at Monmouth, even the\
treason of Benedict Arnold, while they stirred deep emotions in his\
breast and aroused him to make passionate pleas to his countrymen, did\
not shake his iron will or his firm determination to see the war through\
to the bitter end. The weight of Washington's moral force was\
immeasurable.\
\
Of the generals who served under him, none can really be said to have\
been experienced military men when the war opened. Benedict Arnold, the\
unhappy traitor but brave and daring soldier, was a druggist, book\
seller, and ship owner at New Haven when the news of Lexington called\
him to battle. Horatio Gates was looked upon as a "seasoned soldier"\
because he had entered the British army as a youth, had been wounded at\
Braddock's memorable defeat, and had served with credit during the Seven\
Years' War; but he was the most conspicuous failure of the Revolution.\
The triumph over Burgoyne was the work of other men; and his crushing\
defeat at Camden put an end to his military pretensions. Nathanael\
Greene was a Rhode Island farmer and smith without military experience\
who, when convinced that war was coming, read Caesar's _Commentaries_ and\
took up the sword. Francis Marion was a shy and modest planter of South\
Carolina whose sole passage at arms had been a brief but desperate brush\
with the Indians ten or twelve years earlier. Daniel Morgan, one of the\
heroes of Cowpens, had been a teamster with Braddock's army and had seen\
some fighting during the French and Indian War, but his military\
knowledge, from the point of view of a trained British officer, was\
negligible. John Sullivan was a successful lawyer at Durham, New\
Hampshire, and a major in the local militia when duty summoned him to\
lay down his briefs and take up the sword. Anthony Wayne was a\
Pennsylvania farmer and land surveyor who, on hearing the clash of arms,\
read a few books on war, raised a regiment, and offered himself for\
service. Such is the story of the chief American military leaders, and\
it is typical of them all. Some had seen fighting with the French and\
Indians, but none of them had seen warfare on a large scale with regular\
troops commanded according to the strategy evolved in European\
experience. Courage, native ability, quickness of mind, and knowledge of\
the country they had in abundance, and in battles such as were fought\
during the Revolution all those qualities counted heavily in the\
balance.\
\
=Foreign Officers in American Service.=--To native genius was added\
military talent from beyond the seas. Baron Steuben, well schooled in\
the iron regime of Frederick the Great, came over from Prussia, joined\
Washington at Valley Forge, and day after day drilled and manoeuvered the\
men, laughing and cursing as he turned raw countrymen into regular\
soldiers. From France came young Lafayette and the stern De Kalb, from\
Poland came Pulaski and Kosciusko;--all acquainted with the arts of war\
as waged in Europe and fitted for leadership as well as teaching.\
Lafayette came early, in 1776, in a ship of his own, accompanied by\
several officers of wide experience, and remained loyally throughout the\
war sharing the hardships of American army life. Pulaski fell at the\
siege of Savannah and De Kalb at Camden. Kosciusko survived the American\
war to defend in vain the independence of his native land. To these\
distinguished foreigners, who freely threw in their lot with American\
revolutionary fortunes, was due much of that spirit and discipline which\
fitted raw recruits and temperamental militiamen to cope with a military\
power of the first rank.\
\
=The Soldiers.=--As far as the British soldiers were concerned their\
annals are short and simple. The regulars from the standing army who\
were sent over at the opening of the contest, the recruits drummed up\
by special efforts at home, and the thousands of Hessians bought\
outright by King George presented few problems of management to the\
British officers. These common soldiers were far away from home and\
enlisted for the war. Nearly all of them were well disciplined and many\
of them experienced in actual campaigns. The armies of King George\
fought bravely, as the records of Bunker Hill, Brandywine, and Monmouth\
demonstrate. Many a man and subordinate officer and, for that matter,\
some of the high officers expressed a reluctance at fighting against\
their own kin; but they obeyed orders.\
\
The Americans, on the other hand, while they fought with grim\
determination, as men fighting for their homes, were lacking in\
discipline and in the experience of regular troops. When the war broke\
in upon them, there were no common preparations for it. There was no\
continental army; there were only local bands of militiamen, many of\
them experienced in fighting but few of them "regulars" in the military\
sense. Moreover they were volunteers serving for a short time,\
unaccustomed to severe discipline, and impatient at the restraints\
imposed on them by long and arduous campaigns. They were continually\
leaving the service just at the most critical moments. "The militia,"\
lamented Washington, "come in, you cannot tell how; go, you cannot tell\
where; consume your provisions; exhaust your stores; and leave you at\
last at a critical moment."\
\
Again and again Washington begged Congress to provide for an army of\
regulars enlisted for the war, thoroughly trained and paid according to\
some definite plan. At last he was able to overcome, in part at least,\
the chronic fear of civilians in Congress and to wring from that\
reluctant body an agreement to grant half pay to all officers and a\
bonus to all privates who served until the end of the war. Even this\
scheme, which Washington regarded as far short of justice to the\
soldiers, did not produce quick results. It was near the close of the\
conflict before he had an army of well-disciplined veterans capable of\
meeting British regulars on equal terms.\
\
Though there were times when militiamen and frontiersmen did valiant and\
effective work, it is due to historical accuracy to deny the\
time-honored tradition that a few minutemen overwhelmed more numerous\
forces of regulars in a seven years' war for independence. They did\
nothing of the sort. For the victories of Bennington, Trenton, Saratoga,\
and Yorktown there were the defeats of Bunker Hill, Long Island, White\
Plains, Germantown, and Camden. Not once did an army of militiamen\
overcome an equal number of British regulars in an open trial by battle.\
"To bring men to be well acquainted with the duties of a soldier," wrote\
Washington, "requires time.... To expect the same service from raw and\
undisciplined recruits as from veteran soldiers is to expect what never\
did and perhaps never will happen."\
\
=How the War Was Won.=--Then how did the American army win the war? For\
one thing there were delays and blunders on the part of the British\
generals who, in 1775 and 1776, dallied in Boston and New York with\
large bodies of regular troops when they might have been dealing\
paralyzing blows at the scattered bands that constituted the American\
army. "Nothing but the supineness or folly of the enemy could have saved\
us," solemnly averred Washington in 1780. Still it is fair to say that\
this apparent supineness was not all due to the British generals. The\
ministers behind them believed that a large part of the colonists were\
loyal and that compromise would be promoted by inaction rather than by a\
war vigorously prosecuted. Victory by masterly inactivity was obviously\
better than conquest, and the slighter the wounds the quicker the\
healing. Later in the conflict when the seasoned forces of France were\
thrown into the scale, the Americans themselves had learned many things\
about the practical conduct of campaigns. All along, the British were\
embarrassed by the problem of supplies. Their troops could not forage\
with the skill of militiamen, as they were in unfamiliar territory. The\
long oversea voyages were uncertain at best and doubly so when the\
warships of France joined the American privateers in preying on supply\
boats.\
\
The British were in fact battered and worn down by a guerrilla war and\
outdone on two important occasions by superior forces--at Saratoga and\
Yorktown. Stern facts convinced them finally that an immense army, which\
could be raised only by a supreme effort, would be necessary to subdue\
the colonies if that hazardous enterprise could be accomplished at all.\
They learned also that America would then be alienated, fretful, and the\
scene of endless uprisings calling for an army of occupation. That was a\
price which staggered even Lord North and George III. Moreover, there\
were forces of opposition at home with which they had to reckon.\
\
=Women and the War.=--At no time were the women of America indifferent\
to the struggle for independence. When it was confined to the realm of\
opinion they did their part in creating public sentiment. Mrs. Elizabeth\
Timothee, for example, founded in Charleston, in 1773, a newspaper to\
espouse the cause of the province. Far to the north the sister of James\
Otis, Mrs. Mercy Warren, early begged her countrymen to rest their case\
upon their natural rights, and in influential circles she urged the\
leaders to stand fast by their principles. While John Adams was tossing\
about with uncertainty at the Continental Congress, his wife was writing\
letters to him declaring her faith in "independency."\
\
When the war came down upon the country, women helped in every field. In\
sustaining public sentiment they were active. Mrs. Warren with a\
tireless pen combatted loyalist propaganda in many a drama and satire.\
Almost every revolutionary leader had a wife or daughter who rendered\
service in the "second line of defense." Mrs. Washington managed the\
plantation while the General was at the front and went north to face the\
rigors of the awful winter at Valley Forge--an inspiration to her\
husband and his men. The daughter of Benjamin Franklin, Mrs. Sarah\
Bache, while her father was pleading the American cause in France, set\
the women of Pennsylvania to work sewing and collecting supplies. Even\
near the firing line women were to be found, aiding the wounded, hauling\
powder to the front, and carrying dispatches at the peril of their\
lives.\
\
In the economic sphere, the work of women was invaluable. They harvested\
crops without enjoying the picturesque title of "farmerettes" and they\
canned and preserved for the wounded and the prisoners of war. Of their\
labor in spinning and weaving it is recorded: "Immediately on being cut\
off from the use of English manufactures, the women engaged within their\
own families in manufacturing various kinds of cloth for domestic use.\
They thus kept their households decently clad and the surplus of their\
labors they sold to such as chose to buy rather than make for\
themselves. In this way the female part of families by their industry\
and strict economy frequently supported the whole domestic circle,\
evincing the strength of their attachment and the value of their\
service."\
\
For their war work, women were commended by high authorities on more\
than one occasion. They were given medals and public testimonials even\
as in our own day. Washington thanked them for their labors and paid\
tribute to them for the inspiration and material aid which they had\
given to the cause of independence.\
\
\
THE FINANCES OF THE REVOLUTION\
\
When the Revolution opened, there were thirteen little treasuries in\
America but no common treasury, and from first to last the Congress was\
in the position of a beggar rather than a sovereign. Having no authority\
to lay and collect taxes directly and knowing the hatred of the\
provincials for taxation, it resorted mainly to loans and paper money to\
finance the war. "Do you think," boldly inquired one of the delegates,\
"that I will consent to load my constituents with taxes when we can send\
to the printer and get a wagon load of money, one quire of which will\
pay for the whole?"\
\
=Paper Money and Loans.=--Acting on this curious but appealing political\
economy, Congress issued in June, 1776, two million dollars in bills of\
credit to be redeemed by the states on the basis of their respective\
populations. Other issues followed in quick succession. In all about\
$241,000,000 of continental paper was printed, to which the several\
states added nearly $210,000,000 of their own notes. Then came\
interest-bearing bonds in ever increasing quantities. Several millions\
were also borrowed from France and small sums from Holland and Spain. In\
desperation a national lottery was held, producing meager results. The\
property of Tories was confiscated and sold, bringing in about\
$16,000,000. Begging letters were sent to the states asking them to\
raise revenues for the continental treasury, but the states, burdened\
with their own affairs, gave little heed.\
\
=Inflation and Depreciation.=--As paper money flowed from the press, it\
rapidly declined in purchasing power until in 1779 a dollar was worth\
only two or three cents in gold or silver. Attempts were made by\
Congress and the states to compel people to accept the notes at face\
value; but these were like attempts to make water flow uphill.\
Speculators collected at once to fatten on the calamities of the\
republic. Fortunes were made and lost gambling on the prices of public\
securities while the patriot army, half clothed, was freezing at Valley\
Forge. "Speculation, peculation, engrossing, forestalling," exclaimed\
Washington, "afford too many melancholy proofs of the decay of public\
virtue. Nothing, I am convinced, but the depreciation of our currency\
... aided by stock jobbing and party dissensions has fed the hopes of\
the enemy."\
\
=The Patriot Financiers.=--To the efforts of Congress in financing the\
war were added the labors of private citizens. Hayn Solomon, a merchant\
of Philadelphia, supplied members of Congress, including Madison,\
Jefferson, and Monroe, and army officers, like Lee and Steuben, with\
money for their daily needs. All together he contributed the huge sum of\
half a million dollars to the American cause and died broken in purse,\
if not in spirit, a British prisoner of war. Another Philadelphia\
merchant, Robert Morris, won for himself the name of the "patriot\
financier" because he labored night and day to find the money to meet\
the bills which poured in upon the bankrupt government. When his own\
funds were exhausted, he borrowed from his friends. Experienced in the\
handling of merchandise, he created agencies at important points to\
distribute supplies to the troops, thus displaying administrative as\
well as financial talents.\
\
[Illustration: ROBERT MORRIS]\
\
Women organized "drives" for money, contributed their plate and their\
jewels, and collected from door to door. Farmers took worthless paper in\
return for their produce, and soldiers saw many a pay day pass without\
yielding them a penny. Thus by the labors and sacrifices of citizens,\
the issuance of paper money, lotteries, the floating of loans,\
borrowings in Europe, and the impressment of supplies, the Congress\
staggered through the Revolution like a pauper who knows not how his\
next meal is to be secured but is continuously relieved at a crisis by a\
kindly fate.\
\
\
THE DIPLOMACY OF THE REVOLUTION\
\
When the full measure of honor is given to the soldiers and sailors and\
their commanding officers, the civilians who managed finances and\
supplies, the writers who sustained the American spirit, and the women\
who did well their part, there yet remains the duty of recognizing the\
achievements of diplomacy. The importance of this field of activity was\
keenly appreciated by the leaders in the Continental Congress. They were\
fairly well versed in European history. They knew of the balance of\
power and the sympathies, interests, and prejudices of nations and their\
rulers. All this information they turned to good account, in opening\
relations with continental countries and seeking money, supplies, and\
even military assistance. For the transaction of this delicate business,\
they created a secret committee on foreign correspondence as early as\
1775 and prepared to send agents abroad.\
\
=American Agents Sent Abroad.=--Having heard that France was inclining a\
friendly ear to the American cause, the Congress, in March, 1776, sent a\
commissioner to Paris, Silas Deane of Connecticut, often styled the\
"first American diplomat." Later in the year a form of treaty to be\
presented to foreign powers was drawn up, and Franklin, Arthur Lee, and\
Deane were selected as American representatives at the court of "His\
Most Christian Majesty the King of France." John Jay of New York was\
chosen minister to Spain in 1779; John Adams was sent to Holland the\
same year; and other agents were dispatched to Florence, Vienna, and\
Berlin. The representative selected for St. Petersburg spent two\
fruitless years there, "ignored by the court, living in obscurity and\
experiencing nothing but humiliation and failure." Frederick the Great,\
king of Prussia, expressed a desire to find in America a market for\
Silesian linens and woolens, but, fearing England's command of the sea,\
he refused to give direct aid to the Revolutionary cause.\
\
=Early French Interest.=--The great diplomatic triumph of the Revolution\
was won at Paris, and Benjamin Franklin was the hero of the occasion,\
although many circumstances prepared the way for his success. Louis\
XVI's foreign minister, Count de Vergennes, before the arrival of any\
American representative, had brought to the attention of the king the\
opportunity offered by the outbreak of the war between England and her\
colonies. He showed him how France could redress her grievances and\
"reduce the power and greatness of England"--the empire that in 1763 had\
forced upon her a humiliating peace "at the price of our possessions,\
of our commerce, and our credit in the Indies, at the price of Canada,\
Louisiana, Isle Royale, Acadia, and Senegal." Equally successful in\
gaining the king's interest was a curious French adventurer,\
Beaumarchais, a man of wealth, a lover of music, and the author of two\
popular plays, "Figaro" and "The Barber of Seville." These two men had\
already urged upon the king secret aid for America before Deane appeared\
on the scene. Shortly after his arrival they made confidential\
arrangements to furnish money, clothing, powder, and other supplies to\
the struggling colonies, although official requests for them were\
officially refused by the French government.\
\
=Franklin at Paris.=--When Franklin reached Paris, he was received only\
in private by the king's minister, Vergennes. The French people,\
however, made manifest their affection for the "plain republican" in\
"his full dress suit of spotted Manchester velvet." He was known among\
men of letters as an author, a scientist, and a philosopher of\
extraordinary ability. His "Poor Richard" had thrice been translated\
into French and was scattered in numerous editions throughout the\
kingdom. People of all ranks--ministers, ladies at court, philosophers,\
peasants, and stable boys--knew of Franklin and wished him success in\
his mission. The queen, Marie Antoinette, fated to lose her head in a\
revolution soon to follow, played with fire by encouraging "our dear\
republican."\
\
For the king of France, however, this was more serious business. England\
resented the presence of this "traitor" in Paris, and Louis had to be\
cautious about plunging into another war that might also end\
disastrously. Moreover, the early period of Franklin's sojourn in Paris\
was a dark hour for the American Revolution. Washington's brilliant\
exploit at Trenton on Christmas night, 1776, and the battle with\
Cornwallis at Princeton had been followed by the disaster at Brandywine,\
the loss of Philadelphia, the defeat at Germantown, and the retirement\
to Valley Forge for the winter of 1777-78. New York City and\
Philadelphia--two strategic ports--were in British hands; the Hudson\
and Delaware rivers were blocked; and General Burgoyne with his British\
troops was on his way down through the heart of northern New York,\
cutting New England off from the rest of the colonies. No wonder the\
king was cautious. Then the unexpected happened. Burgoyne, hemmed in\
from all sides by the American forces, his flanks harried, his foraging\
parties beaten back, his supplies cut off, surrendered on October 17,\
1777, to General Gates, who had superseded General Schuyler in time to\
receive the honor.\
\
=Treaties of Alliance and Commerce (1778).=--News of this victory,\
placed by historians among the fifteen decisive battles of the world,\
reached Franklin one night early in December while he and some friends\
sat gloomily at dinner. Beaumarchais, who was with him, grasped at once\
the meaning of the situation and set off to the court at Versailles with\
such haste that he upset his coach and dislocated his arm. The king and\
his ministers were at last convinced that the hour had come to aid the\
Revolution. Treaties of commerce and alliance were drawn up and signed\
in February, 1778. The independence of the United States was recognized\
by France and an alliance was formed to guarantee that independence.\
Combined military action was agreed upon and Louis then formally\
declared war on England. Men who had, a few short years before, fought\
one another in the wilderness of Pennsylvania or on the Plains of\
Abraham, were now ranged side by side in a war on the Empire that Pitt\
had erected and that George III was pulling down.\
\
=Spain and Holland Involved.=--Within a few months, Spain, remembering\
the steady decline of her sea power since the days of the Armada and\
hoping to drive the British out of Gibraltar, once more joined the\
concert of nations against England. Holland, a member of a league of\
armed neutrals formed in protest against British searches on the high\
seas, sent her fleet to unite with the forces of Spain, France, and\
America to prey upon British commerce. To all this trouble for England\
was added the danger of a possible revolt in Ireland, where the spirit\
of independence was flaming up.\
\
=The British Offer Terms to America.=--Seeing the colonists about to be\
joined by France in a common war on the English empire, Lord North\
proposed, in February, 1778, a renewal of negotiations. By solemn\
enactment, Parliament declared its intention not to exercise the right\
of imposing taxes within the colonies; at the same time it authorized\
the opening of negotiations through commissioners to be sent to America.\
A truce was to be established, pardons granted, objectionable laws\
suspended, and the old imperial constitution, as it stood before the\
opening of hostilities, restored to full vigor. It was too late. Events\
had taken the affairs of America out of the hands of British\
commissioners and diplomats.\
\
=Effects of French Aid.=--The French alliance brought ships of war,\
large sums of gold and silver, loads of supplies, and a considerable\
body of trained soldiers to the aid of the Americans. Timely as was this\
help, it meant no sudden change in the fortunes of war. The British\
evacuated Philadelphia in the summer following the alliance, and\
Washington's troops were encouraged to come out of Valley Forge. They\
inflicted a heavy blow on the British at Monmouth, but the treasonable\
conduct of General Charles Lee prevented a triumph. The recovery of\
Philadelphia was offset by the treason of Benedict Arnold, the loss of\
Savannah and Charleston (1780), and the defeat of Gates at Camden.\
\
The full effect of the French alliance was not felt until 1781, when\
Cornwallis went into Virginia and settled at Yorktown. Accompanied by\
French troops Washington swept rapidly southward and penned the British\
to the shore while a powerful French fleet shut off their escape by sea.\
It was this movement, which certainly could not have been executed\
without French aid, that put an end to all chance of restoring British\
dominion in America. It was the surrender of Cornwallis at Yorktown that\
caused Lord North to pace the floor and cry out: "It is all over! It is\
all over!" What might have been done without the French alliance lies\
hidden from mankind. What was accomplished with the help of French\
soldiers, sailors, officers, money, and supplies, is known to all the\
earth. "All the world agree," exultantly wrote Franklin from Paris to\
General Washington, "that no expedition was ever better planned or\
better executed. It brightens the glory that must accompany your name to\
the latest posterity." Diplomacy as well as martial valor had its\
reward.\
\
\
PEACE AT LAST\
\
=British Opposition to the War.=--In measuring the forces that led to\
the final discomfiture of King George and Lord North, it is necessary to\
remember that from the beginning to the end the British ministry at home\
faced a powerful, informed, and relentless opposition. There were\
vigorous protests, first against the obnoxious acts which precipitated\
the unhappy quarrel, then against the way in which the war was waged,\
and finally against the futile struggle to retain a hold upon the\
American dominions. Among the members of Parliament who thundered\
against the government were the first statesmen and orators of the land.\
William Pitt, Earl of Chatham, though he deplored the idea of American\
independence, denounced the government as the aggressor and rejoiced in\
American resistance. Edmund Burke leveled his heavy batteries against\
every measure of coercion and at last strove for a peace which, while\
giving independence to America, would work for reconciliation rather\
than estrangement. Charles James Fox gave the colonies his generous\
sympathy and warmly championed their rights. Outside of the circle of\
statesmen there were stout friends of the American cause like David\
Hume, the philosopher and historian, and Catherine Macaulay, an author\
of wide fame and a republican bold enough to encourage Washington in\
seeing it through.\
\
Against this powerful opposition, the government enlisted a whole army\
of scribes and journalists to pour out criticism on the Americans and\
their friends. Dr. Samuel Johnson, whom it employed in this business,\
was so savage that even the ministers had to tone down his pamphlets\
before printing them. Far more weighty was Edward Gibbon, who was in\
time to win fame as the historian of the _Decline and Fall of the Roman\
Empire_. He had at first opposed the government; but, on being given a\
lucrative post, he used his sharp pen in its support, causing his\
friends to ridicule him in these lines:\
\
    "King George, in a fright\
     Lest Gibbon should write\
       The story of England's disgrace,\
     Thought no way so sure\
     His pen to secure\
       As to give the historian a place."\
\
=Lord North Yields.=--As time wore on, events bore heavily on the side\
of the opponents of the government's measures. They had predicted that\
conquest was impossible, and they had urged the advantages of a peace\
which would in some measure restore the affections of the Americans.\
Every day's news confirmed their predictions and lent support to their\
arguments. Moreover, the war, which sprang out of an effort to relieve\
English burdens, made those burdens heavier than ever. Military expenses\
were daily increasing. Trade with the colonies, the greatest single\
outlet for British goods and capital, was paralyzed. The heavy debts due\
British merchants in America were not only unpaid but postponed into an\
indefinite future. Ireland was on the verge of revolution. The French\
had a dangerous fleet on the high seas. In vain did the king assert in\
December, 1781, that no difficulties would ever make him consent to a\
peace that meant American independence. Parliament knew better, and on\
February 27, 1782, in the House of Commons was carried an address to the\
throne against continuing the war. Burke, Fox, the younger Pitt, Barre,\
and other friends of the colonies voted in the affirmative. Lord North\
gave notice then that his ministry was at an end. The king moaned:\
"Necessity made me yield."\
\
In April, 1782, Franklin received word from the English government that\
it was prepared to enter into negotiations leading to a settlement. This\
was embarrassing. In the treaty of alliance with France, the United\
States had promised that peace should be a joint affair agreed to by\
both nations in open conference. Finding France, however, opposed to\
some of their claims respecting boundaries and fisheries, the American\
commissioners conferred with the British agents at Paris without\
consulting the French minister. They actually signed a preliminary peace\
draft before they informed him of their operations. When Vergennes\
reproached him, Franklin replied that they "had been guilty of\
neglecting _bienseance_ [good manners] but hoped that the great work\
would not be ruined by a single indiscretion."\
\
=The Terms of Peace (1783).=--The general settlement at Paris in 1783\
was a triumph for America. England recognized the independence of the\
United States, naming each state specifically, and agreed to boundaries\
extending from the Atlantic to the Mississippi and from the Great Lakes\
to the Floridas. England held Canada, Newfoundland, and the West Indies\
intact, made gains in India, and maintained her supremacy on the seas.\
Spain won Florida and Minorca but not the coveted Gibraltar. France\
gained nothing important save the satisfaction of seeing England humbled\
and the colonies independent.\
\
The generous terms secured by the American commission at Paris called\
forth surprise and gratitude in the United States and smoothed the way\
for a renewal of commercial relations with the mother country. At the\
same time they gave genuine anxiety to European diplomats. "This federal\
republic is born a pigmy," wrote the Spanish ambassador to his royal\
master. "A day will come when it will be a giant; even a colossus\
formidable to these countries. Liberty of conscience and the facility\
for establishing a new population on immense lands, as well as the\
advantages of the new government, will draw thither farmers and artisans\
from all the nations. In a few years we shall watch with grief the\
tyrannical existence of the same colossus."\
\
[Illustration: NORTH AMERICA ACCORDING TO THE TREATY OF 1783]\
\
\
SUMMARY OF THE REVOLUTIONARY PERIOD\
\
The independence of the American colonies was foreseen by many European\
statesmen as they watched the growth of their population, wealth, and\
power; but no one could fix the hour of the great event. Until 1763 the\
American colonists lived fairly happily under British dominion. There\
were collisions from time to time, of course. Royal governors clashed\
with stiff-necked colonial legislatures. There were protests against the\
exercise of the king's veto power in specific cases. Nevertheless, on\
the whole, the relations between America and the mother country were\
more amicable in 1763 than at any period under the Stuart regime which\
closed in 1688.\
\
The crash, when it came, was not deliberately willed by any one. It was\
the product of a number of forces that happened to converge about 1763.\
Three years before, there had come to the throne George III, a young,\
proud, inexperienced, and stubborn king. For nearly fifty years his\
predecessors, Germans as they were in language and interest, had allowed\
things to drift in England and America. George III decided that he would\
be king in fact as well as in name. About the same time England brought\
to a close the long and costly French and Indian War and was staggering\
under a heavy burden of debt and taxes. The war had been fought partly\
in defense of the American colonies and nothing seemed more reasonable\
to English statesmen than the idea that the colonies should bear part of\
the cost of their own defense. At this juncture there came into\
prominence, in royal councils, two men bent on taxing America and\
controlling her trade, Grenville and Townshend. The king was willing,\
the English taxpayers were thankful for any promise of relief, and\
statesmen were found to undertake the experiment. England therefore set\
out upon a new course. She imposed taxes upon the colonists, regulated\
their trade and set royal officers upon them to enforce the law. This\
action evoked protests from the colonists. They held a Stamp Act\
Congress to declare their rights and petition for a redress of\
grievances. Some of the more restless spirits rioted in the streets,\
sacked the houses of the king's officers, and tore up the stamped paper.\
\
Frightened by uprising, the English government drew back and repealed\
the Stamp Act. Then it veered again and renewed its policy of\
interference. Interference again called forth American protests.\
Protests aroused sharper retaliation. More British regulars were sent\
over to keep order. More irritating laws were passed by Parliament.\
Rioting again appeared: tea was dumped in the harbor of Boston and\
seized in the harbor of Charleston. The British answer was more force.\
The response of the colonists was a Continental Congress for defense. An\
unexpected and unintended clash of arms at Lexington and Concord in the\
spring of 1775 brought forth from the king of England a proclamation:\
"The Americans are rebels!"\
\
The die was cast. The American Revolution had begun. Washington was made\
commander-in-chief. Armies were raised, money was borrowed, a huge\
volume of paper currency was issued, and foreign aid was summoned.\
Franklin plied his diplomatic arts at Paris until in 1778 he induced\
France to throw her sword into the balance. Three years later,\
Cornwallis surrendered at Yorktown. In 1783, by the formal treaty of\
peace, George III acknowledged the independence of the United States.\
The new nation, endowed with an imperial domain stretching from the\
Atlantic Ocean to the Mississippi River, began its career among the\
sovereign powers of the earth.\
\
In the sphere of civil government, the results of the Revolution were\
equally remarkable. Royal officers and royal authorities were driven\
from the former dominions. All power was declared to be in the people.\
All the colonies became states, each with its own constitution or plan\
of government. The thirteen states were united in common bonds under the\
Articles of Confederation. A republic on a large scale was instituted.\
Thus there was begun an adventure in popular government such as the\
world had never seen. Could it succeed or was it destined to break down\
and be supplanted by a monarchy? The fate of whole continents hung upon\
the answer.\
\
\
=References=\
\
J. Fiske, _The American Revolution_ (2 vols.).\
\
H. Lodge, _Life of Washington_ (2 vols.).\
\
W. Sumner, _The Financier and the Finances of the American Revolution_.\
\
O. Trevelyan, _The American Revolution_ (4 vols.). A sympathetic account\
by an English historian.\
\
M.C. Tyler, _Literary History of the American Revolution_ (2 vols.).\
\
C.H. Van Tyne, _The American Revolution_ (American Nation Series) and\
_The Loyalists in the American Revolution_.\
\
\
=Questions=\
\
1. What was the non-importation agreement? By what body was it adopted?\
Why was it revolutionary in character?\
\
2. Contrast the work of the first and second Continental Congresses.\
\
3. Why did efforts at conciliation fail?\
\
4. Trace the growth of American independence from opinion to the sphere\
of action.\
\
5. Why is the Declaration of Independence an "immortal" document?\
\
6. What was the effect of the Revolution on colonial governments? On\
national union?\
\
7. Describe the contest between "Patriots" and "Tories."\
\
8. What topics are considered under "military affairs"? Discuss each in\
detail.\
\
9. Contrast the American forces with the British forces and show how the\
war was won.\
\
10. Compare the work of women in the Revolutionary War with their labors\
in the World War (1917-18).\
\
11. How was the Revolution financed?\
\
12. Why is diplomacy important in war? Describe the diplomatic triumph\
of the Revolution.\
\
13. What was the nature of the opposition in England to the war?\
\
14. Give the events connected with the peace settlement; the terms of\
peace.\
\
\
=Research Topics=\
\
=The Spirit of America.=--Woodrow Wilson, _History of the American\
People_, Vol. II, pp. 98-126.\
\
=American Rights.=--Draw up a table showing all the principles laid down\
by American leaders in (1) the Resolves of the First Continental\
Congress, Macdonald, _Documentary Source Book_, pp. 162-166; (2) the\
Declaration of the Causes and the Necessity of Taking Up Arms,\
Macdonald, pp. 176-183; and (3) the Declaration of Independence.\
\
=The Declaration of Independence.=--Fiske, _The American Revolution_,\
Vol. I, pp. 147-197. Elson, _History of the United States_, pp. 250-254.\
\
=Diplomacy and the French Alliance.=--Hart, _American History Told by\
Contemporaries_, Vol. II, pp. 574-590. Fiske, Vol. II, pp. 1-24.\
Callender, _Economic History of the United States_, pp. 159-168; Elson,\
pp. 275-280.\
\
=Biographical Studies.=--Washington, Franklin, Samuel Adams, Patrick\
Henry, Thomas Jefferson--emphasizing the peculiar services of each.\
\
=The Tories.=--Hart, _Contemporaries_, Vol. II, pp. 470-480.\
\
=Valley Forge.=--Fiske, Vol. II, pp. 25-49.\
\
=The Battles of the Revolution.=--Elson, pp. 235-317.\
\
=An English View of the Revolution.=--Green, _Short History of England_,\
Chap. X, Sect. 2.\
\
=English Opinion and the Revolution.=--Trevelyan, _The American\
Revolution_, Vol. III (or Part 2, Vol. II), Chaps. XXIV-XXVII.\
\
\
\
\
PART III. THE UNION AND NATIONAL POLITICS\
\
\
\
\
CHAPTER VII\
\
THE FORMATION OF THE CONSTITUTION\
\
\
THE PROMISE AND THE DIFFICULTIES OF AMERICA\
\
The rise of a young republic composed of thirteen states, each governed\
by officials popularly elected under constitutions drafted by "the plain\
people," was the most significant feature of the eighteenth century. The\
majority of the patriots whose labors and sacrifices had made this\
possible naturally looked upon their work and pronounced it good. Those\
Americans, however, who peered beneath the surface of things, saw that\
the Declaration of Independence, even if splendidly phrased, and paper\
constitutions, drawn by finest enthusiasm "uninstructed by experience,"\
could not alone make the republic great and prosperous or even free. All\
around them they saw chaos in finance and in industry and perils for the\
immediate future.\
\
=The Weakness of the Articles of Confederation.=--The government under\
the Articles of Confederation had neither the strength nor the resources\
necessary to cope with the problems of reconstruction left by the war.\
The sole organ of government was a Congress composed of from two to\
seven members from each state chosen as the legislature might direct and\
paid by the state. In determining all questions, each state had one\
vote--Delaware thus enjoying the same weight as Virginia. There was no\
president to enforce the laws. Congress was given power to select a\
committee of thirteen--one from each state--to act as an executive body\
when it was not in session; but this device, on being tried out, proved\
a failure. There was no system of national courts to which citizens and\
states could appeal for the protection of their rights or through which\
they could compel obedience to law. The two great powers of government,\
military and financial, were withheld. Congress, it is true, could\
authorize expenditures but had to rely upon the states for the payment\
of contributions to meet its bills. It could also order the\
establishment of an army, but it could only request the states to supply\
their respective quotas of soldiers. It could not lay taxes nor bring\
any pressure to bear upon a single citizen in the whole country. It\
could act only through the medium of the state governments.\
\
=Financial and Commercial Disorders.=--In the field of public finance,\
the disorders were pronounced. The huge debt incurred during the war was\
still outstanding. Congress was unable to pay either the interest or the\
principal. Public creditors were in despair, as the market value of\
their bonds sank to twenty-five or even ten cents on the dollar. The\
current bills of Congress were unpaid. As some one complained, there was\
not enough money in the treasury to buy pen and ink with which to record\
the transactions of the shadow legislature. The currency was in utter\
chaos. Millions of dollars in notes issued by Congress had become mere\
trash worth a cent or two on the dollar. There was no other expression\
of contempt so forceful as the popular saying: "not worth a\
Continental." To make matters worse, several of the states were pouring\
new streams of paper money from the press. Almost the only good money in\
circulation consisted of English, French, and Spanish coins, and the\
public was even defrauded by them because money changers were busy\
clipping and filing away the metal. Foreign commerce was unsettled. The\
entire British system of trade discrimination was turned against the\
Americans, and Congress, having no power to regulate foreign commerce,\
was unable to retaliate or to negotiate treaties which it could enforce.\
Domestic commerce was impeded by the jealousies of the states, which\
erected tariff barriers against their neighbors. The condition of the\
currency made the exchange of money and goods extremely difficult, and,\
as if to increase the confusion, backward states enacted laws hindering\
the prompt collection of debts within their borders--an evil which\
nothing but a national system of courts could cure.\
\
=Congress in Disrepute.=--With treaties set at naught by the states, the\
laws unenforced, the treasury empty, and the public credit gone, the\
Congress of the United States fell into utter disrepute. It called upon\
the states to pay their quotas of money into the treasury, only to be\
treated with contempt. Even its own members looked upon it as a solemn\
futility. Some of the ablest men refused to accept election to it, and\
many who did take the doubtful honor failed to attend the sessions.\
Again and again it was impossible to secure a quorum for the transaction\
of business.\
\
=Troubles of the State Governments.=--The state governments, free to\
pursue their own course with no interference from without, had almost as\
many difficulties as the Congress. They too were loaded with\
revolutionary debts calling for heavy taxes upon an already restive\
population. Oppressed by their financial burdens and discouraged by the\
fall in prices which followed the return of peace, the farmers of\
several states joined in a concerted effort and compelled their\
legislatures to issue large sums of paper money. The currency fell in\
value, but nevertheless it was forced on unwilling creditors to square\
old accounts.\
\
In every part of the country legislative action fluctuated violently.\
Laws were made one year only to be repealed the next and reenacted the\
third year. Lands were sold by one legislature and the sales were\
canceled by its successor. Uncertainty and distrust were the natural\
consequences. Men of substance longed for some power that would forbid\
states to issue bills of credit, to make paper money legal tender in\
payment of debts, or to impair the obligation of contracts. Men heavily\
in debt, on the other hand, urged even more drastic action against\
creditors.\
\
So great did the discontent of the farmers in New Hampshire become in\
1786 that a mob surrounded the legislature, demanding a repeal of the\
taxes and the issuance of paper money. It was with difficulty that an\
armed rebellion was avoided. In Massachusetts the malcontents, under the\
leadership of Daniel Shays, a captain in the Revolutionary army,\
organized that same year open resistance to the government of the state.\
Shays and his followers protested against the conduct of creditors in\
foreclosing mortgages upon the debt-burdened farmers, against the\
lawyers for increasing the costs of legal proceedings, against the\
senate of the state the members of which were apportioned among the\
towns on the basis of the amount of taxes paid, against heavy taxes, and\
against the refusal of the legislature to issue paper money. They seized\
the towns of Worcester and Springfield and broke up the courts of\
justice. All through the western part of the state the revolt spread,\
sending a shock of alarm to every center and section of the young\
republic. Only by the most vigorous action was Governor Bowdoin able to\
quell the uprising; and when that task was accomplished, the state\
government did not dare to execute any of the prisoners because they had\
so many sympathizers. Moreover, Bowdoin and several members of the\
legislature who had been most zealous in their attacks on the insurgents\
were defeated at the ensuing election. The need of national assistance\
for state governments in times of domestic violence was everywhere\
emphasized by men who were opposed to revolutionary acts.\
\
=Alarm over Dangers to the Republic.=--Leading American citizens,\
watching the drift of affairs, were slowly driven to the conclusion that\
the new ship of state so proudly launched a few years before was\
careening into anarchy. "The facts of our peace and independence," wrote\
a friend of Washington, "do not at present wear so promising an\
appearance as I had fondly painted in my mind. The prejudices,\
jealousies, and turbulence of the people at times almost stagger my\
confidence in our political establishments; and almost occasion me to\
think that they will show themselves unworthy of the noble prize for\
which we have contended."\
\
Washington himself was profoundly discouraged. On hearing of Shays's\
rebellion, he exclaimed: "What, gracious God, is man that there should\
be such inconsistency and perfidiousness in his conduct! It is but the\
other day that we were shedding our blood to obtain the constitutions\
under which we now live--constitutions of our own choice and making--and\
now we are unsheathing our sword to overturn them." The same year he\
burst out in a lament over rumors of restoring royal government. "I am\
told that even respectable characters speak of a monarchical government\
without horror. From thinking proceeds speaking. Hence to acting is\
often but a single step. But how irresistible and tremendous! What a\
triumph for our enemies to verify their predictions! What a triumph for\
the advocates of despotism to find that we are incapable of governing\
ourselves!"\
\
=Congress Attempts Some Reforms.=--The Congress was not indifferent to\
the events that disturbed Washington. On the contrary it put forth many\
efforts to check tendencies so dangerous to finance, commerce,\
industries, and the Confederation itself. In 1781, even before the\
treaty of peace was signed, the Congress, having found out how futile\
were its taxing powers, carried a resolution of amendment to the\
Articles of Confederation, authorizing the levy of a moderate duty on\
imports. Yet this mild measure was rejected by the states. Two years\
later the Congress prepared another amendment sanctioning the levy of\
duties on imports, to be collected this time by state officers and\
applied to the payment of the public debt. This more limited proposal,\
designed to save public credit, likewise failed. In 1786, the Congress\
made a third appeal to the states for help, declaring that they had been\
so irregular and so negligent in paying their quotas that further\
reliance upon that mode of raising revenues was dishonorable and\
dangerous.\
\
\
THE CALLING OF A CONSTITUTIONAL CONVENTION\
\
=Hamilton and Washington Urge Reform.=--The attempts at reform by the\
Congress were accompanied by demand for, both within and without that\
body, a convention to frame a new plan of government. In 1780, the\
youthful Alexander Hamilton, realizing the weakness of the Articles, so\
widely discussed, proposed a general convention for the purpose of\
drafting a new constitution on entirely different principles. With\
tireless energy he strove to bring his countrymen to his view.\
Washington, agreeing with him on every point, declared, in a circular\
letter to the governors, that the duration of the union would be short\
unless there was lodged somewhere a supreme power "to regulate and\
govern the general concerns of the confederated republic." The governor\
of Massachusetts, disturbed by the growth of discontent all about him,\
suggested to the state legislature in 1785 the advisability of a\
national convention to enlarge the powers of the Congress. The\
legislature approved the plan, but did not press it to a conclusion.\
\
[Illustration: ALEXANDER HAMILTON]\
\
=The Annapolis Convention.=--Action finally came from the South. The\
Virginia legislature, taking things into its own hands, called a\
conference of delegates at Annapolis to consider matters of taxation and\
commerce. When the convention assembled in 1786, it was found that only\
five states had taken the trouble to send representatives. The leaders\
were deeply discouraged, but the resourceful Hamilton, a delegate from\
New York, turned the affair to good account. He secured the adoption of\
a resolution, calling upon the Congress itself to summon another\
convention, to meet at Philadelphia.\
\
=A National Convention Called (1787).=--The Congress, as tardy as ever,\
at last decided in February, 1787, to issue the call. Fearing drastic\
changes, however, it restricted the convention to "the sole and express\
purpose of revising the Articles of Confederation." Jealous of its own\
powers, it added that any alterations proposed should be referred to the\
Congress and the states for their approval.\
\
Every state in the union, except Rhode Island, responded to this call.\
Indeed some of the states, having the Annapolis resolution before them,\
had already anticipated the Congress by selecting delegates before the\
formal summons came. Thus, by the persistence of governors,\
legislatures, and private citizens, there was brought about the\
long-desired national convention. In May, 1787, it assembled in\
Philadelphia.\
\
=The Eminent Men of the Convention.=--On the roll of that memorable\
convention were fifty-five men, at least half of whom were acknowledged\
to be among the foremost statesmen and thinkers in America. Every field\
of statecraft was represented by them: war and practical management in\
Washington, who was chosen president of the convention; diplomacy in\
Franklin, now old and full of honor in his own land as well as abroad;\
finance in Alexander Hamilton and Robert Morris; law in James Wilson of\
Pennsylvania; the philosophy of government in James Madison, called the\
"father of the Constitution." They were not theorists but practical men,\
rich in political experience and endowed with deep insight into the\
springs of human action. Three of them had served in the Stamp Act\
Congress: Dickinson of Delaware, William Samuel Johnson of Connecticut,\
and John Rutledge of South Carolina. Eight had been signers of the\
Declaration of Independence: Read of Delaware, Sherman of Connecticut,\
Wythe of Virginia, Gerry of Massachusetts, Franklin, Robert Morris,\
George Clymer, and James Wilson of Pennsylvania. All but twelve had at\
some time served in the Continental Congress and eighteen were members\
of that body in the spring of 1787. Washington, Hamilton, Mifflin, and\
Charles Pinckney had been officers in the Revolutionary army. Seven of\
the delegates had gained political experience as governors of states.\
"The convention as a whole," according to the historian Hildreth,\
"represented in a marked manner the talent, intelligence, and\
especially the conservative sentiment of the country."\
\
\
THE FRAMING OF THE CONSTITUTION\
\
=Problems Involved.=--The great problems before the convention were nine\
in number: (1) Shall the Articles of Confederation be revised or a new\
system of government constructed? (2) Shall the government be founded on\
states equal in power as under the Articles or on the broader and deeper\
foundation of population? (3) What direct share shall the people have in\
the election of national officers? (4) What shall be the qualifications\
for the suffrage? (5) How shall the conflicting interests of the\
commercial and the planting states be balanced so as to safeguard the\
essential rights of each? (6) What shall be the form of the new\
government? (7) What powers shall be conferred on it? (8) How shall the\
state legislatures be restrained from their attacks on property rights\
such as the issuance of paper money? (9) Shall the approval of all the\
states be necessary, as under the Articles, for the adoption and\
amendment of the Constitution?\
\
=Revision of the Articles or a New Government?=--The moment the first\
problem was raised, representatives of the small states, led by William\
Paterson of New Jersey, were on their feet. They feared that, if the\
Articles were overthrown, the equality and rights of the states would be\
put in jeopardy. Their protest was therefore vigorous. They cited the\
call issued by the Congress in summoning the convention which\
specifically stated that they were assembled for "the sole and express\
purpose of revising the Articles of Confederation." They cited also\
their instructions from their state legislatures, which authorized them\
to "revise and amend" the existing scheme of government, not to make a\
revolution in it. To depart from the authorization laid down by the\
Congress and the legislatures would be to exceed their powers, they\
argued, and to betray the trust reposed in them by their countrymen.\
\
To their contentions, Randolph of Virginia replied: "When the salvation\
of the republic is at stake, it would be treason to our trust not to\
propose what we find necessary." Hamilton, reminding the delegates that\
their work was still subject to the approval of the states, frankly said\
that on the point of their powers he had no scruples. With the issue\
clear, the convention cast aside the Articles as if they did not exist\
and proceeded to the work of drawing up a new constitution, "laying its\
foundations on such principles and organizing its powers in such form"\
as to the delegates seemed "most likely to affect their safety and\
happiness."\
\
=A Government Founded on States or on People?--The\
Compromise.=--Defeated in their attempt to limit the convention to a\
mere revision of the Articles, the spokesmen of the smaller states\
redoubled their efforts to preserve the equality of the states. The\
signal for a radical departure from the Articles on this point was given\
early in the sessions when Randolph presented "the Virginia plan." He\
proposed that the new national legislature consist of two houses, the\
members of which were to be apportioned among the states according to\
their wealth or free white population, as the convention might decide.\
This plan was vehemently challenged. Paterson of New Jersey flatly\
avowed that neither he nor his state would ever bow to such tyranny. As\
an alternative, he presented "the New Jersey plan" calling for a\
national legislature of one house representing states as such, not\
wealth or people--a legislature in which all states, large or small,\
would have equal voice. Wilson of Pennsylvania, on behalf of the more\
populous states, took up the gauntlet which Paterson had thrown down. It\
was absurd, he urged, for 180,000 men in one state to have the same\
weight in national counsels as 750,000 men in another state. "The\
gentleman from New Jersey," he said, "is candid. He declares his opinion\
boldly.... I will be equally candid.... I will never confederate on his\
principles." So the bitter controversy ran on through many exciting\
sessions.\
\
Greek had met Greek. The convention was hopelessly deadlocked and on the\
verge of dissolution, "scarce held together by the strength of a hair,"\
as one of the delegates remarked. A crash was averted only by a\
compromise. Instead of a Congress of one house as provided by the\
Articles, the convention agreed upon a legislature of two houses. In the\
Senate, the aspirations of the small states were to be satisfied, for\
each state was given two members in that body. In the formation of the\
House of Representatives, the larger states were placated, for it was\
agreed that the members of that chamber were to be apportioned among the\
states on the basis of population, counting three-fifths of the slaves.\
\
=The Question of Popular Election.=--The method of selecting federal\
officers and members of Congress also produced an acrimonious debate\
which revealed how deep-seated was the distrust of the capacity of the\
people to govern themselves. Few there were who believed that no branch\
of the government should be elected directly by the voters; still fewer\
were there, however, who desired to see all branches so chosen. One or\
two even expressed a desire for a monarchy. The dangers of democracy\
were stressed by Gerry of Massachusetts: "All the evils we experience\
flow from an excess of democracy. The people do not want virtue but are\
the dupes of pretended patriots.... I have been too republican\
heretofore but have been taught by experience the danger of a leveling\
spirit." To the "democratic licentiousness of the state legislatures,"\
Randolph sought to oppose a "firm senate." To check the excesses of\
popular government Charles Pinckney of South Carolina declared that no\
one should be elected President who was not worth $100,000 and that high\
property qualifications should be placed on members of Congress and\
judges. Other members of the convention were stoutly opposed to such\
"high-toned notions of government." Franklin and Wilson, both from\
Pennsylvania, vigorously championed popular election; while men like\
Madison insisted that at least one part of the government should rest on\
the broad foundation of the people.\
\
Out of this clash of opinion also came compromise. One branch, the House\
of Representatives, it was agreed, was to be elected directly by the\
voters, while the Senators were to be elected indirectly by the state\
legislatures. The President was to be chosen by electors selected as the\
legislatures of the states might determine, and the judges of the\
federal courts, supreme and inferior, by the President and the Senate.\
\
=The Question of the Suffrage.=--The battle over the suffrage was sharp\
but brief. Gouverneur Morris proposed that only land owners should be\
permitted to vote. Madison replied that the state legislatures, which\
had made so much trouble with radical laws, were elected by freeholders.\
After the debate, the delegates, unable to agree on any property\
limitations on the suffrage, decided that the House of Representatives\
should be elected by voters having the "qualifications requisite for\
electors of the most numerous branch of the state legislature." Thus\
they accepted the suffrage provisions of the states.\
\
=The Balance between the Planting and the Commercial States.=--After the\
debates had gone on for a few weeks, Madison came to the conclusion that\
the real division in the convention was not between the large and the\
small states but between the planting section founded on slave labor and\
the commercial North. Thus he anticipated by nearly three-quarters of a\
century "the irrepressible conflict." The planting states had neither\
the free white population nor the wealth of the North. There were,\
counting Delaware, six of them as against seven commercial states.\
Dependent for their prosperity mainly upon the sale of tobacco, rice,\
and other staples abroad, they feared that Congress might impose\
restraints upon their enterprise. Being weaker in numbers, they were\
afraid that the majority might lay an unfair burden of taxes upon them.\
\
_Representation and Taxation._--The Southern members of the convention\
were therefore very anxious to secure for their section the largest\
possible representation in Congress, and at the same time to restrain\
the taxing power of that body. Two devices were thought adapted to these\
ends. One was to count the slaves as people when apportioning\
representatives among the states according to their respective\
populations; the other was to provide that direct taxes should be\
apportioned among the states, in proportion not to their wealth but to\
the number of their free white inhabitants. For obvious reasons the\
Northern delegates objected to these proposals. Once more a compromise\
proved to be the solution. It was agreed that not all the slaves but\
three-fifths of them should be counted for both purposes--representation\
and direct taxation.\
\
_Commerce and the Slave Trade._--Southern interests were also involved\
in the project to confer upon Congress the power to regulate interstate\
and foreign commerce. To the manufacturing and trading states this was\
essential. It would prevent interstate tariffs and trade jealousies; it\
would enable Congress to protect American manufactures and to break\
down, by appropriate retaliations, foreign discriminations against\
American commerce. To the South the proposal was menacing because\
tariffs might interfere with the free exchange of the produce of\
plantations in European markets, and navigation acts might confine the\
carrying trade to American, that is Northern, ships. The importation of\
slaves, moreover, it was feared might be heavily taxed or immediately\
prohibited altogether.\
\
The result of this and related controversies was a debate on the merits\
of slavery. Gouverneur Morris delivered his mind and heart on that\
subject, denouncing slavery as a nefarious institution and the curse of\
heaven on the states in which it prevailed. Mason of Virginia, a\
slaveholder himself, was hardly less outspoken, saying: "Slavery\
discourages arts and manufactures. The poor despise labor when performed\
by slaves. They prevent the migration of whites who really strengthen\
and enrich a country."\
\
The system, however, had its defenders. Representatives from South\
Carolina argued that their entire economic life rested on slave labor\
and that the high death rate in the rice swamps made continuous\
importation necessary. Ellsworth of Connecticut took the ground that\
the convention should not meddle with slavery. "The morality or wisdom\
of slavery," he said, "are considerations belonging to the states. What\
enriches a part enriches the whole." To the future he turned an\
untroubled face: "As population increases, poor laborers will be so\
plenty as to render slaves useless. Slavery in time will not be a speck\
in our country." Virginia and North Carolina, already overstocked with\
slaves, favored prohibiting the traffic in them; but South Carolina was\
adamant. She must have fresh supplies of slaves or she would not\
federate.\
\
So it was agreed that, while Congress might regulate foreign trade by\
majority vote, the importation of slaves should not be forbidden before\
the lapse of twenty years, and that any import tax should not exceed $10\
a head. At the same time, in connection with the regulation of foreign\
trade, it was stipulated that a two-thirds vote in the Senate should be\
necessary in the ratification of treaties. A further concession to the\
South was made in the provision for the return of runaway slaves--a\
provision also useful in the North, where indentured servants were about\
as troublesome as slaves in escaping from their masters.\
\
=The Form of the Government.=--As to the details of the frame of\
government and the grand principles involved, the opinion of the\
convention ebbed and flowed, decisions being taken in the heat of\
debate, only to be revoked and taken again.\
\
_The Executive._--There was general agreement that there should be an\
executive branch; for reliance upon Congress to enforce its own laws and\
treaties had been a broken reed. On the character and functions of the\
executive, however, there were many views. The New Jersey plan called\
for a council selected by the Congress; the Virginia plan provided that\
the executive branch should be chosen by the Congress but did not state\
whether it should be composed of one or several persons. On this matter\
the convention voted first one way and then another; finally it agreed\
on a single executive chosen indirectly by electors selected as the\
state legislatures might decide, serving for four years, subject to\
impeachment, and endowed with regal powers in the command of the army\
and the navy and in the enforcement of the laws.\
\
_The Legislative Branch--Congress._--After the convention had made the\
great compromise between the large and small commonwealths by giving\
representation to states in the Senate and to population in the House,\
the question of methods of election had to be decided. As to the House\
of Representatives it was readily agreed that the members should be\
elected by direct popular vote. There was also easy agreement on the\
proposition that a strong Senate was needed to check the "turbulence" of\
the lower house. Four devices were finally selected to accomplish this\
purpose. In the first place, the Senators were not to be chosen directly\
by the voters but by the legislatures of the states, thus removing their\
election one degree from the populace. In the second place, their term\
was fixed at six years instead of two, as in the case of the House. In\
the third place, provision was made for continuity by having only\
one-third of the members go out at a time while two-thirds remained in\
service. Finally, it was provided that Senators must be at least thirty\
years old while Representatives need be only twenty-five.\
\
_The Judiciary._--The need for federal courts to carry out the law was\
hardly open to debate. The feebleness of the Articles of Confederation\
was, in a large measure, attributed to the want of a judiciary to hold\
states and individuals in obedience to the laws and treaties of the\
union. Nevertheless on this point the advocates of states' rights were\
extremely sensitive. They looked with distrust upon judges appointed at\
the national capital and emancipated from local interests and\
traditions; they remembered with what insistence they had claimed\
against Britain the right of local trial by jury and with what\
consternation they had viewed the proposal to make colonial judges\
independent of the assemblies in the matter of their salaries.\
Reluctantly they yielded to the demand for federal courts, consenting at\
first only to a supreme court to review cases heard in lower state\
courts and finally to such additional inferior courts as Congress might\
deem necessary.\
\
_The System of Checks and Balances._--It is thus apparent that the\
framers of the Constitution, in shaping the form of government, arranged\
for a distribution of power among three branches, executive,\
legislative, and judicial. Strictly speaking we might say four branches,\
for the legislature, or Congress, was composed of two houses, elected in\
different ways, and one of them, the Senate, was made a check on the\
President through its power of ratifying treaties and appointments. "The\
accumulation of all powers, legislative, executive, and judicial, in the\
same hands," wrote Madison, "whether of one, a few, or many, and whether\
hereditary, self-appointed, or elective, may justly be pronounced the\
very definition of tyranny." The devices which the convention adopted to\
prevent such a centralization of authority were exceedingly ingenious\
and well calculated to accomplish the purposes of the authors.\
\
The legislature consisted of two houses, the members of which were to be\
apportioned on a different basis, elected in different ways, and to\
serve for different terms. A veto on all its acts was vested in a\
President elected in a manner not employed in the choice of either\
branch of the legislature, serving for four years, and subject to\
removal only by the difficult process of impeachment. After a law had\
run the gantlet of both houses and the executive, it was subject to\
interpretation and annulment by the judiciary, appointed by the\
President with the consent of the Senate and serving for life. Thus it\
was made almost impossible for any political party to get possession of\
all branches of the government at a single popular election. As Hamilton\
remarked, the friends of good government considered "every institution\
calculated to restrain the excess of law making and to keep things in\
the same state in which they happen to be at any given period as more\
likely to do good than harm."\
\
=The Powers of the Federal Government.=--On the question of the powers\
to be conferred upon the new government there was less occasion for a\
serious dispute. Even the delegates from the small states agreed with\
those from Massachusetts, Pennsylvania, and Virginia that new powers\
should be added to those intrusted to Congress by the Articles of\
Confederation. The New Jersey plan as well as the Virginia plan\
recognized this fact. Some of the delegates, like Hamilton and Madison,\
even proposed to give Congress a general legislative authority covering\
all national matters; but others, frightened by the specter of\
nationalism, insisted on specifying each power to be conferred and\
finally carried the day.\
\
_Taxation and Commerce._--There were none bold enough to dissent from\
the proposition that revenue must be provided to pay current expenses\
and discharge the public debt. When once the dispute over the\
apportionment of direct taxes among the slave states was settled, it was\
an easy matter to decide that Congress should have power to lay and\
collect taxes, duties, imposts, and excises. In this way the national\
government was freed from dependence upon stubborn and tardy\
legislatures and enabled to collect funds directly from citizens. There\
were likewise none bold enough to contend that the anarchy of state\
tariffs and trade discriminations should be longer endured. When the\
fears of the planting states were allayed and the "bargain" over the\
importation of slaves was reached, the convention vested in Congress the\
power to regulate foreign and interstate commerce.\
\
_National Defense._--The necessity for national defense was realized,\
though the fear of huge military establishments was equally present. The\
old practice of relying on quotas furnished by the state legislatures\
was completely discredited. As in the case of taxes a direct authority\
over citizens was demanded. Congress was therefore given full power to\
raise and support armies and a navy. It could employ the state militia\
when desirable; but it could at the same time maintain a regular army\
and call directly upon all able-bodied males if the nature of a crisis\
was thought to require it.\
\
_The "Necessary and Proper" Clause._--To the specified power vested in\
Congress by the Constitution, the advocates of a strong national\
government added a general clause authorizing it to make all laws\
"necessary and proper" for carrying into effect any and all of the\
enumerated powers. This clause, interpreted by that master mind, Chief\
Justice Marshall, was later construed to confer powers as wide as the\
requirements of a vast country spanning a continent and taking its place\
among the mighty nations of the earth.\
\
=Restraints on the States.=--Framing a government and endowing it with\
large powers were by no means the sole concern of the convention. Its\
very existence had been due quite as much to the conduct of the state\
legislatures as to the futilities of a paralyzed Continental Congress.\
In every state, explains Marshall in his _Life of Washington_, there was\
a party of men who had "marked out for themselves a more indulgent\
course. Viewing with extreme tenderness the case of the debtor, their\
efforts were unceasingly directed to his relief. To exact a faithful\
compliance with contracts was, in their opinion, a harsh measure which\
the people could not bear. They were uniformly in favor of relaxing the\
administration of justice, of affording facilities for the payment of\
debts, or of suspending their collection, and remitting taxes."\
\
The legislatures under the dominance of these men had enacted paper\
money laws enabling debtors to discharge their obligations more easily.\
The convention put an end to such practices by providing that no state\
should emit bills of credit or make anything but gold or silver legal\
tender in the payment of debts. The state legislatures had enacted laws\
allowing men to pay their debts by turning over to creditors land or\
personal property; they had repealed the charter of an endowed college\
and taken the management from the hands of the lawful trustees; and they\
had otherwise interfered with the enforcement of private agreements. The\
convention, taking notice of such matters, inserted a clause forbidding\
states "to impair the obligation of contracts." The more venturous of\
the radicals had in Massachusetts raised the standard of revolt against\
the authorities of the state. The convention answered by a brief\
sentence to the effect that the President of the United States, to be\
equipped with a regular army, would send troops to suppress domestic\
insurrections whenever called upon by the legislature or, if it was not\
in session, by the governor of the state. To make sure that the\
restrictions on the states would not be dead letters, the federal\
Constitution, laws, and treaties were made the supreme law of the land,\
to be enforced whenever necessary by a national judiciary and executive\
against violations on the part of any state authorities.\
\
=Provisions for Ratification and Amendment.=--When the frame of\
government had been determined, the powers to be vested in it had been\
enumerated, and the restrictions upon the states had been written into\
the bond, there remained three final questions. How shall the\
Constitution be ratified? What number of states shall be necessary to\
put it into effect? How shall it be amended in the future?\
\
On the first point, the mandate under which the convention was sitting\
seemed positive. The Articles of Confederation were still in effect.\
They provided that amendments could be made only by unanimous adoption\
in Congress and the approval of all the states. As if to give force to\
this provision of law, the call for the convention had expressly stated\
that all alterations and revisions should be reported to Congress for\
adoption or rejection, Congress itself to transmit the document\
thereafter to the states for their review.\
\
To have observed the strict letter of the law would have defeated the\
purposes of the delegates, because Congress and the state legislatures\
were openly hostile to such drastic changes as had been made. Unanimous\
ratification, as events proved, would have been impossible. Therefore\
the delegates decided that the Constitution should be sent to Congress\
with the recommendation that it, in turn, transmit the document, not to\
the state legislatures, but to conventions held in the states for the\
special object of deciding upon ratification. This process was followed.\
It was their belief that special conventions would be more friendly than\
the state legislatures.\
\
The convention was equally positive in dealing with the problem of the\
number of states necessary to establish the new Constitution. Attempts\
to change the Articles had failed because amendment required the\
approval of every state and there was always at least one recalcitrant\
member of the union. The opposition to a new Constitution was\
undoubtedly formidable. Rhode Island had even refused to take part in\
framing it, and her hostility was deep and open. So the convention cast\
aside the provision of the Articles of Confederation which required\
unanimous approval for any change in the plan of government; it decreed\
that the new Constitution should go into effect when ratified by nine\
states.\
\
In providing for future changes in the Constitution itself the\
convention also thrust aside the old rule of unanimous approval, and\
decided that an amendment could be made on a two-thirds vote in both\
houses of Congress and ratification by three-fourths of the states. This\
change was of profound significance. Every state agreed to be bound in\
the future by amendments duly adopted even in case it did not approve\
them itself. America in this way set out upon the high road that led\
from a league of states to a nation.\
\
\
THE STRUGGLE OVER RATIFICATION\
\
On September 17, 1787, the Constitution, having been finally drafted in\
clear and simple language, a model to all makers of fundamental law, was\
adopted. The convention, after nearly four months of debate in secret\
session, flung open the doors and presented to the Americans the\
finished plan for the new government. Then the great debate passed to\
the people.\
\
=The Opposition.=--Storms of criticism at once descended upon the\
Constitution. "Fraudulent usurpation!" exclaimed Gerry, who had refused\
to sign it. "A monster" out of the "thick veil of secrecy," declaimed a\
Pennsylvania newspaper. "An iron-handed despotism will be the result,"\
protested a third. "We, 'the low-born,'" sarcastically wrote a fourth,\
"will now admit the 'six hundred well-born' immediately to establish\
this most noble, most excellent, and truly divine constitution." The\
President will become a king; Congress will be as tyrannical as\
Parliament in the old days; the states will be swallowed up; the rights\
of the people will be trampled upon; the poor man's justice will be lost\
in the endless delays of the federal courts--such was the strain of the\
protests against ratification.\
\
[Illustration: AN ADVERTISEMENT OF _The Federalist_]\
\
=Defense of the Constitution.=--Moved by the tempest of opposition,\
Hamilton, Madison, and Jay took up their pens in defense of the\
Constitution. In a series of newspaper articles they discussed and\
expounded with eloquence, learning, and dignity every important clause\
and provision of the proposed plan. These papers, afterwards collected\
and published in a volume known as _The Federalist_, form the finest\
textbook on the Constitution that has ever been printed. It takes its\
place, moreover, among the wisest and weightiest treatises on government\
ever written in any language in any time. Other men, not so gifted, were\
no less earnest in their support of ratification. In private\
correspondence, editorials, pamphlets, and letters to the newspapers,\
they urged their countrymen to forget their partisanship and accept a\
Constitution which, in spite of any defects great or small, was the\
only guarantee against dissolution and warfare at home and dishonor and\
weakness abroad.\
\
[Illustration: CELEBRATING THE RATIFICATION]\
\
=The Action of the State Conventions.=--Before the end of the year,\
1787, three states had ratified the Constitution: Delaware and New\
Jersey unanimously and Pennsylvania after a short, though savage,\
contest. Connecticut and Georgia followed early the next year. Then came\
the battle royal in Massachusetts, ending in ratification in February by\
the narrow margin of 187 votes to 168. In the spring came the news that\
Maryland and South Carolina were "under the new roof." On June 21, New\
Hampshire, where the sentiment was at first strong enough to defeat the\
Constitution, joined the new republic, influenced by the favorable\
decision in Massachusetts. Swift couriers were sent to carry the news to\
New York and Virginia, where the question of ratification was still\
undecided. Nine states had accepted it and were united, whether more saw\
fit to join or not.\
\
Meanwhile, however, Virginia, after a long and searching debate, had\
given her approval by a narrow margin, leaving New York as the next seat\
of anxiety. In that state the popular vote for the delegates to the\
convention had been clearly and heavily against ratification. Events\
finally demonstrated the futility of resistance, and Hamilton by good\
judgment and masterly arguments was at last able to marshal a majority\
of thirty to twenty-seven votes in favor of ratification.\
\
The great contest was over. All the states, except North Carolina and\
Rhode Island, had ratified. "The sloop Anarchy," wrote an ebullient\
journalist, "when last heard from was ashore on Union rocks."\
\
=The First Election.=--In the autumn of 1788, elections were held to\
fill the places in the new government. Public opinion was overwhelmingly\
in favor of Washington as the first President. Yielding to the\
importunities of friends, he accepted the post in the spirit of public\
service. On April 30, 1789, he took the oath of office at Federal Hall\
in New York City. "Long live George Washington, President of the United\
States!" cried Chancellor Livingston as soon as the General had kissed\
the Bible. The cry was caught by the assembled multitude and given back.\
A new experiment in popular government was launched.\
\
\
=References=\
\
M. Farrand, _The Framing of the Constitution of the United States_.\
\
P.L. Ford, _Essays on the Constitution of the United States_.\
\
_The Federalist_ (in many editions).\
\
G. Hunt, _Life of James Madison_.\
\
A.C. McLaughlin, _The Confederation and the Constitution_ (American\
Nation Series).\
\
\
=Questions=\
\
1. Account for the failure of the Articles of Confederation.\
\
2. Explain the domestic difficulties of the individual states.\
\
3. Why did efforts at reform by the Congress come to naught?\
\
4. Narrate the events leading up to the constitutional convention.\
\
5. Who were some of the leading men in the convention? What had been\
their previous training?\
\
6. State the great problems before the convention.\
\
7. In what respects were the planting and commercial states opposed?\
What compromises were reached?\
\
8. Show how the "check and balance" system is embodied in our form of\
government.\
\
9. How did the powers conferred upon the federal government help cure\
the defects of the Articles of Confederation?\
\
10. In what way did the provisions for ratifying and amending the\
Constitution depart from the old system?\
\
11. What was the nature of the conflict over ratification?\
\
\
=Research Topics=\
\
=English Treatment of American Commerce.=--Callender, _Economic History\
of the United States_, pp. 210-220.\
\
=Financial Condition of the United States.=--Fiske, _Critical Period of\
American History_, pp. 163-186.\
\
=Disordered Commerce.=--Fiske, pp. 134-162.\
\
=Selfish Conduct of the States.=--Callender, pp. 185-191.\
\
=The Failure of the Confederation.=--Elson, _History of the United\
States_, pp. 318-326.\
\
=Formation of the Constitution.=--(1) The plans before the convention,\
Fiske, pp. 236-249; (2) the great compromise, Fiske, pp. 250-255; (3)\
slavery and the convention, Fiske, pp. 256-266; and (4) the frame of\
government, Fiske, pp. 275-301; Elson, pp. 328-334.\
\
=Biographical Studies.=--Look up the history and services of the leaders\
in the convention in any good encyclopedia.\
\
=Ratification of the Constitution.=--Hart, _History Told by\
Contemporaries_, Vol. III, pp. 233-254; Elson, pp. 334-340.\
\
=Source Study.=--Compare the Constitution and Articles of Confederation\
under the following heads: (1) frame of government; (2) powers of\
Congress; (3) limits on states; and (4) methods of amendment. Every line\
of the Constitution should be read and re-read in the light of the\
historical circumstances set forth in this chapter.\
\
\
\
\
CHAPTER VIII\
\
THE CLASH OF POLITICAL PARTIES\
\
\
THE MEN AND MEASURES OF THE NEW GOVERNMENT\
\
=Friends of the Constitution in Power.=--In the first Congress that\
assembled after the adoption of the Constitution, there were eleven\
Senators, led by Robert Morris, the financier, who had been delegates to\
the national convention. Several members of the House of\
Representatives, headed by James Madison, had also been at Philadelphia\
in 1787. In making his appointments, Washington strengthened the new\
system of government still further by a judicious selection of\
officials. He chose as Secretary of the Treasury, Alexander Hamilton,\
who had been the most zealous for its success; General Knox, head of the\
War Department, and Edmund Randolph, the Attorney-General, were likewise\
conspicuous friends of the experiment. Every member of the federal\
judiciary whom Washington appointed, from the Chief Justice, John Jay,\
down to the justices of the district courts, had favored the\
ratification of the Constitution; and a majority of them had served as\
members of the national convention that framed the document or of the\
state ratifying conventions. Only one man of influence in the new\
government, Thomas Jefferson, the Secretary of State, was reckoned as a\
doubter in the house of the faithful. He had expressed opinions both for\
and against the Constitution; but he had been out of the country acting\
as the minister at Paris when the Constitution was drafted and ratified.\
\
=An Opposition to Conciliate.=--The inauguration of Washington amid the\
plaudits of his countrymen did not set at rest all the political turmoil\
which had been aroused by the angry contest over ratification. "The\
interesting nature of the question," wrote John Marshall, "the equality\
of the parties, the animation produced inevitably by ardent debate had a\
necessary tendency to embitter the dispositions of the vanquished and to\
fix more deeply in many bosoms their prejudices against a plan of\
government in opposition to which all their passions were enlisted." The\
leaders gathered around Washington were well aware of the excited state\
of the country. They saw Rhode Island and North Carolina still outside\
of the union.[1] They knew by what small margins the Constitution had\
been approved in the great states of Massachusetts, Virginia, and New\
York. They were equally aware that a majority of the state conventions,\
in yielding reluctant approval to the Constitution, had drawn a number\
of amendments for immediate submission to the states.\
\
=The First Amendments--a Bill of Rights.=--To meet the opposition,\
Madison proposed, and the first Congress adopted, a series of amendments\
to the Constitution. Ten of them were soon ratified and became in 1791 a\
part of the law of the land. These amendments provided, among other\
things, that Congress could make no law respecting the establishment of\
religion, abridging the freedom of speech or of the press or the right\
of the people peaceably to assemble and petition the government for a\
redress of grievances. They also guaranteed indictment by grand jury and\
trial by jury for all persons charged by federal officers with serious\
crimes. To reassure those who still feared that local rights might be\
invaded by the federal government, the tenth amendment expressly\
provided that the powers not delegated to the United States by the\
Constitution, nor prohibited by it to the states, are reserved to the\
states respectively or to the people. Seven years later, the eleventh\
amendment was written in the same spirit as the first ten, after a\
heated debate over the action of the Supreme Court in permitting a\
citizen to bring a suit against "the sovereign state" of Georgia. The\
new amendment was designed to protect states against the federal\
judiciary by forbidding it to hear any case in which a state was sued by\
a citizen.\
\
=Funding the National Debt.=--Paper declarations of rights, however,\
paid no bills. To this task Hamilton turned all his splendid genius. At\
the very outset he addressed himself to the problem of the huge public\
debt, daily mounting as the unpaid interest accumulated. In a _Report on\
Public Credit_ under date of January 9, 1790, one of the first and\
greatest of American state papers, he laid before Congress the outlines\
of his plan. He proposed that the federal government should call in all\
the old bonds, certificates of indebtedness, and other promises to pay\
which had been issued by the Congress since the beginning of the\
Revolution. These national obligations, he urged, should be put into one\
consolidated debt resting on the credit of the United States; to the\
holders of the old paper should be issued new bonds drawing interest at\
fixed rates. This process was called "funding the debt." Such a\
provision for the support of public credit, Hamilton insisted, would\
satisfy creditors, restore landed property to its former value, and\
furnish new resources to agriculture and commerce in the form of credit\
and capital.\
\
=Assumption and Funding of State Debts.=--Hamilton then turned to the\
obligations incurred by the several states in support of the Revolution.\
These debts he proposed to add to the national debt. They were to be\
"assumed" by the United States government and placed on the same secure\
foundation as the continental debt. This measure he defended not merely\
on grounds of national honor. It would, as he foresaw, give strength to\
the new national government by making all public creditors, men of\
substance in their several communities, look to the federal, rather than\
the state government, for the satisfaction of their claims.\
\
=Funding at Face Value.=--On the question of the terms of consolidation,\
assumption, and funding, Hamilton had a firm conviction. That millions\
of dollars' worth of the continental and state bonds had passed out of\
the hands of those who had originally subscribed their funds to the\
support of the government or had sold supplies for the Revolutionary\
army was well known. It was also a matter of common knowledge that a\
very large part of these bonds had been bought by speculators at ruinous\
figures--ten, twenty, and thirty cents on the dollar. Accordingly, it\
had been suggested, even in very respectable quarters, that a\
discrimination should be made between original holders and speculative\
purchasers. Some who held this opinion urged that the speculators who\
had paid nominal sums for their bonds should be reimbursed for their\
outlays and the original holders paid the difference; others said that\
the government should "scale the debt" by redeeming, not at full value\
but at a figure reasonably above the market price. Against the\
proposition Hamilton set his face like flint. He maintained that the\
government was honestly bound to redeem every bond at its face value,\
although the difficulty of securing revenue made necessary a lower rate\
of interest on a part of the bonds and the deferring of interest on\
another part.\
\
=Funding and Assumption Carried.=--There was little difficulty in\
securing the approval of both houses of Congress for the funding of the\
national debt at full value. The bill for the assumption of state debts,\
however, brought the sharpest division of opinions. To the Southern\
members of Congress assumption was a gross violation of states' rights,\
without any warrant in the Constitution and devised in the interest of\
Northern speculators who, anticipating assumption and funding, had\
bought up at low prices the Southern bonds and other promises to pay.\
New England, on the other hand, was strongly in favor of assumption;\
several representatives from that section were rash enough to threaten a\
dissolution of the union if the bill was defeated. To this dispute was\
added an equally bitter quarrel over the location of the national\
capital, then temporarily at New York City.\
\
[Illustration: FIRST UNITED STATES BANK AT PHILADELPHIA]\
\
A deadlock, accompanied by the most surly feelings on both sides,\
threatened the very existence of the young government. Washington and\
Hamilton were thoroughly alarmed. Hearing of the extremity to which the\
contest had been carried and acting on the appeal from the Secretary of\
the Treasury, Jefferson intervened at this point. By skillful management\
at a good dinner he brought the opposing leaders together; and thus once\
more, as on many other occasions, peace was purchased and the union\
saved by compromise. The bargain this time consisted of an exchange of\
votes for assumption in return for votes for the capital. Enough\
Southern members voted for assumption to pass the bill, and a majority\
was mustered in favor of building the capital on the banks of the\
Potomac, after locating it for a ten-year period at Philadelphia to\
satisfy Pennsylvania members.\
\
=The United States Bank.=--Encouraged by the success of his funding and\
assumption measures, Hamilton laid before Congress a project for a great\
United States Bank. He proposed that a private corporation be chartered\
by Congress, authorized to raise a capital stock of $10,000,000\
(three-fourths in new six per cent federal bonds and one-fourth in\
specie) and empowered to issue paper currency under proper safeguards.\
Many advantages, Hamilton contended, would accrue to the government from\
this institution. The price of the government bonds would be increased,\
thus enhancing public credit. A national currency would be created of\
uniform value from one end of the land to the other. The branches of the\
bank in various cities would make easy the exchange of funds so vital to\
commercial transactions on a national scale. Finally, through the issue\
of bank notes, the money capital available for agriculture and industry\
would be increased, thus stimulating business enterprise. Jefferson\
hotly attacked the bank on the ground that Congress had no power\
whatever under the Constitution to charter such a private corporation.\
Hamilton defended it with great cogency. Washington, after weighing all\
opinions, decided in favor of the proposal. In 1791 the bill\
establishing the first United States Bank for a period of twenty years\
became a law.\
\
=The Protective Tariff.=--A third part of Hamilton's program was the\
protection of American industries. The first revenue act of 1789, though\
designed primarily to bring money into the empty treasury, declared in\
favor of the principle. The following year Washington referred to the\
subject in his address to Congress. Thereupon Hamilton was instructed to\
prepare recommendations for legislative action. The result, after a\
delay of more than a year, was his _Report on Manufactures_, another\
state paper worthy, in closeness of reasoning and keenness of\
understanding, of a place beside his report on public credit. Hamilton\
based his argument on the broadest national grounds: the protective\
tariff would, by encouraging the building of factories, create a home\
market for the produce of farms and plantations; by making the United\
States independent of other countries in times of peace, it would double\
its security in time of war; by making use of the labor of women and\
children, it would turn to the production of goods persons otherwise\
idle or only partly employed; by increasing the trade between the North\
and South it would strengthen the links of union and add to political\
ties those of commerce and intercourse. The revenue measure of 1792 bore\
the impress of these arguments.\
\
\
THE RISE OF POLITICAL PARTIES\
\
=Dissensions over Hamilton's Measures.=--Hamilton's plans, touching\
deeply as they did the resources of individuals and the interests of the\
states, awakened alarm and opposition. Funding at face value, said his\
critics, was a government favor to speculators; the assumption of state\
debts was a deep design to undermine the state governments; Congress had\
no constitutional power to create a bank; the law creating the bank\
merely allowed a private corporation to make paper money and lend it at\
a high rate of interest; and the tariff was a tax on land and labor for\
the benefit of manufacturers.\
\
Hamilton's reply to this bill of indictment was simple and\
straightforward. Some rascally speculators had profited from the funding\
of the debt at face value, but that was only an incident in the\
restoration of public credit. In view of the jealousies of the states it\
was a good thing to reduce their powers and pretensions. The\
Constitution was not to be interpreted narrowly but in the full light of\
national needs. The bank would enlarge the amount of capital so sorely\
needed to start up American industries, giving markets to farmers and\
planters. The tariff by creating a home market and increasing\
opportunities for employment would benefit both land and labor. Out of\
such wise policies firmly pursued by the government, he concluded, were\
bound to come strength and prosperity for the new government at home,\
credit and power abroad. This view Washington fully indorsed, adding\
the weight of his great name to the inherent merits of the measures\
adopted under his administration.\
\
=The Sharpness of the Partisan Conflict.=--As a result of the clash of\
opinion, the people of the country gradually divided into two parties:\
Federalists and Anti-Federalists, the former led by Hamilton, the latter\
by Jefferson. The strength of the Federalists lay in the cities--Boston,\
Providence, Hartford, New York, Philadelphia, Charleston--among the\
manufacturing, financial, and commercial groups of the population who\
were eager to extend their business operations. The strength of the\
Anti-Federalists lay mainly among the debt-burdened farmers who feared\
the growth of what they called "a money power" and planters in all\
sections who feared the dominance of commercial and manufacturing\
interests. The farming and planting South, outside of the few towns,\
finally presented an almost solid front against assumption, the bank,\
and the tariff. The conflict between the parties grew steadily in\
bitterness, despite the conciliatory and engaging manner in which\
Hamilton presented his cause in his state papers and despite the\
constant efforts of Washington to soften the asperity of the\
contestants.\
\
=The Leadership and Doctrines of Jefferson.=--The party dispute had not\
gone far before the opponents of the administration began to look to\
Jefferson as their leader. Some of Hamilton's measures he had approved,\
declaring afterward that he did not at the time understand their\
significance. Others, particularly the bank, he fiercely assailed. More\
than once, he and Hamilton, shaking violently with anger, attacked each\
other at cabinet meetings, and nothing short of the grave and dignified\
pleas of Washington prevented an early and open break between them. In\
1794 it finally came. Jefferson resigned as Secretary of State and\
retired to his home in Virginia to assume, through correspondence and\
negotiation, the leadership of the steadily growing party of opposition.\
\
Shy and modest in manner, halting in speech, disliking the turmoil of\
public debate, and deeply interested in science and philosophy,\
Jefferson was not very well fitted for the strenuous life of political\
contest. Nevertheless, he was an ambitious and shrewd negotiator. He was\
also by honest opinion and matured conviction the exact opposite of\
Hamilton. The latter believed in a strong, active, "high-toned"\
government, vigorously compelling in all its branches. Jefferson looked\
upon such government as dangerous to the liberties of citizens and\
openly avowed his faith in the desirability of occasional popular\
uprisings. Hamilton distrusted the people. "Your people is a great\
beast," he is reported to have said. Jefferson professed his faith in\
the people with an abandon that was considered reckless in his time.\
\
On economic matters, the opinions of the two leaders were also\
hopelessly at variance. Hamilton, while cherishing agriculture, desired\
to see America a great commercial and industrial nation. Jefferson was\
equally set against this course for his country. He feared the\
accumulation of riches and the growth of a large urban working class.\
The mobs of great cities, he said, are sores on the body politic;\
artisans are usually the dangerous element that make revolutions;\
workshops should be kept in Europe and with them the artisans with their\
insidious morals and manners. The only substantial foundation for a\
republic, Jefferson believed to be agriculture. The spirit of\
independence could be kept alive only by free farmers, owning the land\
they tilled and looking to the sun in heaven and the labor of their\
hands for their sustenance. Trusting as he did in the innate goodness of\
human nature when nourished on a free soil, Jefferson advocated those\
measures calculated to favor agriculture and to enlarge the rights of\
persons rather than the powers of government. Thus he became the\
champion of the individual against the interference of the government,\
and an ardent advocate of freedom of the press, freedom of speech, and\
freedom of scientific inquiry. It was, accordingly, no mere factious\
spirit that drove him into opposition to Hamilton.\
\
=The Whisky Rebellion.=--The political agitation of the Anti-Federalists\
was accompanied by an armed revolt against the government in 1794. The\
occasion for this uprising was another of Hamilton's measures, a law\
laying an excise tax on distilled spirits, for the purpose of increasing\
the revenue needed to pay the interest on the funded debt. It so\
happened that a very considerable part of the whisky manufactured in the\
country was made by the farmers, especially on the frontier, in their\
own stills. The new revenue law meant that federal officers would now\
come into the homes of the people, measure their liquor, and take the\
tax out of their pockets. All the bitterness which farmers felt against\
the fiscal measures of the government was redoubled. In the western\
districts of Pennsylvania, Virginia, and North Carolina, they refused to\
pay the tax. In Pennsylvania, some of them sacked and burned the houses\
of the tax collectors, as the Revolutionists thirty years before had\
mobbed the agents of King George sent over to sell stamps. They were in\
a fair way to nullify the law in whole districts when Washington called\
out the troops to suppress "the Whisky Rebellion." Then the movement\
collapsed; but it left behind a deep-seated resentment which flared up\
in the election of several obdurate Anti-Federalist Congressmen from the\
disaffected regions.\
\
\
FOREIGN INFLUENCES AND DOMESTIC POLITICS\
\
=The French Revolution.=--In this exciting period, when all America was\
distracted by partisan disputes, a storm broke in Europe--the\
epoch-making French Revolution--which not only shook the thrones of the\
Old World but stirred to its depths the young republic of the New World.\
The first scene in this dramatic affair occurred in the spring of 1789,\
a few days after Washington was inaugurated. The king of France, Louis\
XVI, driven into bankruptcy by extravagance and costly wars, was forced\
to resort to his people for financial help. Accordingly he called, for\
the first time in more than one hundred fifty years, a meeting of the\
national parliament, the "Estates General," composed of representatives\
of the "three estates"--the clergy, nobility, and commoners. Acting\
under powerful leaders, the commoners, or "third estate," swept aside\
the clergy and nobility and resolved themselves into a national\
assembly. This stirred the country to its depths.\
\
[Illustration: _From an old print_\
\
LOUIS XVI IN THE HANDS OF THE MOB]\
\
Great events followed in swift succession. On July 14, 1789, the\
Bastille, an old royal prison, symbol of the king's absolutism, was\
stormed by a Paris crowd and destroyed. On the night of August 4, the\
feudal privileges of the nobility were abolished by the national\
assembly amid great excitement. A few days later came the famous\
Declaration of the Rights of Man, proclaiming the sovereignty of the\
people and the privileges of citizens. In the autumn of 1791, Louis XVI\
was forced to accept a new constitution for France vesting the\
legislative power in a popular assembly. Little disorder accompanied\
these startling changes. To all appearances a peaceful revolution had\
stripped the French king of his royal prerogatives and based the\
government of his country on the consent of the governed.\
\
=American Influence in France.=--In undertaking their great political\
revolt the French had been encouraged by the outcome of the American\
Revolution. Officers and soldiers, who had served in the American war,\
reported to their French countrymen marvelous tales. At the frugal table\
of General Washington, in council with the unpretentious Franklin, or at\
conferences over the strategy of war, French noblemen of ancient lineage\
learned to respect both the talents and the simple character of the\
leaders in the great republican commonwealth beyond the seas. Travelers,\
who had gone to see the experiment in republicanism with their own eyes,\
carried home to the king and ruling class stories of an astounding\
system of popular government.\
\
On the other hand the dalliance with American democracy was regarded by\
French conservatives as playing with fire. "When we think of the false\
ideas of government and philanthropy," wrote one of Lafayette's aides,\
"which these youths acquired in America and propagated in France with so\
much enthusiasm and such deplorable success--for this mania of imitation\
powerfully aided the Revolution, though it was not the sole cause of\
it--we are bound to confess that it would have been better, both for\
themselves and for us, if these young philosophers in red-heeled shoes\
had stayed at home in attendance on the court."\
\
=Early American Opinion of the French Revolution.=--So close were the\
ties between the two nations that it is not surprising to find every\
step in the first stages of the French Revolution greeted with applause\
in the United States. "Liberty will have another feather in her cap,"\
exultantly wrote a Boston editor. "In no part of the globe," soberly\
wrote John Marshall, "was this revolution hailed with more joy than in\
America.... But one sentiment existed." The main key to the Bastille,\
sent to Washington as a memento, was accepted as "a token of the\
victory gained by liberty." Thomas Paine saw in the great event "the\
first ripe fruits of American principles transplanted into Europe."\
Federalists and Anti-Federalists regarded the new constitution of France\
as another vindication of American ideals.\
\
=The Reign of Terror.=--While profuse congratulations were being\
exchanged, rumors began to come that all was not well in France. Many\
noblemen, enraged at the loss of their special privileges, fled into\
Germany and plotted an invasion of France to overthrow the new system of\
government. Louis XVI entered into negotiations with his brother\
monarchs on the continent to secure their help in the same enterprise,\
and he finally betrayed to the French people his true sentiments by\
attempting to escape from his kingdom, only to be captured and taken\
back to Paris in disgrace.\
\
A new phase of the revolution now opened. The working people, excluded\
from all share in the government by the first French constitution,\
became restless, especially in Paris. Assembling on the Champs de Mars,\
a great open field, they signed a petition calling for another\
constitution giving them the suffrage. When told to disperse, they\
refused and were fired upon by the national guard. This "massacre," as\
it was called, enraged the populace. A radical party, known as\
"Jacobins," then sprang up, taking its name from a Jacobin monastery in\
which it held its sessions. In a little while it became the master of\
the popular convention convoked in September, 1792. The monarchy was\
immediately abolished and a republic established. On January 21, 1793,\
Louis was sent to the scaffold. To the war on Austria, already raging,\
was added a war on England. Then came the Reign of Terror, during which\
radicals in possession of the convention executed in large numbers\
counter-revolutionists and those suspected of sympathy with the\
monarchy. They shot down peasants who rose in insurrection against their\
rule and established a relentless dictatorship. Civil war followed.\
Terrible atrocities were committed on both sides in the name of liberty,\
and in the name of monarchy. To Americans of conservative temper it now\
seemed that the Revolution, so auspiciously begun, had degenerated into\
anarchy and mere bloodthirsty strife.\
\
=Burke Summons the World to War on France.=--In England, Edmund Burke\
led the fight against the new French principles which he feared might\
spread to all Europe. In his _Reflections on the French Revolution_,\
written in 1790, he attacked with terrible wrath the whole program of\
popular government; he called for war, relentless war, upon the French\
as monsters and outlaws; he demanded that they be reduced to order by\
the restoration of the king to full power under the protection of the\
arms of European nations.\
\
=Paine's Defense of the French Revolution.=--To counteract the campaign\
of hate against the French, Thomas Paine replied to Burke in another of\
his famous tracts, _The Rights of Man_, which was given to the American\
public in an edition containing a letter of approval from Jefferson.\
Burke, said Paine, had been mourning about the glories of the French\
monarchy and aristocracy but had forgotten the starving peasants and the\
oppressed people; had wept over the plumage and neglected the dying\
bird. Burke had denied the right of the French people to choose their\
own governors, blandly forgetting that the English government in which\
he saw final perfection itself rested on two revolutions. He had boasted\
that the king of England held his crown in contempt of the democratic\
societies. Paine answered: "If I ask a man in America if he wants a\
king, he retorts and asks me if I take him for an idiot." To the charge\
that the doctrines of the rights of man were "new fangled," Paine\
replied that the question was not whether they were new or old but\
whether they were right or wrong. As to the French disorders and\
difficulties, he bade the world wait to see what would be brought forth\
in due time.\
\
=The Effect of the French Revolution on American Politics.=--The course\
of the French Revolution and the controversies accompanying it,\
exercised a profound influence on the formation of the first political\
parties in America. The followers of Hamilton, now proud of the name\
"Federalists," drew back in fright as they heard of the cruel deeds\
committed during the Reign of Terror. They turned savagely upon the\
revolutionists and their friends in America, denouncing as "Jacobin"\
everybody who did not condemn loudly enough the proceedings of the\
French Republic. A Massachusetts preacher roundly assailed "the\
atheistical, anarchical, and in other respects immoral principles of the\
French Republicans"; he then proceeded with equal passion to attack\
Jefferson and the Anti-Federalists, whom he charged with spreading false\
French propaganda and betraying America. "The editors, patrons, and\
abettors of these vehicles of slander," he exclaimed, "ought to be\
considered and treated as enemies to their country.... Of all traitors\
they are the most aggravatedly criminal; of all villains, they are the\
most infamous and detestable."\
\
The Anti-Federalists, as a matter of fact, were generally favorable to\
the Revolution although they deplored many of the events associated with\
it. Paine's pamphlet, indorsed by Jefferson, was widely read. Democratic\
societies, after the fashion of French political clubs, arose in the\
cities; the coalition of European monarchs against France was denounced\
as a coalition against the very principles of republicanism; and the\
execution of Louis XVI was openly celebrated at a banquet in\
Philadelphia. Harmless titles, such as "Sir," "the Honorable," and "His\
Excellency," were decried as aristocratic and some of the more excited\
insisted on adopting the French title, "Citizen," speaking, for example,\
of "Citizen Judge" and "Citizen Toastmaster." Pamphlets in defense of\
the French streamed from the press, while subsidized newspapers kept the\
propaganda in full swing.\
\
=The European War Disturbs American Commerce.=--This battle of wits, or\
rather contest in calumny, might have gone on indefinitely in America\
without producing any serious results, had it not been for the war\
between England and France, then raging. The English, having command of\
the seas, claimed the right to seize American produce bound for French\
ports and to confiscate American ships engaged in carrying French goods.\
Adding fuel to a fire already hot enough, they began to search American\
ships and to carry off British-born sailors found on board American\
vessels.\
\
=The French Appeal for Help.=--At the same time the French Republic\
turned to the United States for aid in its war on England and sent over\
as its diplomatic representative "Citizen" Genet, an ardent supporter of\
the new order. On his arrival at Charleston, he was greeted with fervor\
by the Anti-Federalists. As he made his way North, he was wined and\
dined and given popular ovations that turned his head. He thought the\
whole country was ready to join the French Republic in its contest with\
England. Genet therefore attempted to use the American ports as the base\
of operations for French privateers preying on British merchant ships;\
and he insisted that the United States was in honor bound to help France\
under the treaty of 1778.\
\
=The Proclamation of Neutrality and the Jay Treaty.=--Unmoved by the\
\
rising tide of popular sympathy for France, Washington took a firm\
course. He received Genet coldly. The demand that the United States aid\
France under the old treaty of alliance he answered by proclaiming the\
neutrality of America and warning American citizens against hostile acts\
toward either France or England. When Genet continued to hold meetings,\
issue manifestoes, and stir up the people against England, Washington\
asked the French government to recall him. This act he followed up by\
sending the Chief Justice, John Jay, on a pacific mission to England.\
\
The result was the celebrated Jay treaty of 1794. By its terms Great\
Britain agreed to withdraw her troops from the western forts where they\
had been since the war for independence and to grant certain slight\
trade concessions. The chief sources of bitterness--the failure of the\
British to return slaves carried off during the Revolution, the seizure\
of American ships, and the impressment of sailors--were not touched,\
much to the distress of everybody in America, including loyal\
Federalists. Nevertheless, Washington, dreading an armed conflict with\
England, urged the Senate to ratify the treaty. The weight of his\
influence carried the day.\
\
At this, the hostility of the Anti-Federalists knew no bounds. Jefferson\
declared the Jay treaty "an infamous act which is really nothing more\
than an alliance between England and the Anglo-men of this country,\
against the legislature and the people of the United States." Hamilton,\
defending it with his usual courage, was stoned by a mob in New York and\
driven from the platform with blood streaming from his face. Jay was\
burned in effigy. Even Washington was not spared. The House of\
Representatives was openly hostile. To display its feelings, it called\
upon the President for the papers relative to the treaty negotiations,\
only to be more highly incensed by his flat refusal to present them, on\
the ground that the House did not share in the treaty-making power.\
\
=Washington Retires from Politics.=--Such angry contests confirmed the\
President in his slowly maturing determination to retire at the end of\
his second term in office. He did not believe that a third term was\
unconstitutional or improper; but, worn out by his long and arduous\
labors in war and in peace and wounded by harsh attacks from former\
friends, he longed for the quiet of his beautiful estate at Mount\
Vernon.\
\
In September, 1796, on the eve of the presidential election, Washington\
issued his Farewell Address, another state paper to be treasured and\
read by generations of Americans to come. In this address he directed\
the attention of the people to three subjects of lasting interest. He\
warned them against sectional jealousies. He remonstrated against the\
spirit of partisanship, saying that in government "of the popular\
character, in government purely elective, it is a spirit not to be\
encouraged." He likewise cautioned the people against "the insidious\
wiles of foreign influence," saying: "Europe has a set of primary\
interests which to us have none or a very remote relation. Hence she\
must be engaged in frequent controversies, the causes of which are\
essentially foreign to our concerns. Hence, therefore, it would be\
unwise in us to implicate ourselves, by artificial ties, in the ordinary\
vicissitudes of her politics or the ordinary combinations and collisions\
of her friendships or enmities.... Why forego the advantages of so\
peculiar a situation?... It is our true policy to steer clear of\
permanent alliances with any portion of the foreign world.... Taking\
care always to keep ourselves, by suitable establishments, on a\
respectable defensive posture, we may safely trust to temporary\
alliances for extraordinary emergencies."\
\
=The Campaign of 1796--Adams Elected.=--On hearing of the retirement of\
Washington, the Anti-Federalists cast off all restraints. In honor of\
France and in opposition to what they were pleased to call the\
monarchical tendencies of the Federalists, they boldly assumed the name\
"Republican"; the term "Democrat," then applied only to obscure and\
despised radicals, had not come into general use. They selected\
Jefferson as their candidate for President against John Adams, the\
Federalist nominee, and carried on such a spirited campaign that they\
came within four votes of electing him.\
\
The successful candidate, Adams, was not fitted by training or opinion\
for conciliating a determined opposition. He was a reserved and studious\
man. He was neither a good speaker nor a skillful negotiator. In one of\
his books he had declared himself in favor of "government by an\
aristocracy of talents and wealth"--an offense which the Republicans\
never forgave. While John Marshall found him "a sensible, plain, candid,\
good-tempered man," Jefferson could see in him nothing but a "monocrat"\
and "Anglo-man." Had it not been for the conduct of the French\
government, Adams would hardly have enjoyed a moment's genuine\
popularity during his administration.\
\
=The Quarrel with France.=--The French Directory, the executive\
department established under the constitution of 1795, managed, however,\
to stir the anger of Republicans and Federalists alike. It regarded the\
Jay treaty as a rebuke to France and a flagrant violation of obligations\
solemnly registered in the treaty of 1778. Accordingly it refused to\
receive the American minister, treated him in a humiliating way, and\
finally told him to leave the country. Overlooking this affront in his\
anxiety to maintain peace, Adams dispatched to France a commission of\
eminent men with instructions to reach an understanding with the French\
Republic. On their arrival, they were chagrined to find, instead of a\
decent reception, an indirect demand for an apology respecting the past\
conduct of the American government, a payment in cash, and an annual\
tribute as the price of continued friendship. When the news of this\
affair reached President Adams, he promptly laid it before Congress,\
referring to the Frenchmen who had made the demands as "Mr. X, Mr. Y,\
and Mr. Z."\
\
This insult, coupled with the fact that French privateers, like the\
British, were preying upon American commerce, enraged even the\
Republicans who had been loudest in the profession of their French\
sympathies. They forgot their wrath over the Jay treaty and joined with\
the Federalists in shouting: "Millions for defense, not a cent for\
tribute!" Preparations for war were made on every hand. Washington was\
once more called from Mount Vernon to take his old position at the head\
of the army. Indeed, fighting actually began upon the high seas and went\
on without a formal declaration of war until the year 1800. By that time\
the Directory had been overthrown. A treaty was readily made with\
Napoleon, the First Consul, who was beginning his remarkable career as\
chief of the French Republic, soon to be turned into an empire.\
\
=Alien and Sedition Laws.=--Flushed with success, the Federalists\
determined, if possible, to put an end to radical French influence in\
America and to silence Republican opposition. They therefore passed two\
drastic laws in the summer of 1798: the Alien and Sedition Acts.\
\
The first of these measures empowered the President to expel from the\
country or to imprison any alien whom he regarded as "dangerous" or "had\
reasonable grounds to suspect" of "any treasonable or secret\
machinations against the government."\
\
The second of the measures, the Sedition Act, penalized not only those\
who attempted to stir up unlawful combinations against the government\
but also every one who wrote, uttered, or published "any false,\
scandalous, and malicious writing ... against the government of the\
United States or either House of Congress, or the President of the\
United States, with intent to defame said government ... or to bring\
them or either of them into contempt or disrepute." This measure was\
hurried through Congress in spite of the opposition and the clear\
provision in the Constitution that Congress shall make no law abridging\
the freedom of speech or of the press. Even many Federalists feared the\
consequences of the action. Hamilton was alarmed when he read the bill,\
exclaiming: "Let us not establish a tyranny. Energy is a very different\
thing from violence." John Marshall told his friends in Virginia that,\
had he been in Congress, he would have opposed the two bills because he\
thought them "useless" and "calculated to create unnecessary discontents\
and jealousies."\
\
The Alien law was not enforced; but it gave great offense to the Irish\
and French whose activities against the American government's policy\
respecting Great Britain put them in danger of prison. The Sedition law,\
on the other hand, was vigorously applied. Several editors of Republican\
newspapers soon found themselves in jail or broken by ruinous fines for\
their caustic criticisms of the Federalist President and his policies.\
Bystanders at political meetings, who uttered sentiments which, though\
ungenerous and severe, seem harmless enough now, were hurried before\
Federalist judges and promptly fined and imprisoned. Although the\
prosecutions were not numerous, they aroused a keen resentment. The\
Republicans were convinced that their political opponents, having\
saddled upon the country Hamilton's fiscal system and the British\
treaty, were bent on silencing all censure. The measures therefore had\
exactly the opposite effect from that which their authors intended.\
Instead of helping the Federalist party, they made criticism of it more\
bitter than ever.\
\
=The Kentucky and Virginia Resolutions.=--Jefferson was quick to take\
advantage of the discontent. He drafted a set of resolutions declaring\
the Sedition law null and void, as violating the federal Constitution.\
His resolutions were passed by the Kentucky legislature late in 1798,\
signed by the governor, and transmitted to the other states for their\
consideration. Though receiving unfavorable replies from a number of\
Northern states, Kentucky the following year reaffirmed its position and\
declared that the nullification of all unconstitutional acts of Congress\
was the rightful remedy to be used by the states in the redress of\
grievances. It thus defied the federal government and announced a\
doctrine hostile to nationality and fraught with terrible meaning for\
the future. In the neighboring state of Virginia, Madison led a movement\
against the Alien and Sedition laws. He induced the legislature to pass\
resolutions condemning the acts as unconstitutional and calling upon the\
other states to take proper means to preserve their rights and the\
rights of the people.\
\
=The Republican Triumph in 1800.=--Thus the way was prepared for the\
election of 1800. The Republicans left no stone unturned in their\
efforts to place on the Federalist candidate, President Adams, all the\
odium of the Alien and Sedition laws, in addition to responsibility for\
approving Hamilton's measures and policies. The Federalists, divided in\
councils and cold in their affection for Adams, made a poor campaign.\
They tried to discredit their opponents with epithets of "Jacobins" and\
"Anarchists"--terms which had been weakened by excessive use. When the\
vote was counted, it was found that Adams had been defeated; while the\
Republicans had carried the entire South and New York also and secured\
eight of the fifteen electoral votes cast by Pennsylvania. "Our beloved\
Adams will now close his bright career," lamented a Federalist\
newspaper. "Sons of faction, demagogues and high priests of anarchy, now\
you have cause to triumph!"\
\
[Illustration: _An old cartoon_\
\
A QUARREL BETWEEN A FEDERALIST AND A REPUBLICAN IN THE HOUSE OF\
REPRESENTATIVES]\
\
Jefferson's election, however, was still uncertain. By a curious\
provision in the Constitution, presidential electors were required to\
vote for two persons without indicating which office each was to fill,\
the one receiving the highest number of votes to be President and the\
candidate standing next to be Vice President. It so happened that Aaron\
Burr, the Republican candidate for Vice President, had received the same\
number of votes as Jefferson; as neither had a majority the election was\
thrown into the House of Representatives, where the Federalists held the\
balance of power. Although it was well known that Burr was not even a\
candidate for President, his friends and many Federalists began\
intriguing for his election to that high office. Had it not been for the\
vigorous action of Hamilton the prize might have been snatched out of\
Jefferson's hands. Not until the thirty-sixth ballot on February 17,\
1801, was the great issue decided in his favor.[2]\
\
\
=References=\
\
J.S. Bassett, _The Federalist System_ (American Nation Series).\
\
C.A. Beard, _Economic Origins of Jeffersonian Democracy_.\
\
H. Lodge, _Alexander Hamilton_.\
\
J.T. Morse, _Thomas Jefferson_.\
\
\
=Questions=\
\
1. Who were the leaders in the first administration under the\
Constitution?\
\
2. What step was taken to appease the opposition?\
\
3. Enumerate Hamilton's great measures and explain each in detail.\
\
4. Show the connection between the parts of Hamilton's system.\
\
5. Contrast the general political views of Hamilton and Jefferson.\
\
6. What were the important results of the "peaceful" French Revolution\
(1789-92)?\
\
7. Explain the interaction of opinion between France and the United\
States.\
\
8. How did the "Reign of Terror" change American opinion?\
\
9. What was the Burke-Paine controversy?\
\
10. Show how the war in Europe affected American commerce and involved\
America with England and France.\
\
11. What were American policies with regard to each of those countries?\
\
12. What was the outcome of the Alien and Sedition Acts?\
\
\
=Research Topics=\
\
=Early Federal Legislation.=--Coman, _Industrial History of the United\
States_, pp. 133-156; Elson, _History of the United States_, pp.\
341-348.\
\
=Hamilton's Report on Public Credit.=--Macdonald, _Documentary Source\
Book_, pp. 233-243.\
\
=The French Revolution.=--Robinson and Beard, _Development of Modern\
Europe_, Vol. I, pp. 224-282; Elson, pp. 351-354.\
\
=The Burke-Paine Controversy.=--Make an analysis of Burke's _Reflections\
on the French Revolution_ and Paine's _Rights of Man_.\
\
=The Alien and Sedition Acts.=--Macdonald, _Documentary Source Book_,\
pp. 259-267; Elson, pp. 367-375.\
\
=Kentucky and Virginia Resolutions.=--Macdonald, pp. 267-278.\
\
=Source Studies.=--Materials in Hart, _American History Told by\
Contemporaries_, Vol. III, pp. 255-343.\
\
=Biographical Studies.=--Alexander Hamilton, John Adams, Thomas\
Jefferson, and Albert Gallatin.\
\
=The Twelfth Amendment.=--Contrast the provision in the original\
Constitution with the terms of the Amendment. _See_ Appendix.\
\
FOOTNOTES:\
\
[1] North Carolina ratified in November, 1789, and Rhode Island in May,\
1790.\
\
[2] To prevent a repetition of such an unfortunate affair, the twelfth\
amendment of the Constitution was adopted in 1804, changing slightly the\
method of electing the President.\
\
\
\
\
CHAPTER IX\
\
THE JEFFERSONIAN REPUBLICANS IN POWER\
\
\
REPUBLICAN PRINCIPLES AND POLICIES\
\
=Opposition to Strong Central Government.=--Cherishing especially the\
agricultural interest, as Jefferson said, the Republicans were in the\
beginning provincial in their concern and outlook. Their attachment to\
America was, certainly, as strong as that of Hamilton; but they regarded\
the state, rather than the national government, as the proper center of\
power and affection. Indeed, a large part of the rank and file had been\
among the opponents of the Constitution in the days of its adoption.\
Jefferson had entertained doubts about it and Monroe, destined to be the\
fifth President, had been one of the bitter foes of ratification. The\
former went so far in the direction of local autonomy that he exalted\
the state above the nation in the Kentucky resolutions of 1798,\
declaring the Constitution to be a mere compact and the states competent\
to interpret and nullify federal law. This was provincialism with a\
vengeance. "It is jealousy, not confidence, which prescribes limited\
constitutions," wrote Jefferson for the Kentucky legislature. Jealousy\
of the national government, not confidence in it--this is the ideal that\
reflected the provincial and agricultural interest.\
\
=Republican Simplicity.=--Every act of the Jeffersonian party during its\
early days of power was in accord with the ideals of government which it\
professed. It had opposed all pomp and ceremony, calculated to give\
weight and dignity to the chief executive of the nation, as symbols of\
monarchy and high prerogative. Appropriately, therefore, Jefferson's\
inauguration on March 4, 1801, the first at the new capital at\
Washington, was marked by extreme simplicity. In keeping with this\
procedure he quit the practice, followed by Washington and Adams, of\
reading presidential addresses to Congress in joint assembly and adopted\
in its stead the plan of sending his messages in writing--a custom that\
was continued unbroken until 1913 when President Wilson returned to the\
example set by the first chief magistrate.\
\
=Republican Measures.=--The Republicans had complained of a great\
national debt as the source of a dangerous "money power," giving\
strength to the federal government; accordingly they began to pay it off\
as rapidly as possible. They had held commerce in low esteem and looked\
upon a large navy as a mere device to protect it; consequently they\
reduced the number of warships. They had objected to excise taxes,\
particularly on whisky; these they quickly abolished, to the intense\
satisfaction of the farmers. They had protested against the heavy cost\
of the federal government; they reduced expenses by discharging hundreds\
of men from the army and abolishing many offices.\
\
They had savagely criticized the Sedition law and Jefferson refused to\
enforce it. They had been deeply offended by the assault on freedom of\
speech and press and they promptly impeached Samuel Chase, a justice of\
the Supreme Court, who had been especially severe in his attacks upon\
offenders under the Sedition Act. Their failure to convict Justice Chase\
by a narrow margin was due to no lack of zeal on their part but to the\
Federalist strength in the Senate where the trial was held. They had\
regarded the appointment of a large number of federal judges during the\
last hours of Adams' administration as an attempt to intrench\
Federalists in the judiciary and to enlarge the sphere of the national\
government. Accordingly, they at once repealed the act creating the new\
judgeships, thus depriving the "midnight appointees" of their posts.\
They had considered the federal offices, civil and military, as sources\
of great strength to the Federalists and Jefferson, though committed to\
the principle that offices should be open to all and distributed\
according to merit, was careful to fill most of the vacancies as they\
occurred with trusted Republicans. To his credit, however, it must be\
said that he did not make wholesale removals to find room for party\
workers.\
\
The Republicans thus hewed to the line of their general policy of\
restricting the weight, dignity, and activity of the national\
government. Yet there were no Republicans, as the Federalists asserted,\
prepared to urge serious modifications in the Constitution. "If there be\
any among us who wish to dissolve this union or to change its republican\
form," wrote Jefferson in his first inaugural, "let them stand\
undisturbed as monuments of the safety with which error of opinion may\
be tolerated where reason is left free to combat it." After reciting the\
fortunate circumstances of climate, soil, and isolation which made the\
future of America so full of promise, Jefferson concluded: "A wise and\
frugal government which shall restrain men from injuring one another,\
shall leave them otherwise free to regulate their own pursuits of\
industry and improvement and shall not take from the mouth of labour the\
bread it has earned. This is the sum of good government; and this is\
necessary to close the circle of our felicities."\
\
In all this the Republicans had not reckoned with destiny. In a few\
short years that lay ahead it was their fate to double the territory of\
the country, making inevitable a continental nation; to give the\
Constitution a generous interpretation that shocked many a Federalist;\
to wage war on behalf of American commerce; to reestablish the hated\
United States Bank; to enact a high protective tariff; to see their\
Federalist opponents in their turn discredited as nullifiers and\
provincials; to announce high national doctrines in foreign affairs; and\
to behold the Constitution exalted and defended against the pretensions\
of states by a son of old Virginia, John Marshall, Chief Justice of the\
Supreme Court of the United States.\
\
\
THE REPUBLICANS AND THE GREAT WEST\
\
=Expansion and Land Hunger.=--The first of the great measures which\
drove the Republicans out upon this new national course--the purchase\
of the Louisiana territory--was the product of circumstances rather than\
of their deliberate choosing. It was not the lack of land for his\
cherished farmers that led Jefferson to add such an immense domain to\
the original possessions of the United States. In the Northwest\
territory, now embracing Ohio, Indiana, Illinois, Michigan, Wisconsin,\
and a portion of Minnesota, settlements were mainly confined to the\
north bank of the Ohio River. To the south, in Kentucky and Tennessee,\
where there were more than one hundred thousand white people who had\
pushed over the mountains from Virginia and the Carolinas, there were\
still wide reaches of untilled soil. The Alabama and Mississippi regions\
were vast Indian frontiers of the state of Georgia, unsettled and almost\
unexplored. Even to the wildest imagination there seemed to be territory\
enough to satisfy the land hunger of the American people for a century\
to come.\
\
=The Significance of the Mississippi River.=--At all events the East,\
then the center of power, saw no good reason for expansion. The planters\
of the Carolinas, the manufacturers of Pennsylvania, the importers of\
New York, the shipbuilders of New England, looking to the seaboard and\
to Europe for trade, refinements, and sometimes their ideas of\
government, were slow to appreciate the place of the West in national\
economy. The better educated the Easterners were, the less, it seems,\
they comprehended the destiny of the nation. Sons of Federalist fathers\
at Williams College, after a long debate decided by a vote of fifteen to\
one that the purchase of Louisiana was undesirable.\
\
On the other hand, the pioneers of Kentucky, Ohio, and Tennessee,\
unlearned in books, saw with their own eyes the resources of the\
wilderness. Many of them had been across the Mississippi and had beheld\
the rich lands awaiting the plow of the white man. Down the great river\
they floated their wheat, corn, and bacon to ocean-going ships bound for\
the ports of the seaboard or for Europe. The land journeys over the\
mountain barriers with bulky farm produce, they knew from experience,\
were almost impossible, and costly at best. Nails, bolts of cloth, tea,\
and coffee could go or come that way, but not corn and bacon. A free\
outlet to the sea by the Mississippi was as essential to the pioneers of\
the Kentucky region as the harbor of Boston to the merchant princes of\
that metropolis.\
\
=Louisiana under Spanish Rule.=--For this reason they watched with deep\
solicitude the fortunes of the Spanish king to whom, at the close of the\
Seven Years' War, had fallen the Louisiana territory stretching from New\
Orleans to the Rocky Mountains. While he controlled the mouth of the\
Mississippi there was little to fear, for he had neither the army nor\
the navy necessary to resist any invasion of American trade. Moreover,\
Washington had been able, by the exercise of great tact, to secure from\
Spain in 1795 a trading privilege through New Orleans which satisfied\
the present requirements of the frontiersmen even if it did not allay\
their fears for the future. So things stood when a swift succession of\
events altered the whole situation.\
\
=Louisiana Transferred to France.=--In July, 1802, a royal order from\
Spain instructed the officials at New Orleans to close the port to\
American produce. About the same time a disturbing rumor, long current,\
was confirmed--Napoleon had coerced Spain into returning Louisiana to\
France by a secret treaty signed in 1800. "The scalers of the Alps and\
conquerors of Venice" now looked across the sea for new scenes of\
adventure. The West was ablaze with excitement. A call for war ran\
through the frontier; expeditions were organized to prevent the landing\
of the French; and petitions for instant action flooded in upon\
Jefferson.\
\
=Jefferson Sees the Danger.=--Jefferson, the friend of France and sworn\
enemy of England, compelled to choose in the interest of America, never\
winced. "The cession of Louisiana and the Floridas by Spain to France,"\
he wrote to Livingston, the American minister in Paris, "works sorely on\
the United States. It completely reverses all the political relations of\
the United States and will form a new epoch in our political course....\
There is on the globe one single spot, the possessor of which is our\
natural and habitual enemy. It is New Orleans through which the produce\
of three-eighths of our territory must pass to market.... France,\
placing herself in that door, assumes to us an attitude of defiance.\
Spain might have retained it quietly for years. Her pacific\
dispositions, her feeble state would induce her to increase our\
facilities there.... Not so can it ever be in the hands of France....\
The day that France takes possession of New Orleans fixes the sentence\
which is to restrain her forever within her low water mark.... It seals\
the union of the two nations who in conjunction can maintain exclusive\
possession of the ocean. From that moment we must marry ourselves to the\
British fleet and nation.... This is not a state of things we seek or\
desire. It is one which this measure, if adopted by France, forces on us\
as necessarily as any other cause by the laws of nature brings on its\
necessary effect."\
\
=Louisiana Purchased.=--Acting on this belief, but apparently seeing\
only the Mississippi outlet at stake, Jefferson sent his friend, James\
Monroe, to France with the power to buy New Orleans and West Florida.\
Before Monroe arrived, the regular minister, Livingston, had already\
convinced Napoleon that it would be well to sell territory which might\
be wrested from him at any moment by the British sea power, especially\
as the war, temporarily stopped by the peace of Amiens, was once more\
raging in Europe. Wise as he was in his day, Livingston had at first no\
thought of buying the whole Louisiana country. He was simply dazed when\
Napoleon offered to sell the entire domain and get rid of the business\
altogether. Though staggered by the proposal, he and Monroe decided to\
accept. On April 30, they signed the treaty of cession, agreeing to pay\
$11,250,000 in six per cent bonds and to discharge certain debts due\
French citizens, making in all approximately fifteen millions. Spain\
protested, Napoleon's brother fumed, French newspapers objected; but the\
deed was done.\
\
=Jefferson and His Constitutional Scruples.=--When the news of this\
extraordinary event reached the United States, the people were filled\
with astonishment, and no one was more surprised than Jefferson himself.\
He had thought of buying New Orleans and West Florida for a small sum,\
and now a vast domain had been dumped into the lap of the nation. He was\
puzzled. On looking into the Constitution he found not a line\
authorizing the purchase of more territory and so he drafted an\
amendment declaring "Louisiana, as ceded by France,--a part of the\
United States." He had belabored the Federalists for piling up a big\
national debt and he could hardly endure the thought of issuing more\
bonds himself.\
\
In the midst of his doubts came the news that Napoleon might withdraw\
from the bargain. Thoroughly alarmed by that, Jefferson pressed the\
Senate for a ratification of the treaty. He still clung to his original\
idea that the Constitution did not warrant the purchase; but he lamely\
concluded: "If our friends shall think differently, I shall certainly\
acquiesce with satisfaction; confident that the good sense of our\
country will correct the evil of construction when it shall produce ill\
effects." Thus the stanch advocate of "strict interpretation" cut loose\
from his own doctrine and intrusted the construction of the Constitution\
to "the good sense" of his countrymen.\
\
=The Treaty Ratified.=--This unusual transaction, so favorable to the\
West, aroused the ire of the seaboard Federalists. Some denounced it as\
unconstitutional, easily forgetting Hamilton's masterly defense of the\
bank, also not mentioned in the Constitution. Others urged that, if "the\
howling wilderness" ever should be settled, it would turn against the\
East, form new commercial connections, and escape from federal control.\
Still others protested that the purchase would lead inevitably to the\
dominance of a "hotch potch of wild men from the Far West." Federalists,\
who thought "the broad back of America" could readily bear Hamilton's\
consolidated debt, now went into agonies over a bond issue of less than\
one-sixth of that amount. But in vain. Jefferson's party with a high\
hand carried the day. The Senate, after hearing the Federalist protest,\
ratified the treaty. In December, 1803, the French flag was hauled down\
from the old government buildings in New Orleans and the Stars and\
Stripes were hoisted as a sign that the land of Coronado, De Soto,\
Marquette, and La Salle had passed forever to the United States.\
\
[Illustration: THE UNITED STATES IN 1805]\
\
By a single stroke, the original territory of the United States was more\
than doubled. While the boundaries of the purchase were uncertain, it is\
safe to say that the Louisiana territory included what is now Arkansas,\
Missouri, Iowa, Oklahoma, Kansas, Nebraska, South Dakota, and large\
portions of Louisiana, Minnesota, North Dakota, Colorado, Montana, and\
Wyoming. The farm lands that the friends of "a little America" on the\
seacoast declared a hopeless wilderness were, within a hundred years,\
fully occupied and valued at nearly seven billion dollars--almost five\
hundred times the price paid to Napoleon.\
\
=Western Explorations.=--Having taken the fateful step, Jefferson wisely\
began to make the most of it. He prepared for the opening of the new\
country by sending the Lewis and Clark expedition to explore it,\
discover its resources, and lay out an overland route through the\
Missouri Valley and across the Great Divide to the Pacific. The story of\
this mighty exploit, which began in the spring of 1804 and ended in the\
autumn of 1806, was set down with skill and pains in the journal of\
Lewis and Clark; when published even in a short form, it invited the\
forward-looking men of the East to take thought about the western\
empire. At the same time Zebulon Pike, in a series of journeys, explored\
the sources of the Mississippi River and penetrated the Spanish\
territories of the far Southwest. Thus scouts and pioneers continued the\
work of diplomats.\
\
\
THE REPUBLICAN WAR FOR COMMERCIAL INDEPENDENCE\
\
=The English and French Blockades.=--In addition to bringing Louisiana\
to the United States, the reopening of the European War in 1803, after a\
short lull, renewed in an acute form the commercial difficulties that\
had plagued the country all during the administrations of Washington and\
Adams. The Republicans were now plunged into the hornets' nest. The\
party whose ardent spirits had burned Jay in effigy, stoned Hamilton for\
defending his treaty, jeered Washington's proclamation of neutrality,\
and spoken bitterly of "timid traders," could no longer take refuge in\
criticism. It had to act.\
\
Its troubles took a serious turn in 1806. England, in a determined\
effort to bring France to her knees by starvation, declared the coast of\
Europe blockaded from Brest to the mouth of the Elbe River. Napoleon\
retaliated by his Berlin Decree of November, 1806, blockading the\
British Isles--a measure terrifying to American ship owners whose\
vessels were liable to seizure by any French rover, though Napoleon had\
no navy to make good his proclamation. Great Britain countered with a\
still more irritating decree--the Orders in Council of 1807. It modified\
its blockade, but in so doing merely authorized American ships not\
carrying munitions of war to complete their voyage to the Continent, on\
condition of their stopping at a British port, securing a license, and\
paying a tax. This, responded Napoleon, was the height of insolence, and\
he denounced it as a gross violation of international law. He then\
closed the circle of American troubles by issuing his Milan Decree of\
December, 1807. This order declared that any ship which complied with\
the British rules would be subject to seizure and confiscation by French\
authorities.\
\
=The Impressment of Seamen.=--That was not all. Great Britain, in dire\
need of men for her navy, adopted the practice of stopping American\
ships, searching them, and carrying away British-born sailors found on\
board. British sailors were so badly treated, so cruelly flogged for\
trivial causes, and so meanly fed that they fled in crowds to the\
American marine. In many cases it was difficult to tell whether seamen\
were English or American. They spoke the same language, so that language\
was no test. Rovers on the deep and stragglers in the ports of both\
countries, they frequently had no papers to show their nativity.\
Moreover, Great Britain held to the old rule--"Once an Englishman,\
always an Englishman"--a doctrine rejected by the United States in\
favor of the principle that a man could choose the nation to which he\
would give allegiance. British sea captains, sometimes by mistake, and\
often enough with reckless indifference, carried away into servitude in\
their own navy genuine American citizens. The process itself, even when\
executed with all the civilities of law, was painful enough, for it\
meant that American ships were forced to "come to," and compelled to\
rest submissively under British guns until the searching party had pried\
into records, questioned seamen, seized and handcuffed victims. Saints\
could not have done this work without raising angry passions, and only\
saints could have endured it with patience and fortitude.\
\
Had the enactment of the scenes been confined to the high seas and\
knowledge of them to rumors and newspaper stories, American resentment\
might not have been so intense; but many a search and seizure was made\
in sight of land. British and French vessels patrolled the coasts,\
firing on one another and chasing one another in American waters within\
the three-mile limit. When, in the summer of 1807, the American frigate\
_Chesapeake_ refused to surrender men alleged to be deserters from King\
George's navy, the British warship _Leopard_ opened fire, killing three\
men and wounding eighteen more--an act which even the British ministry\
could hardly excuse. If the French were less frequently the offenders,\
it was not because of their tenderness about American rights but because\
so few of their ships escaped the hawk-eyed British navy to operate in\
American waters.\
\
=The Losses in American Commerce.=--This high-handed conduct on the part\
of European belligerents was very injurious to American trade. By their\
enterprise, American shippers had become the foremost carriers on the\
Atlantic Ocean. In a decade they had doubled the tonnage of American\
merchant ships under the American flag, taking the place of the French\
marine when Britain swept that from the seas, and supplying Britain with\
the sinews of war for the contest with the Napoleonic empire. The\
American shipping engaged in foreign trade embraced 363,110 tons in\
1791; 669,921 tons in 1800; and almost 1,000,000 tons in 1810. Such was\
the enterprise attacked by the British and French decrees. American\
ships bound for Great Britain were liable to be captured by French\
privateers which, in spite of the disasters of the Nile and Trafalgar,\
ranged the seas. American ships destined for the Continent, if they\
failed to stop at British ports and pay tribute, were in great danger of\
capture by the sleepless British navy and its swarm of auxiliaries.\
American sea captains who, in fear of British vengeance, heeded the\
Orders in Council and paid the tax were almost certain to fall a prey to\
French vengeance, for the French were vigorous in executing the Milan\
Decree.\
\
=Jefferson's Policy.=--The President's dilemma was distressing. Both the\
belligerents in Europe were guilty of depredations on American commerce.\
War on both of them was out of the question. War on France was\
impossible because she had no territory on this side of the water which\
could be reached by American troops and her naval forces had been\
shattered at the battles of the Nile and Trafalgar. War on Great\
Britain, a power which Jefferson's followers feared and distrusted, was\
possible but not inviting. Jefferson shrank from it. A man of peace, he\
disliked war's brazen clamor; a man of kindly spirit, he was startled at\
the death and destruction which it brought in its train. So for the\
eight years Jefferson steered an even course, suggesting measure after\
measure with a view to avoiding bloodshed. He sent, it is true,\
Commodore Preble in 1803 to punish Mediterranean pirates preying upon\
American commerce; but a great war he evaded with passionate\
earnestness, trying in its place every other expedient to protect\
American rights.\
\
=The Embargo and Non-intercourse Acts.=--In 1806, Congress passed and\
Jefferson approved a non-importation act closing American ports to\
certain products from British dominions--a measure intended as a club\
over the British government's head. This law, failing in its purpose,\
Jefferson proposed and Congress adopted in December, 1807, the Embargo\
Act forbidding all vessels to leave American harbors for foreign ports.\
France and England were to be brought to terms by cutting off their\
supplies.\
\
The result of the embargo was pathetic. England and France refused to\
give up search and seizure. American ship owners who, lured by huge\
profits, had formerly been willing to take the risk were now restrained\
by law to their home ports. Every section suffered. The South and West\
found their markets for cotton, rice, tobacco, corn, and bacon\
curtailed. Thus they learned by bitter experience the national\
significance of commerce. Ship masters, ship builders, longshoremen, and\
sailors were thrown out of employment while the prices of foreign goods\
doubled. Those who obeyed the law were ruined; violators of the law\
smuggled goods into Canada and Florida for shipment abroad.\
\
Jefferson's friends accepted the medicine with a wry face as the only\
alternative to supine submission or open war. His opponents, without\
offering any solution of their own, denounced it as a contemptible plan\
that brought neither relief nor honor. Beset by the clamor that arose on\
all sides, Congress, in the closing days of Jefferson's administration,\
repealed the Embargo law and substituted a Non-intercourse act\
forbidding trade with England and France while permitting it with other\
countries--a measure equally futile in staying the depredations on\
American shipping.\
\
=Jefferson Retires in Favor of Madison.=--Jefferson, exhausted by\
endless wrangling and wounded, as Washington had been, by savage\
criticism, welcomed March 4, 1809. His friends urged him to "stay by the\
ship" and accept a third term. He declined, saying that election for\
life might result from repeated reelection. In following Washington's\
course and defending it on principle, he set an example to all his\
successors, making the "third term doctrine" a part of American\
unwritten law.\
\
His intimate friend, James Madison, to whom he turned over the burdens\
of his high office was, like himself, a man of peace. Madison had been a\
leader since the days of the Revolution, but in legislative halls and\
council chambers, not on the field of battle. Small in stature,\
sensitive in feelings, studious in habits, he was no man for the rough\
and tumble of practical politics. He had taken a prominent and\
distinguished part in the framing and the adoption of the Constitution.\
He had served in the first Congress as a friend of Hamilton's measures.\
Later he attached himself to Jefferson's fortunes and served for eight\
years as his first counselor, the Secretary of State. The principles of\
the Constitution, which he had helped to make and interpret, he was now\
as President called upon to apply in one of the most perplexing moments\
in all American history. In keeping with his own traditions and\
following in the footsteps of Jefferson, he vainly tried to solve the\
foreign problem by negotiation.\
\
=The Trend of Events.=--Whatever difficulties Madison had in making up\
his mind on war and peace were settled by events beyond his own control.\
In the spring of 1811, a British frigate held up an American ship near\
the harbor of New York and impressed a seaman alleged to be an American\
citizen. Burning with resentment, the captain of the _President_, an\
American warship, acting under orders, poured several broadsides into\
the _Little Belt_, a British sloop, suspected of being the guilty party.\
The British also encouraged the Indian chief Tecumseh, who welded\
together the Indians of the Northwest under British protection and gave\
signs of restlessness presaging a revolt. This sent a note of alarm\
along the frontier that was not checked even when, in November,\
Tecumseh's men were badly beaten at Tippecanoe by William Henry\
Harrison. The Indians stood in the way of the advancing frontier, and it\
seemed to the pioneers that, without support from the British in Canada,\
the Red Men would soon be subdued.\
\
=Clay and Calhoun.=--While events were moving swiftly and rumors were\
flying thick and fast, the mastery of the government passed from the\
uncertain hands of Madison to a party of ardent young men in Congress,\
dubbed "Young Republicans," under the leadership of two members destined\
to be mighty figures in American history: Henry Clay of Kentucky and\
John C. Calhoun of South Carolina. The former contended, in a flair of\
folly, that "the militia of Kentucky alone are competent to place\
Montreal and Upper Canada at your feet." The latter with a light heart\
spoke of conquering Canada in a four weeks' campaign. "It must not be\
inferred," says Channing, "that in advocating conquest, the Westerners\
were actuated merely by desire for land; they welcomed war because they\
\
thought it would be the easiest way to abate Indian troubles. The\
savages were supported by the fur-trading interests that centred at\
Quebec and London.... The Southerners on their part wished for Florida\
and they thought that the conquest of Canada would obviate some Northern\
opposition to this acquisition of slave territory." While Clay and\
Calhoun, spokesmen of the West and South, were not unmindful of what\
Napoleon had done to American commerce, they knew that their followers\
still remembered with deep gratitude the aid of the French in the war\
for independence and that the embers of the old hatred for George III,\
still on the throne, could be readily blown into flame.\
\
=Madison Accepts War as Inevitable.=--The conduct of the British\
ministers with whom Madison had to deal did little to encourage him in\
adhering to the policy of "watchful waiting." One of them, a high Tory,\
believed that all Americans were alike "except that a few are less\
knaves than others" and his methods were colored by his belief. On the\
recall of this minister the British government selected another no less\
high and mighty in his principles and opinions. So Madison became\
thoroughly discouraged about the outcome of pacific measures. When the\
pressure from Congress upon him became too heavy, he gave way, signing\
on June 18, 1812, the declaration of war on Great Britain. In\
proclaiming hostilities, the administration set forth the causes which\
justified the declaration; namely, the British had been encouraging the\
Indians to attack American citizens on the frontier; they had ruined\
American trade by blockades; they had insulted the American flag by\
stopping and searching our ships; they had illegally seized American\
sailors and driven them into the British navy.\
\
=The Course of the War.=--The war lasted for nearly three years without\
bringing victory to either side. The surrender of Detroit by General\
Hull to the British and the failure of the American invasion of Canada\
were offset by Perry's victory on Lake Erie and a decisive blow\
administered to British designs for an invasion of New York by way of\
Plattsburgh. The triumph of Jackson at New Orleans helped to atone for\
the humiliation suffered in the burning of the Capitol by the British.\
The stirring deeds of the _Constitution_, the _United States_, and the\
_Argus_ on the seas, the heroic death of Lawrence and the victories of a\
hundred privateers furnished consolation for those who suffered from the\
iron blockade finally established by the British government when it came\
to appreciate the gravity of the situation. While men love the annals of\
the sea, they will turn to the running battles, the narrow escapes, and\
the reckless daring of American sailors in that naval contest with Great\
Britain.\
\
All this was exciting but it was inconclusive. In fact, never was a\
government less prepared than was that of the United States in 1812. It\
had neither the disciplined troops, the ships of war, nor the supplies\
required by the magnitude of the military task. It was fortune that\
favored the American cause. Great Britain, harassed, worn, and\
financially embarrassed by nearly twenty years of fighting in Europe,\
was in no mood to gather her forces for a titanic effort in America even\
after Napoleon was overthrown and sent into exile at Elba in the spring\
of 1814. War clouds still hung on the European horizon and the conflict\
temporarily halted did again break out. To be rid of American anxieties\
and free for European eventualities, England was ready to settle with\
the United States, especially as that could be done without conceding\
anything or surrendering any claims.\
\
=The Treaty of Peace.=--Both countries were in truth sick of a war that\
offered neither glory nor profit. Having indulged in the usual\
diplomatic skirmishing, they sent representatives to Ghent to discuss\
terms of peace. After long negotiations an agreement was reached on\
Christmas eve, 1814, a few days before Jackson's victory at New Orleans.\
When the treaty reached America the people were surprised to find that\
it said nothing about the seizure of American sailors, the destruction\
of American trade, the searching of American ships, or the support of\
Indians on the frontier. Nevertheless, we are told, the people "passed\
from gloom to glory" when the news of peace arrived. The bells were\
rung; schools were closed; flags were displayed; and many a rousing\
toast was drunk in tavern and private home. The rejoicing could\
continue. With Napoleon definitely beaten at Waterloo in June, 1815,\
Great Britain had no need to impress sailors, search ships, and\
confiscate American goods bound to the Continent. Once more the terrible\
sea power sank into the background and the ocean was again white with\
the sails of merchantmen.\
\
\
THE REPUBLICANS NATIONALIZED\
\
=The Federalists Discredited.=--By a strange turn of fortune's wheel,\
the party of Hamilton, Washington, Adams, the party of the grand nation,\
became the party of provincialism and nullification. New England,\
finding its shipping interests crippled in the European conflict and\
then penalized by embargoes, opposed the declaration of war on Great\
Britain, which meant the completion of the ruin already begun. In the\
course of the struggle, the Federalist leaders came perilously near to\
treason in their efforts to hamper the government of the United States;\
and in their desperation they fell back upon the doctrine of\
nullification so recently condemned by them when it came from Kentucky.\
The Senate of Massachusetts, while the war was in progress, resolved\
that it was waged "without justifiable cause," and refused to approve\
military and naval projects not connected with "the defense of our\
seacoast and soil." A Boston newspaper declared that the union was\
nothing but a treaty among sovereign states, that states could decide\
for themselves the question of obeying federal law, and that armed\
resistance under the banner of a state would not be rebellion or\
treason. The general assembly of Connecticut reminded the administration\
at Washington that "the state of Connecticut is a free, sovereign, and\
independent state." Gouverneur Morris, a member of the convention which\
had drafted the Constitution, suggested the holding of another\
conference to consider whether the Northern states should remain in the\
union.\
\
[Illustration: _From an old cartoon_\
\
NEW ENGLAND JUMPING INTO THE HANDS OF GEORGE III]\
\
In October, 1814, a convention of delegates from Connecticut,\
Massachusetts, Rhode Island, and certain counties of New Hampshire and\
Vermont was held at Hartford, on the call of Massachusetts. The counsels\
of the extremists were rejected but the convention solemnly went on\
record to the effect that acts of Congress in violation of the\
Constitution are void; that in cases of deliberate, dangerous, and\
palpable infractions the state is duty bound to interpose its authority\
for the protection of its citizens; and that when emergencies occur the\
states must be their own judges and execute their own decisions. Thus\
New England answered the challenge of Calhoun and Clay. Fortunately its\
actions were not as rash as its words. The Hartford convention merely\
proposed certain amendments to the Constitution and adjourned. At the\
close of the war, its proposals vanished harmlessly; but the men who\
made them were hopelessly discredited.\
\
=The Second United States Bank.=--In driving the Federalists towards\
nullification and waging a national war themselves, the Republicans lost\
all their old taint of provincialism. Moreover, in turning to measures\
of reconstruction called forth by the war, they resorted to the national\
devices of the Federalists. In 1816, they chartered for a period of\
twenty years a second United States Bank--the institution which\
Jefferson and Madison once had condemned as unsound and\
unconstitutional. The Constitution remained unchanged; times and\
circumstances had changed. Calhoun dismissed the vexed question of\
constitutionality with a scant reference to an ancient dispute, while\
Madison set aside his scruples and signed the bill.\
\
=The Protective Tariff of 1816.=--The Republicans supplemented the Bank\
by another Federalist measure--a high protective tariff. Clay viewed it\
as the beginning of his "American system" of protection. Calhoun\
defended it on national principles. For this sudden reversal of policy\
the young Republicans were taunted by some of their older party\
colleagues with betraying the "agricultural interest" that Jefferson had\
fostered; but Calhoun refused to listen to their criticisms. "When the\
seas are open," he said, "the produce of the South may pour anywhere\
into the markets of the Old World.... What are the effects of a war with\
a maritime power--with England? Our commerce annihilated ... our\
agriculture cut off from its accustomed markets, the surplus of the\
farmer perishes on his hands.... The recent war fell with peculiar\
pressure on the growers of cotton and tobacco and the other great\
staples of the country; and the same state of things will recur in the\
event of another war unless prevented by the foresight of this body....\
When our manufactures are grown to a certain perfection, as they soon\
will be under the fostering care of the government, we shall no longer\
experience these evils." With the Republicans nationalized, the\
Federalist party, as an organization, disappeared after a crushing\
defeat in the presidential campaign of 1816.\
\
=Monroe and the Florida Purchase.=--To the victor in that political\
contest, James Monroe of Virginia, fell two tasks of national\
importance, adding to the prestige of the whole country and deepening\
the sense of patriotism that weaned men away from mere allegiance to\
states. The first of these was the purchase of Florida from Spain. The\
acquisition of Louisiana let the Mississippi flow "unvexed to the sea";\
but it left all the states east of the river cut off from the Gulf,\
affording them ground for discontent akin to that which had moved the\
pioneers of Kentucky to action a generation earlier. The uncertainty as\
to the boundaries of Louisiana gave the United States a claim to West\
Florida, setting on foot a movement for occupation. The Florida swamps\
were a basis for Indian marauders who periodically swept into the\
frontier settlements, and hiding places for runaway slaves. Thus the\
sanction of international law was given to punitive expeditions into\
alien territory.\
\
The pioneer leaders stood waiting for the signal. It came. President\
Monroe, on the occasion of an Indian outbreak, ordered General Jackson\
to seize the offenders, in the Floridas, if necessary. The high-spirited\
warrior, taking this as a hint that he was to occupy the coveted region,\
replied that, if possession was the object of the invasion, he could\
occupy the Floridas within sixty days. Without waiting for an answer to\
this letter, he launched his expedition, and in the spring of 1818 was\
master of the Spanish king's domain to the south.\
\
There was nothing for the king to do but to make the best of the\
inevitable by ceding the Floridas to the United States in return for\
five million dollars to be paid to American citizens having claims\
against Spain. On Washington's birthday, 1819, the treaty was signed. It\
ceded the Floridas to the United States and defined the boundary between\
Mexico and the United States by drawing a line from the mouth of the\
Sabine River in a northwesterly direction to the Pacific. On this\
occasion even Monroe, former opponent of the Constitution, forgot to\
inquire whether new territory could be constitutionally acquired and\
incorporated into the American union. The Republicans seemed far away\
from the days of "strict construction." And Jefferson still lived!\
\
=The Monroe Doctrine.=--Even more effective in fashioning the national\
idea was Monroe's enunciation of the famous doctrine that bears his\
name. The occasion was another European crisis. During the Napoleonic\
upheaval and the years of dissolution that ensued, the Spanish colonies\
in America, following the example set by their English neighbors in\
1776, declared their independence. Unable to conquer them alone, the\
king of Spain turned for help to the friendly powers of Europe that\
looked upon revolution and republics with undisguised horror.\
\
_The Holy Alliance._--He found them prepared to view his case with\
sympathy. Three of them, Austria, Prussia, and Russia, under the\
leadership of the Czar, Alexander I, in the autumn of 1815, had entered\
into a Holy Alliance to sustain by reciprocal service the autocratic\
principle in government. Although the effusive, almost maudlin, language\
of the treaty did not express their purpose explicitly, the Alliance was\
later regarded as a mere union of monarchs to prevent the rise and\
growth of popular government.\
\
The American people thought their worst fears confirmed when, in 1822, a\
conference of delegates from Russia, Austria, Prussia, and France met at\
Verona to consider, among other things, revolutions that had just broken\
out in Spain and Italy. The spirit of the conference is reflected in the\
first article of the agreement reached by the delegates: "The high\
contracting powers, being convinced that the system of representative\
government is equally incompatible with the monarchical principle and\
the maxim of the sovereignty of the people with the divine right,\
mutually engage in the most solemn manner to use all their efforts to\
put an end to the system of representative government in whatever\
country it may exist in Europe and to prevent its being introduced in\
those countries where it is not yet known." The Czar, who incidentally\
coveted the west coast of North America, proposed to send an army to aid\
the king of Spain in his troubles at home, thus preparing the way for\
intervention in Spanish America. It was material weakness not want of\
spirit, that prevented the grand union of monarchs from making open war\
on popular government.\
\
_The Position of England._--Unfortunately, too, for the Holy Alliance,\
England refused to cooperate. English merchants had built up a large\
trade with the independent Latin-American colonies and they protested\
against the restoration of Spanish sovereignty, which meant a renewal of\
Spain's former trade monopoly. Moreover, divine right doctrines had been\
laid to rest in England and the representative principle thoroughly\
established. Already there were signs of the coming democratic flood\
which was soon to carry the first reform bill of 1832, extending the\
suffrage, and sweep on to even greater achievements. British statesmen,\
therefore, had to be cautious. In such circumstances, instead of\
cooperating with the autocrats of Russia, Austria, and Prussia, they\
turned to the minister of the United States in London. The British prime\
minister, Canning, proposed that the two countries join in declaring\
their unwillingness to see the Spanish colonies transferred to any other\
power.\
\
_Jefferson's Advice._--The proposal was rejected; but President Monroe\
took up the suggestion with Madison and Jefferson as well as with his\
Secretary of State, John Quincy Adams. They favored the plan. Jefferson\
said: "One nation, most of all, could disturb us in this pursuit [of\
freedom]; she now offers to lead, aid, and accompany us in it. By\
acceding to her proposition we detach her from the bands, bring her\
mighty weight into the scale of free government and emancipate a\
continent at one stroke.... With her on our side we need not fear the\
whole world. With her then we should most sedulously cherish a cordial\
friendship."\
\
_Monroe's Statement of the Doctrine._--Acting on the advice of trusted\
friends, President Monroe embodied in his message to Congress, on\
December 2, 1823, a statement of principles now famous throughout the\
world as the Monroe Doctrine. To the autocrats of Europe he announced\
that he would regard "any attempt on their part to extend their system\
to any portion of this hemisphere as dangerous to our peace and safety."\
While he did not propose to interfere with existing colonies dependent\
on European powers, he ranged himself squarely on the side of those that\
had declared their independence. Any attempt by a European power to\
oppress them or control their destiny in any manner he characterized as\
"a manifestation of an unfriendly disposition toward the United States."\
Referring in another part of his message to a recent claim which the\
Czar had made to the Pacific coast, President Monroe warned the Old\
World that "the American continents, by the free and independent\
condition which they have assumed and maintained, are henceforth not to\
be considered as subjects for future colonization by any European\
powers." The effect of this declaration was immediate and profound. Men\
whose political horizon had been limited to a community or state were\
led to consider their nation as a great power among the sovereignties of\
the earth, taking its part in shaping their international relations.\
\
=The Missouri Compromise.=--Respecting one other important measure of\
this period, the Republicans also took a broad view of their obligations\
under the Constitution; namely, the Missouri Compromise. It is true,\
they insisted on the admission of Missouri as a slave state, balanced\
against the free state of Maine; but at the same time they assented to\
the prohibition of slavery in the Louisiana territory north of the line\
36 o 30'. During the debate on the subject an extreme view had been\
presented, to the effect that Congress had no constitutional warrant for\
abolishing slavery in the territories. The precedent of the Northwest\
Ordinance, ratified by Congress in 1789, seemed a conclusive answer from\
practice to this contention; but Monroe submitted the issue to his\
cabinet, which included Calhoun of South Carolina, Crawford of Georgia,\
and Wirt of Virginia, all presumably adherents to the Jeffersonian\
principle of strict construction. He received in reply a unanimous\
verdict to the effect that Congress did have the power to prohibit\
slavery in the territories governed by it. Acting on this advice he\
approved, on March 6, 1820, the bill establishing freedom north of the\
compromise line. This generous interpretation of the powers of Congress\
stood for nearly forty years, until repudiated by the Supreme Court in\
the Dred Scott case.\
\
\
THE NATIONAL DECISIONS OF CHIEF JUSTICE MARSHALL\
\
=John Marshall, the Nationalist.=--The Republicans in the lower ranges\
of state politics, who did not catch the grand national style of their\
leaders charged with responsibilities in the national field, were\
assisted in their education by a Federalist from the Old Dominion, John\
Marshall, who, as Chief Justice of the Supreme Court of the United\
States from 1801 to 1835, lost no occasion to exalt the Constitution\
above the claims of the provinces. No differences of opinion as to his\
political views have ever led even his warmest opponents to deny his\
superb abilities or his sincere devotion to the national idea. All will\
likewise agree that for talents, native and acquired, he was an ornament\
to the humble democracy that brought him forth. His whole career was\
American. Born on the frontier of Virginia, reared in a log cabin,\
granted only the barest rudiments of education, inured to hardship and\
rough life, he rose by masterly efforts to the highest judicial honor\
America can bestow.\
\
On him the bitter experience of the Revolution and of later days made a\
lasting impression. He was no "summer patriot." He had been a soldier in\
the Revolutionary army. He had suffered with Washington at Valley Forge.\
He had seen his comrades in arms starving and freezing because the\
Continental Congress had neither the power nor the inclination to force\
the states to do their full duty. To him the Articles of Confederation\
were the symbol of futility. Into the struggle for the formation of the\
Constitution and its ratification in Virginia he had thrown himself with\
the ardor of a soldier. Later, as a member of Congress, a representative\
to France, and Secretary of State, he had aided the Federalists in\
establishing the new government. When at length they were driven from\
power in the executive and legislative branches of the government, he\
was chosen for their last stronghold, the Supreme Court. By historic\
irony he administered the oath of office to his bitterest enemy, Thomas\
Jefferson; and, long after the author of the Declaration of Independence\
had retired to private life, the stern Chief Justice continued to\
announce the old Federalist principles from the Supreme Bench.\
\
[Illustration: JOHN MARSHALL]\
\
=Marbury _vs._ Madison--An Act of Congress Annulled.=--He had been in\
his high office only two years when he laid down for the first time in\
the name of the entire Court the doctrine that the judges have the power\
to declare an act of Congress null and void when in their opinion it\
violates the Constitution. This power was not expressly conferred on the\
Court. Though many able men held that the judicial branch of the\
government enjoyed it, the principle was not positively established\
until 1803 when the case of Marbury _vs._ Madison was decided. In\
rendering the opinion of the Court, Marshall cited no precedents. He\
sought no foundations for his argument in ancient history. He rested it\
on the general nature of the American system. The Constitution, ran his\
reasoning, is the supreme law of the land; it limits and binds all who\
act in the name of the United States; it limits the powers of Congress\
and defines the rights of citizens. If Congress can ignore its\
limitations and trespass upon the rights of citizens, Marshall argued,\
then the Constitution disappears and Congress is supreme. Since,\
however, the Constitution is supreme and superior to Congress, it is the\
duty of judges, under their oath of office, to sustain it against\
measures which violate it. Therefore, from the nature of the American\
constitutional system the courts must declare null and void all acts\
which are not authorized. "A law repugnant to the Constitution," he\
closed, "is void and the courts as well as other departments are bound\
by that instrument." From that day to this the practice of federal and\
state courts in passing upon the constitutionality of laws has remained\
unshaken.\
\
This doctrine was received by Jefferson and many of his followers with\
consternation. If the idea was sound, he exclaimed, "then indeed is our\
Constitution a complete _felo de se_ [legally, a suicide]. For,\
intending to establish three departments, coordinate and independent\
that they might check and balance one another, it has given, according\
to this opinion, to one of them alone the right to prescribe rules for\
the government of the others, and to that one, too, which is unelected\
by and independent of the nation.... The Constitution, on this\
hypothesis, is a mere thing of wax in the hands of the judiciary which\
they may twist and shape into any form they please. It should be\
remembered, as an axiom of eternal truth in politics, that whatever\
power in any government is independent, is absolute also.... A judiciary\
independent of a king or executive alone is a good thing; but\
independence of the will of the nation is a solecism, at least in a\
republican government." But Marshall was mighty and his view prevailed,\
though from time to time other men, clinging to Jefferson's opinion,\
likewise opposed the exercise by the Courts of the high power of passing\
upon the constitutionality of acts of Congress.\
\
=Acts of State Legislatures Declared Unconstitutional.=--Had Marshall\
stopped with annulling an act of Congress, he would have heard less\
criticism from Republican quarters; but, with the same firmness, he set\
aside acts of state legislatures as well, whenever, in his opinion, they\
violated the federal Constitution. In 1810, in the case of Fletcher\
_vs._ Peck, he annulled an act of the Georgia legislature, informing the\
state that it was not sovereign, but "a part of a large empire, ... a\
member of the American union; and that union has a constitution ...\
which imposes limits to the legislatures of the several states." In the\
case of McCulloch _vs._ Maryland, decided in 1819, he declared void an\
act of the Maryland legislature designed to paralyze the branches of the\
United States Bank established in that state. In the same year, in the\
still more memorable Dartmouth College case, he annulled an act of the\
New Hampshire legislature which infringed upon the charter received by\
the college from King George long before. That charter, he declared, was\
a contract between the state and the college, which the legislature\
under the federal Constitution could not impair. Two years later he\
stirred the wrath of Virginia by summoning her to the bar of the Supreme\
Court to answer in a case in which the validity of one of her laws was\
involved and then justified his action in a powerful opinion rendered in\
the case of Cohens _vs._ Virginia.\
\
All these decisions aroused the legislatures of the states. They passed\
sheaves of resolutions protesting and condemning; but Marshall never\
turned and never stayed. The Constitution of the United States, he\
fairly thundered at them, is the supreme law of the land; the Supreme\
Court is the proper tribunal to pass finally upon the validity of the\
laws of the states; and "those sovereignties," far from possessing the\
right of review and nullification, are irrevocably bound by the\
decisions of that Court. This was strong medicine for the authors of the\
Kentucky and Virginia Resolutions and for the members of the Hartford\
convention; but they had to take it.\
\
=The Doctrine of Implied Powers.=--While restraining Congress in the\
Marbury case and the state legislatures in a score of cases, Marshall\
also laid the judicial foundation for a broad and liberal view of the\
Constitution as opposed to narrow and strict construction. In McCulloch\
_vs._ Maryland, he construed generously the words "necessary and proper"\
in such a way as to confer upon Congress a wide range of "implied\
powers" in addition to their express powers. That case involved, among\
other things, the question whether the act establishing the second\
United States Bank was authorized by the Constitution. Marshall answered\
in the affirmative. Congress, ran his reasoning, has large powers over\
taxation and the currency; a bank is of appropriate use in the exercise\
of these enumerated powers; and therefore, though not absolutely\
necessary, a bank is entirely proper and constitutional. "With respect\
to the means by which the powers that the Constitution confers are to be\
carried into execution," he said, Congress must be allowed the\
discretion which "will enable that body to perform the high duties\
assigned to it, in the manner most beneficial to the people." In short,\
the Constitution of the United States is not a strait jacket but a\
flexible instrument vesting in Congress the powers necessary to meet\
national problems as they arise. In delivering this opinion Marshall\
used language almost identical with that employed by Lincoln when,\
standing on the battle field of a war waged to preserve the nation, he\
said that "a government of the people, by the people, for the people\
shall not perish from the earth."\
\
\
SUMMARY OF THE UNION AND NATIONAL POLITICS\
\
During the strenuous period between the establishment of American\
independence and the advent of Jacksonian democracy the great American\
experiment was under the direction of the men who had launched it. All\
the Presidents in that period, except John Quincy Adams, had taken part\
in the Revolution. James Madison, the chief author of the Constitution,\
lived until 1836. This age, therefore, was the "age of the fathers." It\
saw the threatened ruin of the country under the Articles of\
Confederation, the formation of the Constitution, the rise of political\
parties, the growth of the West, the second war with England, and the\
apparent triumph of the national spirit over sectionalism.\
\
The new republic had hardly been started in 1783 before its troubles\
began. The government could not raise money to pay its debts or running\
expenses; it could not protect American commerce and manufactures\
against European competition; it could not stop the continual issues of\
paper money by the states; it could not intervene to put down domestic\
uprisings that threatened the existence of the state governments.\
Without money, without an army, without courts of law, the union under\
the Articles of Confederation was drifting into dissolution. Patriots,\
who had risked their lives for independence, began to talk of monarchy\
again. Washington, Hamilton, and Madison insisted that a new\
constitution alone could save America from disaster.\
\
By dint of much labor the friends of a new form of government induced\
the Congress to call a national convention to take into account the\
state of America. In May, 1787, it assembled at Philadelphia and for\
months it debated and wrangled over plans for a constitution. The small\
states clamored for equal rights in the union. The large states vowed\
that they would never grant it. A spirit of conciliation, fair play, and\
compromise saved the convention from breaking up. In addition, there\
were jealousies between the planting states and the commercial states.\
Here, too, compromises had to be worked out. Some of the delegates\
feared the growth of democracy and others cherished it. These factions\
also had to be placated. At last a plan of government was drafted--the\
Constitution of the United States--and submitted to the states for\
approval. Only after a long and acrimonious debate did enough states\
ratify the instrument to put it into effect. On April 30, 1789, George\
Washington was inaugurated first President.\
\
The new government proceeded to fund the old debt of the nation, assume\
the debts of the states, found a national bank, lay heavy taxes to pay\
the bills, and enact laws protecting American industry and commerce.\
Hamilton led the way, but he had not gone far before he encountered\
opposition. He found a formidable antagonist in Jefferson. In time two\
political parties appeared full armed upon the scene: the Federalists\
and the Republicans. For ten years they filled the country with\
political debate. In 1800 the Federalists were utterly vanquished by the\
Republicans with Jefferson in the lead.\
\
By their proclamations of faith the Republicans favored the states\
rather than the new national government, but in practice they added\
immensely to the prestige and power of the nation. They purchased\
Louisiana from France, they waged a war for commercial independence\
against England, they created a second United States Bank, they enacted\
the protective tariff of 1816, they declared that Congress had power to\
abolish slavery north of the Missouri Compromise line, and they spread\
the shield of the Monroe Doctrine between the Western Hemisphere and\
Europe.\
\
Still America was a part of European civilization. Currents of opinion\
flowed to and fro across the Atlantic. Friends of popular government in\
Europe looked to America as the great exemplar of their ideals. Events\
in Europe reacted upon thought in the United States. The French\
Revolution exerted a profound influence on the course of political\
debate. While it was in the stage of mere reform all Americans favored\
it. When the king was executed and a radical democracy set up, American\
opinion was divided. When France fell under the military dominion of\
Napoleon and preyed upon American commerce, the United States made ready\
for war.\
\
The conduct of England likewise affected American affairs. In 1793 war\
broke out between England and France and raged with only a slight\
intermission until 1815. England and France both ravaged American\
commerce, but England was the more serious offender because she had\
command of the seas. Though Jefferson and Madison strove for peace, the\
country was swept into war by the vehemence of the "Young Republicans,"\
headed by Clay and Calhoun.\
\
When the armed conflict was closed, one in diplomacy opened. The\
autocratic powers of Europe threatened to intervene on behalf of Spain\
in her attempt to recover possession of her Latin-American colonies.\
Their challenge to America brought forth the Monroe Doctrine. The powers\
of Europe were warned not to interfere with the independence or the\
republican policies of this hemisphere or to attempt any new\
colonization in it. It seemed that nationalism was to have a peaceful\
triumph over sectionalism.\
\
\
=References=\
\
H. Adams, _History of the United States, 1800-1817_ (9 vols.).\
\
K.C. Babcock, _Rise of American Nationality_ (American Nation Series).\
\
E. Channing, _The Jeffersonian System_ (Same Series).\
\
D.C. Gilman, _James Monroe_.\
\
W. Reddaway, _The Monroe Doctrine_.\
\
T. Roosevelt, _Naval War of 1812_.\
\
\
=Questions=\
\
1. What was the leading feature of Jefferson's political theory?\
\
2. Enumerate the chief measures of his administration.\
\
3. Were the Jeffersonians able to apply their theories? Give the\
reasons.\
\
\
4. Explain the importance of the Mississippi River to Western farmers.\
\
5. Show how events in Europe forced the Louisiana Purchase.\
\
6. State the constitutional question involved in the Louisiana Purchase.\
\
7. Show how American trade was affected by the European war.\
\
8. Compare the policies of Jefferson and Madison.\
\
9. Why did the United States become involved with England rather than\
with France?\
\
10. Contrast the causes of the War of 1812 with the results.\
\
11. Give the economic reasons for the attitude of New England.\
\
12. Give five "nationalist" measures of the Republicans. Discuss each in\
detail.\
\
13. Sketch the career of John Marshall.\
\
14. Discuss the case of Marbury _vs._ Madison.\
\
15. Summarize Marshall's views on: (_a_) states' rights; and (_b_) a\
liberal interpretation of the Constitution.\
\
\
=Research Topics=\
\
=The Louisiana Purchase.=--Text of Treaty in Macdonald, _Documentary\
Source Book_, pp. 279-282. Source materials in Hart, _American History\
Told by Contemporaries_, Vol. III, pp. 363-384. Narrative, Henry Adams,\
_History of the United States_, Vol. II, pp. 25-115; Elson, _History of\
the United States_, pp. 383-388.\
\
=The Embargo and Non-Intercourse Acts.=--Macdonald, pp. 282-288; Adams,\
Vol. IV, pp. 152-177; Elson, pp. 394-405.\
\
=Congress and the War of 1812.=--Adams, Vol. VI, pp. 113-198; Elson, pp.\
408-450.\
\
=Proposals of the Hartford Convention.=--Macdonald, pp. 293-302.\
\
=Manufactures and the Tariff of 1816.=--Coman, _Industrial History of\
the United States_, pp. 184-194.\
\
=The Second United States Bank.=--Macdonald, pp. 302-306.\
\
=Effect of European War on American Trade.=--Callender, _Economic\
History of the United States_, pp. 240-250.\
\
=The Monroe Message.=--Macdonald, pp. 318-320.\
\
=Lewis and Clark Expedition.=--R.G. Thwaites, _Rocky Mountain\
Explorations_, pp. 92-187. Schafer, _A History of the Pacific Northwest_\
(rev. ed.), pp. 29-61.\
\
\
\
\
PART IV. THE WEST AND JACKSONIAN DEMOCRACY\
\
\
\
\
CHAPTER X\
\
THE FARMERS BEYOND THE APPALACHIANS\
\
\
The nationalism of Hamilton was undemocratic. The democracy of Jefferson\
was, in the beginning, provincial. The historic mission of uniting\
nationalism and democracy was in the course of time given to new leaders\
from a region beyond the mountains, peopled by men and women from all\
sections and free from those state traditions which ran back to the\
early days of colonization. The voice of the democratic nationalism\
nourished in the West was heard when Clay of Kentucky advocated his\
American system of protection for industries; when Jackson of Tennessee\
condemned nullification in a ringing proclamation that has taken its\
place among the great American state papers; and when Lincoln of\
Illinois, in a fateful hour, called upon a bewildered people to meet the\
supreme test whether this was a nation destined to survive or to perish.\
And it will be remembered that Lincoln's party chose for its banner that\
earlier device--Republican--which Jefferson had made a sign of power.\
The "rail splitter" from Illinois united the nationalism of Hamilton\
with the democracy of Jefferson, and his appeal was clothed in the\
simple language of the people, not in the sonorous rhetoric which\
Webster learned in the schools.\
\
\
PREPARATION FOR WESTERN SETTLEMENT\
\
=The West and the American Revolution.=--The excessive attention devoted\
by historians to the military operations along the coast has obscured\
the role played by the frontier in the American Revolution. The action\
of Great Britain in closing western land to easy settlement in 1763 was\
more than an incident in precipitating the war for independence.\
Americans on the frontier did not forget it; when Indians were employed\
by England to defend that land, zeal for the patriot cause set the\
interior aflame. It was the members of the western vanguard, like Daniel\
Boone, John Sevier, and George Rogers Clark, who first understood the\
value of the far-away country under the guns of the English forts, where\
the Red Men still wielded the tomahawk and the scalping knife. It was\
they who gave the East no rest until their vision was seen by the\
leaders on the seaboard who directed the course of national policy. It\
was one of their number, a seasoned Indian fighter, George Rogers Clark,\
who with aid from Virginia seized Kaskaskia and Vincennes and secured\
the whole Northwest to the union while the fate of Washington's army was\
still hanging in the balance.\
\
=Western Problems at the End of the Revolution.=--The treaty of peace,\
signed with Great Britain in 1783, brought the definite cession of the\
coveted territory west to the Mississippi River, but it left unsolved\
many problems. In the first place, tribes of resentful Indians in the\
Ohio region, even though British support was withdrawn at last, had to\
be reckoned with; and it was not until after the establishment of the\
federal Constitution that a well-equipped army could be provided to\
guarantee peace on the border. In the second place, British garrisons\
still occupied forts on Lake Erie pending the execution of the terms of\
the treaty of 1783--terms which were not fulfilled until after the\
ratification of the Jay treaty twelve years later. In the third place,\
Virginia, Connecticut, and Massachusetts had conflicting claims to the\
land in the Northwest based on old English charters and Indian treaties.\
It was only after a bitter contest that the states reached an agreement\
to transfer their rights to the government of the United States,\
Virginia executing her deed of cession on March 1, 1784. In the fourth\
place, titles to lands bought by individuals remained uncertain in the\
absence of official maps and records. To meet this last situation,\
Congress instituted a systematic survey of the Ohio country, laying it\
out into townships, sections of 640 acres each, and quarter sections. In\
every township one section of land was set aside for the support of\
public schools.\
\
=The Northwest Ordinance.=--The final problem which had to be solved\
before settlement on a large scale could be begun was that of governing\
the territory. Pioneers who looked with hungry eyes on the fertile\
valley of the Ohio could hardly restrain their impatience. Soldiers of\
the Revolution, who had been paid for their services in land warrants\
entitling them to make entries in the West, called for action.\
\
Congress answered by passing in 1787 the famous Northwest Ordinance\
providing for temporary territorial government to be followed by the\
creation of a popular assembly as soon as there were five thousand free\
males in any district. Eventual admission to the union on an equal\
footing with the original states was promised to the new territories.\
Religious freedom was guaranteed. The safeguards of trial by jury,\
regular judicial procedure, and _habeas corpus_ were established, in order\
that the methods of civilized life might take the place of the\
rough-and-ready justice of lynch law. During the course of the debate on\
the Ordinance, Congress added the sixth article forbidding slavery and\
involuntary servitude.\
\
This Charter of the Northwest, so well planned by the Congress under the\
Articles of Confederation, was continued in force by the first Congress\
under the Constitution in 1789. The following year its essential\
provisions, except the ban on slavery, were applied to the territory\
south of the Ohio, ceded by North Carolina to the national government,\
and in 1798 to the Mississippi territory, once held by Georgia. Thus it\
was settled for all time that "the new colonies were not to be exploited\
for the benefit of the parent states (any more than for the benefit of\
England) but were to be autonomous and coordinate commonwealths." This\
outcome, bitterly opposed by some Eastern leaders who feared the triumph\
of Western states over the seaboard, completed the legal steps necessary\
by way of preparation for the flood of settlers.\
\
=The Land Companies, Speculators, and Western Land Tenure.=--As in the\
original settlement of America, so in the opening of the West, great\
companies and single proprietors of large grants early figured. In 1787\
the Ohio Land Company, a New England concern, acquired a million and a\
half acres on the Ohio and began operations by planting the town of\
Marietta. A professional land speculator, J.C. Symmes, secured a million\
acres lower down where the city of Cincinnati was founded. Other\
individuals bought up soldiers' claims and so acquired enormous holdings\
for speculative purposes. Indeed, there was such a rush to make fortunes\
quickly through the rise in land values that Washington was moved to cry\
out against the "rage for speculating in and forestalling of land on the\
North West of the Ohio," protesting that "scarce a valuable spot within\
any tolerable distance of it is left without a claimant." He therefore\
urged Congress to fix a reasonable price for the land, not "too\
exorbitant and burdensome for real occupiers, but high enough to\
discourage monopolizers."\
\
Congress, however, was not prepared to use the public domain for the\
sole purpose of developing a body of small freeholders in the West. It\
still looked upon the sale of public lands as an important source of\
revenue with which to pay off the public debt; consequently it thought\
more of instant income than of ultimate results. It placed no limit on\
the amount which could be bought when it fixed the price at $2 an acre\
in 1796, and it encouraged the professional land operator by making the\
first installment only twenty cents an acre in addition to the small\
registration and survey fee. On such terms a speculator with a few\
thousand dollars could get possession of an enormous plot of land. If he\
was fortunate in disposing of it, he could meet the installments, which\
were spread over a period of four years, and make a handsome profit for\
himself. Even when the credit or installment feature was abolished in\
1821 and the price of the land lowered to a cash price of $1.75 an acre,\
the opportunity for large speculative purchases continued to attract\
capital to land ventures.\
\
=The Development of the Small Freehold.=--The cheapness of land and the\
scarcity of labor, nevertheless, made impossible the triumph of the huge\
estate with its semi-servile tenantry. For about $45 a man could get a\
farm of 160 acres on the installment plan; another payment of $80 was\
due in forty days; but a four-year term was allowed for the discharge of\
the balance. With a capital of from two to three hundred dollars a\
family could embark on a land venture. If it had good crops, it could\
meet the deferred payments. It was, however, a hard battle at best. Many\
a man forfeited his land through failure to pay the final installment;\
yet in the end, in spite of all the handicaps, the small freehold of a\
few hundred acres at most became the typical unit of Western\
agriculture, except in the planting states of the Gulf. Even the lands\
of the great companies were generally broken up and sold in small lots.\
\
The tendency toward moderate holdings, so favored by Western conditions,\
was also promoted by a clause in the Northwest Ordinance declaring that\
the land of any person dying intestate--that is, without any will\
disposing of it--should be divided equally among his descendants.\
Hildreth says of this provision: "It established the important\
republican principle, not then introduced into all the states, of the\
equal distribution of landed as well as personal property." All these\
forces combined made the wide dispersion of wealth, in the early days of\
the nineteenth century, an American characteristic, in marked contrast\
with the European system of family prestige and vast estates based on\
the law of primogeniture.\
\
\
THE WESTERN MIGRATION AND NEW STATES\
\
=The People.=--With government established, federal arms victorious over\
the Indians, and the lands surveyed for sale, the way was prepared for\
the immigrants. They came with a rush. Young New Englanders, weary of\
tilling the stony soil of their native states, poured through New York\
and Pennsylvania, some settling on the northern bank of the Ohio but\
most of them in the Lake region. Sons and daughters of German farmers in\
Pennsylvania and many a redemptioner who had discharged his bond of\
servitude pressed out into Ohio, Kentucky, Tennessee, or beyond. From\
the exhausted fields and the clay hills of the Southern states came\
pioneers of English and Scotch-Irish descent, the latter in great\
numbers. Indeed one historian of high authority has ventured to say that\
"the rapid expansion of the United States from a coast strip to a\
continental area is largely a Scotch-Irish achievement." While native\
Americans of mixed stocks led the way into the West, it was not long\
before immigrants direct from Europe, under the stimulus of company\
enterprise, began to filter into the new settlements in increasing\
numbers.\
\
The types of people were as various as the nations they represented.\
Timothy Flint, who published his entertaining _Recollections_ in 1826,\
found the West a strange mixture of all sorts and conditions of people.\
Some of them, he relates, had been hunters in the upper world of the\
Mississippi, above the falls of St. Anthony. Some had been still farther\
north, in Canada. Still others had wandered from the South--the Gulf of\
Mexico, the Red River, and the Spanish country. French boatmen and\
trappers, Spanish traders from the Southwest, Virginia planters with\
their droves of slaves mingled with English, German, and Scotch-Irish\
farmers. Hunters, forest rangers, restless bordermen, and squatters,\
like the foaming combers of an advancing tide, went first. Then followed\
the farmers, masters of the ax and plow, with their wives who shared\
every burden and hardship and introduced some of the features of\
civilized life. The hunters and rangers passed on to new scenes; the\
home makers built for all time.\
\
=The Number of Immigrants.=--There were no official stations on the\
frontier to record the number of immigrants who entered the West during\
the decades following the American Revolution. But travelers of the time\
record that every road was "crowded" with pioneers and their families,\
their wagons and cattle; and that they were seldom out of the sound of\
the snapping whip of the teamster urging forward his horses or the crack\
of the hunter's rifle as he brought down his evening meal. "During the\
latter half of 1787," says Coman, "more than nine hundred boats floated\
down the Ohio carrying eighteen thousand men, women, and children, and\
twelve thousand horses, sheep, and cattle, and six hundred and fifty\
wagons." Other lines of travel were also crowded and with the passing\
years the flooding tide of home seekers rose higher and higher.\
\
=The Western Routes.=--Four main routes led into the country beyond the\
Appalachians. The Genesee road, beginning at Albany, ran almost due west\
to the present site of Buffalo on Lake Erie, through a level country. In\
the dry season, wagons laden with goods could easily pass along it into\
northern Ohio. A second route, through Pittsburgh, was fed by three\
eastern branches, one starting at Philadelphia, one at Baltimore, and\
another at Alexandria. A third main route wound through the mountains\
from Alexandria to Boonesboro in Kentucky and then westward across the\
Ohio to St. Louis. A fourth, the most famous of them all, passed through\
the Cumberland Gap and by branches extended into the Cumberland valley\
and the Kentucky country.\
\
Of these four lines of travel, the Pittsburgh route offered the most\
advantages. Pioneers, no matter from what section they came, when once\
they were on the headwaters of the Ohio and in possession of a flatboat,\
could find a quick and easy passage into all parts of the West and\
Southwest. Whether they wanted to settle in Ohio, Kentucky, or western\
Tennessee they could find their way down the drifting flood to their\
destination or at least to some spot near it. Many people from the South\
as well as the Northern and Middle states chose this route; so it came\
about that the sons and daughters of Virginia and the Carolinas mingled\
with those of New York, Pennsylvania, and New England in the settlement\
of the Northwest territory.\
\
=The Methods of Travel into the West.=--Many stories giving exact\
descriptions of methods of travel into the West in the early days have\
been preserved. The country was hardly opened before visitors from the\
Old World and from the Eastern states, impelled by curiosity, made their\
way to the very frontier of civilization and wrote books to inform or\
amuse the public. One of them, Gilbert Imlay, an English traveler, has\
given us an account of the Pittsburgh route as he found it in 1791. "If\
a man ... " he writes, "has a family or goods of any sort to remove, his\
best way, then, would be to purchase a waggon and team of horses to\
carry his property to Redstone Old Fort or to Pittsburgh, according as\
he may come from the Northern or Southern states. A good waggon will\
cost, at Philadelphia, about $10 ... and the horses about $12 each; they\
would cost something more both at Baltimore and Alexandria. The waggon\
may be covered with canvass, and if it is the choice of the people, they\
may sleep in it of nights with the greatest safety. But if they dislike\
that, there are inns of accommodation the whole distance on the\
different roads.... The provisions I would purchase in the same manner\
[that is, from the farmers along the road]; and by having two or three\
camp kettles and stopping every evening when the weather is fine upon\
the brink of some rivulet and by kindling a fire they may soon dress\
their own food.... This manner of journeying is so far from being\
disagreeable that in a fine season it is extremely pleasant." The\
immigrant once at Pittsburgh or Wheeling could then buy a flatboat of a\
size required for his goods and stock, and drift down the current to his\
journey's end.\
\
[Illustration: ROADS AND TRAILS INTO THE WESTERN TERRITORY]\
\
=The Admission of Kentucky and Tennessee.=--When the eighteenth century\
drew to a close, Kentucky had a population larger than Delaware, Rhode\
Island, or New Hampshire. Tennessee claimed 60,000 inhabitants. In 1792\
Kentucky took her place as a state beside her none too kindly parent,\
Virginia. The Eastern Federalists resented her intrusion; but they took\
some consolation in the admission of Vermont because the balance of\
Eastern power was still retained.\
\
As if to assert their independence of old homes and conservative ideas\
the makers of Kentucky's first constitution swept aside the landed\
qualification on the suffrage and gave the vote to all free white males.\
Four years later, Kentucky's neighbor to the south, Tennessee, followed\
this step toward a wider democracy. After encountering fierce opposition\
from the Federalists, Tennessee was accepted as the sixteenth state.\
\
=Ohio.=--The door of the union had hardly opened for Tennessee when\
another appeal was made to Congress, this time from the pioneers in\
Ohio. The little posts founded at Marietta and Cincinnati had grown into\
flourishing centers of trade. The stream of immigrants, flowing down the\
river, added daily to their numbers and the growing settlements all\
around poured produce into their markets to be exchanged for "store\
goods." After the Indians were disposed of in 1794 and the last British\
soldier left the frontier forts under the terms of the Jay treaty of\
1795, tiny settlements of families appeared on Lake Erie in the "Western\
Reserve," a region that had been retained by Connecticut when she\
surrendered her other rights in the Northwest.\
\
At the close of the century, Ohio, claiming a population of more than\
50,000, grew discontented with its territorial status. Indeed, two years\
before the enactment of the Northwest Ordinance, squatters in that\
region had been invited by one John Emerson to hold a convention after\
the fashion of the men of Hartford, Windsor, and Wethersfield in old\
Connecticut and draft a frame of government for themselves. This true\
son of New England declared that men "have an undoubted right to pass\
into every vacant country and there to form their constitution and that\
from the confederation of the whole United States Congress is not\
empowered to forbid them." This grand convention was never held because\
the heavy hand of the government fell upon the leaders; but the spirit\
of John Emerson did not perish. In November, 1802, a convention chosen\
by voters, assembled under the authority of Congress at Chillicothe,\
drew up a constitution. It went into force after a popular ratification.\
The roll of the convention bore such names as Abbot, Baldwin, Cutler,\
Huntington, Putnam, and Sargent, and the list of counties from which\
they came included Adams, Fairfield, Hamilton, Jefferson, Trumbull, and\
Washington, showing that the new America in the West was peopled and led\
by the old stock. In 1803 Ohio was admitted to the union.\
\
=Indiana and Illinois.=--As in the neighboring state, the frontier in\
Indiana advanced northward from the Ohio, mainly under the leadership,\
however, of settlers from the South--restless Kentuckians hoping for\
better luck in a newer country and pioneers from the far frontiers of\
Virginia and North Carolina. As soon as a tier of counties swinging\
upward like the horns of the moon against Ohio on the east and in the\
Wabash Valley on the west was fairly settled, a clamor went up for\
statehood. Under the authority of an act of Congress in 1816 the\
Indianians drafted a constitution and inaugurated their government at\
Corydon. "The majority of the members of the convention," we are told by\
a local historian, "were frontier farmers who had a general idea of what\
they wanted and had sense enough to let their more erudite colleagues\
put it into shape."\
\
Two years later, the pioneers of Illinois, also settled upward from the\
Ohio, like Indiana, elected their delegates to draft a constitution.\
Leadership in the convention, quite properly, was taken by a man born in\
New York and reared in Tennessee; and the constitution as finally\
drafted "was in its principal provisions a copy of the then existing\
constitutions of Kentucky, Ohio, and Indiana.... Many of the articles\
are exact copies in wording although differently arranged and\
numbered."\
\
=Louisiana, Mississippi, and Alabama.=--Across the Mississippi to the\
far south, clearing and planting had gone on with much bustle and\
enterprise. The cotton and sugar lands of Louisiana, opened by French\
and Spanish settlers, were widened in every direction by planters with\
their armies of slaves from the older states. New Orleans, a good market\
and a center of culture not despised even by the pioneer, grew apace. In\
1810 the population of lower Louisiana was over 75,000. The time had\
come, said the leaders of the people, to fulfill the promise made to\
France in the treaty of cession; namely, to grant to the inhabitants of\
the territory statehood and the rights of American citizens. Federalists\
from New England still having a voice in Congress, if somewhat weaker,\
still protested in tones of horror. "I am compelled to declare it as my\
deliberate opinion," pronounced Josiah Quincy in the House of\
Representatives, "that if this bill [to admit Louisiana] passes, the\
bonds of this Union are virtually dissolved ... that as it will be the\
right of all, so it will be the duty of some [states] to prepare\
definitely for a separation; amicably if they can, violently if they\
must.... It is a death blow to the Constitution. It may afterwards\
linger; but lingering, its fate will, at no very distant period, be\
consummated." Federalists from New York like those from New England had\
their doubts about the wisdom of admitting Western states; but the party\
of Jefferson and Madison, having the necessary majority, granted the\
coveted statehood to Louisiana in 1812.\
\
When, a few years later, Mississippi and Alabama knocked at the doors of\
the union, the Federalists had so little influence, on account of their\
conduct during the second war with England, that spokesmen from the\
Southwest met a kindlier reception at Washington. Mississippi, in 1817,\
and Alabama, in 1819, took their places among the United States of\
America. Both of them, while granting white manhood suffrage, gave their\
constitutions the tone of the old East by providing landed\
qualifications for the governor and members of the legislature.\
\
=Missouri.=--Far to the north in the Louisiana purchase, a new\
commonwealth was rising to power. It was peopled by immigrants who came\
down the Ohio in fleets of boats or crossed the Mississippi from\
Kentucky and Tennessee. Thrifty Germans from Pennsylvania, hardy farmers\
from Virginia ready to work with their own hands, freemen seeking\
freemen's homes, planters with their slaves moving on from worn-out\
fields on the seaboard, came together in the widening settlements of the\
Missouri country. Peoples from the North and South flowed together,\
small farmers and big planters mingling in one community. When their\
numbers had reached sixty thousand or more, they precipitated a contest\
over their admission to the union, "ringing an alarm bell in the night,"\
as Jefferson phrased it. The favorite expedient of compromise with\
slavery was brought forth in Congress once more. Maine consequently was\
brought into the union without slavery and Missouri with slavery. At the\
same time there was drawn westward through the rest of the Louisiana\
territory a line separating servitude from slavery.\
\
\
THE SPIRIT OF THE FRONTIER\
\
=Land Tenure and Liberty.=--Over an immense western area there developed\
an unbroken system of freehold farms. In the Gulf states and the lower\
Mississippi Valley, it is true, the planter with his many slaves even\
led in the pioneer movement; but through large sections of Tennessee and\
Kentucky, as well as upper Georgia and Alabama, and all throughout the\
Northwest territory the small farmer reigned supreme. In this immense\
dominion there sprang up a civilization without caste or class--a body\
of people all having about the same amount of this world's goods and\
deriving their livelihood from one source: the labor of their own hands\
on the soil. The Northwest territory alone almost equaled in area all\
the original thirteen states combined, except Georgia, and its system of\
agricultural economy was unbroken by plantations and feudal estates. "In\
the subdivision of the soil and the great equality of condition," as\
Webster said on more than one occasion, "lay the true basis, most\
certainly, of popular government." There was the undoubted source of\
Jacksonian democracy.\
\
[Illustration: A LOG CABIN--LINCOLN'S BIRTHPLACE]\
\
=The Characteristics of the Western People.=--Travelers into the\
Northwest during the early years of the nineteenth century were agreed\
that the people of that region were almost uniformly marked by the\
characteristics common to an independent yeomanry. A close observer thus\
recorded his impressions: "A spirit of adventurous enterprise, a\
willingness to go through any hardship to accomplish an object....\
Independence of thought and action. They have felt the influence of\
these principles from their childhood. Men who can endure anything; that\
have lived almost without restraint, free as the mountain air or as the\
deer and the buffalo of their forests, and who know they are Americans\
all.... An apparent roughness which some would deem rudeness of\
manner.... Where there is perfect equality in a neighborhood of people\
who know little about each other's previous history or ancestry but\
where each is lord of the soil he cultivates. Where a log cabin is all\
that the best of families can expect to have for years and of course can\
possess few of the external decorations which have so much influence in\
creating a diversity of rank in society. These circumstances have laid\
the foundation for that equality of intercourse, simplicity of manners,\
want of deference, want of reserve, great readiness to make\
acquaintances, freedom of speech, indisposition to brook real or\
imaginary insults which one witnesses among people of the West."\
\
This equality, this independence, this rudeness so often described by\
the traveler as marking a new country, were all accentuated by the\
character of the settlers themselves. Traces of the fierce, unsociable,\
eagle-eyed, hard-drinking hunter remained. The settlers who followed the\
hunter were, with some exceptions, soldiers of the Revolutionary army,\
farmers of the "middling order," and mechanics from the towns,--English,\
Scotch-Irish, Germans,--poor in possessions and thrown upon the labor of\
their own hands for support. Sons and daughters from well-to-do Eastern\
homes sometimes brought softer manners; but the equality of life and the\
leveling force of labor in forest and field soon made them one in spirit\
with their struggling neighbors. Even the preachers and teachers, who\
came when the cabins were raised in the clearings and rude churches and\
schoolhouses were built, preached sermons and taught lessons that\
savored of the frontier, as any one may know who reads Peter\
Cartwright's _A Muscular Christian_ or Eggleston's _The Hoosier\
Schoolmaster_.\
\
\
THE WEST AND THE EAST MEET\
\
=The East Alarmed.=--A people so independent as the Westerners and so\
attached to local self-government gave the conservative East many a rude\
shock, setting gentlemen in powdered wigs and knee breeches agog with\
the idea that terrible things might happen in the Mississippi Valley.\
Not without good grounds did Washington fear that "a touch of a feather\
would turn" the Western settlers away from the seaboard to the\
Spaniards; and seriously did he urge the East not to neglect them, lest\
they be "drawn into the arms of, or be dependent upon foreigners."\
Taking advantage of the restless spirit in the Southwest, Aaron Burr,\
having disgraced himself by killing Alexander Hamilton in a duel, laid\
wild plans, if not to bring about a secession in that region, at least\
to build a state of some kind out of the Spanish dominions adjoining\
Louisiana. Frightened at such enterprises and fearing the dominance of\
the West, the Federalists, with a few conspicuous exceptions, opposed\
equality between the sections. Had their narrow views prevailed, the\
West, with its new democracy, would have been held in perpetual tutelage\
to the seaboard or perhaps been driven into independence as the thirteen\
colonies had been not long before.\
\
=Eastern Friends of the West.=--Fortunately for the nation, there were\
many Eastern leaders, particularly from the South, who understood the\
West, approved its spirit, and sought to bring the two sections together\
by common bonds. Washington kept alive and keen the zeal for Western\
advancement which he acquired in his youth as a surveyor. He never grew\
tired of urging upon his Eastern friends the importance of the lands\
beyond the mountains. He pressed upon the governor of Virginia a project\
for a wagon road connecting the seaboard with the Ohio country and was\
active in a movement to improve the navigation of the Potomac. He\
advocated strengthening the ties of commerce. "Smooth the roads," he\
said, "and make easy the way for them, and then see what an influx of\
articles will be poured upon us; how amazingly our exports will be\
increased by them; and how amply we shall be compensated for any trouble\
and expense we may encounter to effect it." Jefferson, too, was\
interested in every phase of Western development--the survey of lands,\
the exploration of waterways, the opening of trade, and even the\
discovery of the bones of prehistoric animals. Robert Fulton, the\
inventor of the steamboat, was another man of vision who for many years\
pressed upon his countrymen the necessity of uniting East and West by a\
canal which would cement the union, raise the value of the public lands,\
and extend the principles of confederate and republican government.\
\
=The Difficulties of Early Transportation.=--Means of communication\
played an important part in the strategy of all those who sought to\
bring together the seaboard and the frontier. The produce of the\
West--wheat, corn, bacon, hemp, cattle, and tobacco--was bulky and the\
cost of overland transportation was prohibitive. In the Eastern market,\
"a cow and her calf were given for a bushel of salt, while a suit of\
'store clothes' cost as much as a farm." In such circumstances, the\
inhabitants of the Mississippi Valley were forced to ship their produce\
over a long route by way of New Orleans and to pay high freight rates\
for everything that was brought across the mountains. Scows of from five\
to fifty tons were built at the towns along the rivers and piloted down\
the stream to the Crescent City. In a few cases small ocean-going\
vessels were built to transport goods to the West Indies or to the\
Eastern coast towns. Salt, iron, guns, powder, and the absolute\
essentials which the pioneers had to buy mainly in Eastern markets were\
carried over narrow wagon trails that were almost impassable in the\
rainy season.\
\
=The National Road.=--To far-sighted men, like Albert Gallatin, "the\
father of internal improvements," the solution of this problem was the\
construction of roads and canals. Early in Jefferson's administration,\
Congress dedicated a part of the proceeds from the sale of lands to\
building highways from the headwaters of the navigable waters emptying\
into the Atlantic to the Ohio River and beyond into the Northwest\
territory. In 1806, after many misgivings, it authorized a great\
national highway binding the East and the West. The Cumberland Road, as\
it was called, began in northwestern Maryland, wound through southern\
Pennsylvania, crossed the narrow neck of Virginia at Wheeling, and then\
shot almost straight across Ohio, Indiana, and Illinois, into Missouri.\
By 1817, stagecoaches were running between Washington and Wheeling; by\
1833 contractors had carried their work to Columbus, Ohio, and by 1852,\
to Vandalia, Illinois. Over this ballasted road mail and passenger\
coaches could go at high speed, and heavy freight wagons proceed in\
safety at a steady pace.\
\
[Illustration: THE CUMBERLAND ROAD]\
\
=Canals and Steamboats.=--A second epoch in the economic union of the\
East and West was reached with the opening of the Erie Canal in 1825,\
offering an all-water route from New York City to the Great Lakes and\
the Mississippi Valley. Pennsylvania, alarmed by the advantages\
conferred on New York by this enterprise, began her system of canals and\
portages from Philadelphia to Pittsburgh, completing the last link in\
1834. In the South, the Chesapeake and Ohio Company, chartered in 1825,\
was busy with a project to connect Georgetown and Cumberland when\
railways broke in upon the undertaking before it was half finished.\
About the same time, Ohio built a canal across the state, affording\
water communication between Lake Erie and the Ohio River through a rich\
wheat belt. Passengers could now travel by canal boat into the West with\
comparative ease and comfort, if not at a rapid speed, and the bulkiest\
of freight could be easily handled. Moreover, the rate charged for\
carrying goods was cut by the Erie Canal from $32 a ton per hundred\
miles to $1. New Orleans was destined to lose her primacy in the\
Mississippi Valley.\
\
The diversion of traffic to Eastern markets was also stimulated by\
steamboats which appeared on the Ohio about 1810, three years after\
Fulton had made his famous trip on the Hudson. It took twenty men to\
sail and row a five-ton scow up the river at a speed of from ten to\
twenty miles a day. In 1825, Timothy Flint traveled a hundred miles a\
day on the new steamer _Grecian_ "against the whole weight of the\
Mississippi current." Three years later the round trip from Louisville\
to New Orleans was cut to eight days. Heavy produce that once had to\
float down to New Orleans could be carried upstream and sent to the East\
by way of the canal systems.\
\
[Illustration: _From an old print_\
\
AN EARLY MISSISSIPPI STEAMBOAT]\
\
Thus the far country was brought near. The timid no longer hesitated at\
the thought of the perilous journey. All routes were crowded with\
Western immigrants. The forests fell before the ax like grain before the\
sickle. Clearings scattered through the woods spread out into a great\
mosaic of farms stretching from the Southern Appalachians to Lake\
Michigan. The national census of 1830 gave 937,000 inhabitants to Ohio;\
343,000 to Indiana; 157,000 to Illinois; 687,000 to Kentucky; and\
681,000 to Tennessee.\
\
[Illustration: DISTRIBUTION OF POPULATION, 1830]\
\
With the increase in population and the growth of agriculture came\
political influence. People who had once petitioned Congress now sent\
their own representatives. Men who had hitherto accepted without\
protests Presidents from the seaboard expressed a new spirit of dissent\
in 1824 by giving only three electoral votes for John Quincy Adams; and\
four years later they sent a son of the soil from Tennessee, Andrew\
Jackson, to take Washington's chair as chief executive of the\
nation--the first of a long line of Presidents from the Mississippi\
basin.\
\
\
=References=\
\
W.G. Brown, _The Lower South in American History_.\
\
B.A. Hinsdale, _The Old North West_ (2 vols.).\
\
A.B. Hulbert, _Great American Canals_ and _The Cumberland Road_.\
\
T. Roosevelt, _Thomas H. Benton_.\
\
P.J. Treat, _The National Land System_ (1785-1820).\
\
F.J. Turner, _Rise of the New West_ (American Nation Series).\
\
J. Winsor, _The Westward Movement_.\
\
\
=Questions=\
\
1. How did the West come to play a role in the Revolution?\
\
2. What preparations were necessary to settlement?\
\
3. Give the principal provisions of the Northwest Ordinance.\
\
4. Explain how freehold land tenure happened to predominate in the West.\
\
5. Who were the early settlers in the West? What routes did they take?\
How did they travel?\
\
6. Explain the Eastern opposition to the admission of new Western\
states. Show how it was overcome.\
\
7. Trace a connection between the economic system of the West and the\
spirit of the people.\
\
8. Who were among the early friends of Western development?\
\
9. Describe the difficulties of trade between the East and the West.\
\
10. Show how trade was promoted.\
\
\
=Research Topics=\
\
=Northwest Ordinance.=--Analysis of text in Macdonald, _Documentary\
Source Book_. Roosevelt, _Winning of the West_, Vol. V, pp. 5-57.\
\
=The West before the Revolution.=--Roosevelt, Vol. I.\
\
=The West during the Revolution.=--Roosevelt, Vols. II and III.\
\
=Tennessee.=--Roosevelt, Vol. V, pp. 95-119 and Vol. VI, pp. 9-87.\
\
=The Cumberland Road.=--A.B. Hulbert, _The Cumberland Road_.\
\
=Early Life in the Middle West.=--Callender, _Economic History of the\
United States_, pp. 617-633; 636-641.\
\
=Slavery in the Southwest.=--Callender, pp. 641-652.\
\
=Early Land Policy.=--Callender, pp. 668-680.\
\
=Westward Movement of Peoples.=--Roosevelt, Vol. IV, pp. 7-39.\
\
Lists of books dealing with the early history of Western states are\
given in Hart, Channing, and Turner, _Guide to the Study and Reading of\
American History_ (rev. ed.), pp. 62-89.\
\
=Kentucky.=--Roosevelt, Vol. IV, pp. 176-263.\
\
\
\
\
CHAPTER XI\
\
JACKSONIAN DEMOCRACY\
\
\
The New England Federalists, at the Hartford convention, prophesied that\
in time the West would dominate the East. "At the adoption of the\
Constitution," they said, "a certain balance of power among the original\
states was considered to exist, and there was at that time and yet is\
among those parties a strong affinity between their great and general\
interests. By the admission of these [new] states that balance has been\
materially affected and unless the practice be modified must ultimately\
be destroyed. The Southern states will first avail themselves of their\
new confederates to govern the East, and finally the Western states,\
multiplied in number, and augmented in population, will control the\
interests of the whole." Strangely enough the fulfillment of this\
prophecy was being prepared even in Federalist strongholds by the rise\
of a new urban democracy that was to make common cause with the farmers\
beyond the mountains.\
\
\
THE DEMOCRATIC MOVEMENT IN THE EAST\
\
=The Aristocratic Features of the Old Order.=--The Revolutionary\
fathers, in setting up their first state constitutions, although they\
often spoke of government as founded on the consent of the governed, did\
not think that consistency required giving the vote to all adult males.\
On the contrary they looked upon property owners as the only safe\
"depositary" of political power. They went back to the colonial\
tradition that related taxation and representation. This, they argued,\
was not only just but a safeguard against the "excesses of democracy."\
\
In carrying their theory into execution they placed taxpaying or\
property qualifications on the right to vote. Broadly speaking, these\
limitations fell into three classes. Three states, Pennsylvania (1776),\
New Hampshire (1784), and Georgia (1798), gave the ballot to all who\
paid taxes, without reference to the value of their property. Three,\
Virginia, Delaware, and Rhode Island, clung firmly to the ancient\
principles that only freeholders could be intrusted with electoral\
rights. Still other states, while closely restricting the suffrage,\
accepted the ownership of other things as well as land in fulfillment of\
the requirements. In Massachusetts, for instance, the vote was granted\
to all men who held land yielding an annual income of three pounds or\
possessed other property worth sixty pounds.\
\
The electors thus enfranchised, numerous as they were, owing to the wide\
distribution of land, often suffered from a very onerous disability. In\
many states they were able to vote only for persons of wealth because\
heavy property qualifications were imposed on public officers. In New\
Hampshire, the governor had to be worth five hundred pounds, one-half in\
land; in Massachusetts, one thousand pounds, all freehold; in Maryland,\
five thousand pounds, one thousand of which was freehold; in North\
Carolina, one thousand pounds freehold; and in South Carolina, ten\
thousand pounds freehold. A state senator in Massachusetts had to be the\
owner of a freehold worth three hundred pounds or personal property\
worth six hundred pounds; in New Jersey, one thousand pounds' worth of\
property; in North Carolina, three hundred acres of land; in South\
Carolina, two thousand pounds freehold. For members of the lower house\
of the legislature lower qualifications were required.\
\
In most of the states the suffrage or office holding or both were\
further restricted by religious provisions. No single sect was powerful\
enough to dominate after the Revolution, but, for the most part,\
Catholics and Jews were either disfranchised or excluded from office.\
North Carolina and Georgia denied the ballot to any one who was not a\
Protestant. Delaware withheld it from all who did not believe in the\
Trinity and the inspiration of the Scriptures. Massachusetts and\
Maryland limited it to Christians. Virginia and New York, advanced for\
their day, made no discrimination in government on account of religious\
opinion.\
\
=The Defense of the Old Order.=--It must not be supposed that property\
qualifications were thoughtlessly imposed at the outset or considered of\
little consequence in practice. In the beginning they were viewed as\
fundamental. As towns grew in size and the number of landless citizens\
increased, the restrictions were defended with even more vigor. In\
Massachusetts, the great Webster upheld the rights of property in\
government, saying: "It is entirely just that property should have its\
due weight and consideration in political arrangements.... The\
disastrous revolutions which the world has witnessed, those political\
thunderstorms and earthquakes which have shaken the pillars of society\
to their deepest foundations, have been revolutions against property."\
In Pennsylvania, a leader in local affairs cried out against a plan to\
remove the taxpaying limitation on the suffrage: "What does the delegate\
propose? To place the vicious vagrant, the wandering Arabs, the Tartar\
hordes of our large cities on the level with the virtuous and good man?"\
In Virginia, Jefferson himself had first believed in property\
qualifications and had feared with genuine alarm the "mobs of the great\
cities." It was near the end of the eighteenth century before he\
accepted the idea of manhood suffrage. Even then he was unable to\
convince the constitution-makers of his own state. "It is not an idle\
chimera of the brain," urged one of them, "that the possession of land\
furnishes the strongest evidence of permanent, common interest with, and\
attachment to, the community.... It is upon this foundation I wish to\
place the right of suffrage. This is the best general standard which can\
be resorted to for the purpose of determining whether the persons to be\
invested with the right of suffrage are such persons as could be,\
consistently with the safety and well-being of the community, intrusted\
with the exercise of that right."\
\
=Attacks on the Restricted Suffrage.=--The changing circumstances of\
American life, however, soon challenged the rule of those with property.\
Prominent among the new forces were the rising mercantile and business\
interests. Where the freehold qualification was applied, business men\
who did not own land were deprived of the vote and excluded from office.\
In New York, for example, the most illiterate farmer who had one hundred\
pounds' worth of land could vote for state senator and governor, while\
the landless banker or merchant could not. It is not surprising,\
therefore, to find business men taking the lead in breaking down\
freehold limitations on the suffrage. The professional classes also were\
interested in removing the barriers which excluded many of them from\
public affairs. It was a schoolmaster, Thomas Dorr, who led the popular\
uprising in Rhode Island which brought the exclusive rule by freeholders\
to an end.\
\
In addition to the business and professional classes, the mechanics of\
the towns showed a growing hostility to a system of government that\
generally barred them from voting or holding office. Though not\
numerous, they had early begun to exercise an influence on the course of\
public affairs. They had led the riots against the Stamp Act, overturned\
King George's statue, and "crammed stamps down the throats of\
collectors." When the state constitutions were framed they took a lively\
interest, particularly in New York City and Philadelphia. In June, 1776,\
the "mechanicks in union" in New York protested against putting the new\
state constitution into effect without their approval, declaring that\
the right to vote on the acceptance or rejection of a fundamental law\
"is the birthright of every man to whatever state he may belong." Though\
their petition was rejected, their spirit remained. When, a few years\
later, the federal Constitution was being framed, the mechanics watched\
the process with deep concern; they knew that one of its main objects\
was to promote trade and commerce, affecting directly their daily bread.\
During the struggle over ratification, they passed resolutions approving\
its provisions and they often joined in parades organized to stir up\
sentiment for the Constitution, even though they could not vote for\
members of the state conventions and so express their will directly.\
After the organization of trade unions they collided with the courts of\
law and thus became interested in the election of judges and lawmakers.\
\
Those who attacked the old system of class rule found a strong moral\
support in the Declaration of Independence. Was it not said that all men\
are created equal? Whoever runs may read. Was it not declared that\
governments derive their just power from the consent of the governed?\
That doctrine was applied with effect to George III and seemed\
appropriate for use against the privileged classes of Massachusetts or\
Virginia. "How do the principles thus proclaimed," asked the\
non-freeholders of Richmond, in petitioning for the ballot, "accord with\
the existing regulation of the suffrage? A regulation which, instead of\
the equality nature ordains, creates an odious distinction between\
members of the same community ... and vests in a favored class, not in\
consideration of their public services but of their private possessions,\
the highest of all privileges."\
\
=Abolition of Property Qualifications.=--By many minor victories rather\
than by any spectacular triumphs did the advocates of manhood suffrage\
carry the day. Slight gains were made even during the Revolution or\
shortly afterward. In Pennsylvania, the mechanics, by taking an active\
part in the contest over the Constitution of 1776, were able to force\
the qualification down to the payment of a small tax. Vermont came into\
the union in 1792 without any property restrictions. In the same year\
Delaware gave the vote to all men who paid taxes. Maryland, reckoned one\
of the most conservative of states, embarked on the experiment of\
manhood suffrage in 1809; and nine years later, Connecticut, equally\
conservative, decided that all taxpayers were worthy of the ballot.\
\
Five states, Massachusetts, New York, Virginia, Rhode Island, and North\
Carolina, remained obdurate while these changes were going on around\
them; finally they had to yield themselves. The last struggle in\
Massachusetts took place in the constitutional convention of 1820. There\
Webster, in the prime of his manhood, and John Adams, in the closing\
years of his old age, alike protested against such radical innovations\
as manhood suffrage. Their protests were futile. The property test was\
abolished and a small tax-paying qualification was substituted. New York\
surrendered the next year and, after trying some minor restrictions for\
five years, went completely over to white manhood suffrage in 1826.\
Rhode Island clung to her freehold qualification through thirty years of\
agitation. Then Dorr's Rebellion, almost culminating in bloodshed,\
brought about a reform in 1843 which introduced a slight tax-paying\
qualification as an alternative to the freehold. Virginia and North\
Carolina were still unconvinced. The former refused to abandon ownership\
of land as the test for political rights until 1850 and the latter until\
1856. Although religious discriminations and property qualifications for\
office holders were sometimes retained after the establishment of\
manhood suffrage, they were usually abolished along with the monopoly of\
government enjoyed by property owners and taxpayers.\
\
[Illustration: THOMAS DORR AROUSING HIS FOLLOWERS]\
\
At the end of the first quarter of the nineteenth century, the white\
male industrial workers and the mechanics of the Northern cities, at\
least, could lay aside the petition for the ballot and enjoy with the\
free farmer a voice in the government of their common country.\
"Universal democracy," sighed Carlyle, who was widely read in the United\
States, "whatever we may think of it has declared itself the inevitable\
fact of the days in which we live; and he who has any chance to instruct\
or lead in these days must begin by admitting that ... Where no\
government is wanted, save that of the parish constable, as in America\
with its boundless soil, every man being able to find work and\
recompense for himself, democracy may subsist; not elsewhere." Amid the\
grave misgivings of the first generation of statesmen, America was\
committed to the great adventure, in the populous towns of the East as\
well as in the forests and fields of the West.\
\
\
THE NEW DEMOCRACY ENTERS THE ARENA\
\
The spirit of the new order soon had a pronounced effect on the\
machinery of government and the practice of politics. The enfranchised\
electors were not long in demanding for themselves a larger share in\
administration.\
\
=The Spoils System and Rotation in Office.=--First of all they wanted\
office for themselves, regardless of their fitness. They therefore\
extended the system of rewarding party workers with government\
positions--a system early established in several states, notably New\
York and Pennsylvania. Closely connected with it was the practice of\
fixing short terms for officers and making frequent changes in\
personnel. "Long continuance in office," explained a champion of this\
idea in Pennsylvania in 1837, "unfits a man for the discharge of its\
duties, by rendering him arbitrary and aristocratic, and tends to beget,\
first life office, and then hereditary office, which leads to the\
destruction of free government." The solution offered was the historic\
doctrine of "rotation in office." At the same time the principle of\
popular election was extended to an increasing number of officials who\
had once been appointed either by the governor or the legislature. Even\
geologists, veterinarians, surveyors, and other technical officers were\
declared elective on the theory that their appointment "smacked of\
monarchy."\
\
=Popular Election of Presidential Electors.=--In a short time the spirit\
of democracy, while playing havoc with the old order in state\
government, made its way upward into the federal system. The framers of\
the Constitution, bewildered by many proposals and unable to agree on\
any single plan, had committed the choice of presidential electors to\
the discretion of the state legislatures. The legislatures, in turn,\
greedy of power, early adopted the practice of choosing the electors\
themselves; but they did not enjoy it long undisturbed. Democracy,\
thundering at their doors, demanded that they surrender the privilege to\
the people. Reluctantly they yielded, sometimes granting popular\
election and then withdrawing it. The drift was inevitable, and the\
climax came with the advent of Jacksonian democracy. In 1824, Vermont,\
New York, Delaware, South Carolina, Georgia, and Louisiana, though some\
had experimented with popular election, still left the choice of\
electors with the legislature. Eight years later South Carolina alone\
held to the old practice. Popular election had become the final word.\
The fanciful idea of an electoral college of "good and wise men,"\
selected without passion or partisanship by state legislatures acting as\
deliberative bodies, was exploded for all time; the election of the\
nation's chief magistrate was committed to the tempestuous methods of\
democracy.\
\
=The Nominating Convention.=--As the suffrage was widened and the\
popular choice of presidential electors extended, there arose a violent\
protest against the methods used by the political parties in nominating\
candidates. After the retirement of Washington, both the Republicans and\
the Federalists found it necessary to agree upon their favorites before\
the election, and they adopted a colonial device--the pre-election\
caucus. The Federalist members of Congress held a conference and\
selected their candidate, and the Republicans followed the example. In\
a short time the practice of nominating by a "congressional caucus"\
became a recognized institution. The election still remained with the\
people; but the power of picking candidates for their approval passed\
into the hands of a small body of Senators and Representatives.\
\
\
A reaction against this was unavoidable. To friends of "the plain\
people," like Andrew Jackson, it was intolerable, all the more so\
because the caucus never favored him with the nomination. More\
conservative men also found grave objections to it. They pointed out\
that, whereas the Constitution intended the President to be an\
independent officer, he had now fallen under the control of a caucus of\
congressmen. The supremacy of the legislative branch had been obtained\
by an extra-legal political device. To such objections were added\
practical considerations. In 1824, when personal rivalry had taken the\
place of party conflicts, the congressional caucus selected as the\
candidate, William H. Crawford, of Georgia, a man of distinction but no\
great popularity, passing by such an obvious hero as General Jackson.\
The followers of the General were enraged and demanded nothing short of\
the death of "King Caucus." Their clamor was effective. Under their\
attacks, the caucus came to an ignominious end.\
\
In place of it there arose in 1831 a new device, the national nominating\
convention, composed of delegates elected by party voters for the sole\
purpose of nominating candidates. Senators and Representatives were\
still prominent in the party councils, but they were swamped by hundreds\
of delegates "fresh from the people," as Jackson was wont to say. In\
fact, each convention was made up mainly of office holders and office\
seekers, and the new institution was soon denounced as vigorously as\
King Caucus had been, particularly by statesmen who failed to obtain a\
nomination. Still it grew in strength and by 1840 was firmly\
established.\
\
=The End of the Old Generation.=--In the election of 1824, the\
representatives of the "aristocracy" made their last successful stand.\
Until then the leadership by men of "wealth and talents" had been\
undisputed. There had been five Presidents--Washington, John Adams,\
Jefferson, Madison, and Monroe--all Eastern men brought up in prosperous\
families with the advantages of culture which come from leisure and the\
possession of life's refinements. None of them had ever been compelled\
to work with his hands for a livelihood. Four of them had been\
slaveholders. Jefferson was a philosopher, learned in natural science, a\
master of foreign languages, a gentleman of dignity and grace of manner,\
notwithstanding his studied simplicity. Madison, it was said, was armed\
"with all the culture of his century." Monroe was a graduate of William\
and Mary, a gentleman of the old school. Jefferson and his three\
successors called themselves Republicans and professed a genuine faith\
in the people but they were not "of the people" themselves; they were\
not sons of the soil or the workshop. They were all men of "the grand\
\
old order of society" who gave finish and style even to popular\
government.\
\
Monroe was the last of the Presidents belonging to the heroic epoch of\
the Revolution. He had served in the war for independence, in the\
Congress under the Articles of Confederation, and in official capacity\
after the adoption of the Constitution. In short, he was of the age that\
had wrought American independence and set the government afloat. With\
his passing, leadership went to a new generation; but his successor,\
John Quincy Adams, formed a bridge between the old and the new in that\
he combined a high degree of culture with democratic sympathies.\
Washington had died in 1799, preceded but a few months by Patrick Henry\
and followed in four years by Samuel Adams. Hamilton had been killed in\
a duel with Burr in 1804. Thomas Jefferson and John Adams were yet alive\
in 1824 but they were soon to pass from the scene, reconciled at last,\
full of years and honors. Madison was in dignified retirement, destined\
to live long enough to protest against the doctrine of nullification\
proclaimed by South Carolina before death carried him away at the ripe\
old age of eighty-five.\
\
=The Election of John Quincy Adams (1824).=--The campaign of 1824 marked\
the end of the "era of good feeling" inaugurated by the collapse of the\
Federalist party after the election of 1816. There were four leading\
candidates, John Quincy Adams, Andrew Jackson, Henry Clay, and W.H.\
Crawford. The result of the election was a division of the electoral\
votes into four parts and no one received a majority. Under the\
Constitution, therefore, the selection of President passed to the House\
of Representatives. Clay, who stood at the bottom of the poll, threw his\
weight to Adams and assured his triumph, much to the chagrin of\
Jackson's friends. They thought, with a certain justification, that\
inasmuch as the hero of New Orleans had received the largest electoral\
vote, the House was morally bound to accept the popular judgment and\
make him President. Jackson shook hands cordially with Adams on the day\
of the inauguration, but never forgave him for being elected.\
\
While Adams called himself a Republican in politics and often spoke of\
"the rule of the people," he was regarded by Jackson's followers as "an\
aristocrat." He was not a son of the soil. Neither was he acquainted at\
first hand with the labor of farmers and mechanics. He had been educated\
at Harvard and in Europe. Like his illustrious father, John Adams, he\
was a stern and reserved man, little given to seeking popularity.\
Moreover, he was from the East and the frontiersmen of the West regarded\
him as a man "born with a silver spoon in his mouth." Jackson's\
supporters especially disliked him because they thought their hero\
entitled to the presidency. Their anger was deepened when Adams\
appointed Clay to the office of Secretary of State; and they set up a\
cry that there had been a "deal" by which Clay had helped to elect Adams\
to get office for himself.\
\
Though Adams conducted his administration with great dignity and in a\
fine spirit of public service, he was unable to overcome the opposition\
which he encountered on his election to office or to win popularity in\
the West and South. On the contrary, by advocating government assistance\
in building roads and canals and public grants in aid of education,\
arts, and sciences, he ran counter to the current which had set in\
against appropriations of federal funds for internal improvements. By\
signing the Tariff Bill of 1828, soon known as the "Tariff of\
Abominations," he made new enemies without adding to his friends in New\
York, Pennsylvania, and Ohio where he sorely needed them. Handicapped by\
the false charge that he had been a party to a "corrupt bargain" with\
Clay to secure his first election; attacked for his advocacy of a high\
protective tariff; charged with favoring an "aristocracy of\
office-holders" in Washington on account of his refusal to discharge\
government clerks by the wholesale, Adams was retired from the White\
House after he had served four years.\
\
=The Triumph of Jackson in 1828.=--Probably no candidate for the\
presidency ever had such passionate popular support as Andrew Jackson\
had in 1828. He was truly a man of the people. Born of poor parents in\
the upland region of South Carolina, schooled in poverty and adversity,\
without the advantages of education or the refinements of cultivated\
leisure, he seemed the embodiment of the spirit of the new American\
democracy. Early in his youth he had gone into the frontier of Tennessee\
where he soon won a name as a fearless and intrepid Indian fighter. On\
the march and in camp, he endeared himself to his men by sharing their\
hardships, sleeping on the ground with them, and eating parched corn\
when nothing better could be found for the privates. From local\
prominence he sprang into national fame by his exploit at the battle of\
New Orleans. His reputation as a military hero was enhanced by the\
feeling that he had been a martyr to political treachery in 1824. The\
farmers of the West and South claimed him as their own. The mechanics of\
the Eastern cities, newly enfranchised, also looked upon him as their\
friend. Though his views on the tariff, internal improvements, and other\
issues before the country were either vague or unknown, he was readily\
elected President.\
\
The returns of the electoral vote in 1828 revealed the sources of\
Jackson's power. In New England, he received but one ballot, from\
Maine; he had a majority of the electors in New York and all of them in\
Pennsylvania; and he carried every state south of Maryland and beyond\
the Appalachians. Adams did not get a single electoral vote in the South\
and West. The prophecy of the Hartford convention had been fulfilled.\
\
[Illustration: ANDREW JACKSON]\
\
When Jackson took the oath of office on March 4, 1829, the government of\
the United States entered into a new era. Until this time the\
inauguration of a President--even that of Jefferson, the apostle of\
simplicity--had brought no rude shock to the course of affairs at the\
capital. Hitherto the installation of a President meant that an\
old-fashioned gentleman, accompanied by a few servants, had driven to\
the White House in his own coach, taken the oath with quiet dignity,\
appointed a few new men to the higher posts, continued in office the\
long list of regular civil employees, and begun his administration with\
respectable decorum. Jackson changed all this. When he was inaugurated,\
men and women journeyed hundreds of miles to witness the ceremony. Great\
throngs pressed into the White House, "upset the bowls of punch, broke\
the glasses, and stood with their muddy boots on the satin-covered\
chairs to see the people's President." If Jefferson's inauguration was,\
as he called it, the "great revolution," Jackson's inauguration was a\
cataclysm.\
\
\
THE NEW DEMOCRACY AT WASHINGTON\
\
=The Spoils System.=--The staid and respectable society of Washington\
was disturbed by this influx of farmers and frontiersmen. To speak of\
politics became "bad form" among fashionable women. The clerks and\
civil servants of the government who had enjoyed long and secure tenure\
of office became alarmed at the clamor of new men for their positions.\
Doubtless the major portion of them had opposed the election of Jackson\
and looked with feelings akin to contempt upon him and his followers.\
With a hunter's instinct, Jackson scented his prey. Determined to have\
none but his friends in office, he made a clean sweep, expelling old\
employees to make room for men "fresh from the people." This was a new\
custom. Other Presidents had discharged a few officers for engaging in\
opposition politics. They had been careful in making appointments not to\
choose inveterate enemies; but they discharged relatively few men on\
account of their political views and partisan activities.\
\
By wholesale removals and the frank selection of officers on party\
grounds--a practice already well intrenched in New York--Jackson\
established the "spoils system" at Washington. The famous slogan, "to\
the victor belong the spoils of victory," became the avowed principle of\
the national government. Statesmen like Calhoun denounced it; poets like\
James Russell Lowell ridiculed it; faithful servants of the government\
suffered under it; but it held undisturbed sway for half a century\
thereafter, each succeeding generation outdoing, if possible, its\
predecessor in the use of public office for political purposes. If any\
one remarked that training and experience were necessary qualifications\
for important public positions, he met Jackson's own profession of\
faith: "The duties of any public office are so simple or admit of being\
made so simple that any man can in a short time become master of them."\
\
=The Tariff and Nullification.=--Jackson had not been installed in power\
very long before he was compelled to choose between states' rights and\
nationalism. The immediate occasion of the trouble was the tariff--a\
matter on which Jackson did not have any very decided views. His mind\
did not run naturally to abstruse economic questions; and owing to the\
divided opinion of the country it was "good politics" to be vague and\
ambiguous in the controversy. Especially was this true, because the\
tariff issue was threatening to split the country into parties again.\
\
_The Development of the Policy of "Protection."_--The war of 1812 and\
the commercial policies of England which followed it had accentuated the\
need for American economic independence. During that conflict, the\
United States, cut off from English manufactures as during the\
Revolution, built up home industries to meet the unusual call for iron,\
steel, cloth, and other military and naval supplies as well as the\
demands from ordinary markets. Iron foundries and textile mills sprang\
up as in the night; hundreds of business men invested fortunes in\
industrial enterprises so essential to the military needs of the\
government; and the people at large fell into the habit of buying\
American-made goods again. As the London _Times_ tersely observed of the\
Americans, "their first war with England made them independent; their\
second war made them formidable."\
\
In recognition of this state of affairs, the tariff of 1816 was\
designed: _first_, to prevent England from ruining these "infant\
industries" by dumping the accumulated stores of years suddenly upon\
American markets; and, _secondly_, to enlarge in the manufacturing\
centers the demand for American agricultural produce. It accomplished\
the purposes of its framers. It kept in operation the mills and furnaces\
so recently built. It multiplied the number of industrial workers and\
enhanced the demand for the produce of the soil. It brought about\
another very important result. It turned the capital and enterprise of\
New England from shipping to manufacturing, and converted her statesmen,\
once friends of low tariffs, into ardent advocates of protection.\
\
In the early years of the nineteenth century, the Yankees had bent their\
energies toward building and operating ships to carry produce from\
America to Europe and manufactures from Europe to America. For this\
reason, they had opposed the tariff of 1816 calculated to increase\
domestic production and cut down the carrying trade. Defeated in their\
efforts, they accepted the inevitable and turned to manufacturing. Soon\
they were powerful friends of protection for American enterprise. As the\
money invested and the labor employed in the favored industries\
increased, the demand for continued and heavier protection grew apace.\
Even the farmers who furnished raw materials, like wool, flax, and hemp,\
began to see eye to eye with the manufacturers. So the textile interests\
of New England, the iron masters of Connecticut, New Jersey, and\
Pennsylvania, the wool, hemp, and flax growers of Ohio, Kentucky, and\
Tennessee, and the sugar planters of Louisiana developed into a\
formidable combination in support of a high protective tariff.\
\
_The Planting States Oppose the Tariff._--In the meantime, the cotton\
states on the seaboard had forgotten about the havoc wrought during the\
Napoleonic wars when their produce rotted because there were no ships to\
carry it to Europe. The seas were now open. The area devoted to cotton\
had swiftly expanded as Alabama, Mississippi, and Louisiana were opened\
up. Cotton had in fact become "king" and the planters depended for their\
prosperity, as they thought, upon the sale of their staple to English\
manufacturers whose spinning and weaving mills were the wonder of the\
world. Manufacturing nothing and having to buy nearly everything except\
farm produce and even much of that for slaves, the planters naturally\
wanted to purchase manufactures in the cheapest market, England, where\
they sold most of their cotton. The tariff, they contended, raised the\
price of the goods they had to buy and was thus in fact a tribute laid\
on them for the benefit of the Northern mill owners.\
\
_The Tariff of Abominations._--They were overborne, however, in 1824 and\
again in 1828 when Northern manufacturers and Western farmers forced\
Congress to make an upward revision of the tariff. The Act of 1828 known\
as "the Tariff of Abominations," though slightly modified in 1832, was\
"the straw which broke the camel's back." Southern leaders turned in\
rage against the whole system. The legislatures of Virginia, North\
Carolina, South Carolina, Georgia, and Alabama denounced it; a general\
convention of delegates held at Augusta issued a protest of defiance\
against it; and South Carolina, weary of verbal battles, decided to\
prevent its enforcement.\
\
_South Carolina Nullifies the Tariff._--The legislature of that state,\
on October 26, 1832, passed a bill calling for a state convention which\
duly assembled in the following month. In no mood for compromise, it\
adopted the famous Ordinance of Nullification after a few days' debate.\
Every line of this document was clear and firm. The tariff, it opened,\
gives "bounties to classes and individuals ... at the expense and to the\
injury and oppression of other classes and individuals"; it is a\
violation of the Constitution of the United States and therefore null\
and void; its enforcement in South Carolina is unlawful; if the federal\
government attempts to coerce the state into obeying the law, "the\
people of this state will thenceforth hold themselves absolved from all\
further obligations to maintain or preserve their political connection\
with the people of the other states and will forthwith proceed to\
organize a separate government and do all other acts and things which\
sovereign and independent states may of right do."\
\
_Southern States Condemn Nullification._--The answer of the country to\
this note of defiance, couched in the language used in the Kentucky\
resolutions and by the New England Federalists during the war of 1812,\
was quick and positive. The legislatures of the Southern states, while\
condemning the tariff, repudiated the step which South Carolina had\
taken. Georgia responded: "We abhor the doctrine of nullification as\
neither a peaceful nor a constitutional remedy." Alabama found it\
"unsound in theory and dangerous in practice." North Carolina replied\
that it was "revolutionary in character, subversive of the Constitution\
of the United States." Mississippi answered: "It is disunion by\
force--it is civil war." Virginia spoke more softly, condemning the\
tariff and sustaining the principle of the Virginia resolutions but\
denying that South Carolina could find in them any sanction for her\
proceedings.\
\
_Jackson Firmly Upholds the Union._--The eyes of the country were turned\
upon Andrew Jackson. It was known that he looked with no friendly\
feelings upon nullification, for, at a Jefferson dinner in the spring of\
1830 while the subject was in the air, he had with laconic firmness\
announced a toast: "Our federal union; it must be preserved." When two\
years later the open challenge came from South Carolina, he replied that\
he would enforce the law, saying with his frontier directness: "If a\
single drop of blood shall be shed there in opposition to the laws of\
the United States, I will hang the first man I can lay my hands on\
engaged in such conduct upon the first tree that I can reach." He made\
ready to keep his word by preparing for the use of military and naval\
forces in sustaining the authority of the federal government. Then in a\
long and impassioned proclamation to the people of South Carolina he\
pointed out the national character of the union, and announced his\
solemn resolve to preserve it by all constitutional means. Nullification\
he branded as "incompatible with the existence of the union,\
contradicted expressly by the letter of the Constitution, unauthorized\
by its spirit, inconsistent with every principle on which it was\
founded, and destructive of the great objects for which it was formed."\
\
_A Compromise._--In his messages to Congress, however, Jackson spoke the\
language of conciliation. A few days before issuing his proclamation he\
suggested that protection should be limited to the articles of domestic\
manufacture indispensable to safety in war time, and shortly afterward\
he asked for new legislation to aid him in enforcing the laws. With two\
propositions before it, one to remove the chief grounds for South\
Carolina's resistance and the other to apply force if it was continued,\
Congress bent its efforts to avoid a crisis. On February 12, 1833,\
Henry Clay laid before the Senate a compromise tariff bill providing for\
the gradual reduction of the duties until by 1842 they would reach the\
level of the law which Calhoun had supported in 1816. About the same\
time the "force bill," designed to give the President ample authority in\
executing the law in South Carolina, was taken up. After a short but\
acrimonious debate, both measures were passed and signed by President\
Jackson on the same day, March 2. Looking upon the reduction of the\
tariff as a complete vindication of her policy and an undoubted victory,\
South Carolina rescinded her ordinance and enacted another nullifying\
the force bill.\
\
[Illustration: _From an old print._\
\
DANIEL WEBSTER]\
\
_The Webster-Hayne Debate._--Where the actual victory lay in this\
quarrel, long the subject of high dispute, need not concern us to-day.\
Perhaps the chief result of the whole affair was a clarification of the\
issue between the North and the South--a definite statement of the\
principles for which men on both sides were years afterward to lay down\
their lives. On behalf of nationalism and a perpetual union, the stanch\
old Democrat from Tennessee had, in his proclamation on nullification,\
spoken a language that admitted of only one meaning. On behalf of\
nullification, Senator Hayne, of South Carolina, a skilled lawyer and\
courtly orator, had in a great speech delivered in the Senate in\
January, 1830, set forth clearly and cogently the doctrine that the\
union is a compact among sovereign states from which the parties may\
lawfully withdraw. It was this address that called into the arena\
Daniel Webster, Senator from Massachusetts, who, spreading the mantle\
of oblivion over the Hartford convention, delivered a reply to Hayne\
that has been reckoned among the powerful orations of all time--a plea\
for the supremacy of the Constitution and the national character of the\
union.\
\
=The War on the United States Bank.=--If events forced the issue of\
nationalism and nullification upon Jackson, the same could not be said\
of his attack on the bank. That institution, once denounced by every\
true Jeffersonian, had been reestablished in 1816 under the\
administration of Jefferson's disciple, James Madison. It had not been\
in operation very long, however, before it aroused bitter opposition,\
especially in the South and the West. Its notes drove out of circulation\
the paper currency of unsound banks chartered by the states, to the\
great anger of local financiers. It was accused of favoritism in making\
loans, of conferring special privileges upon politicians in return for\
their support at Washington. To all Jackson's followers it was "an\
insidious money power." One of them openly denounced it as an\
institution designed "to strengthen the arm of wealth and counterpoise\
the influence of extended suffrage in the disposition of public\
affairs."\
\
This sentiment President Jackson fully shared. In his first message to\
Congress he assailed the bank in vigorous language. He declared that its\
constitutionality was in doubt and alleged that it had failed to\
establish a sound and uniform currency. If such an institution was\
necessary, he continued, it should be a public bank, owned and managed\
by the government, not a private concern endowed with special privileges\
by it. In his second and third messages, Jackson came back to the\
subject, leaving the decision, however, to "an enlightened people and\
their representatives."\
\
Moved by this frank hostility and anxious for the future, the bank\
applied to Congress for a renewal of its charter in 1832, four years\
before the expiration of its life. Clay, with his eye upon the\
presidency and an issue for the campaign, warmly supported the\
application. Congress, deeply impressed by his leadership, passed the\
bill granting the new charter, and sent the open defiance to Jackson.\
His response was an instant veto. The battle was on and it raged with\
fury until the close of his second administration, ending in the\
destruction of the bank, a disordered currency, and a national panic.\
\
In his veto message, Jackson attacked the bank as unconstitutional and\
even hinted at corruption. He refused to assent to the proposition that\
the Supreme Court had settled the question of constitutionality by the\
decision in the McCulloch case. "Each public officer," he argued, "who\
takes an oath to support the Constitution, swears that he will support\
it as he understands it, not as it is understood by others."\
\
Not satisfied with his veto and his declaration against the bank,\
Jackson ordered the Secretary of the Treasury to withdraw the government\
deposits which formed a large part of the institution's funds. This\
action he followed up by an open charge that the bank had used money\
shamefully to secure the return of its supporters to Congress. The\
Senate, stung by this charge, solemnly resolved that Jackson had\
"assumed upon himself authority and power not conferred by the\
Constitution and laws, but in derogation of both."\
\
The effects of the destruction of the bank were widespread. When its\
charter expired in 1836, banking was once more committed to the control\
of the states. The state legislatures, under a decision rendered by the\
Supreme Court after the death of Marshall, began to charter banks under\
state ownership and control, with full power to issue paper money--this\
in spite of the provision in the Constitution that states shall not\
issue bills of credit or make anything but gold and silver coin legal\
tender in the payment of debts. Once more the country was flooded by\
paper currency of uncertain value. To make matters worse, Jackson\
adopted the practice of depositing huge amounts of government funds in\
these banks, not forgetting to render favors to those institutions which\
supported him in politics--"pet banks," as they were styled at the\
time. In 1837, partially, though by no means entirely, as a result of\
the abolition of the bank, the country was plunged into one of the most\
disastrous panics which it ever experienced.\
\
=Internal Improvements Checked.=--The bank had presented to Jackson a\
very clear problem--one of destruction. Other questions were not so\
simple, particularly the subject of federal appropriations in aid of\
roads and other internal improvements. Jefferson had strongly favored\
government assistance in such matters, but his administration was\
followed by a reaction. Both Madison and Monroe vetoed acts of Congress\
appropriating public funds for public roads, advancing as their reason\
the argument that the Constitution authorized no such laws. Jackson,\
puzzled by the clamor on both sides, followed their example without\
making the constitutional bar absolute. Congress, he thought, might\
lawfully build highways of a national and military value, but he\
strongly deprecated attacks by local interests on the federal treasury.\
\
=The Triumph of the Executive Branch.=--Jackson's reelection in 1832\
served to confirm his opinion that he was the chosen leader of the\
people, freed and instructed to ride rough shod over Congress and even\
the courts. No President before or since ever entertained in times of\
peace such lofty notions of executive prerogative. The entire body of\
federal employees he transformed into obedient servants of his wishes, a\
sign or a nod from him making and undoing the fortunes of the humble and\
the mighty. His lawful cabinet of advisers, filling all of the high\
posts in the government, he treated with scant courtesy, preferring\
rather to secure his counsel and advice from an unofficial body of\
friends and dependents who, owing to their secret methods and back\
stairs arrangements, became known as "the kitchen cabinet." Under the\
leadership of a silent, astute, and resourceful politician, Amos\
Kendall, this informal gathering of the faithful both gave and carried\
out decrees and orders, communicating the President's lightest wish or\
strictest command to the uttermost part of the country. Resolutely and\
in the face of bitter opposition Jackson had removed the deposits from\
the United States Bank. When the Senate protested against this arbitrary\
conduct, he did not rest until it was forced to expunge the resolution\
of condemnation; in time one of his lieutenants with his own hands was\
able to tear the censure from the records. When Chief Justice Marshall\
issued a decree against Georgia which did not suit him, Jackson,\
according to tradition, blurted out that Marshall could go ahead and\
enforce his own orders. To the end he pursued his willful way, finally\
even choosing his own successor.\
\
\
THE RISE OF THE WHIGS\
\
=Jackson's Measures Arouse Opposition.=--Measures so decided, policies\
so radical, and conduct so high-handed could not fail to arouse against\
Jackson a deep and exasperated opposition. The truth is the conduct of\
his entire administration profoundly disturbed the business and finances\
of the country. It was accompanied by conditions similar to those which\
existed under the Articles of Confederation. A paper currency, almost as\
unstable and irritating as the worthless notes of revolutionary days,\
flooded the country, hindering the easy transaction of business. The use\
of federal funds for internal improvements, so vital to the exchange of\
commodities which is the very life of industry, was blocked by executive\
vetoes. The Supreme Court, which, under Marshall, had held refractory\
states to their obligations under the Constitution, was flouted; states'\
rights judges, deliberately selected by Jackson for the bench, began to\
sap and undermine the rulings of Marshall. The protective tariff, under\
which the textile industry of New England, the iron mills of\
Pennsylvania, and the wool, flax, and hemp farms of the West had\
flourished, had received a severe blow in the compromise of 1833 which\
promised a steady reduction of duties. To cap the climax, Jackson's\
party, casting aside the old and reputable name of Republican, boldly\
chose for its title the term "Democrat," throwing down the gauntlet to\
every conservative who doubted the omniscience of the people. All these\
things worked together to evoke an opposition that was sharp and\
determined.\
\
[Illustration: AN OLD CARTOON RIDICULING CLAY'S TARIFF AND INTERNAL\
IMPROVEMENT PROGRAM]\
\
=Clay and the National Republicans.=--In this opposition movement,\
leadership fell to Henry Clay, a son of Kentucky, rather than to Daniel\
Webster of Massachusetts. Like Jackson, Clay was born in a home haunted\
by poverty. Left fatherless early and thrown upon his own resources, he\
went from Virginia into Kentucky where by sheer force of intellect he\
rose to eminence in the profession of law. Without the martial gifts or\
the martial spirit of Jackson, he slipped more easily into the social\
habits of the East at the same time that he retained his hold on the\
affections of the boisterous West. Farmers of Ohio, Indiana, and\
Kentucky loved him; financiers of New York and Philadelphia trusted him.\
He was thus a leader well fitted to gather the forces of opposition\
into union against Jackson.\
\
Around Clay's standard assembled a motley collection, representing every\
species of political opinion, united by one tie only--hatred for "Old\
Hickory." Nullifiers and less strenuous advocates of states' rights were\
yoked with nationalists of Webster's school; ardent protectionists were\
bound together with equally ardent free traders, all fraternizing in one\
grand confusion of ideas under the title of "National Republicans." Thus\
the ancient and honorable term selected by Jefferson and his party, now\
abandoned by Jacksonian Democracy, was adroitly adopted to cover the\
supporters of Clay. The platform of the party, however, embraced all the\
old Federalist principles: protection for American industry; internal\
improvements; respect for the Supreme Court; resistance to executive\
tyranny; and denunciation of the spoils system. Though Jackson was\
easily victorious in 1832, the popular vote cast for Clay should have\
given him some doubts about the faith of "the whole people" in the\
wisdom of his "reign."\
\
=Van Buren and the Panic of 1837.=--Nothing could shake the General's\
superb confidence. At the end of his second term he insisted on\
selecting his own successor; at a national convention, chosen by party\
voters, but packed with his office holders and friends, he nominated\
Martin Van Buren of New York. Once more he proved his strength by\
carrying the country for the Democrats. With a fine flourish, he\
attended the inauguration of Van Buren and then retired, amid the\
applause and tears of his devotees, to the Hermitage, his home in\
Tennessee.\
\
Fortunately for him, Jackson escaped the odium of a disastrous panic\
which struck the country with terrible force in the following summer.\
Among the contributory causes of this crisis, no doubt, were the\
destruction of the bank and the issuance of the "specie circular" of\
\
1836 which required the purchasers of public lands to pay for them in\
coin, instead of the paper notes of state banks. Whatever the dominating\
cause, the ruin was widespread. Bank after bank went under; boom towns\
in the West collapsed; Eastern mills shut down; and working people in\
the industrial centers, starving from unemployment, begged for relief.\
Van Buren braved the storm, offering no measure of reform or assistance\
to the distracted people. He did seek security for government funds by\
suggesting the removal of deposits from private banks and the\
establishment of an independent treasury system, with government\
depositaries for public funds, in several leading cities. This plan was\
finally accepted by Congress in 1840.\
\
Had Van Buren been a captivating figure he might have lived down the\
discredit of the panic unjustly laid at his door; but he was far from\
being a favorite with the populace. Though a man of many talents, he\
owed his position to the quiet and adept management of Jackson rather\
than to his own personal qualities. The men of the frontier did not care\
for him. They suspected that he ate from "gold plate" and they could not\
forgive him for being an astute politician from New York. Still the\
Democratic party, remembering Jackson's wishes, renominated him\
unanimously in 1840 and saw him go down to utter defeat.\
\
=The Whigs and General Harrison.=--By this time, the National\
Republicans, now known as Whigs--a title taken from the party of\
opposition to the Crown in England, had learned many lessons. Taking a\
leaf out of the Democratic book, they nominated, not Clay of Kentucky,\
well known for his views on the bank, the tariff, and internal\
improvements, but a military hero, General William Henry Harrison, a man\
of uncertain political opinions. Harrison, a son of a Virginia signer of\
the Declaration of Independence, sprang into public view by winning a\
battle more famous than important, "Tippecanoe"--a brush with the\
Indians in Indiana. He added to his laurels by rendering praiseworthy\
services during the war of 1812. When days of peace returned he was\
rewarded by a grateful people with a seat in Congress. Then he retired\
to quiet life in a little village near Cincinnati. Like Jackson he was\
held to be a son of the South and the West. Like Jackson he was a\
military hero, a lesser light, but still a light. Like Old Hickory he\
rode into office on a tide of popular feeling against an Eastern man\
accused of being something of an aristocrat. His personal popularity was\
sufficient. The Whigs who nominated him shrewdly refused to adopt a\
platform or declare their belief in anything. When some Democrat\
asserted that Harrison was a backwoodsman whose sole wants were a jug of\
hard cider and a log cabin, the Whigs treated the remark not as an\
insult but as proof positive that Harrison deserved the votes of Jackson\
men. The jug and the cabin they proudly transformed into symbols of the\
campaign, and won for their chieftain 234 electoral votes, while Van\
Buren got only sixty.\
\
=Harrison and Tyler.=--The Hero of Tippecanoe was not long to enjoy the\
fruits of his victory. The hungry horde of Whig office seekers descended\
upon him like wolves upon the fold. If he went out they waylaid him; if\
he stayed indoors, he was besieged; not even his bed chamber was spared.\
He was none too strong at best and he took a deep cold on the day of his\
inauguration. Between driving out Democrats and appeasing Whigs, he fell\
mortally ill. Before the end of a month he lay dead at the capitol.\
\
Harrison's successor, John Tyler, the Vice President, whom the Whigs had\
nominated to catch votes in Virginia, was more of a Democrat than\
anything else, though he was not partisan enough to please anybody. The\
Whigs railed at him because he would not approve the founding of another\
United States Bank. The Democrats stormed at him for refusing, until\
near the end of his term, to sanction the annexation of Texas, which had\
declared its independence of Mexico in 1836. His entire administration,\
marked by unseemly wrangling, produced only two measures of importance.\
The Whigs, flushed by victory, with the aid of a few protectionist\
Democrats, enacted, in 1842, a new tariff law destroying the compromise\
which had brought about the truce between the North and the South, in\
the days of nullification. The distinguished leader of the Whigs, Daniel\
Webster, as Secretary of State, in negotiation with Lord Ashburton\
representing Great Britain, settled the long-standing dispute between\
the two countries over the Maine boundary. A year after closing this\
chapter in American diplomacy, Webster withdrew to private life, leaving\
the President to endure alone the buffets of political fortune.\
\
To the end, the Whigs regarded Tyler as a traitor to their cause; but\
the judgment of history is that it was a case of the biter bitten. They\
had nominated him for the vice presidency as a man of views acceptable\
to Southern Democrats in order to catch their votes, little reckoning\
with the chances of his becoming President. Tyler had not deceived them\
and, thoroughly soured, he left the White House in 1845 not to appear in\
public life again until the days of secession, when he espoused the\
Southern confederacy. Jacksonian Democracy, with new leadership, serving\
a new cause--slavery--was returned to power under James K. Polk, a\
friend of the General from Tennessee. A few grains of sand were to run\
through the hour glass before the Whig party was to be broken and\
scattered as the Federalists had been more than a generation before.\
\
\
THE INTERACTION OF AMERICAN AND EUROPEAN OPINION\
\
=Democracy in England and France.=--During the period of Jacksonian\
Democracy, as in all epochs of ferment, there was a close relation\
between the thought of the New World and the Old. In England, the\
successes of the American experiment were used as arguments in favor of\
overthrowing the aristocracy which George III had manipulated with such\
effect against America half a century before. In the United States, on\
the other hand, conservatives like Chancellor Kent, the stout opponent\
of manhood suffrage in New York, cited the riots of the British working\
classes as a warning against admitting the same classes to a share in\
the government of the United States. Along with the agitation of opinion\
went epoch-making events. In 1832, the year of Jackson's second\
triumph, the British Parliament passed its first reform bill, which\
conferred the ballot--not on workingmen as yet--but on mill owners and\
shopkeepers whom the landlords regarded with genuine horror. The initial\
step was thus taken in breaking down the privileges of the landed\
aristocracy and the rich merchants of England.\
\
About the same time a popular revolution occurred in France. The Bourbon\
family, restored to the throne of France by the allied powers after\
their victory over Napoleon in 1815, had embarked upon a policy of\
arbitrary government. To use the familiar phrase, they had learned\
nothing and forgotten nothing. Charles X, who came to the throne in\
1824, set to work with zeal to undo the results of the French\
Revolution, to stifle the press, restrict the suffrage, and restore the\
clergy and the nobility to their ancient rights. His policy encountered\
equally zealous opposition and in 1830 he was overthrown. The popular\
party, under the leadership of Lafayette, established, not a republic as\
some of the radicals had hoped, but a "liberal" middle-class monarchy\
under Louis Philippe. This second French Revolution made a profound\
impression on Americans, convincing them that the whole world was moving\
toward democracy. The mayor, aldermen, and citizens of New York City\
joined in a great parade to celebrate the fall of the Bourbons. Mingled\
with cheers for the new order in France were hurrahs for "the people's\
own, Andrew Jackson, the Hero of New Orleans and President of the United\
States!"\
\
=European Interest in America.=--To the older and more settled\
Europeans, the democratic experiment in America was either a menace or\
an inspiration. Conservatives viewed it with anxiety; liberals with\
optimism. Far-sighted leaders could see that the tide of democracy was\
rising all over the world and could not be stayed. Naturally the country\
that had advanced furthest along the new course was the place in which\
to find arguments for and against proposals that Europe should make\
experiments of the same character.\
\
=De Tocqueville's _Democracy in America_.=--In addition to the casual\
traveler there began to visit the United States the thoughtful observer\
bent on finding out what manner of nation this was springing up in the\
wilderness. Those who looked with sympathy upon the growing popular\
forces of England and France found in the United States, in spite of\
many blemishes and defects, a guarantee for the future of the people's\
rule in the Old World. One of these, Alexis de Tocqueville, a French\
liberal of mildly democratic sympathies, made a journey to this country\
in 1831; he described in a very remarkable volume, _Democracy in\
America_, the grand experiment as he saw it. On the whole he was\
convinced. After examining with a critical eye the life and labor of the\
American people, as well as the constitutions of the states and the\
nation, he came to the conclusion that democracy with all its faults was\
both inevitable and successful. Slavery he thought was a painful\
contrast to the other features of American life, and he foresaw what\
proved to be the irrepressible conflict over it. He believed that\
through blundering the people were destined to learn the highest of all\
arts, self-government on a grand scale. The absence of a leisure class,\
devoted to no calling or profession, merely enjoying the refinements of\
life and adding to its graces--the flaw in American culture that gave\
deep distress to many a European leader--de Tocqueville thought a\
necessary virtue in the republic. "Amongst a democratic people where\
there is no hereditary wealth, every man works to earn a living, or has\
worked, or is born of parents who have worked. A notion of labor is\
therefore presented to the mind on every side as the necessary, natural,\
and honest condition of human existence." It was this notion of a\
government in the hands of people who labored that struck the French\
publicist as the most significant fact in the modern world.\
\
=Harriet Martineau's Visit to America.=--This phase of American life\
also profoundly impressed the brilliant English writer, Harriet\
Martineau. She saw all parts of the country, the homes of the rich and\
the log cabins of the frontier; she traveled in stagecoaches, canal\
boats, and on horseback; and visited sessions of Congress and auctions\
at slave markets. She tried to view the country impartially and the\
thing that left the deepest mark on her mind was the solidarity of the\
people in one great political body. "However various may be the tribes\
of inhabitants in those states, whatever part of the world may have been\
their birthplace, or that of their fathers, however broken may be their\
language, however servile or noble their employments, however exalted or\
despised their state, all are declared to be bound together by equal\
political obligations.... In that self-governing country all are held to\
have an equal interest in the principles of its institutions and to be\
bound in equal duty to watch their workings." Miss Martineau was also\
impressed with the passion of Americans for land ownership and\
contrasted the United States favorably with England where the tillers of\
the soil were either tenants or laborers for wages.\
\
=Adverse Criticism.=--By no means all observers and writers were\
convinced that America was a success. The fastidious traveler, Mrs.\
Trollope, who thought the English system of church and state was ideal,\
saw in the United States only roughness and ignorance. She lamented the\
"total and universal want of manners both in males and females," adding\
that while "they appear to have clear heads and active intellects,"\
there was "no charm, no grace in their conversation." She found\
everywhere a lack of reverence for kings, learning, and rank. Other\
critics were even more savage. The editor of the _Foreign Quarterly_\
petulantly exclaimed that the United States was "a brigand\
confederation." Charles Dickens declared the country to be "so maimed\
and lame, so full of sores and ulcers that her best friends turn from\
the loathsome creature in disgust." Sydney Smith, editor of the\
_Edinburgh Review_, was never tired of trying his caustic wit at the\
expense of America. "Their Franklins and Washingtons and all the other\
sages and heroes of their revolution were born and bred subjects of the\
king of England," he observed in 1820. "During the thirty or forty\
years of their independence they have done absolutely nothing for the\
sciences, for the arts, for literature, or even for the statesmanlike\
studies of politics or political economy.... In the four quarters of the\
globe who reads an American book? Or goes to an American play? Or looks\
at an American picture or statue?" To put a sharp sting into his taunt\
he added, forgetting by whose authority slavery was introduced and\
fostered: "Under which of the old tyrannical governments of Europe is\
every sixth man a slave whom his fellow creatures may buy and sell?"\
\
Some Americans, while resenting the hasty and often superficial\
judgments of European writers, winced under their satire and took\
thought about certain particulars in the indictments brought against\
them. The mass of the people, however, bent on the great experiment,\
gave little heed to carping critics who saw the flaws and not the\
achievements of our country--critics who were in fact less interested in\
America than in preventing the rise and growth of democracy in Europe.\
\
\
=References=\
\
J.S. Bassett, _Life of Andrew Jackson_.\
\
J.W. Burgess, _The Middle Period_.\
\
H. Lodge, _Daniel Webster_.\
\
W. Macdonald, _Jacksonian Democracy_ (American Nation Series).\
\
Ostrogorski, _Democracy and the Organization of Political Parties_, Vol.\
II.\
\
C.H. Peck, _The Jacksonian Epoch_.\
\
C. Schurz, _Henry Clay_.\
\
\
=Questions=\
\
1. By what devices was democracy limited in the first days of our\
Republic?\
\
2. On what grounds were the limitations defended? Attacked?\
\
3. Outline the rise of political democracy in the United States.\
\
4. Describe three important changes in our political system.\
\
5. Contrast the Presidents of the old and the new generations.\
\
6. Account for the unpopularity of John Adams' administration.\
\
7. What had been the career of Andrew Jackson before 1829?\
\
8. Sketch the history of the protective tariff and explain the theory\
underlying it.\
\
9. Explain the growth of Southern opposition to the tariff.\
\
10. Relate the leading events connected with nullification in South\
Carolina.\
\
11. State Jackson's views and tell the outcome of the controversy.\
\
12. Why was Jackson opposed to the bank? How did he finally destroy it?\
\
13. The Whigs complained of Jackson's "executive tyranny." What did they\
mean?\
\
14. Give some of the leading events in Clay's career.\
\
15. How do you account for the triumph of Harrison in 1840?\
\
16. Why was Europe especially interested in America at this period? Who\
were some of the European writers on American affairs?\
\
\
=Research Topics=\
\
=Jackson's Criticisms of the Bank.=--Macdonald, _Documentary Source\
Book_, pp. 320-329.\
\
=Financial Aspects of the Bank Controversy.=--Dewey, _Financial History\
of the United States_, Sections 86-87; Elson, _History of the United\
States_, pp. 492-496.\
\
=Jackson's View of the Union.=--See his proclamation on nullification in\
Macdonald, pp. 333-340.\
\
=Nullification.=--McMaster, _History of the People of the United\
States_, Vol. VI, pp. 153-182; Elson, pp. 487-492.\
\
=The Webster-Hayne Debate.=--Analyze the arguments. Extensive extracts\
are given in Macdonald's larger three-volume work, _Select Documents of\
United States History, 1776-1761_, pp. 239-260.\
\
=The Character of Jackson's Administration.=--Woodrow Wilson, _History\
of the American People_, Vol. IV, pp. 1-87; Elson, pp. 498-501.\
\
=The People in 1830.=--From contemporary writings in Hart, _American\
History Told by Contemporaries_, Vol. III, pp. 509-530.\
\
=Biographical Studies.=--Andrew Jackson, J.Q. Adams, Henry Clay, Daniel\
Webster, J.C. Calhoun, and W.H. Harrison.\
\
\
\
\
CHAPTER XII\
\
THE MIDDLE BORDER AND THE GREAT WEST\
\
\
"We shall not send an emigrant beyond the Mississippi in a hundred\
years," exclaimed Livingston, the principal author of the Louisiana\
purchase. When he made this astounding declaration, he doubtless had\
before his mind's eye the great stretches of unoccupied lands between\
the Appalachians and the Mississippi. He also had before him the history\
of the English colonies, which told him of the two centuries required to\
settle the seaboard region. To practical men, his prophecy did not seem\
far wrong; but before the lapse of half that time there appeared beyond\
the Mississippi a tier of new states, reaching from the Gulf of Mexico\
to the southern boundary of Minnesota, and a new commonwealth on the\
Pacific Ocean where American emigrants had raised the Bear flag of\
California.\
\
\
THE ADVANCE OF THE MIDDLE BORDER\
\
=Missouri.=--When the middle of the nineteenth century had been reached,\
the Mississippi River, which Daniel Boone, the intrepid hunter, had\
crossed during Washington's administration "to escape from civilization"\
in Kentucky, had become the waterway for a vast empire. The center of\
population of the United States had passed to the Ohio Valley. Missouri,\
with its wide reaches of rich lands, low-lying, level, and fertile, well\
adapted to hemp raising, had drawn to its borders thousands of planters\
from the old Southern states--from Virginia and the Carolinas as well as\
from Kentucky and Tennessee. When the great compromise of 1820-21\
admitted her to the union, wearing "every jewel of sovereignty," as a\
florid orator announced, migratory slave owners were assured that their\
property would be safe in Missouri. Along the western shore of the\
Mississippi and on both banks of the Missouri to the uttermost limits of\
the state, plantations tilled by bondmen spread out in broad expanses.\
In the neighborhood of Jefferson City the slaves numbered more than a\
fourth of the population.\
\
Into this stream of migration from the planting South flowed another\
current of land-tilling farmers; some from Kentucky, Tennessee, and\
Mississippi, driven out by the onrush of the planters buying and\
consolidating small farms into vast estates; and still more from the\
East and the Old World. To the northwest over against Iowa and to the\
southwest against Arkansas, these yeomen laid out farms to be tilled by\
their own labor. In those regions the number of slaves seldom rose above\
five or six per cent of the population. The old French post, St. Louis,\
enriched by the fur trade of the Far West and the steamboat traffic of\
the river, grew into a thriving commercial city, including among its\
seventy-five thousand inhabitants in 1850 nearly forty thousand\
foreigners, German immigrants from Pennsylvania and Europe being the\
largest single element.\
\
=Arkansas.=--Below Missouri lay the territory of Arkansas, which had\
long been the paradise of the swarthy hunter and the restless\
frontiersman fleeing from the advancing borders of farm and town. In\
search of the life, wild and free, where the rifle supplied the game and\
a few acres of ground the corn and potatoes, they had filtered into the\
territory in an unending drift, "squatting" on the land. Without so much\
as asking the leave of any government, territorial or national, they\
claimed as their own the soil on which they first planted their feet.\
Like the Cherokee Indians, whom they had as neighbors, whose very\
customs and dress they sometimes adopted, the squatters spent their days\
in the midst of rough plenty, beset by chills, fevers, and the ills of\
the flesh, but for many years unvexed by political troubles or the\
restrictions of civilized life.\
\
Unfortunately for them, however, the fertile valleys of the Mississippi\
and Arkansas were well adapted to the cultivation of cotton and tobacco\
and their sylvan peace was soon broken by an invasion of planters. The\
newcomers, with their servile workers, spread upward in the valley\
toward Missouri and along the southern border westward to the Red River.\
In time the slaves in the tier of counties against Louisiana ranged from\
thirty to seventy per cent of the population. This marked the doom of\
the small farmer, swept Arkansas into the main current of planting\
politics, and led to a powerful lobby at Washington in favor of\
admission to the union, a boon granted in 1836.\
\
=Michigan.=--In accordance with a well-established custom, a free state\
was admitted to the union to balance a slave state. In 1833, the people\
of Michigan, a territory ten times the size of Connecticut, announced\
that the time had come for them to enjoy the privileges of a\
commonwealth. All along the southern border the land had been occupied\
largely by pioneers from New England, who built prim farmhouses and\
adopted the town-meeting plan of self-government after the fashion of\
the old home. The famous post of Detroit was growing into a flourishing\
city as the boats plying on the Great Lakes carried travelers, settlers,\
and freight through the narrows. In all, according to the census, there\
were more than ninety thousand inhabitants in the territory; so it was\
not without warrant that they clamored for statehood. Congress, busy as\
ever with politics, delayed; and the inhabitants of Michigan, unable to\
restrain their impatience, called a convention, drew up a constitution,\
and started a lively quarrel with Ohio over the southern boundary. The\
hand of Congress was now forced. Objections were made to the new\
constitution on the ground that it gave the ballot to all free white\
males, including aliens not yet naturalized; but the protests were\
overborne in a long debate. The boundary was fixed, and Michigan, though\
shorn of some of the land she claimed, came into the union in 1837.\
\
=Wisconsin.=--Across Lake Michigan to the west lay the territory of\
Wisconsin, which shared with Michigan the interesting history of the\
Northwest, running back into the heroic days when French hunters and\
missionaries were planning a French empire for the great monarch, Louis\
XIV. It will not be forgotten that the French rangers of the woods, the\
black-robed priests, prepared for sacrifice, even to death, the trappers\
of the French agencies, and the French explorers--Marquette, Joliet, and\
Menard--were the first white men to paddle their frail barks through the\
northern waters. They first blazed their trails into the black forests\
and left traces of their work in the names of portages and little\
villages. It was from these forests that Red Men in full war paint\
journeyed far to fight under the _fleur-de-lis_ of France when the\
soldiers of King Louis made their last stand at Quebec and Montreal\
against the imperial arms of Britain. It was here that the British flag\
was planted in 1761 and that the great Pontiac conspiracy was formed two\
years later to overthrow British dominion.\
\
When, a generation afterward, the Stars and Stripes supplanted the Union\
Jack, the French were still almost the only white men in the region.\
They were soon joined by hustling Yankee fur traders who did battle\
royal against British interlopers. The traders cut their way through\
forest trails and laid out the routes through lake and stream and over\
portages for the settlers and their families from the states "back\
East." It was the forest ranger who discovered the water power later\
used to turn the busy mills grinding the grain from the spreading farm\
lands. In the wake of the fur hunters, forest men, and farmers came\
miners from Kentucky, Tennessee, and Missouri crowding in to exploit the\
lead ores of the northwest, some of them bringing slaves to work their\
claims. Had it not been for the gold fever of 1849 that drew the\
wielders of pick and shovel to the Far West, Wisconsin would early have\
taken high rank among the mining regions of the country.\
\
From a favorable point of vantage on Lake Michigan, the village of\
Milwaukee, a center for lumber and grain transport and a place of entry\
for Eastern goods, grew into a thriving city. It claimed twenty thousand\
inhabitants, when in 1848 Congress admitted Wisconsin to the union.\
Already the Germans, Irish, and Scandinavians had found their way into\
the territory. They joined Americans from the older states in clearing\
forests, building roads, transforming trails into highways, erecting\
mills, and connecting streams with canals to make a network of routes\
for the traffic that poured to and from the Great Lakes.\
\
=Iowa and Minnesota.=--To the southwest of Wisconsin beyond the\
Mississippi, where the tall grass of the prairies waved like the sea,\
farmers from New England, New York, and Ohio had prepared Iowa for\
statehood. A tide of immigration that might have flowed into Missouri\
went northward; for freemen, unaccustomed to slavery and slave markets,\
preferred the open country above the compromise line. With incredible\
swiftness, they spread farms westward from the Mississippi. With Yankee\
ingenuity they turned to trading on the river, building before 1836\
three prosperous centers of traffic: Dubuque, Davenport, and Burlington.\
True to their old traditions, they founded colleges and academies that\
religion and learning might be cherished on the frontier as in the\
states from which they came. Prepared for self-government, the Iowans\
laid siege to the door of Congress and were admitted to the union in\
1846.\
\
Above Iowa, on the Mississippi, lay the territory of Minnesota--the home\
of the Dakotas, the Ojibways, and the Sioux. Like Michigan and\
Wisconsin, it had been explored early by the French scouts, and the\
first white settlement was the little French village of Mendota. To the\
people of the United States, the resources of the country were first\
revealed by the historic journey of Zebulon Pike in 1805 and by American\
fur traders who were quick to take advantage of the opportunity to ply\
their arts of hunting and bartering in fresh fields. In 1839 an\
American settlement was planted at Marina on the St. Croix, the outpost\
of advancing civilization. Within twenty years, the territory, boasting\
a population of 150,000, asked for admission to the union. In 1858 the\
plea was granted and Minnesota showed her gratitude three years later by\
being first among the states to offer troops to Lincoln in the hour of\
peril.\
\
\
ON TO THE PACIFIC--TEXAS AND THE MEXICAN WAR\
\
=The Uniformity of the Middle West.=--There was a certain monotony about\
pioneering in the Northwest and on the middle border. As the long\
stretches of land were cleared or prepared for the plow, they were laid\
out like checkerboards into squares of forty, eighty, one hundred sixty,\
or more acres, each the seat of a homestead. There was a striking\
uniformity also about the endless succession of fertile fields spreading\
far and wide under the hot summer sun. No majestic mountains relieved\
the sweep of the prairie. Few monuments of other races and antiquity\
were there to awaken curiosity about the region. No sonorous bells in\
old missions rang out the time of day. The chaffering Red Man bartering\
blankets and furs for powder and whisky had passed farther on. The\
population was made up of plain farmers and their families engaged in\
severe and unbroken labor, chopping down trees, draining fever-breeding\
swamps, breaking new ground, and planting from year to year the same\
rotation of crops. Nearly all the settlers were of native American stock\
into whose frugal and industrious lives the later Irish and German\
immigrants fitted, on the whole, with little friction. Even the Dutch\
oven fell before the cast-iron cooking stove. Happiness and sorrow,\
despair and hope were there, but all encompassed by the heavy tedium of\
prosaic sameness.\
\
[Illustration: SANTA BARBARA MISSION]\
\
=A Contrast in the Far West and Southwest.=--As George Rogers Clark and\
Daniel Boone had stirred the snug Americans of the seaboard to seek\
their fortunes beyond the Appalachians, so now Kit Carson, James Bowie,\
Sam Houston, Davy Crockett, and John C. Fremont were to lead the way\
into a new land, only a part of which was under the American flag. The\
setting for this new scene in the westward movement was thrown out in a\
wide sweep from the headwaters of the Mississippi to the banks of the\
Rio Grande; from the valleys of the Sabine and Red rivers to Montana and\
the Pacific slope. In comparison with the middle border, this region\
presented such startling diversities that only the eye of faith could\
foresee the unifying power of nationalism binding its communities with\
the older sections of the country. What contrasts indeed! The blue grass\
region of Kentucky or the rich, black soil of Illinois--the painted\
desert, the home of the sage brush and the coyote! The level prairies of\
Iowa--the mighty Rockies shouldering themselves high against the\
horizon! The long bleak winters of Wisconsin--California of endless\
summer! The log churches of Indiana or Illinois--the quaint missions of\
San Antonio, Tucson, and Santa Barbara! The little state of\
Delaware--the empire of Texas, one hundred and twenty times its area!\
And scattered about through the Southwest were signs of an ancient\
civilization--fragments of four-and five-story dwellings, ruined dams,\
aqueducts, and broken canals, which told of once prosperous peoples\
who, by art and science, had conquered the aridity of the desert and\
lifted themselves in the scale of culture above the savages of the\
plain.\
\
The settlers of this vast empire were to be as diverse in their origins\
and habits as those of the colonies on the coast had been. Americans of\
English, Irish, and Scotch-Irish descent came as usual from the Eastern\
states. To them were added the migratory Germans as well. Now for the\
first time came throngs of Scandinavians. Some were to make their homes\
on quiet farms as the border advanced against the setting sun. Others\
were to be Indian scouts, trappers, fur hunters, miners, cowboys, Texas\
planters, keepers of lonely posts on the plain and the desert, stage\
drivers, pilots of wagon trains, pony riders, fruit growers, "lumber\
jacks," and smelter workers. One common bond united them--a passion for\
the self-government accorded to states. As soon as a few thousand\
settlers came together in a single territory, there arose a mighty shout\
for a position beside the staid commonwealths of the East and the South.\
Statehood meant to the pioneers self-government, dignity, and the right\
to dispose of land, minerals, and timber in their own way. In the quest\
for this local autonomy there arose many a wordy contest in Congress,\
each of the political parties lending a helping hand in the admission of\
a state when it gave promise of adding new congressmen of the "right\
political persuasion," to use the current phrase.\
\
=Southern Planters and Texas.=--While the farmers of the North found the\
broad acres of the Western prairies stretching on before them apparently\
in endless expanse, it was far different with the Southern planters.\
Ever active in their search for new fields as they exhausted the virgin\
soil of the older states, the restless subjects of King Cotton quickly\
reached the frontier of Louisiana. There they paused; but only for a\
moment. The fertile land of Texas just across the boundary lured them on\
and the Mexican republic to which it belonged extended to them a more\
than generous welcome. Little realizing the perils lurking in a\
"peaceful penetration," the authorities at Mexico City opened wide the\
doors and made large grants of land to American contractors, who agreed\
to bring a number of families into Texas. The omnipresent Yankee, in the\
person of Moses Austin of Connecticut, hearing of this good news in the\
Southwest, obtained a grant in 1820 to settle three hundred Americans\
near Bexar--a commission finally carried out to the letter by his son\
and celebrated in the name given to the present capital of the state of\
Texas. Within a decade some twenty thousand Americans had crossed the\
border.\
\
=Mexico Closes the Door.=--The government of Mexico, unaccustomed to\
such enterprise and thoroughly frightened by its extent, drew back in\
dismay. Its fears were increased as quarrels broke out between the\
Americans and the natives in Texas. Fear grew into consternation when\
efforts were made by President Jackson to buy the territory for the\
United States. Mexico then sought to close the flood gates. It stopped\
all American colonization schemes, canceled many of the land grants, put\
a tariff on farming implements, and abolished slavery. These barriers\
were raised too late. A call for help ran through the western border of\
the United States. The sentinels of the frontier answered. Davy\
Crockett, the noted frontiersman, bear hunter, and backwoods politician;\
James Bowie, the dexterous wielder of the knife that to this day bears\
his name; and Sam Houston, warrior and pioneer, rushed to the aid of\
their countrymen in Texas. Unacquainted with the niceties of diplomacy,\
impatient at the formalities of international law, they soon made it\
known that in spite of Mexican sovereignty they would be their own\
masters.\
\
=The Independence of Texas Declared.=--Numbering only about one-fourth\
of the population in Texas, they raised the standard of revolt in 1836\
and summoned a convention. Following in the footsteps of their\
ancestors, they issued a declaration of independence signed mainly by\
Americans from the slave states. Anticipating that the government of\
Mexico would not quietly accept their word of defiance as final, they\
dispatched a force to repel "the invading army," as General Houston\
called the troops advancing under the command of Santa Ana, the Mexican\
president. A portion of the Texan soldiers took their stand in the\
Alamo, an old Spanish mission in the cottonwood trees in the town of San\
Antonio. Instead of obeying the order to blow up the mission and retire,\
they held their ground until they were completely surrounded and cut off\
from all help. Refusing to surrender, they fought to the bitter end, the\
last man falling a victim to the sword. Vengeance was swift. Within\
three months General Houston overwhelmed Santa Ana at the San Jacinto,\
taking him prisoner of war and putting an end to all hopes for the\
restoration of Mexican sovereignty over Texas.\
\
The Lone Star Republic, with Houston at the head, then sought admission\
to the United States. This seemed at first an easy matter. All that was\
required to bring it about appeared to be a treaty annexing Texas to the\
union. Moreover, President Jackson, at the height of his popularity, had\
a warm regard for General Houston and, with his usual sympathy for rough\
and ready ways of doing things, approved the transaction. Through an\
American representative in Mexico, Jackson had long and anxiously\
labored, by means none too nice, to wring from the Mexican republic the\
cession of the coveted territory. When the Texans took matters into\
their own hands, he was more than pleased; but he could not marshal the\
approval of two-thirds of the Senators required for a treaty of\
annexation. Cautious as well as impetuous, Jackson did not press the\
issue; he went out of office in 1837 with Texas uncertain as to her\
future.\
\
=Northern Opposition to Annexation.=--All through the North the\
opposition to annexation was clear and strong. Anti-slavery agitators\
could hardly find words savage enough to express their feelings.\
"Texas," exclaimed Channing in a letter to Clay, "is but the first step\
of aggression. I trust indeed that Providence will beat back and humble\
our cupidity and ambition. I now ask whether as a people we are\
prepared to seize on a neighboring territory for the end of extending\
slavery? I ask whether as a people we can stand forth in the sight of\
God, in the sight of nations, and adopt this atrocious policy? Sooner\
perish! Sooner be our name blotted out from the record of nations!"\
William Lloyd Garrison called for the secession of the Northern states\
if Texas was brought into the union with slavery. John Quincy Adams\
warned his countrymen that they were treading in the path of the\
imperialism that had brought the nations of antiquity to judgment and\
destruction. Henry Clay, the Whig candidate for President, taking into\
account changing public sentiment, blew hot and cold, losing the state\
of New York and the election of 1844 by giving a qualified approval of\
annexation. In the same campaign, the Democrats boldly demanded the\
"Reannexation of Texas," based on claims which the United States once\
had to Spanish territory beyond the Sabine River.\
\
=Annexation.=--The politicians were disposed to walk very warily. Van\
Buren, at heart opposed to slavery extension, refused to press the issue\
of annexation. Tyler, a pro-slavery Democrat from Virginia, by a strange\
fling of fortune carried into office as a nominal Whig, kept his mind\
firmly fixed on the idea of reelection and let the troublesome matter\
rest until the end of his administration was in sight. He then listened\
with favor to the voice of the South. Calhoun stated what seemed to be a\
convincing argument: All good Americans have their hearts set on the\
Constitution; the admission of Texas is absolutely essential to the\
preservation of the union; it will give a balance of power to the South\
as against the North growing with incredible swiftness in wealth and\
population. Tyler, impressed by the plea, appointed Calhoun to the\
office of Secretary of State in 1844, authorizing him to negotiate the\
treaty of annexation--a commission at once executed. This scheme was\
blocked in the Senate where the necessary two-thirds vote could not be\
secured. Balked but not defeated, the advocates of annexation drew up a\
joint resolution which required only a majority vote in both houses,\
and in February of the next year, just before Tyler gave way to Polk,\
they pushed it through Congress. So Texas, amid the groans of Boston and\
the hurrahs of Charleston, folded up her flag and came into the union.\
\
[Illustration: TEXAS AND THE TERRITORY IN DISPUTE]\
\
=The Mexican War.=--The inevitable war with Mexico, foretold by the\
abolitionists and feared by Henry Clay, ensued, the ostensible cause\
being a dispute over the boundaries of the new state. The Texans claimed\
all the lands down to the Rio Grande. The Mexicans placed the border of\
Texas at the Nueces River and a line drawn thence in a northerly\
direction. President Polk, accepting the Texan view of the controversy,\
ordered General Zachary Taylor to move beyond the Nueces in defense of\
American sovereignty. This act of power, deemed by the Mexicans an\
invasion of their territory, was followed by an attack on our troops.\
\
President Polk, not displeased with the turn of events, announced that\
American blood had been "spilled on American soil" and that war existed\
"by the act of Mexico." Congress, in a burst of patriotic fervor,\
brushed aside the protests of those who deplored the conduct of the\
government as wanton aggression on a weaker nation and granted money and\
supplies to prosecute the war. The few Whigs in the House of\
Representatives, who refused to vote in favor of taking up arms,\
accepted the inevitable with such good grace as they could command. All\
through the South and the West the war was popular. New England\
grumbled, but gave loyal, if not enthusiastic, support to a conflict\
precipitated by policies not of its own choosing. Only a handful of firm\
objectors held out. James Russell Lowell, in his _Biglow Papers_, flung\
scorn and sarcasm to the bitter end.\
\
=The Outcome of the War.=--The foregone conclusion was soon reached.\
General Taylor might have delivered the fatal thrust from northern\
Mexico if politics had not intervened. Polk, anxious to avoid raising up\
another military hero for the Whigs to nominate for President, decided\
to divide the honors by sending General Scott to strike a blow at the\
capital, Mexico City. The deed was done with speed and pomp and two\
heroes were lifted into presidential possibilities. In the Far West a\
third candidate was made, John C. Fremont, who, in cooperation with\
Commodores Sloat and Stockton and General Kearney, planted the Stars and\
Stripes on the Pacific slope.\
\
In February, 1848, the Mexicans came to terms, ceding to the victor\
California, Arizona, New Mexico, and more--a domain greater in extent\
than the combined areas of France and Germany. As a salve to the wound,\
the vanquished received fifteen million dollars in cash and the\
cancellation of many claims held by American citizens. Five years later,\
through the negotiations of James Gadsden, a further cession of lands\
along the southern border of Arizona and New Mexico was secured on\
payment of ten million dollars.\
\
=General Taylor Elected President.=--The ink was hardly dry upon the\
treaty that closed the war before "rough and ready" General Taylor, a\
slave owner from Louisiana, "a Whig," as he said, "but not an ultra\
Whig," was put forward as the Whig candidate for President. He himself\
had not voted for years and he was fairly innocent in matters political.\
The tariff, the currency, and internal improvements, with a magnificent\
gesture he referred to the people's representatives in Congress,\
offering to enforce the laws as made, if elected. Clay's followers\
mourned. Polk stormed but could not win even a renomination at the hands\
of the Democrats. So it came about that the hero of Buena Vista,\
celebrated for his laconic order, "Give 'em a little more grape, Captain\
Bragg," became President of the United States.\
\
\
THE PACIFIC COAST AND UTAH\
\
=Oregon.=--Closely associated in the popular mind with the contest about\
the affairs of Texas was a dispute with Great Britain over the\
possession of territory in Oregon. In their presidential campaign of\
1844, the Democrats had coupled with the slogan, "The Reannexation of\
Texas," two other cries, "The Reoccupation of Oregon," and "Fifty-four\
Forty or Fight." The last two slogans were founded on American\
discoveries and explorations in the Far Northwest. Their appearance in\
politics showed that the distant Oregon country, larger in area than New\
England, New York, and Pennsylvania combined, was at last receiving from\
the nation the attention which its importance warranted.\
\
_Joint Occupation and Settlement._--Both England and the United States\
had long laid claim to Oregon and in 1818 they had agreed to occupy the\
territory jointly--a contract which was renewed ten years later for an\
indefinite period. Under this plan, citizens of both countries were free\
to hunt and settle anywhere in the region. The vanguard of British fur\
traders and Canadian priests was enlarged by many new recruits, with\
Americans not far behind them. John Jacob Astor, the resourceful New\
York merchant, sent out trappers and hunters who established a trading\
post at Astoria in 1811. Some twenty years later, American\
missionaries--among them two very remarkable men, Jason Lee and Marcus\
Whitman--were preaching the gospel to the Indians.\
\
Through news from the fur traders and missionaries, Eastern farmers\
heard of the fertile lands awaiting their plows on the Pacific slope;\
those with the pioneering spirit made ready to take possession of the\
new country. In 1839 a band went around by Cape Horn. Four years later a\
great expedition went overland. The way once broken, others followed\
rapidly. As soon as a few settlements were well established, the\
pioneers held a mass meeting and agreed upon a plan of government. "We,\
the people of Oregon territory," runs the preamble to their compact,\
"for the purposes of mutual protection and to secure peace and\
prosperity among ourselves, agree to adopt the following laws and\
regulations until such time as the United States of America extend their\
jurisdiction over us." Thus self-government made its way across the\
Rocky Mountains.\
\
[Illustration: THE OREGON COUNTRY AND THE DISPUTED BOUNDARY]\
\
_The Boundary Dispute with England Adjusted._--By this time it was\
evident that the boundaries of Oregon must be fixed. Having made the\
question an issue in his campaign, Polk, after his election in 1844,\
pressed it upon the attention of the country. In his inaugural address\
and his first message to Congress he reiterated the claim of the\
Democratic platform that "our title to the whole territory of Oregon is\
clear and unquestionable." This pretension Great Britain firmly\
rejected, leaving the President a choice between war and compromise.\
\
Polk, already having the contest with Mexico on his hands, sought and\
obtained a compromise. The British government, moved by a hint from the\
American minister, offered a settlement which would fix the boundary at\
the forty-ninth parallel instead of "fifty-four forty," and give it\
Vancouver Island. Polk speedily chose this way out of the dilemma.\
Instead of making the decision himself, however, and drawing up a\
treaty, he turned to the Senate for "counsel." As prearranged with party\
leaders, the advice was favorable to the plan. The treaty, duly drawn in\
1846, was ratified by the Senate after an acrimonious debate. "Oh!\
mountain that was delivered of a mouse," exclaimed Senator Benton, "thy\
name shall be fifty-four forty!" Thirteen years later, the southern part\
of the territory was admitted to the union as the state of Oregon,\
leaving the northern and eastern sections in the status of a territory.\
\
=California.=--With the growth of the northwestern empire, dedicated by\
nature to freedom, the planting interests might have been content, had\
fortune not wrested from them the fair country of California. Upon this\
huge territory they had set their hearts. The mild climate and fertile\
soil seemed well suited to slavery and the planters expected to extend\
their sway to the entire domain. California was a state of more than\
155,000 square miles--about seventy times the size of the state of\
Delaware. It could readily be divided into five or six large states, if\
that became necessary to preserve the Southern balance of power.\
\
_Early American Relations with California._--Time and tide, it seems,\
were not on the side of the planters. Already Americans of a far\
different type were invading the Pacific slope. Long before Polk ever\
dreamed of California, the Yankee with his cargo of notions had been\
around the Horn. Daring skippers had sailed out of New England harbors\
with a variety of goods, bent their course around South America to\
California, on to China and around the world, trading as they went and\
leaving pots, pans, woolen cloth, guns, boots, shoes, salt fish, naval\
stores, and rum in their wake. "Home from Californy!" rang the cry in\
many a New England port as a good captain let go his anchor on his\
return from the long trading voyage in the Pacific.\
\
[Illustration: THE OVERLAND TRAILS]\
\
_The Overland Trails._--Not to be outdone by the mariners of the deep,\
western scouts searched for overland routes to the Pacific. Zebulon\
Pike, explorer and pathfinder, by his expedition into the Southwest\
during Jefferson's administration, had discovered the resources of New\
Spain and had shown his countrymen how easy it was to reach Santa Fe\
from the upper waters of the Arkansas River. Not long afterward, traders\
laid open the route, making Franklin, Missouri, and later Fort\
Leavenworth the starting point. Along the trail, once surveyed, poured\
caravans heavily guarded by armed men against marauding Indians. Sand\
storms often wiped out all signs of the route; hunger and thirst did\
many a band of wagoners to death; but the lure of the game and the\
profits at the end kept the business thriving. Huge stocks of cottons,\
glass, hardware, and ammunition were drawn almost across the continent\
to be exchanged at Santa Fe for furs, Indian blankets, silver, and\
mules; and many a fortune was made out of the traffic.\
\
_Americans in California._--Why stop at Santa Fe? The question did not\
long remain unanswered. In 1829, Ewing Young broke the path to Los\
Angeles. Thirteen years later Fremont made the first of his celebrated\
expeditions across plain, desert, and mountain, arousing the interest of\
the entire country in the Far West. In the wake of the pathfinders went\
adventurers, settlers, and artisans. By 1847, more than one-fifth of the\
inhabitants in the little post of two thousand on San Francisco Bay were\
from the United States. The Mexican War, therefore, was not the\
beginning but the end of the American conquest of California--a conquest\
initiated by Americans who went to till the soil, to trade, or to follow\
some mechanical pursuit.\
\
_The Discovery of Gold._--As if to clinch the hold on California already\
secured by the friends of free soil, there came in 1848 the sudden\
discovery of gold at Sutter's Mill in the Sacramento Valley. When this\
exciting news reached the East, a mighty rush began to California, over\
the trails, across the Isthmus of Panama, and around Cape Horn. Before\
two years had passed, it is estimated that a hundred thousand people, in\
search of fortunes, had arrived in California--mechanics, teachers,\
doctors, lawyers, farmers, miners, and laborers from the four corners of\
the earth.\
\
[Illustration: _From an old print_\
\
SAN FRANCISCO IN 1849]\
\
_California a Free State._--With this increase in population there\
naturally resulted the usual demand for admission to the union. Instead\
of waiting for authority from Washington, the Californians held a\
convention in 1849 and framed their constitution. With impatience, the\
delegates brushed aside the plea that "the balance of power between the\
North and South" required the admission of their state as a slave\
commonwealth. Without a dissenting voice, they voted in favor of freedom\
and boldly made their request for inclusion among the United States.\
President Taylor, though a Southern man, advised Congress to admit the\
applicant. Robert Toombs of Georgia vowed to God that he preferred\
secession. Henry Clay, the great compromiser, came to the rescue and in\
1850 California was admitted as a free state.\
\
=Utah.=--On the long road to California, in the midst of forbidding and\
barren wastes, a religious sect, the Mormons, had planted a colony\
destined to a stormy career. Founded in 1830 under the leadership of\
Joseph Smith of New York, the sect had suffered from many cruel buffets\
of fortune. From Ohio they had migrated into Missouri where they were\
set upon and beaten. Some of them were murdered by indignant neighbors.\
Harried out of Missouri, they went into Illinois only to see their\
director and prophet, Smith, first imprisoned by the authorities and\
then shot by a mob. Having raised up a cloud of enemies on account of\
both their religious faith and their practice of allowing a man to have\
more than one wife, they fell in heartily with the suggestion of a new\
leader, Brigham Young, that they go into the Far West beyond the plains\
of Kansas--into the forlorn desert where the wicked would cease from\
troubling and the weary could be at rest, as they read in the Bible. In\
1847, Young, with a company of picked men, searched far and wide until\
he found a suitable spot overlooking the Salt Lake Valley. Returning to\
Illinois, he gathered up his followers, now numbering several thousand,\
and in one mighty wagon caravan they all went to their distant haven.\
\
_Brigham Young and His Economic System._--In Brigham Young the Mormons\
had a leader of remarkable power who gave direction to the redemption of\
the arid soil, the management of property, and the upbuilding of\
industry. He promised them to make the desert blossom as the rose, and\
verily he did it. He firmly shaped the enterprise of the colony along\
co-operative lines, holding down the speculator and profiteer with one\
hand and giving encouragement to the industrious poor with the other.\
With the shrewdness befitting a good business man, he knew how to draw\
the line between public and private interest. Land was given outright to\
each family, but great care was exercised in the distribution so that\
none should have great advantage over another. The purchase of supplies\
and the sale of produce were carried on through a cooperative store, the\
profits of which went to the common good. Encountering for the first\
time in the history of the Anglo-Saxon race the problem of aridity, the\
Mormons surmounted the most perplexing obstacles with astounding skill.\
They built irrigation works by cooperative labor and granted water\
rights to all families on equitable terms.\
\
_The Growth of Industries._--Though farming long remained the major\
interest of the colony, the Mormons, eager to be self-supporting in\
every possible way, bent their efforts also to manufacturing and later\
to mining. Their missionaries, who hunted in the highways and byways of\
Europe for converts, never failed to stress the economic advantages of\
the sect. "We want," proclaimed President Young to all the earth, "a\
company of woolen manufacturers to come with machinery and take the wool\
from the sheep and convert it into the best clothes. We want a company\
of potters; we need them; the clay is ready and the dishes wanted.... We\
want some men to start a furnace forthwith; the iron, coal, and molders\
are waiting.... We have a printing press and any one who can take good\
printing and writing paper to the Valley will be a blessing to\
themselves and the church." Roads and bridges were built; millions were\
spent in experiments in agriculture and manufacturing; missionaries at a\
huge cost were maintained in the East and in Europe; an army was kept\
for defense against the Indians; and colonies were planted in the\
outlying regions. A historian of Deseret, as the colony was called by\
the Mormons, estimated in 1895 that by the labor of their hands the\
people had produced nearly half a billion dollars in wealth since the\
coming of the vanguard.\
\
_Polygamy Forbidden._--The hope of the Mormons that they might forever\
remain undisturbed by outsiders was soon dashed to earth, for hundreds\
of farmers and artisans belonging to other religious sects came to\
settle among them. In 1850 the colony was so populous and prosperous\
that it was organized into a territory of the United States and brought\
under the supervision of the federal government. Protests against\
polygamy were raised in the colony and at the seat of authority three\
thousand miles away at Washington. The new Republican party in 1856\
proclaimed it "the right and duty of Congress to prohibit in the\
Territories those twin relics of barbarism, polygamy and slavery." In\
due time the Mormons had to give up their marriage practices which were\
condemned by the common opinion of all western civilization; but they\
kept their religious faith. Monuments to their early enterprise are seen\
in the Temple and the Tabernacle, the irrigation works, and the great\
wealth of the Church.\
\
\
SUMMARY OF WESTERN DEVELOPMENT AND NATIONAL POLITICS\
\
While the statesmen of the old generation were solving the problems of\
their age, hunters, pioneers, and home seekers were preparing new\
problems beyond the Alleghanies. The West was rising in population and\
wealth. Between 1783 and 1829, eleven states were added to the original\
thirteen. All but two were in the West. Two of them were in the\
Louisiana territory beyond the Mississippi. Here the process of\
colonization was repeated. Hardy frontier people cut down the forests,\
built log cabins, laid out farms, and cut roads through the wilderness.\
They began a new civilization just as the immigrants to Virginia or\
Massachusetts had done two centuries earlier.\
\
Like the seaboard colonists before them, they too cherished the spirit\
of independence and power. They had not gone far upon their course\
before they resented the monopoly of the presidency by the East. In 1829\
they actually sent one of their own cherished leaders, Andrew Jackson,\
to the White House. Again in 1840, in 1844, in 1848, and in 1860, the\
Mississippi Valley could boast that one of its sons had been chosen for\
the seat of power at Washington. Its democratic temper evoked a cordial\
response in the towns of the East where the old aristocracy had been put\
aside and artisans had been given the ballot.\
\
For three decades the West occupied the interest of the nation. Under\
Jackson's leadership, it destroyed the second United States Bank. When\
he smote nullification in South Carolina, it gave him cordial support.\
It approved his policy of parceling out government offices among party\
workers--"the spoils system" in all its fullness. On only one point did\
it really dissent. The West heartily favored internal improvements, the\
appropriation of federal funds for highways, canals, and railways.\
Jackson had misgivings on this question and awakened sharp criticism by\
vetoing a road improvement bill.\
\
From their point of vantage on the frontier, the pioneers pressed on\
westward. They pushed into Texas, created a state, declared their\
independence, demanded a place in the union, and precipitated a war with\
Mexico. They crossed the trackless plain and desert, laying out trails\
to Santa Fe, to Oregon, and to California. They were upon the scene when\
the Mexican War brought California under the Stars and Stripes. They had\
laid out their farms in the Willamette Valley when the slogan\
"Fifty-Four Forty or Fight" forced a settlement of the Oregon boundary.\
California and Oregon were already in the union when there arose the\
Great Civil War testing whether this nation or any nation so conceived\
and so dedicated could long endure.\
\
\
=References=\
\
G.P. Brown, _Westward Expansion_ (American Nation Series).\
\
\
K. Coman, _Economic Beginnings of the Far West_ (2 vols.).\
\
F. Parkman, _California and the Oregon Trail_.\
\
R.S. Ripley, _The War with Mexico_.\
\
W.C. Rives, _The United States and Mexico, 1821-48_ (2 vols.).\
\
\
=Questions=\
\
1. Give some of the special features in the history of Missouri,\
Arkansas, Michigan, Wisconsin, Iowa, and Minnesota.\
\
2. Contrast the climate and soil of the Middle West and the Far West.\
\
3. How did Mexico at first encourage American immigration?\
\
4. What produced the revolution in Texas? Who led in it?\
\
5. Narrate some of the leading events in the struggle over annexation to\
the United States.\
\
6. What action by President Polk precipitated war?\
\
7. Give the details of the peace settlement with Mexico.\
\
8. What is meant by the "joint occupation" of Oregon?\
\
9. How was the Oregon boundary dispute finally settled?\
\
10. Compare the American "invasion" of California with the migration\
into Texas.\
\
11. Explain how California became a free state.\
\
12. Describe the early economic policy of the Mormons.\
\
\
=Research Topics=\
\
=The Independence of Texas.=--McMaster, _History of the People of the\
United States_, Vol. VI, pp. 251-270. Woodrow Wilson, _History of the\
American People_, Vol. IV, pp. 102-126.\
\
=The Annexation of Texas.=--McMaster, Vol. VII. The passages on\
annexation are scattered through this volume and it is an exercise in\
ingenuity to make a connected story of them. Source materials in Hart,\
_American History Told by Contemporaries_, Vol. III, pp. 637-655; Elson,\
_History of the United States_, pp. 516-521, 526-527.\
\
=The War with Mexico.=--Elson, pp. 526-538.\
\
=The Oregon Boundary Dispute.=--Schafer, _History of the Pacific\
Northwest_ (rev. ed.), pp. 88-104; 173-185.\
\
=The Migration to Oregon.=--Schafer, pp. 105-172. Coman, _Economic\
Beginnings of the Far West_, Vol. II, pp. 113-166.\
\
=The Santa Fe Trail.=--Coman, _Economic Beginnings_, Vol. II, pp. 75-93.\
\
=The Conquest of California.=--Coman, Vol. II, pp. 297-319.\
\
=Gold in California.=--McMaster, Vol. VII, pp. 585-614.\
\
=The Mormon Migration.=--Coman, Vol. II, pp. 167-206.\
\
=Biographical Studies.=--Fremont, Generals Scott and Taylor, Sam\
Houston, and David Crockett.\
\
=The Romance of Western Exploration.=--J.G. Neihardt, _The Splendid\
Wayfaring_. J.G. Neihardt, _The Song of Hugh Glass_.\
\
\
\
\
PART V. SECTIONAL CONFLICT AND RECONSTRUCTION\
\
\
\
\
CHAPTER XIII\
\
THE RISE OF THE INDUSTRIAL SYSTEM\
\
\
If Jefferson could have lived to see the Stars and Stripes planted on\
the Pacific Coast, the broad empire of Texas added to the planting\
states, and the valley of the Willamette waving with wheat sown by\
farmers from New England, he would have been more than fortified in his\
faith that the future of America lay in agriculture. Even a stanch old\
Federalist like Gouverneur Morris or Josiah Quincy would have mournfully\
conceded both the prophecy and the claim. Manifest destiny never seemed\
more clearly written in the stars.\
\
As the farmers from the Northwest and planters from the Southwest poured\
in upon the floor of Congress, the party of Jefferson, christened anew\
by Jackson, grew stronger year by year. Opponents there were, no doubt,\
disgruntled critics and Whigs by conviction; but in 1852 Franklin\
Pierce, the Democratic candidate for President, carried every state in\
the union except Massachusetts, Vermont, Kentucky, and Tennessee. This\
victory, a triumph under ordinary circumstances, was all the more\
significant in that Pierce was pitted against a hero of the Mexican War,\
General Scott, whom the Whigs, hoping to win by rousing the martial\
ardor of the voters, had nominated. On looking at the election returns,\
the new President calmly assured the planters that "the general\
principle of reduction of duties with a view to revenue may now be\
regarded as the settled policy of the country." With equal confidence,\
he waved aside those agitators who devoted themselves "to the supposed\
interests of the relatively few Africans in the United States." Like a\
watchman in the night he called to the country: "All's well."\
\
The party of Hamilton and Clay lay in the dust.\
\
\
THE INDUSTRIAL REVOLUTION\
\
As pride often goeth before a fall, so sanguine expectation is sometimes\
the symbol of defeat. Jackson destroyed the bank. Polk signed the tariff\
bill of 1846 striking an effective blow at the principle of protection\
for manufactures. Pierce promised to silence the abolitionists. His\
successor was to approve a drastic step in the direction of free trade.\
Nevertheless all these things left untouched the springs of power that\
were in due time to make America the greatest industrial nation on the\
earth; namely, vast national resources, business enterprise, inventive\
genius, and the free labor supply of Europe. Unseen by the thoughtless,\
unrecorded in the diaries of wiseacres, rarely mentioned in the speeches\
of statesmen, there was swiftly rising such a tide in the affairs of\
America as Jefferson and Hamilton never dreamed of in their little\
philosophies.\
\
=The Inventors.=--Watt and Boulton experimenting with steam in England,\
Whitney combining wood and steel into a cotton gin, Fulton and Fitch\
applying the steam engine to navigation, Stevens and Peter Cooper trying\
out the "iron horse" on "iron highways," Slater building spinning mills\
in Pawtucket, Howe attaching the needle to the flying wheel, Morse\
spanning a continent with the telegraph, Cyrus Field linking the markets\
of the new world with the old along the bed of the Atlantic, McCormick\
breaking the sickle under the reaper--these men and a thousand more were\
destroying in a mighty revolution of industry the world of the\
stagecoach and the tallow candle which Washington and Franklin had\
inherited little changed from the age of Caesar. Whitney was to make\
cotton king. Watt and Fulton were to make steel and steam masters of the\
world. Agriculture was to fall behind in the race for supremacy.\
\
=Industry Outstrips Planting.=--The story of invention, that tribute to\
the triumph of mind over matter, fascinating as a romance, need not be\
treated in detail here. The effects of invention on social and political\
life, multitudinous and never-ending, form the very warp and woof of\
American progress from the days of Andrew Jackson to the latest hour.\
Neither the great civil conflict--the clash of two systems--nor the\
problems of the modern age can be approached without an understanding of\
the striking phases of industrialism.\
\
[Illustration: A NEW ENGLAND MILL BUILT IN 1793]\
\
First and foremost among them was the uprush of mills managed by\
captains of industry and manned by labor drawn from farms, cities, and\
foreign lands. For every planter who cleared a domain in the Southwest\
and gathered his army of bondmen about him, there rose in the North a\
magician of steam and steel who collected under his roof an army of free\
workers.\
\
In seven league boots this new giant strode ahead of the Southern giant.\
Between 1850 and 1859, to use dollars and cents as the measure of\
progress, the value of domestic manufactures including mines and\
fisheries rose from $1,019,106,616 to $1,900,000,000, an increase of\
eighty-six per cent in ten years. In this same period the total\
production of naval stores, rice, sugar, tobacco, and cotton, the\
staples of the South, went only from $165,000,000, in round figures, to\
$204,000,000. At the halfway point of the century, the capital invested\
in industry, commerce, and cities far exceeded the value of all the farm\
land between the Atlantic and the Pacific; thus the course of economy\
had been reversed in fifty years. Tested by figures of production, King\
Cotton had shriveled by 1860 to a petty prince in comparison, for each\
year the captains of industry turned out goods worth nearly twenty times\
all the bales of cotton picked on Southern plantations. Iron, boots and\
shoes, and leather goods pouring from Northern mills surpassed in value\
the entire cotton output.\
\
=The Agrarian West Turns to Industry.=--Nor was this vast enterprise\
confined to the old Northeast where, as Madison had sagely remarked,\
commerce was early dominant. "Cincinnati," runs an official report in\
1854, "appears to be a great central depot for ready-made clothing and\
its manufacture for the Western markets may be said to be one of the\
great trades of that city." There, wrote another traveler, "I heard the\
crack of the cattle driver's whip and the hum of the factory: the West\
and the East meeting." Louisville and St. Louis were already famous for\
their clothing trades and the manufacture of cotton bagging. Five\
hundred of the two thousand woolen mills in the country in 1860 were in\
the Western states. Of the output of flour and grist mills, which almost\
reached in value the cotton crop of 1850, the Ohio Valley furnished a\
rapidly growing share. The old home of Jacksonian democracy, where\
Federalists had been almost as scarce as monarchists, turned slowly\
backward, as the needle to the pole, toward the principle of protection\
for domestic industry, espoused by Hamilton and defended by Clay.\
\
=The Extension of Canals and Railways.=--As necessary to mechanical\
industry as steel and steam power was the great market, spread over a\
wide and diversified area and knit together by efficient means of\
transportation. This service was supplied to industry by the steamship,\
which began its career on the Hudson in 1807; by the canals, of which\
the Erie opened in 1825 was the most noteworthy; and by the railways,\
which came into practical operation about 1830.\
\
[Illustration: _From an old print_\
\
AN EARLY RAILWAY]\
\
With sure instinct the Eastern manufacturer reached out for the markets\
of the Northwest territory where free farmers were producing annually\
staggering crops of corn, wheat, bacon, and wool. The two great canal\
systems--the Erie connecting New York City with the waterways of the\
Great Lakes and the Pennsylvania chain linking Philadelphia with the\
headwaters of the Ohio--gradually turned the tide of trade from New\
Orleans to the Eastern seaboard. The railways followed the same paths.\
By 1860, New York had rail connections with Chicago and St. Louis, one\
of the routes running through the Hudson and Mohawk valleys and along\
the Great Lakes, the other through Philadelphia and Pennsylvania and\
across the rich wheat fields of Ohio, Indiana, and Illinois. Baltimore,\
not to be outdone by her two rivals, reached out over the mountains for\
the Western trade and in 1857 had trains running into St. Louis.\
\
In railway enterprise the South took more interest than in canals, and\
the friends of that section came to its aid. To offset the magnet\
drawing trade away from the Mississippi Valley, lines were built from\
the Gulf to Chicago, the Illinois Central part of the project being a\
monument to the zeal and industry of a Democrat, better known in\
politics than in business, Stephen A. Douglas. The swift movement of\
cotton and tobacco to the North or to seaports was of common concern to\
planters and manufacturers. Accordingly lines were flung down along the\
Southern coast, linking Richmond, Charleston, and Savannah with the\
Northern markets. Other lines struck inland from the coast, giving a\
rail outlet to the sea for Raleigh, Columbia, Atlanta, Chattanooga,\
Nashville, and Montgomery. Nevertheless, in spite of this enterprise,\
the mileage of all the Southern states in 1860 did not equal that of\
Ohio, Indiana, and Illinois combined.\
\
=Banking and Finance.=--Out of commerce and manufactures and the\
construction and operation of railways came such an accumulation of\
capital in the Northern states as merchants of old never imagined. The\
banks of the four industrial states of Massachusetts, Connecticut, New\
York, and Pennsylvania in 1860 had funds greater than the banks in all\
the other states combined. New York City had become the money market of\
America, the center to which industrial companies, railway promoters,\
farmers, and planters turned for capital to initiate and carry on their\
operations. The banks of Louisiana, South Carolina, Georgia, and\
Virginia, it is true, had capital far in excess of the banks of the\
Northwest; but still they were relatively small compared with the\
financial institutions of the East.\
\
=The Growth of the Industrial Population.=--A revolution of such\
magnitude in industry, transport, and finance, overturning as it did the\
agrarian civilization of the old Northwest and reaching out to the very\
borders of the country, could not fail to bring in its train\
consequences of a striking character. Some were immediate and obvious.\
Others require a fullness of time not yet reached to reveal their\
complete significance. Outstanding among them was the growth of an\
industrial population, detached from the land, concentrated in cities,\
and, to use Jefferson's phrase, dependent upon "the caprices and\
casualties of trade" for a livelihood. This was a result, as the great\
Virginian had foreseen, which flowed inevitably from public and private\
efforts to stimulate industry as against agriculture.\
\
[Illustration: LOWELL, MASSACHUSETTS, IN 1838, AN EARLY INDUSTRIAL\
TOWN]\
\
It was estimated in 1860, on the basis of the census figures, that\
mechanical production gave employment to 1,100,000 men and 285,000\
women, making, if the average number of dependents upon them be\
reckoned, nearly six million people or about one-sixth of the population\
of the country sustained from manufactures. "This," runs the official\
record, "was exclusive of the number engaged in the production of many\
of the raw materials and of the food for manufacturers; in the\
distribution of their products, such as merchants, clerks, draymen,\
mariners, the employees of railroads, expresses, and steamboats; of\
capitalists, various artistic and professional classes, as well as\
carpenters, bricklayers, painters, and the members of other mechanical\
trades not classed as manufactures. It is safe to assume, then, that\
one-third of the whole population is supported, directly, or indirectly,\
by manufacturing industry." Taking, however, the number of persons\
directly supported by manufactures, namely about six millions, reveals\
the astounding fact that the white laboring population, divorced from\
the soil, already exceeded the number of slaves on Southern farms and\
plantations.\
\
_Immigration._--The more carefully the rapid growth of the industrial\
population is examined, the more surprising is the fact that such an\
immense body of free laborers could be found, particularly when it is\
recalled to what desperate straits the colonial leaders were put in\
securing immigrants,--slavery, indentured servitude, and kidnapping\
being the fruits of their necessities. The answer to the enigma is to be\
found partly in European conditions and partly in the cheapness of\
transportation after the opening of the era of steam navigation. Shrewd\
observers of the course of events had long foreseen that a flood of\
cheap labor was bound to come when the way was made easy. Some, among\
them Chief Justice Ellsworth, went so far as to prophesy that white\
labor would in time be so abundant that slavery would disappear as the\
more costly of the two labor systems. The processes of nature were aided\
by the policies of government in England and Germany.\
\
_The Coming of the Irish._--The opposition of the Irish people to the\
English government, ever furious and irrepressible, was increased in the\
mid forties by an almost total failure of the potato crop, the main\
support of the peasants. Catholic in religion, they had been compelled\
to support a Protestant church. Tillers of the soil by necessity, they\
were forced to pay enormous tributes to absentee landlords in England\
whose claim to their estates rested upon the title of conquest and\
confiscation. Intensely loyal to their race, the Irish were subjected in\
all things to the Parliament at London, in which their small minority of\
representatives had little influence save in holding a balance of power\
between the two contending English parties. To the constant political\
irritation, the potato famine added physical distress beyond\
description. In cottages and fields and along the highways the victims\
of starvation lay dead by the hundreds, the relief which charity\
afforded only bringing misery more sharply to the foreground. Those who\
were fortunate enough to secure passage money sought escape to America.\
In 1844 the total immigration into the United States was less than\
eighty thousand; in 1850 it had risen by leaps and bounds to more than\
three hundred thousand. Between 1820 and 1860 the immigrants from the\
United Kingdom numbered 2,750,000, of whom more than one-half were\
Irish. It has been said with a touch of exaggeration that the American\
canals and railways of those days were built by the labor of Irishmen.\
\
_The German Migration._--To political discontent and economic distress,\
such as was responsible for the coming of the Irish, may likewise be\
traced the source of the Germanic migration. The potato blight that fell\
upon Ireland visited the Rhine Valley and Southern Germany at the same\
time with results as pitiful, if less extensive. The calamity inflicted\
by nature was followed shortly by another inflicted by the despotic\
conduct of German kings and princes. In 1848 there had occurred\
throughout Europe a popular uprising in behalf of republics and\
democratic government. For a time it rode on a full tide of success.\
Kings were overthrown, or compelled to promise constitutional\
government, and tyrannical ministers fled from their palaces. Then came\
reaction. Those who had championed the popular cause were imprisoned,\
shot, or driven out of the land. Men of attainments and distinction,\
whose sole offense was opposition to the government of kings and\
princes, sought an asylum in America, carrying with them to the land of\
their adoption the spirit of liberty and democracy. In 1847 over fifty\
thousand Germans came to America, the forerunners of a migration that\
increased, almost steadily, for many years. The record of 1860 showed\
that in the previous twenty years nearly a million and a half had found\
homes in the United States. Far and wide they scattered, from the mills\
and shops of the seacoast towns to the uttermost frontiers of Wisconsin\
and Minnesota.\
\
_The Labor of Women and Children._--If the industries, canals, and\
railways of the country were largely manned by foreign labor, still\
important native sources must not be overlooked; above all, the women\
and children of the New England textile districts. Spinning and weaving,\
by a tradition that runs far beyond the written records of mankind,\
belonged to women. Indeed it was the dexterous housewives, spinsters,\
and boys and girls that laid the foundations of the textile industry in\
America, foundations upon which the mechanical revolution was built. As\
the wheel and loom were taken out of the homes to the factories operated\
by water power or the steam engine, the women and, to use Hamilton's\
phrase, "the children of tender years," followed as a matter of course.\
"The cotton manufacture alone employs six thousand persons in Lowell,"\
wrote a French observer in 1836; "of this number nearly five thousand\
are young women from seventeen to twenty-four years of age, the\
daughters of farmers from the different New England states." It was not\
until after the middle of the century that foreign lands proved to be\
the chief source from which workers were recruited for the factories of\
New England. It was then that the daughters of the Puritans, outdone by\
the competition of foreign labor, both of men and women, left the\
spinning jenny and the loom to other hands.\
\
=The Rise of Organized Labor.=--The changing conditions of American\
life, marked by the spreading mill towns of New England, New York, and\
Pennsylvania and the growth of cities like Buffalo, Cincinnati,\
Louisville, St. Louis, Detroit, and Chicago in the West, naturally\
brought changes, as Jefferson had prophesied, in "manners and morals." A\
few mechanics, smiths, carpenters, and masons, widely scattered through\
farming regions and rural villages, raise no such problems as tens of\
thousands of workers collected in one center in daily intercourse,\
learning the power of cooperation and union.\
\
Even before the coming of steam and machinery, in the "good old days" of\
handicrafts, laborers in many trades--printers, shoemakers, carpenters,\
for example--had begun to draw together in the towns for the advancement\
of their interests in the form of higher wages, shorter days, and\
milder laws. The shoemakers of Philadelphia, organized in 1794,\
conducted a strike in 1799 and held together until indicted seven years\
later for conspiracy. During the twenties and thirties, local labor\
unions sprang up in all industrial centers and they led almost\
immediately to city federations of the several crafts.\
\
As the thousands who were dependent upon their daily labor for their\
livelihood mounted into the millions and industries spread across the\
continent, the local unions of craftsmen grew into national craft\
organizations bound together by the newspapers, the telegraph, and the\
railways. Before 1860 there were several such national trade unions,\
including the plumbers, printers, mule spinners, iron molders, and stone\
cutters. All over the North labor leaders arose--men unknown to general\
history but forceful and resourceful characters who forged links binding\
scattered and individual workers into a common brotherhood. An attempt\
was even made in 1834 to federate all the crafts into a permanent\
national organization; but it perished within three years through lack\
of support. Half a century had to elapse before the American Federation\
of Labor was to accomplish this task.\
\
All the manifestations of the modern labor movement had appeared, in\
germ at least, by the time the mid-century was reached: unions, labor\
leaders, strikes, a labor press, a labor political program, and a labor\
political party. In every great city industrial disputes were a common\
occurrence. The papers recorded about four hundred in two years,\
1853-54, local affairs but forecasting economic struggles in a larger\
field. The labor press seems to have begun with the founding of the\
_Mechanics' Free Press_ in Philadelphia in 1828 and the establishment of\
the New York _Workingman's Advocate_ shortly afterward. These\
semi-political papers were in later years followed by regular trade\
papers designed to weld together and advance the interests of particular\
crafts. Edited by able leaders, these little sheets with limited\
circulation wielded an enormous influence in the ranks of the workers.\
\
=Labor and Politics.=--As for the political program of labor, the main\
planks were clear and specific: the abolition of imprisonment for debt,\
manhood suffrage in states where property qualifications still\
prevailed, free and universal education, laws protecting the safety and\
health of workers in mills and factories, abolition of lotteries, repeal\
of laws requiring militia service, and free land in the West.\
\
Into the labor papers and platforms there sometimes crept a note of\
hostility to the masters of industry, a sign of bitterness that excited\
little alarm while cheap land in the West was open to the discontented.\
The Philadelphia workmen, in issuing a call for a local convention,\
invited "all those of our fellow citizens who live by their own labor\
and none other." In Newcastle county, Delaware, the association of\
working people complained in 1830: "The poor have no laws; the laws are\
made by the rich and of course for the rich." Here and there an\
extremist went to the length of advocating an equal division of wealth\
among all the people--the crudest kind of communism.\
\
Agitation of this character produced in labor circles profound distrust\
of both Whigs and Democrats who talked principally about tariffs and\
banks; it resulted in attempts to found independent labor parties. In\
Philadelphia, Albany, New York City, and New England, labor candidates\
were put up for elections in the early thirties and in a few cases were\
victorious at the polls. "The balance of power has at length got into\
the hands of the working people, where it properly belongs,"\
triumphantly exclaimed the _Mechanics' Free Press_ of Philadelphia in\
1829. But the triumph was illusory. Dissensions appeared in the labor\
ranks. The old party leaders, particularly of Tammany Hall, the\
Democratic party organization in New York City, offered concessions to\
labor in return for votes. Newspapers unsparingly denounced "trade union\
politicians" as "demagogues," "levellers," and "rag, tag, and bobtail";\
and some of them, deeming labor unrest the sour fruit of manhood\
suffrage, suggested disfranchisement as a remedy. Under the influence\
of concessions and attacks the political fever quickly died away, and\
the end of the decade left no remnant of the labor political parties.\
Labor leaders turned to a task which seemed more substantial and\
practical, that of organizing workingmen into craft unions for the\
definite purpose of raising wages and reducing hours.\
\
\
THE INDUSTRIAL REVOLUTION AND NATIONAL POLITICS\
\
=Southern Plans for Union with the West.=--It was long the design of\
Southern statesmen like Calhoun to hold the West and the South together\
in one political party. The theory on which they based their hope was\
simple. Both sections were agricultural--the producers of raw materials\
and the buyers of manufactured goods. The planters were heavy purchasers\
of Western bacon, pork, mules, and grain. The Mississippi River and its\
tributaries formed the natural channel for the transportation of heavy\
produce southward to the plantations and outward to Europe. Therefore,\
ran their political reasoning, the interests of the two sections were\
one. By standing together in favor of low tariffs, they could buy their\
manufactures cheaply in Europe and pay for them in cotton, tobacco, and\
grain. The union of the two sections under Jackson's management seemed\
perfect.\
\
=The East Forms Ties with the West.=--Eastern leaders were not blind to\
the ambitions of Southern statesmen. On the contrary, they also\
recognized the importance of forming strong ties with the agrarian West\
and drawing the produce of the Ohio Valley to Philadelphia and New York.\
The canals and railways were the physical signs of this economic union,\
and the results, commercial and political, were soon evident. By the\
middle of the century, Southern economists noted the change, one of\
them, De Bow, lamenting that "the great cities of the North have\
severally penetrated the interior with artificial lines until they have\
taken from the open and untaxed current of the Mississippi the commerce\
produced on its borders." To this writer it was an astounding thing to\
behold "the number of steamers that now descend the upper Mississippi\
River, loaded to the guards with produce, as far as the mouth of the\
Illinois River and then turn up that stream with their cargoes to be\
shipped to New York _via_ Chicago. The Illinois canal has not only swept\
the whole produce along the line of the Illinois River to the East, but\
it is drawing the products of the upper Mississippi through the same\
channel; thus depriving New Orleans and St. Louis of a rich portion of\
their former trade."\
\
If to any shippers the broad current of the great river sweeping down to\
New Orleans offered easier means of physical communication to the sea\
than the canals and railways, the difference could be overcome by the\
credit which Eastern bankers were able to extend to the grain and\
produce buyers, in the first instance, and through them to the farmers\
on the soil. The acute Southern observer just quoted, De Bow, admitted\
with evident regret, in 1852, that "last autumn, the rich regions of\
Ohio, Indiana, and Illinois were flooded with the local bank notes of\
the Eastern States, advanced by the New York houses on produce to be\
shipped by way of the canals in the spring.... These moneyed facilities\
enable the packer, miller, and speculator to hold on to their produce\
until the opening of navigation in the spring and they are no longer\
obliged, as formerly, to hurry off their shipments during the winter by\
the way of New Orleans in order to realize funds by drafts on their\
shipments. The banking facilities at the East are doing as much to draw\
trade from us as the canals and railways which Eastern capital is\
constructing." Thus canals, railways, and financial credit were swiftly\
forging bonds of union between the old home of Jacksonian Democracy in\
the West and the older home of Federalism in the East. The nationalism\
to which Webster paid eloquent tribute became more and more real with\
the passing of time. The self-sufficiency of the pioneer was broken down\
as he began to watch the produce markets of New York and Philadelphia\
where the prices of corn and hogs fixed his earnings for the year.\
\
=The West and Manufactures.=--In addition to the commercial bonds\
between the East and the West there was growing up a common interest in\
manufactures. As skilled white labor increased in the Ohio Valley, the\
industries springing up in the new cities made Western life more like\
that of the industrial East than like that of the planting South.\
Moreover, the Western states produced some important raw materials for\
American factories, which called for protection against foreign\
competition, notably, wool, hemp, and flax. As the South had little or\
no foreign competition in cotton and tobacco, the East could not offer\
protection for her raw materials in exchange for protection for\
industries. With the West, however, it became possible to establish\
reciprocity in tariffs; that is, for example, to trade a high rate on\
wool for a high rate on textiles or iron.\
\
=The South Dependent on the North.=--While East and West were drawing\
together, the distinctions between North and South were becoming more\
marked; the latter, having few industries and producing little save raw\
materials, was being forced into the position of a dependent section. As\
a result of the protective tariff, Southern planters were compelled to\
turn more and more to Northern mills for their cloth, shoes, hats, hoes,\
plows, and machinery. Nearly all the goods which they bought in Europe\
in exchange for their produce came overseas to Northern ports, whence\
transshipments were made by rail and water to Southern points of\
distribution. Their rice, cotton, and tobacco, in as far as they were\
not carried to Europe in British bottoms, were transported by Northern\
masters. In these ways, a large part of the financial operations\
connected with the sale of Southern produce and the purchase of goods in\
exchange passed into the hands of Northern merchants and bankers who,\
naturally, made profits from their transactions. Finally, Southern\
planters who wanted to buy more land and more slaves on credit borrowed\
heavily in the North where huge accumulations made the rates of interest\
lower than the smaller banks of the South could afford.\
\
=The South Reckons the Cost of Economic Dependence.=--As Southern\
dependence upon Northern capital became more and more marked, Southern\
leaders began to chafe at what they regarded as restraints laid upon\
their enterprise. In a word, they came to look upon the planter as a\
tribute-bearer to the manufacturer and financier. "The South,"\
expostulated De Bow, "stands in the attitude of feeding ... a vast\
population of [Northern] merchants, shipowners, capitalists, and others\
who, without claims on her progeny, drink up the life blood of her\
trade.... Where goes the value of our labor but to those who, taking\
advantage of our folly, ship for us, buy for us, sell to us, and, after\
turning our own capital to their profitable account, return laden with\
our money to enjoy their easily earned opulence at home."\
\
Southern statisticians, not satisfied with generalities, attempted to\
figure out how great was this tribute in dollars and cents. They\
estimated that the planters annually lent to Northern merchants the full\
value of their exports, a hundred millions or more, "to be used in the\
manipulation of foreign imports." They calculated that no less than\
forty millions all told had been paid to shipowners in profits. They\
reckoned that, if the South were to work up her own cotton, she would\
realize from seventy to one hundred millions a year that otherwise went\
North. Finally, to cap the climax, they regretted that planters spent\
some fifteen millions a year pleasure-seeking in the alluring cities and\
summer resorts of the North.\
\
=Southern Opposition to Northern Policies.=--Proceeding from these\
premises, Southern leaders drew the logical conclusion that the entire\
program of economic measures demanded in the North was without exception\
adverse to Southern interests and, by a similar chain of reasoning,\
injurious to the corn and wheat producers of the West. Cheap labor\
afforded by free immigration, a protective tariff raising prices of\
manufactures for the tiller of the soil, ship subsidies increasing the\
tonnage of carrying trade in Northern hands, internal improvements\
forging new economic bonds between the East and the West, a national\
banking system giving strict national control over the currency as a\
safeguard against paper inflation--all these devices were regarded in\
the South as contrary to the planting interest. They were constantly\
compared with the restrictive measures by which Great Britain more than\
half a century before had sought to bind American interests.\
\
As oppression justified a war for independence once, statesmen argued,\
so it can justify it again. "It is curious as it is melancholy and\
distressing," came a broad hint from South Carolina, "to see how\
striking is the analogy between the colonial vassalage to which the\
manufacturing states have reduced the planting states and that which\
formerly bound the Anglo-American colonies to the British empire....\
England said to her American colonies: 'You shall not trade with the\
rest of the world for such manufactures as are produced in the mother\
country.' The manufacturing states say to their Southern colonies: 'You\
shall not trade with the rest of the world for such manufactures as we\
produce.'" The conclusion was inexorable: either the South must control\
the national government and its economic measures, or it must declare,\
as America had done four score years before, its political and economic\
independence. As Northern mills multiplied, as railways spun their\
mighty web over the face of the North, and as accumulated capital rose\
into the hundreds of millions, the conviction of the planters and their\
statesmen deepened into desperation.\
\
=Efforts to Start Southern Industries Fail.=--A few of them, seeing the\
predominance of the North, made determined efforts to introduce\
manufactures into the South. To the leaders who were averse to secession\
and nullification this seemed the only remedy for the growing disparity\
in the power of the two sections. Societies for the encouragement of\
mechanical industries were formed, the investment of capital was sought,\
and indeed a few mills were built on Southern soil. The results were\
meager. The natural resources, coal and water power, were abundant; but\
the enterprise for direction and the skilled labor were wanting. The\
stream of European immigration flowed North and West, not South. The\
Irish or German laborer, even if he finally made his home in a city, had\
before him, while in the North, the alternative of a homestead on\
Western land. To him slavery was a strange, if not a repelling,\
institution. He did not take to it kindly nor care to fix his home where\
it flourished. While slavery lasted, the economy of the South was\
inevitably agricultural. While agriculture predominated, leadership with\
equal necessity fell to the planting interest. While the planting\
interest ruled, political opposition to Northern economy was destined to\
grow in strength.\
\
=The Southern Theory of Sectionalism.=--In the opinion of the statesmen\
who frankly represented the planting interest, the industrial system was\
its deadly enemy. Their entire philosophy of American politics was\
summed up in a single paragraph by McDuffie, a spokesman for South\
Carolina: "Owing to the federative character of our government, the\
great geographical extent of our territory, and the diversity of the\
pursuits of our citizens in different parts of the union, it has so\
happened that two great interests have sprung up, standing directly\
opposed to each other. One of these consists of those manufactures which\
the Northern and Middle states are capable of producing but which, owing\
to the high price of labor and the high profits of capital in those\
states, cannot hold competition with foreign manufactures without the\
aid of bounties, directly or indirectly given, either by the general\
government or by the state governments. The other of these interests\
consists of the great agricultural staples of the Southern states which\
can find a market only in foreign countries and which can be\
advantageously sold only in exchange for foreign manufactures which come\
in competition with those of the Northern and Middle states.... These\
interests then stand diametrically and irreconcilably opposed to each\
other. The interest, the pecuniary interest of the Northern\
manufacturer, is directly promoted by every increase of the taxes\
imposed upon Southern commerce; and it is unnecessary to add that the\
interest of the Southern planter is promoted by every diminution of\
taxes imposed upon the productions of their industry. If, under these\
circumstances, the manufacturers were clothed with the power of imposing\
taxes, at their pleasure, upon the foreign imports of the planter, no\
doubt would exist in the mind of any man that it would have all the\
characteristics of an absolute and unqualified despotism." The economic\
soundness of this reasoning, a subject of interesting speculation for\
the economist, is of little concern to the historian. The historical\
point is that this opinion was widely held in the South and with the\
progress of time became the prevailing doctrine of the planting\
statesmen.\
\
Their antagonism was deepened because they also became convinced, on\
what grounds it is not necessary to inquire, that the leaders of the\
industrial interest thus opposed to planting formed a consolidated\
"aristocracy of wealth," bent upon the pursuit and attainment of\
political power at Washington. "By the aid of various associated\
interests," continued McDuffie, "the manufacturing capitalists have\
obtained a complete and permanent control over the legislation of\
Congress on this subject [the tariff].... Men confederated together upon\
selfish and interested principles, whether in pursuit of the offices or\
the bounties of the government, are ever more active and vigilant than\
the great majority who act from disinterested and patriotic impulses.\
Have we not witnessed it on this floor, sir? Who ever knew the tariff\
men to divide on any question affecting their confederated interests?...\
The watchword is, stick together, right or wrong upon every question\
affecting the common cause. Such, sir, is the concert and vigilance and\
such the combinations by which the manufacturing party, acting upon the\
interests of some and the prejudices of others, have obtained a decided\
and permanent control over public opinion in all the tariff states."\
Thus, as the Southern statesman would have it, the North, in matters\
affecting national policies, was ruled by a "confederated interest"\
which menaced the planting interest. As the former grew in magnitude and\
attached to itself the free farmers of the West through channels of\
trade and credit, it followed as night the day that in time the planters\
would be overshadowed and at length overborne in the struggle of giants.\
Whether the theory was sound or not, Southern statesmen believed it and\
acted upon it.\
\
\
=References=\
\
M. Beard, _Short History of the American Labor Movement_.\
\
E.L. Bogart, _Economic History of the United States_.\
\
J.R. Commons, _History of Labour in the United States_ (2 vols.).\
\
E.R. Johnson, _American Railway Transportation_.\
\
C.D. Wright, _Industrial Evolution of the United States_.\
\
\
=Questions=\
\
1. What signs pointed to a complete Democratic triumph in 1852?\
\
2. What is the explanation of the extraordinary industrial progress of\
America?\
\
3. Compare the planting system with the factory system.\
\
4. In what sections did industry flourish before the Civil War? Why?\
\
5. Show why transportation is so vital to modern industry and\
agriculture.\
\
6. Explain how it was possible to secure so many people to labor in\
American industries.\
\
7. Trace the steps in the rise of organized labor before 1860.\
\
8. What political and economic reforms did labor demand?\
\
9. Why did the East and the South seek closer ties with the West?\
\
10. Describe the economic forces which were drawing the East and the\
West together.\
\
11. In what way was the South economically dependent upon the North?\
\
12 State the national policies generally favored in the North and\
condemned in the South.\
\
13. Show how economic conditions in the South were unfavorable to\
industry.\
\
14. Give the Southern explanation of the antagonism between the North\
and the South.\
\
\
=Research Topics=\
\
=The Inventions.=--Assign one to each student. Satisfactory accounts are\
to be found in any good encyclopedia, especially the Britannica.\
\
=River and Lake Commerce.=--Callender, _Economic History of the United\
States_, pp. 313-326.\
\
=Railways and Canals.=--Callender, pp. 326-344; 359-387. Coman,\
_Industrial History of the United States_, pp. 216-225.\
\
=The Growth of Industry, 1815-1840.=--Callender, pp. 459-471. From 1850\
to 1860, Callender, pp. 471-486.\
\
=Early Labor Conditions.=--Callender, pp. 701-718.\
\
=Early Immigration.=--Callender, pp. 719-732.\
\
=Clay's Home Market Theory of the Tariff.=--Callender, pp. 498-503.\
\
=The New England View of the Tariff.=--Callender, pp. 503-514.\
\
\
\
\
CHAPTER XIV\
\
THE PLANTING SYSTEM AND NATIONAL POLITICS\
\
\
James Madison, the father of the federal Constitution, after he had\
watched for many days the battle royal in the national convention of\
1787, exclaimed that the contest was not between the large and the small\
states, but between the commercial North and the planting South. From\
the inauguration of Washington to the election of Lincoln the sectional\
conflict, discerned by this penetrating thinker, exercised a profound\
influence on the course of American politics. It was latent during the\
"era of good feeling" when the Jeffersonian Republicans adopted\
Federalist policies; it flamed up in the contest between the Democrats\
and Whigs. Finally it raged in the angry political quarrel which\
culminated in the Civil War.\
\
\
SLAVERY--NORTH AND SOUTH\
\
=The Decline of Slavery in the North.=--At the time of the adoption of\
the Constitution, slavery was lawful in all the Northern states except\
Massachusetts. There were almost as many bondmen in New York as in\
Georgia. New Jersey had more than Delaware or Tennessee, indeed nearly\
as many as both combined. All told, however, there were only about forty\
thousand in the North as against nearly seven hundred thousand in the\
South. Moreover, most of the Northern slaves were domestic servants, not\
laborers necessary to keep mills going or fields under cultivation.\
\
There was, in the North, a steadily growing moral sentiment against the\
system. Massachusetts abandoned it in 1780. In the same year,\
Pennsylvania provided for gradual emancipation. New Hampshire, where\
there had been only a handful, Connecticut with a few thousand\
domestics, and New Jersey early followed these examples. New York, in\
1799, declared that all children born of slaves after July 4 of that\
year should be free, though held for a term as apprentices; and in 1827\
it swept away the last vestiges of slavery. So with the passing of the\
generation that had framed the Constitution, chattel servitude\
disappeared in the commercial states, leaving behind only such\
discriminations as disfranchisement or high property qualifications on\
colored voters.\
\
=The Growth of Northern Sentiment against Slavery.=--In both sections of\
the country there early existed, among those more or less\
philosophically inclined, a strong opposition to slavery on moral as\
well as economic grounds. In the constitutional convention of 1787,\
Gouverneur Morris had vigorously condemned it and proposed that the\
whole country should bear the cost of abolishing it. About the same time\
a society for promoting the abolition of slavery, under the presidency\
of Benjamin Franklin, laid before Congress a petition that serious\
attention be given to the emancipation of "those unhappy men who alone\
in this land of freedom are degraded into perpetual bondage." When\
Congress, acting on the recommendations of President Jefferson, provided\
for the abolition of the foreign slave trade on January 1, 1808, several\
Northern members joined with Southern members in condemning the system\
as well as the trade. Later, colonization societies were formed to\
encourage the emancipation of slaves and their return to Africa. James\
Madison was president and Henry Clay vice president of such an\
organization.\
\
The anti-slavery sentiment of which these were the signs was\
nevertheless confined to narrow circles and bore no trace of bitterness.\
\
"We consider slavery your calamity, not your crime," wrote a\
distinguished Boston clergyman to his Southern brethren, "and we will\
share with you the burden of putting an end to it. We will consent that\
the public lands shall be appropriated to this object.... I deprecate\
everything which sows discord and exasperating sectional animosities."\
\
=Uncompromising Abolition.=--In a little while the spirit of generosity\
was gone. Just as Jacksonian Democracy rose to power there appeared a\
new kind of anti-slavery doctrine--the dogmatism of the abolition\
agitator. For mild speculation on the evils of the system was\
substituted an imperious and belligerent demand for instant\
emancipation. If a date must be fixed for its appearance, the year 1831\
may be taken when William Lloyd Garrison founded in Boston his\
anti-slavery paper, _The Liberator_. With singleness of purpose and\
utter contempt for all opposing opinions and arguments, he pursued his\
course of passionate denunciation. He apologized for having ever\
"assented to the popular but pernicious doctrine of gradual abolition."\
He chose for his motto: "Immediate and unconditional emancipation!" He\
promised his readers that he would be "harsh as truth and uncompromising\
as justice"; that he would not "think or speak or write with\
moderation." Then he flung out his defiant call: "I am in earnest--I\
will not equivocate--I will not excuse--I will not retreat a single\
inch--and I will be heard....\
\
     'Such is the vow I take, so help me God.'"\
\
Though Garrison complained that "the apathy of the people is enough to\
make every statue leap from its pedestal," he soon learned how alive the\
masses were to the meaning of his propaganda. Abolition orators were\
stoned in the street and hissed from the platform. Their meeting places\
were often attacked and sometimes burned to the ground. Garrison himself\
was assaulted in the streets of Boston, finding refuge from the angry\
mob behind prison bars. Lovejoy, a publisher in Alton, Illinois, for his\
willingness to give abolition a fair hearing, was brutally murdered; his\
printing press was broken to pieces as a warning to all those who\
disturbed the nation's peace of mind. The South, doubly frightened by a\
slave revolt in 1831 which ended in the murder of a number of men,\
women, and children, closed all discussion of slavery in that section.\
"Now," exclaimed Calhoun, "it is a question which admits of neither\
concession nor compromise."\
\
As the opposition hardened, the anti-slavery agitation gathered in force\
and intensity. Whittier blew his blast from the New England hills:\
\
    "No slave-hunt in our borders--no pirate on our strand;\
     No fetters in the Bay State--no slave upon our land."\
\
Lowell, looking upon the espousal of a great cause as the noblest aim of\
his art, ridiculed and excoriated bondage in the South. Those\
abolitionists, not gifted as speakers or writers, signed petitions\
against slavery and poured them in upon Congress. The flood of them was\
so continuous that the House of Representatives, forgetting its\
traditions, adopted in 1836 a "gag rule" which prevented the reading of\
appeals and consigned them to the waste basket. Not until the Whigs were\
in power nearly ten years later was John Quincy Adams able, after a\
relentless campaign, to carry a motion rescinding the rule.\
\
How deep was the impression made upon the country by this agitation for\
immediate and unconditional emancipation cannot be measured. If the\
popular vote for those candidates who opposed not slavery, but its\
extension to the territories, be taken as a standard, it was slight\
indeed. In 1844, the Free Soil candidate, Birney, polled 62,000 votes\
out of over a million and a half; the Free Soil vote of the next\
campaign went beyond a quarter of a million, but the increase was due to\
the strength of the leader, Martin Van Buren; four years afterward it\
receded to 156,000, affording all the outward signs for the belief that\
the pleas of the abolitionist found no widespread response among the\
people. Yet the agitation undoubtedly ran deeper than the ballot box.\
Young statesmen of the North, in whose hands the destiny of frightful\
years was to lie, found their indifference to slavery broken and their\
consciences stirred by the unending appeal and the tireless reiteration.\
Charles Sumner afterward boasted that he read the _Liberator_ two years\
before Wendell Phillips, the young Boston lawyer who cast aside his\
profession to take up the dangerous cause.\
\
=Early Southern Opposition to Slavery.=--In the South, the sentiment\
against slavery was strong; it led some to believe that it would also\
come to an end there in due time. Washington disliked it and directed in\
his will that his own slaves should be set free after the death of his\
wife. Jefferson, looking into the future, condemned the system by which\
he also lived, saying: "Can the liberties of a nation be thought secure\
when we have removed their only firm basis, a conviction in the minds of\
the people that their liberties are the gift of God? Are they not to be\
violated but with His wrath? Indeed I tremble for my country when I\
reflect that God is just; that His justice cannot sleep forever." Nor\
did Southern men confine their sentiments to expressions of academic\
opinion. They accepted in 1787 the Ordinance which excluded slavery from\
the Northwest territory forever and also the Missouri Compromise, which\
shut it out of a vast section of the Louisiana territory.\
\
=The Revolution in the Slave System.=--Among the representatives of\
South Carolina and Georgia, however, the anti-slavery views of\
Washington and Jefferson were by no means approved; and the drift of\
Southern economy was decidedly in favor of extending and perpetuating,\
rather than abolishing, the system of chattel servitude. The invention\
of the cotton gin and textile machinery created a market for cotton\
which the planters, with all their skill and energy, could hardly\
supply. Almost every available acre was brought under cotton culture as\
the small farmers were driven steadily from the seaboard into the\
uplands or to the Northwest.\
\
The demand for slaves to till the swiftly expanding fields was enormous.\
The number of bondmen rose from 700,000 in Washington's day to more than\
three millions in 1850. At the same time slavery itself was transformed.\
Instead of the homestead where the same family of masters kept the same\
families of slaves from generation to generation, came the plantation\
system of the Far South and Southwest where masters were ever moving and\
ever extending their holdings of lands and slaves. This in turn reacted\
on the older South where the raising of slaves for the market became a\
regular and highly profitable business.\
\
[Illustration: _From an old print_\
\
JOHN C. CALHOUN]\
\
=Slavery Defended as a Positive Good.=--As the abolition agitation\
increased and the planting system expanded, apologies for slavery became\
fainter and fainter in the South. Then apologies were superseded by\
claims that slavery was a beneficial scheme of labor control. Calhoun,\
in a famous speech in the Senate in 1837, sounded the new note by\
declaring slavery "instead of an evil, a good--a positive good." His\
reasoning was as follows: in every civilized society one portion of the\
community must live on the labor of another; learning, science, and the\
arts are built upon leisure; the African slave, kindly treated by his\
master and mistress and looked after in his old age, is better off than\
the free laborers of Europe; and under the slave system conflicts\
between capital and labor are avoided. The advantages of slavery in this\
respect, he concluded, "will become more and more manifest, if left\
undisturbed by interference from without, as the country advances in\
wealth and numbers."\
\
=Slave Owners Dominate Politics.=--The new doctrine of Calhoun was\
eagerly seized by the planters as they came more and more to overshadow\
the small farmers of the South and as they beheld the menace of\
abolition growing upon the horizon. It formed, as they viewed matters, a\
moral defense for their labor system--sound, logical, invincible. It\
warranted them in drawing together for the protection of an institution\
so necessary, so inevitable, so beneficent.\
\
Though in 1850 the slave owners were only about three hundred and fifty\
thousand in a national population of nearly twenty million whites, they\
had an influence all out of proportion to their numbers. They were knit\
together by the bonds of a common interest. They had leisure and wealth.\
They could travel and attend conferences and conventions. Throughout the\
South and largely in the North, they had the press, the schools, and the\
pulpits on their side. They formed, as it were, a mighty union for the\
protection and advancement of their common cause. Aided by those\
mechanics and farmers of the North who stuck by Jacksonian Democracy\
through thick and thin, the planters became a power in the federal\
government. "We nominate Presidents," exultantly boasted a Richmond\
newspaper; "the North elects them."\
\
This jubilant Southern claim was conceded by William H. Seward, a\
Republican Senator from New York, in a speech describing the power of\
slavery in the national government. "A party," he said, "is in one sense\
a joint stock association, in which those who contribute most direct the\
action and management of the concern.... The slaveholders, contributing\
in an overwhelming proportion to the strength of the Democratic party,\
necessarily dictate and prescribe its policy." He went on: "The\
slaveholding class has become the governing power in each of the\
slaveholding states and it practically chooses thirty of the sixty-two\
members of the Senate, ninety of the two hundred and thirty-three\
members of the House of Representatives, and one hundred and five of the\
two hundred and ninety-five electors of President and Vice-President of\
the United States." Then he considered the slave power in the Supreme\
Court. "That tribunal," he exclaimed, "consists of a chief justice and\
eight associate justices. Of these, five were called from slave states\
and four from free states. The opinions and bias of each of them were\
carefully considered by the President and Senate when he was appointed.\
Not one of them was found wanting in soundness of politics, according to\
the slaveholder's exposition of the Constitution." Such was the Northern\
view of the planting interest that, from the arena of national politics,\
challenged the whole country in 1860.\
\
[Illustration: DISTRIBUTION OF SLAVES IN THE SOUTHERN STATES]\
\
\
SLAVERY IN NATIONAL POLITICS\
\
=National Aspects of Slavery.=--It may be asked why it was that slavery,\
founded originally on state law and subject to state government, was\
drawn into the current of national affairs. The answer is simple. There\
were, in the first place, constitutional reasons. The Congress of the\
United States had to make all needful rules for the government of the\
territories, the District of Columbia, the forts and other property\
under national authority; so it was compelled to determine whether\
slavery should exist in the places subject to its jurisdiction. Upon\
Congress was also conferred the power of admitting new states; whenever\
a territory asked for admission, the issue could be raised as to whether\
slavery should be sanctioned or excluded. Under the Constitution,\
provision was made for the return of runaway slaves; Congress had the\
power to enforce this clause by appropriate legislation. Since the\
control of the post office was vested in the federal government, it had\
to face the problem raised by the transmission of abolition literature\
through the mails. Finally citizens had the right of petition; it\
inheres in all free government and it is expressly guaranteed by the\
first amendment to the Constitution. It was therefore legal for\
abolitionists to present to Congress their petitions, even if they asked\
for something which it had no right to grant. It was thus impossible,\
constitutionally, to draw a cordon around the slavery issue and confine\
the discussion of it to state politics.\
\
There were, in the second place, economic reasons why slavery was\
inevitably drawn into the national sphere. It was the basis of the\
planting system which had direct commercial relations with the North and\
European countries; it was affected by federal laws respecting tariffs,\
bounties, ship subsidies, banking, and kindred matters. The planters of\
the South, almost without exception, looked upon the protective tariff\
as a tribute laid upon them for the benefit of Northern industries. As\
heavy borrowers of money in the North, they were generally in favor of\
"easy money," if not paper currency, as an aid in the repayment of their\
debts. This threw most of them into opposition to the Whig program for a\
United States Bank. All financial aids to American shipping they stoutly\
resisted, preferring to rely upon the cheaper service rendered by\
English shippers. Internal improvements, those substantial ties that\
were binding the West to the East and turning the traffic from New\
Orleans to Philadelphia and New York, they viewed with alarm. Free\
homesteads from the public lands, which tended to overbalance the South\
by building free states, became to them a measure dangerous to their\
interests. Thus national economic policies, which could not by any twist\
or turn be confined to state control, drew the slave system and its\
defenders into the political conflict that centered at Washington.\
\
=Slavery and the Territories--the Missouri Compromise (1820).=--Though\
men continually talked about "taking slavery out of politics," it could\
not be done. By 1818 slavery had become so entrenched and the\
anti-slavery sentiment so strong, that Missouri's quest for admission\
brought both houses of Congress into a deadlock that was broken only by\
compromise. The South, having half the Senators, could prevent the\
admission of Missouri stripped of slavery; and the North, powerful in\
the House of Representatives, could keep Missouri with slavery out of\
the union indefinitely. An adjustment of pretensions was the last\
resort. Maine, separated from the parent state of Massachusetts, was\
brought into the union with freedom and Missouri with bondage. At the\
same time it was agreed that the remainder of the vast Louisiana\
territory north of the parallel of 36 o 30' should be, like the old\
Northwest, forever free; while the southern portion was left to slavery.\
In reality this was an immense gain for liberty. The area dedicated to\
free farmers was many times greater than that left to the planters. The\
principle was once more asserted that Congress had full power to prevent\
slavery in the territories.\
\
[Illustration: THE MISSOURI COMPROMISE]\
\
=The Territorial Question Reopened by the Wilmot Proviso.=--To the\
Southern leaders, the annexation of Texas and the conquest of Mexico\
meant renewed security to the planting interest against the increasing\
wealth and population of the North. Texas, it was said, could be divided\
into four slave states. The new territories secured by the treaty of\
peace with Mexico contained the promise of at least three more. Thus, as\
each new free soil state knocked for admission into the union, the\
South could demand as the price of its consent a new slave state. No\
wonder Southern statesmen saw, in the annexation of Texas and the\
conquest of Mexico, slavery and King Cotton triumphant--secure for all\
time against adverse legislation. Northern leaders were equally\
convinced that the Southern prophecy was true. Abolitionists and\
moderate opponents of slavery alike were in despair. Texas, they\
lamented, would fasten slavery upon the country forevermore. "No living\
man," cried one, "will see the end of slavery in the United States!"\
\
It so happened, however, that the events which, it was thought, would\
secure slavery let loose a storm against it. A sign appeared first on\
August 6, 1846, only a few months after war was declared on Mexico. On\
that day, David Wilmot, a Democrat from Pennsylvania, introduced into\
the House of Representatives a resolution to the effect that, as an\
express and fundamental condition to the acquisition of any territory\
from the republic of Mexico, slavery should be forever excluded from\
every part of it. "The Wilmot Proviso," as the resolution was popularly\
called, though defeated on that occasion, was a challenge to the South.\
\
The South answered the challenge. Speaking in the House of\
Representatives, Robert Toombs of Georgia boldly declared: "In the\
presence of the living God, if by your legislation you seek to drive us\
from the territories of California and New Mexico ... I am for\
disunion." South Carolina announced that the day for talk had passed and\
the time had come to join her sister states "in resisting the\
application of the Wilmot Proviso at any and all hazards." A conference,\
assembled at Jackson, Mississippi, in the autumn of 1849, called a\
general convention of Southern states to meet at Nashville the following\
summer. The avowed purpose was to arrest "the course of aggression" and,\
if that was not possible, to provide "in the last resort for their\
separate welfare by the formation of a compact and union that will\
afford protection to their liberties and rights." States that had\
spurned South Carolina's plea for nullification in 1832 responded to\
this new appeal with alacrity--an augury of the secession to come.\
\
[Illustration: _From an old print._\
\
HENRY CLAY]\
\
=The Great Debate of 1850.=--The temper of the country was white hot\
when Congress convened in December, 1849. It was a memorable session,\
memorable for the great men who took part in the debates and memorable\
for the grand Compromise of 1850 which it produced. In the Senate sat\
for the last time three heroic figures: Webster from the North, Calhoun\
from the South, and Clay from a border state. For nearly forty years\
these three had been leaders of men. All had grown old and gray in\
service. Calhoun was already broken in health and in a few months was to\
be borne from the political arena forever. Clay and Webster had but two\
more years in their allotted span.\
\
Experience, learning, statecraft--all these things they now marshaled in\
a mighty effort to solve the slavery problem. On January 29, 1850, Clay\
offered to the Senate a compromise granting concessions to both sides;\
and a few days later, in a powerful oration, he made a passionate appeal\
for a union of hearts through mutual sacrifices. Calhoun relentlessly\
demanded the full measure of justice for the South: equal rights in the\
territories bought by common blood; the return of runaway slaves as\
required by the Constitution; the suppression of the abolitionists; and\
the restoration of the balance of power between the North and the South.\
Webster, in his notable "Seventh of March speech," condemned the Wilmot\
Proviso, advocated a strict enforcement of the fugitive slave law,\
denounced the abolitionists, and made a final plea for the Constitution,\
union, and liberty. This was the address which called forth from\
Whittier the poem, "Ichabod," deploring the fall of the mighty one whom\
he thought lost to all sense of faith and honor.\
\
=The Terms of the Compromise of 1850.=--When the debates were closed,\
the results were totaled in a series of compromise measures, all of\
which were signed in September, 1850, by the new President, Millard\
Fillmore, who had taken office two months before on the death of Zachary\
Taylor. By these acts the boundaries of Texas were adjusted and the\
territory of New Mexico created, subject to the provision that all or\
any part of it might be admitted to the union "with or without slavery\
as their constitution may provide at the time of their admission." The\
Territory of Utah was similarly organized with the same conditions as to\
slavery, thus repudiating the Wilmot Proviso without guaranteeing\
slavery to the planters. California was admitted as a free state under a\
constitution in which the people of the territory had themselves\
prohibited slavery.\
\
The slave trade was abolished in the District of Columbia, but slavery\
itself existed as before at the capital of the nation. This concession\
to anti-slavery sentiment was more than offset by a fugitive slave law,\
drastic in spirit and in letter. It placed the enforcement of its terms\
in the hands of federal officers appointed from Washington and so\
removed it from the control of authorities locally elected. It provided\
that masters or their agents, on filing claims in due form, might\
summarily remove their escaped slaves without affording their "alleged\
fugitives" the right of trial by jury, the right to witness, the right\
to offer any testimony in evidence. Finally, to "put teeth" into the\
act, heavy penalties were prescribed for all who obstructed or assisted\
in obstructing the enforcement of the law. Such was the Great Compromise\
of 1850.\
\
[Illustration: AN OLD CARTOON REPRESENTING WEBSTER "STEALING CLAY'S\
THUNDER"]\
\
=The Pro-slavery Triumph in the Election of 1852.=--The results of the\
election of 1852 seemed to show conclusively that the nation was weary\
of slavery agitation and wanted peace. Both parties, Whigs and\
Democrats, endorsed the fugitive slave law and approved the Great\
Compromise. The Democrats, with Franklin Pierce as their leader, swept\
the country against the war hero, General Winfield Scott, on whom the\
Whigs had staked their hopes. Even Webster, broken with grief at his\
failure to receive the nomination, advised his friends to vote for\
Pierce and turned away from politics to meditate upon approaching death.\
The verdict of the voters would seem to indicate that for the time\
everybody, save a handful of disgruntled agitators, looked upon Clay's\
settlement as the last word. "The people, especially the business men of\
the country," says Elson, "were utterly weary of the agitation and they\
gave their suffrages to the party that promised them rest." The Free\
Soil party, condemning slavery as "a sin against God and a crime against\
man," and advocating freedom for the territories, failed to carry a\
single state. In fact it polled fewer votes than it had four years\
earlier--156,000 as against nearly 3,000,000, the combined vote of the\
Whigs and Democrats. It is not surprising, therefore, that President\
Pierce, surrounded in his cabinet by strong Southern sympathizers, could\
promise to put an end to slavery agitation and to crush the abolition\
movement in the bud.\
\
=Anti-slavery Agitation Continued.=--The promise was more difficult to\
fulfill than to utter. In fact, the vigorous execution of one measure\
included in the Compromise--the fugitive slave law--only made matters\
worse. Designed as security for the planters, it proved a powerful\
instrument in their undoing. Slavery five hundred miles away on a\
Louisiana plantation was so remote from the North that only the\
strongest imagination could maintain a constant rage against it. "Slave\
catching," "man hunting" by federal officers on the streets of\
Philadelphia, New York, Boston, Chicago, or Milwaukee and in the hamlets\
and villages of the wide-stretching farm lands of the North was another\
matter. It brought the most odious aspects of slavery home to thousands\
of men and women who would otherwise have been indifferent to the\
system. Law-abiding business men, mechanics, farmers, and women, when\
they saw peaceful negroes, who had resided in their neighborhoods\
perhaps for years, torn away by federal officers and carried back to\
bondage, were transformed into enemies of the law. They helped slaves to\
escape; they snatched them away from officers who had captured them;\
they broke open jails and carried fugitives off to Canada.\
\
Assistance to runaway slaves, always more or less common in the North,\
was by this time organized into a system. Regular routes, known as\
"underground railways," were laid out across the free states into\
Canada, and trusted friends of freedom maintained "underground stations"\
where fugitives were concealed in the daytime between their long night\
journeys. Funds were raised and secret agents sent into the South to\
help negroes to flee. One negro woman, Harriet Tubman, "the Moses of her\
people," with headquarters at Philadelphia, is accredited with nineteen\
invasions into slave territory and the emancipation of three hundred\
negroes. Those who worked at this business were in constant peril. One\
underground operator, Calvin Fairbank, spent nearly twenty years in\
prison for aiding fugitives from justice. Yet perils and prisons did not\
stay those determined men and women who, in obedience to their\
consciences, set themselves to this lawless work.\
\
[Illustration: HARRIET BEECHER STOWE]\
\
From thrilling stories of adventure along the underground railways came\
some of the scenes and themes of the novel by Harriet Beecher Stowe,\
"Uncle Tom's Cabin," published two years after the Compromise of 1850.\
Her stirring tale set forth the worst features of slavery in vivid word\
pictures that caught and held the attention of millions of readers.\
Though the book was unfair to the South and was denounced as a hideous\
distortion of the truth, it was quickly dramatized and played in every\
city and town throughout the North. Topsy, Little Eva, Uncle Tom, the\
fleeing slave, Eliza Harris, and the cruel slave driver, Simon Legree,\
with his baying blood hounds, became living specters in many a home that\
sought to bar the door to the "unpleasant and irritating business of\
slavery agitation."\
\
\
THE DRIFT OF EVENTS TOWARD THE IRREPRESSIBLE CONFLICT\
\
=Repeal of the Missouri Compromise.=--To practical men, after all, the\
"rub-a-dub" agitation of a few abolitionists, an occasional riot over\
fugitive slaves, and the vogue of a popular novel seemed of slight or\
transient importance. They could point with satisfaction to the election\
returns of 1852; but their very security was founded upon shifting\
sands. The magnificent triumph of the pro-slavery Democrats in 1852\
brought a turn in affairs that destroyed the foundations under their\
feet. Emboldened by their own strength and the weakness of their\
opponents, they now dared to repeal the Missouri Compromise. The leader\
in this fateful enterprise was Stephen A. Douglas, Senator from\
Illinois, and the occasion for the deed was the demand for the\
organization of territorial government in the regions west of Iowa and\
Missouri.\
\
Douglas, like Clay and Webster before him, was consumed by a strong\
passion for the presidency, and, to reach his goal, it was necessary to\
win the support of the South. This he undoubtedly sought to do when he\
introduced on January 4, 1854, a bill organizing the Nebraska territory\
on the principle of the Compromise of 1850; namely, that the people in\
the territory might themselves decide whether they would have slavery or\
not. Unwittingly the avalanche was started.\
\
After a stormy debate, in which important amendments were forced on\
Douglas, the Kansas-Nebraska Bill became a law on May 30, 1854. The\
measure created two territories, Kansas and Nebraska, and provided that\
they, or territories organized out of them, could come into the union as\
states "with or without slavery as their constitutions may prescribe at\
the time of their admission." Not content with this, the law went on to\
declare the Missouri Compromise null and void as being inconsistent with\
the principle of non-intervention by Congress with slavery in the states\
and territories. Thus by a single blow the very heart of the continent,\
dedicated to freedom by solemn agreement, was thrown open to slavery. A\
desperate struggle between slave owners and the advocates of freedom was\
the outcome in Kansas.\
\
If Douglas fancied that the North would receive the overthrow of the\
Missouri Compromise in the same temper that it greeted Clay's\
settlement, he was rapidly disillusioned. A blast of rage, terrific in\
its fury, swept from Maine to Iowa. Staid old Boston hanged him in\
effigy with an inscription--"Stephen A. Douglas, author of the infamous\
Nebraska bill: the Benedict Arnold of 1854." City after city burned him\
in effigy until, as he himself said, he could travel from the Atlantic\
coast to Chicago in the light of the fires. Thousands of Whigs and\
Free-soil Democrats deserted their parties which had sanctioned or at\
least tolerated the Kansas-Nebraska Bill, declaring that the startling\
measure showed an evident resolve on the part of the planters to rule\
the whole country. A gage of defiance was thrown down to the\
abolitionists. An issue was set even for the moderate and timid who had\
been unmoved by the agitation over slavery in the Far South. That issue\
was whether slavery was to be confined within its existing boundaries or\
be allowed to spread without interference, thereby placing the free\
states in the minority and surrendering the federal government wholly to\
the slave power.\
\
=The Rise of the Republican Party.=--Events of terrible significance,\
swiftly following, drove the country like a ship before a gale straight\
into civil war. The Kansas-Nebraska Bill rent the old parties asunder\
and called into being the Republican party. While that bill was pending\
in Congress, many Northern Whigs and Democrats had come to the\
conclusion that a new party dedicated to freedom in the territories must\
follow the repeal of the Missouri Compromise. Several places claim to be\
the original home of the Republican party; but historians generally\
yield it to Wisconsin. At Ripon in that state, a mass meeting of Whigs\
and Democrats assembled in February, 1854, and resolved to form a new\
party if the Kansas-Nebraska Bill should pass. At a second meeting a\
fusion committee representing Whigs, Free Soilers, and Democrats was\
formed and the name Republican--the name of Jefferson's old party--was\
selected. All over the country similar meetings were held and political\
committees were organized.\
\
When the presidential campaign of 1856 began the Republicans entered the\
contest. After a preliminary conference in Pittsburgh in February, they\
held a convention in Philadelphia at which was drawn up a platform\
opposing the extension of slavery to the territories. John C. Fremont,\
the distinguished explorer, was named for the presidency. The results\
of the election were astounding as compared with the Free-soil failure\
of the preceding election. Prominent men like Longfellow, Washington\
Irving, William Cullen Bryant, Ralph Waldo Emerson, and George William\
Curtis went over to the new party and 1,341,264 votes were rolled up for\
"free labor, free speech, free men, free Kansas, and Fremont."\
Nevertheless the victory of the Democrats was decisive. Their candidate,\
James Buchanan of Pennsylvania, was elected by a majority of 174 to 114\
electoral votes.\
\
[Illustration: SLAVE AND FREE SOIL ON EVE OF CIVIL WAR]\
\
=The Dred Scott Decision (1857).=--In his inaugural, Buchanan vaguely\
hinted that in a forthcoming decision the Supreme Court would settle one\
of the vital questions of the day. This was a reference to the Dred\
Scott case then pending. Scott was a slave who had been taken by his\
master into the upper Louisiana territory, where freedom had been\
established by the Missouri Compromise, and then carried back into his\
old state of Missouri. He brought suit for his liberty on the ground\
that his residence in the free territory made him free. This raised the\
question whether the law of Congress prohibiting slavery north of 36 o\
30' was authorized by the federal Constitution or not. The Court might\
have avoided answering it by saying that even though Scott was free in\
the territory, he became a slave again in Missouri by virtue of the law\
of that state. The Court, however, faced the issue squarely. It held\
that Scott had not been free anywhere and that, besides, the Missouri\
Compromise violated the Constitution and was null and void.\
\
The decision was a triumph for the South. It meant that Congress after\
all had no power to abolish slavery in the territories. Under the decree\
of the highest court in the land, that could be done only by an\
amendment to the Constitution which required a two-thirds vote in\
Congress and the approval of three-fourths of the states. Such an\
amendment was obviously impossible--the Southern states were too\
numerous; but the Republicans were not daunted. "We know," said Lincoln,\
"the Court that made it has often overruled its own decisions and we\
shall do what we can to have it overrule this." Legislatures of Northern\
states passed resolutions condemning the decision and the Republican\
platform of 1860 characterized the dogma that the Constitution carried\
slavery into the territories as "a dangerous political heresy at\
variance with the explicit provisions of that instrument itself ... with\
legislative and judicial precedent ... revolutionary in tendency and\
subversive of the peace and harmony of the country."\
\
=The Panic of 1857.=--In the midst of the acrimonious dispute over the\
Dred Scott decision, came one of the worst business panics which ever\
afflicted the country. In the spring and summer of 1857, fourteen\
railroad corporations, including the Erie, Michigan Central, and the\
Illinois Central, failed to meet their obligations; banks and insurance\
companies, some of them the largest and strongest institutions in the\
North, closed their doors; stocks and bonds came down in a crash on the\
markets; manufacturing was paralyzed; tens of thousands of working\
people were thrown out of employment; "hunger meetings" of idle men were\
held in the cities and banners bearing the inscription, "We want\
bread," were flung out. In New York, working men threatened to invade\
the Council Chamber to demand "work or bread," and the frightened mayor\
called for the police and soldiers. For this distressing state of\
affairs many remedies were offered; none with more zeal and persistence\
than the proposal for a higher tariff to take the place of the law of\
March, 1857, a Democratic measure making drastic reductions in the rates\
of duty. In the manufacturing districts of the North, the panic was\
ascribed to the "Democratic assault on business." So an old issue was\
again vigorously advanced, preparatory to the next presidential\
campaign.\
\
=The Lincoln-Douglas Debates.=--The following year the interest of the\
whole country was drawn to a series of debates held in Illinois by\
Lincoln and Douglas, both candidates for the United States Senate. In\
the course of his campaign Lincoln had uttered his trenchant saying that\
"a house divided against itself cannot stand. I believe this government\
cannot endure permanently half slave and half free." At the same time he\
had accused Douglas, Buchanan, and the Supreme Court of acting in\
concert to make slavery national. This daring statement arrested the\
attention of Douglas, who was making his campaign on the doctrine of\
"squatter sovereignty;" that is, the right of the people of each\
territory "to vote slavery up or down." After a few long-distance shots\
at each other, the candidates agreed to meet face to face and discuss\
the issues of the day. Never had such crowds been seen at political\
meetings in Illinois. Farmers deserted their plows, smiths their forges,\
and housewives their baking to hear "Honest Abe" and "the Little Giant."\
\
The results of the series of debates were momentous. Lincoln clearly\
defined his position. The South, he admitted, was entitled under the\
Constitution to a fair, fugitive slave law. He hoped that there might be\
no new slave states; but he did not see how Congress could exclude the\
people of a territory from admission as a state if they saw fit to adopt\
a constitution legalizing the ownership of slaves. He favored the\
gradual abolition of slavery in the District of Columbia and the total\
exclusion of it from the territories of the United States by act of\
Congress.\
\
Moreover, he drove Douglas into a hole by asking how he squared\
"squatter sovereignty" with the Dred Scott decision; how, in other\
words, the people of a territory could abolish slavery when the Court\
had declared that Congress, the superior power, could not do it under\
the Constitution? To this baffling question Douglas lamely replied that\
the inhabitants of a territory, by "unfriendly legislation," might make\
property in slaves insecure and thus destroy the institution. This\
answer to Lincoln's query alienated many Southern Democrats who believed\
that the Dred Scott decision settled the question of slavery in the\
territories for all time. Douglas won the election to the Senate; but\
Lincoln, lifted into national fame by the debates, beat him in the\
campaign for President two years later.\
\
=John Brown's Raid.=--To the abolitionists the line of argument pursued\
by Lincoln, including his proposal to leave slavery untouched in the\
states where it existed, was wholly unsatisfactory. One of them, a grim\
and resolute man, inflamed by a hatred for slavery in itself, turned\
from agitation to violence. "These men are all talk; what is needed is\
action--action!" So spoke John Brown of New York. During the sanguinary\
struggle in Kansas he hurried to the frontier, gun and dagger in hand,\
to help drive slave owners from the free soil of the West. There he\
committed deeds of such daring and cruelty that he was outlawed and a\
price put upon his head. Still he kept on the path of "action." Aided by\
funds from Northern friends, he gathered a small band of his followers\
around him, saying to them: "If God be for us, who can be against us?"\
He went into Virginia in the autumn of 1859, hoping, as he explained,\
"to effect a mighty conquest even though it be like the last victory of\
Samson." He seized the government armory at Harper's Ferry, declared\
free the slaves whom he found, and called upon them to take up arms in\
defense of their liberty. His was a hope as forlorn as it was desperate.\
Armed forces came down upon him and, after a hard battle, captured him.\
Tried for treason, Brown was condemned to death. The governor of\
Virginia turned a deaf ear to pleas for clemency based on the ground\
that the prisoner was simply a lunatic. "This is a beautiful country,"\
said the stern old Brown glancing upward to the eternal hills on his way\
to the gallows, as calmly as if he were returning home from a long\
journey. "So perish all such enemies of Virginia. All such enemies of\
the Union. All such foes of the human race," solemnly announced the\
executioner as he fulfilled the judgment of the law.\
\
The raid and its grim ending deeply moved the country. Abolitionists\
looked upon Brown as a martyr and tolled funeral bells on the day of his\
execution. Longfellow wrote in his diary: "This will be a great day in\
our history; the date of a new revolution as much needed as the old\
one." Jefferson Davis saw in the affair "the invasion of a state by a\
murderous gang of abolitionists bent on inciting slaves to murder\
helpless women and children"--a crime for which the leader had met a\
felon's death. Lincoln spoke of the raid as absurd, the deed of an\
enthusiast who had brooded over the oppression of a people until he\
fancied himself commissioned by heaven to liberate them--an attempt\
which ended in "little else than his own execution." To Republican\
leaders as a whole, the event was very embarrassing. They were taunted\
by the Democrats with responsibility for the deed. Douglas declared his\
"firm and deliberate conviction that the Harper's Ferry crime was the\
natural, logical, inevitable result of the doctrines and teachings of\
the Republican party." So persistent were such attacks that the\
Republicans felt called upon in 1860 to denounce Brown's raid "as among\
the gravest of crimes."\
\
=The Democrats Divided.=--When the Democratic convention met at\
Charleston in the spring of 1860, a few months after Brown's execution,\
it soon became clear that there was danger ahead. Between the extreme\
slavery advocates of the Far South and the so-called pro-slavery\
Democrats of the Douglas type, there was a chasm which no appeals to\
party loyalty could bridge. As the spokesman of the West, Douglas knew\
that, while the North was not abolitionist, it was passionately set\
against an extension of slavery into the territories by act of Congress;\
that squatter sovereignty was the mildest kind of compromise acceptable\
to the farmers whose votes would determine the fate of the election.\
Southern leaders would not accept his opinion. Yancey, speaking for\
Alabama, refused to palter with any plan not built on the proposition\
that slavery was in itself right. He taunted the Northern Democrats with\
taking the view that slavery was wrong, but that they could not do\
anything about it. That, he said, was the fatal error--the cause of all\
discord, the source of "Black Republicanism," as well as squatter\
sovereignty. The gauntlet was thus thrown down at the feet of the\
Northern delegates: "You must not apologize for slavery; you must\
declare it right; you must advocate its extension." The challenge, so\
bluntly put, was as bluntly answered. "Gentlemen of the South,"\
responded a delegate from Ohio, "you mistake us. You mistake us. We will\
not do it."\
\
For ten days the Charleston convention wrangled over the platform and\
balloted for the nomination of a candidate. Douglas, though in the lead,\
could not get the two-thirds vote required for victory. For more than\
fifty times the roll of the convention was called without a decision.\
Then in sheer desperation the convention adjourned to meet later at\
Baltimore. When the delegates again assembled, their passions ran as\
high as ever. The division into two irreconcilable factions was\
unchanged. Uncompromising delegates from the South withdrew to Richmond,\
nominated John C. Breckinridge of Kentucky for President, and put forth\
a platform asserting the rights of slave owners in the territories and\
the duty of the federal government to protect them. The delegates who\
remained at Baltimore nominated Douglas and endorsed his doctrine of\
squatter sovereignty.\
\
=The Constitutional Union Party.=--While the Democratic party was being\
disrupted, a fragment of the former Whig party, known as the\
Constitutional Unionists, held a convention at Baltimore and selected\
national candidates: John Bell from Tennessee and Edward Everett from\
Massachusetts. A melancholy interest attached to this assembly. It was\
mainly composed of old men whose political views were those of Clay and\
Webster, cherished leaders now dead and gone. In their platform they\
sought to exorcise the evil spirit of partisanship by inviting their\
fellow citizens to "support the Constitution of the country, the union\
of the states, and the enforcement of the laws." The party that\
campaigned on this grand sentiment only drew laughter from the Democrats\
and derision from the Republicans and polled less than one-fourth the\
votes.\
\
=The Republican Convention.=--With the Whigs definitely forced into a\
separate group, the Republican convention at Chicago was fated to be\
sectional in character, although five slave states did send delegates.\
As the Democrats were split, the party that had led a forlorn hope four\
years before was on the high road to success at last. New and powerful\
recruits were found. The advocates of a high protective tariff and the\
friends of free homesteads for farmers and workingmen mingled with\
enthusiastic foes of slavery. While still firm in their opposition to\
slavery in the territories, the Republicans went on record in favor of a\
homestead law granting free lands to settlers and approved customs\
duties designed "to encourage the development of the industrial\
interests of the whole country." The platform was greeted with cheers\
which, according to the stenographic report of the convention, became\
loud and prolonged as the protective tariff and homestead planks were\
read.\
\
Having skillfully drawn a platform to unite the North in opposition to\
slavery and the planting system, the Republicans were also adroit in\
their selection of a candidate. The tariff plank might carry\
Pennsylvania, a Democratic state; but Ohio, Indiana, and Illinois were\
equally essential to success at the polls. The southern counties of\
these states were filled with settlers from Virginia, North Carolina,\
and Kentucky who, even if they had no love for slavery, were no friends\
of abolition. Moreover, remembering the old fight on the United States\
Bank in Andrew Jackson's day, they were suspicious of men from the East.\
Accordingly, they did not favor the candidacy of Seward, the leading\
Republican statesman and "favorite son" of New York.\
\
After much trading and discussing, the convention came to the conclusion\
that Abraham Lincoln of Illinois was the most "available" candidate. He\
was of Southern origin, born in Kentucky in 1809, a fact that told\
heavily in the campaign in the Ohio Valley. He was a man of the soil,\
the son of poor frontier parents, a pioneer who in his youth had labored\
in the fields and forests, celebrated far and wide as "honest Abe, the\
rail-splitter." It was well-known that he disliked slavery, but was no\
abolitionist. He had come dangerously near to Seward's radicalism in his\
"house-divided-against-itself" speech but he had never committed himself\
to the reckless doctrine that there was a "higher law" than the\
Constitution. Slavery in the South he tolerated as a bitter fact;\
slavery in the territories he opposed with all his strength. Of his\
sincerity there could be no doubt. He was a speaker and writer of\
singular power, commanding, by the use of simple and homely language,\
the hearts and minds of those who heard him speak or read his printed\
words. He had gone far enough in his opposition to slavery; but not too\
far. He was the man of the hour! Amid lusty cheers from ten thousand\
throats, Lincoln was nominated for the presidency by the Republicans. In\
the ensuing election, he carried all the free states except New Jersey.\
\
\
=References=\
\
P.E. Chadwick, _Causes of the Civil War_ (American Nation Series).\
\
W.E. Dodd, _Statesmen of the Old South_.\
\
E. Engle, _Southern Sidelights_ (Sympathetic account of the Old South).\
\
A.B. Hart, _Slavery and Abolition_ (American Nation Series).\
\
J.F. Rhodes, _History of the United States_, Vols. I and II.\
\
T.C. Smith, _Parties and Slavery_ (American Nation Series).\
\
\
=Questions=\
\
1. Trace the decline of slavery in the North and explain it.\
\
2. Describe the character of early opposition to slavery.\
\
3. What was the effect of abolition agitation?\
\
4. Why did anti-slavery sentiment practically disappear in the South?\
\
5. On what grounds did Calhoun defend slavery?\
\
6. Explain how slave owners became powerful in politics.\
\
7. Why was it impossible to keep the slavery issue out of national\
politics?\
\
8. Give the leading steps in the long controversy over slavery in the\
territories.\
\
9. State the terms of the Compromise of 1850 and explain its failure.\
\
10. What were the startling events between 1850 and 1860?\
\
11. Account for the rise of the Republican party. What party had used\
the title before?\
\
12. How did the Dred Scott decision become a political issue?\
\
13. What were some of the points brought out in the Lincoln-Douglas\
debates?\
\
14. Describe the party division in 1860.\
\
15. What were the main planks in the Republican platform?\
\
\
=Research Topics=\
\
=The Extension of Cotton Planting.=--Callender, _Economic History of the\
United States_, pp. 760-768.\
\
=Abolition Agitation.=--McMaster, _History of the People of the United\
States_, Vol. VI, pp. 271-298.\
\
=Calhoun's Defense of Slavery.=--Harding, _Select Orations Illustrating\
American History_, pp. 247-257.\
\
=The Compromise of 1850.=--Clay's speech in Harding, _Select Orations_,\
pp. 267-289. The compromise laws in Macdonald, _Documentary Source Book\
of American History_, pp. 383-394. Narrative account in McMaster, Vol.\
VIII, pp. 1-55; Elson, _History of the United States_, pp. 540-548.\
\
=The Repeal of the Missouri Compromise.=--McMaster, Vol. VIII, pp.\
192-231; Elson, pp. 571-582.\
\
=The Dred Scott Case.=--McMaster, Vol. VIII, pp. 278-282. Compare the\
opinion of Taney and the dissent of Curtis in Macdonald, _Documentary\
Source Book_, pp. 405-420; Elson, pp. 595-598.\
\
=The Lincoln-Douglas Debates.=--Analysis of original speeches in\
Harding, _Select Orations_ pp. 309-341; Elson, pp. 598-604.\
\
=Biographical Studies.=--Calhoun, Clay, Webster, A.H. Stephens, Douglas,\
W.H. Seward, William Lloyd Garrison, Wendell Phillips, and Harriet\
Beecher Stowe.\
\
\
\
\
CHAPTER XV\
\
THE CIVIL WAR AND RECONSTRUCTION\
\
\
"The irrepressible conflict is about to be visited upon us through the\
Black Republican nominee and his fanatical, diabolical Republican\
party," ran an appeal to the voters of South Carolina during the\
campaign of 1860. If that calamity comes to pass, responded the governor\
of the state, the answer should be a declaration of independence. In a\
few days the suspense was over. The news of Lincoln's election came\
speeding along the wires. Prepared for the event, the editor of the\
Charleston _Mercury_ unfurled the flag of his state amid wild cheers\
from an excited throng in the streets. Then he seized his pen and wrote:\
"The tea has been thrown overboard; the revolution of 1860 has been\
initiated." The issue was submitted to the voters in the choice of\
delegates to a state convention called to cast off the yoke of the\
Constitution.\
\
\
THE SOUTHERN CONFEDERACY\
\
=Secession.=--As arranged, the convention of South Carolina assembled in\
December and without a dissenting voice passed the ordinance of\
secession withdrawing from the union. Bells were rung exultantly, the\
roar of cannon carried the news to outlying counties, fireworks lighted\
up the heavens, and champagne flowed. The crisis so long expected had\
come at last; even the conservatives who had prayed that they might\
escape the dreadful crash greeted it with a sigh of relief.\
\
[Illustration: THE UNITED STATES IN 1861\
\
The border states (in purple) remained loyal.]\
\
South Carolina now sent forth an appeal to her sister states--states\
that had in Jackson's day repudiated nullification as leading to "the\
dissolution of the union." The answer that came this time was in a\
different vein. A month had hardly elapsed before five other\
states--Florida, Georgia, Alabama, Mississippi, and Louisiana--had\
withdrawn from the union. In February, Texas followed. Virginia,\
hesitating until the bombardment of Fort Sumter forced a conclusion,\
seceded in April; but fifty-five of the one hundred and forty-three\
delegates dissented, foreshadowing the creation of the new state of West\
Virginia which Congress admitted to the union in 1863. In May, North\
Carolina, Arkansas, and Tennessee announced their independence.\
\
=Secession and the Theories of the Union.=--In severing their relations\
with the union, the seceding states denied every point in the Northern\
theory of the Constitution. That theory, as every one knows, was\
carefully formulated by Webster and elaborated by Lincoln. According to\
it, the union was older than the states; it was created before the\
Declaration of Independence for the purpose of common defense. The\
Articles of Confederation did but strengthen this national bond and the\
Constitution sealed it forever. The federal government was not a\
creature of state governments. It was erected by the people and derived\
its powers directly from them. "It is," said Webster, "the people's\
Constitution, the people's government; made for the people; made by the\
people; and answerable to the people. The people of the United States\
have declared that this Constitution shall be the supreme law." When a\
state questions the lawfulness of any act of the federal government, it\
cannot nullify that act or withdraw from the union; it must abide by the\
decision of the Supreme Court of the United States. The union of these\
states is perpetual, ran Lincoln's simple argument in the first\
inaugural; the federal Constitution has no provision for its own\
termination; it can be destroyed only by some action not provided for in\
the instrument itself; even if it is a compact among all the states the\
consent of all must be necessary to its dissolution; therefore no state\
can lawfully get out of the union and acts of violence against the\
United States are insurrectionary or revolutionary. This was the system\
which he believed himself bound to defend by his oath of office\
"registered in heaven."\
\
All this reasoning Southern statesmen utterly rejected. In their opinion\
the thirteen original states won their independence as separate and\
sovereign powers. The treaty of peace with Great Britain named them all\
and acknowledged them "to be free, sovereign, and independent states."\
The Articles of Confederation very explicitly declared that "each state\
retains its sovereignty, freedom, and independence." The Constitution\
was a "league of nations" formed by an alliance of thirteen separate\
powers, each one of which ratified the instrument before it was put into\
effect. They voluntarily entered the union under the Constitution and\
voluntarily they could leave it. Such was the constitutional doctrine of\
Hayne, Calhoun, and Jefferson Davis. In seceding, the Southern states\
had only to follow legal methods, and the transaction would be correct\
in every particular. So conventions were summoned, elections were held,\
and "sovereign assemblies of the people" set aside the Constitution in\
the same manner as it had been ratified nearly four score years before.\
Thus, said the Southern people, the moral judgment was fulfilled and the\
letter of the law carried into effect.\
\
[Illustration: JEFFERSON DAVIS]\
\
=The Formation of the Confederacy.=--Acting on the call of Mississippi,\
a congress of delegates from the seceded states met at Montgomery,\
Alabama, and on February 8, 1861, adopted a temporary plan of union. It\
selected, as provisional president, Jefferson Davis of Mississippi, a\
man well fitted by experience and moderation for leadership, a graduate\
of West Point, who had rendered distinguished service on the field of\
battle in the Mexican War, in public office, and as a member of\
Congress.\
\
In March, a permanent constitution of the Confederate states was\
drafted. It was quickly ratified by the states; elections were held in\
November; and the government under it went into effect the next year.\
This new constitution, in form, was very much like the famous instrument\
drafted at Philadelphia in 1787. It provided for a President, a Senate,\
and a House of Representatives along almost identical lines. In the\
powers conferred upon them, however, there were striking differences.\
The right to appropriate money for internal improvements was expressly\
withheld; bounties were not to be granted from the treasury nor import\
duties so laid as to promote or foster any branch of industry. The\
dignity of the state, if any might be bold enough to question it, was\
safeguarded in the opening line by the declaration that each acted "in\
its sovereign and independent character" in forming the Southern union.\
\
=Financing the Confederacy.=--No government ever set out upon its career\
with more perplexing tasks in front of it. The North had a monetary\
system; the South had to create one. The North had a scheme of taxation\
that produced large revenues from numerous sources; the South had to\
formulate and carry out a financial plan. Like the North, the\
Confederacy expected to secure a large revenue from customs duties,\
easily collected and little felt among the masses. To this expectation\
the blockade of Southern ports inaugurated by Lincoln in April, 1861,\
soon put an end. Following the precedent set by Congress under the\
Articles of Confederation, the Southern Congress resorted to a direct\
property tax apportioned among the states, only to meet the failure that\
might have been foretold.\
\
The Confederacy also sold bonds, the first issue bringing into the\
treasury nearly all the specie available in the Southern banks. This\
specie by unhappy management was early sent abroad to pay for supplies,\
sapping the foundations of a sound currency system. Large amounts of\
bonds were sold overseas, commanding at first better terms than those\
of the North in the markets of London, Paris, and Amsterdam, many an\
English lord and statesman buying with enthusiasm and confidence to\
lament within a few years the proofs of his folly. The difficulties of\
bringing through the blockade any supplies purchased by foreign bond\
issues, however, nullified the effect of foreign credit and forced the\
Confederacy back upon the device of paper money. In all approximately\
one billion dollars streamed from the printing presses, to fall in value\
at an alarming rate, reaching in January, 1863, the astounding figure of\
fifty dollars in paper money for one in gold. Every known device was\
used to prevent its depreciation, without result. To the issues of the\
Confederate Congress were added untold millions poured out by the states\
and by private banks.\
\
=Human and Material Resources.=--When we measure strength for strength\
in those signs of power--men, money, and supplies--it is difficult to\
see how the South was able to embark on secession and war with such\
confidence in the outcome. In the Confederacy at the final reckoning\
there were eleven states in all, to be pitted against twenty-two; a\
population of nine millions, nearly one-half servile, to be pitted\
against twenty-two millions; a land without great industries to produce\
war supplies and without vast capital to furnish war finances, joined in\
battle with a nation already industrial and fortified by property worth\
eleven billion dollars. Even after the Confederate Congress authorized\
conscription in 1862, Southern man power, measured in numbers, was\
wholly inadequate to uphold the independence which had been declared.\
How, therefore, could the Confederacy hope to sustain itself against\
\
such a combination of men, money, and materials as the North could\
marshal?\
\
=Southern Expectations.=--The answer to this question is to be found in\
the ideas that prevailed among Southern leaders. First of all, they\
hoped, in vain, to carry the Confederacy up to the Ohio River; and, with\
the aid of Missouri, to gain possession of the Mississippi Valley, the\
granary of the nation. In the second place, they reckoned upon a large\
and continuous trade with Great Britain--the exchange of cotton for war\
materials. They likewise expected to receive recognition and open aid\
from European powers that looked with satisfaction upon the breakup of\
the great American republic. In the third place, they believed that\
their control over several staples so essential to Northern industry\
would enable them to bring on an industrial crisis in the manufacturing\
states. "I firmly believe," wrote Senator Hammond, of South Carolina, in\
1860, "that the slave-holding South is now the controlling power of the\
world; that no other power would face us in hostility. Cotton, rice,\
tobacco, and naval stores command the world; and we have the sense to\
know it and are sufficiently Teutonic to carry it out successfully. The\
North without us would be a motherless calf, bleating about, and die of\
mange and starvation."\
\
There were other grounds for confidence. Having seized all of the\
federal military and naval supplies in the South, and having left the\
national government weak in armed power during their possession of the\
presidency, Southern leaders looked to a swift war, if it came at all,\
to put the finishing stroke to independence. "The greasy mechanics of\
the North," it was repeatedly said, "will not fight." As to disparity in\
numbers they drew historic parallels. "Our fathers, a mere handful,\
overcame the enormous power of Great Britain," a saying of ex-President\
Tyler, ran current to reassure the doubtful. Finally, and this point\
cannot be too strongly emphasized, the South expected to see a weakened\
and divided North. It knew that the abolitionists and the Southern\
sympathizers were ready to let the Confederate states go in peace; that\
Lincoln represented only a little more than one-third the voters of the\
country; and that the vote for Douglas, Bell, and Breckinridge meant a\
decided opposition to the Republicans and their policies.\
\
=Efforts at Compromise.=--Republican leaders, on reviewing the same\
facts, were themselves uncertain as to the outcome of a civil war and\
made many efforts to avoid a crisis. Thurlow Weed, an Albany journalist\
and politician who had done much to carry New York for Lincoln, proposed\
a plan for extending the Missouri Compromise line to the Pacific.\
Jefferson Davis, warning his followers that a war if it came would be\
terrible, was prepared to accept the offer; but Lincoln, remembering his\
campaign pledges, stood firm as a rock against it. His followers in\
Congress took the same position with regard to a similar settlement\
suggested by Senator Crittenden of Kentucky.\
\
Though unwilling to surrender his solemn promises respecting slavery in\
the territories, Lincoln was prepared to give to Southern leaders a\
strong guarantee that his administration would not interfere directly or\
indirectly with slavery in the states. Anxious to reassure the South on\
this point, the Republicans in Congress proposed to write into the\
Constitution a declaration that no amendment should ever be made\
authorizing the abolition of or interference with slavery in any state.\
The resolution, duly passed, was sent forth on March 4, 1861, with the\
approval of Lincoln; it was actually ratified by three states before the\
storm of war destroyed it. By the irony of fate the thirteenth amendment\
was to abolish, not guarantee, slavery.\
\
\
THE WAR MEASURES OF THE FEDERAL GOVERNMENT\
\
=Raising the Armies.=--The crisis at Fort Sumter, on April 12-14, 1861,\
forced the President and Congress to turn from negotiations to problems\
of warfare. Little did they realize the magnitude of the task before\
them. Lincoln's first call for volunteers, issued on April 15, 1861,\
limited the number to 75,000, put their term of service at three months,\
and prescribed their duty as the enforcement of the law against\
combinations too powerful to be overcome by ordinary judicial process.\
Disillusionment swiftly followed. The terrible defeat of the Federals at\
Bull Run on July 21 revealed the serious character of the task before\
them; and by a series of measures Congress put the entire man power of\
the country at the President's command. Under these acts, he issued new\
calls for volunteers. Early in August, 1862, he ordered a draft of\
militiamen numbering 300,000 for nine months' service. The results were\
disappointing--ominous--for only about 87,000 soldiers were added to the\
army. Something more drastic was clearly necessary.\
\
In March, 1863, Lincoln signed the inevitable draft law; it enrolled in\
the national forces liable to military duty all able-bodied male\
citizens and persons of foreign birth who had declared their intention\
to become citizens, between the ages of twenty and forty-five\
years--with exemptions on grounds of physical weakness and dependency.\
From the men enrolled were drawn by lot those destined to active\
service. Unhappily the measure struck a mortal blow at the principle of\
universal liability by excusing any person who found a substitute for\
himself or paid into the war office a sum, not exceeding three hundred\
dollars, to be fixed by general order. This provision, so crass and so\
obviously favoring the well-to-do, sowed seeds of bitterness which\
sprang up a hundredfold in the North.\
\
[Illustration: THE DRAFT RIOTS IN NEW YORK CITY]\
\
The beginning of the drawings under the draft act in New York City, on\
Monday, July 13, 1863, was the signal for four days of rioting. In the\
course of this uprising, draft headquarters were destroyed; the office\
of the _Tribune_ was gutted; negroes were seized, hanged, and shot; the\
homes of obnoxious Unionists were burned down; the residence of the\
mayor of the city was attacked; and regular battles were fought in the\
streets between the rioters and the police. Business stopped and a large\
part of the city passed absolutely into the control of the mob. Not\
until late the following Wednesday did enough troops arrive to restore\
order and enable the residents of the city to resume their daily\
activities. At least a thousand people had been killed or wounded and\
more than a million dollars' worth of damage done to property. The draft\
temporarily interrupted by this outbreak was then resumed and carried\
out without further trouble.\
\
The results of the draft were in the end distinctly disappointing to the\
government. The exemptions were numerous and the number who preferred\
and were able to pay $300 rather than serve exceeded all expectations.\
Volunteering, it is true, was stimulated, but even that resource could\
hardly keep the thinning ranks of the army filled. With reluctance\
Congress struck out the $300 exemption clause, but still favored the\
well-to-do by allowing them to hire substitutes if they could find them.\
With all this power in its hands the administration was able by January,\
1865, to construct a union army that outnumbered the Confederates two to\
one.\
\
=War Finance.=--In the financial sphere the North faced immense\
difficulties. The surplus in the treasury had been dissipated by 1861\
and the tariff of 1857 had failed to produce an income sufficient to\
meet the ordinary expenses of the government. Confronted by military and\
naval expenditures of appalling magnitude, rising from $35,000,000 in\
the first year of the war to $1,153,000,000 in the last year, the\
administration had to tap every available source of income. The duties\
on imports were increased, not once but many times, producing huge\
revenues and also meeting the most extravagant demands of the\
manufacturers for protection. Direct taxes were imposed on the states\
according to their respective populations, but the returns were\
meager--all out of proportion to the irritation involved. Stamp taxes\
and taxes on luxuries, occupations, and the earnings of corporations\
were laid with a weight that, in ordinary times, would have drawn forth\
opposition of ominous strength. The whole gamut of taxation was run.\
Even a tax on incomes and gains by the year, the first in the history of\
the federal government, was included in the long list.\
\
Revenues were supplemented by bond issues, mounting in size and interest\
rate, until in October, at the end of the war, the debt stood at\
$2,208,000,000. The total cost of the war was many times the money value\
of all the slaves in the Southern states. To the debt must be added\
nearly half a billion dollars in "greenbacks"--paper money issued by\
Congress in desperation as bond sales and revenues from taxes failed to\
meet the rising expenditures. This currency issued at par on\
questionable warrant from the Constitution, like all such paper, quickly\
began to decline until in the worst fortunes of 1864 one dollar in gold\
was worth nearly three in greenbacks.\
\
=The Blockade of Southern Ports.=--Four days after his call for\
volunteers, April 19, 1861, President Lincoln issued a proclamation\
blockading the ports of the Southern Confederacy. Later the blockade was\
extended to Virginia and North Carolina, as they withdrew from the\
union. Vessels attempting to enter or leave these ports, if they\
disregarded the warnings of a blockading ship, were to be captured and\
brought as prizes to the nearest convenient port. To make the order\
effective, immediate steps were taken to increase the naval forces,\
depleted by neglect, until the entire coast line was patrolled with such\
a number of ships that it was a rare captain who ventured to run the\
gantlet. The collision between the _Merrimac_ and the _Monitor_ in\
March, 1862, sealed the fate of the Confederacy. The exploits of the\
union navy are recorded in the falling export of cotton: $202,000,000 in\
1860; $42,000,000 in 1861; and $4,000,000 in 1862.\
\
The deadly effect of this paralysis of trade upon Southern war power may\
be readily imagined. Foreign loans, payable in cotton, could be\
negotiated but not paid off. Supplies could be purchased on credit but\
not brought through the drag net. With extreme difficulty could the\
Confederate government secure even paper for the issue of money and\
bonds. Publishers, in despair at the loss of supplies, were finally\
driven to the use of brown wrapping paper and wall paper. As the\
railways and rolling stock wore out, it became impossible to renew them\
from England or France. Unable to export their cotton, planters on the\
seaboard burned it in what were called "fires of patriotism." In their\
lurid light the fatal weakness of Southern economy stood revealed.\
\
[Illustration: A BLOCKADE RUNNER]\
\
=Diplomacy.=--The war had not advanced far before the federal government\
became involved in many perplexing problems of diplomacy in Europe. The\
Confederacy early turned to England and France for financial aid and for\
recognition as an independent power. Davis believed that the industrial\
crisis created by the cotton blockade would in time literally compel\
Europe to intervene in order to get this essential staple. The crisis\
came as he expected but not the result. Thousands of English textile\
workers were thrown out of employment; and yet, while on the point of\
starvation, they adopted resolutions favoring the North instead of\
petitioning their government to aid the South by breaking the blockade.\
\
With the ruling classes it was far otherwise. Napoleon III, the Emperor\
of the French, was eager to help in disrupting the American republic; if\
he could have won England's support, he would have carried out his\
designs. As it turned out he found plenty of sympathy across the Channel\
but not open and official cooperation. According to the eminent\
historian, Rhodes, "four-fifths of the British House of Lords and most\
members of the House of Commons were favorable to the Confederacy and\
anxious for its triumph." Late in 1862 the British ministers, thus\
sustained, were on the point of recognizing the independence of the\
Confederacy. Had it not been for their extreme caution, for the constant\
and harassing criticism by English friends of the United States--like\
John Bright--and for the victories of Vicksburg and Gettysburg, both\
\
England and France would have doubtless declared the Confederacy to be\
one of the independent powers of the earth.\
\
[Illustration: JOHN BRIGHT]\
\
While stopping short of recognizing its independence, England and France\
took several steps that were in favor of the South. In proclaiming\
neutrality, they early accepted the Confederates as "belligerents" and\
accorded them the rights of people at war--a measure which aroused anger\
in the North at first but was later admitted to be sound. Otherwise\
Confederates taken in battle would have been regarded as "rebels" or\
"traitors" to be hanged or shot. Napoleon III proposed to Russia in 1861\
a coalition of powers against the North, only to meet a firm refusal.\
The next year he suggested intervention to Great Britain, encountering\
this time a conditional rejection of his plans. In 1863, not daunted by\
rebuffs, he offered his services to Lincoln as a mediator, receiving in\
reply a polite letter declining his proposal and a sharp resolution from\
Congress suggesting that he attend to his own affairs.\
\
In both England and France the governments pursued a policy of\
friendliness to the Confederate agents. The British ministry, with\
indifference if not connivance, permitted rams and ships to be built in\
British docks and allowed them to escape to play havoc under the\
Confederate flag with American commerce. One of them, the _Alabama_,\
built in Liverpool by a British firm and paid for by bonds sold in\
England, ran an extraordinary career and threatened to break the\
blockade. The course followed by the British government, against the\
protests of the American minister in London, was later regretted. By an\
award of a tribunal of arbitration at Geneva in 1872, Great Britain was\
required to pay the huge sum of $15,500,000 to cover the damages wrought\
by Confederate cruisers fitted out in England.\
\
[Illustration: WILLIAM H. SEWARD]\
\
In all fairness it should be said that the conduct of the North\
contributed to the irritation between the two countries. Seward, the\
Secretary of State, was vindictive in dealing with Great Britain; had it\
not been for the moderation of Lincoln, he would have pursued a course\
verging in the direction of open war. The New York and Boston papers\
were severe in their attacks on England. Words were, on one occasion at\
least, accompanied by an act savoring of open hostility. In November,\
1861, Captain Wilkes, commanding a union vessel, overhauled the British\
steamer _Trent_, and carried off by force two Confederate agents, Mason\
and Slidell, sent by President Davis to represent the Confederacy at\
London and Paris respectively. This was a clear violation of the right\
of merchant vessels to be immune from search and impressment; and, in\
answer to the demand of Great Britain for the release of the two men,\
the United States conceded that it was in the wrong. It surrendered the\
two Confederate agents to a British vessel for safe conduct abroad, and\
made appropriate apologies.\
\
=Emancipation.=--Among the extreme war measures adopted by the Northern\
government must be counted the emancipation of the slaves in the states\
in arms against the union. This step was early and repeatedly suggested\
to Lincoln by the abolitionists; but was steadily put aside. He knew\
that the abolitionists were a mere handful, that emancipation might\
drive the border states into secession, and that the Northern soldiers\
had enlisted to save the union. Moreover, he had before him a solemn\
resolution passed by Congress on July 22, 1861, declaring the sole\
purpose of the war to be the salvation of the union and disavowing any\
intention of interfering with slavery.\
\
The federal government, though pledged to the preservation of slavery,\
soon found itself beaten back upon its course and out upon a new tack.\
Before a year had elapsed, namely on April 10, 1862, Congress resolved\
that financial aid should be given to any state that might adopt gradual\
emancipation. Six days later it abolished slavery in the District of\
Columbia. Two short months elapsed. On June 19, 1862, it swept slavery\
forever from the territories of the United States. Chief Justice Taney\
still lived, the Dred Scott decision stood as written in the book, but\
the Constitution had been re-read in the light of the Civil War. The\
drift of public sentiment in the North was being revealed.\
\
While these measures were pending in Congress, Lincoln was slowly making\
up his mind. By July of that year he had come to his great decision.\
Near the end of that month he read to his cabinet the draft of a\
proclamation of emancipation; but he laid it aside until a military\
achievement would make it something more than an idle gesture. In\
September, the severe check administered to Lee at Antietam seemed to\
offer the golden opportunity. On the 22d, the immortal document was\
given to the world announcing that, unless the states in arms returned\
to the union by January 1, 1863, the fatal blow at their "peculiar\
institution" would be delivered. Southern leaders treated it with slight\
regard, and so on the date set the promise was fulfilled. The\
proclamation was issued as a war measure, adopted by the President as\
commander-in-chief of the armed forces, on grounds of military\
necessity. It did not abolish slavery. It simply emancipated slaves in\
places then in arms against federal authority. Everywhere else slavery,\
as far as the Proclamation was concerned, remained lawful.\
\
[Illustration: ABRAHAM LINCOLN]\
\
To seal forever the proclamation of emancipation, and to extend freedom\
to the whole country, Congress, in January, 1865, on the urgent\
recommendation of Lincoln, transmitted to the states the thirteenth\
amendment, abolishing slavery throughout the United States. By the end\
of 1865 the amendment was ratified. The house was not divided against\
itself; it did not fall; it was all free.\
\
=The Restraint of Civil Liberty.=--As in all great wars, particularly\
those in the nature of a civil strife, it was found necessary to use\
strong measures to sustain opinion favorable to the administration's\
military policies and to frustrate the designs of those who sought to\
hamper its action. Within two weeks of his first call for volunteers,\
Lincoln empowered General Scott to suspend the writ of _habeas corpus_\
along the line of march between Philadelphia and Washington and thus to\
arrest and hold without interference from civil courts any one whom he\
deemed a menace to the union. At a later date the area thus ruled by\
military officers was extended by executive proclamation. By an act of\
March 3, 1863, Congress, desiring to lay all doubts about the\
President's power, authorized him to suspend the writ throughout the\
United States or in any part thereof. It also freed military officers\
from the necessity of surrendering to civil courts persons arrested\
under their orders, or even making answers to writs issued from such\
courts. In the autumn of that year the President, acting under the terms\
of this law, declared this ancient and honorable instrument for the\
protection of civil liberties, the _habeas corpus_, suspended throughout\
the length and breadth of the land. The power of the government was also\
strengthened by an act defining and punishing certain conspiracies,\
passed on July 31, 1861--a measure which imposed heavy penalties on\
those who by force, intimidation, or threat interfered with the\
execution of the law.\
\
Thus doubly armed, the military authorities spared no one suspected of\
active sympathy with the Southern cause. Editors were arrested and\
imprisoned, their papers suspended, and their newsboys locked up. Those\
who organized "peace meetings" soon found themselves in the toils of the\
law. Members of the Maryland legislature, the mayor of Baltimore, and\
local editors suspected of entertaining secessionist opinions, were\
imprisoned on military orders although charged with no offense, and were\
denied the privilege of examination before a civil magistrate. A Vermont\
farmer, too outspoken in his criticism of the government, found himself\
behind the bars until the government, in its good pleasure, saw fit to\
release him. These measures were not confined to the theater of war nor\
to the border states where the spirit of secession was strong enough to\
endanger the cause of union. They were applied all through the Northern\
states up to the very boundaries of Canada. Zeal for the national cause,\
too often supplemented by a zeal for persecution, spread terror among\
those who wavered in the singleness of their devotion to the union.\
\
These drastic operations on the part of military authorities, so foreign\
to the normal course of civilized life, naturally aroused intense and\
bitter hostility. Meetings of protest were held throughout the country.\
Thirty-six members of the House of Representatives sought to put on\
record their condemnation of the suspension of the _habeas corpus_ act,\
only to meet a firm denial by the supporters of the act. Chief Justice\
Taney, before whom the case of a man arrested under the President's\
military authority was brought, emphatically declared, in a long and\
learned opinion bristling with historical examples, that the President\
had no power to suspend the writ of _habeas corpus_. In Congress and\
out, Democrats, abolitionists, and champions of civil liberty denounced\
Lincoln and his Cabinet in unsparing terms. Vallandigham, a Democratic\
leader of Ohio, afterward banished to the South for his opposition to\
the war, constantly applied to Lincoln the epithet of "Caesar." Wendell\
Phillips saw in him "a more unlimited despot than the world knows this\
side of China."\
\
Sensitive to such stinging thrusts and no friend of wanton persecution,\
Lincoln attempted to mitigate the rigors of the law by paroling many\
political prisoners. The general policy, however, he defended in homely\
language, very different in tone and meaning from the involved reasoning\
of the lawyers. "Must I shoot a simple-minded soldier boy who deserts,\
while I must not touch a hair of the wily agitator who induces him to\
desert?" he asked in a quiet way of some spokesmen for those who\
protested against arresting people for "talking against the war." This\
summed up his philosophy. He was engaged in a war to save the union, and\
all measures necessary and proper to accomplish that purpose were\
warranted by the Constitution which he had sworn to uphold.\
\
=Military Strategy--North and South.=--The broad outlines of military\
strategy followed by the commanders of the opposing forces are clear\
even to the layman who cannot be expected to master the details of a\
campaign or, for that matter, the maneuvers of a single great battle.\
The problem for the South was one of defense mainly, though even for\
defense swift and paralyzing strokes at the North were later deemed\
imperative measures. The problem of the North was, to put it baldly, one\
of invasion and conquest. Southern territory had to be invaded and\
Southern armies beaten on their own ground or worn down to exhaustion\
there.\
\
In the execution of this undertaking, geography, as usual, played a\
significant part in the disposition of forces. The Appalachian ranges,\
stretching through the Confederacy to Northern Alabama, divided the\
campaigns into Eastern and Western enterprises. Both were of signal\
importance. Victory in the East promised the capture of the Confederate\
capital of Richmond, a stroke of moral worth, hardly to be\
overestimated. Victory in the West meant severing the Confederacy and\
opening the Mississippi Valley down to the Gulf.\
\
As it turned out, the Western forces accomplished their task first,\
vindicating the military powers of union soldiers and shaking the\
confidence of opposing commanders. In February, 1862, Grant captured\
Fort Donelson on the Tennessee River, rallied wavering unionists in\
Kentucky, forced the evacuation of Nashville, and opened the way for two\
hundred miles into the Confederacy. At Shiloh, Murfreesboro, Vicksburg,\
Chickamauga, Chattanooga, desperate fighting followed and, in spite of\
varying fortunes, it resulted in the discomfiture and retirement of\
Confederate forces to the Southeast into Georgia. By the middle of 1863,\
the Mississippi Valley was open to the Gulf, the initiative taken out of\
the hands of Southern commanders in the West, and the way prepared for\
Sherman's final stroke--the march from Atlanta to the sea--a maneuver\
executed with needless severity in the autumn of 1864.\
\
[Illustration: GENERAL ULYSSES S. GRANT]\
\
[Illustration: GENERAL ROBERT E. LEE]\
\
For the almost unbroken succession of achievements in the West by\
Generals Grant, Sherman, Thomas, and Hooker against Albert Sidney\
Johnston, Bragg, Pemberton, and Hood, the union forces in the East\
offered at first an almost equally unbroken series of misfortunes and\
disasters. Far from capturing Richmond, they had been thrown on the\
defensive. General after general--McClellan, Pope, Burnside, Hooker, and\
Meade--was tried and found wanting. None of them could administer a\
crushing defeat to the Confederate troops and more than once the union\
soldiers were beaten in a fair battle. They did succeed, however, in\
delivering a severe check to advancing Confederates under General Robert\
E. Lee, first at Antietam in September, 1862, and then at Gettysburg in\
July, 1863--checks reckoned as victories though in each instance the\
Confederates escaped without demoralization. Not until the beginning of\
the next year, when General Grant, supplied with almost unlimited men\
and munitions, began his irresistible hammering at Lee's army, did the\
final phase of the war commence. The pitiless drive told at last.\
General Lee, on April 9, 1865, seeing the futility of further conflict,\
surrendered an army still capable of hard fighting, at Appomattox, not\
far from the capital of the Confederacy.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
THE FEDERAL MILITARY HOSPITAL AT GETTYSBURG]\
\
=Abraham Lincoln.=--The services of Lincoln to the cause of union defy\
description. A judicial scrutiny of the war reveals his thought and\
planning in every part of the varied activity that finally crowned\
Northern arms with victory. Is it in the field of diplomacy? Does\
Seward, the Secretary of State, propose harsh and caustic measures\
likely to draw England's sword into the scale? Lincoln counsels\
moderation. He takes the irritating message and with his own hand\
strikes out, erases, tones down, and interlines, exchanging for words\
that sting and burn the language of prudence and caution. Is it a matter\
of compromise with the South, so often proposed by men on both sides\
sick of carnage? Lincoln is always ready to listen and turns away only\
when he is invited to surrender principles essential to the safety of\
the union. Is it high strategy of war, a question of the general best\
fitted to win Gettysburg--Hooker, Sedgwick, or Meade? Lincoln goes in\
person to the War Department in the dead of night to take counsel with\
his Secretary and to make the fateful choice.\
\
Is it a complaint from a citizen, deprived, as he believes, of his civil\
liberties unjustly or in violation of the Constitution? Lincoln is ready\
to hear it and anxious to afford relief, if warrant can be found for it.\
Is a mother begging for the life of a son sentenced to be shot as a\
deserter? Lincoln hears her petition, and grants it even against the\
protests made by his generals in the name of military discipline. Do\
politicians sow dissensions in the army and among civilians? Lincoln\
grandly waves aside their petty personalities and invites them to think\
of the greater cause. Is it a question of securing votes to ratify the\
thirteenth amendment abolishing slavery? Lincoln thinks it not beneath\
his dignity to traffic and huckster with politicians over the trifling\
jobs asked in return by the members who hold out against him. Does a New\
York newspaper call him an ignorant Western boor? Lincoln's reply is a\
letter to a mother who has given her all--her sons on the field of\
battle--and an address at Gettysburg, both of which will live as long as\
the tongue in which they were written. These are tributes not only to\
his mastery of the English language but also to his mastery of all those\
sentiments of sweetness and strength which are the finest flowers of\
culture.\
\
Throughout the entire span of service, however, Lincoln was beset by\
merciless critics. The fiery apostles of abolition accused him of\
cowardice when he delayed the bold stroke at slavery. Anti-war Democrats\
lashed out at every step he took. Even in his own party he found no\
peace. Charles Sumner complained: "Our President is now dictator,\
_imperator_--whichever you like; but how vain to have the power of a\
god and not to use it godlike." Leaders among the Republicans sought to\
put him aside in 1864 and place Chase in his chair. "I hope we may never\
have a worse man," was Lincoln's quiet answer.\
\
Wide were the dissensions in the North during that year and the\
Republicans, while selecting Lincoln as their candidate again, cast off\
their old name and chose the simple title of the "Union party."\
Moreover, they selected a Southern man, Andrew Johnson, of Tennessee, to\
be associated with him as candidate for Vice President. This combination\
the Northern Democrats boldly confronted with a platform declaring that\
"after four years of failure to restore the union by the experiment of\
war, during which, under the pretence of military necessity or war power\
higher than the Constitution, the Constitution itself has been\
disregarded in every part and public liberty and private right alike\
trodden down ... justice, humanity, liberty, and public welfare demand\
that immediate efforts be made for a cessation of hostilities, to the\
end that peace may be restored on the basis of the federal union of the\
states." It is true that the Democratic candidate, General McClellan,\
sought to break the yoke imposed upon him by the platform, saying that\
he could not look his old comrades in the face and pronounce their\
efforts vain; but the party call to the nation to repudiate Lincoln and\
his works had gone forth. The response came, giving Lincoln 2,200,000\
votes against 1,800,000 for his opponent. The bitter things said about\
him during the campaign, he forgot and forgave. When in April, 1865, he\
was struck down by the assassin's hand, he above all others in\
Washington was planning measures of moderation and healing.\
\
\
THE RESULTS OF THE CIVIL WAR\
\
There is a strong and natural tendency on the part of writers to stress\
the dramatic and heroic aspects of war; but the long judgment of history\
requires us to include all other significant phases as well. Like every\
great armed conflict, the Civil War outran the purposes of those who\
took part in it. Waged over the nature of the union, it made a\
revolution in the union, changing public policies and constitutional\
principles and giving a new direction to agriculture and industry.\
\
=The Supremacy of the Union.=--First and foremost, the war settled for\
all time the long dispute as to the nature of the federal system. The\
doctrine of state sovereignty was laid to rest. Men might still speak of\
the rights of states and think of their commonwealths with affection,\
but nullification and secession were destroyed. The nation was supreme.\
\
=The Destruction of the Slave Power.=--Next to the vindication of\
national supremacy was the destruction of the planting aristocracy of\
the South--that great power which had furnished leadership of undoubted\
ability and had so long contested with the industrial and commercial\
interests of the North. The first paralyzing blow at the planters was\
struck by the abolition of slavery. The second and third came with the\
fourteenth (1868) and fifteenth (1870) amendments, giving the ballot to\
freedmen and excluding from public office the Confederate\
leaders--driving from the work of reconstruction the finest talents of\
the South. As if to add bitterness to gall and wormwood, the fourteenth\
amendment forbade the United States or any state to pay any debts\
incurred in aid of the Confederacy or in the emancipation of the\
slaves--plunging into utter bankruptcy the Southern financiers who had\
stripped their section of capital to support their cause. So the\
Southern planters found themselves excluded from public office and ruled\
over by their former bondmen under the tutelage of Republican leaders.\
Their labor system was wrecked and their money and bonds were as\
worthless as waste paper. The South was subject to the North. That which\
neither the Federalists nor the Whigs had been able to accomplish in the\
realm of statecraft was accomplished on the field of battle.\
\
\
=The Triumph of Industry.=--The wreck of the planting system was\
accompanied by a mighty upswing of Northern industry which made the old\
Whigs of Massachusetts and Pennsylvania stare in wonderment. The demands\
of the federal government for manufactured goods at unrestricted prices\
gave a stimulus to business which more than replaced the lost markets of\
the South. Between 1860 and 1870 the number of manufacturing\
establishments increased 79.6 per cent as against 14.2 for the previous\
decade; while the number of persons employed almost doubled. There was\
no doubt about the future of American industry.\
\
=The Victory for the Protective Tariff.=--Moreover, it was henceforth to\
be well protected. For many years before the war the friends of\
protection had been on the defensive. The tariff act of 1857 imposed\
duties so low as to presage a tariff for revenue only. The war changed\
all that. The extraordinary military expenditures, requiring heavy taxes\
on all sources, justified tariffs so high that a follower of Clay or\
Webster might well have gasped with astonishment. After the war was over\
the debt remained and both interest and principal had to be paid.\
Protective arguments based on economic reasoning were supported by a\
plain necessity for revenue which admitted no dispute.\
\
=A Liberal Immigration Policy.=--Linked with industry was the labor\
supply. The problem of manning industries became a pressing matter, and\
Republican leaders grappled with it. In the platform of the Union party\
adopted in 1864 it was declared "that foreign immigration, which in the\
past has added so much to the wealth, the development of resources, and\
the increase of power to this nation--the asylum of the oppressed of all\
nations--should be fostered and encouraged by a liberal and just\
policy." In that very year Congress, recognizing the importance of the\
problem, passed a measure of high significance, creating a bureau of\
immigration, and authorizing a modified form of indentured labor, by\
making it legal for immigrants to pledge their wages in advance to pay\
their passage over. Though the bill was soon repealed, the practice\
authorized by it was long continued. The cheapness of the passage\
shortened the term of service; but the principle was older than the\
days of William Penn.\
\
=The Homestead Act of 1862.=--In the immigration measure guaranteeing a\
continuous and adequate labor supply, the manufacturers saw an offset to\
the Homestead Act of 1862 granting free lands to settlers. The Homestead\
law they had resisted in a long and bitter congressional battle.\
Naturally, they had not taken kindly to a scheme which lured men away\
from the factories or enabled them to make unlimited demands for higher\
wages as the price of remaining. Southern planters likewise had feared\
free homesteads for the very good reason that they only promised to add\
to the overbalancing power of the North.\
\
In spite of the opposition, supporters of a liberal land policy made\
steady gains. Free-soil Democrats,--Jacksonian farmers and\
mechanics,--labor reformers, and political leaders, like Stephen A.\
Douglas of Illinois and Andrew Johnson of Tennessee, kept up the\
agitation in season and out. More than once were they able to force a\
homestead bill through the House of Representatives only to have it\
blocked in the Senate where Southern interests were intrenched. Then,\
after the Senate was won over, a Democratic President, James Buchanan,\
vetoed the bill. Still the issue lived. The Republicans, strong among\
the farmers of the Northwest, favored it from the beginning and pressed\
it upon the attention of the country. Finally the manufacturers yielded;\
they received their compensation in the contract labor law. In 1862\
Congress provided for the free distribution of land in 160-acre lots\
among men and women of strong arms and willing hearts ready to build\
their serried lines of homesteads to the Rockies and beyond.\
\
=Internal Improvements.=--If farmers and manufacturers were early\
divided on the matter of free homesteads, the same could hardly be said\
of internal improvements. The Western tiller of the soil was as eager\
for some easy way of sending his produce to market as the manufacturer\
was for the same means to transport his goods to the consumer on the\
farm. While the Confederate leaders were writing into their\
constitution a clause forbidding all appropriations for internal\
improvements, the Republican leaders at Washington were planning such\
expenditures from the treasury in the form of public land grants to\
railways as would have dazed the authors of the national road bill half\
a century earlier.\
\
=Sound Finance--National Banking.=--From Hamilton's day to Lincoln's,\
business men in the East had contended for a sound system of national\
currency. The experience of the states with paper money, painfully\
impressive in the years before the framing of the Constitution, had been\
convincing to those who understood the economy of business. The\
Constitution, as we have seen, bore the signs of this experience. States\
were forbidden to emit bills of credit: paper money, in short. This\
provision stood clear in the document; but judicial ingenuity had\
circumvented it in the age of Jacksonian Democracy. The states had\
enacted and the Supreme Court, after the death of John Marshall, had\
sustained laws chartering banking companies and authorizing them to\
issue paper money. So the country was beset by the old curse, the banks\
of Western and Southern states issuing reams of paper notes to help\
borrowers pay their debts.\
\
In dealing with war finances, the Republicans attacked this ancient\
evil. By act of Congress in 1864, they authorized a series of national\
banks founded on the credit of government bonds and empowered to issue\
notes. The next year they stopped all bank paper sent forth under the\
authority of the states by means of a prohibitive tax. In this way, by\
two measures Congress restored federal control over the monetary system\
although it did not reestablish the United States Bank so hated by\
Jacksonian Democracy.\
\
=Destruction of States' Rights by Fourteenth Amendment.=--These acts and\
others not cited here were measures of centralization and consolidation\
at the expense of the powers and dignity of the states. They were all of\
high import, but the crowning act of nationalism was the fourteenth\
amendment which, among other things, forbade states to "deprive any\
person of life, liberty or property without due process of law." The\
immediate occasion, though not the actual cause of this provision, was\
the need for protecting the rights of freedmen against hostile\
legislatures in the South. The result of the amendment, as was\
prophesied in protests loud and long from every quarter of the\
Democratic party, was the subjection of every act of state, municipal,\
and county authorities to possible annulment by the Supreme Court at\
Washington. The expected happened.\
\
Few negroes ever brought cases under the fourteenth amendment to the\
attention of the courts; but thousands of state laws, municipal\
ordinances, and acts of local authorities were set aside as null and\
void under it. Laws of states regulating railway rates, fixing hours of\
labor in bakeshops, and taxing corporations were in due time to be\
annulled as conflicting with an amendment erroneously supposed to be\
designed solely for the protection of negroes. As centralized power over\
tariffs, railways, public lands, and other national concerns went to\
Congress, so centralized power over the acts of state and local\
authorities involving an infringement of personal and property rights\
was conferred on the federal judiciary, the apex of which was the\
Supreme Court at Washington. Thus the old federation of "independent\
states," all equal in rights and dignity, each wearing the "jewel of\
sovereignty" so celebrated in Southern oratory, had gone the way of all\
flesh under the withering blasts of Civil War.\
\
\
RECONSTRUCTION IN THE SOUTH\
\
=Theories about the Position of the Seceded States.=--On the morning of\
April 9, 1865, when General Lee surrendered his army to General Grant,\
eleven states stood in a peculiar relation to the union now declared\
perpetual. Lawyers and political philosophers were much perturbed and\
had been for some time as to what should be done with the members of the\
former Confederacy. Radical Republicans held that they were "conquered\
provinces" at the mercy of Congress, to be governed under such laws as\
it saw fit to enact and until in its wisdom it decided to readmit any or\
all of them to the union. Men of more conservative views held that, as\
the war had been waged by the North on the theory that no state could\
secede from the union, the Confederate states had merely attempted to\
withdraw and had failed. The corollary of this latter line of argument\
was simple: "The Southern states are still in the union and it is the\
duty of the President, as commander-in-chief, to remove the federal\
troops as soon as order is restored and the state governments ready to\
function once more as usual."\
\
=Lincoln's Proposal.=--Some such simple and conservative form of\
reconstruction had been suggested by Lincoln in a proclamation of\
December 8, 1863. He proposed pardon and a restoration of property,\
except in slaves, to nearly all who had "directly or by implication\
participated in the existing rebellion," on condition that they take an\
oath of loyalty to the union. He then announced that when, in any of the\
states named, a body of voters, qualified under the law as it stood\
before secession and equal in number to one-tenth the votes cast in\
1860, took the oath of allegiance, they should be permitted to\
reestablish a state government. Such a government, he added, should be\
recognized as a lawful authority and entitled to protection under the\
federal Constitution. With reference to the status of the former slaves\
Lincoln made it clear that, while their freedom must be recognized, he\
would not object to any legislation "which may yet be consistent as a\
temporary arrangement with their present condition as a laboring,\
landless, and homeless class."\
\
=Andrew Johnson's Plan--His Impeachment.=--Lincoln's successor, Andrew\
Johnson, the Vice President, soon after taking office, proposed to\
pursue a somewhat similar course. In a number of states he appointed\
military governors, instructing them at the earliest possible moment to\
assemble conventions, chosen "by that portion of the people of the said\
states who are loyal to the United States," and proceed to the\
organization of regular civil government. Johnson, a Southern man and a\
Democrat, was immediately charged by the Republicans with being too\
ready to restore the Southern states. As the months went by, the\
opposition to his measures and policies in Congress grew in size and\
bitterness. The contest resulted in the impeachment of Johnson by the\
House of Representatives in March, 1868, and his acquittal by the Senate\
merely because his opponents lacked one vote of the two-thirds required\
for conviction.\
\
=Congress Enacts "Reconstruction Laws."=--In fact, Congress was in a\
strategic position. It was the law-making body, and it could, moreover,\
determine the conditions under which Senators and Representatives from\
the South were to be readmitted. It therefore proceeded to pass a series\
of reconstruction acts--carrying all of them over Johnson's veto. These\
measures, the first of which became a law on March 2, 1867, betrayed an\
animus not found anywhere in Lincoln's plans or Johnson's proclamations.\
\
They laid off the ten states--the whole Confederacy with the exception\
of Tennessee--still outside the pale, into five military districts, each\
commanded by a military officer appointed by the President. They ordered\
the commanding general to prepare a register of voters for the election\
of delegates to conventions chosen for the purpose of drafting new\
constitutions. Such voters, however, were not to be, as Lincoln had\
suggested, loyal persons duly qualified under the law existing before\
secession but "the male citizens of said state, twenty-one years old and\
upward, of whatever race, color, or previous condition, ... except such\
as may be disfranchised for participation in the rebellion or for felony\
at common law." This was the death knell to the idea that the leaders of\
the Confederacy and their white supporters might be permitted to share\
in the establishment of the new order. Power was thus arbitrarily thrust\
into the hands of the newly emancipated male negroes and the handful of\
whites who could show a record of loyalty. That was not all. Each state\
was, under the reconstruction acts, compelled to ratify the fourteenth\
amendment to the federal Constitution as a price of restoration to the\
union.\
\
The composition of the conventions thus authorized may be imagined.\
Bondmen without the asking and without preparation found themselves the\
governing power. An army of adventurers from the North, "carpet baggers"\
as they were called, poured in upon the scene to aid in\
"reconstruction." Undoubtedly many men of honor and fine intentions gave\
unstinted service, but the results of their deliberations only\
aggravated the open wound left by the war. Any number of political\
doctors offered their prescriptions; but no effective remedy could be\
found. Under measures admittedly open to grave objections, the Southern\
states were one after another restored to the union by the grace of\
Congress, the last one in 1870. Even this grudging concession of the\
formalities of statehood did not mean a full restoration of honors and\
privileges. The last soldier was not withdrawn from the last Southern\
capital until 1877, and federal control over elections long remained as\
a sign of congressional supremacy.\
\
=The Status of the Freedmen.=--Even more intricate than the issues\
involved in restoring the seceded states to the union was the question\
of what to do with the newly emancipated slaves. That problem, often put\
to abolitionists before the war, had become at last a real concern. The\
thirteenth amendment abolishing slavery had not touched it at all. It\
declared bondmen free, but did nothing to provide them with work or\
homes and did not mention the subject of political rights. All these\
matters were left to the states, and the legislatures of some of them,\
by their famous "black codes," restored a form of servitude under the\
guise of vagrancy and apprentice laws. Such methods were in fact partly\
responsible for the reaction that led Congress to abandon Lincoln's\
policies and undertake its own program of reconstruction.\
\
Still no extensive effort was made to solve by law the economic problems\
of the bondmen. Radical abolitionists had advocated that the slaves when\
emancipated should be given outright the fields of their former\
masters; but Congress steadily rejected the very idea of confiscation.\
The necessity of immediate assistance it recognized by creating in 1865\
the Freedmen's Bureau to take care of refugees. It authorized the issue\
of food and clothing to the destitute and the renting of abandoned and\
certain other lands under federal control to former slaves at reasonable\
rates. But the larger problem of the relation of the freedmen to the\
land, it left to the slow working of time.\
\
Against sharp protests from conservative men, particularly among the\
Democrats, Congress did insist, however, on conferring upon the freedmen\
certain rights by national law. These rights fell into broad divisions,\
civil and political. By an act passed in 1866, Congress gave to former\
slaves the rights of white citizens in the matter of making contracts,\
giving testimony in courts, and purchasing, selling, and leasing\
property. As it was doubtful whether Congress had the power to enact\
this law, there was passed and submitted to the states the fourteenth\
amendment which gave citizenship to the freedmen, assured them of the\
privileges and immunities of citizens of the United States, and declared\
that no state should deprive any person of his life, liberty, or\
property without due process of law. Not yet satisfied, Congress\
attempted to give social equality to negroes by the second civil rights\
bill of 1875 which promised to them, among other things, the full and\
equal enjoyment of inns, theaters, public conveyances, and places of\
amusement--a law later declared unconstitutional by the Supreme Court.\
\
The matter of political rights was even more hotly contested; but the\
radical Republicans, like Charles Sumner, asserted that civil rights\
were not secure unless supported by the suffrage. In this same\
fourteenth amendment they attempted to guarantee the ballot to all negro\
men, leaving the women to take care of themselves. The amendment\
declared in effect that when any state deprived adult male citizens of\
the right to vote, its representation in Congress should be reduced in\
the proportion such persons bore to the voting population.\
\
This provision having failed to accomplish its purpose, the fifteenth\
amendment was passed and ratified, expressly declaring that no citizen\
should be deprived of the right to vote "on account of race, color, or\
previous condition of servitude." To make assurance doubly secure,\
Congress enacted in 1870, 1872, and 1873 three drastic laws, sometimes\
known as "force bills," providing for the use of federal authorities,\
civil and military, in supervising elections in all parts of the Union.\
So the federal government, having destroyed chattel slavery, sought by\
legal decree to sweep away all its signs and badges, civil, social, and\
political. Never, save perhaps in some of the civil conflicts of Greece\
or Rome, had there occurred in the affairs of a nation a social\
revolution so complete, so drastic, and far-reaching in its results.\
\
\
SUMMARY OF THE SECTIONAL CONFLICT\
\
Just as the United States, under the impetus of Western enterprise,\
rounded out the continental domain, its very existence as a nation was\
challenged by a fratricidal conflict between two sections. This storm\
had been long gathering upon the horizon. From the very beginning in\
colonial times there had been a marked difference between the South and\
the North. The former by climate and soil was dedicated to a planting\
system--the cultivation of tobacco, rice, cotton, and sugar cane--and in\
the course of time slave labor became the foundation of the system. The\
North, on the other hand, supplemented agriculture by commerce, trade,\
and manufacturing. Slavery, though lawful, did not flourish there. An\
abundant supply of free labor kept the Northern wheels turning.\
\
This difference between the two sections, early noted by close\
observers, was increased with the advent of the steam engine and the\
factory system. Between 1815 and 1860 an industrial revolution took\
place in the North. Its signs were gigantic factories, huge aggregations\
of industrial workers, immense cities, a flourishing commerce, and\
prosperous banks. Finding an unfavorable reception in the South, the new\
industrial system was confined mainly to the North. By canals and\
railways New York, Boston, and Philadelphia were linked with the\
wheatfields of Ohio, Indiana, and Illinois. A steel net wove North and\
Northwest together. A commercial net supplemented it. Western trade was\
diverted from New Orleans to the East and Eastern credit sustained\
Western enterprise.\
\
In time, the industrial North and the planting South evolved different\
ideas of political policy. The former looked with favor on protective\
tariffs, ship subsidies, a sound national banking system, and internal\
improvements. The farmers of the West demanded that the public domain be\
divided up into free homesteads for farmers. The South steadily swung\
around to the opposite view. Its spokesmen came to regard most of these\
policies as injurious to the planting interests.\
\
The economic questions were all involved in a moral issue. The Northern\
states, in which slavery was of slight consequence, had early abolished\
the institution. In the course of a few years there appeared\
uncompromising advocates of universal emancipation. Far and wide the\
agitation spread. The South was thoroughly frightened. It demanded\
protection against the agitators, the enforcement of its rights in the\
case of runaway slaves, and equal privileges for slavery in the new\
territories.\
\
With the passing years the conflict between the two sections increased\
in bitterness. It flamed up in 1820 and was allayed by the Missouri\
compromise. It took on the form of a tariff controversy and\
nullification in 1832. It appeared again after the Mexican war when the\
question of slavery in the new territories was raised. Again\
compromise--the great settlement of 1850--seemed to restore peace, only\
to prove an illusion. A series of startling events swept the country\
into war: the repeal of the Missouri compromise in 1854, the rise of the\
Republican party pledged to the prohibition of slavery in the\
territories, the Dred Scott decision of 1857, the Lincoln-Douglas\
debates, John Brown's raid, the election of Lincoln, and secession.\
\
The Civil War, lasting for four years, tested the strength of both North\
and South, in leadership, in finance, in diplomatic skill, in material\
resources, in industry, and in armed forces. By the blockade of Southern\
ports, by an overwhelming weight of men and materials, and by relentless\
hammering on the field of battle, the North was victorious.\
\
The results of the war were revolutionary in character. Slavery was\
abolished and the freedmen given the ballot. The Southern planters who\
had been the leaders of their section were ruined financially and almost\
to a man excluded from taking part in political affairs. The union was\
declared to be perpetual and the right of a state to secede settled by\
the judgment of battle. Federal control over the affairs of states,\
counties, and cities was established by the fourteenth amendment. The\
power and prestige of the federal government were enhanced beyond\
imagination. The North was now free to pursue its economic policies: a\
protective tariff, a national banking system, land grants for railways,\
free lands for farmers. Planting had dominated the country for nearly a\
generation. Business enterprise was to take its place.\
\
\
=References=\
\
NORTHERN ACCOUNTS\
\
J.K. Hosmer, _The Appeal to Arms_ and _The Outcome of the Civil War_\
(American Nation Series).\
\
J. Ropes, _History of the Civil War_ (best account of military\
campaigns).\
\
J.F. Rhodes, _History of the United States_, Vols. III, IV, and V.\
\
J.T. Morse, _Abraham Lincoln_ (2 vols.).\
\
\
SOUTHERN ACCOUNTS\
\
W.E. Dodd, _Jefferson Davis_.\
\
Jefferson Davis, _Rise and Fall of the Confederate Government_.\
\
E. Pollard, _The Lost Cause_.\
\
A.H. Stephens, _The War between the States_.\
\
\
=Questions=\
\
1. Contrast the reception of secession in 1860 with that given to\
nullification in 1832.\
\
2. Compare the Northern and Southern views of the union.\
\
3. What were the peculiar features of the Confederate constitution?\
\
4. How was the Confederacy financed?\
\
5. Compare the resources of the two sections.\
\
6. On what foundations did Southern hopes rest?\
\
7. Describe the attempts at a peaceful settlement.\
\
8. Compare the raising of armies for the Civil War with the methods\
employed in the World War. (See below, chapter XXV.)\
\
9. Compare the financial methods of the government in the two wars.\
\
10. Explain why the blockade was such a deadly weapon.\
\
11. Give the leading diplomatic events of the war.\
\
12. Trace the growth of anti-slavery sentiment.\
\
13. What measures were taken to restrain criticism of the government?\
\
14. What part did Lincoln play in all phases of the war?\
\
15. State the principal results of the war.\
\
16. Compare Lincoln's plan of reconstruction with that adopted by\
Congress.\
\
17. What rights did Congress attempt to confer upon the former slaves?\
\
\
=Research Topics=\
\
=Was Secession Lawful?=--The Southern view by Jefferson Davis in\
Harding, _Select Orations Illustrating American History_, pp. 364-369.\
Lincoln's view, Harding, pp. 371-381.\
\
=The Confederate Constitution.=--Compare with the federal Constitution\
in Macdonald, _Documentary Source Book_, pp. 424-433 and pp. 271-279.\
\
=Federal Legislative Measures.=--Prepare a table and brief digest of the\
important laws relating to the war. Macdonald, pp. 433-482.\
\
=Economic Aspects of the War.=--Coman, _Industrial History of the United\
States_, pp. 279-301. Dewey, _Financial History of the United States_,\
Chaps. XII and XIII. Tabulate the economic measures of Congress in\
Macdonald.\
\
=Military Campaigns.=--The great battles are fully treated in Rhodes,\
_History of the Civil War_, and teachers desiring to emphasize military\
affairs may assign campaigns to members of the class for study and\
report. A briefer treatment in Elson, _History of the United States_,\
pp. 641-785.\
\
=Biographical Studies.=--Lincoln, Davis, Lee, Grant, Sherman, and other\
leaders in civil and military affairs, with reference to local "war\
governors."\
\
=English and French Opinion of the War.=--Rhodes, _History of the United\
States_, Vol. IV, pp. 337-394.\
\
=The South during the War.=--Rhodes, Vol. V, pp. 343-382.\
\
=The North during the War.=--Rhodes, Vol. V, pp. 189-342.\
\
=Reconstruction Measures.=--Macdonald, _Source Book_, pp. 500-511;\
514-518; 529-530; Elson, pp. 786-799.\
\
=The Force Bills.=--Macdonald, pp. 547-551; 554-564.\
\
\
\
\
PART VI. NATIONAL GROWTH AND WORLD POLITICS\
\
\
\
\
CHAPTER XVI\
\
THE POLITICAL AND ECONOMIC EVOLUTION OF THE SOUTH\
\
\
The outcome of the Civil War in the South was nothing short of a\
revolution. The ruling class, the law, and the government of the old\
order had been subverted. To political chaos was added the havoc wrought\
in agriculture, business, and transportation by military operations. And\
as if to fill the cup to the brim, the task of reconstruction was\
committed to political leaders from another section of the country,\
strangers to the life and traditions of the South.\
\
\
THE SOUTH AT THE CLOSE OF THE WAR\
\
=A Ruling Class Disfranchised.=--As the sovereignty of the planters had\
been the striking feature of the old regime, so their ruin was the\
outstanding fact of the new. The situation was extraordinary. The\
American Revolution was carried out by people experienced in the arts of\
self-government, and at its close they were free to follow the general\
course to which they had long been accustomed. The French Revolution\
witnessed the overthrow of the clergy and the nobility; but middle\
classes who took their places had been steadily rising in intelligence\
and wealth.\
\
The Southern Revolution was unlike either of these cataclysms. It was\
not brought about by a social upheaval, but by an external crisis. It\
did not enfranchise a class that sought and understood power, but\
bondmen who had played no part in the struggle. Moreover it struck down\
a class equipped to rule. The leading planters were almost to a man\
excluded from state and federal offices, and the fourteenth amendment\
was a bar to their return. All civil and military places under the\
authority of the United States and of the states were closed to every\
man who had taken an oath to support the Constitution as a member of\
Congress, as a state legislator, or as a state or federal officer, and\
afterward engaged in "insurrection or rebellion," or "given aid and\
comfort to the enemies" of the United States. This sweeping provision,\
supplemented by the reconstruction acts, laid under the ban most of the\
talent, energy, and spirit of the South.\
\
=The Condition of the State Governments.=--The legislative, executive,\
and judicial branches of the state governments thus passed into the\
control of former slaves, led principally by Northern adventurers or\
Southern novices, known as "Scalawags." The result was a carnival of\
waste, folly, and corruption. The "reconstruction" assembly of South\
Carolina bought clocks at $480 apiece and chandeliers at $650. To\
purchase land for former bondmen the sum of $800,000 was appropriated;\
and swamps bought at seventy-five cents an acre were sold to the state\
at five times the cost. In the years between 1868 and 1873, the debt of\
the state rose from about $5,800,000 to $24,000,000, and millions of the\
increase could not be accounted for by the authorities responsible for\
it.\
\
=Economic Ruin--Urban and Rural.=--No matter where Southern men turned\
in 1865 they found devastation--in the towns, in the country, and along\
the highways. Atlanta, the city to which Sherman applied the torch, lay\
in ashes; Nashville and Chattanooga had been partially wrecked; Richmond\
and Augusta had suffered severely from fires. Charleston was described\
by a visitor as "a city of ruins, of desolation, of vacant houses, of\
rotten wharves, of deserted warehouses, of weed gardens, of miles of\
grass-grown streets.... How few young men there are, how generally the\
young women are dressed in black! The flower of their proud aristocracy\
is buried on scores of battle fields."\
\
Those who journeyed through the country about the same time reported\
desolation equally widespread and equally pathetic. An English traveler\
who made his way along the course of the Tennessee River in 1870 wrote:\
"The trail of war is visible throughout the valley in burnt-up gin\
houses, ruined bridges, mills, and factories ... and large tracts of\
once cultivated land are stripped of every vestige of fencing. The\
roads, long neglected, are in disorder and, having in many places become\
impassable, new tracks have been made through the woods and fields\
without much respect to boundaries." Many a great plantation had been\
confiscated by the federal authorities while the owner was in\
Confederate service. Many more lay in waste. In the wake of the armies\
the homes of rich and poor alike, if spared the torch, had been\
despoiled of the stock and seeds necessary to renew agriculture.\
\
=Railways Dilapidated.=--Transportation was still more demoralized. This\
is revealed in the pages of congressional reports based upon first-hand\
investigations. One eloquent passage illustrates all the rest. From\
Pocahontas to Decatur, Alabama, a distance of 114 miles, we are told,\
the railroad was "almost entirely destroyed, except the road bed and\
iron rails, and they were in a very bad condition--every bridge and\
trestle destroyed, cross-ties rotten, buildings burned, water tanks\
gone, tracks grown up in weeds and bushes, not a saw mill near the line\
and the labor system of the country gone. About forty miles of the track\
were burned, the cross-ties entirely destroyed, and the rails bent and\
twisted in such a manner as to require great labor to straighten and a\
large portion of them requiring renewal."\
\
=Capital and Credit Destroyed.=--The fluid capital of the South, money\
and credit, was in the same prostrate condition as the material capital.\
The Confederate currency, inflated to the bursting point, had utterly\
collapsed and was as worthless as waste paper. The bonds of the\
Confederate government were equally valueless. Specie had nearly\
disappeared from circulation. The fourteenth amendment to the federal\
Constitution had made all "debts, obligations, and claims" incurred in\
aid of the Confederate cause "illegal and void." Millions of dollars\
owed to Northern creditors before the war were overdue and payment was\
pressed upon the debtors. Where such debts were secured by mortgages on\
land, executions against the property could be obtained in federal\
courts.\
\
\
THE RESTORATION OF WHITE SUPREMACY\
\
=Intimidation.=--In both politics and economics, the process of\
reconstruction in the South was slow and arduous. The first battle in\
the political contest for white supremacy was won outside the halls of\
legislatures and the courts of law. It was waged, in the main, by secret\
organizations, among which the Ku Klux Klan and the White Camelia were\
the most prominent. The first of these societies appeared in Tennessee\
in 1866 and held its first national convention the following year. It\
was in origin a social club. According to its announcement, its objects\
were "to protect the weak, the innocent, and the defenceless from the\
indignities, wrongs, and outrages of the lawless, the violent, and the\
brutal; and to succor the suffering, especially the widows and orphans\
of the Confederate soldiers." The whole South was called "the Empire"\
and was ruled by a "Grand Wizard." Each state was a realm and each\
county a province. In the secret orders there were enrolled over half a\
million men.\
\
The methods of the Ku Klux and the White Camelia were similar. Solemn\
parades of masked men on horses decked in long robes were held,\
sometimes in the daytime and sometimes at the dead of night. Notices\
were sent to obnoxious persons warning them to stop certain practices.\
If warning failed, something more convincing was tried. Fright was the\
emotion most commonly stirred. A horseman, at the witching hour of\
midnight, would ride up to the house of some offender, lift his head\
gear, take off a skull, and hand it to the trembling victim with the\
request that he hold it for a few minutes. Frequently violence was\
employed either officially or unofficially by members of the Klan. Tar\
and feathers were freely applied; the whip was sometimes laid on\
unmercifully, and occasionally a brutal murder was committed. Often the\
members were fired upon from bushes or behind trees, and swift\
retaliation followed. So alarming did the clashes become that in 1870\
Congress forbade interference with electors or going in disguise for the\
purpose of obstructing the exercise of the rights enjoyed under federal\
law.\
\
In anticipation of such a step on the part of the federal government,\
the Ku Klux was officially dissolved by the "Grand Wizard" in 1869.\
Nevertheless, the local societies continued their organization and\
methods. The spirit survived the national association. "On the whole,"\
says a Southern writer, "it is not easy to see what other course was\
open to the South.... Armed resistance was out of the question. And yet\
there must be some control had of the situation.... If force was denied,\
craft was inevitable."\
\
=The Struggle for the Ballot Box.=--The effects of intimidation were\
soon seen at elections. The freedman, into whose inexperienced hand the\
ballot had been thrust, was ordinarily loath to risk his head by the\
exercise of his new rights. He had not attained them by a long and\
laborious contest of his own and he saw no urgent reason why he should\
battle for the privilege of using them. The mere show of force, the mere\
existence of a threat, deterred thousands of ex-slaves from appearing at\
the polls. Thus the whites steadily recovered their dominance. Nothing\
could prevent it. Congress enacted force bills establishing federal\
supervision of elections and the Northern politicians protested against\
the return of former Confederates to practical, if not official, power;\
but all such opposition was like resistance to the course of nature.\
\
=Amnesty for Southerners.=--The recovery of white supremacy in this way\
was quickly felt in national councils. The Democratic party in the North\
welcomed it as a sign of its return to power. The more moderate\
Republicans, anxious to heal the breach in American unity, sought to\
encourage rather than to repress it. So it came about that amnesty for\
Confederates was widely advocated. Yet it must be said that the struggle\
for the removal of disabilities was stubborn and bitter. Lincoln, with\
characteristic generosity, in the midst of the war had issued a general\
proclamation of amnesty to nearly all who had been in arms against the\
Union, on condition that they take an oath of loyalty; but Johnson,\
vindictive toward Southern leaders and determined to make "treason\
infamous," had extended the list of exceptions. Congress, even more\
relentless in its pursuit of Confederates, pushed through the fourteenth\
amendment which worked the sweeping disabilities we have just described.\
\
To appeals for comprehensive clemency, Congress was at first adamant. In\
vain did men like Carl Schurz exhort their colleagues to crown their\
victory in battle with a noble act of universal pardon and oblivion.\
Congress would not yield. It would grant amnesty in individual cases;\
for the principle of proscription it stood fast. When finally in 1872,\
seven years after the surrender at Appomattox, it did pass the general\
amnesty bill, it insisted on certain exceptions. Confederates who had\
been members of Congress just before the war, or had served in other\
high posts, civil or military, under the federal government, were still\
excluded from important offices. Not until the summer of 1898, when the\
war with Spain produced once more a union of hearts, did Congress relent\
and abolish the last of the disabilities imposed on the Confederates.\
\
=The Force Bills Attacked and Nullified.=--The granting of amnesty\
encouraged the Democrats to redouble their efforts all along the line.\
In 1874 they captured the House of Representatives and declared war on\
the "force bills." As a Republican Senate blocked immediate repeal, they\
resorted to an ingenious parliamentary trick. To the appropriation bill\
for the support of the army they attached a "rider," or condition, to\
the effect that no troops should be used to sustain the Republican\
government in Louisiana. The Senate rejected the proposal. A deadlock\
ensued and Congress adjourned without making provision for the army.\
Satisfied with the technical victory, the Democrats let the army bill\
pass the next session, but kept up their fight on the force laws until\
they wrung from President Hayes a measure forbidding the use of United\
States troops in supervising elections. The following year they again\
had recourse to a rider on the army bill and carried it through, putting\
an end to the use of money for military control of elections. The\
reconstruction program was clearly going to pieces, and the Supreme\
Court helped along the process of dissolution by declaring parts of the\
laws invalid. In 1878 the Democrats even won a majority in the Senate\
and returned to power a large number of men once prominent in the\
Confederate cause.\
\
The passions of the war by this time were evidently cooling. A new\
generation of men was coming on the scene. The supremacy of the whites\
in the South, if not yet complete, was at least assured. Federal\
marshals, their deputies, and supervisors of elections still possessed\
authority over the polls, but their strength had been shorn by the\
withdrawal of United States troops. The war on the remaining remnants of\
the "force bills" lapsed into desultory skirmishing. When in 1894 the\
last fragment was swept away, the country took little note of the fact.\
The only task that lay before the Southern leaders was to write in the\
constitutions of their respective states the provisions of law which\
would clinch the gains so far secured and establish white supremacy\
beyond the reach of outside intervention.\
\
=White Supremacy Sealed by New State Constitutions.=--The impetus to\
this final step was given by the rise of the Populist movement in the\
South, which sharply divided the whites and in many communities threw\
the balance of power into the hands of the few colored voters who\
survived the process of intimidation. Southern leaders now devised new\
constitutions so constructed as to deprive negroes of the ballot by law.\
Mississippi took the lead in 1890; South Carolina followed five years\
later; Louisiana, in 1898; North Carolina, in 1900; Alabama and\
Maryland, in 1901; and Virginia, in 1902.\
\
The authors of these measures made no attempt to conceal their purposes.\
"The intelligent white men of the South," said Governor Tillman, "intend\
to govern here." The fifteenth amendment to the federal Constitution,\
however, forbade them to deprive any citizen of the right to vote on\
account of race, color, or previous condition of servitude. This made\
necessary the devices of indirection. They were few, simple, and\
effective. The first and most easily administered was the ingenious\
provision requiring each prospective voter to read a section of the\
state constitution or "understand and explain it" when read to him by\
the election officers. As an alternative, the payment of taxes or the\
ownership of a small amount of property was accepted as a qualification\
for voting. Southern leaders, unwilling to disfranchise any of the poor\
white men who had stood side by side with them "in the dark days of\
reconstruction," also resorted to a famous provision known as "the\
grandfather clause." This plan admitted to the suffrage any man who did\
not have either property or educational qualifications, provided he had\
voted on or before 1867 or was the son or grandson of any such person.\
\
The devices worked effectively. Of the 147,000 negroes in Mississippi\
above the age of twenty-one, only about 8600 registered under the\
constitution of 1890. Louisiana had 127,000 colored voters enrolled in\
1896; under the constitution drafted two years later the registration\
fell to 5300. An analysis of the figures for South Carolina in 1900\
indicates that only about one negro out of every hundred adult males of\
that race took part in elections. Thus was closed this chapter of\
reconstruction.\
\
=The Supreme Court Refuses to Intervene.=--Numerous efforts were made to\
prevail upon the Supreme Court of the United States to declare such laws\
unconstitutional; but the Court, usually on technical grounds, avoided\
coming to a direct decision on the merits of the matter. In one case\
the Court remarked that it could not take charge of and operate the\
election machinery of Alabama; it concluded that "relief from a great\
political wrong, if done as alleged, by the people of a state and by the\
state itself, must be given by them, or by the legislative and executive\
departments of the government of the United States." Only one of the\
several schemes employed, namely, the "grandfather clause," was held to\
be a violation of the federal Constitution. This blow, effected in 1915\
by the decision in the Oklahoma and Maryland cases, left, however, the\
main structure of disfranchisement unimpaired.\
\
=Proposals to Reduce Southern Representation in Congress.=--These\
provisions excluding thousands of male citizens from the ballot did not,\
in express terms, deprive any one of the vote on account of race or\
color. They did not, therefore, run counter to the letter of the\
fifteenth amendment; but they did unquestionably make the states which\
adopted them liable to the operations of the fourteenth amendment. The\
latter very explicitly provides that whenever any state deprives adult\
male citizens of the right to vote (except in certain minor cases) the\
representation of the state in Congress shall be reduced in the\
proportion which such number of disfranchised citizens bears to the\
whole number of male citizens over twenty-one years of age.\
\
Mindful of this provision, those who protested against disfranchisement\
in the South turned to the Republican party for relief, asking for\
action by the political branches of the federal government as the\
Supreme Court had suggested. The Republicans responded in their platform\
of 1908 by condemning all devices designed to deprive any one of the\
ballot for reasons of color alone; they demanded the enforcement in\
letter and spirit of the fourteenth as well as all other amendments.\
Though victorious in the election, the Republicans refrained from\
reopening the ancient contest; they made no attempt to reduce Southern\
representation in the House. Southern leaders, while protesting against\
the declarations of their opponents, were able to view them as idle\
threats in no way endangering the security of the measures by which\
political reconstruction had been undone.\
\
=The Solid South.=--Out of the thirty-year conflict against "carpet-bag\
rule" there emerged what was long known as the "solid South"--a South\
that, except occasionally in the border states, never gave an electoral\
vote to a Republican candidate for President. Before the Civil War, the\
Southern people had been divided on political questions. Take, for\
example, the election of 1860. In all the fifteen slave states the\
variety of opinion was marked. In nine of them--Delaware, Virginia,\
Tennessee, Missouri, Maryland, Louisiana, Kentucky, Georgia, and\
Arkansas--the combined vote against the representative of the extreme\
Southern point of view, Breckinridge, constituted a safe majority. In\
each of the six states which were carried by Breckinridge, there was a\
large and powerful minority. In North Carolina Breckinridge's majority\
over Bell and Douglas was only 849 votes. Equally astounding to those\
who imagine the South united in defense of extreme views in 1860 was the\
vote for Bell, the Unionist candidate, who stood firmly for the\
Constitution and silence on slavery. In every Southern state Bell's vote\
was large. In Virginia, Kentucky, Missouri, and Tennessee it was greater\
than that received by Breckinridge; in Georgia, it was 42,000 against\
51,000; in Louisiana, 20,000 against 22,000; in Mississippi, 25,000\
against 40,000.\
\
The effect of the Civil War upon these divisions was immediate and\
decisive, save in the border states where thousands of men continued to\
adhere to the cause of Union. In the Confederacy itself nearly all\
dissent was silenced by war. Men who had been bitter opponents joined\
hands in defense of their homes; when the armed conflict was over they\
remained side by side working against "Republican misrule and negro\
domination." By 1890, after Northern supremacy was definitely broken,\
they boasted that there were at least twelve Southern states in which no\
Republican candidate for President could win a single electoral vote.\
\
=Dissent in the Solid South.=--Though every one grew accustomed to speak\
of the South as "solid," it did not escape close observers that in a\
number of Southern states there appeared from time to time a fairly\
large body of dissenters. In 1892 the Populists made heavy inroads upon\
the Democratic ranks. On other occasions, the contests between factions\
within the Democratic party over the nomination of candidates revealed\
sharp differences of opinion. In some places, moreover, there grew up a\
Republican minority of respectable size. For example, in Georgia, Mr.\
Taft in 1908 polled 41,000 votes against 72,000 for Mr. Bryan; in North\
Carolina, 114,000 against 136,000; in Tennessee, 118,000 against\
135,000; in Kentucky, 235,000 against 244,000. In 1920, Senator Harding,\
the Republican candidate, broke the record by carrying Tennessee as well\
as Kentucky, Oklahoma, and Maryland.\
\
\
THE ECONOMIC ADVANCE OF THE SOUTH\
\
=The Break-up of the Great Estates.=--In the dissolution of chattel\
slavery it was inevitable that the great estate should give way before\
the small farm. The plantation was in fact founded on slavery. It was\
continued and expanded by slavery. Before the war the prosperous\
planter, either by inclination or necessity, invested his surplus in\
more land to add to his original domain. As his slaves increased in\
number, he was forced to increase his acreage or sell them, and he\
usually preferred the former, especially in the Far South. Still another\
element favored the large estate. Slave labor quickly exhausted the soil\
and of its own force compelled the cutting of the forests and the\
extension of the area under cultivation. Finally, the planter took a\
natural pride in his great estate; it was a sign of his prowess and his\
social prestige.\
\
In 1865 the foundations of the planting system were gone. It was\
difficult to get efficient labor to till the vast plantations. The\
planters themselves were burdened with debts and handicapped by lack of\
capital. Negroes commonly preferred tilling plots of their own, rented\
or bought under mortgage, to the more irksome wage labor under white\
supervision. The land hunger of the white farmer, once checked by the\
planting system, reasserted itself. Before these forces the plantation\
broke up. The small farm became the unit of cultivation in the South as\
in the North. Between 1870 and 1900 the number of farms doubled in every\
state south of the line of the Potomac and Ohio rivers, except in\
Arkansas and Louisiana. From year to year the process of breaking up\
continued, with all that it implied in the creation of land-owning\
farmers.\
\
=The Diversification of Crops.=--No less significant was the concurrent\
diversification of crops. Under slavery, tobacco, rice, and sugar were\
staples and "cotton was king." These were standard crops. The methods of\
cultivation were simple and easily learned. They tested neither the\
skill nor the ingenuity of the slaves. As the returns were quick, they\
did not call for long-time investments of capital. After slavery was\
abolished, they still remained the staples, but far-sighted\
agriculturists saw the dangers of depending upon a few crops. The mild\
climate all the way around the coast from Virginia to Texas and the\
character of the alluvial soil invited the exercise of more imagination.\
Peaches, oranges, peanuts, and other fruits and vegetables were found to\
grow luxuriantly. Refrigeration for steamships and freight cars put the\
markets of great cities at the doors of Southern fruit and vegetable\
gardeners. The South, which in planting days had relied so heavily upon\
the Northwest for its foodstuffs, began to battle for independence.\
Between 1880 and the close of the century the value of its farm crops\
increased from $660,000,000 to $1,270,000,000.\
\
=The Industrial and Commercial Revolution.=--On top of the radical\
changes in agriculture came an industrial and commercial revolution. The\
South had long been rich in natural resources, but the slave system had\
been unfavorable to their development. Rivers that would have turned\
millions of spindles tumbled unheeded to the seas. Coal and iron beds\
lay unopened. Timber was largely sacrificed in clearing lands for\
planting, or fell to earth in decay. Southern enterprise was consumed in\
planting. Slavery kept out the white immigrants who might have supplied\
the skilled labor for industry.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
STEEL MILLS--BIRMINGHAM, ALABAMA]\
\
After 1865, achievement and fortune no longer lay on the land alone. As\
soon as the paralysis of the war was over, the South caught the\
industrial spirit that had conquered feudal Europe and the agricultural\
North. In the development of mineral wealth, enormous strides were\
taken. Iron ore of every quality was found, the chief beds being in\
Virginia, West Virginia, Tennessee, Kentucky, North Carolina, Georgia,\
Alabama, Arkansas, and Texas. Five important coal basins were uncovered:\
in Virginia, North Carolina, the Appalachian chain from Maryland to\
Northern Alabama, Kentucky, Arkansas, and Texas. Oil pools were found\
in Kentucky, Tennessee, and Texas. Within two decades, 1880 to 1900, the\
output of mineral wealth multiplied tenfold: from ten millions a year to\
one hundred millions. The iron industries of West Virginia and Alabama\
began to rival those of Pennsylvania. Birmingham became the Pittsburgh\
and Atlanta the Chicago of the South.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
A SOUTHERN COTTON MILL IN A COTTON FIELD]\
\
In other lines of industry, lumbering and cotton manufacturing took a\
high rank. The development of Southern timber resources was in every\
respect remarkable, particularly in Louisiana, Arkansas, and\
Mississippi. At the end of the first decade of the twentieth century,\
primacy in lumber had passed from the Great Lakes region to the South.\
In 1913 eight Southern states produced nearly four times as much lumber\
as the Lake states and twice as much as the vast forests of Washington\
and Oregon.\
\
The development of the cotton industry, in the meantime, was similarly\
astounding. In 1865 cotton spinning was a negligible matter in the\
Southern states. In 1880 they had one-fourth of the mills of the\
country. At the end of the century they had one-half the mills, the two\
Carolinas taking the lead by consuming more than one-third of their\
entire cotton crop. Having both the raw materials and the power at hand,\
they enjoyed many advantages over the New England rivals, and at the\
opening of the new century were outstripping the latter in the\
proportion of spindles annually put into operation. Moreover, the cotton\
planters, finding a market at the neighboring mills, began to look\
forward to a day when they would be somewhat emancipated from absolute\
dependence upon the cotton exchanges of New York, New Orleans, and\
Liverpool.\
\
Transportation kept pace with industry. In 1860, the South had about ten\
thousand miles of railway. By 1880 the figure had doubled. During the\
next twenty years over thirty thousand miles were added, most of the\
increase being in Texas. About 1898 there opened a period of\
consolidation in which scores of short lines were united, mainly under\
the leadership of Northern capitalists, and new through service opened\
to the North and West. Thus Southern industries were given easy outlets\
to the markets of the nation and brought within the main currents of\
national business enterprise.\
\
=The Social Effects of the Economic Changes.=--As long as the slave\
system lasted and planting was the major interest, the South was bound\
to be sectional in character. With slavery gone, crops diversified,\
natural resources developed, and industries promoted, the social order\
of the ante-bellum days inevitably dissolved; the South became more and\
more assimilated to the system of the North. In this process several\
lines of development are evident.\
\
In the first place we see the steady rise of the small farmer. Even in\
the old days there had been a large class of white yeomen who owned no\
slaves and tilled the soil with their own hands, but they labored under\
severe handicaps. They found the fertile lands of the coast and river\
valleys nearly all monopolized by planters, and they were by the force\
of circumstances driven into the uplands where the soil was thin and the\
crops were light. Still they increased in numbers and zealously worked\
their freeholds.\
\
The war proved to be their opportunity. With the break-up of the\
plantations, they managed to buy land more worthy of their plows. By\
intelligent labor and intensive cultivation they were able to restore\
much of the worn-out soil to its original fertility. In the meantime\
they rose with their prosperity in the social and political scale. It\
became common for the sons of white farmers to enter the professions,\
while their daughters went away to college and prepared for teaching.\
Thus a more democratic tone was given to the white society of the South.\
Moreover the migration to the North and West, which had formerly carried\
thousands of energetic sons and daughters to search for new homesteads,\
was materially reduced. The energy of the agricultural population went\
into rehabilitation.\
\
The increase in the number of independent farmers was accompanied by the\
rise of small towns and villages which gave diversity to the life of the\
South. Before 1860 it was possible to travel through endless stretches\
of cotton and tobacco. The social affairs of the planter's family\
centered in the homestead even if they were occasionally interrupted by\
trips to distant cities or abroad. Carpentry, bricklaying, and\
blacksmithing were usually done by slaves skilled in simple handicrafts.\
Supplies were bought wholesale. In this way there was little place in\
plantation economy for villages and towns with their stores and\
mechanics.\
\
The abolition of slavery altered this. Small farms spread out where\
plantations had once stood. The skilled freedmen turned to agriculture\
rather than to handicrafts; white men of a business or mechanical bent\
found an opportunity to serve the needs of their communities. So local\
merchants and mechanics became an important element in the social\
system. In the county seats, once dominated by the planters, business\
and professional men assumed the leadership.\
\
Another vital outcome of this revolution was the transference of a large\
part of planting enterprise to business. Mr. Bruce, a Southern historian\
of fine scholarship, has summed up this process in a single telling\
paragraph: "The higher planting class that under the old system gave so\
much distinction to rural life has, so far as it has survived at all,\
been concentrated in the cities. The families that in the time of\
slavery would have been found only in the country are now found, with a\
few exceptions, in the towns. The transplantation has been practically\
universal. The talent, the energy, the ambition that formerly sought\
expression in the management of great estates and the control of hosts\
of slaves, now seek a field of action in trade, in manufacturing\
enterprises, or in the general enterprises of development. This was for\
the ruling class of the South the natural outcome of the great economic\
revolution that followed the war."\
\
As in all other parts of the world, the mechanical revolution was\
attended by the growth of a population of industrial workers dependent\
not upon the soil but upon wages for their livelihood. When Jefferson\
Davis was inaugurated President of the Southern Confederacy, there were\
approximately only one hundred thousand persons employed in Southern\
manufactures as against more than a million in Northern mills. Fifty\
years later, Georgia and Alabama alone had more than one hundred and\
fifty thousand wage-earners. Necessarily this meant also a material\
increase in urban population, although the wide dispersion of cotton\
spinning among small centers prevented the congestion that had\
accompanied the rise of the textile industry in New England. In 1910,\
New Orleans, Atlanta, Memphis, Nashville, and Houston stood in the same\
relation to the New South that Cincinnati, Chicago, Cleveland, and\
Detroit had stood to the New West fifty years before. The problems of\
labor and capital and municipal administration, which the earlier\
writers boasted would never perplex the planting South, had come in full\
force.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
A GLIMPSE OF MEMPHIS, TENNESSEE]\
\
=The Revolution in the Status of the Slaves.=--No part of Southern\
society was so profoundly affected by the Civil War and economic\
reconstruction as the former slaves. On the day of emancipation, they\
stood free, but empty-handed, the owners of no tools or property, the\
masters of no trade and wholly inexperienced in the arts of self-help\
that characterized the whites in general. They had never been accustomed\
to looking out for themselves. The plantation bell had called them to\
labor and released them. Doles of food and clothing had been regularly\
made in given quantities. They did not understand wages, ownership,\
renting, contracts, mortgages, leases, bills, or accounts.\
\
When they were emancipated, four courses were open to them. They could\
flee from the plantation to the nearest town or city, or to the distant\
North, to seek a livelihood. Thousands of them chose this way,\
overcrowding cities where disease mowed them down. They could remain\
where they, were in their cabins and work for daily wages instead of\
food, clothing, and shelter. This second course the major portion of\
them chose; but, as few masters had cash to dispense, the new relation\
was much like the old, in fact. It was still one of barter. The planter\
offered food, clothing, and shelter; the former slaves gave their labor\
in return. That was the best that many of them could do.\
\
A third course open to freedmen was that of renting from the former\
master, paying him usually with a share of the produce of the land. This\
way a large number of them chose. It offered them a chance to become\
land owners in time and it afforded an easier life, the renter being, to\
a certain extent at least, master of his own hours of labor. The final\
and most difficult path was that to ownership of land. Many a master\
helped his former slaves to acquire small holdings by offering easy\
terms. The more enterprising and the more fortunate who started life as\
renters or wage-earners made their way upward to ownership in so many\
cases that by the end of the century, one-fourth of the colored laborers\
on the land owned the soil they tilled.\
\
In the meantime, the South, though relatively poor, made relatively\
large expenditures for the education of the colored population. By the\
opening of the twentieth century, facilities were provided for more than\
one-half of the colored children of school age. While in many respects\
this progress was disappointing, its significance, to be appreciated,\
must be derived from a comparison with the total illiteracy which\
prevailed under slavery.\
\
In spite of all that happened, however, the status of the negroes in the\
South continued to give a peculiar character to that section of the\
country. They were almost entirely excluded from the exercise of the\
suffrage, especially in the Far South. Special rooms were set aside for\
them at the railway stations and special cars on the railway lines. In\
the field of industry calling for technical skill, it appears, from the\
census figures, that they lost ground between 1890 and 1900--a condition\
which their friends ascribed to discriminations against them in law and\
in labor organizations and their critics ascribed to their lack of\
aptitude. Whatever may be the truth, the fact remained that at the\
opening of the twentieth century neither the hopes of the emancipators\
nor the fears of their opponents were realized. The marks of the\
"peculiar institution" were still largely impressed upon Southern\
society.\
\
The situation, however, was by no means unchanging. On the contrary\
there was a decided drift in affairs. For one thing, the proportion of\
negroes in the South had slowly declined. By 1900 they were in a\
majority in only two states, South Carolina and Mississippi. In\
Arkansas, Virginia, West Virginia, and North Carolina the proportion of\
the white population was steadily growing. The colored migration\
northward increased while the westward movement of white farmers which\
characterized pioneer days declined. At the same time a part of the\
foreign immigration into the United States was diverted southward. As\
the years passed these tendencies gained momentum. The already huge\
colored quarters in some Northern cities were widely expanded, as whole\
counties in the South were stripped of their colored laborers. The race\
question, in its political and economic aspects, became less and less\
sectional, more and more national. The South was drawn into the main\
stream of national life. The separatist forces which produced the\
cataclysm of 1861 sank irresistibly into the background.\
\
\
=References=\
\
H.W. Grady, _The New South_ (1890).\
\
H.A. Herbert, _Why the Solid South_.\
\
W.G. Brown, _The Lower South_.\
\
E.G. Murphy, _Problems of the Present South_.\
\
B.T. Washington, _The Negro Problem_; _The Story of the Negro_; _The\
Future of the Negro_.\
\
A.B. Hart, _The Southern South_ and R.S. Baker, _Following the Color\
Line_ (two works by Northern writers).\
\
T.N. Page, _The Negro, the Southerner's Problem_.\
\
\
=Questions=\
\
1. Give the three main subdivisions of the chapter.\
\
2. Compare the condition of the South in 1865 with that of the North.\
Compare with the condition of the United States at the close of the\
Revolutionary War. At the close of the World War in 1918.\
\
3. Contrast the enfranchisement of the slaves with the enfranchisement\
of white men fifty years earlier.\
\
4. What was the condition of the planters as compared with that of the\
Northern manufacturers?\
\
5. How does money capital contribute to prosperity? Describe the plight\
of Southern finance.\
\
6. Give the chief steps in the restoration of white supremacy.\
\
7. Do you know of any other societies to compare with the Ku Klux Klan?\
\
8. Give Lincoln's plan for amnesty. What principles do you think should\
govern the granting of amnesty?\
\
9. How were the "Force bills" overcome?\
\
10. Compare the fourteenth and fifteenth amendments with regard to the\
suffrage provisions.\
\
11. Explain how they may be circumvented.\
\
12. Account for the Solid South. What was the situation before 1860?\
\
13. In what ways did Southern agriculture tend to become like that of\
the North? What were the social results?\
\
14. Name the chief results of an "industrial revolution" in general. In\
the South, in particular.\
\
15. What courses were open to freedmen in 1865?\
\
16. Give the main features in the economic and social status of the\
colored population in the South.\
\
17. Explain why the race question is national now, rather than\
sectional.\
\
\
\
=Research Topics=\
\
=Amnesty for Confederates.=--Study carefully the provisions of the\
fourteenth amendment in the Appendix. Macdonald, _Documentary Source\
Book of American History_, pp. 470 and 564. A plea for amnesty in\
Harding, _Select Orations Illustrating American History_, pp. 467-488.\
\
=Political Conditions in the South in 1868.=--Dunning, _Reconstruction,\
Political and Economic_ (American Nation Series), pp. 109-123; Hart,\
_American History Told by Contemporaries_, Vol. IV, pp. 445-458,\
497-500; Elson, _History of the United States_, pp. 799-805.\
\
=Movement for White Supremacy.=--Dunning, _Reconstruction_, pp. 266-280;\
Paxson, _The New Nation_ (Riverside Series), pp. 39-58; Beard, _American\
Government and Politics_, pp. 454-457.\
\
=The Withdrawal of Federal Troops from the South.=--Sparks, _National\
Development_ (American Nation Series), pp. 84-102; Rhodes, _History of\
the United States_, Vol. VIII, pp. 1-12.\
\
=Southern Industry.=--Paxson, _The New Nation_, pp. 192-207; T.M. Young,\
_The American Cotton Industry_, pp. 54-99.\
\
=The Race Question.=--B.T. Washington, _Up From Slavery_ (sympathetic\
presentation); A.H. Stone, _Studies in the American Race Problem_\
(coldly analytical); Hart, _Contemporaries_, Vol. IV, pp. 647-649,\
652-654, 663-669.\
\
\
\
\
CHAPTER XVII\
\
BUSINESS ENTERPRISE AND THE REPUBLICAN PARTY\
\
\
If a single phrase be chosen to characterize American life during the\
generation that followed the age of Douglas and Lincoln, it must be\
"business enterprise"--the tremendous, irresistible energy of a virile\
people, mounting in numbers toward a hundred million and applied without\
let or hindrance to the developing of natural resources of unparalleled\
richness. The chief goal of this effort was high profits for the\
captains of industry, on the one hand; and high wages for the workers,\
on the other. Its signs, to use the language of a Republican orator in\
1876, were golden harvest fields, whirling spindles, turning wheels,\
open furnace doors, flaming forges, and chimneys filled with eager fire.\
The device blazoned on its shield and written over its factory doors was\
"prosperity." A Republican President was its "advance agent." Released\
from the hampering interference of the Southern planters and the\
confusing issues of the slavery controversy, business enterprise sprang\
forward to the task of winning the entire country. Then it flung its\
outposts to the uttermost parts of the earth--Europe, Africa, and the\
Orient--where were to be found markets for American goods and natural\
resources for American capital to develop.\
\
\
RAILWAYS AND INDUSTRY\
\
=The Outward Signs of Enterprise.=--It is difficult to comprehend all\
the multitudinous activities of American business energy or to appraise\
its effects upon the life and destiny of the American people; for beyond\
the horizon of the twentieth century lie consequences as yet undreamed\
of in our poor philosophy. Statisticians attempt to record its\
achievements in terms of miles of railways built, factories opened, men\
and women employed, fortunes made, wages paid, cities founded, rivers\
spanned, boxes, bales, and tons produced. Historians apply standards of\
comparison with the past. Against the slow and leisurely stagecoach,\
they set the swift express, rushing from New York to San Francisco in\
less time than Washington consumed in his triumphal tour from Mt. Vernon\
to New York for his first inaugural. Against the lazy sailing vessel\
drifting before a genial breeze, they place the turbine steamer crossing\
the Atlantic in five days or the still swifter airplane, in fifteen\
hours. For the old workshop where a master and a dozen workmen and\
apprentices wrought by hand, they offer the giant factory where ten\
thousand persons attend the whirling wheels driven by steam. They write\
of the "romance of invention" and the "captains of industry."\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
A CORNER IN THE BETHLEHEM STEEL WORKS]\
\
=The Service of the Railway.=--All this is fitting in its way. Figures\
and contrasts cannot, however, tell the whole story. Take, for example,\
the extension of railways. It is easy to relate that there were 30,000\
miles in 1860; 166,000 in 1890; and 242,000 in 1910. It is easy to show\
upon the map how a few straggling lines became a perfect mesh of closely\
knitted railways; or how, like the tentacles of a great monster, the few\
roads ending in the Mississippi Valley in 1860 were extended and\
multiplied until they tapped every wheat field, mine, and forest beyond\
the valley. All this, eloquent of enterprise as it truly is, does not\
reveal the significance of railways for American life. It does not\
indicate how railways made a continental market for American goods; nor\
how they standardized the whole country, giving to cities on the\
advancing frontier the leading features of cities in the old East; nor\
how they carried to the pioneer the comforts of civilization; nor yet\
how in the West they were the forerunners of civilization, the makers of\
homesteads, the builders of states.\
\
=Government Aid for Railways.=--Still the story is not ended. The\
significant relation between railways and politics must not be\
overlooked. The bounty of a lavish government, for example, made\
possible the work of railway promoters. By the year 1872 the Federal\
government had granted in aid of railways 155,000,000 acres of land--an\
area estimated as almost equal to Pennsylvania, New York, Connecticut,\
Rhode Island, Massachusetts, Maine, New Hampshire, and Vermont. The\
Union Pacific Company alone secured from the federal government a free\
right of way through the public domain, twenty sections of land with\
each mile of railway, and a loan up to fifty millions of dollars secured\
by a second mortgage on the company's property. More than half of the\
northern tier of states lying against Canada from Lake Michigan to the\
Pacific was granted to private companies in aid of railways and wagon\
roads. About half of New Mexico, Arizona, and California was also given\
outright to railway companies. These vast grants from the federal\
government were supplemented by gifts from the states in land and by\
subscriptions amounting to more than two hundred million dollars. The\
history of these gifts and their relation to the political leaders that\
engineered them would alone fill a large and interesting volume.\
\
=Railway Fortunes and Capital.=--Out of this gigantic railway promotion,\
the first really immense American fortunes were made. Henry Adams, the\
grandson of John Quincy Adams, related that his grandfather on his\
mother's side, Peter Brooks, on his death in 1849, left a fortune of two\
million dollars, "supposed to be the largest estate in Boston," then one\
of the few centers of great riches. Compared with the opulence that\
sprang out of the Union Pacific, the Northern Pacific, the Southern\
Pacific, with their subsidiary and component lines, the estate of Peter\
Brooks was a poor man's heritage.\
\
The capital invested in these railways was enormous beyond the\
imagination of the men of the stagecoach generation. The total debt of\
the United States incurred in the Revolutionary War--a debt which those\
of little faith thought the country could never pay--was reckoned at a\
figure well under $75,000,000. When the Union Pacific Railroad was\
completed, there were outstanding against it $27,000,000 in first\
mortgage bonds, $27,000,000 in second mortgage bonds held by the\
government, $10,000,000 in income bonds, $10,000,000 in land grant\
bonds, and, on top of that huge bonded indebtedness, $36,000,000 in\
stock--making $110,000,000 in all. If the amount due the United States\
government be subtracted, still there remained, in private hands, stocks\
and bonds exceeding in value the whole national debt of Hamilton's\
day--a debt that strained all the resources of the Federal government in\
1790. Such was the financial significance of the railways.\
\
[Illustration: RAILROADS OF THE UNITED STATES IN 1918]\
\
=Growth and Extension of Industry.=--In the field of manufacturing,\
mining, and metal working, the results of business enterprise far\
outstripped, if measured in mere dollars, the results of railway\
construction. By the end of the century there were about ten billion\
dollars invested in factories alone and five million wage-earners\
employed in them; while the total value of the output, fourteen billion\
dollars, was fifteen times the figure for 1860. In the Eastern states\
industries multiplied. In the Northwest territory, the old home of\
Jacksonian Democracy, they overtopped agriculture. By the end of the\
century, Ohio had almost reached and Illinois had surpassed\
Massachusetts in the annual value of manufacturing output.\
\
That was not all. Untold wealth in the form of natural resources was\
discovered in the South and West. Coal deposits were found in the\
Appalachians stretching from Pennsylvania down to Alabama, in Michigan,\
in the Mississippi Valley, and in the Western mountains from North\
Dakota to New Mexico. In nearly every coal-bearing region, iron was also\
discovered and the great fields of Michigan, Wisconsin, and Minnesota\
soon rivaled those of the Appalachian area. Copper, lead, gold, and\
silver in fabulous quantities were unearthed by the restless prospectors\
who left no plain or mountain fastness unexplored. Petroleum, first\
pumped from the wells of Pennsylvania in the summer of 1859, made new\
fortunes equaling those of trade, railways, and land speculation. It\
scattered its riches with an especially lavish hand through Oklahoma,\
Texas, and California.\
\
=The Trust--an Instrument of Industrial Progress.=--Business enterprise,\
under the direction of powerful men working single-handed, or of small\
groups of men pooling their capital for one or more undertakings, had\
not advanced far before there appeared upon the scene still mightier\
leaders of even greater imagination. New constructive genius now brought\
together and combined under one management hundreds of concerns or\
thousands of miles of railways, revealing the magic strength of\
cooperation on a national scale. Price-cutting in oil, threatening ruin\
to those engaged in the industry, as early as 1879, led a number of\
companies in Cleveland, Pittsburgh, and Philadelphia to unite in\
price-fixing. Three years later a group of oil interests formed a close\
organization, placing all their stocks in the hands of trustees, among\
whom was John D. Rockefeller. The trustees, in turn, issued\
certificates representing the share to which each participant was\
entitled; and took over the management of the entire business. Such was\
the nature of the "trust," which was to play such an unique role in the\
progress of America.\
\
The idea of combination was applied in time to iron and steel, copper,\
lead, sugar, cordage, coal, and other commodities, until in each field\
there loomed a giant trust or corporation, controlling, if not most of\
the output, at least enough to determine in a large measure the prices\
charged to consumers. With the passing years, the railways, mills,\
mines, and other business concerns were transferred from individual\
owners to corporations. At the end of the nineteenth century, the whole\
face of American business was changed. Three-fourths of the output from\
industries came from factories under corporate management and only\
one-fourth from individual and partnership undertakings.\
\
[Illustration: JOHN D. ROCKEFELLER]\
\
=The Banking Corporation.=--Very closely related to the growth of\
business enterprise on a large scale was the system of banking. In the\
old days before banks, a person with savings either employed them in his\
own undertakings, lent them to a neighbor, or hid them away where they\
set no industry in motion. Even in the early stages of modern business,\
it was common for a manufacturer to rise from small beginnings by\
financing extensions out of his own earnings and profits. This state of\
affairs was profoundly altered by the growth of the huge corporations\
requiring millions and even billions of capital. The banks, once an\
adjunct to business, became the leaders in business.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
WALL STREET, NEW YORK CITY]\
\
It was the banks that undertook to sell the stocks and bonds issued by\
new corporations and trusts and to supply them with credit to carry on\
their operations. Indeed, many of the great mergers or combinations in\
business were initiated by magnates in the banking world with millions\
and billions under their control. Through their connections with one\
another, the banks formed a perfect network of agencies gathering up the\
pennies and dollars of the masses as well as the thousands of the rich\
and pouring them all into the channels of business and manufacturing.\
In this growth of banking on a national scale, it was inevitable that a\
few great centers, like Wall Street in New York or State Street in\
Boston, should rise to a position of dominance both in concentrating the\
savings and profits of the nation and in financing new as well as old\
corporations.\
\
=The Significance of the Corporation.=--The corporation, in fact, became\
the striking feature of American business life, one of the most\
marvelous institutions of all time, comparable in wealth and power and\
the number of its servants with kingdoms and states of old. The effect\
of its rise and growth cannot be summarily estimated; but some special\
facts are obvious. It made possible gigantic enterprises once entirely\
beyond the reach of any individual, no matter how rich. It eliminated\
many of the futile and costly wastes of competition in connection with\
manufacture, advertising, and selling. It studied the cheapest methods\
of production and shut down mills that were poorly equipped or\
disadvantageously located. It established laboratories for research in\
industry, chemistry, and mechanical inventions. Through the sale of\
stocks and bonds, it enabled tens of thousands of people to become\
capitalists, if only in a small way. The corporation made it possible\
for one person to own, for instance, a $50 share in a million dollar\
business concern--a thing entirely impossible under a regime of\
individual owners and partnerships.\
\
There was, of course, another side to the picture. Many of the\
corporations sought to become monopolies and to make profits, not by\
economies and good management, but by extortion from purchasers.\
Sometimes they mercilessly crushed small business men, their\
competitors, bribed members of legislatures to secure favorable laws,\
and contributed to the campaign funds of both leading parties. Wherever\
a trust approached the position of a monopoly, it acquired a dominion\
over the labor market which enabled it to break even the strongest trade\
unions. In short, the power of the trust in finance, in manufacturing,\
in politics, and in the field of labor control can hardly be measured.\
\
=The Corporation and Labor.=--In the development of the corporation\
there was to be observed a distinct severing of the old ties between\
master and workmen, which existed in the days of small industries. For\
the personal bond between the owner and the employees was substituted a\
new relation. "In most parts of our country," as President Wilson once\
said, "men work, not for themselves, not as partners in the old way in\
which they used to work, but generally as employees--in a higher or\
lower grade--of great corporations." The owner disappeared from the\
factory and in his place came the manager, representing the usually\
invisible stockholders and dependent for his success upon his ability to\
make profits for the owners. Hence the term "soulless corporation,"\
which was to exert such a deep influence on American thinking about\
industrial relations.\
\
=Cities and Immigration.=--Expressed in terms of human life, this era of\
unprecedented enterprise meant huge industrial cities and an immense\
labor supply, derived mainly from European immigration. Here, too,\
figures tell only a part of the story. In Washington's day nine-tenths\
of the American people were engaged in agriculture and lived in the\
country; in 1890 more than one-third of the population dwelt in towns of\
2500 and over; in 1920 more than half of the population lived in towns\
of over 2500. In forty years, between 1860 and 1900, Greater New York\
had grown from 1,174,000 to 3,437,000; San Francisco from 56,000 to\
342,000; Chicago from 109,000 to 1,698,000. The miles of city tenements\
began to rival, in the number of their residents, the farm homesteads of\
the West. The time so dreaded by Jefferson had arrived. People were\
"piled upon one another in great cities" and the republic of small\
farmers had passed away.\
\
To these industrial centers flowed annually an ever-increasing tide of\
immigration, reaching the half million point in 1880; rising to\
three-quarters of a million three years later; and passing the million\
mark in a single year at the opening of the new century. Immigration was\
as old as America but new elements now entered the situation. In the\
first place, there were radical changes in the nationality of the\
newcomers. The migration from Northern Europe--England, Ireland,\
Germany, and Scandinavia--diminished; that from Italy, Russia, and\
Austria-Hungary increased, more than three-fourths of the entire number\
coming from these three lands between the years 1900 and 1910. These\
later immigrants were Italians, Poles, Magyars, Czechs, Slovaks,\
Russians, and Jews, who came from countries far removed from the\
language and the traditions of England whence came the founders of\
America.\
\
In the second place, the reception accorded the newcomers differed from\
that given to the immigrants in the early days. By 1890 all the free\
land was gone. They could not, therefore, be dispersed widely among the\
native Americans to assimilate quickly and unconsciously the habits and\
ideas of American life. On the contrary, they were diverted mainly to\
the industrial centers. There they crowded--nay, overcrowded--into\
colonies of their own where they preserved their languages, their\
newspapers, and their old-world customs and views.\
\
So eager were American business men to get an enormous labor supply that\
they asked few questions about the effect of this "alien invasion" upon\
the old America inherited from the fathers. They even stimulated the\
invasion artificially by importing huge armies of foreigners under\
contract to work in specified mines and mills. There seemed to be no\
limit to the factories, forges, refineries, and railways that could be\
built, to the multitudes that could be employed in conquering a\
continent. As for the future, that was in the hands of Providence!\
\
=Business Theories of Politics.=--As the statesmen of Hamilton's school\
and the planters of Calhoun's had their theories of government and\
politics, so the leaders in business enterprise had theirs. It was\
simple and easily stated. "It is the duty of the government," they\
urged, "to protect American industry against foreign competition by\
means of high tariffs on imported goods, to aid railways by generous\
grants of land, to sell mineral and timber lands at low prices to\
energetic men ready to develop them, and then to leave the rest to the\
initiative and drive of individuals and companies." All government\
interference with the management, prices, rates, charges, and conduct of\
private business they held to be either wholly pernicious or intolerably\
impertinent. Judging from their speeches and writings, they conceived\
the nation as a great collection of individuals, companies, and labor\
unions all struggling for profits or high wages and held together by a\
government whose principal duty was to keep the peace among them and\
protect industry against the foreign manufacturer. Such was the\
political theory of business during the generation that followed the\
Civil War.\
\
\
THE SUPREMACY OF THE REPUBLICAN PARTY (1861-85)\
\
=Business Men and Republican Policies.=--Most of the leaders in industry\
gravitated to the Republican ranks. They worked in the North and the\
Republican party was essentially Northern. It was moreover--at least so\
far as the majority of its members were concerned--committed to\
protective tariffs, a sound monetary and banking system, the promotion\
of railways and industry by land grants, and the development of internal\
improvements. It was furthermore generous in its immigration policy. It\
proclaimed America to be an asylum for the oppressed of all countries\
and flung wide the doors for immigrants eager to fill the factories, man\
the mines, and settle upon Western lands. In a word the Republicans\
stood for all those specific measures which favored the enlargement and\
prosperity of business. At the same time they resisted government\
interference with private enterprise. They did not regulate railway\
rates, prosecute trusts for forming combinations, or prevent railway\
companies from giving lower rates to some shippers than to others. To\
sum it up, the political theories of the Republican party for three\
decades after the Civil War were the theories of American\
business--prosperous and profitable industries for the owners and "the\
full dinner pail" for the workmen. Naturally a large portion of those\
who flourished under its policies gave their support to it, voted for\
its candidates, and subscribed to its campaign funds.\
\
=Sources of Republican Strength in the North.=--The Republican party was\
in fact a political organization of singular power. It originated in a\
wave of moral enthusiasm, having attracted to itself, if not the\
abolitionists, certainly all those idealists, like James Russell Lowell\
and George William Curtis, who had opposed slavery when opposition was\
neither safe nor popular. To moral principles it added practical\
considerations. Business men had confidence in it. Workingmen, who\
longed for the independence of the farmer, owed to its indulgent land\
policy the opportunity of securing free homesteads in the West. The\
immigrant, landing penniless on these shores, as a result of the same\
beneficent system, often found himself in a little while with an estate\
as large as many a baronial domain in the Old World. Under a Republican\
administration, the union had been saved. To it the veterans of the war\
could turn with confidence for those rewards of service which the\
government could bestow: pensions surpassing in liberality anything that\
the world had ever seen. Under a Republican administration also the\
great debt had been created in the defense of the union, and to the\
Republican party every investor in government bonds could look for the\
full and honorable discharge of the interest and principal. The spoils\
system, inaugurated by Jacksonian Democracy, in turn placed all the\
federal offices in Republican hands, furnishing an army of party workers\
to be counted on for loyal service in every campaign.\
\
Of all these things Republican leaders made full and vigorous use,\
sometimes ascribing to the party, in accordance with ancient political\
usage, merits and achievements not wholly its own. Particularly was this\
true in the case of saving the union. "When in the economy of\
Providence, this land was to be purged of human slavery ... the\
Republican party came into power," ran a declaration in one platform.\
"The Republican party suppressed a gigantic rebellion, emancipated four\
million slaves, decreed the equal citizenship of all, and established\
universal suffrage," ran another. As for the aid rendered by the\
millions of Northern Democrats who stood by the union and the tens of\
thousands of them who actually fought in the union army, the Republicans\
in their zeal were inclined to be oblivious. They repeatedly charged the\
Democratic party "with being the same in character and spirit as when it\
sympathized with treason."\
\
=Republican Control of the South.=--To the strength enjoyed in the\
North, the Republicans for a long time added the advantages that came\
from control over the former Confederate states where the newly\
enfranchised negroes, under white leadership, gave a grateful support to\
the party responsible for their freedom. In this branch of politics,\
motives were so mixed that no historian can hope to appraise them all at\
their proper values. On the one side of the ledger must be set the\
vigorous efforts of the honest and sincere friends of the freedmen to\
win for them complete civil and political equality, wiping out not only\
slavery but all its badges of misery and servitude. On the same side\
must be placed the labor of those who had valiantly fought in forum and\
field to save the union and who regarded continued Republican supremacy\
after the war as absolutely necessary to prevent the former leaders in\
secession from coming back to power. At the same time there were\
undoubtedly some men of the baser sort who looked on politics as a game\
and who made use of "carpet-bagging" in the South to win the spoils that\
might result from it. At all events, both by laws and presidential acts,\
the Republicans for many years kept a keen eye upon the maintenance of\
their dominion in the South. Their declaration that neither the law nor\
its administration should admit any discrimination in respect of\
citizens by reason of race, color, or previous condition of servitude\
appealed to idealists and brought results in elections. Even South\
Carolina, where reposed the ashes of John C. Calhoun, went Republican in\
1872 by a vote of three to one!\
\
Republican control was made easy by the force bills described in a\
previous chapter--measures which vested the supervision of elections in\
federal officers appointed by Republican Presidents. These drastic\
measures, departing from American tradition, the Republican authors\
urged, were necessary to safeguard the purity of the ballot, not merely\
in the South where the timid freedman might readily be frightened from\
using it; but also in the North, particularly in New York City, where it\
was claimed that fraud was regularly practiced by Democratic leaders.\
\
The Democrats, on their side, indignantly denied the charges, replying\
that the force bills were nothing but devices created by the Republicans\
for the purpose of securing their continued rule through systematic\
interference with elections. Even the measures of reconstruction were\
deemed by Democratic leaders as thinly veiled schemes to establish\
Republican power throughout the country. "Nor is there the slightest\
doubt," exclaimed Samuel J. Tilden, spokesman of the Democrats in New\
York and candidate for President in 1876, "that the paramount object and\
motive of the Republican party is by these means to secure itself\
against a reaction of opinion adverse to it in our great populous\
Northern commonwealths.... When the Republican party resolved to\
establish negro supremacy in the ten states in order to gain to itself\
the representation of those states in Congress, it had to begin by\
governing the people of those states by the sword.... The next was the\
creation of new electoral bodies for those ten states, in which, by\
exclusions, by disfranchisements and proscriptions, by control over\
registration, by applying test oaths ... by intimidation and by every\
form of influence, three million negroes are made to predominate over\
four and a half million whites."\
\
=The War as a Campaign Issue.=--Even the repeal of force bills could not\
allay the sectional feelings engendered by the war. The Republicans\
could not forgive the men who had so recently been in arms against the\
union and insisted on calling them "traitors" and "rebels." The\
Southerners, smarting under the reconstruction acts, could regard the\
Republicans only as political oppressors. The passions of the war had\
been too strong; the distress too deep to be soon forgotten. The\
generation that went through it all remembered it all. For twenty\
years, the Republicans, in their speeches and platforms, made "a\
straight appeal to the patriotism of the Northern voters." They\
maintained that their party, which had saved the union and emancipated\
the slaves, was alone worthy of protecting the union and uplifting the\
freedmen.\
\
Though the Democrats, especially in the North, resented this policy and\
dubbed it with the expressive but inelegant phrase, "waving the bloody\
shirt," the Republicans refused to surrender a slogan which made such a\
ready popular appeal. As late as 1884, a leader expressed the hope that\
they might "wring one more President from the bloody shirt." They\
refused to let the country forget that the Democratic candidate, Grover\
Cleveland, had escaped military service by hiring a substitute; and they\
made political capital out of the fact that he had "insulted the\
veterans of the Grand Army of the Republic" by going fishing on\
Decoration Day.\
\
=Three Republican Presidents.=--Fortified by all these elements of\
strength, the Republicans held the presidency from 1869 to 1885. The\
three Presidents elected in this period, Grant, Hayes, and Garfield, had\
certain striking characteristics in common. They were all of origin\
humble enough to please the most exacting Jacksonian Democrat. They had\
been generals in the union army. Grant, next to Lincoln, was regarded as\
the savior of the Constitution. Hayes and Garfield, though lesser lights\
in the military firmament, had honorable records duly appreciated by\
veterans of the war, now thoroughly organized into the Grand Army of the\
Republic. It is true that Grant was not a politician and had never voted\
the Republican ticket; but this was readily overlooked. Hayes and\
Garfield on the other hand were loyal party men. The former had served\
in Congress and for three terms as governor of his state. The latter had\
long been a member of the House of Representatives and was Senator-elect\
when he received the nomination for President.\
\
All of them possessed, moreover, another important asset, which was not\
forgotten by the astute managers who led in selecting candidates. All\
of them were from Ohio--though Grant had been in Illinois when the\
summons to military duties came--and Ohio was a strategic state. It lay\
between the manufacturing East and the agrarian country to the West.\
Having growing industries and wool to sell it benefited from the\
protective tariff. Yet being mainly agricultural still, it was not\
\
without sympathy for the farmers who showed low tariff or free trade\
tendencies. Whatever share the East had in shaping laws and framing\
policies, it was clear that the West was to have the candidates. This\
division in privileges--not uncommon in political management--was always\
accompanied by a judicious selection of the candidate for Vice\
President. With Garfield, for example, was associated a prominent New\
York politician, Chester A. Arthur, who, as fate decreed, was destined\
to more than three years' service as chief magistrate, on the\
assassination of his superior in office.\
\
=The Disputed Election of 1876.=--While taking note of the long years of\
Republican supremacy, it must be recorded that grave doubts exist in the\
minds of many historians as to whether one of the three Presidents,\
Hayes, was actually the victor in 1876 or not. His Democratic opponent,\
Samuel J. Tilden, received a popular plurality of a quarter of a million\
and had a plausible claim to a majority of the electoral vote. At all\
events, four states sent in double returns, one set for Tilden and\
another for Hayes; and a deadlock ensued. Both parties vehemently\
claimed the election and the passions ran so high that sober men did not\
shrink from speaking of civil war again. Fortunately, in the end, the\
counsels of peace prevailed. Congress provided for an electoral\
commission of fifteen men to review the contested returns. The\
Democrats, inspired by Tilden's moderation, accepted the judgment in\
favor of Hayes even though they were not convinced that he was really\
entitled to the office.\
\
\
THE GROWTH OF OPPOSITION TO REPUBLICAN RULE\
\
=Abuses in American Political Life.=--During their long tenure of\
office, the Republicans could not escape the inevitable consequences of\
power; that is, evil practices and corrupt conduct on the part of some\
who found shelter within the party. For that matter neither did the\
Democrats manage to avoid such difficulties in those states and cities\
where they had the majority. In New York City, for instance, the local\
Democratic organization, known as Tammany Hall, passed under the sway of\
a group of politicians headed by "Boss" Tweed. He plundered the city\
treasury until public-spirited citizens, supported by Samuel J. Tilden,\
the Democratic leader of the state, rose in revolt, drove the ringleader\
from power, and sent him to jail. In Philadelphia, the local Republican\
bosses were guilty of offenses as odious as those committed by New York\
politicians. Indeed, the decade that followed the Civil War was marred\
by so many scandals in public life that one acute editor was moved to\
inquire: "Are not all the great communities of the Western World growing\
more corrupt as they grow in wealth?"\
\
In the sphere of national politics, where the opportunities were\
greater, betrayals of public trust were even more flagrant. One\
revelation after another showed officers, high and low, possessed with\
the spirit of peculation. Members of Congress, it was found, accepted\
railway stock in exchange for votes in favor of land grants and other\
concessions to the companies. In the administration as well as the\
legislature the disease was rife. Revenue officers permitted whisky\
distillers to evade their taxes and received heavy bribes in return. A\
probe into the post-office department revealed the malodorous "star\
route frauds"--the deliberate overpayment of certain mail carriers whose\
lines were indicated in the official record by asterisks or stars. Even\
cabinet officers did not escape suspicion, for the trail of the serpent\
led straight to the door of one of them.\
\
In the lower ranges of official life, the spoils system became more\
virulent as the number of federal employees increased. The holders of\
offices and the seekers after them constituted a veritable political\
army. They crowded into Republican councils, for the Republicans, being\
in power, could alone dispense federal favors. They filled positions in\
the party ranging from the lowest township committee to the national\
convention. They helped to nominate candidates and draft platforms and\
elbowed to one side the busy citizen, not conversant with party\
intrigues, who could only give an occasional day to political matters.\
Even the Civil Service Act of 1883, wrung from a reluctant Congress two\
years after the assassination of Garfield, made little change for a long\
time. It took away from the spoilsmen a few thousand government\
positions, but it formed no check on the practice of rewarding party\
workers from the public treasury.\
\
On viewing this state of affairs, many a distinguished citizen became\
profoundly discouraged. James Russell Lowell, for example, thought he\
saw a steady decline in public morals. In 1865, hearing of Lee's\
surrender, he had exclaimed: "There is something magnificent in having a\
country to love!" Ten years later, when asked to write an ode for the\
centennial at Philadelphia in 1876, he could think only of a biting\
satire on the nation:\
\
    "Show your state legislatures; show your Rings;\
     And challenge Europe to produce such things\
     As high officials sitting half in sight\
     To share the plunder and fix things right.\
     If that don't fetch her, why, you need only\
     To show your latest style in martyrs,--Tweed:\
     She'll find it hard to hide her spiteful tears\
     At such advance in one poor hundred years."\
\
When his critics condemned him for this "attack upon his native land,"\
Lowell replied in sadness: "These fellows have no notion of what love of\
country means. It was in my very blood and bones. If I am not an\
American who ever was?... What fills me with doubt and dismay is the\
degradation of the moral tone. Is it or is it not a result of democracy?\
Is ours a 'government of the people, by the people, for the people,' or\
a Kakistocracy [a government of the worst], rather for the benefit of\
knaves at the cost of fools?"\
\
=The Reform Movement in Republican Ranks.=--The sentiments expressed by\
Lowell, himself a Republican and for a time American ambassador to\
England, were shared by many men in his party. Very soon after the close\
of the Civil War some of them began to protest vigorously against the\
policies and conduct of their leaders. In 1872, the dissenters, calling\
themselves Liberal Republicans, broke away altogether, nominated a\
candidate of their own, Horace Greeley, and put forward a platform\
indicting the Republican President fiercely enough to please the most\
uncompromising Democrat. They accused Grant of using "the powers and\
opportunities of his high office for the promotion of personal ends."\
They charged him with retaining "notoriously corrupt and unworthy men in\
places of power and responsibility." They alleged that the Republican\
party kept "alive the passions and resentments of the late civil war to\
use them for their own advantages," and employed the "public service of\
the government as a machinery of corruption and personal influence."\
\
It was not apparent, however, from the ensuing election that any\
considerable number of Republicans accepted the views of the Liberals.\
Greeley, though indorsed by the Democrats, was utterly routed and died\
of a broken heart. The lesson of his discomfiture seemed to be that\
independent action was futile. So, at least, it was regarded by most men\
of the rising generation like Henry Cabot Lodge, of Massachusetts, and\
Theodore Roosevelt, of New York. Profiting by the experience of Greeley\
they insisted in season and out that reformers who desired to rid the\
party of abuses should remain loyal to it and do their work "on the\
inside."\
\
=The Mugwumps and Cleveland Democracy in 1884.=--Though aided by\
Republican dissensions, the Democrats were slow in making headway\
against the political current. They were deprived of the energetic and\
capable leadership once afforded by the planters, like Calhoun, Davis,\
and Toombs; they were saddled by their opponents with responsibility for\
secession; and they were stripped of the support of the prostrate\
South. Not until the last Southern state was restored to the union, not\
until a general amnesty was wrung from Congress, not until white\
supremacy was established at the polls, and the last federal soldier\
withdrawn from Southern capitals did they succeed in capturing the\
presidency.\
\
The opportune moment for them came in 1884 when a number of\
circumstances favored their aspirations. The Republicans, leaving the\
Ohio Valley in their search for a candidate, nominated James G. Blaine\
of Maine, a vigorous and popular leader but a man under fire from the\
reformers in his own party. The Democrats on their side were able to\
find at this juncture an able candidate who had no political enemies in\
the sphere of national politics, Grover Cleveland, then governor of New\
York and widely celebrated as a man of "sterling honesty." At the same\
time a number of dissatisfied Republicans openly espoused the Democratic\
cause,--among them Carl Schurz, George William Curtis, Henry Ward\
Beecher, and William Everett, men of fine ideals and undoubted\
integrity. Though the "regular" Republicans called them "Mugwumps" and\
laughed at them as the "men milliners, the dilettanti, and carpet\
knights of politics," they had a following that was not to be despised.\
\
The campaign which took place that year was one of the most savage in\
American history. Issues were thrust into the background. The tariff,\
though mentioned, was not taken seriously. Abuse of the opposition was\
the favorite resource of party orators. The Democrats insisted that "the\
Republican party so far as principle is concerned is a reminiscence. In\
practice it is an organization for enriching those who control its\
machinery." For the Republican candidate, Blaine, they could hardly find\
words to express their contempt. The Republicans retaliated in kind.\
They praised their own good works, as of old, in saving the union, and\
denounced the "fraud and violence practiced by the Democracy in the\
Southern states." Seeing little objectionable in the public record of\
Cleveland as mayor of Buffalo and governor of New York, they attacked\
his personal character. Perhaps never in the history of political\
campaigns did the discussions on the platform and in the press sink to\
so low a level. Decent people were sickened. Even hot partisans shrank\
from their own words when, after the election, they had time to reflect\
on their heedless passions. Moreover, nothing was decided by the\
balloting. Cleveland was elected, but his victory was a narrow one. A\
change of a few hundred votes in New York would have sent his opponent\
to the White House instead.\
\
=Changing Political Fortunes (1888-96).=--After the Democrats had\
settled down to the enjoyment of their hard-earned victory, President\
Cleveland in his message of 1887 attacked the tariff as "vicious,\
inequitable, and illogical"; as a system of taxation that laid a burden\
upon "every consumer in the land for the benefit of our manufacturers."\
Business enterprise was thoroughly alarmed. The Republicans\
characterized the tariff message as a free-trade assault upon the\
industries of the country. Mainly on that issue they elected in 1888\
Benjamin Harrison of Indiana, a shrewd lawyer, a reticent politician, a\
descendant of the hero of Tippecanoe, and a son of the old Northwest.\
Accepting the outcome of the election as a vindication of their\
principles, the Republicans, under the leadership of William McKinley in\
the House of Representatives, enacted in 1890 a tariff law imposing the\
highest duties yet laid in our history. To their utter surprise,\
however, they were instantly informed by the country that their program\
was not approved. That very autumn they lost in the congressional\
elections, and two years later they were decisively beaten in the\
presidential campaign, Cleveland once more leading his party to victory.\
\
\
=References=\
\
L.H. Haney, _Congressional History of Railways_ (2 vols.).\
\
J.P. Davis, _Union Pacific Railway_.\
\
J.M. Swank, _History of the Manufacture of Iron_.\
\
M.T. Copeland, _The Cotton Manufacturing Industry in the United States_\
(Harvard Studies).\
\
E.W. Bryce, _Progress of Invention in the Nineteenth Century_.\
\
Ida Tarbell, _History of the Standard Oil Company_ (Critical).\
\
G.H. Montague, _Rise and Progress of the Standard Oil Company_\
(Friendly).\
\
H.P. Fairchild, _Immigration_, and F.J. Warne, _The Immigrant Invasion_\
(Both works favor exclusion).\
\
I.A. Hourwich, _Immigration_ (Against exclusionist policies).\
\
J.F. Rhodes, _History of the United States, 1877-1896_, Vol. VIII.\
\
Edward Stanwood, _A History of the Presidency_, Vol. I, for the\
presidential elections of the period.\
\
\
=Questions=\
\
1. Contrast the state of industry and commerce at the close of the Civil\
War with its condition at the close of the Revolutionary War.\
\
2. Enumerate the services rendered to the nation by the railways.\
\
3. Explain the peculiar relation of railways to government.\
\
4. What sections of the country have been industrialized?\
\
5. How do you account for the rise and growth of the trusts? Explain\
some of the economic advantages of the trust.\
\
6. Are the people in cities more or less independent than the farmers?\
What was Jefferson's view?\
\
7. State some of the problems raised by unrestricted immigration.\
\
8. What was the theory of the relation of government to business in this\
period? Has it changed in recent times?\
\
9. State the leading economic policies sponsored by the Republican\
party.\
\
10. Why were the Republicans especially strong immediately after the\
Civil War?\
\
11. What illustrations can you give showing the influence of war in\
American political campaigns?\
\
12. Account for the strength of middle-western candidates.\
\
13. Enumerate some of the abuses that appeared in American political\
life after 1865.\
\
14. Sketch the rise and growth of the reform movement.\
\
15. How is the fluctuating state of public opinion reflected in the\
elections from 1880 to 1896?\
\
\
=Research Topics=\
\
=Invention, Discovery, and Transportation.=--Sparks, _National\
Development_ (American Nation Series), pp. 37-67; Bogart, _Economic\
History of the United States_, Chaps. XXI, XXII, and XXIII.\
\
=Business and Politics.=--Paxson, _The New Nation_ (Riverside Series),\
pp. 92-107; Rhodes, _History of the United States_, Vol. VII, pp. 1-29,\
64-73, 175-206; Wilson, _History of the American People_, Vol. IV, pp.\
78-96.\
\
=Immigration.=--Coman, _Industrial History of the United States_ (2d\
ed.), pp. 369-374; E.L. Bogart, _Economic History of the United States_,\
pp. 420-422, 434-437; Jenks and Lauck, _Immigration Problems_, Commons,\
_Races and Immigrants_.\
\
=The Disputed Election of 1876.=--Haworth, _The United States in Our Own\
Time_, pp. 82-94; Dunning, _Reconstruction, Political and Economic_\
(American Nation Series), pp. 294-341; Elson, _History of the United\
States_, pp. 835-841.\
\
=Abuses in Political Life.=--Dunning, _Reconstruction_, pp. 281-293; see\
criticisms in party platforms in Stanwood, _History of the Presidency_,\
Vol. I; Bryce, _American Commonwealth_ (1910 ed.), Vol. II, pp. 379-448;\
136-167.\
\
=Studies of Presidential Administrations.=--(_a_) Grant, (_b_) Hayes,\
(_c_) Garfield-Arthur, (_d_) Cleveland, and (_e_) Harrison, in Haworth,\
_The United States in Our Own Time_, or in Paxson, _The New Nation_\
(Riverside Series), or still more briefly in Elson.\
\
=Cleveland Democracy.=--Haworth, _The United States_, pp. 164-183;\
Rhodes, _History of the United States_, Vol. VIII, pp. 240-327; Elson,\
pp. 857-887.\
\
=Analysis of Modern Immigration Problems.=--_Syllabus in History_ (New\
York State, 1919), pp. 110-112.\
\
\
\
\
CHAPTER XVIII\
\
THE DEVELOPMENT OF THE GREAT WEST\
\
\
At the close of the Civil War, Kansas and Texas were sentinel states on\
the middle border. Beyond the Rockies, California, Oregon, and Nevada\
stood guard, the last of them having been just admitted to furnish\
another vote for the fifteenth amendment abolishing slavery. Between the\
near and far frontiers lay a vast reach of plain, desert, plateau, and\
mountain, almost wholly undeveloped. A broad domain, extending from\
Canada to Mexico, and embracing the regions now included in Washington,\
Idaho, Wyoming, Montana, Utah, Arizona, New Mexico, the Dakotas, and\
Oklahoma, had fewer than half a million inhabitants. It was laid out\
into territories, each administered under a governor appointed by the\
President and Senate and, as soon as there was the requisite number of\
inhabitants, a legislature elected by the voters. No railway line\
stretched across the desert. St. Joseph on the Missouri was the terminus\
of the Eastern lines. It required twenty-five days for a passenger to\
make the overland journey to California by the stagecoach system,\
established in 1858, and more than ten days for the swift pony express,\
organized in 1860, to carry a letter to San Francisco. Indians still\
roamed the plain and desert and more than one powerful tribe disputed\
the white man's title to the soil.\
\
\
THE RAILWAYS AS TRAIL BLAZERS\
\
=Opening Railways to the Pacific.=--A decade before the Civil War the\
importance of rail connection between the East and the Pacific Coast had\
been recognized. Pressure had already been brought to bear on Congress\
to authorize the construction of a line and to grant land and money in\
its aid. Both the Democrats and Republicans approved the idea, but it\
was involved in the slavery controversy. Indeed it was submerged in it.\
Southern statesmen wanted connections between the Gulf and the Pacific\
through Texas, while Northerners stood out for a central route.\
\
The North had its way during the war. Congress, by legislation initiated\
in 1862, provided for the immediate organization of companies to build a\
line from the Missouri River to California and made grants of land and\
loans of money to aid in the enterprise. The Western end, the Central\
Pacific, was laid out under the supervision of Leland Stanford. It was\
heavily financed by the Mormons of Utah and also by the state\
government, the ranchmen, miners, and business men of California; and it\
was built principally by Chinese labor. The Eastern end, the Union\
Pacific, starting at Omaha, was constructed mainly by veterans of the\
Civil War and immigrants from Ireland and Germany. In 1869 the two\
companies met near Ogden in Utah and the driving of the last spike,\
uniting the Atlantic and the Pacific, was the occasion of a great\
demonstration.\
\
Other lines to the Pacific were projected at the same time; but the\
panic of 1873 checked railway enterprise for a while. With the revival\
of prosperity at the end of that decade, construction was renewed with\
vigor and the year 1883 marked a series of railway triumphs. In February\
trains were running from New Orleans through Houston, San Antonio, and\
Yuma to San Francisco, as a result of a union of the Texas Pacific with\
the Southern Pacific and its subsidiary corporations. In September the\
last spike was driven in the Northern Pacific at Helena, Montana. Lake\
Superior was connected with Puget Sound. The waters explored by Joliet\
and Marquette were joined to the waters plowed by Sir Francis Drake\
while he was searching for a route around the world. That same year also\
a third line was opened to the Pacific by way of the Atchison, Topeka\
and Santa Fe, making connections through Albuquerque and Needles with\
San Francisco. The fondest hopes of railway promoters seemed to be\
realized.\
\
[Illustration: UNITED STATES IN 1870]\
\
=Western Railways Precede Settlement.=--In the Old World and on our\
Atlantic seaboard, railways followed population and markets. In the Far\
West, railways usually preceded the people. Railway builders planned\
cities on paper before they laid tracks connecting them. They sent\
missionaries to spread the gospel of "Western opportunity" to people in\
the Middle West, in the Eastern cities, and in Southern states. Then\
they carried their enthusiastic converts bag and baggage in long trains\
to the distant Dakotas and still farther afield. So the development of\
the Far West was not left to the tedious processes of time. It was\
pushed by men of imagination--adventurers who made a romance of\
money-making and who had dreams of empire unequaled by many kings of the\
past.\
\
These empire builders bought railway lands in huge tracts; they got more\
from the government; they overcame every obstacle of canon, mountain,\
and stream with the aid of science; they built cities according to the\
plans made by the engineers. Having the towns ready and railway and\
steamboat connections formed with the rest of the world, they carried\
out the people to use the railways, the steamships, the houses, and the\
land. It was in this way that "the frontier speculator paved the way for\
the frontier agriculturalist who had to be near a market before he could\
farm." The spirit of this imaginative enterprise, which laid out\
railways and towns in advance of the people, is seen in an advertisement\
of that day: "This extension will run 42 miles from York, northeast\
through the Island Lake country, and will have five good North Dakota\
towns. The stations on the line will be well equipped with elevators and\
will be constructed and ready for operation at the commencement of the\
grain season. Prospective merchants have been active in securing\
desirable locations at the different towns on the line. There are still\
opportunities for hotels, general merchandise, hardware, furniture, and\
drug stores, etc."\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
A TOWN ON THE PRAIRIE]\
\
Among the railway promoters and builders in the West, James J. Hill,\
of the Great Northern and allied lines, was one of the most forceful\
figures. He knew that tracks and trains were useless without passengers\
and freight; without a population of farmers and town dwellers. He\
therefore organized publicity in the Virginias, Iowa, Ohio, Indiana,\
Illinois, Wisconsin, and Nebraska especially. He sent out agents to tell\
the story of Western opportunity in this vein: "You see your children\
come out of school with no chance to get farms of their own because the\
cost of land in your older part of the country is so high that you can't\
afford to buy land to start your sons out in life around you. They have\
to go to the cities to make a living or become laborers in the mills or\
hire out as farm hands. There is no future for them there. If you are\
doing well where you are and can safeguard the future of your children\
and see them prosper around you, don't leave here. But if you want\
independence, if you are renting your land, if the money-lender is\
carrying you along and you are running behind year after year, you can\
do no worse by moving.... You farmers talk of free trade and protection\
and what this or that political party will do for you. Why don't you\
vote a homestead for yourself? That is the only thing Uncle Sam will\
ever give you. Jim Hill hasn't an acre of land to sell you. We are not\
in the real estate business. We don't want you to go out West and make a\
failure of it because the rates at which we haul you and your goods make\
the first transaction a loss.... We must have landless men for a manless\
land."\
\
Unlike steamship companies stimulating immigration to get the fares,\
Hill was seeking permanent settlers who would produce, manufacture, and\
use the railways as the means of exchange. Consequently he fixed low\
rates and let his passengers take a good deal of live stock and\
household furniture free. By doing this he made an appeal that was\
answered by eager families. In 1894 the vanguard of home seekers left\
Indiana in fourteen passenger coaches, filled with men, women, and\
children, and forty-eight freight cars carrying their household goods\
and live stock. In the ten years that followed, 100,000 people from the\
Middle West and the South, responding to his call, went to the Western\
country where they brought eight million acres of prairie land under\
cultivation.\
\
When Hill got his people on the land, he took an interest in everything\
that increased the productivity of their labor. Was the output of food\
for his freight cars limited by bad drainage on the farms? Hill then\
interested himself in practical ways of ditching and tiling. Were\
farmers hampered in hauling their goods to his trains by bad roads? In\
that case, he urged upon the states the improvement of highways. Did the\
traffic slacken because the food shipped was not of the best quality?\
Then live stock must be improved and scientific farming promoted. Did\
the farmers need credit? Banks must be established close at hand to\
advance it. In all conferences on scientific farm management,\
conservation of natural resources, banking and credit in relation to\
agriculture and industry, Hill was an active participant. His was the\
long vision, seeing in conservation and permanent improvements the\
foundation of prosperity for the railways and the people.\
\
Indeed, he neglected no opportunity to increase the traffic on the\
lines. He wanted no empty cars running in either direction and no wheat\
stored in warehouses for the lack of markets. So he looked to the Orient\
as well as to Europe as an outlet for the surplus of the farms. He sent\
agents to China and Japan to discover what American goods and produce\
those countries would consume and what manufactures they had to offer to\
Americans in exchange. To open the Pacific trade he bought two ocean\
monsters, the _Minnesota_ and the _Dakota_, thus preparing for\
emergencies West as well as East. When some Japanese came to the United\
States on their way to Europe to buy steel rails, Hill showed them how\
easy it was for them to make their purchase in this country and ship by\
way of American railways and American vessels. So the railway builder\
and promoter, who helped to break the virgin soil of the prairies, lived\
through the pioneer epoch and into the age of great finance. Before he\
died he saw the wheat fields of North Dakota linked with the spinning\
jennies of Manchester and the docks of Yokohama.\
\
\
THE EVOLUTION OF GRAZING AND AGRICULTURE\
\
=The Removal of the Indians.=--Unlike the frontier of New England in\
colonial days or that of Kentucky later, the advancing lines of home\
builders in the Far West had little difficulty with warlike natives.\
Indian attacks were made on the railway construction gangs; General\
Custer had his fatal battle with the Sioux in 1876 and there were minor\
brushes; but they were all of relatively slight consequence. The former\
practice of treating with the Indians as independent nations was\
abandoned in 1871 and most of them were concentrated in reservations\
where they were mainly supported by the government. The supervision of\
their affairs was vested in a board of commissioners created in 1869 and\
instructed to treat them as wards of the nation--a trust which\
unfortunately was often betrayed. A further step in Indian policy was\
taken in 1887 when provision was made for issuing lands to individual\
Indians, thus permitting them to become citizens and settle down among\
their white neighbors as farmers or cattle raisers. The disappearance of\
the buffalo, the main food supply of the wild Indians, had made them\
more tractable and more willing to surrender the freedom of the hunter\
for the routine of the reservation, ranch, or wheat field.\
\
=The Cowboy and Cattle Ranger.=--Between the frontier of farms and the\
mountains were plains and semi-arid regions in vast reaches suitable for\
grazing. As soon as the railways were open into the Missouri Valley,\
affording an outlet for stock, there sprang up to the westward cattle\
and sheep raising on an immense scale. The far-famed American cowboy was\
the hero in this scene. Great herds of cattle were bred in Texas; with\
the advancing spring and summer seasons, they were driven northward\
across the plains and over the buffalo trails. In a single year, 1884,\
it is estimated that nearly one million head of cattle were moved out of\
Texas to the North by four thousand cowboys, supplied with 30,000\
horses and ponies.\
\
During the two decades from 1870 to 1890 both the cattle men and the\
sheep raisers had an almost free run of the plains, using public lands\
without paying for the privilege and waging war on one another over the\
possession of ranges. At length, however, both had to go, as the\
homesteaders and land companies came and fenced in the plain and desert\
with endless lines of barbed wire. Already in 1893 a writer familiar\
with the frontier lamented the passing of the picturesque days: "The\
unique position of the cowboys among the Americans is jeopardized in a\
thousand ways. Towns are growing up on their pasture lands; irrigation\
schemes of a dozen sorts threaten to turn bunch-grass scenery into\
farm-land views; farmers are pre-empting valleys and the sides of\
waterways; and the day is not far distant when stock-raising must be\
done mainly in small herds, with winter corrals, and then the cowboy's\
days will end. Even now his condition disappoints those who knew him\
only half a dozen years ago. His breed seems to have deteriorated and\
his ranks are filling with men who work for wages rather than for the\
love of the free life and bold companionship that once tempted men into\
that calling. Splendid Cheyenne saddles are less and less numerous in\
the outfits; the distinctive hat that made its way up from Mexico may or\
may not be worn; all the civil authorities in nearly all towns in the\
grazing country forbid the wearing of side arms; nobody shoots up these\
towns any more. The fact is the old simon-pure cowboy days are gone\
already."\
\
=Settlement under the Homestead Act of 1862.=--Two factors gave a\
special stimulus to the rapid settlement of Western lands which swept\
away the Indians and the cattle rangers. The first was the policy of the\
railway companies in selling large blocks of land received from the\
government at low prices to induce immigration. The second was the\
operation of the Homestead law passed in 1862. This measure practically\
closed the long controversy over the disposition of the public domain\
that was suitable for agriculture. It provided for granting, without any\
cost save a small registration fee, public lands in lots of 160 acres\
each to citizens and aliens who declared their intention of becoming\
citizens. The one important condition attached was that the settler\
should occupy the farm for five years before his title was finally\
confirmed. Even this stipulation was waived in the case of the Civil War\
veterans who were allowed to count their term of military service as a\
part of the five years' occupancy required. As the soldiers of the\
Revolutionary and Mexican wars had advanced in great numbers to the\
frontier in earlier days, so now veterans led in the settlement of the\
middle border. Along with them went thousands of German, Irish, and\
Scandinavian immigrants, fresh from the Old World. Between 1867 and\
1874, 27,000,000 acres were staked out in quarter-section farms. In\
twenty years (1860-80), the population of Nebraska leaped from 28,000 to\
almost half a million; Kansas from 100,000 to a million; Iowa from\
600,000 to 1,600,000; and the Dakotas from 5000 to 140,000.\
\
=The Diversity of Western Agriculture.=--In soil, produce, and\
management, Western agriculture presented many contrasts to that of the\
East and South. In the region of arable and watered lands the typical\
American unit--the small farm tilled by the owner--appeared as usual;\
but by the side of it many a huge domain owned by foreign or Eastern\
companies and tilled by hired labor. Sometimes the great estate took the\
shape of the "bonanza farm" devoted mainly to wheat and corn and\
cultivated on a large scale by machinery. Again it assumed the form of\
the cattle ranch embracing tens of thousands of acres. Again it was a\
vast holding of diversified interest, such as the Santa Anita ranch near\
Los Angeles, a domain of 60,000 acres "cultivated in a glorious sweep of\
vineyards and orange and olive orchards, rich sheep and cattle pastures\
and horse ranches, their life and customs handed down from the Spanish\
owners of the various ranches which were swept into one estate."\
\
=Irrigation.=--In one respect agriculture in the Far West was unique. In\
a large area spreading through eight states, Montana, Idaho, Wyoming,\
Utah, Colorado, Nevada, Arizona, New Mexico, and parts of adjoining\
states, the rainfall was so slight that the ordinary crops to which the\
American farmer was accustomed could not be grown at all. The Mormons\
were the first Anglo-Saxons to encounter aridity, and they were baffled\
at first; but they studied it and mastered it by magnificent irrigation\
systems. As other settlers poured into the West the problem of the\
desert was attacked with a will, some of them replying to the\
commiseration of Eastern farmers by saying that it was easier to scoop\
out an irrigation ditch than to cut forests and wrestle with stumps and\
stones. Private companies bought immense areas at low prices, built\
irrigation works, and disposed of their lands in small plots. Some\
ranchers with an instinct for water, like that of the miner for metal,\
sank wells into the dry sand and were rewarded with gushers that "soused\
the thirsty desert and turned its good-for-nothing sand into\
good-for-anything loam." The federal government came to the aid of the\
arid regions in 1894 by granting lands to the states to be used for\
irrigation purposes. In this work Wyoming took the lead with a law which\
induced capitalists to invest in irrigation and at the same time\
provided for the sale of the redeemed lands to actual settlers. Finally\
in 1902 the federal government by its liberal Reclamation Act added its\
strength to that of individuals, companies, and states in conquering\
"arid America."\
\
"Nowhere," writes Powell, a historian of the West, in his picturesque\
_End of the Trail_, "has the white man fought a more courageous fight or\
won a more brilliant victory than in Arizona. His weapons have been the\
transit and the level, the drill and the dredge, the pick and the spade;\
and the enemy which he has conquered has been the most stubborn of all\
foes--the hostile forces of Nature.... The story of how the white man\
within the space of less than thirty years penetrated, explored, and\
mapped this almost unknown region; of how he carried law, order, and\
justice into a section which had never had so much as a speaking\
acquaintance with any one of the three before; of how, realizing the\
necessity for means of communication, he built highways of steel across\
this territory from east to west and from north to south; of how,\
undismayed by the savageness of the countenance which the desert turned\
upon him, he laughed and rolled up his sleeves, and spat upon his hands,\
and slashed the face of the desert with canals and irrigating ditches,\
and filled those ditches with water brought from deep in the earth or\
high in the mountains; and of how, in the conquered and submissive soil,\
he replaced the aloe with alfalfa, the mesquite with maize, the cactus\
with cotton, forms one of the most inspiring chapters in our history. It\
is one of the epics of civilization, this reclamation of the Southwest,\
and its heroes, thank God, are Americans.\
\
"Other desert regions have been redeemed by irrigation--Egypt, for\
example, and Mesopotamia and parts of the Sudan--but the people of all\
those regions lay stretched out in the shade of a convenient palm,\
metaphorically speaking, and waited for some one with more energy than\
themselves to come along and do the work. But the Arizonians, mindful of\
the fact that God, the government, and Carnegie help those who help\
themselves, spent their days wielding the pick and shovel, and their\
evenings in writing letters to Washington with toil-hardened hands.\
After a time the government was prodded into action and the great dams\
at Laguna and Roosevelt are the result. Then the people, organizing\
themselves into cooperative leagues and water-users' associations, took\
up the work of reclamation where the government left off; it is to these\
energetic, persevering men who have drilled wells, plowed fields, and\
dug ditches through the length and breadth of that great region which\
stretches from Yuma to Tucson, that the metamorphosis of Arizona is\
due."\
\
The effect of irrigation wherever introduced was amazing. Stretches of\
sand and sagebrush gave way to fertile fields bearing crops of wheat,\
corn, fruits, vegetables, and grass. Huge ranches grazed by browsing\
sheep were broken up into small plots. The cowboy and ranchman vanished.\
In their place rose the prosperous community--a community unlike the\
township of Iowa or the industrial center of the East. Its intensive\
tillage left little room for hired labor. Its small holdings drew\
families together in village life rather than dispersing them on the\
lonely plain. Often the development of water power in connection with\
irrigation afforded electricity for labor-saving devices and lifted many\
a burden that in other days fell heavily upon the shoulders of the\
farmer and his family.\
\
\
MINING AND MANUFACTURING IN THE WEST\
\
=Mineral Resources.=--In another important particular the Far West\
differed from the Mississippi Valley states. That was in the\
predominance of mining over agriculture throughout a vast section.\
Indeed it was the minerals rather than the land that attracted the\
pioneers who first opened the country. The discovery of gold in\
California in 1848 was the signal for the great rush of prospectors,\
miners, and promoters who explored the valleys, climbed the hills,\
washed the sands, and dug up the soil in their feverish search for gold,\
silver, copper, coal, and other minerals. In Nevada and Montana the\
development of mineral resources went on all during the Civil War. Alder\
Gulch became Virginia City in 1863; Last Chance Gulch was named Helena\
in 1864; and Confederate Gulch was christened Diamond City in 1865. At\
Butte the miners began operations in 1864 and within five years had\
washed out eight million dollars' worth of gold. Under the gold they\
found silver; under silver they found copper.\
\
Even at the end of the nineteenth century, after agriculture was well\
advanced and stock and sheep raising introduced on a large scale,\
minerals continued to be the chief source of wealth in a number of\
states. This was revealed by the figures for 1910. The gold, silver,\
iron, and copper of Colorado were worth more than the wheat, corn, and\
oats combined; the copper of Montana sold for more than all the cereals\
and four times the price of the wheat. The interest of Nevada was also\
mainly mining, the receipts from the mineral output being $43,000,000 or\
more than one-half the national debt of Hamilton's day. The yield of the\
mines of Utah was worth four or five times the wheat crop; the coal of\
Wyoming brought twice as much as the great wool clip; the minerals of\
Arizona were totaled at $43,000,000 as against a wool clip reckoned at\
$1,200,000; while in Idaho alone of this group of states did the wheat\
crop exceed in value the output of the mines.\
\
[Illustration: _Photograph from Underwood and Underwood, N.Y._\
\
LOGGING]\
\
=Timber Resources.=--The forests of the great West, unlike those of the\
Ohio Valley, proved a boon to the pioneers rather than a foe to be\
attacked. In Ohio and Indiana, for example, the frontier line of\
homemakers had to cut, roll, and burn thousands of trees before they\
could put out a crop of any size. Beyond the Mississippi, however,\
there were all ready for the breaking plow great reaches of almost\
treeless prairie, where every stick of timber was precious. In the other\
parts, often rough and mountainous, where stood primeval forests of the\
finest woods, the railroads made good use of the timber. They consumed\
acres of forests themselves in making ties, bridge timbers, and\
telegraph poles, and they laid a heavy tribute upon the forests for\
their annual upkeep. The surplus trees, such as had burdened the\
pioneers of the Northwest Territory a hundred years before, they carried\
off to markets on the east and west coasts.\
\
=Western Industries.=--The peculiar conditions of the Far West\
stimulated a rise of industries more rapid than is usual in new country.\
The mining activities which in many sections preceded agriculture called\
for sawmills to furnish timber for the mines and smelters to reduce and\
refine ores. The ranches supplied sheep and cattle for the packing\
houses of Kansas City as well as Chicago. The waters of the Northwest\
afforded salmon for 4000 cases in 1866 and for 1,400,000 cases in 1916.\
The fruits and vegetables of California brought into existence\
innumerable canneries. The lumber industry, starting with crude sawmills\
to furnish rough timbers for railways and mines, ended in specialized\
factories for paper, boxes, and furniture. As the railways preceded\
settlement and furnished a ready outlet for local manufactures, so they\
encouraged the early establishment of varied industries, thus creating a\
state of affairs quite unlike that which obtained in the Ohio Valley in\
the early days before the opening of the Erie Canal.\
\
=Social Effects of Economic Activities.=--In many respects the social\
life of the Far West also differed from that of the Ohio Valley. The\
treeless prairies, though open to homesteads, favored the great estate\
tilled in part by tenant labor and in part by migratory seasonal labor,\
summoned from all sections of the country for the harvests. The mineral\
resources created hundreds of huge fortunes which made the accumulations\
of eastern mercantile families look trivial by comparison. Other\
millionaires won their fortunes in the railway business and still more\
from the cattle and sheep ranges. In many sections the "cattle king," as\
he was called, was as dominant as the planter had been in the old South.\
Everywhere in the grazing country he was a conspicuous and important\
person. He "sometimes invested money in banks, in railroad stocks, or in\
city property.... He had his rating in the commercial reviews and could\
hobnob with bankers, railroad presidents, and metropolitan merchants....\
He attended party caucuses and conventions, ran for the state\
legislature, and sometimes defeated a lawyer or metropolitan 'business\
man' in the race for a seat in Congress. In proportion to their numbers,\
the ranchers ... have constituted a highly impressive class."\
\
Although many of the early capitalists of the great West, especially\
from Nevada, spent their money principally in the East, others took\
leadership in promoting the sections in which they had made their\
fortunes. A railroad pioneer, General Palmer, built his home at Colorado\
Springs, founded the town, and encouraged local improvements. Denver\
owed its first impressive buildings to the civic patriotism of Horace\
Tabor, a wealthy mine owner. Leland Stanford paid his tribute to\
California in the endowment of a large university. Colonel W.F. Cody,\
better known as "Buffalo Bill," started his career by building a "boom\
town" which collapsed, and made a large sum of money supplying buffalo\
meat to construction hands (hence his popular name). By his famous Wild\
West Show, he increased it to a fortune which he devoted mainly to the\
promotion of a western reclamation scheme.\
\
While the Far West was developing this vigorous, aggressive leadership\
in business, a considerable industrial population was springing up. Even\
the cattle ranges and hundreds of farms were conducted like factories in\
that they were managed through overseers who hired plowmen, harvesters,\
and cattlemen at regular wages. At the same time there appeared other\
peculiar features which made a lasting impression on western economic\
life. Mining, lumbering, and fruit growing, for instance, employed\
thousands of workers during the rush months and turned them out at other\
times. The inevitable result was an army of migratory laborers wandering\
from camp to camp, from town to town, and from ranch to ranch, without\
fixed homes or established habits of life. From this extraordinary\
condition there issued many a long and lawless conflict between capital\
and labor, giving a distinct color to the labor movement in whole\
sections of the mountain and coast states.\
\
\
THE ADMISSION OF NEW STATES\
\
=The Spirit of Self-Government.=--The instinct of self-government was\
strong in the western communities. In the very beginning, it led to the\
organization of volunteer committees, known as "vigilantes," to suppress\
crime and punish criminals. As soon as enough people were settled\
permanently in a region, they took care to form a more stable kind of\
government. An illustration of this process is found in the Oregon\
compact made by the pioneers in 1843, the spirit of which is reflected\
in an editorial in an old copy of the _Rocky Mountain News_: "We claim\
that any body or community of American citizens which from any cause or\
under any circumstances is cut off from or from isolation is so situated\
as not to be under any active and protecting branch of the central\
government, have a right, if on American soil, to frame a government and\
enact such laws and regulations as may be necessary for their own\
safety, protection, and happiness, always with the condition precedent,\
that they shall, at the earliest moment when the central government\
shall extend an effective organization and laws over them, give it their\
unqualified support and obedience."\
\
People who turned so naturally to the organization of local\
administration were equally eager for admission to the union as soon as\
any shadow of a claim to statehood could be advanced. As long as a\
region was merely one of the territories of the United States, the\
appointment of the governor and other officers was controlled by\
politics at Washington. Moreover the disposition of land, mineral\
rights, forests, and water power was also in the hands of national\
leaders. Thus practical considerations were united with the spirit of\
independence in the quest for local autonomy.\
\
=Nebraska and Colorado.=--Two states, Nebraska and Colorado, had little\
difficulty in securing admission to the union. The first, Nebraska, had\
been organized as a territory by the famous Kansas-Nebraska bill which\
did so much to precipitate the Civil War. Lying to the north of Kansas,\
which had been admitted in 1861, it escaped the invasion of slave owners\
from Missouri and was settled mainly by farmers from the North. Though\
it claimed a population of only 67,000, it was regarded with kindly\
interest by the Republican Congress at Washington and, reduced to its\
present boundaries, it received the coveted statehood in 1867.\
\
This was hardly accomplished before the people of Colorado to the\
southwest began to make known their demands. They had been organized\
under territorial government in 1861 when they numbered only a handful;\
but within ten years the aspect of their affairs had completely changed.\
The silver and gold deposits of the Leadville and Cripple Creek regions\
had attracted an army of miners and prospectors. The city of Denver,\
founded in 1858 and named after the governor of Kansas whence came many\
of the early settlers, had grown from a straggling camp of log huts into\
a prosperous center of trade. By 1875 it was reckoned that the\
population of the territory was not less than one hundred thousand; the\
following year Congress, yielding to the popular appeal, made Colorado a\
member of the American union.\
\
=Six New States (1889-1890).=--For many years there was a deadlock in\
Congress over the admission of new states. The spell was broken in 1889\
under the leadership of the Dakotas. For a long time the Dakota\
territory, organized in 1861, had been looked upon as the home of the\
powerful Sioux Indians whose enormous reservation blocked the advance of\
the frontier. The discovery of gold in the Black Hills, however, marked\
their doom. Even before Congress could open their lands to prospectors,\
pioneers were swarming over the country. Farmers from the adjoining\
Minnesota and the Eastern states, Scandinavians, Germans, and Canadians,\
came in swelling waves to occupy the fertile Dakota lands, now famous\
even as far away as the fjords of Norway. Seldom had the plow of man cut\
through richer soil than was found in the bottoms of the Red River\
Valley, and it became all the more precious when the opening of the\
Northern Pacific in 1883 afforded a means of transportation east and\
west. The population, which had numbered 135,000 in 1880, passed the\
half million mark before ten years had elapsed.\
\
Remembering that Nebraska had been admitted with only 67,000\
inhabitants, the Dakotans could not see why they should be kept under\
federal tutelage. At the same time Washington, far away on the Pacific\
Coast, Montana, Idaho, and Wyoming, boasting of their populations and\
their riches, put in their own eloquent pleas. But the members of\
Congress were busy with politics. The Democrats saw no good reason for\
admitting new Republican states until after their defeat in 1888. Near\
the end of their term the next year they opened the door for North and\
South Dakota, Washington, and Montana. In 1890, a Republican Congress\
brought Idaho and Wyoming into the union, the latter with woman\
suffrage, which had been granted twenty-one years before.\
\
=Utah.=--Although Utah had long presented all the elements of a\
well-settled and industrious community, its admission to the union was\
delayed on account of popular hostility to the practice of polygamy. The\
custom, it is true, had been prohibited by act of Congress in 1862; but\
the law had been systematically evaded. In 1882 Congress made another\
and more effective effort to stamp out polygamy. Five years later it\
even went so far as to authorize the confiscation of the property of the\
Mormon Church in case the practice of plural marriages was not stopped.\
Meanwhile the Gentile or non-Mormon population was steadily increasing\
and the leaders in the Church became convinced that the battle\
against the sentiment of the country was futile. At last in 1896 Utah\
was admitted as a state under a constitution which forbade plural\
marriages absolutely and forever. Horace Greeley, who visited Utah in\
1859, had prophesied that the Pacific Railroad would work a revolution\
in the land of Brigham Young. His prophecy had come true.\
\
[Illustration: THE UNITED STATES IN 1912]\
\
=Rounding out the Continent.=--Three more territories now remained out\
of the Union. Oklahoma, long an Indian reservation, had been opened for\
settlement to white men in 1889. The rush upon the fertile lands of this\
region, the last in the history of America, was marked by all the frenzy\
of the final, desperate chance. At a signal from a bugle an army of men\
with families in wagons, men and women on horseback and on foot, burst\
into the territory. During the first night a city of tents was raised at\
Guthrie and Oklahoma City. In ten days wooden houses rose on the plains.\
In a single year there were schools, churches, business blocks, and\
newspapers. Within fifteen years there was a population of more than\
half a million. To the west, Arizona with a population of about 125,000\
and New Mexico with 200,000 inhabitants joined Oklahoma in asking for\
statehood. Congress, then Republican, looked with reluctance upon the\
addition of more Democratic states; but in 1907 it was literally\
compelled by public sentiment and a sense of justice to admit Oklahoma.\
In 1910 the House of Representatives went to the Democrats and within\
two years Arizona and New Mexico were "under the roof." So the\
continental domain was rounded out.\
\
\
THE INFLUENCE OF THE FAR WEST ON NATIONAL LIFE\
\
=The Last of the Frontier.=--When Horace Greeley made his trip west in\
1859 he thus recorded the progress of civilization in his journal:\
\
     "May 12th, Chicago.--Chocolate and morning journals last\
     seen on the hotel breakfast table.\
\
     23rd, Leavenworth (Kansas).--Room bells and bath tubs make\
     their final appearance.\
\
     26th, Manhattan.--Potatoes and eggs last recognized among\
     the blessings that 'brighten as they take their flight.'\
\
     27th, Junction City.--Last visitation of a boot-black, with\
     dissolving views of a board bedroom. Beds bid us good-by."\
\
[Illustration: _Copyright by Panama-California Exposition_\
\
THE CANADIAN BUILDING AT THE PANAMA-CALIFORNIA INTERNATIONAL\
EXPOSITION, SAN DIEGO, 1915]\
\
Within thirty years travelers were riding across that country in Pullman\
cars and enjoying at the hotels all the comforts of a standardized\
civilization. The "wild west" was gone, and with it that frontier of\
pioneers and settlers who had long given such a bent and tone to\
American life and had "poured in upon the floor of Congress" such a long\
line of "backwoods politicians," as they were scornfully styled.\
\
=Free Land and Eastern Labor.=--It was not only the picturesque features\
of the frontier that were gone. Of far more consequence was the\
disappearance of free lands with all that meant for American labor. For\
more than a hundred years, any man of even moderate means had been able\
to secure a homestead of his own and an independent livelihood. For a\
hundred years America had been able to supply farms to as many\
immigrants as cared to till the soil. Every new pair of strong arms\
meant more farms and more wealth. Workmen in Eastern factories, mines,\
or mills who did not like their hours, wages, or conditions of labor,\
could readily find an outlet to the land. Now all that was over. By\
about 1890 most of the desirable land available under the Homestead act\
had disappeared. American industrial workers confronted a new situation.\
\
=Grain Supplants King Cotton.=--In the meantime a revolution was taking\
place in agriculture. Until 1860 the chief staples sold by America were\
cotton and tobacco. With the advance of the frontier, corn and wheat\
supplanted them both in agrarian economy. The West became the granary of\
the East and of Western Europe. The scoop shovel once used to handle\
grain was superseded by the towering elevator, loading and unloading\
thousands of bushels every hour. The refrigerator car and ship made the\
packing industry as stable as the production of cotton or corn, and gave\
an immense impetus to cattle raising and sheep farming. So the meat of\
the West took its place on the English dinner table by the side of bread\
baked from Dakotan wheat.\
\
=Aid in American Economic Independence.=--The effects of this economic\
movement were manifold and striking. Billions of dollars' worth of\
American grain, dairy produce, and meat were poured into European\
markets where they paid off debts due money lenders and acquired\
capital to develop American resources. Thus they accelerated the\
progress of American financiers toward national independence. The\
country, which had timidly turned to the Old World for capital in\
Hamilton's day and had borrowed at high rates of interest in London in\
Lincoln's day, moved swiftly toward the time when it would be among the\
world's first bankers and money lenders itself. Every grain of wheat and\
corn pulled the balance down on the American side of the scale.\
\
=Eastern Agriculture Affected.=--In the East as well as abroad the\
opening of the western granary produced momentous results. The\
agricultural economy of that part of the country was changed in many\
respects. Whole sections of the poorest land went almost out of\
cultivation, the abandoned farms of the New England hills bearing solemn\
witness to the competing power of western wheat fields. Sheep and cattle\
raising, as well as wheat and corn production, suffered at least a\
relative decline. Thousands of farmers cultivating land of the lower\
grade were forced to go West or were driven to the margin of\
subsistence. Even the herds that supplied Eastern cities with milk were\
fed upon grain brought halfway across the continent.\
\
=The Expansion of the American Market.=--Upon industry as well as\
agriculture, the opening of vast food-producing regions told in a\
thousand ways. The demand for farm machinery, clothing, boots, shoes,\
and other manufactures gave to American industries such a market as even\
Hamilton had never foreseen. Moreover it helped to expand far into the\
Mississippi Valley the industrial area once confined to the Northern\
seaboard states and to transform the region of the Great Lakes into an\
industrial empire. Herein lies the explanation of the growth of\
mid-western cities after 1865. Chicago, with its thirty-five railways,\
tapped every locality of the West and South. To the railways were added\
the water routes of the Lakes, thus creating a strategic center for\
industries. Long foresight carried the McCormick reaper works to\
Chicago before 1860. From Troy, New York, went a large stove plant. That\
was followed by a shoe factory from Massachusetts. The packing industry\
rose as a matter of course at a point so advantageous for cattle raisers\
and shippers and so well connected with Eastern markets.\
\
To the opening of the Far West also the Lake region was indebted for a\
large part of that water-borne traffic which made it "the Mediterranean\
basin of North America." The produce of the West and the manufactures of\
the East poured through it in an endless stream. The swift growth of\
shipbuilding on the Great Lakes helped to compensate for the decline of\
the American marine on the high seas. In response to this stimulus\
Detroit could boast that her shipwrights were able to turn out a ten\
thousand ton Leviathan for ore or grain about "as quickly as carpenters\
could put up an eight-room house." Thus in relation to the Far West the\
old Northwest territory--the wilderness of Jefferson's time--had taken\
the position formerly occupied by New England alone. It was supplying\
capital and manufactures for a vast agricultural empire West and South.\
\
=America on the Pacific.=--It has been said that the Mediterranean Sea\
was the center of ancient civilization; that modern civilization has\
developed on the shores of the Atlantic; and that the future belongs to\
the Pacific. At any rate, the sweep of the United States to the shores\
of the Pacific quickly exercised a powerful influence on world affairs\
and it undoubtedly has a still greater significance for the future.\
\
Very early regular traffic sprang up between the Pacific ports and the\
Hawaiian Islands, China, and Japan. Two years before the adjustment of\
the Oregon controversy with England, namely in 1844, the United States\
had established official and trading relations with China. Ten years\
later, four years after the admission of California to the union, the\
barred door of Japan was forced open by Commodore Perry. The commerce\
which had long before developed between the Pacific ports and Hawaii,\
China, and Japan now flourished under official care. In 1865 a ship\
from Honolulu carried sugar, molasses, and fruits from Hawaii to the\
Oregon port of Astoria. The next year a vessel from Hongkong brought\
rice, mats, and tea from China. An era of lucrative trade was opened.\
The annexation of Hawaii in 1898, the addition of the Philippines at the\
same time, and the participation of American troops in the suppression\
of the Boxer rebellion in Peking in 1900, were but signs and symbols of\
American power on the Pacific.\
\
[Illustration: _From an old print_\
\
COMMODORE PERRY'S MEN MAKING PRESENTS TO THE JAPANESE]\
\
=Conservation and the Land Problem.=--The disappearance of the frontier\
also brought new and serious problems to the governments of the states\
and the nation. The people of the whole United States suddenly were\
forced to realize that there was a limit to the rich, new land to\
exploit and to the forests and minerals awaiting the ax and the pick.\
Then arose in America the questions which had long perplexed the\
countries of the Old World--the scientific use of the soils and\
conservation of natural resources. Hitherto the government had followed\
the easy path of giving away arable land and selling forest and mineral\
lands at low prices. Now it had to face far more difficult and complex\
problems. It also had to consider questions of land tenure again,\
especially if the ideal of a nation of home-owning farmers was to be\
maintained. While there was plenty of land for every man or woman who\
wanted a home on the soil, it made little difference if single landlords\
or companies got possession of millions of acres, if a hundred men in\
one western river valley owned 17,000,000 acres; but when the good land\
for small homesteads was all gone, then was raised the real issue. At\
the opening of the twentieth century the nation, which a hundred years\
before had land and natural resources apparently without limit, was\
compelled to enact law after law conserving its forests and minerals.\
Then it was that the great state of California, on the very border of\
the continent, felt constrained to enact a land settlement measure\
providing government assistance in an effort to break up large holdings\
into small lots and to make it easy for actual settlers to acquire small\
farms. America was passing into a new epoch.\
\
\
=References=\
\
Henry Inman, _The Old Santa Fe Trail_.\
\
R.I. Dodge, _The Plains of the Great West_ (1877).\
\
C.H. Shinn, _The Story of the Mine_.\
\
Cy Warman, _The Story of the Railroad_.\
\
Emerson Hough, _The Story of the Cowboy_.\
\
H.H. Bancroft is the author of many works on the West but his writings\
will be found only in the larger libraries.\
\
Joseph Schafer, _History of the Pacific Northwest_ (ed. 1918).\
\
T.H. Hittel, _History of California_ (4 vols.).\
\
W.H. Olin, _American Irrigation Farming_.\
\
W.E. Smythe, _The Conquest of Arid America_.\
\
H.A. Millis, _The American-Japanese Problem_.\
\
E.S. Meany, _History of the State of Washington_.\
\
H.K. Norton, _The Story of California_.\
\
\
=Questions=\
\
1. Name the states west of the Mississippi in 1865.\
\
2. In what manner was the rest of the western region governed?\
\
3. How far had settlement been carried?\
\
4. What were the striking physical features of the West?\
\
5. How was settlement promoted after 1865?\
\
6. Why was admission to the union so eagerly sought?\
\
7. Explain how politics became involved in the creation of new states.\
\
8. Did the West rapidly become like the older sections of the country?\
\
9. What economic peculiarities did it retain or develop?\
\
10. How did the federal government aid in western agriculture?\
\
11. How did the development of the West affect the East? The South?\
\
12. What relation did the opening of the great grain areas of the West\
bear to the growth of America's commercial and financial power?\
\
13. State some of the new problems of the West.\
\
14. Discuss the significance of American expansion to the Pacific Ocean.\
\
\
=Research Topics=\
\
=The Passing of the Wild West.=--Haworth, _The United States in Our Own\
Times_, pp. 100-124.\
\
=The Indian Question.=--Sparks, _National Development_ (American Nation\
Series), pp. 265-281.\
\
=The Chinese Question.=--Sparks, _National Development_, pp. 229-250;\
Rhodes, _History of the United States_, Vol. VIII, pp. 180-196.\
\
=The Railway Age.=--Schafer, _History of the Pacific Northwest_, pp.\
230-245; E.V. Smalley, _The Northern Pacific Railroad_; Paxson, _The New\
Nation_ (Riverside Series), pp. 20-26, especially the map on p. 23, and\
pp. 142-148.\
\
=Agriculture and Business.=--Schafer, _Pacific Northwest_, pp. 246-289.\
\
=Ranching in the Northwest.=--Theodore Roosevelt, _Ranch Life_, and\
_Autobiography_, pp. 103-143.\
\
=The Conquest of the Desert.=--W.E. Smythe, _The Conquest of Arid\
America_.\
\
=Studies of Individual Western States.=--Consult any good encyclopedia.\
\
\
\
\
CHAPTER XIX\
\
DOMESTIC ISSUES BEFORE THE COUNTRY (1865-1897)\
\
\
For thirty years after the Civil War the leading political parties,\
although they engaged in heated presidential campaigns, were not sharply\
and clearly opposed on many matters of vital significance. During none\
of that time was there a clash of opinion over specific issues such as\
rent the country in 1800 when Jefferson rode a popular wave to victory,\
or again in 1828 when Jackson's western hordes came sweeping into power.\
The Democrats, who before 1860 definitely opposed protective tariffs,\
federal banking, internal improvements, and heavy taxes, now spoke\
cautiously on all these points. The Republicans, conscious of the fact\
that they had been a minority of the voters in 1860 and warned by the\
early loss of the House of Representatives in 1874, also moved with\
considerable prudence among the perplexing problems of the day. Again\
and again the votes in Congress showed that no clear line separated all\
the Democrats from all the Republicans. There were Republicans who\
favored tariff reductions and "cheap money." There were Democrats who\
looked with partiality upon high protection or with indulgence upon the\
contraction of the currency. Only on matters relating to the coercion of\
the South was the division between the parties fairly definite; this\
could be readily accounted for on practical as well as sentimental\
grounds.\
\
After all, the vague criticisms and proposals that found their way into\
the political platforms did but reflect the confusion of mind prevailing\
in the country. The fact that, out of the eighteen years between 1875\
and 1893, the Democrats held the House of Representatives for fourteen\
years while the Republicans had every President but one showed that the\
voters, like the politicians, were in a state of indecision. Hayes had a\
Democratic House during his entire term and a Democratic Senate for two\
years of the four. Cleveland was confronted by a belligerent Republican\
majority in the Senate during his first administration; and at the same\
time was supported by a Democratic majority in the House. Harrison was\
sustained by continuous Republican successes in Senatorial elections;\
but in the House he had the barest majority from 1889 to 1891 and lost\
that altogether at the election held in the middle of his term. The\
opinion of the country was evidently unsettled and fluctuating. It was\
still distracted by memories of the dead past and uncertain as to the\
trend of the future.\
\
\
THE CURRENCY QUESTION\
\
Nevertheless these years of muddled politics and nebulous issues proved\
to be a period in which social forces were gathering for the great\
campaign of 1896. Except for three new features--the railways, the\
trusts, and the trade unions--the subjects of debate among the people\
were the same as those that had engaged their attention since the\
foundation of the republic: the currency, the national debt, banking,\
the tariff, and taxation.\
\
=Debtors and the Fall in Prices.=--For many reasons the currency\
question occupied the center of interest. As of old, the farmers and\
planters of the West and South were heavily in debt to the East for\
borrowed money secured by farm mortgages; and they counted upon the sale\
of cotton, corn, wheat, and hogs to meet interest and principal when\
due. During the war, the Western farmers had been able to dispose of\
their produce at high prices and thus discharge their debts with\
comparative ease; but after the war prices declined. Wheat that sold at\
two dollars a bushel in 1865 brought sixty-four cents twenty years\
later. The meaning of this for the farmers in debt--and nearly\
three-fourths of them were in that class--can be shown by a single\
illustration. A thousand-dollar mortgage on a Western farm could be paid\
off by five hundred bushels of wheat when prices were high; whereas it\
took about fifteen hundred bushels to pay the same debt when wheat was\
at the bottom of the scale. For the farmer, it must be remembered, wheat\
was the measure of his labor, the product of his toil under the summer\
sun; and in its price he found the test of his prosperity.\
\
=Creditors and Falling Prices.=--To the bondholders or creditors, on the\
other hand, falling prices were clear gain. If a fifty-dollar coupon on\
a bond bought seventy or eighty bushels of wheat instead of twenty or\
thirty, the advantage to the owner of the coupon was obvious. Moreover\
the advantage seemed to him entirely just. Creditors had suffered heavy\
losses when the Civil War carried prices skyward while the interest\
rates on their old bonds remained stationary. For example, if a man had\
a $1000 bond issued before 1860 and paying interest at five per cent, he\
received fifty dollars a year from it. Before the war each dollar would\
buy a bushel of wheat; in 1865 it would only buy half a bushel. When\
prices--that is, the cost of living--began to go down, creditors\
therefore generally regarded the change with satisfaction as a return to\
normal conditions.\
\
=The Cause of Falling Prices.=--The fall in prices was due, no doubt, to\
many factors. Among them must be reckoned the discontinuance of\
government buying for war purposes, labor-saving farm machinery,\
immigration, and the opening of new wheat-growing regions. The currency,\
too, was an element in the situation. Whatever the cause, the\
discontented farmers believed that the way to raise prices was to issue\
more money. They viewed it as a case of supply and demand. If there was\
a small volume of currency in circulation, prices would be low; if there\
was a large volume, prices would be high. Hence they looked with favor\
upon all plans to increase the amount of money in circulation. First\
they advocated more paper notes--greenbacks--and then they turned to\
silver as the remedy. The creditors, on the other hand, naturally\
approved the reduction of the volume of currency. They wished to see the\
greenbacks withdrawn from circulation and gold--a metal more limited in\
volume than silver--made the sole basis of the national monetary system.\
\
=The Battle over the Greenbacks.=--The contest between these factions\
began as early as 1866. In that year, Congress enacted a law authorizing\
the Treasury to withdraw the greenbacks from circulation. The paper\
money party set up a shrill cry of protest, and kept up the fight until,\
in 1878, it forced Congress to provide for the continuous re-issue of\
the legal tender notes as they came into the Treasury in payment of\
taxes and other dues. Then could the friends of easy money rejoice:\
\
    "Thou, Greenback, 'tis of thee\
     Fair money of the free,\
      Of thee we sing."\
\
=Resumption of Specie Payment.=--There was, however, another side to\
this victory. The opponents of the greenbacks, unable to stop the\
circulation of paper, induced Congress to pass a law in 1875 providing\
that on and after January 1, 1879, "the Secretary of the Treasury shall\
redeem in coin the United States legal tender notes then outstanding on\
their presentation at the office of the Assistant Treasurer of the\
United States in the City of New York in sums of not less than fifty\
dollars." "The way to resume," John Sherman had said, "is to resume."\
When the hour for redemption arrived, the Treasury was prepared with a\
large hoard of gold. "On the appointed day," wrote the assistant\
secretary, "anxiety reigned in the office of the Treasury. Hour after\
hour passed; no news from New York. Inquiry by wire showed that all was\
quiet. At the close of the day this message came: '$135,000 of notes\
presented for coin--$400,000 of gold for notes.' That was all.\
Resumption was accomplished with no disturbance. By five o'clock the\
news was all over the land, and the New York bankers were sipping their\
tea in absolute safety."\
\
=The Specie Problem--the Parity of Gold and Silver.=--Defeated in their\
efforts to stop "the present suicidal and destructive policy of\
contraction," the advocates of an abundant currency demanded an increase\
in the volume of silver in circulation. This precipitated one of the\
sharpest political battles in American history. The issue turned on\
legal as well as economic points. The Constitution gave Congress the\
power to coin money and it forbade the states to make anything but gold\
and silver legal tender in the payment of debts. It evidently\
contemplated the use of both metals in the currency system. Such, at\
least, was the view of many eminent statesmen, including no less a\
personage than James G. Blaine. The difficulty, however, lay in\
maintaining gold and silver coins on a level which would permit them to\
circulate with equal facility. Obviously, if the gold in a gold dollar\
exceeds the value of the silver in a silver dollar on the open market,\
men will hoard gold money and leave silver money in circulation. When,\
for example, Congress in 1792 fixed the ratio of the two metals at one\
to fifteen--one ounce of gold declared worth fifteen of silver--it was\
soon found that gold had been undervalued. When again in 1834 the ratio\
was put at one to sixteen, it was found that silver was undervalued.\
Consequently the latter metal was not brought in for coinage and silver\
almost dropped out of circulation. Many a silver dollar was melted down\
by silverware factories.\
\
=Silver Demonetized in 1873.=--So things stood in 1873. At that time,\
Congress, in enacting a mintage law, discontinued the coinage of the\
standard silver dollar, then practically out of circulation. This act\
was denounced later by the friends of silver as "the crime of '73," a\
conspiracy devised by the money power and secretly carried out. This\
contention the debates in Congress do not seem to sustain. In the course\
of the argument on the mint law it was distinctly said by one speaker at\
least: "This bill provides for the making of changes in the legal tender\
coin of the country and for substituting as legal tender, coin of only\
one metal instead of two as heretofore."\
\
=The Decline in the Value of Silver.=--Absorbed in the greenback\
controversy, the people apparently did not appreciate, at the time, the\
significance of the "demonetization" of silver; but within a few years\
several events united in making it the center of a political storm.\
Germany, having abandoned silver in 1871, steadily increased her demand\
for gold. Three years later, the countries of the Latin Union followed\
this example, thus helping to enhance the price of the yellow metal. All\
the while, new silver lodes, discovered in the Far West, were pouring\
into the market great streams of the white metal, bearing down the\
price. Then came the resumption of specie payment, which, in effect,\
placed the paper money on a gold basis. Within twenty years silver was\
worth in gold only about half the price of 1870.\
\
That there had been a real decline in silver was denied by the friends\
of that metal. They alleged that gold had gone up because it had been\
given a monopoly in the coinage markets of civilized governments. This\
monopoly, they continued, was the fruit of a conspiracy against the\
people conceived by the bankers of the world. Moreover, they went on,\
the placing of the greenbacks on a gold basis had itself worked a\
contraction of the currency; it lowered the prices of labor and produce\
to the advantage of the holders of long-term investments bearing a fixed\
rate of interest. When wheat sold at sixty-four cents a bushel, their\
search for relief became desperate, and they at last concentrated their\
efforts on opening the mints of the government for the free coinage of\
silver at the ratio of sixteen to one.\
\
=Republicans and Democrats Divided.=--On this question both Republicans\
and Democrats were divided, the line being drawn between the East on the\
one hand and the South and West on the other, rather than between the\
two leading parties. So trusted a leader as James G. Blaine avowed, in a\
speech delivered in the Senate in 1878, that, as the Constitution\
required Congress to make both gold and silver the money of the land,\
the only question left was that of fixing the ratio between them. He\
affirmed, moreover, the main contention of the silver faction that a\
reopening of the government mints of the world to silver would bring it\
up to its old relation with gold. He admitted also that their most\
ominous warnings were well founded, saying: "I believe the struggle now\
going on in this country and in other countries for a single gold\
standard would, if successful, produce widespread disaster throughout\
the commercial world. The destruction of silver as money and the\
establishment of gold as the sole unit of value must have a ruinous\
effect on all forms of property, except those investments which yield a\
fixed return."\
\
This was exactly the concession that the silver party wanted.\
"Three-fourths of the business enterprises of this country are conducted\
on borrowed capital," said Senator Jones, of Nevada. "Three-fourths of\
the homes and farms that stand in the names of the actual occupants have\
been bought on time and a very large proportion of them are mortgaged\
for the payment of some part of the purchase money. Under the operation\
of a shrinkage in the volume of money, this enormous mass of borrowers,\
at the maturity of their respective debts, though nominally paying no\
more than the amount borrowed, with interest, are in reality, in the\
amount of the principal alone, returning a percentage of value greater\
than they received--more in equity than they contracted to pay.... In\
all discussions of the subject the creditors attempt to brush aside the\
equities involved by sneering at the debtors."\
\
=The Silver Purchase Act (1878).=--Even before the actual resumption of\
specie payment, the advocates of free silver were a power to be reckoned\
with, particularly in the Democratic party. They had a majority in the\
House of Representatives in 1878 and they carried a silver bill through\
that chamber. Blocked by the Republican Senate they accepted a\
compromise in the Bland-Allison bill, which provided for huge monthly\
purchases of silver by the government for coinage into dollars. So\
strong was the sentiment that a two-thirds majority was mustered after\
President Hayes vetoed the measure.\
\
The effect of this act, as some had anticipated, was disappointing. It\
did not stay silver on its downward course. Thereupon the silver faction\
pressed through Congress in 1886 a bill providing for the issue of paper\
certificates based on the silver accumulated in the Treasury. Still\
silver continued to fall. Then the advocates of inflation declared that\
they would be content with nothing short of free coinage at the ratio of\
sixteen to one. If the issue had been squarely presented in 1890, there\
is good reason for believing that free silver would have received a\
majority in both houses of Congress; but it was not presented.\
\
=The Sherman Silver Purchase Act and the Bond Sales.=--Republican\
leaders, particularly from the East, stemmed the silver tide by a\
diversion of forces. They passed the Sherman Act of 1890 providing for\
large monthly purchases of silver and for the issue of notes redeemable\
in gold or silver at the discretion of the Secretary of the Treasury. In\
a clause of superb ambiguity they announced that it was "the established\
policy of the United States to maintain the two metals on a parity with\
each other upon the present legal ratio or such other ratio as may be\
provided by law." For a while silver was buoyed up. Then it turned once\
more on its downward course. In the meantime the Treasury was in a sad\
plight. To maintain the gold reserve, President Cleveland felt compelled\
to sell government bonds; and to his dismay he found that as soon as the\
gold was brought in at the front door of the Treasury, notes were\
presented for redemption and the gold was quickly carried out at the\
back door. Alarmed at the vicious circle thus created, he urged upon\
Congress the repeal of the Sherman Silver Purchase Act. For this he was\
roundly condemned by many of his own followers who branded his conduct\
as "treason to the party"; but the Republicans, especially from the\
East, came to his rescue and in 1893 swept the troublesome sections of\
the law from the statute book. The anger of the silver faction knew no\
bounds, and the leaders made ready for the approaching presidential\
campaign.\
\
\
THE PROTECTIVE TARIFF AND TAXATION\
\
=Fluctuation in Tariff Policy.=--As each of the old parties was divided\
on the currency question, it is not surprising that there was some\
confusion in their ranks over the tariff. Like the silver issue, the\
tariff tended to align the manufacturing East against the agricultural\
West and South rather than to cut directly between the two parties.\
Still the Republicans on the whole stood firmly by the rates imposed\
during the Civil War. If we except the reductions of 1872 which were\
soon offset by increases, we may say that those rates were substantially\
unchanged for nearly twenty years. When a revision was brought about,\
however, it was initiated by Republican leaders. Seeing a huge surplus\
of revenue in the Treasury in 1883, they anticipated popular clamor by\
revising the tariff on the theory that it ought to be reformed by its\
friends rather than by its enemies. On the other hand, it was the\
Republicans also who enacted the McKinley tariff bill of 1890, which\
carried protection to its highest point up to that time.\
\
The Democrats on their part were not all confirmed free traders or even\
advocates of tariff for revenue only. In Cleveland's first\
administration they did attack the protective system in the House, where\
they had a majority, and in this they were vigorously supported by the\
President. The assault, however, proved to be a futile gesture for it\
was blocked by the Republicans in the Senate. When, after the sweeping\
victory of 1892, the Democrats in the House again attempted to bring\
down the tariff by the Wilson bill of 1894, they were checkmated by\
their own party colleagues in the upper chamber. In the end they were\
driven into a compromise that looked more like a McKinley than a Calhoun\
tariff. The Republicans taunted them with being "babes in the woods."\
President Cleveland was so dissatisfied with the bill that he refused to\
sign it, allowing it to become a law, on the lapse of ten days, without\
his approval.\
\
=The Income Tax of 1894.=--The advocates of tariff reduction usually\
associated with their proposal a tax on incomes. The argument which\
they advanced in support of their program was simple. Most of the\
industries, they said, are in the East and the protective tariff which\
taxes consumers for the benefit of manufacturers is, in effect, a\
tribute laid upon the rest of the country. As an offset they offered a\
tax on large incomes; this owing to the heavy concentration of rich\
people in the East, would fall mainly upon the beneficiaries of\
protection. "We propose," said one of them, "to place a part of the\
burden upon the accumulated wealth of the country instead of placing it\
all upon the consumption of the people." In this spirit the sponsors of\
the Wilson tariff bill laid a tax upon all incomes of $4000 a year or\
more.\
\
In taking this step, the Democrats encountered opposition in their own\
party. Senator Hill, of New York, turned fiercely upon them, exclaiming:\
"The professors with their books, the socialists with their schemes, the\
anarchists with their bombs are all instructing the people in the ...\
principles of taxation." Even the Eastern Republicans were hardly as\
savage in their denunciation of the tax. But all this labor was wasted.\
The next year the Supreme Court of the United States declared the income\
tax to be a direct tax, and therefore null and void because it was laid\
on incomes wherever found and not apportioned among the states according\
to population. The fact that four of the nine judges dissented from this\
decision was also an index to the diversity of opinion that divided both\
parties.\
\
\
THE RAILWAYS AND TRUSTS\
\
=The Grangers and State Regulation.=--The same uncertainty about the\
railways and trusts pervaded the ranks of the Republicans and Democrats.\
As to the railways, the first firm and consistent demand for their\
regulation came from the West. There the farmers, in the early\
seventies, having got control in state legislatures, particularly in\
Iowa, Wisconsin, and Illinois, enacted drastic laws prescribing the\
maximum charges which companies could make for carrying freight and\
passengers. The application of these measures, however, was limited\
because the state could not fix the rates for transporting goods and\
passengers beyond its own borders. The power of regulating interstate\
commerce, under the Constitution, belonged to Congress.\
\
=The Interstate Commerce Act of 1887.=--Within a few years, the movement\
which had been so effective in western legislatures appeared at\
Washington in the form of demands for the federal regulation of\
interstate rates. In 1887, the pressure became so strong that Congress\
created the interstate commerce commission and forbade many abuses on\
the part of railways; such as discriminating in charges between one\
shipper and another and granting secret rebates to favored persons. This\
law was a significant beginning; but it left the main question of\
rate-fixing untouched, much to the discontent of farmers and shippers.\
\
=The Sherman Anti-Trust Law of 1890.=--As in the case of the railways,\
attacks upon the trusts were first made in state legislatures, where it\
became the fashion to provide severe penalties for those who formed\
monopolies and "conspired to enhance prices." Republicans and Democrats\
united in the promotion of measures of this kind. As in the case of the\
railways also, the movement to curb the trusts soon had spokesmen at\
Washington. Though Blaine had declared that "trusts were largely a\
private affair with which neither the President nor any private citizen\
had any particular right to interfere," it was a Republican Congress\
that enacted in 1890 the first measure--the Sherman Anti-Trust\
Law--directed against great combinations in business. This act declared\
illegal "every contract, combination in the form of trust or otherwise,\
or conspiracy in restraint of trade and commerce among the several\
states or with foreign nations."\
\
=The Futility of the Anti-Trust Law.=--Whether the Sherman law was\
directed against all combinations or merely those which placed an\
"unreasonable restraint" on trade and competition was not apparent.\
Senator Platt of Connecticut, a careful statesman of the old school,\
averred: "The questions of whether the bill would be operative, of how\
it would operate, or whether it was within the power of Congress to\
enact it, have been whistled down the wind in this Senate as idle talk\
and the whole effort has been to get some bill headed: 'A bill to punish\
trusts,' with which to go to the country." Whatever its purpose, its\
effect upon existing trusts and upon the formation of new combinations\
was negligible. It was practically unenforced by President Harrison and\
President Cleveland, in spite of the constant demand for harsh action\
against "monopolies." It was patent that neither the Republicans nor the\
Democrats were prepared for a war on the trusts to the bitter end.\
\
\
THE MINOR PARTIES AND UNREST\
\
=The Demands of Dissenting Parties.=--From the election of 1872, when\
Horace Greeley made his ill-fated excursion into politics, onward, there\
appeared in each presidential campaign one, and sometimes two or more\
parties, stressing issues that appealed mainly to wage-earners and\
farmers. Whether they chose to call themselves Labor Reformers,\
Greenbackers, or Anti-monopolists, their slogans and their platforms all\
pointed in one direction. Even the Prohibitionists, who in 1872 started\
on their career with a single issue, the abolition of the liquor\
traffic, found themselves making declarations of faith on other matters\
and hopelessly split over the money question in 1896.\
\
A composite view of the platforms put forth by the dissenting parties\
from the administration of Grant to the close of Cleveland's second term\
reveals certain notions common to them all. These included among many\
others: the earliest possible payment of the national debt; regulation\
of the rates of railways and telegraph companies; repeal of the specie\
resumption act of 1875; the issue of legal tender notes by the\
government convertible into interest-bearing obligations on demand;\
unlimited coinage of silver as well as gold; a graduated inheritance\
tax; legislation to take from "land, railroad, money, and other gigantic\
corporate monopolies ... the powers they have so corruptly and unjustly\
usurped"; popular or direct election of United States Senators; woman\
suffrage; and a graduated income tax, "placing the burden of government\
on those who can best afford to pay instead of laying it on the farmers\
and producers."\
\
=Criticism of the Old Parties.=--To this long program of measures the\
reformers added harsh and acrid criticism of the old parties and\
sometimes, it must be said, of established institutions of government.\
"We denounce," exclaimed the Labor party in 1888, "the Democratic and\
Republican parties as hopelessly and shamelessly corrupt and by reason\
of their affiliation with monopolies equally unworthy of the suffrages\
of those who do not live upon public plunder." "The United States\
Senate," insisted the Greenbackers, "is a body composed largely of\
aristocratic millionaires who according to their own party papers\
generally purchased their elections in order to protect the great\
monopolies which they represent." Indeed, if their platforms are to be\
accepted at face value, the Greenbackers believed that the entire\
government had passed out of the hands of the people.\
\
=The Grangers.=--This unsparing, not to say revolutionary, criticism of\
American political life, appealed, it seems, mainly to farmers in the\
Middle West. Always active in politics, they had, before the Civil War,\
cast their lot as a rule with one or the other of the leading parties.\
In 1867, however, there grew up among them an association known as the\
"Patrons of Husbandry," which was destined to play a large role in the\
partisan contests of the succeeding decades. This society, which\
organized local lodges or "granges" on principles of secrecy and\
fraternity, was originally designed to promote in a general way the\
interests of the farmers. Its political bearings were apparently not\
grasped at first by its promoters. Yet, appealing as it did to the most\
active and independent spirits among the farmers and gathering to itself\
the strength that always comes from organization, it soon found itself\
in the hands of leaders more or less involved in politics. Where a few\
votes are marshaled together in a democracy, there is power.\
\
=The Greenback Party.=--The first extensive activity of the Grangers was\
connected with the attack on the railways in the Middle West which\
forced several state legislatures to reduce freight and passenger rates\
by law. At the same time, some leaders in the movement, no doubt\
emboldened by this success, launched in 1876 a new political party,\
popularly known as the Greenbackers, favoring a continued re-issue of\
the legal tenders. The beginnings were disappointing; but two years\
later, in the congressional elections, the Greenbackers swept whole\
sections of the country. Their candidates polled more than a million\
votes and fourteen of them were returned to the House of\
Representatives. To all outward signs a new and formidable party had\
entered the lists.\
\
The sanguine hopes of the leaders proved to be illusory. The quiet\
operations of the resumption act the following year, a revival of\
industry from a severe panic which had set in during 1873, the Silver\
Purchase Act, and the re-issue of Greenbacks cut away some of the\
grounds of agitation. There was also a diversion of forces to the silver\
faction which had a substantial support in the silver mine owners of the\
West. At all events the Greenback vote fell to about 300,000 in the\
election of 1880. A still greater drop came four years later and the\
party gave up the ghost, its sponsors returning to their former\
allegiance or sulking in their tents.\
\
=The Rise of the Populist Party.=--Those leaders of the old parties who\
now looked for a happy future unvexed by new factions were doomed to\
disappointment. The funeral of the Greenback party was hardly over\
before there arose two other political specters in the agrarian\
sections: the National Farmers' Alliance and Industrial Union,\
particularly strong in the South and West; and the Farmers' Alliance,\
operating in the North. By 1890 the two orders claimed over three\
million members. As in the case of the Grangers many years before, the\
leaders among them found an easy way into politics. In 1892 they held a\
convention, nominated a candidate for President, and adopted the name of\
"People's Party," from which they were known as Populists. Their\
platform, in every line, breathed a spirit of radicalism. They declared\
that "the newspapers are largely subsidized or muzzled; public opinion\
silenced; business prostrate; our homes covered with mortgages; and the\
land concentrating in the hands of capitalists.... The fruits of the\
toil of millions are boldly stolen to build up colossal fortunes for a\
few." Having delivered this sweeping indictment, the Populists put\
forward their remedies: the free coinage of silver, a graduated income\
tax, postal savings banks, and government ownership of railways and\
telegraphs. At the same time they approved the initiative, referendum,\
and popular election of Senators, and condemned the use of federal\
troops in labor disputes. On this platform, the Populists polled over a\
million votes, captured twenty-two presidential electors, and sent a\
powerful delegation to Congress.\
\
=Industrial Distress Augments Unrest.=--The four years intervening\
between the campaign of 1892 and the next presidential election brought\
forth many events which aggravated the ill-feeling expressed in the\
portentous platform of Populism. Cleveland, a consistent enemy of free\
silver, gave his powerful support to the gold standard and insisted on\
the repeal of the Silver Purchase Act, thus alienating an increasing\
number of his own party. In 1893 a grave industrial crisis fell upon the\
land: banks and business houses went into bankruptcy with startling\
rapidity; factories were closed; idle men thronged the streets hunting\
for work; and the prices of wheat and corn dropped to a ruinous level.\
Labor disputes also filled the crowded record. A strike at the Pullman\
car works in Chicago spread to the railways. Disorders ensued. President\
Cleveland, against the protests of the governor of Illinois, John P.\
Altgeld, dispatched troops to the scene of action. The United States\
district court at Chicago issued an injunction forbidding the president\
of the Railway Union, Eugene V. Debs, or his assistants to interfere\
with the transmission of the mails or interstate commerce in any form.\
For refusing to obey the order, Debs was arrested and imprisoned. With\
federal troops in possession of the field, with their leader in jail,\
the strikers gave up the battle, defeated but not subdued. To cap the\
climax the Supreme Court of the United States, the following year (1895)\
declared null and void the income tax law just enacted by Congress, thus\
fanning the flames of Populist discontent all over the West and South.\
\
\
THE SOUND MONEY BATTLE OF 1896\
\
=Conservative Men Alarmed.=--Men of conservative thought and leaning in\
both parties were by this time thoroughly disturbed. They looked upon\
the rise of Populism and the growth of labor disputes as the signs of a\
revolutionary spirit, indeed nothing short of a menace to American\
institutions and ideals. The income tax law of 1894, exclaimed the\
distinguished New York advocate, Joseph H. Choate, in an impassioned\
speech before the Supreme Court, "is communistic in its purposes and\
tendencies and is defended here upon principles as communistic,\
socialistic--what shall I call them--populistic as ever have been\
addressed to any political assembly in the world." Mr. Justice Field in\
the name of the Court replied: "The present assault upon capital is but\
the beginning. It will be but the stepping stone to others larger and\
more sweeping till our political conditions will become a war of the\
poor against the rich." In declaring the income tax unconstitutional, he\
believed that he was but averting greater evils lurking under its guise.\
As for free silver, nearly all conservative men were united in calling\
it a measure of confiscation and repudiation; an effort of the debtors\
to pay their obligations with money worth fifty cents on the dollar; the\
climax of villainies openly defended; a challenge to law, order, and\
honor.\
\
=The Republicans Come Out for the Gold Standard.=--It was among the\
Republicans that this opinion was most widely shared and firmly held. It\
was they who picked up the gauge thrown down by the Populists, though a\
host of Democrats, like Cleveland and Hill of New York, also battled\
against the growing Populist defection in Democratic ranks. When the\
Republican national convention assembled in 1896, the die was soon\
cast; a declaration of opposition to free silver save by international\
agreement was carried by a vote of eight to one. The Republican party,\
to use the vigorous language of Mr. Lodge, arrayed itself against "not\
only that organized failure, the Democratic party, but all the wandering\
forces of political chaos and social disorder ... in these bitter times\
when the forces of disorder are loose and the wreckers with their false\
lights gather at the shore to lure the ship of state upon the rocks."\
Yet it is due to historic truth to state that McKinley, whom the\
Republicans nominated, had voted in Congress for the free coinage of\
silver, was widely known as a bimetallist, and was only with difficulty\
persuaded to accept the unequivocal indorsement of the gold standard\
which was pressed upon him by his counselors. Having accepted it,\
however, he proved to be a valiant champion, though his major interest\
was undoubtedly in the protective tariff. To him nothing was more\
reprehensible than attempts "to array class against class, 'the classes\
against the masses,' section against section, labor against capital,\
'the poor against the rich,' or interest against interest." Such was the\
language of his acceptance speech. The whole program of Populism he now\
viewed as a "sudden, dangerous, and revolutionary assault upon law and\
order."\
\
=The Democratic Convention at Chicago.=--Never, save at the great\
disruption on the eve of the Civil War, did a Democratic national\
convention display more feeling than at Chicago in 1896. From the\
opening prayer to the last motion before the house, every act, every\
speech, every scene, every resolution evoked passions and sowed\
dissensions. Departing from long party custom, it voted down in anger a\
proposal to praise the administration of the Democratic President,\
Cleveland. When the platform with its radical planks, including free\
silver, was reported, a veritable storm broke. Senator Hill, trembling\
with emotion, protested against the departure from old tests of\
Democratic allegiance; against principles that must drive out of the\
party men who had grown gray in its service; against revolutionary,\
unwise, and unprecedented steps in the history of the party. Senator\
Vilas of Wisconsin, in great fervor, avowed that there was no difference\
in principle between the free coinage of silver--"the confiscation of\
one-half of the credits of the nation for the benefit of debtors"--and\
communism itself--"a universal distribution of property." In the triumph\
of that cause he saw the beginning of "the overthrow of all law, all\
justice, all security and repose in the social order."\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
WILLIAM J. BRYAN IN 1898]\
\
=The Crown of Thorns Speech.=--The champions of free silver replied in\
strident tones. They accused the gold advocates of being the aggressors\
who had assailed the labor and the homes of the people. William Jennings\
Bryan, of Nebraska, voiced their sentiments in a memorable oration. He\
declared that their cause "was as holy as the cause of liberty--the\
cause of humanity." He exclaimed that the contest was between the idle\
holders of idle capital and the toiling millions. Then he named those\
for whom he spoke--the wage-earner, the country lawyer, the small\
merchant, the farmer, and the miner. "The man who is employed for wages\
is as much a business man as his employer. The attorney in a country\
town is as much a business man as the corporation counsel in a great\
metropolis. The merchant at the cross roads store is as much a business\
man as the merchant of New York. The farmer ... is as much a business\
man as the man who goes upon the board of trade and bets upon the price\
of grain. The miners who go a thousand feet into the earth or climb two\
thousand feet upon the cliffs ... are as much business men as the few\
financial magnates who in a back room corner the money of the world....\
It is for these that we speak. We do not come as aggressors. Ours is not\
a war of conquest. We are fighting in defense of our homes, our\
families, and our posterity. We have petitioned and our petitions have\
been scorned. We have entreated and our entreaties have been\
disregarded. We have begged and they have mocked when our calamity came.\
We beg no longer; we entreat no more; we petition no more. We defy\
them.... We shall answer their demands for a gold standard by saying to\
them, 'You shall not press upon the brow of labor this crown of thorns.\
You shall not crucify mankind upon a cross of gold.'"\
\
=Bryan Nominated.=--In all the history of national conventions never had\
an orator so completely swayed a multitude; not even Yancey in his\
memorable plea in the Charleston convention of 1860 when, with grave and\
moving eloquence, he espoused the Southern cause against the impending\
fates. The delegates, after cheering Mr. Bryan until they could cheer no\
more, tore the standards from the floor and gathered around the Nebraska\
delegation to renew the deafening applause. The platform as reported was\
carried by a vote of two to one and the young orator from the West,\
hailed as America's Tiberius Gracchus, was nominated as the Democratic\
candidate for President. The South and West had triumphed over the East.\
The division was sectional, admittedly sectional--the old combination of\
power which Calhoun had so anxiously labored to build up a century\
earlier. The Gold Democrats were repudiated in terms which were clear to\
all. A few, unable to endure the thought of voting the Republican\
ticket, held a convention at Indianapolis where, with the sanction of\
Cleveland, they nominated candidates of their own and endorsed the gold\
standard in a forlorn hope.\
\
=The Democratic Platform.=--It was to the call from Chicago that the\
Democrats gave heed and the Republicans made answer. The platform on\
which Mr. Bryan stood, unlike most party manifestoes, was explicit in\
its language and its appeal. It denounced the practice of allowing\
national banks to issue notes intended to circulate as money on the\
ground that it was "in derogation of the Constitution," recalling\
Jackson's famous attack on the Bank in 1832. It declared that tariff\
duties should be laid "for the purpose of revenue"--Calhoun's doctrine.\
In demanding the free coinage of silver, it recurred to the practice\
abandoned in 1873. The income tax came next on the program. The platform\
alleged that the law of 1894, passed by a Democratic Congress, was "in\
strict pursuance of the uniform decisions of the Supreme Court for\
nearly a hundred years," and then hinted that the decision annulling the\
law might be reversed by the same body "as it may hereafter be\
constituted."\
\
The appeal to labor voiced by Mr. Bryan in his "crown of thorns" speech\
was reinforced in the platform. "As labor creates the wealth of the\
country," ran one plank, "we demand the passage of such laws as may be\
necessary to protect it in all its rights." Referring to the recent\
Pullman strike, the passions of which had not yet died away, the\
platform denounced "arbitrary interference by federal authorities in\
local affairs as a violation of the Constitution of the United States\
and a crime against free institutions." A special objection was lodged\
against "government by injunction as a new and highly dangerous form of\
oppression by which federal judges, in contempt of the laws of states\
and rights of citizens, become at once legislators, judges, and\
executioners." The remedy advanced was a federal law assuring trial by\
jury in all cases of contempt in labor disputes. Having made this\
declaration of faith, the Democrats, with Mr. Bryan at the head, raised\
their standard of battle.\
\
=The Heated Campaign.=--The campaign which ensued outrivaled in the\
range of its educational activities and the bitterness of its tone all\
other political conflicts in American history, not excepting the fateful\
struggle of 1860. Immense sums of money were contributed to the funds of\
both parties. Railway, banking, and other corporations gave generously\
to the Republicans; the silver miners, less lavishly but with the same\
anxiety, supported the Democrats. The country was flooded with\
pamphlets, posters, and handbills. Every public forum, from the great\
auditoriums of the cities to the "red schoolhouses" on the countryside,\
was occupied by the opposing forces.\
\
Mr. Bryan took the stump himself, visiting all parts of the country in\
special trains and addressing literally millions of people in the open\
air. Mr. McKinley chose the older and more formal plan. He received\
delegations at his home in Canton and discussed the issues of the\
campaign from his front porch, leaving to an army of well-organized\
orators the task of reaching the people in their home towns. Parades,\
processions, and monster demonstrations filled the land with politics.\
Whole states were polled in advance by the Republicans and the doubtful\
voters personally visited by men equipped with arguments and literature.\
Manufacturers, frightened at the possibility of disordered public\
credit, announced that they would close their doors if the Democrats won\
the election. Men were dismissed from public and private places on\
account of their political views, one eminent college president being\
forced out for advocating free silver. The language employed by\
impassioned and embittered speakers on both sides roused the public to a\
state of frenzy, once more showing the lengths to which men could go in\
personal and political abuse.\
\
=The Republican Victory.=--The verdict of the nation was decisive.\
McKinley received 271 of the 447 electoral votes, and 7,111,000 popular\
votes as against Bryan's 6,509,000. The congressional elections were\
equally positive although, on account of the composition of the Senate,\
the "hold-over" Democrats and Populists still enjoyed a power out of\
proportion to their strength as measured at the polls. Even as it was,\
the Republicans got full control of both houses--a dominion of the\
entire government which they were to hold for fourteen years--until the\
second half of Mr. Taft's administration, when they lost possession of\
the House of Representatives. The yoke of indecision was broken. The\
party of sound finance and protective tariffs set out upon its lease of\
power with untroubled assurance.\
\
\
REPUBLICAN MEASURES AND RESULTS\
\
=The Gold Standard and the Tariff.=--Yet strange as it may seem, the\
Republicans did not at once enact legislation making the gold dollar the\
standard for the national currency. Not until 1900 did they take that\
positive step. In his first inaugural President McKinley, as if still\
uncertain in his own mind or fearing a revival of the contest just\
closed, placed the tariff, not the money question, in the forefront.\
"The people have decided," he said, "that such legislation should be had\
as will give ample protection and encouragement to the industries and\
development of our country." Protection for American industries,\
therefore, he urged, is the task before Congress. "With adequate revenue\
secured, but not until then, we can enter upon changes in our fiscal\
laws." As the Republicans had only forty-six of the ninety Senators, and\
at least four of them were known advocates of free silver, the\
discretion exercised by the President in selecting the tariff for\
congressional debate was the better part of valor.\
\
Congress gave heed to the warning. Under the direction of Nelson P.\
Dingley, whose name was given to the bill, a tariff measure levying the\
highest rates yet laid in the history of American imposts was prepared\
and driven through the House of Representatives. The opposition\
encountered in the Senate, especially from the West, was overcome by\
concessions in favor of that section; but the duties on sugar, tin,\
steel, lumber, hemp, and in fact all of the essential commodities\
handled by combinations and trusts, were materially raised.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
PRESIDENT MCKINLEY AND HIS CABINET]\
\
=Growth of Combinations.=--The years that followed the enactment of the\
Dingley law were, whatever the cause, the most prosperous the country\
had witnessed for many a decade. Industries of every kind were soon\
running full blast; labor was employed; commerce spread more swiftly\
than ever to the markets of the world. Coincident with this progress was\
the organization of the greatest combinations and trusts the world had\
yet seen. In 1899 the smelters formed a trust with a capital of\
$65,000,000; in the same year the Standard Oil Company with a capital of\
over one hundred millions took the place of the old trust; and the\
Copper Trust was incorporated under the laws of New Jersey, its par\
value capital being fixed shortly afterward at $175,000,000. A year\
later the National Sugar Refining Company, of New Jersey, started with a\
capital of $90,000,000, adopting the policy of issuing to the\
stockholders no public statement of its earnings or financial condition.\
Before another twelvemonth had elapsed all previous corporate financing\
was reduced to small proportions by the flotation of the United States\
Steel Corporation with a capital of more than a billion dollars, an\
enterprise set in motion by the famous Morgan banking house of New York.\
\
In nearly all these gigantic undertakings, the same great leaders in\
finance were more or less intimately associated. To use the language of\
an eminent authority: "They are all allied and intertwined by their\
various mutual interests. For instance, the Pennsylvania Railroad\
interests are on the one hand allied with the Vanderbilts and on the\
other with the Rockefellers. The Vanderbilts are closely allied with the\
Morgan group.... Viewed as a whole we find the dominating influences in\
the trusts to be made up of a network of large and small capitalists,\
many allied to one another by ties of more or less importance, but all\
being appendages to or parts of the greater groups which are themselves\
dependent on and allied with the two mammoth or Rockefeller and Morgan\
groups. These two mammoth groups jointly ... constitute the heart of the\
business and commercial life of the nation." Such was the picture of\
triumphant business enterprise drawn by a financier within a few years\
after the memorable campaign of 1896.\
\
America had become one of the first workshops of the world. It was, by\
virtue of the closely knit organization of its business and finance, one\
of the most powerful and energetic leaders in the struggle of the giants\
for the business of the earth. The capital of the Steel Corporation\
alone was more than ten times the total national debt which the apostles\
of calamity in the days of Washington and Hamilton declared the nation\
could never pay. American industry, filling domestic markets to\
overflowing, was ready for new worlds to conquer.\
\
\
=References=\
\
F.W. Taussig, _Tariff History of the United States_.\
\
J.L. Laughlin, _Bimetallism in the United States_.\
\
A.B. Hepburn, _History of Coinage and Currency in the United States_.\
\
E.R.A. Seligman, _The Income Tax_.\
\
S.J. Buck, _The Granger Movement_ (Harvard Studies).\
\
F.H. Dixon, _State Railroad Control_.\
\
H.R. Meyer, _Government Regulation of Railway Rates_.\
\
W.Z. Ripley (editor), _Trusts, Pools, and Corporations_.\
\
R.T. Ely, _Monopolies and Trusts_.\
\
J.B. Clark, _The Control of Trusts_.\
\
\
=Questions=\
\
1. What proof have we that the political parties were not clearly\
divided over issues between 1865 and 1896?\
\
2. Why is a fall in prices a loss to farmers and a gain to holders of\
fixed investments?\
\
3. Explain the theory that the quantity of money determines the prices\
of commodities.\
\
4. Why was it difficult, if not impossible, to keep gold and silver at a\
parity?\
\
5. What special conditions favored a fall in silver between 1870 and\
1896?\
\
6. Describe some of the measures taken to raise the value of silver.\
\
7. Explain the relation between the tariff and the income tax in 1894.\
\
8. How did it happen that the farmers led in regulating railway rates?\
\
9. Give the terms of the Sherman Anti-Trust Act. What was its immediate\
effect?\
\
10. Name some of the minor parties. Enumerate the reforms they\
advocated.\
\
11. Describe briefly the experiments of the farmers in politics.\
\
12. How did industrial conditions increase unrest?\
\
13. Why were conservative men disturbed in the early nineties?\
\
14. Explain the Republican position in 1896.\
\
15. Give Mr. Bryan's doctrines in 1896. Enumerate the chief features of\
the Democratic platform.\
\
16. What were the leading measures adopted by the Republicans after\
their victory in 1896?\
\
\
=Research Topics=\
\
=Greenbacks and Resumption.=--Dewey, _Financial History of the United\
States_ (6th ed.), Sections 122-125, 154, and 378; MacDonald,\
_Documentary Source Book of American History_, pp. 446, 566; Hart,\
_American History Told by Contemporaries_, Vol. IV, pp. 531-533; Rhodes,\
_History of the United States_, Vol. VIII, pp. 97-101.\
\
=Demonetization and Coinage of Silver.=--Dewey, _Financial History_,\
Sections 170-173, 186, 189, 194; MacDonald, _Documentary Source Book_,\
pp. 174, 573, 593, 595; Hart, _Contemporaries_, Vol. IV, pp. 529-531;\
Rhodes, _History_, Vol. VIII, pp. 93-97.\
\
=Free Silver and the Campaign of 1896.=--Dewey, _National Problems_\
(American Nation Series), pp. 220-237, 314-328; Hart, _Contemporaries_,\
Vol. IV, pp. 533-538.\
\
=Tariff Revision.=--Dewey, _Financial History_, Sections 167, 180, 181,\
187, 192, 196; Hart, _Contemporaries_, Vol. IV, pp. 518-525; Rhodes,\
_History_, Vol. VIII, pp. 168-179, 346-351, 418-422.\
\
=Federal Regulation of Railways.=--Dewey, _National Problems_, pp.\
91-111; MacDonald, _Documentary Source Book_, pp. 581-590; Hart,\
_Contemporaries_, Vol. IV, pp. 521-523; Rhodes, _History_, Vol. VIII,\
pp. 288-292.\
\
=The Rise and Regulation of Trusts.=--Dewey, _National Problems_, pp.\
188-202; MacDonald, _Documentary Source Book_, pp. 591-593.\
\
=The Grangers and Populism.=--Paxson, _The New Nation_ (Riverside\
Series), pp. 20-37, 177-191, 208-223.\
\
=General Analysis of Domestic Problems.=--_Syllabus in History_ (New\
York State, 1920), pp. 137-142.\
\
\
\
\
CHAPTER XX\
\
AMERICA A WORLD POWER (1865-1900)\
\
\
It has now become a fashion, sanctioned by wide usage and by eminent\
historians, to speak of America, triumphant over Spain and possessed of\
new colonies, as entering the twentieth century in the role of "a world\
power," for the first time. Perhaps at this late day, it is useless to\
protest against the currency of the idea. Nevertheless, the truth is\
that from the fateful moment in March, 1775, when Edmund Burke unfolded\
to his colleagues in the British Parliament the resources of an\
invincible America, down to the settlement at Versailles in 1919 closing\
the drama of the World War, this nation has been a world power,\
influencing by its example, by its institutions, by its wealth, trade,\
and arms the course of international affairs. And it should be said also\
that neither in the field of commercial enterprise nor in that of\
diplomacy has it been wanting in spirit or ingenuity.\
\
When John Hay, Secretary of State, heard that an American citizen,\
Perdicaris, had been seized by Raisuli, a Moroccan bandit, in 1904, he\
wired his brusque message: "We want Perdicaris alive or Raisuli dead."\
This was but an echo of Commodore Decatur's equally characteristic\
answer, "Not a minute," given nearly a hundred years before to the\
pirates of Algiers begging for time to consider whether they would cease\
preying upon American merchantmen. Was it not as early as 1844 that the\
American commissioner, Caleb Cushing, taking advantage of the British\
Opium War on China, negotiated with the Celestial Empire a successful\
commercial treaty? Did he not then exultantly exclaim: "The laws of the\
Union follow its citizens and its banner protects them even within the\
domain of the Chinese Empire"? Was it not almost half a century before\
the battle of Manila Bay in 1898, that Commodore Perry with an adequate\
naval force "gently coerced Japan into friendship with us," leading all\
the nations of the earth in the opening of that empire to the trade of\
the Occident? Nor is it inappropriate in this connection to recall the\
fact that the Monroe Doctrine celebrates in 1923 its hundredth\
anniversary.\
\
\
AMERICAN FOREIGN RELATIONS (1865-98)\
\
=French Intrigues in Mexico Blocked.=--Between the war for the union and\
the war with Spain, the Department of State had many an occasion to\
present the rights of America among the powers of the world. Only a\
little while after the civil conflict came to a close, it was called\
upon to deal with a dangerous situation created in Mexico by the\
ambitions of Napoleon III. During the administration of Buchanan, Mexico\
had fallen into disorder through the strife of the Liberal and the\
Clerical parties; the President asked for authority to use American\
troops to bring to a peaceful haven "a wreck upon the ocean, drifting\
about as she is impelled by different factions." Our own domestic crisis\
then intervened.\
\
Observing the United States heavily involved in its own problems, the\
great powers, England, France, and Spain, decided in the autumn of 1861\
to take a hand themselves in restoring order in Mexico. They entered\
into an agreement to enforce the claims of their citizens against Mexico\
and to protect their subjects residing in that republic. They invited\
the United States to join them, and, on meeting a polite refusal, they\
prepared for a combined military and naval demonstration on their own\
account. In the midst of this action England and Spain, discovering the\
sinister purposes of Napoleon, withdrew their troops and left the field\
to him.\
\
The French Emperor, it was well known, looked with jealousy upon the\
growth of the United States and dreamed of establishing in the Western\
hemisphere an imperial power to offset the American republic.\
Intervention to collect debts was only a cloak for his deeper designs.\
Throwing off that guise in due time, he made the Archduke Maximilian, a\
brother of the ruler of Austria, emperor in Mexico, and surrounded his\
throne by French soldiers, in spite of all protests.\
\
This insolent attack upon the Mexican republic, deeply resented in the\
United States, was allowed to drift in its course until 1865. At that\
juncture General Sheridan was dispatched to the Mexican border with a\
large armed force; General Grant urged the use of the American army to\
expel the French from this continent. The Secretary of State, Seward,\
counseled negotiation first, and, applying the Monroe Doctrine, was able\
to prevail upon Napoleon III to withdraw his troops. Without the support\
of French arms, the sham empire in Mexico collapsed like a house of\
cards and the unhappy Maximilian, the victim of French ambition and\
intrigue, met his death at the hands of a Mexican firing squad.\
\
=Alaska Purchased.=--The Mexican affair had not been brought to a close\
before the Department of State was busy with negotiations which resulted\
in the purchase of Alaska from Russia. The treaty of cession, signed on\
March 30, 1867, added to the United States a domain of nearly six\
hundred thousand square miles, a territory larger than Texas and nearly\
three-fourths the size of the Louisiana purchase. Though it was a\
distant colony separated from our continental domain by a thousand miles\
of water, no question of "imperialism" or "colonization foreign to\
American doctrines" seems to have been raised at the time. The treaty\
was ratified promptly by the Senate. The purchase price, $7,200,000, was\
voted by the House of Representatives after the display of some\
resentment against a system that compelled it to appropriate money to\
fulfill an obligation which it had no part in making. Seward, who\
formulated the treaty, rejoiced, as he afterwards said, that he had kept\
Alaska out of the hands of England.\
\
=American Interest in the Caribbean.=--Having achieved this diplomatic\
triumph, Seward turned to the increase of American power in another\
direction. He negotiated, with Denmark, a treaty providing for the\
purchase of the islands of St. John and St. Thomas in the West Indies,\
strategic points in the Caribbean for sea power. This project, long\
afterward brought to fruition by other men, was defeated on this\
occasion by the refusal of the Senate to ratify the treaty. Evidently it\
was not yet prepared to exercise colonial dominion over other races.\
\
Undaunted by the misadventure in Caribbean policies, President Grant\
warmly advocated the acquisition of Santo Domingo. This little republic\
had long been in a state of general disorder. In 1869 a treaty of\
annexation was concluded with its president. The document Grant\
transmitted to the Senate with his cordial approval, only to have it\
rejected. Not at all changed in his opinion by the outcome of his\
effort, he continued to urge the subject of annexation. Even in his last\
message to Congress he referred to it, saying that time had only proved\
the wisdom of his early course. The addition of Santo Domingo to the\
American sphere of protection was the work of a later generation. The\
State Department, temporarily checked, had to bide its time.\
\
=The _Alabama_ Claims Arbitrated.=--Indeed, it had in hand a far more\
serious matter, a vexing issue that grew out of Civil War diplomacy. The\
British government, as already pointed out in other connections, had\
permitted Confederate cruisers, including the famous _Alabama_, built in\
British ports, to escape and prey upon the commerce of the Northern\
states. This action, denounced at the time by our government as a grave\
breach of neutrality as well as a grievous injury to American citizens,\
led first to remonstrances and finally to repeated claims for damages\
done to American ships and goods. For a long time Great Britain was\
firm. Her foreign secretary denied all obligations in the premises,\
adding somewhat curtly that "he wished to say once for all that Her\
Majesty's government disclaimed any responsibility for the losses and\
hoped that they had made their position perfectly clear." Still\
President Grant was not persuaded that the door of diplomacy, though\
closed, was barred. Hamilton Fish, his Secretary of State, renewed the\
demand. Finally he secured from the British government in 1871 the\
treaty of Washington providing for the arbitration not merely of the\
_Alabama_ and other claims but also all points of serious controversy\
between the two countries.\
\
The tribunal of arbitration thus authorized sat at Geneva in\
Switzerland, and after a long and careful review of the arguments on\
both sides awarded to the United States the lump sum of $15,500,000 to\
be distributed among the American claimants. The damages thus allowed\
were large, unquestionably larger than strict justice required and it is\
not surprising that the decision excited much adverse comment in\
England. Nevertheless, the prompt payment by the British government\
swept away at once a great cloud of ill-feeling in America. Moreover,\
the spectacle of two powerful nations choosing the way of peaceful\
arbitration to settle an angry dispute seemed a happy, if illusory, omen\
of a modern method for avoiding the arbitrament of war.\
\
=Samoa.=--If the Senate had its doubts at first about the wisdom of\
acquiring strategic points for naval power in distant seas, the same\
could not be said of the State Department or naval officers. In 1872\
Commander Meade, of the United States navy, alive to the importance of\
coaling stations even in mid-ocean, made a commercial agreement with the\
chief of Tutuila, one of the Samoan Islands, far below the equator, in\
the southern Pacific, nearer to Australia than to California. This\
agreement, providing among other things for our use of the harbor of\
Pago Pago as a naval base, was six years later changed into a formal\
treaty ratified by the Senate.\
\
Such enterprise could not escape the vigilant eyes of England and\
Germany, both mindful of the course of the sea power in history. The\
German emperor, seizing as a pretext a quarrel between his consul in the\
islands and a native king, laid claim to an interest in the Samoan\
group. England, aware of the dangers arising from German outposts in the\
southern seas so near to Australia, was not content to stand aside. So\
it happened that all three countries sent battleships to the Samoan\
waters, threatening a crisis that was fortunately averted by friendly\
settlement. If, as is alleged, Germany entertained a notion of\
challenging American sea power then and there, the presence of British\
ships must have dispelled that dream.\
\
The result of the affair was a tripartite agreement by which the three\
powers in 1889 undertook a protectorate over the islands. But joint\
control proved unsatisfactory. There was constant friction between the\
Germans and the English. The spheres of authority being vague and open\
to dispute, the plan had to be abandoned at the end of ten years.\
England withdrew altogether, leaving to Germany all the islands except\
Tutuila, which was ceded outright to the United States. Thus one of the\
finest harbors in the Pacific, to the intense delight of the American\
navy, passed permanently under American dominion. Another triumph in\
diplomacy was set down to the credit of the State Department.\
\
=Cleveland and the Venezuela Affair.=--In the relations with South\
America, as well as in those with the distant Pacific, the diplomacy of\
the government at Washington was put to the test. For some time it had\
been watching a dispute between England and Venezuela over the western\
boundary of British Guiana and, on an appeal from Venezuela, it had\
taken a lively interest in the contest. In 1895 President Cleveland saw\
that Great Britain would yield none of her claims. After hearing the\
arguments of Venezuela, his Secretary of State, Richard T. Olney, in a\
note none too conciliatory, asked the British government whether it was\
willing to arbitrate the points in controversy. This inquiry he\
accompanied by a warning to the effect that the United States could not\
permit any European power to contest its mastery in this hemisphere.\
"The United States," said the Secretary, "is practically sovereign on\
this continent and its fiat is law upon the subjects to which it\
confines its interposition.... Its infinite resources, combined with its\
isolated position, render it master of the situation and practically\
invulnerable against any or all other powers."\
\
The reply evoked from the British government by this strong statement\
was firm and clear. The Monroe Doctrine, it said, even if not so widely\
stretched by interpretation, was not binding in international law; the\
dispute with Venezuela was a matter of interest merely to the parties\
involved; and arbitration of the question was impossible. This response\
called forth President Cleveland's startling message of 1895. He asked\
Congress to create a commission authorized to ascertain by researches\
the true boundary between Venezuela and British Guiana. He added that it\
would be the duty of this country "to resist by every means in its\
power, as a willful aggression upon its rights and interests, the\
appropriation by Great Britain of any lands or the exercise of\
governmental jurisdiction over any territory which, after investigation,\
we have determined of right belongs to Venezuela." The serious character\
of this statement he thoroughly understood. He declared that he was\
conscious of his responsibilities, intimating that war, much as it was\
to be deplored, was not comparable to "a supine submission to wrong and\
injustice and the consequent loss of national self-respect and honor."\
\
[Illustration: GROVER CLEVELAND]\
\
The note of defiance which ran through this message, greeted by shrill\
cries of enthusiasm in many circles, was viewed in other quarters as a\
portent of war. Responsible newspapers in both countries spoke of an\
armed settlement of the dispute as inevitable. Congress created the\
commission and appropriated money for the investigation; a body of\
learned men was appointed to determine the merits of the conflicting\
boundary claims. The British government, deaf to the clamor of the\
bellicose section of the London press, deplored the incident,\
courteously replied in the affirmative to a request for assistance in\
the search for evidence, and finally agreed to the proposition that the\
issue be submitted to arbitration. The outcome of this somewhat perilous\
dispute contributed not a little to Cleveland's reputation as "a\
sterling representative of the true American spirit." This was not\
diminished when the tribunal of arbitration found that Great Britain was\
on the whole right in her territorial claims against Venezuela.\
\
=The Annexation of Hawaii.=--While engaged in the dangerous Venezuela\
controversy, President Cleveland was compelled by a strange turn in\
events to consider the annexation of the Hawaiian Islands in the\
mid-Pacific. For more than half a century American missionaries had been\
active in converting the natives to the Christian faith and enterprising\
American business men had been developing the fertile sugar plantations.\
Both the Department of State and the Navy Department were fully\
conscious of the strategic relation of the islands to the growth of sea\
power and watched with anxiety any developments likely to bring them\
under some other Dominion.\
\
The country at large was indifferent, however, until 1893, when a\
revolution, headed by Americans, broke out, ending in the overthrow of\
the native government, the abolition of the primitive monarchy, and the\
retirement of Queen Liliuokalani to private life. This crisis, a\
repetition of the Texas affair in a small theater, was immediately\
followed by a demand from the new Hawaiian government for annexation to\
the United States. President Harrison looked with favor on the proposal,\
negotiated the treaty of annexation, and laid it before the Senate for\
approval. There it still rested when his term of office was brought to a\
close.\
\
Harrison's successor, Cleveland, it was well known, had doubts about the\
propriety of American action in Hawaii. For the purpose of making an\
inquiry into the matter, he sent a special commissioner to the islands.\
On the basis of the report of his agent, Cleveland came to the\
conclusion that "the revolution in the island kingdom had been\
accomplished by the improper use of the armed forces of the United\
States and that the wrong should be righted by a restoration of the\
queen to her throne." Such being his matured conviction, though the\
facts upon which he rested it were warmly controverted, he could do\
nothing but withdraw the treaty from the Senate and close the incident.\
\
To the Republicans this sharp and cavalier disposal of their plans,\
carried out in a way that impugned the motives of a Republican\
President, was nothing less than "a betrayal of American interests." In\
their platform of 1896 they made clear their position: "Our foreign\
policy should be at all times firm, vigorous, and dignified and all our\
interests in the Western hemisphere carefully watched and guarded. The\
Hawaiian Islands should be controlled by the United States and no\
foreign power should be permitted to interfere with them." There was no\
mistaking this view of the issue. As the vote in the election gave\
popular sanction to Republican policies, Congress by a joint resolution,\
passed on July 6, 1898, annexed the islands to the United States and\
later conferred upon them the ordinary territorial form of government.\
\
\
CUBA AND THE SPANISH WAR\
\
=Early American Relations with Cuba.=--The year that brought Hawaii\
finally under the American flag likewise drew to a conclusion another\
long controversy over a similar outpost in the Atlantic, one of the last\
remnants of the once glorious Spanish empire--the island of Cuba.\
\
For a century the Department of State had kept an anxious eye upon this\
base of power, knowing full well that both France and England, already\
well established in the West Indies, had their attention also fixed upon\
Cuba. In the administration of President Fillmore they had united in\
proposing to the United States a tripartite treaty guaranteeing Spain in\
her none too certain ownership. This proposal, squarely rejected,\
furnished the occasion for a statement of American policy which stood\
the test of all the years that followed; namely, that the affair was one\
between Spain and the United States alone.\
\
In that long contest in the United States for the balance of power\
between the North and South, leaders in the latter section often thought\
of bringing Cuba into the union to offset the free states. An\
opportunity to announce their purposes publicly was afforded in 1854 by\
a controversy over the seizure of an American ship by Cuban authorities.\
On that occasion three American ministers abroad, stationed at Madrid,\
Paris, and London respectively, held a conference and issued the\
celebrated "Ostend Manifesto." They united in declaring that Cuba, by\
her geographical position, formed a part of the United States, that\
possession by a foreign power was inimical to American interests, and\
that an effort should be made to purchase the island from Spain. In case\
the owner refused to sell, they concluded, with a menacing flourish, "by\
every law, human and divine, we shall be justified in wresting it from\
Spain if we possess the power." This startling proclamation to the world\
was promptly disowned by the United States government.\
\
[Illustration: _=An old cartoon.=_\
\
A SIGHT TOO BAD\
\
_Struggling Cuba._ "You must be awfully near-sighted, Mr. President, not\
to recognize me." _U.S.G._ "No, I am far-sighted: for I can recognize\
France."]\
\
=Revolutions in Cuba.=--For nearly twenty years afterwards the Cuban\
question rested. Then it was revived in another form during President\
Grant's administrations, when the natives became engaged in a\
destructive revolt against Spanish officials. For ten years--1868-78--a\
guerrilla warfare raged in the island. American citizens, by virtue of\
their ancient traditions of democracy, naturally sympathized with a war\
for independence and self-government. Expeditions to help the insurgents\
were fitted out secretly in American ports. Arms and supplies were\
smuggled into Cuba. American soldiers of fortune joined their ranks. The\
enforcement of neutrality against the friends of Cuban independence, no\
pleasing task for a sympathetic President, the protection of American\
lives and property in the revolutionary area, and similar matters kept\
our government busy with Cuba for a whole decade.\
\
A brief lull in Cuban disorders was followed in 1895 by a renewal of the\
revolutionary movement. The contest between the rebels and the Spanish\
troops, marked by extreme cruelty and a total disregard for life and\
property, exceeded all bounds of decency, and once more raised the old\
questions that had tormented Grant's administration. Gomez, the leader\
of the revolt, intent upon provoking American interference, laid waste\
the land with fire and sword. By a proclamation of November 6, 1895, he\
ordered the destruction of sugar plantations and railway connections and\
the closure of all sugar factories. The work of ruin was completed by\
the ruthless Spanish general, Weyler, who concentrated the inhabitants\
from rural regions into military camps, where they died by the hundreds\
of disease and starvation. Stories of the atrocities, bad enough in\
simple form, became lurid when transmuted into American news and deeply\
moved the sympathies of the American people. Sermons were preached about\
Spanish misdeeds; orators demanded that the Cubans be sustained "in\
their heroic struggle for independence"; newspapers, scouting the\
ordinary forms of diplomatic negotiation, spurned mediation and demanded\
intervention and war if necessary.\
\
[Illustration: _Underwood and Underwood, N.Y._\
\
CUBAN REVOLUTIONISTS]\
\
=President Cleveland's Policy.=--Cleveland chose the way of peace. He\
ordered the observance of the rule of neutrality. He declined to act on\
a resolution of Congress in favor of giving to the Cubans the rights of\
belligerents. Anxious to bring order to the distracted island, he\
tendered to Spain the good offices of the United States as mediator in\
the contest--a tender rejected by the Spanish government with the broad\
hint that President Cleveland might be more vigorous in putting a stop\
to the unlawful aid in money, arms, and supplies, afforded to the\
insurgents by American sympathizers. Thereupon the President returned to\
the course he had marked out for himself, leaving "the public nuisance"\
to his successor, President McKinley.\
\
=Republican Policies.=--The Republicans in 1897 found themselves in a\
position to employ that "firm, vigorous, and dignified" foreign policy\
which they had approved in their platform. They had declared: "The\
government of Spain having lost control of Cuba and being unable to\
\
protect the property or lives of resident American citizens or to comply\
with its treaty obligations, we believe that the government of the\
United States should actively use its influence and good offices to\
restore peace and give independence to the island." The American\
property in Cuba to which the Republicans referred in their platform\
amounted by this time to more than fifty million dollars; the commerce\
with the island reached more than one hundred millions annually; and the\
claims of American citizens against Spain for property destroyed totaled\
sixteen millions. To the pleas of humanity which made such an effective\
appeal to the hearts of the American people, there were thus added\
practical considerations of great weight.\
\
=President McKinley Negotiates.=--In the face of the swelling tide of\
popular opinion in favor of quick, drastic, and positive action,\
McKinley chose first the way of diplomacy. A short time after his\
inauguration he lodged with the Spanish government a dignified protest\
against its policies in Cuba, thus opening a game of thrust and parry\
with the suave ministers at Madrid. The results of the exchange of\
notes were the recall of the obnoxious General Weyler, the appointment\
of a governor-general less bloodthirsty in his methods, a change in the\
policy of concentrating civilians in military camps, and finally a\
promise of "home rule" for Cuba. There is no doubt that the Spanish\
government was eager to avoid a war that could have but one outcome. The\
American minister at Madrid, General Woodford, was convinced that firm\
and patient pressure would have resulted in the final surrender of Cuba\
by the Spanish government.\
\
=The De Lome and the _Maine_ Incidents.=--Such a policy was defeated by\
events. In February, 1898, a private letter written by Senor de Lome,\
the Spanish ambassador at Washington, expressing contempt for the\
President of the United States, was filched from the mails and passed\
into the hands of a journalist, William R. Hearst, who published it to\
the world. In the excited state of American opinion, few gave heed to\
the grave breach of diplomatic courtesy committed by breaking open\
private correspondence. The Spanish government was compelled to recall\
De Lome, thus officially condemning his conduct.\
\
At this point a far more serious crisis put the pacific relations of the\
two negotiating countries in dire peril. On February 15, the battleship\
_Maine_, riding in the harbor of Havana, was blown up and sunk, carrying\
to death two officers and two hundred and fifty-eight members of the\
crew. This tragedy, ascribed by the American public to the malevolence\
of Spanish officials, profoundly stirred an already furious nation.\
When, on March 21, a commission of inquiry reported that the ill-fated\
ship had been blown up by a submarine mine which had in turn set off\
some of the ship's magazines, the worst suspicions seemed confirmed. If\
any one was inclined to be indifferent to the Cuban war for\
independence, he was now met by the vehement cry: "Remember the\
_Maine_!"\
\
=Spanish Concessions.=--Still the State Department, under McKinley's\
steady hand, pursued the path of negotiation, Spain proving more pliable\
and more ready with promises of reform in the island. Early in April,\
however, there came a decided change in the tenor of American diplomacy.\
On the 4th, McKinley, evidently convinced that promises did not mean\
performances, instructed our minister at Madrid to warn the Spanish\
government that as no effective armistice had been offered to the\
Cubans, he would lay the whole matter before Congress. This decision,\
every one knew, from the temper of Congress, meant war--a prospect which\
excited all the European powers. The Pope took an active interest in the\
crisis. France and Germany, foreseeing from long experience in world\
politics an increase of American power and prestige through war, sought\
to prevent it. Spain, hopeless and conscious of her weakness, at last\
dispatched to the President a note promising to suspend hostilities, to\
call a Cuban parliament, and to grant all the autonomy that could be\
reasonably asked.\
\
=President McKinley Calls for War.=--For reasons of his own--reasons\
which have never yet been fully explained--McKinley ignored the final\
program of concessions presented by Spain. At the very moment when his\
patient negotiations seemed to bear full fruit, he veered sharply from\
his course and launched the country into the war by sending to Congress\
his militant message of April 11, 1898. Without making public the last\
note he had received from Spain, he declared that he was brought to the\
end of his effort and the cause was in the hands of Congress. Humanity,\
the protection of American citizens and property, the injuries to\
American commerce and business, the inability of Spain to bring about\
permanent peace in the island--these were the grounds for action that\
induced him to ask for authority to employ military and naval forces in\
establishing a stable government in Cuba. They were sufficient for a\
public already straining at the leash.\
\
=The Resolution of Congress.=--There was no doubt of the outcome when\
the issue was withdrawn from diplomacy and placed in charge of Congress.\
Resolutions were soon introduced into the House of Representatives\
authorizing the President to employ armed force in securing peace and\
order in the island and "establishing by the free action of the people\
thereof a stable and independent government of their own." To the form\
and spirit of this proposal the Democrats and Populists took exception.\
In the Senate, where they were stronger, their position had to be\
reckoned with by the narrow Republican majority. As the resolution\
finally read, the independence of Cuba was recognized; Spain was called\
upon to relinquish her authority and withdraw from the island; and the\
President was empowered to use force to the extent necessary to carry\
the resolutions into effect. Furthermore the United States disclaimed\
"any disposition or intention to exercise sovereignty, jurisdiction, or\
control over said island except for the pacification thereof." Final\
action was taken by Congress on April 19, 1898, and approved by the\
President on the following day.\
\
=War and Victory.=--Startling events then followed in swift succession.\
The navy, as a result in no small measure of the alertness of Theodore\
Roosevelt, Assistant Secretary of the Department, was ready for the\
trial by battle. On May 1, Commodore Dewey at Manila Bay shattered the\
Spanish fleet, marking the doom of Spanish dominion in the Philippines.\
On July 3, the Spanish fleet under Admiral Cervera, in attempting to\
escape from Havana, was utterly destroyed by American forces under\
Commodore Schley. On July 17, Santiago, invested by American troops\
under General Shafter and shelled by the American ships, gave up the\
struggle. On July 25 General Miles landed in Porto Rico. On August 13,\
General Merritt and Admiral Dewey carried Manila by storm. The war was\
over.\
\
=The Peace Protocol.=--Spain had already taken cognizance of stern\
facts. As early as July 26, 1898, acting through the French ambassador,\
M. Cambon, the Madrid government approached President McKinley for a\
statement of the terms on which hostilities could be brought to a close.\
After some skirmishing Spain yielded reluctantly to the ultimatum. On\
August 12, the preliminary peace protocol was signed, stipulating that\
Cuba should be free, Porto Rico ceded to the United States, and Manila\
occupied by American troops pending the formal treaty of peace. On\
October 1, the commissioners of the two countries met at Paris to bring\
about the final settlement.\
\
=Peace Negotiations.=--When the day for the first session of the\
conference arrived, the government at Washington apparently had not made\
up its mind on the final disposition of the Philippines. Perhaps, before\
the battle of Manila Bay, not ten thousand people in the United States\
knew or cared where the Philippines were. Certainly there was in the\
autumn of 1898 no decided opinion as to what should be done with the\
fruits of Dewey's victory. President McKinley doubtless voiced the\
sentiment of the people when he stated to the peace commissioners on the\
eve of their departure that there had originally been no thought of\
conquest in the Pacific.\
\
The march of events, he added, had imposed new duties on the country.\
"Incidental to our tenure in the Philippines," he said, "is the\
commercial opportunity to which American statesmanship cannot be\
indifferent. It is just to use every legitimate means for the\
enlargement of American trade." On this ground he directed the\
commissioners to accept not less than the cession of the island of\
Luzon, the chief of the Philippine group, with its harbor of Manila. It\
was not until the latter part of October that he definitely instructed\
them to demand the entire archipelago, on the theory that the occupation\
of Luzon alone could not be justified "on political, commercial, or\
humanitarian grounds." This departure from the letter of the peace\
protocol was bitterly resented by the Spanish agents. It was with\
heaviness of heart that they surrendered the last sign of Spain's\
ancient dominion in the far Pacific.\
\
=The Final Terms of Peace.=--The treaty of peace, as finally agreed\
upon, embraced the following terms: the independence of Cuba; the\
cession of Porto Rico, Guam, and the Philippines to the United States;\
the settlement of claims filed by the citizens of both countries; the\
payment of twenty million dollars to Spain by the United States for the\
Philippines; and the determination of the status of the inhabitants of\
the ceded territories by Congress. The great decision had been made. Its\
issue was in the hands of the Senate where the Democrats and the\
Populists held the balance of power under the requirement of the\
two-thirds vote for ratification.\
\
=The Contest in America over the Treaty of Peace.=--The publication of\
the treaty committing the United States to the administration of distant\
colonies directed the shifting tides of public opinion into two distinct\
channels: support of the policy and opposition to it. The trend in\
Republican leadership, long in the direction marked out by the treaty,\
now came into the open. Perhaps a majority of the men highest in the\
councils of that party had undergone the change of heart reflected in\
the letters of John Hay, Secretary of State. In August of 1898 he had\
hinted, in a friendly letter to Andrew Carnegie, that he sympathized\
with the latter's opposition to "imperialism"; but he had added quickly:\
"The only question in my mind is how far it is now possible for us to\
withdraw from the Philippines." In November of the same year he wrote to\
Whitelaw Reid, one of the peace commissioners at Paris: "There is a wild\
and frantic attack now going on in the press against the whole\
Philippine transaction. Andrew Carnegie really seems to be off his\
head.... But all this confusion of tongues will go its way. The country\
will applaud the resolution that has been reached and you will return in\
the role of conquering heroes with your 'brows bound with oak.'"\
\
Senator Beveridge of Indiana and Senator Platt of Connecticut, accepting\
the verdict of history as the proof of manifest destiny, called for\
unquestioning support of the administration in its final step. "Every\
expansion of our territory," said the latter, "has been in accordance\
with the irresistible law of growth. We could no more resist the\
successive expansions by which we have grown to be the strongest nation\
on earth than a tree can resist its growth. The history of territorial\
expansion is the history of our nation's progress and glory. It is a\
matter to be proud of, not to lament. We should rejoice that Providence\
has given us the opportunity to extend our influence, our institutions,\
and our civilization into regions hitherto closed to us, rather than\
contrive how we can thwart its designs."\
\
This doctrine was savagely attacked by opponents of McKinley's policy,\
many a stanch Republican joining with the majority of Democrats in\
denouncing the treaty as a departure from the ideals of the republic.\
Senator Vest introduced in the Senate a resolution that "under the\
Constitution of the United States, no power is given to the federal\
Government to acquire territory to be held and governed permanently as\
colonies." Senator Hoar, of Massachusetts, whose long and honorable\
career gave weight to his lightest words, inveighed against the whole\
procedure and to the end of his days believed that the new drift into\
rivalry with European nations as a colonial power was fraught with\
genuine danger. "Our imperialistic friends," he said, "seem to have\
forgotten the use of the vocabulary of liberty. They talk about giving\
good government. 'We shall give them such a government as we think they\
are fitted for.' 'We shall give them a better government than they had\
before.' Why, Mr. President, that one phrase conveys to a free man and a\
free people the most stinging of insults. In that little phrase, as in a\
seed, is contained the germ of all despotism and of all tyranny.\
Government is not a gift. Free government is not to be given by all the\
blended powers of earth and heaven. It is a birthright. It belongs, as\
our fathers said, and as their children said, as Jefferson said, and as\
President McKinley said, to human nature itself."\
\
The Senate, more conservative on the question of annexation than the\
House of Representatives composed of men freshly elected in the stirring\
campaign of 1896, was deliberate about ratification of the treaty. The\
Democrats and Populists were especially recalcitrant. Mr. Bryan hurried\
to Washington and brought his personal influence to bear in favor of\
speedy action. Patriotism required ratification, it was said in one\
quarter. The country desires peace and the Senate ought not to delay, it\
was urged in another. Finally, on February 6, 1899, the requisite\
majority of two-thirds was mustered, many a Senator who voted for the\
treaty, however, sharing the misgivings of Senator Hoar as to the\
"dangers of imperialism." Indeed at the time, the Senators passed a\
resolution declaring that the policy to be adopted in the Philippines\
was still an open question, leaving to the future, in this way, the\
possibility of retracing their steps.\
\
=The Attitude of England.=--The Spanish war, while accomplishing the\
simple objects of those who launched the nation on that course, like all\
other wars, produced results wholly unforeseen. In the first place, it\
exercised a profound influence on the drift of opinion among European\
powers. In England, sympathy with the United States was from the first\
positive and outspoken. "The state of feeling here," wrote Mr. Hay, then\
ambassador in London, "is the best I have ever known. From every quarter\
the evidences of it come to me. The royal family by habit and tradition\
are most careful not to break the rules of strict neutrality, but even\
among them I find nothing but hearty kindness and--so far as is\
consistent with propriety--sympathy. Among the political leaders on both\
sides I find not only sympathy but a somewhat eager desire that 'the\
other fellows' shall not seem more friendly."\
\
Joseph Chamberlain, the distinguished Liberal statesman, thinking no\
doubt of the continental situation, said in a political address at the\
very opening of the war that the next duty of Englishmen "is to\
establish and maintain bonds of permanent unity with our kinsmen across\
the Atlantic.... I even go so far as to say that, terrible as war may\
be, even war would be cheaply purchased if, in a great and noble cause,\
the Stars and Stripes and the Union Jack should wave together over an\
Anglo-Saxon alliance." To the American ambassador he added\
significantly that he did not "care a hang what they say about it on the\
continent," which was another way of expressing the hope that the\
warning to Germany and France was sufficient. This friendly English\
opinion, so useful to the United States when a combination of powers to\
support Spain was more than possible, removed all fears as to the\
consequences of the war. Henry Adams, recalling days of humiliation in\
London during the Civil War, when his father was the American\
ambassador, coolly remarked that it was "the sudden appearance of\
Germany as the grizzly terror" that "frightened England into America's\
arms"; but the net result in keeping the field free for an easy triumph\
of American arms was none the less appreciated in Washington where,\
despite outward calm, fears of European complications were never absent.\
\
\
AMERICAN POLICIES IN THE PHILIPPINES AND THE ORIENT\
\
=The Filipino Revolt against American Rule.=--In the sphere of domestic\
politics, as well as in the field of foreign relations, the outcome of\
the Spanish war exercised a marked influence. It introduced at once\
problems of colonial administration and difficulties in adjusting trade\
relations with the outlying dominions. These were furthermore\
complicated in the very beginning by the outbreak of an insurrection\
against American sovereignty in the Philippines. The leader of the\
revolt, Aguinaldo, had been invited to join the American forces in\
overthrowing Spanish dominion, and he had assumed, apparently without\
warrant, that independence would be the result of the joint operations.\
When the news reached him that the American flag had been substituted\
for the Spanish flag, his resentment was keen. In February, 1899, there\
occurred a slight collision between his men and some American soldiers.\
The conflict thus begun was followed by serious fighting which finally\
dwindled into a vexatious guerrilla warfare lasting three years and\
costing heavily in men and money. Atrocities were committed by the\
native insurrectionists and, sad to relate, they were repaid in kind;\
it was argued in defense of the army that the ordinary rules of warfare\
were without terror to men accustomed to fighting like savages. In vain\
did McKinley assure the Filipinos that the institutions and laws\
established in the islands would be designed "not for our satisfaction\
or for the expression of our theoretical views, but for the happiness,\
peace, and prosperity of the people of the Philippine Islands." Nothing\
short of military pressure could bring the warring revolutionists to\
terms.\
\
=Attacks on Republican "Imperialism."=--The Filipino insurrection,\
following so quickly upon the ratification of the treaty with Spain,\
moved the American opponents of McKinley's colonial policies to redouble\
their denunciation of what they were pleased to call "imperialism."\
Senator Hoar was more than usually caustic in his indictment of the new\
course. The revolt against American rule did but convince him of the\
folly hidden in the first fateful measures. Everywhere he saw a\
conspiracy of silence and injustice. "I have failed to discover in the\
speeches, public or private, of the advocates of this war," he contended\
in the Senate, "or in the press which supports it and them, a single\
expression anywhere of a desire to do justice to the people of the\
Philippine Islands, or of a desire to make known to the people of the\
United States the truth of the case.... The catchwords, the cries, the\
pithy and pregnant phrases of which their speech is full, all mean\
dominion. They mean perpetual dominion.... There is not one of these\
gentlemen who will rise in his place and affirm that if he were a\
Filipino he would not do exactly as the Filipinos are doing; that he\
would not despise them if they were to do otherwise. So much at least\
they owe of respect to the dead and buried history--the dead and buried\
history so far as they can slay and bury it--of their country." In the\
way of practical suggestions, the Senator offered as a solution of the\
problem: the recognition of independence, assistance in establishing\
self-government, and an invitation to all powers to join in a guarantee\
of freedom to the islands.\
\
=The Republican Answer.=--To McKinley and his supporters, engaged in a\
sanguinary struggle to maintain American supremacy, such talk was more\
than quixotic; it was scarcely short of treasonable. They pointed out\
the practical obstacles in the way of uniform self-government for a\
collection of seven million people ranging in civilization from the most\
ignorant hill men to the highly cultivated inhabitants of Manila. The\
incidents of the revolt and its repression, they admitted, were painful\
enough; but still nothing as compared with the chaos that would follow\
the attempt of a people who had never had experience in such matters to\
set up and sustain democratic institutions. They preferred rather the\
gradual process of fitting the inhabitants of the islands for\
self-government. This course, in their eyes, though less poetic, was\
more in harmony with the ideals of humanity. Having set out upon it,\
they pursued it steadfastly to the end. First, they applied force\
without stint to the suppression of the revolt. Then they devoted such\
genius for colonial administration as they could command to the\
development of civil government, commerce, and industry.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
A PHILIPPINE HOME]\
\
=The Boxer Rebellion in China.=--For a nation with a world-wide trade,\
steadily growing, as the progress of home industries redoubled the zeal\
for new markets, isolation was obviously impossible. Never was this\
clearer than in 1900 when a native revolt against foreigners in China,\
known as the Boxer uprising, compelled the United States to join with\
the powers of Europe in a military expedition and a diplomatic\
settlement. The Boxers, a Chinese association, had for some time carried\
on a campaign of hatred against all aliens in the Celestial empire,\
calling upon the natives to rise in patriotic wrath and drive out the\
foreigners who, they said, "were lacerating China like tigers." In the\
summer of 1900 the revolt flamed up in deeds of cruelty. Missionaries\
and traders were murdered in the provinces; foreign legations were\
stoned; the German ambassador, one of the most cordially despised\
foreigners, was killed in the streets of Peking; and to all appearances\
a frightful war of extermination had begun. In the month of June nearly\
five hundred men, women, and children, representing all nations, were\
besieged in the British quarters in Peking under constant fire of\
Chinese guns and in peril of a terrible death.\
\
=Intervention in China.=--Nothing but the arrival of armed forces, made\
up of Japanese, Russian, British, American, French, and German soldiers\
and marines, prevented the destruction of the beleaguered aliens. When\
once the foreign troops were in possession of the Chinese capital,\
diplomatic questions of the most delicate character arose. For more than\
half a century, the imperial powers of Europe had been carving up the\
Chinese empire, taking to themselves territory, railway concessions,\
mining rights, ports, and commercial privileges at the expense of the\
huge but helpless victim. The United States alone among the great\
nations, while as zealous as any in the pursuit of peaceful trade, had\
refrained from seizing Chinese territory or ports. Moreover, the\
Department of State had been urging European countries to treat China\
with fairness, to respect her territorial integrity, and to give her\
equal trading privileges with all nations.\
\
=The American Policy of the "Open Door."=--In the autumn of 1899,\
Secretary Hay had addressed to London, Berlin, Rome, Paris, Tokyo, and\
St. Petersburg his famous note on the "open door" policy in China. In\
this document he proposed that existing treaty ports and vested\
interests of the several foreign countries should be respected; that\
the Chinese government should be permitted to extend its tariffs to all\
ports held by alien powers except the few free ports; and that there\
should be no discrimination in railway and port charges among the\
citizens of foreign countries operating in the empire. To these\
principles the governments addressed by Mr. Hay, finally acceded with\
evident reluctance.\
\
[Illustration: AMERICAN DOMINIONS IN THE PACIFIC]\
\
On this basis he then proposed the settlement that had to follow the\
Boxer uprising. "The policy of the Government of the United States," he\
said to the great powers, in the summer of 1900, "is to seek a solution\
which may bring about permanent safety and peace to China, preserve\
Chinese territorial and administrative entity, protect all rights\
guaranteed to friendly powers by treaty and international law, and\
safeguard for the world the principle of equal and impartial trade with\
all parts of the Chinese empire." This was a friendly warning to the\
world that the United States would not join in a scramble to punish the\
Chinese by carving out more territory. "The moment we acted," said Mr.\
Hay, "the rest of the world paused and finally came over to our ground;\
and the German government, which is generally brutal but seldom silly,\
recovered its senses, and climbed down off its perch."\
\
In taking this position, the Secretary of State did but reflect the\
common sense of America. "We are, of course," he explained, "opposed to\
the dismemberment of that empire and we do not think that the public\
opinion of the United States would justify this government in taking\
part in the great game of spoliation now going on." Heavy damages were\
collected by the European powers from China for the injuries inflicted\
upon their citizens by the Boxers; but the United States, finding the\
sum awarded in excess of the legitimate claims, returned the balance in\
the form of a fund to be applied to the education of Chinese students in\
American universities. "I would rather be, I think," said Mr. Hay, "the\
dupe of China than the chum of the Kaiser." By pursuing a liberal\
policy, he strengthened the hold of the United States upon the\
affections of the Chinese people and, in the long run, as he remarked\
himself, safeguarded "our great commercial interests in that Empire."\
\
=Imperialism in the Presidential Campaign of 1900.=--It is not strange\
that the policy pursued by the Republican administration in disposing of\
the questions raised by the Spanish War became one of the first issues\
in the presidential campaign of 1900. Anticipating attacks from every\
quarter, the Republicans, in renominating McKinley, set forth their\
position in clear and ringing phrases: "In accepting by the treaty of\
Paris the just responsibility of our victories in the Spanish War the\
President and Senate won the undoubted approval of the American people.\
No other course was possible than to destroy Spain's sovereignty\
throughout the West Indies and in the Philippine Islands. That course\
created our responsibility, before the world and with the unorganized\
population whom our intervention had freed from Spain, to provide for\
the maintenance of law and order, and for the establishment of good\
government and for the performance of international obligations. Our\
authority could not be less than our responsibility, and wherever\
sovereign rights were extended it became the high duty of the government\
to maintain its authority, to put down armed insurrection, and to confer\
the blessings of liberty and civilization upon all the rescued peoples.\
The largest measure of self-government consistent with their welfare and\
our duties shall be secured to them by law." To give more strength to\
their ticket, the Republican convention, in a whirlwind of enthusiasm,\
nominated for the vice presidency, against his protest, Theodore\
Roosevelt, the governor of New York and the hero of the Rough Riders, so\
popular on account of their Cuban campaign.\
\
The Democrats, as expected, picked up the gauntlet thrown down with such\
defiance by the Republicans. Mr. Bryan, whom they selected as their\
candidate, still clung to the currency issue; but the main emphasis,\
both of the platform and the appeal for votes, was on the "imperialistic\
program" of the Republican administration. The Democrats denounced the\
treatment of Cuba and Porto Rico and condemned the Philippine policy in\
sharp and vigorous terms. "As we are not willing," ran the platform, "to\
surrender our civilization or to convert the Republic into an empire, we\
favor an immediate declaration of the Nation's purpose to give to the\
Filipinos, first, a stable form of government; second, independence;\
third, protection from outside interference.... The greedy commercialism\
which dictated the Philippine policy of the Republican administration\
attempts to justify it with the plea that it will pay, but even this\
sordid and unworthy plea fails when brought to the test of facts. The\
war of 'criminal aggression' against the Filipinos entailing an annual\
expense of many millions has already cost more than any possible profit\
that could accrue from the entire Philippine trade for years to come....\
We oppose militarism. It means conquest abroad and intimidation and\
oppression at home. It means the strong arm which has ever been fatal to\
free institutions. It is what millions of our citizens have fled from in\
Europe. It will impose upon our peace-loving people a large standing\
army, an unnecessary burden of taxation, and would be a constant menace\
to their liberties." Such was the tenor of their appeal to the voters.\
\
With the issues clearly joined, the country rejected the Democratic\
candidate even more positively than four years before. The popular vote\
cast for McKinley was larger and that cast for Bryan smaller than in the\
silver election. Thus vindicated at the polls, McKinley turned with\
renewed confidence to the development of the policies he had so far\
advanced. But fate cut short his designs. In the September following his\
second inauguration, he was shot by an anarchist while attending the\
Buffalo exposition. "What a strange and tragic fate it has been of\
mine," wrote the Secretary of State, John Hay, on the day of the\
President's death, "to stand by the bier of three of my dearest friends,\
Lincoln, Garfield, and McKinley, three of the gentlest of men, all risen\
to the head of the state and all done to death by assassins." On\
September 14, 1901, the Vice President, Theodore Roosevelt, took up the\
lines of power that had fallen from the hands of his distinguished\
chief, promising to continue "absolutely unbroken" the policies he had\
inherited.\
\
\
SUMMARY OF NATIONAL GROWTH AND WORLD POLITICS\
\
The economic aspects of the period between 1865 and 1900 may be readily\
summed up: the recovery of the South from the ruin of the Civil War, the\
extension of the railways, the development of the Great West, and the\
triumph of industry and business enterprise. In the South many of the\
great plantations were broken up and sold in small farms, crops were\
diversified, the small farming class was raised in the scale of social\
importance, the cotton industry was launched, and the coal, iron,\
timber, and other resources were brought into use. In the West the free\
arable land was practically exhausted by 1890 under the terms of the\
Homestead Act; gold, silver, copper, coal and other minerals were\
discovered in abundance; numerous rail connections were formed with the\
Atlantic seaboard; the cowboy and the Indian were swept away before a\
standardized civilization of electric lights and bathtubs. By the end of\
the century the American frontier had disappeared. The wild, primitive\
life so long associated with America was gone. The unity of the nation\
was established.\
\
In the field of business enterprise, progress was most marked. The\
industrial system, which had risen and flourished before the Civil War,\
grew into immense proportions and the industrial area was extended from\
the Northeast into all parts of the country. Small business concerns\
were transformed into huge corporations. Individual plants were merged\
under the management of gigantic trusts. Short railway lines were\
consolidated into national systems. The industrial population of\
wage-earners rose into the tens of millions. The immigration of aliens\
increased by leaps and bounds. The cities overshadowed the country. The\
nation that had once depended upon Europe for most of its manufactured\
goods became a competitor of Europe in the markets of the earth.\
\
In the sphere of politics, the period witnessed the recovery of white\
supremacy in the South; the continued discussion of the old questions,\
such as the currency, the tariff, and national banking; and the\
injection of new issues like the trusts and labor problems. As of old,\
foreign affairs were kept well at the front. Alaska was purchased from\
Russia; attempts were made to extend American influence in the Caribbean\
region; a Samoan island was brought under the flag; and the Hawaiian\
islands were annexed. The Monroe Doctrine was applied with vigor in the\
dispute between Venezuela and Great Britain.\
\
Assistance was given to the Cubans in their revolutionary struggle\
against Spain and thus there was precipitated a war which ended in the\
annexation of Porto Rico and the Philippines. American influence in the\
Pacific and the Orient was so enlarged as to be a factor of great weight\
in world affairs. Thus questions connected with foreign and "imperial"\
policies were united with domestic issues to make up the warp and woof\
of politics. In the direction of affairs, the Republicans took the\
leadership, for they held the presidency during all the years, except\
eight, between 1865 and 1900.\
\
\
=References=\
\
J.W. Foster, _A Century of American Diplomacy_; _American Diplomacy in\
the Orient_.\
\
W.F. Reddaway, _The Monroe Doctrine_.\
\
J.H. Latane, _The United States and Spanish America_.\
\
A.C. Coolidge, _United States as a World Power_.\
\
A.T. Mahan, _Interest of the United States in the Sea Power_.\
\
F.E. Chadwick, _Spanish-American War_.\
\
D.C. Worcester, _The Philippine Islands and Their People_.\
\
M.M. Kalaw, _Self-Government in the Philippines_.\
\
L.S. Rowe, _The United States and Porto Rico_.\
\
F.E. Chadwick, _The Relations of the United States and Spain_.\
\
W.R. Shepherd, _Latin America_; _Central and South America_.\
\
\
=Questions=\
\
1. Tell the story of the international crisis that developed soon after\
the Civil War with regard to Mexico.\
\
2. Give the essential facts relating to the purchase of Alaska.\
\
3. Review the early history of our interest in the Caribbean.\
\
4. Amid what circumstances was the Monroe Doctrine applied in\
Cleveland's administration?\
\
5. Give the causes that led to the war with Spain.\
\
6. Tell the leading events in that war.\
\
7. What was the outcome as far as Cuba was concerned? The outcome for\
the United States?\
\
8. Discuss the attitude of the Filipinos toward American sovereignty in\
the islands.\
\
9. Describe McKinley's colonial policy.\
\
10. How was the Spanish War viewed in England? On the Continent?\
\
11. Was there a unified American opinion on American expansion?\
\
12. Was this expansion a departure from our traditions?\
\
13. What events led to foreign intervention in China?\
\
14. Explain the policy of the "open door."\
\
\
=Research Topics=\
\
=Hawaii and Venezuela.=--Dewey, _National Problems_ (American Nation\
Series), pp. 279-313; Macdonald, _Documentary Source Book_, pp. 600-602;\
Hart, _American History Told by Contemporaries_, Vol. IV, pp. 612-616.\
\
=Intervention in Cuba.=--Latane, _America as a World Power_ (American\
Nation Series), pp. 3-28; Macdonald, _Documentary Source Book_, pp.\
597-598; Roosevelt, _Autobiography_, pp. 223-277; Haworth, _The United\
States in Our Own Time_, pp. 232-256; Hart, _Contemporaries_, Vol. IV,\
pp. 573-578.\
\
=The War with Spain.=--Elson, _History of the United States_, pp.\
889-896.\
\
=Terms of Peace with Spain.=--Latane, pp. 63-81; Macdonald, pp. 602-608;\
Hart, _Contemporaries_, Vol. IV, pp. 588-590.\
\
=The Philippine Insurrection.=--Latane, pp. 82-99.\
\
=Imperialism as a Campaign Issue.=--Latane, pp. 120-132; Haworth, pp.\
257-277; Hart, _Contemporaries_, Vol. IV, pp. 604-611.\
\
=Biographical Studies.=--William McKinley, M.A. Hanna, John Hay;\
Admirals, George Dewey, W.T. Sampson, and W.S. Schley; and Generals,\
W.R. Shafter, Joseph Wheeler, and H.W. Lawton.\
\
=General Analysis of American Expansion.=--_Syllabus in History_ (New\
York State, 1920), pp. 142-147.\
\
\
\
\
PART VII. PROGRESSIVE DEMOCRACY AND THE WORLD WAR\
\
\
\
\
CHAPTER XXI\
\
THE EVOLUTION OF REPUBLICAN POLICIES (1901-13)\
\
\
=The Personality and Early Career of Roosevelt.=--On September 14, 1901,\
when Theodore Roosevelt took the oath of office, the presidency passed\
to a new generation and a leader of a new type recalling, if comparisons\
must be made, Andrew Jackson rather than any Republican predecessor.\
Roosevelt was brusque, hearty, restless, and fond of action--"a young\
fellow of infinite dash and originality," as John Hay remarked of him;\
combining the spirit of his old college, Harvard, with the breezy\
freedom of the plains; interested in everything--a new species of game,\
a new book, a diplomatic riddle, or a novel theory of history or\
biology. Though only forty-three years old he was well versed in the art\
of practical politics. Coming upon the political scene in the early\
eighties, he had associated himself with the reformers in the Republican\
party; but he was no Mugwump. From the first he vehemently preached the\
doctrine of party loyalty; if beaten in the convention, he voted the\
straight ticket in the election. For twenty years he adhered to this\
rule and during a considerable portion of that period he held office as\
a spokesman of his party. He served in the New York legislature, as head\
of the metropolitan police force, as federal civil service commissioner\
under President Harrison, as assistant secretary of the navy under\
President McKinley, and as governor of the Empire state. Political\
managers of the old school spoke of him as "brilliant but erratic"; they\
soon found him equal to the shrewdest in negotiation and action.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
ROOSEVELT TALKING TO THE ENGINEER OF A RAILROAD TRAIN]\
\
\
FOREIGN AFFAIRS\
\
=The Panama Canal.=--The most important foreign question confronting\
President Roosevelt on the day of his inauguration, that of the Panama\
Canal, was a heritage from his predecessor. The idea of a water route\
across the isthmus, long a dream of navigators, had become a living\
issue after the historic voyage of the battleship _Oregon_ around South\
America during the Spanish War. But before the United States could act\
it had to undo the Clayton-Bulwer treaty, made with Great Britain in\
1850, providing for the construction of the canal under joint\
supervision. This was finally effected by the Hay-Pauncefote treaty of\
1901 authorizing the United States to proceed alone, on condition that\
there should be no discriminations against other nations in the matter\
of rates and charges.\
\
This accomplished, it was necessary to decide just where the canal\
should be built. One group in Congress favored the route through\
Nicaragua; in fact, two official commissions had already approved that\
location. Another group favored cutting the way through Panama after\
purchasing the rights of the old French company which, under the\
direction of De Lesseps, the hero of the Suez Canal, had made a costly\
failure some twenty years before. After a heated argument over the\
merits of the two plans, preference was given to the Panama route. As\
the isthmus was then a part of Colombia, President Roosevelt proceeded\
to negotiate with the government at Bogota a treaty authorizing the\
United States to cut a canal through its territory. The treaty was\
easily framed, but it was rejected by the Colombian senate, much to the\
President's exasperation. "You could no more make an agreement with the\
Colombian rulers," he exclaimed, "than you could nail jelly to a wall."\
He was spared the necessity by a timely revolution. On November 3, 1903,\
Panama renounced its allegiance to Colombia and three days later the\
United States recognized its independence.\
\
[Illustration: _Courtesy of Panama Canal, Washington, D.C._\
\
DEEPEST EXCAVATED PORTION OF PANAMA CANAL, SHOWING GOLD HILL ON\
RIGHT AND CONTRACTOR'S HILL ON LEFT. JUNE, 1913]\
\
This amazing incident was followed shortly by the signature of a treaty\
between Panama and the United States in which the latter secured the\
right to construct the long-discussed canal, in return for a guarantee\
of independence and certain cash payments. The rights and property of\
the French concern were then bought, and the final details settled. A\
lock rather than a sea-level canal was agreed upon. Construction by the\
government directly instead of by private contractors was adopted.\
Scientific medicine was summoned to stamp out the tropical diseases\
that had made Panama a plague spot. Finally, in 1904, as the President\
said, "the dirt began to fly." After surmounting formidable\
difficulties--engineering, labor, and sanitary--the American forces in\
1913 joined the waters of the Atlantic and the Pacific. Nearly eight\
thousand miles were cut off the sea voyage from New York to San\
Francisco. If any were inclined to criticize President Roosevelt for\
the way in which he snapped off negotiations with Colombia and\
recognized the Panama revolutionists, their attention was drawn to the\
magnificent outcome of the affair. Notwithstanding the treaty with Great\
Britain, Congress passed a tolls bill discriminating in rates in favor\
of American ships. It was only on the urgent insistence of President\
Wilson that the measure was later repealed.\
\
=The Conclusion of the Russo-Japanese War.=--The applause which greeted\
the President's next diplomatic stroke was unmarred by censure of any\
kind. In the winter of 1904 there broke out between Japan and Russia a\
terrible conflict over the division of spoils in Manchuria. The fortunes\
of war were with the agile forces of Nippon. In this struggle, it seems,\
President Roosevelt's sympathies were mainly with the Japanese, although\
he observed the proprieties of neutrality. At all events, Secretary Hay\
wrote in his diary on New Year's Day, 1905, that the President was\
"quite firm in his view that we cannot permit Japan to be robbed a\
second time of her victory," referring to the fact that Japan, ten years\
before, after defeating China on the field of battle, had been forced by\
Russia, Germany, and France to forego the fruits of conquest.\
\
Whatever the President's personal feelings may have been, he was aware\
that Japan, despite her triumphs over Russia, was staggering under a\
heavy burden of debt. At a suggestion from Tokyo, he invited both\
belligerents in the summer of 1905 to join in a peace conference. The\
celerity of their reply was aided by the pressure of European bankers,\
who had already come to a substantial agreement that the war must stop.\
After some delay, Portsmouth, New Hampshire, was chosen as the meeting\
place for the spokesmen of the two warring powers. Roosevelt presided\
over the opening ceremonies with fine urbanity, thoroughly enjoying the\
justly earned honor of being for the moment at the center of the world's\
interest. He had the satisfaction of seeing the conference end in a\
treaty of peace and amity.\
\
=The Monroe Doctrine Applied to Germany.=--Less spectacular than the\
Russo-Japanese settlement but not less important was a diplomatic\
passage-at-arms with Germany over the Monroe Doctrine. This clash grew\
out of the inability or unwillingness of the Venezuelan government to\
pay debts due foreign creditors. Having exhausted their patience in\
negotiations, England and Germany, in December 1901, sent battleships to\
establish what they characterized as "a peaceful blockade" of Venezuelan\
ports. Their action was followed by the rupture of diplomatic relations;\
there was a possibility that war and the occupation of Venezuelan\
territory might result.\
\
While unwilling to stand between a Latin-American country and its\
creditors, President Roosevelt was determined that debt collecting\
should not be made an excuse for European countries to seize territory.\
He therefore urged arbitration of the dispute, winning the assent of\
England and Italy. Germany, with a somewhat haughty air, refused to take\
the milder course. The President, learning of this refusal, called the\
German ambassador to the White House and informed him in very precise\
terms that, unless the Imperial German Government consented to\
arbitrate, Admiral Dewey would be ordered to the scene with instructions\
to prevent Germany from seizing any Venezuelan territory. A week passed\
and no answer came from Berlin. Not baffled, the President again took\
the matter up with the ambassador, this time with even more firmness; he\
stated in language admitting of but one meaning that, unless within\
forty-eight hours the Emperor consented to arbitration, American\
battleships, already coaled and cleared, would sail for Venezuelan\
waters. The hint was sufficient. The Kaiser accepted the proposal and\
the President, with the fine irony of diplomacy, complimented him\
publicly on "being so stanch an advocate of arbitration." In terms of\
the Monroe Doctrine this action meant that the United States, while not\
denying the obligations of debtors, would not permit any move on the\
part of European powers that might easily lead to the temporary or\
permanent occupation of Latin-American territory.\
\
=The Santo Domingo Affair.=--The same issue was involved in a\
controversy over Santo Domingo which arose in 1904. The Dominican\
republic, like Venezuela, was heavily in debt, and certain European\
countries declared that, unless the United States undertook to look\
after the finances of the embarrassed debtor, they would resort to armed\
coercion. What was the United States to do? The danger of having some\
European power strongly intrenched in Santo Domingo was too imminent to\
be denied. President Roosevelt acted with characteristic speed, and\
notwithstanding strong opposition in the Senate was able, in 1907, to\
effect a treaty arrangement which placed Dominican finances under\
American supervision.\
\
In the course of the debate over this settlement, a number of\
interesting questions arose. It was pertinently asked whether the\
American navy should be used to help creditors collect their debts\
anywhere in Latin-America. It was suggested also that no sanction should\
be given to the practice among European governments of using armed force\
to collect private claims. Opponents of President Roosevelt's policy,\
and they were neither few nor insignificant, urged that such matters\
should be referred to the Hague Court or to special international\
commissions for arbitration. To this the answer was made that the United\
States could not surrender any question coming under the terms of the\
Monroe Doctrine to the decision of an international tribunal. The\
position of the administration was very clearly stated by President\
Roosevelt himself. "The country," he said, "would certainly decline to\
go to war to prevent a foreign government from collecting a just debt;\
on the other hand, it is very inadvisable to permit any foreign power to\
take possession, even temporarily, of the customs houses of an American\
republic in order to enforce the payment of its obligations; for such a\
temporary occupation might turn into a permanent occupation. The only\
escape from these alternatives may at any time be that we must\
ourselves undertake to bring about some arrangement by which so much as\
possible of a just obligation shall be paid." The Monroe Doctrine was\
negative. It denied to European powers a certain liberty of operation in\
this hemisphere. The positive obligations resulting from its application\
by the United States were points now emphasized and developed.\
\
=The Hague Conference.=--The controversies over Latin-American relations\
and his part in bringing the Russo-Japanese War to a close naturally\
made a deep impression upon Roosevelt, turning his mind in the direction\
of the peaceful settlement of international disputes. The subject was\
moreover in the air. As if conscious of impending calamity, the\
statesmen of the Old World, to all outward signs at least, seemed\
searching for a way to reduce armaments and avoid the bloody and costly\
trial of international causes by the ancient process of battle. It was\
the Czar, Nicholas II, fated to die in one of the terrible holocausts\
which he helped to bring upon mankind, who summoned the delegates of the\
nations in the first Hague Peace Conference in 1899. The conference did\
nothing to reduce military burdens or avoid wars but it did recognize\
the right of friendly nations to offer the services of mediation to\
countries at war and did establish a Court at the Hague for the\
arbitration of international disputes.\
\
Encouraged by this experiment, feeble as it was, President Roosevelt in\
1904 proposed a second conference, yielding to the Czar the honor of\
issuing the call. At this great international assembly, held at the\
Hague in 1907, the representatives of the United States proposed a plan\
for the compulsory arbitration of certain matters of international\
dispute. This was rejected with contempt by Germany. Reduction of\
armaments, likewise proposed in the conference, was again deferred. In\
fact, nothing was accomplished beyond agreement upon certain rules for\
the conduct of "civilized warfare," casting a somewhat lurid light upon\
the "pacific" intentions of most of the powers assembled.\
\
=The World Tour of the Fleet.=--As if to assure the world then that the\
United States placed little reliance upon the frail reed of peace\
conferences, Roosevelt the following year (1908) made an imposing\
display of American naval power by sending a fleet of sixteen\
battleships on a tour around the globe. On his own authority, he ordered\
the ships to sail out of Hampton Roads and circle the earth by way of\
the Straits of Magellan, San Francisco, Australia, the Philippines,\
China, Japan, and the Suez Canal. This enterprise was not, as some\
critics claimed, a "mere boyish flourish." President Roosevelt knew how\
deep was the influence of sea power on the fate of nations. He was aware\
that no country could have a wide empire of trade and dominion without\
force adequate to sustain it. The voyage around the world therefore\
served a double purpose. It interested his own country in the naval\
program of the government, and it reminded other powers that the\
American giant, though quiet, was not sleeping in the midst of\
international rivalries.\
\
\
COLONIAL ADMINISTRATION\
\
=A Constitutional Question Settled.=--In colonial administration, as in\
foreign policy, President Roosevelt advanced with firm step in a path\
already marked out. President McKinley had defined the principles that\
were to control the development of Porto Rico and the Philippines. The\
Republican party had announced a program of pacification, gradual\
self-government, and commercial improvement. The only remaining question\
of importance, to use the popular phrase,--"Does the Constitution follow\
the flag?"--had been answered by the Supreme Court of the United States.\
Although it was well known that the Constitution did not contemplate the\
government of dependencies, such as the Philippines and Porto Rico, the\
Court, by generous and ingenious interpretations, found a way for\
Congress to apply any reasonable rules required by the occasion.\
\
=Porto Rico.=--The government of Porto Rico was a relatively simple\
matter. It was a single island with a fairly homogeneous population\
apart from the Spanish upper class. For a time after military occupation\
in 1898, it was administered under military rule. This was succeeded by\
the establishment of civil government under the "organic act" passed by\
Congress in 1900. The law assured to the Porto Ricans American\
protection but withheld American citizenship--a boon finally granted in\
1917. It provided for a governor and six executive secretaries appointed\
by the President with the approval of the Senate; and for a legislature\
of two houses--one elected by popular native vote, and an upper chamber\
composed of the executive secretaries and five other persons appointed\
in the same manner. Thus the United States turned back to the provincial\
system maintained by England in Virginia or New York in old colonial\
days. The natives were given a voice in their government and the power\
of initiating laws; but the final word both in law-making and\
administration was vested in officers appointed in Washington. Such was\
the plan under which the affairs of Porto Rico were conducted by\
President Roosevelt. It lasted until the new organic act of 1917.\
\
[Illustration: _Photograph from Underwood and Underwood, N.Y._\
\
A SUGAR MILL, PORTO RICO]\
\
=The Philippines.=--The administration of the Philippines presented far\
more difficult questions. The number of islands, the variety of\
languages and races, the differences in civilization all combined to\
challenge the skill of the government. Moreover, there was raging in\
1901 a stubborn revolt against American authority, which had to be\
faced. Following the lines laid down by President McKinley, the\
evolution of American policy fell into three stages. At first the\
islands were governed directly by the President under his supreme\
military power. In 1901 a civilian commission, headed by William Howard\
Taft, was selected by the President and charged with the government of\
the provinces in which order had been restored. Six years later, under\
the terms of an organic act, passed by Congress in 1902, the third stage\
was reached. The local government passed into the hands of a governor\
and commission, appointed by the President and Senate, and a\
legislature--one house elected by popular vote and an upper chamber\
\
composed of the commission. This scheme, like that obtaining in Porto\
Rico, remained intact until a Democratic Congress under President\
Wilson's leadership carried the colonial administration into its fourth\
phase by making both houses elective. Thus, by the steady pursuit of a\
liberal policy, self-government was extended to the dependencies; but it\
encouraged rather than extinguished the vigorous movement among the\
Philippine natives for independence.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
MR TAFT IN THE PHILIPPINES]\
\
=Cuban Relations.=--Within the sphere of colonial affairs, Cuba, though\
nominally independent, also presented problems to the government at\
Washington. In the fine enthusiasm that accompanied the declaration of\
war on Spain, Congress, unmindful of practical considerations,\
recognized the independence of Cuba and disclaimed "any disposition or\
intention to exercise sovereignty, jurisdiction, or control over said\
island except for the pacification thereof." In the settlement that\
followed the war, however, it was deemed undesirable to set the young\
republic adrift upon the stormy sea of international politics without a\
guiding hand. Before withdrawing American troops from the island,\
Congress, in March, 1901, enacted, and required Cuba to approve, a\
series of restrictions known as the Platt amendment, limiting her power\
to incur indebtedness, securing the right of the United States to\
intervene whenever necessary to protect life and property, and reserving\
to the United States coaling stations at certain points to be agreed\
upon. The Cubans made strong protests against what they deemed\
"infringements of their sovereignty"; but finally with good grace\
accepted their fate. Even when in 1906 President Roosevelt landed\
American troops in the island to quell a domestic dissension, they\
acquiesced in the action, evidently regarding it as a distinct warning\
that they should learn to manage their elections in an orderly manner.\
\
\
THE ROOSEVELT DOMESTIC POLICIES\
\
=Social Questions to the Front.=--From the day of his inauguration to\
the close of his service in 1909, President Roosevelt, in messages,\
speeches, and interviews, kept up a lively and interesting discussion of\
trusts, capital, labor, poverty, riches, lawbreaking, good citizenship,\
and kindred themes. Many a subject previously touched upon only by\
representatives of the minor and dissenting parties, he dignified by a\
careful examination. That he did this with any fixed design or policy in\
mind does not seem to be the case. He admitted himself that when he\
became President he did not have in hand any settled or far-reaching\
plan of social betterment. He did have, however, serious convictions on\
general principles. "I was bent upon making the government," he wrote,\
"the most efficient possible instrument in helping the people of the\
United States to better themselves in every way, politically, socially,\
and industrially. I believed with all my heart in real and\
thorough-going democracy and I wished to make the democracy industrial\
as well as political, although I had only partially formulated the\
method I believed we should follow." It is thus evident at least that he\
had departed a long way from the old idea of the government as nothing\
but a great policeman keeping order among the people in a struggle over\
the distribution of the nation's wealth and resources.\
\
=Roosevelt's View of the Constitution.=--Equally significant was\
Roosevelt's attitude toward the Constitution and the office of\
President. He utterly repudiated the narrow construction of our national\
charter. He held that the Constitution "should be treated as the\
greatest document ever devised by the wit of man to aid a people in\
exercising every power necessary for its own betterment, not as a\
strait-jacket cunningly fashioned to strangle growth." He viewed the\
presidency as he did the Constitution. Strict constructionists of the\
Jeffersonian school, of whom there were many on occasion even in the\
Republican party, had taken a view that the President could do nothing\
that he was not specifically authorized by the Constitution to do.\
Roosevelt took exactly the opposite position. It was his opinion that it\
was not only the President's right but his duty "to do anything that the\
needs of the nation demanded unless such action was forbidden by the\
Constitution or the laws." He went on to say that he acted "for the\
common well-being of all our people whenever and in whatever manner was\
necessary, unless prevented by direct constitutional or legislative\
prohibition."\
\
=The Trusts and Railways.=--To the trust question, Roosevelt devoted\
especial attention. This was unavoidable. By far the larger part of the\
business of the country was done by corporations as distinguished from\
partnerships and individual owners. The growth of these gigantic\
aggregations of capital had been the leading feature in American\
industrial development during the last two decades of the nineteenth\
century. In the conquest of business by trusts and "the resulting\
private fortunes of great magnitude," the Populists and the Democrats\
had seen a grievous danger to the republic. "Plutocracy has taken the\
place of democracy; the tariff breeds trusts; let us destroy therefore\
the tariff and the trusts"--such was the battle cry which had been taken\
up by Bryan and his followers.\
\
President Roosevelt countered vigorously. He rejected the idea that the\
trusts were the product of the tariff or of governmental action of any\
kind. He insisted that they were the outcome of "natural economic\
forces": (1) destructive competition among business men compelling them\
to avoid ruin by cooperation in fixing prices; (2) the growth of markets\
on a national scale and even international scale calling for vast\
accumulations of capital to carry on such business; (3) the possibility\
of immense savings by the union of many plants under one management. In\
the corporation he saw a new stage in the development of American\
industry. Unregulated competition he regarded as "the source of evils\
which all men concede must be remedied if this civilization of ours is\
to survive." The notion, therefore, that these immense business concerns\
should be or could be broken up by a decree of law, Roosevelt considered\
absurd.\
\
At the same time he proposed that "evil trusts" should be prevented from\
"wrong-doing of any kind"; that is, punished for plain swindling, for\
making agreements to limit output, for refusing to sell to customers who\
dealt with rival firms, and for conspiracies with railways to ruin\
competitors by charging high freight rates and for similar abuses.\
Accordingly, he proposed, not the destruction of the trusts, but their\
regulation by the government. This, he contended, would preserve the\
advantages of business on a national scale while preventing the evils\
that accompanied it. The railway company he declared to be a public\
servant. "Its rates should be just to and open to all shippers alike."\
So he answered those who thought that trusts and railway combinations\
were private concerns to be managed solely by their owners without let\
or hindrance and also those who thought trusts and railway combinations\
could be abolished by tariff reduction or criminal prosecution.\
\
=The Labor Question.=--On the labor question, then pressing to the front\
in public interest, President Roosevelt took advanced ground for his\
time. He declared that the working-man, single-handed and empty-handed,\
threatened with starvation if unemployed, was no match for the employer\
who was able to bargain and wait. This led him, accordingly, to accept\
the principle of the trade union; namely, that only by collective\
bargaining can labor be put on a footing to measure its strength equally\
with capital. While he severely arraigned labor leaders who advocated\
violence and destructive doctrines, he held that "the organization of\
labor into trade unions and federations is necessary, is beneficent, and\
is one of the greatest possible agencies in the attainment of a true\
industrial, as well as a true political, democracy in the United\
States." The last resort of trade unions in labor disputes, the strike,\
he approved in case negotiations failed to secure "a fair deal."\
\
He thought, however, that labor organizations, even if wisely managed,\
could not solve all the pressing social questions of the time. The aid\
of the government at many points he believed to be necessary to\
eliminate undeserved poverty, industrial diseases, unemployment, and the\
unfortunate consequences of industrial accidents. In his first message\
of 1901, for instance, he urged that workers injured in industry should\
have certain and ample compensation. From time to time he advocated\
other legislation to obtain what he called "a larger measure of social\
and industrial justice."\
\
=Great Riches and Taxation.=--Even the challenge of the radicals, such\
as the Populists, who alleged that "the toil of millions is boldly\
stolen to build up colossal fortunes for a few"--challenges which his\
predecessors did not consider worthy of notice--President Roosevelt\
refused to let pass without an answer. In his first message he denied\
the truth of the common saying that the rich were growing richer and the\
poor were growing poorer. He asserted that, on the contrary, the average\
man, wage worker, farmer, and small business man, was better off than\
ever before in the history of our country. That there had been abuses in\
the accumulation of wealth he did not pretend to ignore, but he believed\
that even immense fortunes, on the whole, represented positive benefits\
conferred upon the country. Nevertheless he felt that grave dangers to\
the safety and the happiness of the people lurked in great inequalities\
of wealth. In 1906 he wrote that he wished it were in his power to\
prevent the heaping up of enormous fortunes. The next year, to the\
astonishment of many leaders in his own party, he boldly announced in a\
message to Congress that he approved both income and inheritance taxes,\
then generally viewed as Populist or Democratic measures. He even took\
the stand that such taxes should be laid in order to bring about a more\
equitable distribution of wealth and greater equality of opportunity\
among citizens.\
\
\
LEGISLATIVE AND EXECUTIVE ACTIVITIES\
\
=Economic Legislation.=--When President Roosevelt turned from the field\
of opinion he found himself in a different sphere. Many of his views\
were too advanced for the members of his party in Congress, and where\
results depended upon the making of new laws, his progress was slow.\
Nevertheless, in his administrations several measures were enacted that\
bore the stamp of his theories, though it could hardly be said that he\
dominated Congress to the same degree as did some other Presidents. The\
Hepburn Railway Act of 1906 enlarged the interstate commerce commission;\
it extended the commission's power over oil pipe lines, express\
companies, and other interstate carriers; it gave the commission the\
right to reduce rates found to be unreasonable and discriminatory; it\
forbade "midnight tariffs," that is, sudden changes in rates favoring\
certain shippers; and it prohibited common carriers from transporting\
goods owned by themselves, especially coal, except for their own proper\
use. Two important pure food and drug laws, enacted during the same\
year, were designed to protect the public against diseased meats and\
deleterious foods and drugs. A significant piece of labor legislation\
was an act of the same Congress making interstate railways liable to\
damages for injuries sustained by their employees. When this measure was\
declared unconstitutional by the Supreme Court it was reenacted with the\
objectionable clauses removed. A second installment of labor legislation\
was offered in the law of 1908 limiting the hours of railway employees\
engaged as trainmen or telegraph operators.\
\
[Illustration: _Courtesy United States Reclamation Service._\
\
THE ROOSEVELT DAM, PHOENIX, ARIZONA]\
\
=Reclamation and Conservation.=--The open country--the deserts, the\
forests, waterways, and the public lands--interested President Roosevelt\
no less than railway and industrial questions. Indeed, in his first\
message to Congress he placed the conservation of natural resources\
among "the most vital internal problems" of the age, and forcibly\
emphasized an issue that had been discussed in a casual way since\
Cleveland's first administration. The suggestion evoked an immediate\
response in Congress. Under the leadership of Senator Newlands, of\
Nevada, the Reclamation Act of 1902 was passed, providing for the\
redemption of the desert areas of the West. The proceeds from the sale\
of public lands were dedicated to the construction of storage dams and\
sluiceways to hold water and divert it as needed to the thirsty sands.\
Furthermore it was stipulated that the rents paid by water users should\
go into a reclamation fund to continue the good work forever.\
Construction was started immediately under the terms of the law. Within\
seventeen years about 1,600,000 acres had been reclaimed and more than a\
million were actually irrigated. In the single year 1918, the crops of\
the irrigated districts were valued at approximately $100,000,000.\
\
In his first message, also, President Roosevelt urged the transfer of\
all control over national forests to trained men in the Bureau of\
Forestry--a recommendation carried out in 1907 when the Forestry Service\
was created. In every direction noteworthy advances were made in the\
administration of the national domain. The science of forestry was\
improved and knowledge of the subject spread among the people. Lands in\
the national forest available for agriculture were opened to settlers.\
Water power sites on the public domain were leased for a term of years\
to private companies instead of being sold outright. The area of the\
national forests was enlarged from 43 million acres to 194 million acres\
by presidential proclamation--more than 43 million acres being added in\
one year, 1907. The men who turned sheep and cattle to graze on the\
public lands were compelled to pay a fair rental, much to their\
dissatisfaction. Fire prevention work was undertaken in the forests on a\
large scale, reducing the appalling, annual destruction of timber.\
Millions of acres of coal land, such as the government had been\
carelessly selling to mining companies at low figures, were withdrawn\
from sale and held until Congress was prepared to enact laws for the\
disposition of them in the public interest. Prosecutions were\
instituted against men who had obtained public lands by fraud and vast\
tracts were recovered for the national domain. An agitation was begun\
which bore fruit under the administrations of Taft and Wilson in laws\
reserving to the federal government the ownership of coal, water power,\
phosphates, and other natural resources while authorizing corporations\
to develop them under leases for a period of years.\
\
=The Prosecution of the Trusts.=--As an executive, President Roosevelt\
was also a distinct "personality." His discrimination between "good" and\
"bad" trusts led him to prosecute some of them with vigor. On his\
initiative, the Northern Securities Company, formed to obtain control of\
certain great western railways, was dissolved by order of the Supreme\
Court. Proceedings were instituted against the American Tobacco Company\
and the Standard Oil Company as monopolies in violation of the Sherman\
Anti-Trust law. The Sugar Trust was found guilty of cheating the New\
York customs house and some of the minor officers were sent to prison.\
Frauds in the Post-office Department were uncovered and the offenders\
brought to book. In fact hardly a week passed without stirring news of\
"wrong doers" and "malefactors" haled into federal courts.\
\
=The Great Coal Strike.=--The Roosevelt theory that the President could\
do anything for public welfare not forbidden by the Constitution and the\
laws was put to a severe test in 1902. A strike of the anthracite coal\
miners, which started in the summer, ran late into the autumn.\
Industries were paralyzed for the want of coal; cities were threatened\
with the appalling menace of a winter without heat. Governors and mayors\
were powerless and appealed for aid. The mine owners rejected the\
demands of the men and refused to permit the arbitration of the points\
in dispute, although John Mitchell, the leader of the miners, repeatedly\
urged it. After observing closely the course affairs, President\
Roosevelt made up his mind that the situation was intolerable. He\
arranged to have the federal troops, if necessary, take possession of\
the mines and operate them until the strike could be settled. He then\
invited the contestants to the White House and by dint of hard labor\
induced them to accept, as a substitute or compromise, arbitration by a\
commission which he appointed. Thus, by stepping outside the\
Constitution and acting as the first citizen of the land, President\
Roosevelt averted a crisis of great magnitude.\
\
=The Election of 1904.=--The views and measures which he advocated with\
such vigor aroused deep hostility within as well as without his party.\
There were rumors of a Republican movement to defeat his nomination in\
1904 and it was said that the "financial and corporation interests" were\
in arms against him. A prominent Republican paper in New York City\
accused him of having "stolen Mr. Bryan's thunder," by harrying the\
trusts and favoring labor unions. When the Republican convention\
assembled in Chicago, however, the opposition disappeared and Roosevelt\
was nominated by acclamation.\
\
This was the signal for a change on the part of Democratic leaders. They\
denounced the President as erratic, dangerous, and radical and decided\
to assume the moderate role themselves. They put aside Mr. Bryan and\
selected as their candidate, Judge Alton B. Parker, of New York, a man\
\
who repudiated free silver and made a direct appeal for the conservative\
vote. The outcome of the reversal was astounding. Judge Parker's vote\
fell more than a million below that cast for Bryan in 1900; of the 476\
electoral votes he received only 140. Roosevelt, in addition to sweeping\
the Republican sections, even invaded Democratic territory, carrying the\
state of Missouri. Thus vindicated at the polls, he became more\
outspoken than ever. His leadership in the party was so widely\
recognized that he virtually selected his own successor.\
\
\
THE ADMINISTRATION OF PRESIDENT TAFT\
\
=The Campaign of 1908.=--Long before the end of his elective term,\
President Roosevelt let it be known that he favored as his successor,\
William Howard Taft, of Ohio, his Secretary of War. To attain this end\
he used every shred of his powerful influence. When the Republican\
convention assembled, Mr. Taft easily won the nomination. Though the\
party platform was conservative in tone, he gave it a progressive tinge\
by expressing his personal belief in the popular election of United\
States Senators, an income tax, and other liberal measures. President\
Roosevelt announced his faith in the Republican candidate and appealed\
to the country for his election.\
\
The turn in Republican affairs now convinced Mr. Bryan that the signs\
were propitious for a third attempt to win the presidency. The disaster\
to Judge Parker had taught the party that victory did not lie in a\
conservative policy. With little difficulty, therefore, the veteran\
leader from Nebraska once more rallied the Democrats around his\
standard, won the nomination, and wrote a platform vigorously attacking\
the tariff, trusts, and monopolies. Supported by a loyal following, he\
entered the lists, only to meet another defeat. Though he polled almost\
a million and a half more votes than did Judge Parker in 1904, the palm\
went to Mr. Taft.\
\
=The Tariff Revision and Party Dissensions.=--At the very beginning of\
his term, President Taft had to face the tariff issue. He had met it in\
the campaign. Moved by the Democratic demand for a drastic reduction, he\
had expressed opinions which were thought to imply a "downward\
revision." The Democrats made much of the implication and the\
Republicans from the Middle West rejoiced in it. Pressure was coming\
from all sides. More than ten years had elapsed since the enactment of\
the Dingley bill and the position of many industries had been altered\
with the course of time. Evidently the day for revision--at best a\
thankless task--had arrived. Taft accepted the inevitable and called\
Congress in a special session. Until the midsummer of 1909, Republican\
Senators and Representatives wrangled over tariff schedules, the\
President making little effort to influence their decisions. When on\
August 5 the Payne-Aldrich bill became a law, a breach had been made in\
Republican ranks. Powerful Senators from the Middle West had spoken\
angrily against many of the high rates imposed by the bill. They had\
even broken with their party colleagues to vote against the entire\
scheme of tariff revision.\
\
=The Income Tax Amendment.=--The rift in party harmony was widened by\
another serious difference of opinion. During the debate on the tariff\
bill, there was a concerted movement to include in it an income tax\
provision--this in spite of the decision of the Supreme Court in 1895\
declaring it unconstitutional. Conservative men were alarmed by the\
evident willingness of some members to flout a solemn decree of that\
eminent tribunal. At the same time they saw a powerful combination of\
Republicans and Democrats determined upon shifting some of the burden of\
taxation to large incomes. In the press of circumstances, a compromise\
was reached. The income tax bill was dropped for the present; but\
Congress passed the sixteenth amendment to the Constitution, authorizing\
taxes upon incomes from whatever source they might be derived, without\
reference to any apportionment among the states on the basis of\
population. The states ratified the amendment and early in 1913 it was\
proclaimed.\
\
=President Taft's Policies.=--After the enactment of the tariff bill,\
Taft continued to push forward with his legislative program. He\
recommended, and Congress created, a special court of commerce with\
jurisdiction, among other things, over appeals from the interstate\
commerce commission, thus facilitating judicial review of the railway\
rates fixed and the orders issued by that body. This measure was quickly\
followed by an act establishing a system of postal savings banks in\
connection with the post office--a scheme which had long been opposed by\
private banks. Two years later, Congress defied the lobby of the express\
companies and supplemented the savings banks with a parcels post system,\
thus enabling the American postal service to catch up with that of other\
progressive nations. With a view to improving the business\
administration of the federal government, the President obtained from\
Congress a large appropriation for an economy and efficiency commission\
charged with the duty of inquiring into wasteful and obsolete methods\
and recommending improved devices and practices. The chief result of\
this investigation was a vigorous report in favor of a national budget\
system, which soon found public backing.\
\
President Taft negotiated with England and France general treaties\
providing for the arbitration of disputes which were "justiciable" in\
character even though they might involve questions of "vital interest\
and national honor." They were coldly received in the Senate and so\
amended that Taft abandoned them altogether. A tariff reciprocity\
agreement with Canada, however, he forced through Congress in the face\
of strong opposition from his own party. After making a serious breach\
in Republican ranks, he was chagrined to see the whole scheme come to\
naught by the overthrow of the Liberals in the Canadian elections of\
1911.\
\
=Prosecution of the Trusts.=--The party schism was even enlarged by what\
appeared to be the successful prosecution of several great combinations.\
In two important cases, the Supreme Court ordered the dissolution of the\
Standard Oil Company and the American Tobacco Company on the ground that\
they violated the Sherman Anti-Trust law. In taking this step Chief\
Justice White was at some pains to state that the law did not apply to\
combinations which did not "unduly" restrain trade. His remark,\
construed to mean that the Court would not interfere with corporations\
as such, became the subject of a popular outcry against the President\
and the judges.\
\
\
PROGRESSIVE INSURGENCY AND THE ELECTION OF 1912\
\
=Growing Dissensions.=--All in all, Taft's administration from the first\
day had been disturbed by party discord. High words had passed over the\
tariff bill and disgruntled members of Congress could not forget them.\
To differences over issues were added quarrels between youth and old\
age. In the House of Representatives there developed a group of young\
"insurgent" Republicans who resented the dominance of the Speaker,\
Joseph G. Cannon, and other members of the "old guard," as they named\
the men of long service and conservative minds. In 1910, the insurgents\
went so far as to join with the Democrats in a movement to break the\
Speaker's sway by ousting him from the rules committee and depriving him\
of the power to appoint its members. The storm was brewing. In the\
autumn of that year the Democrats won a clear majority in the House of\
Representatives and began an open battle with President Taft by\
demanding an immediate downward revision of the tariff.\
\
=The Rise of the Progressive Republicans.=--Preparatory to the campaign\
of 1912, the dissenters within the Republican party added the prefix\
"Progressive" to their old title and began to organize a movement to\
prevent the renomination of Mr. Taft. As early as January 21, 1911, they\
formed a Progressive Republican League at the home of Senator La\
Follette of Wisconsin and launched an attack on the Taft measures and\
policies. In October they indorsed Mr. La Follette as "the logical\
Republican candidate" and appealed to the party for support. The\
controversy over the tariff had grown into a formidable revolt against\
the occupant of the White House.\
\
=Roosevelt in the Field.=--After looking on for a while, ex-President\
Roosevelt took a hand in the fray. Soon after his return in 1910 from a\
hunting trip in Africa and a tour in Europe, he made a series of\
addresses in which he formulated a progressive program. In a speech in\
Kansas, he favored regulation of the trusts, a graduated income tax\
bearing heavily on great fortunes, tariff revision schedule by schedule,\
conservation of natural resources, labor legislation, the direct\
primary, and the recall of elective officials. In an address before the\
Ohio state constitutional convention in February, 1912, he indorsed the\
initiative and referendum and announced a doctrine known as the "recall\
of judicial decisions." This was a new and radical note in American\
politics. An ex-President of the United States proposed that the people\
at the polls should have the right to reverse the decision of a judge\
who set aside any act of a state legislature passed in the interests of\
social welfare. The Progressive Republicans, impressed by these\
addresses, turned from La Follette to Roosevelt and on February 24,\
induced him to come out openly as a candidate against Taft for the\
Republican nomination.\
\
=The Split in the Republican Party.=--The country then witnessed the\
strange spectacle of two men who had once been close companions engaged\
in a bitter rivalry to secure a majority of the delegates to the\
Republican convention to be held at Chicago. When the convention\
assembled, about one-fourth of the seats were contested, the delegates\
for both candidates loudly proclaiming the regularity of their election.\
In deciding between the contestants the national committee, after the\
usual hearings, settled the disputes in such a way that Taft received a\
safe majority. After a week of negotiation, Roosevelt and his followers\
left the Republican party. Most of his supporters withdrew from the\
convention and the few who remained behind refused to answer the roll\
call. Undisturbed by this formidable bolt, the regular Republicans went\
on with their work. They renominated Mr. Taft and put forth a platform\
roundly condemning such Progressive doctrines as the recall of judges.\
\
=The Formation of the Progressive Party.=--The action of the Republicans\
in seating the Taft delegates was vigorously denounced by Roosevelt. He\
declared that the convention had no claim to represent the voters of the\
Republican party; that any candidate named by it would be "the\
beneficiary of a successful fraud"; and that it would be deeply\
discreditable to any man to accept the convention's approval under such\
circumstances. The bitterness of his followers was extreme. On July 8, a\
call went forth for a "Progressive" convention to be held in Chicago on\
August 5. The assembly which duly met on that day was a unique political\
conference. Prominence was given to women delegates, and "politicians"\
were notably absent. Roosevelt himself, who was cheered as a conquering\
hero, made an impassioned speech setting forth his "confession of\
faith." He was nominated by acclamation; Governor Hiram Johnson of\
California was selected as his companion candidate for Vice President.\
The platform endorsed such political reforms as woman suffrage, direct\
primaries, the initiative, referendum, and recall, popular election of\
United States Senators, and the short ballot. It favored a program of\
social legislation, including the prohibition of child labor and minimum\
wages for women. It approved the regulation, rather than the\
dissolution, of the trusts. Like apostles in a new and lofty cause, the\
Progressives entered a vigorous campaign for the election of their\
distinguished leader.\
\
=Woodrow Wilson and the Election of 1912.=--With the Republicans\
divided, victory loomed up before the Democrats. Naturally, a terrific\
contest over the nomination occurred at their convention in Baltimore.\
Champ Clark, Speaker of the House of Representatives, and Governor\
Woodrow Wilson, of New Jersey, were the chief contestants. After tossing\
to and fro for seven long, hot days, and taking forty-six ballots, the\
delegates, powerfully influenced by Mr. Bryan, finally decided in favor\
of the governor. As a professor, a writer on historical and political\
subjects, and the president of Princeton University, Mr. Wilson had\
become widely known in public life. As the governor of New Jersey he had\
attracted the support of the progressives in both parties. With grim\
determination he had "waged war on the bosses," and pushed through the\
legislature measures establishing direct primaries, regulating public\
utilities, and creating a system of workmen's compensation in\
industries. During the presidential campaign that followed Governor\
Wilson toured the country and aroused great enthusiasm by a series of\
addresses later published under the title of _The New Freedom_. He\
declared that "the government of the United States is at present the\
foster child of the special interests." He proposed to free the country\
by breaking the dominance of "the big bankers, the big manufacturers,\
the big masters of commerce, the heads of railroad corporations and of\
steamship corporations."\
\
In the election Governor Wilson easily secured a majority of the\
electoral votes, and his party, while retaining possession of the House\
of Representatives, captured the Senate as well. The popular verdict,\
however, indicated a state of confusion in the country. The combined\
Progressive and Republican vote exceeded that of the Democrats by\
1,300,000. The Socialists, with Eugene V. Debs as their candidate again,\
polled about 900,000 votes, more than double the number received four\
years before. Thus, as the result of an extraordinary upheaval the\
Republicans, after holding the office of President for sixteen years,\
passed out of power, and the government of the country was intrusted to\
the Democrats under the leadership of a man destined to be one of the\
outstanding figures of the modern age, Woodrow Wilson.\
\
\
=General References=\
\
J.B. Bishop, _Theodore Roosevelt and His Time_ (2 vols.).\
\
Theodore Roosevelt, _Autobiography_; _New Nationalism_; _Progressive\
Principles_.\
\
W.H. Taft, _Popular Government_.\
\
Walter Weyl, _The New Democracy_.\
\
H. Croly, _The Promise of American Life_.\
\
J.B. Bishop, _The Panama Gateway_.\
\
J.B. Scott, _The Hague Peace Conferences_.\
\
W.B. Munro (ed.), _Initiative, Referendum, and Recall_.\
\
C.R. Van Hise, _The Conservation of Natural Resources_.\
\
Gifford Pinchot, _The Fight for Conservation_.\
\
W.F. Willoughby, _Territories and Dependencies of the United States_\
(1905).\
\
\
=Research Topics=\
\
=Roosevelt and "Big Business."=--Haworth, _The United States in Our Own\
Time_, pp. 281-289; F.A. Ogg, _National Progress_ (American Nation\
Series), pp. 40-75; Paxson, _The New Nation_ (Riverside Series), pp.\
293-307.\
\
=Our Insular Possessions.=--Elson, _History of the United States_, pp.\
896-904.\
\
=Latin-American Relations.=--Haworth, pp. 294-299; Ogg, pp. 254-257.\
\
=The Panama Canal.=--Haworth, pp. 300-309; Ogg, pp. 266-277; Paxson, pp.\
286-292; Elson, pp. 906-911.\
\
=Conservation.=--Haworth, pp. 331-334; Ogg, pp. 96-115; Beard, _American\
Government and Politics_ (3d ed.), pp. 401-416.\
\
=Republican Dissensions under Taft's Administration.=--Haworth, pp.\
351-360; Ogg, pp. 167-186; Paxson, pp. 324-342; Elson, pp. 916-924.\
\
=The Campaign of 1912.=--Haworth, pp. 360-379; Ogg, pp. 187-208.\
\
\
=Questions=\
\
1. Compare the early career of Roosevelt with that of some other\
President.\
\
2. Name the chief foreign and domestic questions of the Roosevelt-Taft\
administrations.\
\
3. What international complications were involved in the Panama Canal\
problem?\
\
4. Review the Monroe Doctrine. Discuss Roosevelt's applications of it.\
\
5. What is the strategic importance of the Caribbean to the United\
States?\
\
6. What is meant by the sea power? Trace the voyage of the fleet around\
the world and mention the significant imperial and commercial points\
touched.\
\
7. What is meant by the question: "Does the Constitution follow the\
flag?"\
\
8. Trace the history of self-government in Porto Rico. In the\
Philippines.\
\
9. What is Cuba's relation to the United States?\
\
10. What was Roosevelt's theory of our Constitution?\
\
11. Give Roosevelt's views on trusts, labor, taxation.\
\
12. Outline the domestic phases of Roosevelt's administrations.\
\
13. Account for the dissensions under Taft.\
\
14. Trace the rise of the Progressive movement.\
\
15. What was Roosevelt's progressive program?\
\
16. Review Wilson's early career and explain the underlying theory of\
_The New Freedom_.\
\
\
\
\
CHAPTER XXII\
\
THE SPIRIT OF REFORM IN AMERICA\
\
\
AN AGE OF CRITICISM\
\
=Attacks on Abuses in American Life.=--The crisis precipitated by the\
Progressive uprising was not a sudden and unexpected one. It had been\
long in preparation. The revolt against corruption in politics which\
produced the Liberal Republican outbreak in the seventies and the\
Mugwump movement of the eighties was followed by continuous criticism of\
American political and economic development. From 1880 until his death\
in 1892, George William Curtis, as president of the Civil Service Reform\
Association, kept up a running fire upon the abuses of the spoils\
system. James Bryce, an observant English scholar and man of affairs, in\
his great work, _The American Commonwealth_, published in 1888, by\
picturing fearlessly the political rings and machines which dominated\
the cities, gave the whole country a fresh shock. Six years later Henry\
D. Lloyd, in a powerful book entitled _Wealth against Commonwealth_,\
attacked in scathing language certain trusts which had destroyed their\
rivals and bribed public officials. In 1903 Miss Ida Tarbell, an author\
of established reputation in the historical field, gave to the public an\
account of the Standard Oil Company, revealing the ruthless methods of\
that corporation in crushing competition. About the same time Lincoln\
Steffens exposed the sordid character of politics in several\
municipalities in a series of articles bearing the painful heading: _The\
Shame of the Cities_. The critical spirit appeared in almost every form;\
in weekly and monthly magazines, in essays and pamphlets, in editorials\
and news stories, in novels like Churchill's _Coniston_ and Sinclair's\
_The Jungle_. It became so savage and so wanton that the opening years\
of the twentieth century were well named "the age of the muckrakers."\
\
=The Subjects of the Criticism.=--In this outburst of invective, nothing\
was spared. It was charged that each of the political parties had fallen\
into the hands of professional politicians who devoted their time to\
managing conventions, making platforms, nominating candidates, and\
dictating to officials; in return for their "services" they sold offices\
and privileges. It was alleged that mayors and councils had bargained\
away for private benefit street railway and other franchises. It was\
asserted that many powerful labor unions were dominated by men who\
blackmailed employers. Some critics specialized in descriptions of the\
poverty, slums, and misery of great cities. Others took up "frenzied\
finance" and accused financiers of selling worthless stocks and bonds to\
an innocent public. Still others professed to see in the accumulations\
of millionaires the downfall of our republic.\
\
=The Attack on "Invisible Government."=--Some even maintained that the\
control of public affairs had passed from the people to a sinister\
minority called "the invisible government." So eminent and conservative\
a statesman as the Hon. Elihu Root lent the weight of his great name to\
such an imputation. Speaking of his native state, New York, he said:\
"What is the government of this state? What has it been during the forty\
years of my acquaintance with it? The government of the Constitution?\
Oh, no; not half the time or half way.... From the days of Fenton and\
Conkling and Arthur and Cornell and Platt, from the days of David B.\
Hill down to the present time, the government of the state has presented\
two different lines of activity: one, of the constitutional and\
statutory officers of the state and the other of the party leaders; they\
call them party bosses. They call the system--I don't coin the\
phrase--the system they call 'invisible government.' For I don't know\
how many years Mr. Conkling was the supreme ruler in this state. The\
governor did not count, the legislature did not count, comptrollers and\
secretaries of state and what not did not count. It was what Mr.\
Conkling said, and in a great outburst of public rage he was pulled\
down. Then Mr. Platt ruled the state; for nigh upon twenty years he\
ruled it. It was not the governor; it was not the legislature; it was\
Mr. Platt. And the capital was not here [in Albany]; it was at 49\
Broadway; Mr. Platt and his lieutenants. It makes no difference what\
name you give, whether you call it Fenton or Conkling or Cornell or\
Arthur or Platt or by the names of men now living. The ruler of the\
state during the greater part of the forty years of my acquaintance with\
the state government has not been any man authorized by the constitution\
or by law.... The party leader is elected by no one, accountable to no\
one, bound by no oath of office, removable by no one."\
\
=The Nation Aroused.=--With the spirit of criticism came also the spirit\
of reform. The charges were usually exaggerated; often wholly false; but\
there was enough truth in them to warrant renewed vigilance on the part\
of American democracy. President Roosevelt doubtless summed up the\
sentiment of the great majority of citizens when he demanded the\
punishment of wrong-doers in 1907, saying: "It makes not a particle of\
difference whether these crimes are committed by a capitalist or by a\
laborer, by a leading banker or manufacturer or railroad man or by a\
leading representative of a labor union. Swindling in stocks, corrupting\
legislatures, making fortunes by the inflation of securities, by\
wrecking railroads, by destroying competitors through rebates--these\
forms of wrong-doing in the capitalist are far more infamous than any\
ordinary form of embezzlement or forgery." The time had come, he added,\
to stop "muckraking" and proceed to the constructive work of removing\
the abuses that had grown up.\
\
\
POLITICAL REFORMS\
\
=The Public Service.=--It was a wise comprehension of the needs of\
American democracy that led the friends of reform to launch and to\
sustain for more than half a century a movement to improve the public\
service. On the one side they struck at the spoils system; at the right\
of the politicians to use public offices as mere rewards for partisan\
work. The federal civil service act of 1883 opened the way to reform by\
establishing five vital principles in law: (1) admission to office, not\
on the recommendation of party workers, but on the basis of competitive\
examinations; (2) promotion for meritorious service of the government\
rather than of parties; (3) no assessment of office holders for campaign\
funds; (4) permanent tenure during good behavior; and (5) no dismissals\
for political reasons. The act itself at first applied to only 14,000\
federal offices, but under the constant pressure from the reformers it\
was extended until in 1916 it covered nearly 300,000 employees out of an\
executive force of approximately 414,000. While gaining steadily at\
Washington, civil service reformers carried their agitation into the\
states and cities. By 1920 they were able to report ten states with\
civil service commissions and the merit system well intrenched in more\
than three hundred municipalities.\
\
In excluding spoilsmen from public office, the reformers were, in a\
sense, engaged in a negative work: that of "keeping the rascals out."\
But there was a second and larger phase to their movement, one\
constructive in character: that of getting skilled, loyal, and efficient\
servants into the places of responsibility. Everywhere on land and sea,\
in town and country, new burdens were laid upon public officers. They\
were called upon to supervise the ships sailing to and from our ports;\
to inspect the water and milk supplies of our cities; to construct and\
operate great public works, such as the Panama and Erie canals; to\
regulate the complicated rates of railway companies; to safeguard health\
and safety in a thousand ways; to climb the mountains to fight forest\
fires; and to descend into the deeps of the earth to combat the deadly\
coal gases that assail the miners. In a word, those who labored to\
master the secrets and the powers of nature were summoned to the aid of\
the government: chemists, engineers, architects, nurses, surgeons,\
foresters--the skilled in all the sciences, arts, and crafts.\
\
Keeping rascals out was no task at all compared with the problem of\
finding competent people for all the technical offices. "Now," said the\
reformers, "we must make attractive careers in the government work for\
the best American talent; we must train those applying for admission and\
increase the skill of those already in positions of trust; we must see\
to it that those entering at the bottom have a chance to rise to the\
top; in short, we must work for a government as skilled and efficient as\
it is strong, one commanding all the wisdom and talent of America that\
public welfare requires."\
\
=The Australian Ballot.=--A second line of attack on the political\
machines was made in connection with the ballot. In the early days\
elections were frequently held in the open air and the poll was taken by\
a show of hands or by the enrollment of the voters under names of their\
favorite candidates. When this ancient practice was abandoned in favor\
of the printed ballot, there was still no secrecy about elections. Each\
party prepared its own ballot, often of a distinctive color, containing\
the names of its candidates. On election day, these papers were handed\
out to the voters by party workers. Any one could tell from the color of\
the ballot dropped into the box, or from some mark on the outside of the\
folded ballot, just how each man voted. Those who bought votes were sure\
that their purchases were "delivered." Those who intimidated voters\
could know when their intimidation was effective. In this way the party\
ballot strengthened the party machine.\
\
As a remedy for such abuses, reformers, learning from the experience of\
Australia, urged the adoption of the "Australian ballot." That ballot,\
though it appeared in many forms, had certain constant features. It was\
official, that is, furnished by the government, not by party workers; it\
contained the names of all candidates of all parties; it was given out\
only in the polling places; and it was marked in secret. The first state\
to introduce it was Massachusetts. The year was 1888. Before the end of\
the century it had been adopted by nearly all the states in the union.\
The salutary effect of the reform in reducing the amount of cheating\
and bribery in elections was beyond all question.\
\
=The Direct Primary.=--In connection with the uprising against machine\
politics, came a call for the abolition of the old method of nominating\
candidates by conventions. These time-honored party assemblies, which\
had come down from the days of Andrew Jackson, were, it was said, merely\
conclaves of party workers, sustained by the spoils system, and\
dominated by an inner circle of bosses. The remedy offered in this case\
was again "more democracy," namely, the abolition of the party\
convention and the adoption of the direct primary. Candidates were no\
longer to be chosen by secret conferences. Any member of a party was to\
be allowed to run for any office, to present his name to his party by\
securing signatures to a petition, and to submit his candidacy to his\
fellow partisans at a direct primary--an election within the party. In\
this movement Governor La Follette of Wisconsin took the lead and his\
state was the first in the union to adopt the direct primary for\
state-wide purposes. The idea spread, rapidly in the West, more slowly\
in the East. The public, already angered against "the bosses," grasped\
eagerly at it. Governor Hughes in New York pressed it upon the unwilling\
legislature. State after state accepted it until by 1918 Rhode Island,\
Delaware, Connecticut, and New Mexico were the only states that had not\
bowed to the storm. Still the results were disappointing and at that\
very time the pendulum was beginning to swing backward.\
\
=Popular Election of Federal Senators.=--While the movement for direct\
primaries was still advancing everywhere, a demand for the popular\
election of Senators, usually associated with it, swept forward to\
victory. Under the original Constitution, it had been expressly provided\
that Senators should be chosen by the legislatures of the states. In\
practice this rule transferred the selection of Senators to secret\
caucuses of party members in the state legislatures. In connection with\
these caucuses there had been many scandals, some direct proofs of\
brazen bribery and corruption, and dark hints besides. The Senate was\
called by its detractors "a millionaires' club" and it was looked upon\
as the "citadel of conservatism." The prescription in this case was\
likewise "more democracy"--direct election of Senators by popular vote.\
\
This reform was not a new idea. It had been proposed in Congress as\
early as 1826. President Johnson, an ardent advocate, made it the\
subject of a special message in 1868 Not long afterward it appeared in\
Congress. At last in 1893, the year after the great Populist upheaval,\
the House of Representatives by the requisite two-thirds vote\
incorporated it in an amendment to the federal Constitution. Again and\
again it passed the House; but the Senate itself was obdurate. Able\
Senators leveled their batteries against it. Mr. Hoar of Massachusetts\
declared that it would transfer the seat of power to the "great cities\
and masses of population"; that it would "overthrow the whole scheme of\
the Senate and in the end the whole scheme of the national Constitution\
as designed and established by the framers of the Constitution and the\
people who adopted it."\
\
Failing in the Senate, advocates of popular election made a rear assault\
through the states. They induced state legislatures to enact laws\
requiring the nomination of candidates for the Senate by the direct\
primary, and then they bound the legislatures to abide by the popular\
choice. Nevada took the lead in 1899. Shortly afterward Oregon, by the\
use of the initiative and referendum, practically bound legislators to\
accept the popular nominee and the country witnessed the spectacle of a\
Republican legislature "electing" a Democrat to represent the state in\
the Senate at Washington. By 1910 three-fourths of the states had\
applied the direct primary in some form to the choice of Senators. Men\
selected by that method began to pour in upon the floors of Congress;\
finally in 1912 the two-thirds majority was secured for an amendment to\
the federal Constitution providing for the popular election of Senators.\
It was quickly ratified by the states. The following year it was\
proclaimed in effect.\
\
=The Initiative and Referendum.=--As a corrective for the evils which\
had grown up in state legislatures there arose a demand for the\
introduction of a Swiss device known as the initiative and referendum.\
The initiative permits any one to draw up a proposed bill; and, on\
securing a certain number of signatures among the voters, to require the\
submission of the measure to the people at an election. If the bill thus\
initiated receives a sufficient majority, it becomes a law. The\
referendum allows citizens who disapprove any act passed by the\
legislature to get up a petition against it and thus bring about a\
reference of the measure to the voters at the polls for approval or\
rejection. These two practices constitute a form of "direct government."\
\
These devices were prescribed "to restore the government to the people."\
The Populists favored them in their platform of 1896. Mr. Bryan, two\
years later, made them a part of his program, and in the same year South\
Dakota adopted them. In 1902 Oregon, after a strenuous campaign, added a\
direct legislation amendment to the state constitution. Within ten years\
all the Southwestern, Mountain, and Pacific states, except Texas and\
Wyoming, had followed this example. To the east of the Mississippi,\
however, direct legislation met a chilly reception. By 1920 only five\
states in this section had accepted it: Maine, Massachusetts, Ohio,\
Michigan, and Maryland, the last approving the referendum only.\
\
=The Recall.=--Executive officers and judges, as well as legislatures,\
had come in for their share of criticism, and it was proposed that they\
should likewise be subjected to a closer scrutiny by the public. For\
this purpose there was advanced a scheme known as the recall--which\
permitted a certain percentage of the voters to compel any officer, at\
any time during his term, to go before the people at a new election.\
This feature of direct government, tried out first in the city of Los\
Angeles, was extended to state-wide uses in Oregon in 1908. It failed,\
however, to capture popular imagination to the same degree as the\
initiative and referendum. At the end of ten years' agitation, only ten\
states, mainly in the West, had adopted it for general purposes, and\
four of them did not apply it to the judges of the courts. Still it was\
extensively acclaimed in cities and incorporated into hundreds of\
municipal laws and charters.\
\
As a general proposition, direct government in all its forms was\
bitterly opposed by men of a conservative cast of mind. It was denounced\
by Senator Henry Cabot Lodge as "nothing less than a complete revolution\
in the fabric of our government and in the fundamental principles upon\
which that government rests." In his opinion, it promised to break down\
the representative principle and "undermine and overthrow the bulwarks\
of ordered liberty and individual freedom." Mr. Taft shared Mr. Lodge's\
views and spoke of direct government with scorn. "Votes," he exclaimed,\
"are not bread ... referendums do not pay rent or furnish houses,\
recalls do not furnish clothes, initiatives do not supply employment or\
relieve inequalities of condition or of opportunity."\
\
=Commission Government for Cities.=--In the restless searching out of\
evils, the management of cities early came under critical scrutiny. City\
government, Mr. Bryce had remarked, was the one conspicuous failure in\
America. This sharp thrust, though resented by some, was accepted as a\
warning by others. Many prescriptions were offered by doctors of the\
body politic. Chief among them was the idea of simplifying the city\
government so that the light of public scrutiny could shine through it.\
"Let us elect only a few men and make them clearly responsible for the\
city government!" was the new cry in municipal reform. So, many city\
councils were reduced in size; one of the two houses, which several\
cities had adopted in imitation of the federal government, was\
abolished; and in order that the mayor could be held to account, he was\
given the power to appoint all the chief officials. This made the mayor,\
in some cases, the only elective city official and gave the voters a\
"short ballot" containing only a few names--an idea which some proposed\
to apply also to the state government.\
\
A further step in the concentration of authority was taken in Galveston,\
Texas, where the people, looking upon the ruin of their city wrought by\
the devastating storm of 1901, and confronted by the difficult problems\
of reconstruction, felt the necessity for a more businesslike management\
of city affairs and instituted a new form of local administration. They\
abolished the old scheme of mayor and council and vested all power in\
five commissioners, one of whom, without any special prerogatives, was\
assigned to the office of "mayor president." In 1908, the commission\
form of government, as it was soon characterized, was adopted by Des\
Moines, Iowa. The attention of all municipal reformers was drawn to it\
and it was hailed as the guarantee of a better day. By 1920, more than\
four hundred cities, including Memphis, Spokane, Birmingham, Newark, and\
Buffalo, had adopted it. Still the larger cities like New York and\
Chicago kept their boards of aldermen.\
\
=The City Manager Plan.=--A few years' experience with commission\
government revealed certain patent defects. The division of the work\
among five men was frequently found to introduce dissensions and\
irresponsibility. Commissioners were often lacking in the technical\
ability required to manage such difficult matters as fire and police\
protection, public health, public works, and public utilities. Some one\
then proposed to carry over into city government an idea from the\
business world. In that sphere the stockholders of each corporation\
elect the directors and the directors, in turn, choose a business\
manager to conduct the affairs of the company. It was suggested that the\
city commissioners, instead of attempting to supervise the details of\
the city administration, should select a manager to do this. The scheme\
was put into effect in Sumter, South Carolina, in 1912. Like the\
commission plan, it became popular. Within eight years more than one\
hundred and fifty towns and cities had adopted it. Among the larger\
municipalities were Dayton, Springfield (Ohio), Akron, Kalamazoo, and\
Phoenix. It promised to create a new public service profession, that of\
city manager.\
\
\
MEASURES OF ECONOMIC REFORM\
\
=The Spirit of American Reform.=--The purification of the ballot, the\
restriction of the spoils system, the enlargement of direct popular\
control over the organs of government were not the sole answers made by\
the reformers to the critics of American institutions. Nor were they the\
most important. In fact, they were regarded not as ends in themselves,\
but as means to serve a wider purpose. That purpose was the promotion of\
the "general welfare." The concrete objects covered by that broad term\
were many and varied; but they included the prevention of extortion by\
railway and other corporations, the protection of public health, the\
extension of education, the improvement of living conditions in the\
cities, the elimination of undeserved poverty, the removal of gross\
inequalities in wealth, and more equality of opportunity.\
\
All these things involved the use of the powers of government. Although\
a few clung to the ancient doctrine that the government should not\
interfere with private business at all, the American people at large\
rejected that theory as vigorously as they rejected the doctrines of an\
extreme socialism which exalts the state above the individual. Leaders\
representing every shade of opinion proclaimed the government an\
instrument of common welfare to be used in the public interest. "We must\
abandon definitely," said Roosevelt, "the _laissez-faire_ theory of\
political economy and fearlessly champion a system of increased\
governmental control, paying no attention to the cries of worthy people\
who denounce this as socialistic." This view was shared by Mr. Taft, who\
observed: "Undoubtedly the government can wisely do much more ... to\
relieve the oppressed, to create greater equality of opportunity, to\
make reasonable terms for labor in employment, and to furnish vocational\
education." He was quick to add his caution that "there is a line beyond\
which the government cannot go with any good practical results in\
seeking to make men and society better."\
\
=The Regulation of Railways.=--The first attempts to use the government\
in a large way to control private enterprise in the public interest were\
made by the Northwestern states in the decade between 1870 and 1880.\
Charges were advanced by the farmers, particularly those organized into\
Granges, that the railways extorted the highest possible rates for\
freight and passengers, that favoritism was shown to large shippers,\
that fraudulent stocks and bonds were sold to the innocent public. It\
was claimed that railways were not like other enterprises, but were\
"quasi-public" concerns, like the roads and ferries, and thus subject to\
government control. Accordingly laws were enacted bringing the railroads\
under state supervision. In some cases the state legislature fixed the\
maximum rates to be charged by common carriers, and in other cases\
commissions were created with the power to establish the rates after an\
investigation. This legislation was at first denounced in the East as\
nothing less than the "confiscation" of the railways in the interest of\
the farmers. Attempts to have the Supreme Court of the United States\
declare it unconstitutional were made without avail; still a principle\
was finally laid down to the effect that in fixing rates state\
legislatures and commissions must permit railway companies to earn a\
"fair" return on the capital invested.\
\
In a few years the Granger spirit appeared in Congress. An investigation\
revealed a long list of abuses committed by the railways against\
shippers and travelers. The result was the interstate commerce act of\
1887, which created the Interstate Commerce Commission, forbade\
discriminations in rates, and prohibited other objectionable practices\
on the part of railways. This measure was loosely enforced and the\
abuses against which it was directed continued almost unabated. A demand\
for stricter control grew louder and louder. Congress was forced to\
heed. In 1903 it enacted the Elkins law, forbidding railways to charge\
rates other than those published, and laid penalties upon the officers\
and agents of companies, who granted secret favors to shippers, and upon\
shippers who accepted them. Three years later a still more drastic step\
was taken by the passage of the Hepburn act. The Interstate Commerce\
Commission was authorized, upon complaint of some party aggrieved, and\
after a public hearing, to determine whether just and reasonable rates\
had been charged by the companies. In effect, the right to fix freight\
and passenger rates was taken out of the hands of the owners of the\
railways engaged in interstate commerce and vested in the hands of the\
Interstate Commerce Commission. Thus private property to the value of\
$20,000,000,000 or more was declared to be a matter of public concern\
and subject to government regulation in the common interest.\
\
=Municipal Utilities.=--Similar problems arose in connection with the\
street railways, electric light plants, and other utilities in the great\
cities. In the beginning the right to construct such undertakings was\
freely, and often corruptly, granted to private companies by city\
councils. Distressing abuses arose in connection with such practices.\
Many grants or franchises were made perpetual, or perhaps for a term of\
999 years. The rates charged and services rendered were left largely to\
the will of the companies holding the franchises. Mergers or unions of\
companies were common and the public was deluged with stocks and bonds\
of doubtful value; bankruptcies were frequent. The connection between\
the utility companies and the politicians was, to say the least, not\
always in the public interest.\
\
American ingenuity was quick to devise methods for eliminating such\
evils. Three lines of progress were laid out by the reformers. One group\
proposed that such utilities should be subject to municipal or state\
regulation, that the formation of utility companies should be under\
public control, and that the issue of stocks and bonds must be approved\
by public authority. In some cases state, and in other cases municipal,\
commissions were created to exercise this great power over "quasi-public\
corporations." Wisconsin, by laws enacted in 1907, put all heat, light,\
water works, telephone, and street railway companies under the\
supervision of a single railway commission. Other states followed this\
example rapidly. By 1920 the principle of public control over municipal\
utilities was accepted in nearly every section of the union.\
\
A second line of reform appeared in the "model franchise" for utility\
corporations. An illustration of this tendency was afforded by the\
Chicago street railway settlement of 1906. The total capital of the\
company was fixed at a definite sum, its earnings were agreed upon, and\
the city was given the right to buy and operate the system if it desired\
to do so. In many states, about the same time, it was provided that no\
franchises to utility companies could run more than twenty-five years.\
\
A third group of reformers were satisfied with nothing short of\
municipal ownership. They proposed to drive private companies entirely\
out of the field and vest the ownership and management of municipal\
plants in the city itself. This idea was extensively applied to electric\
light and water works plants, but to street railways in only a few\
cities, including San Francisco and Seattle. In New York the subways are\
owned by the city but leased for operation.\
\
=Tenement House Control.=--Among the other pressing problems of the\
cities was the overcrowding in houses unfit for habitation. An inquiry\
in New York City made under the authority of the state in 1902 revealed\
poverty, misery, slums, dirt, and disease almost beyond imagination. The\
immediate answer was the enactment of a tenement house law prescribing\
in great detail the size of the rooms, the air space, the light and the\
sanitary arrangement for all new buildings. An immense improvement\
followed and the idea was quickly taken up in other states having large\
industrial centers. In 1920 New York made a further invasion of the\
rights of landlords by assuring to the public "reasonable rents" for\
flats and apartments.\
\
=Workmen's Compensation.=--No small part of the poverty in cities was\
due to the injury of wage-earners while at their trade. Every year the\
number of men and women killed or wounded in industry mounted higher.\
Under the old law, the workman or his family had to bear the loss unless\
the employer had been guilty of some extraordinary negligence. Even in\
that case an expensive lawsuit was usually necessary to recover\
"damages." In short, although employers insured their buildings and\
machinery against necessary risks from fire and storm, they allowed\
their employees to assume the heavy losses due to accidents. The\
injustice of this, though apparent enough now, was once not generally\
recognized. It was said to be unfair to make the employer pay for\
injuries for which he was not personally responsible; but the argument\
was overborne.\
\
[Illustration: AN EAST SIDE STREET IN NEW YORK]\
\
About 1910 there set in a decided movement in the direction of lifting\
the burden of accidents from the unfortunate victims. In the first\
place, laws were enacted requiring employers to pay damages in certain\
amounts according to the nature of the case, no matter how the accident\
occurred, as long as the injured person was not guilty of willful\
negligence. By 1914 more than one-half the states had such laws. In the\
second place, there developed schemes of industrial insurance in the\
form of automatic grants made by state commissions to persons injured in\
industries, the funds to be provided by the employers or the state or by\
both. By 1917 thirty-six states had legislation of this type.\
\
=Minimum Wages and Mothers' Pensions.=--Another source of poverty,\
especially among women and children, was found to be the low wages paid\
for their labor. Report after report showed this. In 1912 Massachusetts\
took a significant step in the direction of declaring the minimum wages\
which might be paid to women and children. Oregon, the following year,\
created a commission with power to prescribe minimum wages in certain\
industries, based on the cost of living, and to enforce the rates fixed.\
Within a short time one-third of the states had legislation of this\
character. To cut away some of the evils of poverty and enable widows to\
keep their homes intact and bring up their children, a device known as\
mothers' pensions became popular during the second decade of the\
twentieth century. At the opening of 1913 two states, Colorado and\
Illinois, had laws authorizing the payment from public funds of definite\
sums to widows with children. Within four years, thirty-five states had\
similar legislation.\
\
=Taxation and Great Fortunes.=--As a part of the campaign waged against\
poverty by reformers there came a demand for heavy taxes upon great\
fortunes, particularly taxes upon inheritances or estates passing to\
heirs on the decease of the owners. Roosevelt was an ardent champion of\
this type of taxation and dwelt upon it at length in his message to\
Congress in 1907. "Such a tax," he said, "would help to preserve a\
measurable equality of opportunity for the people of the generations\
growing to manhood.... Our aim is to recognize what Lincoln pointed out:\
the fact that there are some respects in which men are obviously not\
equal; but also to insist that there should be equality of self-respect\
and of mutual respect, an equality of rights before the law, and at\
least an approximate equality in the conditions under which each man\
obtains the chance to show the stuff that is in him when compared with\
his fellows."\
\
The spirit of the new age was, therefore, one of reform, not of\
revolution. It called for no evolutionary or utopian experiments, but\
for the steady and progressive enactment of measures aimed at admitted\
abuses and designed to accomplish tangible results in the name of public\
welfare.\
\
\
=General References=\
\
J. Bryce, _The American Commonwealth_.\
\
R.C. Brooks, _Corruption in American Life_.\
\
E.A. Ross, _Changing America_.\
\
P.L. Haworth, _America in Ferment_.\
\
E.R.A. Seligman, _The Income Tax_.\
\
W.Z. Ripley, _Railroads: Rates and Regulation_.\
\
E.S. Bradford, _Commission Government in American Cities_.\
\
H.R. Seager, _A Program of Social Reform_.\
\
C. Zueblin, _American Municipal Progress_.\
\
W.E. Walling, _Progressivism and After_.\
\
_The American Year Book_ (an annual publication which contains reviews\
of reform legislation).\
\
\
=Research Topics=\
\
="The Muckrakers."=--Paxson, _The New Nation_ (Riverside Series), pp.\
309-323.\
\
=Civil Service Reform.=--Beard, _American Government and Politics_ (3d\
ed.), pp. 222-230; Ogg, _National Progress_ (American Nation Series),\
pp. 135-142.\
\
=Direct Government.=--Beard, _American Government_, pp. 461-473; Ogg,\
pp. 160-166.\
\
=Popular Election of Senators.=--Beard, _American Government_, pp.\
241-244; Ogg, pp. 149-150.\
\
=Party Methods.=--Beard, _American Government_, pp. 656-672.\
\
=Ballot Reform.=--Beard, _American Government_, pp. 672-705.\
\
=Social and Economic Legislation.=--Beard, _American Government_, pp.\
721-752.\
\
\
=Questions=\
\
1. Who were some of the critics of abuses in American life?\
\
2. What particular criticisms were advanced?\
\
3. How did Elihu Root define "invisible government"?\
\
4. Discuss the use of criticism as an aid to progress in a democracy.\
\
5. Explain what is meant by the "merit system" in the civil service.\
Review the rise of the spoils system.\
\
6. Why is the public service of increasing importance? Give some of its\
new problems.\
\
7. Describe the Australian ballot and the abuses against which it is\
directed.\
\
8. What are the elements of direct government? Sketch their progress in\
the United States.\
\
9. Trace the history of popular election of Senators.\
\
10. Explain the direct primary. Commission government. The city manager\
plan.\
\
11. How does modern reform involve government action? On what theory is\
it justified?\
\
12. Enumerate five lines of recent economic reform.\
\
\
\
\
CHAPTER XXIII\
\
THE NEW POLITICAL DEMOCRACY\
\
\
=Women in Public Affairs.=--The social legislation enacted in response\
to the spirit of reform vitally affected women in the home and in\
industry and was promoted by their organizations. Where they did not\
lead, they were affiliated with movements for social improvement. No\
cause escaped their attention; no year passed without widening the range\
of their interests. They served on committees that inquired into the\
problems of the day; they appeared before legislative assemblies to\
advocate remedies for the evils they discovered. By 1912 they were a\
force to be reckoned with in national politics. In nine states complete\
and equal suffrage had been established, and a widespread campaign for a\
national suffrage amendment was in full swing. On every hand lay\
evidences that their sphere had been broadened to include public\
affairs. This was the culmination of forces that had long been\
operating.\
\
=A New Emphasis in History.=--A movement so deeply affecting important\
interests could not fail to find a place in time in the written record\
of human progress. History often began as a chronicle of kings and\
queens, knights and ladies, written partly to amuse and partly to\
instruct the classes that appeared in its pages. With the growth of\
commerce, parliaments, and international relations, politics and\
diplomacy were added to such chronicles of royal and princely doings.\
After the rise of democracy, industry, and organized labor, the\
transactions of everyday life were deemed worthy of a place in the pages\
of history. In each case history was rewritten and the past rediscovered\
in the light of the new age. So it will be with the rise and growth of\
women's political power. The history of their labor, their education,\
their status in society, their influence on the course of events will be\
explored and given its place in the general record.\
\
It will be a history of change. The superior position which women enjoy\
in America to-day is the result of a slow evolution from an almost\
rightless condition in colonial times. The founders of America brought\
with them the English common law. Under that law, a married woman's\
personal property--jewels, money, furniture, and the like--became her\
husband's property; the management of her lands passed into his control.\
Even the wages she earned, if she worked for some one else, belonged to\
him. Custom, if not law, prescribed that women should not take part in\
town meetings or enter into public discussions of religious questions.\
Indeed it is a far cry from the banishment of Anne Hutchinson from\
Massachusetts in 1637, for daring to dispute with the church fathers, to\
the political conventions of 1920 in which women sat as delegates, made\
nominating speeches, and served on committees. In the contrast between\
these two scenes may be measured the change in the privileges of women\
since the landing of the Pilgrims. The account of this progress is a\
narrative of individual effort on the part of women, of organizations\
among them, of generous aid from sympathetic men in the long agitation\
for the removal of civil and political disabilities. It is in part also\
a narrative of irresistible economic change which drew women into\
industry, created a leisure class, gave women wages and incomes, and\
therewith economic independence.\
\
\
THE RISE OF THE WOMAN MOVEMENT\
\
=Protests of Colonial Women.=--The republican spirit which produced\
American independence was of slow and steady growth. It did not spring\
up full-armed in a single night. It was, on the contrary, nourished\
during a long period of time by fireside discussions as well as by\
debates in the public forum. Women shared that fireside sifting of\
political principles and passed on the findings of that scrutiny in\
letters to their friends, newspaper articles, and every form of written\
word. How widespread was this potent, though not spectacular force, is\
revealed in the collections of women's letters, articles, songs, dramas,\
and satirical "skits" on English rule that have come down to us. In this\
search into the reasons of government, some women began to take thought\
about laws that excluded them from the ballot. Two women at least left\
their protests on record. Abigail, the ingenious and witty wife of John\
Adams, wrote to her husband, in March, 1776, that women objected "to all\
arbitrary power whether of state or males" and demanded political\
privileges in the new order then being created. Hannah Lee Corbin, the\
sister of "Lighthorse" Harry Lee, protested to her brother against the\
taxation of women without representation.\
\
[Illustration: ABIGAIL ADAMS]\
\
=The Stir among European Women.=--Ferment in America, in the case of\
women as of men, was quickened by events in Europe. In 1792, Mary\
Wollstonecraft published in England the _Vindication of the Rights of\
Women_--a book that was destined to serve the cause of liberty among\
women as the writings of Locke and Paine had served that of men. The\
specific grievances which stirred English women were men's invasion of\
women's industries, such as spinning and weaving; the denial of equal\
educational opportunities; and political disabilities. In France also\
the great Revolution raised questionings about the status of women. The\
rights of "citizenesses" as well as the rights of "citizens" were\
examined by the boldest thinkers. This in turn reacted upon women in the\
United States.\
\
=Leadership in America.=--The origins of the American woman movement are\
to be found in the writings of a few early intellectual leaders. During\
the first decades of the nineteenth century, books, articles, and\
pamphlets about women came in increasing numbers from the press. Lydia\
Maria Child wrote a history of women; Margaret Fuller made a critical\
examination of the status of women in her time; and Mrs. Elizabeth Ellet\
supplemented the older histories by showing what an important part women\
had played in the American Revolution.\
\
=The Struggle for Education.=--Along with criticism, there was carried\
on a constructive struggle for better educational facilities for women\
who had been from the beginning excluded from every college in the\
country. In this long battle, Emma Willard and Mary Lyon led the way;\
the former founded a seminary at Troy, New York; and the latter made the\
beginnings of Mount Holyoke College in Massachusetts. Oberlin College in\
Ohio, established in 1833, opened its doors to girls and from it were\
graduated young students to lead in the woman movement. Sarah J. Hale,\
who in 1827 became the editor of a "Ladies' Magazine," published in\
Boston, conducted a campaign for equal educational opportunities which\
helped to bear fruit in the founding of Vassar College shortly after the\
Civil War.\
\
=The Desire to Effect Reforms.=--As they came to study their own history\
and their own part in civilization, women naturally became deeply\
interested in all the controversies going on around them. The temperance\
question made a special appeal to them and they organized to demand the\
right to be heard on it. In 1846 the "Daughters of Temperance" formed a\
secret society favoring prohibition. They dared to criticize the\
churches for their indifference and were so bold as to ask that\
drunkenness be made a ground for divorce.\
\
The slavery issue even more than temperance called women into public\
life. The Grimke sisters of South Carolina emancipated their bondmen,\
and one of these sisters, exiled from Charleston for her "Appeal to the\
Christian Women of the South," went North to work against the slavery\
system. In 1837 the National Women's Anti-Slavery Convention met in New\
York; seventy-one women delegates represented eight states. Three years\
later eight American women, five of them in Quaker costume, attended the\
World Anti-Slavery Convention in London, much to the horror of the men,\
who promptly excluded them from the sessions on the ground that it was\
not fitting for women to take part in such meetings.\
\
In other spheres of activity, especially social service, women steadily\
enlarged their interest. Nothing human did they consider alien to them.\
They inveighed against cruel criminal laws and unsanitary prisons. They\
organized poor relief and led in private philanthropy. Dorothea Dix\
directed the movement that induced the New York legislature to establish\
in 1845 a separate asylum for the criminal insane. In the same year\
Sarah G. Bagley organized the Lowell Female Reform Association for the\
purpose of reducing the long hours of labor for women, safeguarding "the\
constitutions of future generations." Mrs. Eliza Woodson Farnham, matron\
in Sing Sing penitentiary, was known throughout the nation for her\
social work, especially prison reform. Wherever there were misery and\
suffering, women were preparing programs of relief.\
\
=Freedom of Speech for Women.=--In the advancement of their causes, of\
whatever kind, women of necessity had to make public appeals and take\
part in open meetings. Here they encountered difficulties. The\
appearance of women on the platform was new and strange. Naturally it\
was widely resented. Antoinette Brown, although she had credentials as a\
delegate, was driven off the platform of a temperance convention in New\
York City simply because she was a woman. James Russell Lowell, editor\
of the "Atlantic Monthly," declined a poem from Julia Ward Howe on the\
theory that no woman could write a poem; but he added on second thought\
that he might consider an article in prose. Nathaniel Hawthorne,\
another editor, even objected to something in prose because to him "all\
ink-stained women were equally detestable." To the natural resentment\
against their intrusion into new fields was added that aroused by their\
ideas and methods. As temperance reformers, they criticized in a caustic\
manner those who would not accept their opinions. As opponents of\
slavery they were especially bitter. One of their conventions, held at\
Philadelphia in 1833, passed a resolution calling on all women to leave\
those churches that would not condemn every form of human bondage. This\
stirred against them many of the clergy who, accustomed to having women\
sit silent during services, were in no mood to treat such a revolt\
leniently. Then came the last straw. Women decided that they would\
preach--out of the pulpit first, and finally in it.\
\
=Women in Industry.=--The period of this ferment was also the age of the\
industrial revolution in America, the rise of the factory system, and\
the growth of mill towns. The labor of women was transferred from the\
homes to the factories. Then arose many questions: the hours of labor,\
the sanitary conditions of the mills, the pressure of foreign\
immigration on native labor, the wages of women as compared with those\
of men, and the right of married women to their own earnings. Labor\
organizations sprang up among working women. The mill girls of Lowell,\
Massachusetts, mainly the daughters of New England farmers, published a\
magazine, "The Lowell Offering." So excellent were their writings that\
the French statesman, Thiers, carried a copy of their paper into the\
Chamber of Deputies to show what working women could achieve in a\
republic. As women were now admittedly earning their own way in the\
world by their own labor, they began to talk of their "economic\
independence."\
\
=The World Shaken by Revolution.=--Such was the quickening of women's\
minds in 1848 when the world was startled once more by a revolution in\
France which spread to Germany, Poland, Austria, Hungary, and Italy.\
Once more the people of the earth began to explore the principles of\
democracy and expound human rights. Women, now better educated and more\
"advanced" in their ideas, played a role of still greater importance in\
that revolution. They led in agitations and uprisings. They suffered\
from reaction and persecution. From their prison in France, two of them\
who had been jailed for too much insistence on women's rights exchanged\
greetings with American women who were raising the same issue here. By\
this time the women had more supporters among the men. Horace Greeley,\
editor of the New York _Tribune_, though he afterwards recanted, used\
his powerful pen in their behalf. Anti-slavery leaders welcomed their\
aid and repaid them by urging the enfranchisement of women.\
\
=The Woman's Rights Convention of 1848.=--The forces, moral and\
intellectual, which had been stirring among women, crystallized a few\
months after the outbreak of the European revolution in the first\
Woman's Rights Convention in the history of America. It met at Seneca\
Falls, New York, in 1848, on the call of Lucretia Mott, Martha Wright,\
Elizabeth Cady Stanton, and Mary Ann McClintock, three of them Quakers.\
Accustomed to take part in church meetings with men, the Quakers\
naturally suggested that men as well as women be invited to attend the\
convention. Indeed, a man presided over the conference, for that\
position seemed too presumptuous even for such stout advocates of\
woman's rights.\
\
The deliberations of the Seneca Falls convention resulted in a\
Declaration of Rights modeled after the Declaration of Independence. For\
example, the preamble began: "When in the course of human events it\
becomes necessary for one portion of the family of man to assume among\
the people of the earth a position different from that which they have\
hitherto occupied...." So also it closed: "Such has been the patient\
suffering of women under this government and such is now the necessity\
which constrains them to demand the equal station to which they are\
entitled." Then followed the list of grievances, the same number which\
had been exhibited to George III in 1776. Especially did they assail the\
disabilities imposed upon them by the English common law imported into\
America--the law which denied married women their property, their wages,\
and their legal existence as separate persons. All these grievances they\
recited to "a candid world." The remedies for the evils which they\
endured were then set forth in detail. They demanded "equal rights" in\
the colleges, trades, and professions; equal suffrage; the right to\
share in all political offices, honors, and emoluments; the right to\
complete equality in marriage, including equal guardianship of the\
children; and for married women the right to own property, to keep\
wages, to make contracts, to transact business, and to testify in the\
courts of justice. In short, they declared women to be persons as men\
are persons and entitled to all the rights and privileges of human\
beings. Such was the clarion call which went forth to the world in\
1848--to an amused and contemptuous world, it must be admitted--but to a\
world fated to heed and obey.\
\
=The First Gains in Civil Liberty.=--The convention of 1848 did not make\
political enfranchisement the leading issue. Rather did it emphasize the\
civil disabilities of women which were most seriously under discussion\
at the time. Indeed, the New York legislature of that very year, as the\
result of a twelve years' agitation, passed the Married Woman's Property\
Act setting aside the general principles of the English common law as\
applied to women and giving them many of the "rights of man." California\
and Wisconsin followed in 1850; Massachusetts in 1854; and Kansas in\
1859. Other states soon fell into line. Women's earnings and\
inheritances were at last their own in some states at least. In a little\
while laws were passed granting women rights as equal guardians of their\
children and permitting them to divorce their husbands on the grounds of\
cruelty and drunkenness.\
\
By degrees other steps were taken. The Woman's Medical College of\
Pennsylvania was founded in 1850, and the Philadelphia School of Design\
for Women three years later. In 1852 the American Women's Educational\
Association was formed to initiate an agitation for enlarged\
educational opportunities for women. Other colleges soon emulated the\
example of Oberlin: the University of Utah in 1850; Hillsdale College in\
Michigan in 1855; Baker University in Kansas in 1858; and the University\
of Iowa in 1860. New trades and professions were opened to women and old\
prejudices against their activities and demands slowly gave way.\
\
\
THE NATIONAL STRUGGLE FOR WOMAN SUFFRAGE\
\
=The Beginnings of Organization.=--As women surmounted one obstacle\
after another, the agitation for equal suffrage came to the front. If\
any year is to be fixed as the date of its beginning, it may very well\
be 1850, when the suffragists of Ohio urged the state constitutional\
convention to confer the vote upon them. With apparent spontaneity there\
were held in the same year state suffrage conferences in Indiana,\
Pennsylvania, and Massachusetts; and connections were formed among the\
leaders of these meetings. At the same time the first national suffrage\
convention was held in Worcester, Massachusetts, on the call of\
eighty-nine leading men and women representing six states. Accounts of\
the convention were widely circulated in this country and abroad.\
English women,--for instance, Harriet Martineau,--sent words of\
appreciation for the work thus inaugurated. It inspired a leading\
article in the "Westminster Review," which deeply interested the\
distinguished economist, John Stuart Mill. Soon he was the champion of\
woman suffrage in the British Parliament and the author of a powerful\
tract _The Subjection of Women_, widely read throughout the\
English-speaking world. Thus do world movements grow. Strange to relate\
the women of England were enfranchised before the adoption of the\
federal suffrage amendment in America.\
\
The national suffrage convention of 1850 was followed by an\
extraordinary outburst of agitation. Pamphlets streamed from the press.\
Petitions to legislative bodies were drafted, signed, and presented.\
There were addresses by favorite orators like Garrison, Phillips, and\
Curtis, and lectures and poems by men like Emerson, Longfellow, and\
Whittier. In 1853 the first suffrage paper was founded by the wife of a\
member of Congress from Rhode Island. By this time the last barrier to\
white manhood suffrage in the North had been swept away and the woman's\
movement was gaining momentum every year.\
\
=The Suffrage Movement Checked by the Civil War.=--Advocates of woman\
suffrage believed themselves on the high road to success when the Civil\
War engaged the energies and labors of the nation. Northern women became\
absorbed in the struggle to preserve the union. They held no suffrage\
conventions for five years. They transformed their associations into\
Loyalty Leagues. They banded together to buy only domestic goods when\
foreign imports threatened to ruin American markets. They rolled up\
monster petitions in favor of the emancipation of slaves. In hospitals,\
in military prisons, in agriculture, and in industry they bore their\
full share of responsibility. Even when the New York legislature took\
advantage of their unguarded moments and repealed the law giving the\
mother equal rights with the father in the guardianship of children,\
they refused to lay aside war work for agitation. As in all other wars,\
their devotion was unstinted and their sacrifices equal to the\
necessities of the hour.\
\
=The Federal Suffrage Amendment.=--Their plans and activities, when the\
war closed, were shaped by events beyond their control. The emancipation\
of the slaves and their proposed enfranchisement made prominent the\
question of a national suffrage for the first time in our history.\
Friends of the colored man insisted that his civil liberties would not\
be safe unless he was granted the right to vote. The woman suffragists\
very pertinently asked why the same principle did not apply to women.\
The answer which they received was negative. The fourteenth amendment to\
the federal Constitution, adopted in 1868, definitely put women aside by\
limiting the scope of its application, so far as the suffrage was\
concerned, to the male sex. In making manhood suffrage national,\
however, it nationalized the issue.\
\
This was the signal for the advocates of woman suffrage. In March, 1869,\
their proposed amendment was introduced in Congress by George W. Julian\
of Indiana. It provided that no citizen should be deprived of the vote\
on account of sex, following the language of the fifteenth amendment\
which forbade disfranchisement on account of race. Support for the\
amendment, coming from many directions, led the suffragists to believe\
that their case was hopeful. In their platform of 1872, for example, the\
Republicans praised the women for their loyal devotion to freedom,\
welcomed them to spheres of wider usefulness, and declared that the\
demand of any class of citizens for additional rights deserved\
"respectful consideration."\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
SUSAN B. ANTHONY]\
\
Experience soon demonstrated, however, that praise was not the ballot.\
Indeed the suffragists already had realized that a tedious contest lay\
before them. They had revived in 1866 their regular national convention.\
They gave the name of "The Revolution" to their paper, edited by\
Elizabeth Cady Stanton and Susan B. Anthony. They formed a national\
suffrage association and organized annual pilgrimages to Congress to\
present their claims. Such activities bore some results. Many eminent\
congressmen were converted to their cause and presented it ably to their\
colleagues of both chambers. Still the subject was ridiculed by the\
newspapers and looked upon as freakish by the masses.\
\
=The State Campaigns.=--Discouraged by the outcome of the national\
campaign, suffragists turned to the voters of the individual states and\
sought the ballot at their hands. Gains by this process were painfully\
slow. Wyoming, it is true, while still a territory, granted suffrage to\
women in 1869 and continued it on becoming a state twenty years later,\
in spite of strong protests in Congress. In 1893 Colorado established\
complete political equality. In Utah, the third suffrage state, the\
cause suffered many vicissitudes. Women were enfranchised by the\
territorial legislature; they were deprived of the ballot by Congress in\
1887; finally in 1896 on the admission of Utah to the union they\
recovered their former rights. During the same year, 1896, Idaho\
conferred equal suffrage upon the women. This was the last suffrage\
victory for more than a decade.\
\
=The Suffrage Cause in Congress.=--In the midst of the meager gains\
among the states there were occasional flurries of hope for immediate\
action on the federal amendment. Between 1878 and 1896 the Senate\
committee reported the suffrage resolution by a favorable majority on\
five different occasions. During the same period, however, there were\
nine unfavorable reports and only once did the subject reach the point\
of a general debate. At no time could anything like the required\
two-thirds vote be obtained.\
\
=The Changing Status of Women.=--While the suffrage movement was\
lagging, the activities of women in other directions were steadily\
multiplying. College after college--Vassar, Bryn Mawr, Smith, Wellesley,\
to mention a few--was founded to give them the advantages of higher\
education. Other institutions, especially the state universities of the\
West, opened their doors to women, and women were received into the\
professions of law and medicine. By the rapid growth of public high\
schools in which girls enjoyed the same rights as boys, education was\
extended still more widely. The number of women teachers increased by\
leaps and bounds.\
\
Meanwhile women were entering nearly every branch of industry and\
business. How many of them worked at gainful occupations before 1870 we\
do not know; but from that year forward we have the records of the\
census. Between 1870 and 1900 the proportion of women in the professions\
rose from less than two per cent to more than ten per cent; in trade and\
transportation from 24.8 per cent to 43.2 per cent; and in manufacturing\
from 13 to 19 per cent. In 1910, there were over 8,000,000 women\
gainfully employed as compared with 30,000,000 men. When, during the war\
on Germany, the government established the principle of equal pay for\
equal work and gave official recognition to the value of their services\
in industry, it was discovered how far women had traveled along the road\
forecast by the leaders of 1848.\
\
=The Club Movement among Women.=--All over the country women's societies\
and clubs were started to advance this or that reform or merely to study\
literature, art, and science. In time these women's organizations of all\
kinds were federated into city, state, and national associations and\
drawn into the consideration of public questions. Under the leadership\
of Frances Willard they made temperance reform a vital issue. They took\
an interest in legislation pertaining to prisons, pure food, public\
health, and municipal government, among other things. At their sessions\
and conferences local, state, and national issues were discussed until\
finally, it seems, everything led to the quest of the franchise. By\
solemn resolution in 1914 the National Federation of Women's Clubs,\
representing nearly two million club women, formally endorsed woman\
suffrage. In the same year the National Education Association, speaking\
for the public school teachers of the land, added its seal of approval.\
\
=State and National Action.=--Again the suffrage movement was in full\
swing in the states. Washington in 1910, California in 1911, Oregon,\
Kansas, and Arizona in 1912, Nevada and Montana in 1914 by popular vote\
enfranchised their women. Illinois in 1913 conferred upon them the right\
to vote for President of the United States. The time had arrived for a\
new movement. A number of younger suffragists sought to use the votes of\
women in the equal suffrage states to compel one or both of the national\
political parties to endorse and carry through Congress the federal\
suffrage amendment. Pressure then came upon Congress from every\
direction: from the suffragists who made a straight appeal on the\
grounds of justice; and from the suffragists who besought the women of\
the West to vote against candidates for President, who would not approve\
the federal amendment. In 1916, for the first time, a leading\
presidential candidate, Mr. Charles E. Hughes, speaking for the\
Republicans, endorsed the federal amendment and a distinguished\
ex-President, Roosevelt, exerted a powerful influence to keep it an\
issue in the campaign.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
CONFERENCE OF MEN AND WOMEN DELEGATES AT A NATIONAL CONVENTION IN\
1920]\
\
=National Enfranchisement.=--After that, events moved rapidly. The great\
state of New York adopted equal suffrage in 1917. Oklahoma, South\
Dakota, and Michigan swung into line the following year; several other\
states, by legislative action, gave women the right to vote for\
President. In the meantime the suffrage battle at Washington grew\
intense. Appeals and petitions poured in upon Congress and the\
President. Militant suffragists held daily demonstrations in Washington.\
On September 30, 1918, President Wilson, who, two years before, had\
opposed federal action and endorsed suffrage by state adoption only,\
went before Congress and urged the passage of the suffrage amendment to\
the Constitution. In June, 1919, the requisite two-thirds vote was\
secured; the resolution was carried and transmitted to the states for\
ratification. On August 28, 1920, the thirty-sixth state, Tennessee,\
approved the amendment, making three-fourths of the states as required\
by the Constitution. Thus woman suffrage became the law of the land. A\
new political democracy had been created. The age of agitation was\
closed and the epoch of responsible citizenship opened.\
\
\
=General References=\
\
Edith Abbott, _Women in Industry_.\
\
C.P. Gilman, _Woman and Economics_.\
\
I.H. Harper, _Life and Work of Susan B. Anthony_.\
\
E.R. Hecker, _Short History of Woman's Rights_.\
\
S.B. Anthony and I.H. Harper, _History of Woman Suffrage_ (4 vols.).\
\
J.W. Taylor, _Before Vassar Opened_.\
\
A.H. Shaw, _The Story of a Pioneer_.\
\
\
=Research Topics=\
\
=The Rise of the Woman Suffrage Movement.=--McMaster, _History of the\
People of the United States_, Vol. VIII, pp. 116-121; K. Porter,\
_History of Suffrage in the United States_, pp. 135-145.\
\
=The Development of the Suffrage Movement.=--Porter, pp. 228-254; Ogg,\
_National Progress_ (American Nation Series), pp. 151-156 and p. 382.\
\
=Women's Labor in the Colonial Period.=--E. Abbott, _Women in Industry_,\
pp. 10-34.\
\
=Women and the Factory System.=--Abbott, pp. 35-62.\
\
=Early Occupations for Women.=--Abbott, pp. 63-85.\
\
=Women's Wages.=--Abbott, pp. 262-316.\
\
\
=Questions=\
\
1. Why were women involved in the reform movements of the new century?\
\
2. What is history? What determines the topics that appear in written\
history?\
\
3. State the position of women under the old common law.\
\
4. What part did women play in the intellectual movement that preceded\
the American Revolution?\
\
5. Explain the rise of the discussion of women's rights.\
\
6. What were some of the early writings about women?\
\
7. Why was there a struggle for educational opportunities?\
\
8. How did reform movements draw women into public affairs and what were\
the chief results?\
\
9. Show how the rise of the factory affected the life and labor of\
women.\
\
10. Why is the year 1848 an important year in the woman movement?\
Discuss the work of the Seneca Falls convention.\
\
11. Enumerate some of the early gains in civil liberty for women.\
\
12. Trace the rise of the suffrage movement. Show the effect of the\
Civil War.\
\
13. Review the history of the federal suffrage amendment.\
\
14. Summarize the history of the suffrage in the states.\
\
\
\
\
CHAPTER XXIV\
\
INDUSTRIAL DEMOCRACY\
\
\
=The New Economic Age.=--The spirit of criticism and the measures of\
reform designed to meet it, which characterized the opening years of the\
twentieth century, were merely the signs of a new age. The nation had\
definitely passed into industrialism. The number of city dwellers\
employed for wages as contrasted with the farmers working on their own\
land was steadily mounting. The free land, once the refuge of restless\
workingmen of the East and the immigrants from Europe, was a thing of\
the past. As President Roosevelt later said in speaking of the great\
coal strike, "a few generations ago, the American workman could have\
saved money, gone West, and taken up a homestead. Now the free lands\
were gone. In earlier days, a man who began with a pick and shovel might\
come to own a mine. That outlet was now closed as regards the immense\
majority.... The majority of men who earned wages in the coal industry,\
if they wished to progress at all, were compelled to progress not by\
ceasing to be wage-earners but by improving the conditions under which\
all the wage-earners of the country lived and worked."\
\
The disappearance of the free land, President Roosevelt went on to say,\
also produced "a crass inequality in the bargaining relation of the\
employer and the individual employee standing alone. The great\
coal-mining and coal-carrying companies which employed their tens of\
thousands could easily dispense with the services of any particular\
miner. The miner, on the other hand, however expert, could not dispense\
with the companies. He needed a job; his wife and children would starve\
if he did not get one.... Individually the miners were impotent when\
they sought to enter a wage contract with the great companies; they\
could make fair terms only by uniting into trade unions to bargain\
collectively." It was of this state of affairs that President Taft spoke\
when he favored the modification of the common law "so as to put\
employees of little power and means on a level with their employers in\
adjusting and agreeing upon their mutual obligations."\
\
John D. Rockefeller, Jr., on the side of the great captains of industry,\
recognized the same facts. He said: "In the early days of the\
development of industry, the employer and capital investor were\
frequently one. Daily contact was had between him and his employees, who\
were his friends and neighbors.... Because of the proportions which\
modern industry has attained, employers and employees are too often\
strangers to each other.... Personal relations can be revived only\
through adequate representation of the employees. Representation is a\
principle which is fundamentally just and vital to the successful\
conduct of industry.... It is not consistent for us as Americans to\
demand democracy in government and practice autocracy in industry....\
With the developments what they are in industry to-day, there is sure to\
come a progressive evolution from aristocratic single control, whether\
by capital, labor, or the state, to democratic, cooperative control by\
all three."\
\
\
COOPERATION BETWEEN EMPLOYERS AND EMPLOYEES\
\
=Company Unions.=--The changed economic life described by the three\
eminent men just quoted was acknowledged by several great companies and\
business concerns. All over the country decided efforts were made to\
bridge the gulf which industry and the corporation had created. Among\
the devices adopted was that of the "company union." In one of the\
Western lumber mills, for example, all the employees were invited to\
join a company organization; they held monthly meetings to discuss\
matters of common concern; they elected a "shop committee" to confer\
with the representatives of the company; and periodically the agents of\
the employers attended the conferences of the men to talk over matters\
of mutual interest. The function of the shop committee was to consider\
wages, hours, safety rules, sanitation, recreation and other problems.\
Whenever any employee had a grievance he took it up with the foreman\
and, if it was not settled to his satisfaction, he brought it before the\
shop committee. If the members of the shop committee decided in favor of\
the man with a grievance, they attempted to settle the matter with the\
company's agents. All these things failing, the dispute was transferred\
to a grand meeting of all the employees with the employers'\
representatives, in common council. A deadlock, if it ensued from such a\
conference, was broken by calling in impartial arbitrators selected by\
both sides from among citizens outside the mill. Thus the employees were\
given a voice in all decisions affecting their work and welfare; rights\
and grievances were treated as matters of mutual interest rather than\
individual concern. Representatives of trade unions from outside,\
however, were rigidly excluded from all negotiations between employers\
and the employees.\
\
=Profit-sharing.=--Another proposal for drawing capital and labor\
together was to supplement the wage system by other ties. Sometimes lump\
sums were paid to employees who remained in a company's service for a\
definite period of years. Again they were given a certain percentage of\
the annual profits. In other instances, employees were allowed to buy\
stock on easy terms and thus become part owners in the concern. This\
last plan was carried so far by a large soap manufacturing company that\
the employees, besides becoming stockholders, secured the right to elect\
representatives to serve on the board of directors who managed the\
entire business. So extensive had profit-sharing become by 1914 that the\
Federal Industrial Relations Committee, appointed by the President,\
deemed it worthy of a special study. Though opposed by regular trade\
unions, it was undoubtedly growing in popularity.\
\
=Labor Managers and Welfare Work.=--Another effort of employers to meet\
the problems of the new age appeared in the appointment of specialists,\
known as employment managers, whose task it was to study the relations\
existing between masters and workers and discover practical methods for\
dealing with each grievance as it arose. By 1918, hundreds of big\
companies had recognized this modern "profession" and universities were\
giving courses of instruction on the subject to young men and women. In\
that year a national conference of employment managers was held at\
Rochester, New York. The discussion revealed a wide range of duties\
assigned to managers, including questions of wages, hours, sanitation,\
rest rooms, recreational facilities, and welfare work of every kind\
designed to make the conditions in mills and factories safer and more\
humane. Thus it was evident that hundreds of employers had abandoned the\
old idea that they were dealing merely with individual employees and\
that their obligations ended with the payment of any wages they saw fit\
to fix. In short, they were seeking to develop a spirit of cooperation\
to take the place of competition and enmity; and to increase the\
production of commodities by promoting the efficiency and happiness of\
the producers.\
\
\
THE RISE AND GROWTH OF ORGANIZED LABOR\
\
=The American Federation of Labor.=--Meanwhile a powerful association of\
workers representing all the leading trades and crafts, organized into\
unions of their own, had been built up outside the control of employers.\
This was the American Federation of Labor, a nation-wide union of\
unions, founded in 1886 on the basis of beginnings made five years\
before. At the time of its establishment it had approximately 150,000\
members. Its growth up to the end of the century was slow, for the total\
enrollment in 1900 was only 300,000. At that point the increase became\
marked. The membership reached 1,650,000 in 1904 and more than 3,000,000\
in 1919. To be counted in the ranks of organized labor were several\
strong unions, friendly to the Federation, though not affiliated with\
it. Such, for example, were the Railway Brotherhoods with more than half\
a million members. By the opening of 1920 the total strength of\
organized labor was put at about 4,000,000 members, meaning, if we\
include their families, that nearly one-fifth of the people of the\
United States were in some positive way dependent upon the operations of\
trade unions.\
\
=Historical Background.=--This was the culmination of a long and\
significant history. Before the end of the eighteenth century, the\
skilled workmen--printers, shoemakers, tailors, and carpenters--had, as\
we have seen, formed local unions in the large cities. Between 1830 and\
1860, several aggressive steps were taken in the American labor\
movement. For one thing, the number of local unions increased by leaps\
and bounds in all the industrial towns. For another, there was\
established in every large manufacturing city a central labor body\
composed of delegates from the unions of the separate trades. In the\
local union the printers or the cordwainers, for example, considered\
only their special trade problems. In the central labor union, printers,\
cordwainers, iron molders, and other craftsmen considered common\
problems and learned to cooperate with one another in enforcing the\
demands of each craft. A third step was the federation of the unions of\
the same craftsmen in different cities. The printers of New York,\
Philadelphia, Boston, and other towns, for instance, drew together and\
formed a national trade union of printers built upon the local unions of\
that craft. By the eve of the Civil War there were four or five powerful\
national unions of this character. The expansion of the railway made\
travel and correspondence easier and national conventions possible even\
for workmen of small means. About 1834 an attempt was made to federate\
the unions of all the different crafts into a national organization; but\
the effort was premature.\
\
_The National Labor Union._--The plan which failed in 1834 was tried\
again in the sixties. During the war, industries and railways had\
flourished as never before; prices had risen rapidly; the demand for\
labor had increased; wages had mounted slowly, but steadily. Hundreds of\
new local unions had been founded and eight or ten national trade unions\
had sprung into being. The time was ripe, it seemed, for a national\
consolidation of all labor's forces; and in 1866, the year after the\
surrender of General Lee at Appomattox, the "National Labor Union" was\
formed at Baltimore under the leadership of an experienced organizer,\
W.H. Sylvis of the iron molders. The purpose of the National Labor Union\
was not merely to secure labor's standard demands touching hours, wages,\
and conditions of work or to maintain the gains already won. It leaned\
toward political action and radical opinions. Above all, it sought to\
eliminate the conflict between capital and labor by making workingmen\
the owners of shops through the formation of cooperative industries. For\
six years the National Labor Union continued to hold conferences and\
carry on its propaganda; but most of the cooperative enterprises failed,\
political dissensions arose, and by 1872 the experiment had come to an\
end.\
\
_The Knights of Labor._--While the National Labor Union was\
experimenting, there grew up in the industrial world a more radical\
organization known as the "Noble Order of the Knights of Labor." It was\
founded in Philadelphia in 1869, first as a secret society with rituals,\
signs, and pass words; "so that no spy of the boss can find his way into\
the lodge room to betray his fellows," as the Knights put it. In form\
the new organization was simple. It sought to bring all laborers,\
skilled and unskilled, men and women, white and colored, into a mighty\
body of local and national unions without distinction of trade or craft.\
By 1885, ten years after the national organization was established, it\
boasted a membership of over 700,000. In philosophy, the Knights of\
Labor were socialistic, for they advocated public ownership of the\
railways and other utilities and the formation of cooperative societies\
to own and manage stores and factories.\
\
As the Knights were radical in spirit and their strikes, numerous and\
prolonged, were often accompanied by violence, the organization alarmed\
employers and the general public, raising up against itself a vigorous\
opposition. Weaknesses within, as well as foes from without, started the\
Knights on the path to dissolution. They waged more strikes than they\
could carry on successfully; their cooperative experiments failed as\
those of other labor groups before them had failed; and the rank and\
file could not be kept in line. The majority of the members wanted\
immediate gains in wages or the reduction of hours; when their hopes\
were not realized they drifted away from the order. The troubles were\
increased by the appearance of the American Federation of Labor, a still\
mightier organization composed mainly of skilled workers who held\
strategic positions in industry. When they failed to secure the\
effective support of the Federation in their efforts to organize the\
unskilled, the employers closed in upon them; then the Knights declined\
rapidly in power. By 1890 they were a negligible factor and in a short\
time they passed into the limbo of dead experiments.\
\
=The Policies of the American Federation.=--Unlike the Knights of Labor,\
the American Federation of Labor sought, first of all, to be very\
practical in its objects and methods. It avoided all kinds of\
socialistic theories and attended strictly to the business of organizing\
unions for the purpose of increasing wages, shortening hours, and\
improving working conditions for its members. It did not try to include\
everybody in one big union but brought together the employees of each\
particular craft whose interests were clearly the same. To prepare for\
strikes and periods of unemployment, it raised large funds by imposing\
heavy dues and created a benefit system to hold men loyally to the\
union. In order to permit action on a national scale, it gave the\
superior officers extensive powers over local unions.\
\
While declaring that employers and employees had much in common, the\
Federation strongly opposed company unions. Employers, it argued, were\
affiliated with the National Manufacturers' Association or with similar\
employers' organizations; every important industry was now national in\
scope; and wages and hours, in view of competition with other shops,\
could not be determined in a single factory, no matter how amicable\
might be the relations of the company and its workers in that particular\
plant. For these reasons, the Federation declared company unions and\
local shop committees inherently weak; it insisted that hours, wages,\
and other labor standards should be fixed by general trade agreements\
applicable to all the plants of a given industry, even if subject to\
local modifications.\
\
At the same time, the Federation, far from deliberately antagonizing\
employers, sought to enlist their cooperation and support. It affiliated\
with the National Civic Federation, an association of business men,\
financiers, and professional men, founded in 1900 to promote friendly\
relations in the industrial world. In brief, the American Federation of\
Labor accepted the modern industrial system and, by organization within\
it, endeavored to secure certain definite terms and conditions for trade\
unionists.\
\
\
THE WIDER RELATIONS OF ORGANIZED LABOR\
\
=The Socialists.=--The trade unionism "pure and simple," espoused by the\
American Federation of Labor, seemed to involve at first glance nothing\
but businesslike negotiations with employers. In practice it did not\
work out that way. The Federation was only six years old when a new\
organization, appealing directly for the labor vote--namely, the\
Socialist Labor Party--nominated a candidate for President, launched\
into a national campaign, and called upon trade unionists to desert the\
older parties and enter its fold.\
\
The socialistic idea, introduced into national politics in 1892, had\
been long in germination. Before the Civil War, a number of reformers,\
including Nathaniel Hawthorne, Horace Greeley, and Wendell Phillips,\
deeply moved by the poverty of the great industrial cities, had\
earnestly sought relief in the establishment of cooperative or\
communistic colonies. They believed that people should go into the\
country, secure land and tools, own them in common so that no one could\
profit from exclusive ownership, and produce by common labor the food\
and clothing necessary for their support. For a time this movement\
attracted wide interest, but it had little vitality. Nearly all the\
colonies failed. Selfishness and indolence usually disrupted the best of\
them.\
\
In the course of time this "Utopian" idea was abandoned, and another set\
of socialist doctrines, claiming to be more "scientific," appeared\
instead. The new school of socialists, adopting the principles of a\
German writer and agitator, Karl Marx, appealed directly to workingmen.\
It urged them to unite against the capitalists, to get possession of the\
machinery of government, and to introduce collective or public ownership\
of railways, land, mines, mills, and other means of production. The\
Marxian socialists, therefore, became political. They sought to organize\
labor and to win elections. Like the other parties they put forward\
candidates and platforms. The Socialist Labor party in 1892, for\
example, declared in favor of government ownership of utilities, free\
school books, woman suffrage, heavy income taxes, and the referendum.\
The Socialist party, founded in 1900, with Eugene V. Debs, the leader of\
the Pullman strike, as its candidate, called for public ownership of all\
trusts, monopolies, mines, railways; and the chief means of production.\
In the course of time the vote of the latter organization rose to\
considerable proportions, reaching almost a million in 1912. It declined\
four years later and then rose in 1920 to about the same figure.\
\
In their appeal for votes, the socialists of every type turned first to\
labor. At the annual conventions of the American Federation of Labor\
they besought the delegates to endorse socialism. The president of the\
Federation, Samuel Gompers, on each occasion took the floor against\
them. He repudiated socialism and the socialists, on both theoretical\
and practical grounds. He opposed too much public ownership, declaring\
that the government was as likely as any private employer to oppress\
labor. The approval of socialism, he maintained, would split the\
Federation on the rock of politics, weaken it in its fight for higher\
wages and shorter hours, and prejudice the public against it. At every\
turn he was able to vanquish the socialists in the Federation, although\
he could not prevent it from endorsing public ownership of the railways\
at the convention of 1920.\
\
=The Extreme Radicals.=--Some of the socialists, defeated in their\
efforts to capture organized labor and seeing that the gains in\
elections were very meager, broke away from both trade unionism and\
politics. One faction, the Industrial Workers of the World, founded in\
1905, declared themselves opposed to all capitalists, the wages system,\
and craft unions. They asserted that the "working class and the\
employing class have nothing in common" and that trade unions only\
pitted one set of workers against another set. They repudiated all\
government ownership and the government itself, boldly proclaiming their\
intention to unite all employees into one big union and seize the\
railways, mines, and mills of the country. This doctrine, so\
revolutionary in tone, called down upon the extremists the condemnation\
of the American Federation of Labor as well as of the general public. At\
its convention in 1919, the Federation went on record as "opposed to\
Bolshevism, I.W.W.-ism, and the irresponsible leadership that encourages\
such a policy." It announced its "firm adherence to American ideals."\
\
=The Federation and Political Issues.=--The hostility of the Federation\
to the socialists did not mean, however, that it was indifferent to\
political issues or political parties. On the contrary, from time to\
time, at its annual conventions, it endorsed political and social\
reforms, such as the initiative, referendum, and recall, the abolition\
of child labor, the exclusion of Oriental labor, old-age pensions, and\
government ownership. Moreover it adopted the policy of "rewarding\
friends and punishing enemies" by advising members to vote for or\
against candidates according to their stand on the demands of organized\
labor.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
SAMUEL GOMPERS AND OTHER LABOR LEADERS]\
\
This policy was pursued with especial zeal in connection with disputes\
over the use of injunctions in labor controversies. An injunction is a\
bill or writ issued by a judge ordering some person or corporation to do\
or to refrain from doing something. For example, a judge may order a\
trade union to refrain from interfering with non-union men or to\
continue at work handling goods made by non-union labor; and he may fine\
or imprison those who disobey his injunction, the penalty being\
inflicted for "contempt of court." This ancient legal device came into\
prominence in connection with nation-wide railway strikes in 1877. It\
was applied with increasing frequency after its effective use against\
Eugene V. Debs in the Pullman strike of 1894.\
\
Aroused by the extensive use of the writ, organized labor demanded that\
the power of judges to issue injunctions in labor disputes be limited by\
law. Representatives of the unions sought support from the Democrats and\
the Republicans; they received from the former very specific and cordial\
endorsement. In 1896 the Democratic platform denounced "government by\
injunction as a new and highly dangerous form of oppression." Mr.\
Gompers, while refusing to commit the Federation to Democratic politics,\
privately supported Mr. Bryan. In 1908, he came out openly and boasted\
that eighty per cent of the votes of the Federation had been cast for\
the Democratic candidate. Again in 1912 the same policy was pursued. The\
reward was the enactment in 1914 of a federal law exempting trade unions\
from prosecution as combinations in restraint of trade, limiting the use\
of the injunction in labor disputes, and prescribing trial by jury in\
case of contempt of court. This measure was hailed by Mr. Gompers as the\
"Magna Carta of Labor" and a vindication of his policy. As a matter of\
fact, however, it did not prevent the continued use of injunctions\
against trade unions. Nevertheless Mr. Gompers was unshaken in his\
conviction that organized labor should not attempt to form an\
independent political party or endorse socialist or other radical\
economic theories.\
\
=Organized Labor and the Public.=--Besides its relations to employers,\
radicals within its own ranks, and political questions, the Federation\
had to face responsibilities to the general public. With the passing of\
time these became heavy and grave. While industries were small and\
conflicts were local in character, a strike seldom affected anybody but\
the employer and the employees immediately involved in it. When,\
however, industries and trade unions became organized on a national\
scale and a strike could paralyze a basic enterprise like coal mining or\
railways, the vital interests of all citizens were put in jeopardy.\
Moreover, as increases in wages and reductions in hours often added\
directly to the cost of living, the action of the unions affected the\
well-being of all--the food, clothing, and shelter of the whole people.\
\
For the purpose of meeting the issue raised by this state of affairs, it\
was suggested that employers and employees should lay their disputes\
before commissions of arbitration for decision and settlement. President\
Cleveland, in a message of April 2, 1886, proposed such a method for\
disposing of industrial controversies, and two years later Congress\
enacted a voluntary arbitration law applicable to the railways. The\
principle was extended in 1898 and again in 1913, and under the\
authority of the federal government many contentions in the railway\
world were settled by arbitration.\
\
The success of such legislation induced some students of industrial\
questions to urge that unions and employers should be compelled to\
submit all disputes to official tribunals of arbitration. Kansas\
actually passed such a law in 1920. Congress in the Esch-Cummins railway\
bill of the same year created a federal board of nine members to which\
all railway controversies, not settled by negotiation, must be\
submitted. Strikes, however, were not absolutely forbidden. Generally\
speaking, both employers and employees opposed compulsory adjustments\
without offering any substitute in case voluntary arbitration should not\
be accepted by both parties to a dispute.\
\
\
IMMIGRATION AND AMERICANIZATION\
\
=The Problems of Immigration.=--From its very inception, the American\
Federation of Labor, like the Knights of Labor before it, was confronted\
by numerous questions raised by the ever swelling tide of aliens coming\
to our shores. In its effort to make each trade union all-inclusive, it\
had to wrestle with a score or more languages. When it succeeded in\
thoroughly organizing a craft, it often found its purposes defeated by\
an influx of foreigners ready to work for lower wages and thus undermine\
the foundations of the union.\
\
At the same time, persons outside the labor movement began to be\
apprehensive as they contemplated the undoubted evil, as well as the\
good, that seemed to be associated with the "alien invasion." They saw\
whole sections of great cities occupied by people speaking foreign\
tongues, reading only foreign newspapers, and looking to the Old World\
alone for their ideas and their customs. They witnessed an expanding\
army of total illiterates, men and women who could read and write no\
language at all; while among those aliens who could read few there were\
who knew anything of American history, traditions, and ideals. Official\
reports revealed that over twenty per cent of the men of the draft army\
during the World War could not read a newspaper or write a letter home.\
Perhaps most alarming of all was the discovery that thousands of alien\
men are in the United States only on a temporary sojourn, solely to make\
money and return home with their savings. These men, willing to work for\
low wages and live in places unfit for human beings, have no stake in\
this country and do not care what becomes of it.\
\
=The Restriction of Immigration.=--In all this there was, strictly\
speaking, no cause for surprise. Since the foundation of our republic\
the policy of the government had been to encourage the coming of the\
alien. For nearly one hundred years no restraining act was passed by\
Congress, while two important laws positively encouraged it; namely, the\
homestead act of 1862 and the contract immigration law of 1864. Not\
until American workingmen came into open collision with cheap Chinese\
labor on the Pacific Coast did the federal government spread the first\
measure of limitation on the statute books. After the discovery of gold,\
and particularly after the opening of the railway construction era, a\
horde of laborers from China descended upon California. Accustomed to\
starvation wages and indifferent to the conditions of living, they\
threatened to cut the American standard to the point of subsistence. By\
1876 the protest of American labor was loud and long and both the\
Republicans and the Democrats gave heed to it. In 1882 Congress enacted\
a law prohibiting the admission of Chinese laborers to the United States\
for a term of ten years--later extended by legislation. In a little\
while the demand arose for the exclusion of the Japanese as well. In\
this case no exclusion law was passed; but an understanding was reached\
by which Japan agreed not to issue passports to her laborers authorizing\
them to come to the United States. By act of Congress in 1907 the\
President was empowered to exclude any laborers who, having passports to\
Canada, Hawaii, or Mexico, attempted to enter our country.\
\
These laws and agreements, however, did not remove all grounds for the\
agitation of the subject. They were difficult to enforce and it was\
claimed by residents of the Coast that in spite of federal authority\
Oriental laborers were finding their way into American ports. Moreover,\
several Western states, anxious to preserve the soil for American\
ownership, enacted laws making it impossible for Chinese and Japanese to\
buy land outright; and in other ways they discriminated against\
Orientals. Such proceedings placed the federal government in an\
embarrassing position. By treaty it had guaranteed specific rights to\
Japanese citizens in the United States, and the government at Tokyo\
contended that the state laws just cited violated the terms of the\
international agreement. The Western states were fixed in their\
determination to control Oriental residents; Japan was equally\
persistent in asking that no badge of inferiority be attached to her\
citizens. Subjected to pressure on both sides, the federal government\
sought a way out of the deadlock.\
\
Having embarked upon the policy of restriction in 1882, Congress readily\
extended it. In that same year it barred paupers, criminals, convicts,\
and the insane. Three years later, mainly owing to the pressure of the\
Knights of Labor, it forbade any person, company, or association to\
import aliens under contract. By an act of 1887, the contract labor\
restriction was made even more severe. In 1903, anarchists were excluded\
and the bureau of immigration was transferred from the Treasury\
Department to the Department of Commerce and Labor, in order to provide\
for a more rigid execution of the law. In 1907 the classes of persons\
denied admission were widened to embrace those suffering from physical\
and mental defects and otherwise unfit for effective citizenship. When\
the Department of Labor was established in 1913 the enforcement of the\
law was placed in the hands of the Secretary of Labor, W.B. Wilson, who\
was a former leader in the American Federation of Labor.\
\
=The Literacy Test.=--Still the advocates of restriction were not\
satisfied. Still organized labor protested and demanded more protection\
against the competition of immigrants. In 1917 it won a thirty-year\
battle in the passage of a bill excluding "all aliens over sixteen years\
of age, physically capable of reading, who cannot read the English\
language or some other language or dialect, including Hebrew or\
Yiddish." Even President Wilson could not block it, for a two-thirds\
vote to overcome his veto was mustered in Congress.\
\
This act, while it served to exclude illiterates, made no drastic cut in\
the volume of immigration. Indeed a material reduction was resolutely\
opposed in many quarters. People of certain nationalities already in the\
United States objected to every barrier that shut out their own kinsmen.\
Some Americans of the old stock still held to the idea that the United\
States should continue to be an asylum for "the oppressed of the earth."\
Many employers looked upon an increased labor supply as the means of\
escaping what they called "the domination of trade unions." In the babel\
of countless voices, the discussion of these vital matters went on in\
town and country.\
\
=Americanization.=--Intimately connected with the subject of immigration\
was a call for the "Americanization" of the alien already within our\
gates. The revelation of the illiteracy in the army raised the cry and\
the demand was intensified when it was found that many of the leaders\
among the extreme radicals were foreign in birth and citizenship.\
Innumerable programs for assimilating the alien to American life were\
drawn up, and in 1919 a national conference on the subject was held in\
Washington under the auspices of the Department of the Interior. All\
were agreed that the foreigner should be taught to speak and write the\
language and understand the government of our country. Congress was\
urged to lend aid in this vast undertaking. America, as ex-President\
Roosevelt had said, was to find out "whether it was a nation or a\
boarding-house."\
\
\
=General References=\
\
J.R. Commons and Associates, _History of Labor in the United States_ (2\
vols.).\
\
Samuel Gompers, _Labor and the Common Welfare_.\
\
W.E. Walling, _Socialism as It Is_.\
\
W.E. Walling (and Others), _The Socialism of Today_.\
\
R.T. Ely, _The Labor Movement in America_.\
\
T.S. Adams and H. Sumner, _Labor Problems_.\
\
J.G. Brooks, _American Syndicalism_ and _Social Unrest_.\
\
P.F. Hall, _Immigration and Its Effects on the United States_.\
\
\
=Research Topics=\
\
=The Rise of Trade Unionism.=--Mary Beard, _Short History of the\
American Labor Movement_, pp. 10-18, 47-53, 62-79; Carlton, _Organized\
Labor in American History_, pp. 11-44.\
\
=Labor and Politics.=--Beard, _Short History_, pp. 33-46, 54-61,\
103-112; Carlton, pp. 169-197; Ogg, _National Progress_ (American Nation\
Series), pp. 76-85.\
\
=The Knights of Labor.=--Beard, _Short History_, pp. 116-126; Dewey,\
_National Problems_ (American Nation Series), pp. 40-49.\
\
=The American Federation of Labor--Organization and Policies.=--Beard,\
_Short History_, pp. 86-112.\
\
=Organized Labor and the Socialists.=--Beard, _Short History_, pp.\
126-149.\
\
=Labor and the Great War.=--Carlton, pp. 282-306; Beard, _Short\
History_, pp. 150-170.\
\
\
=Questions=\
\
1. What are the striking features of the new economic age?\
\
2. Give Mr. Rockefeller's view of industrial democracy.\
\
3. Outline the efforts made by employers to establish closer relations\
with their employees.\
\
4. Sketch the rise and growth of the American Federation of Labor.\
\
5. How far back in our history does the labor movement extend?\
\
6. Describe the purposes and outcome of the National Labor Union and the\
Knights of Labor.\
\
7. State the chief policies of the American Federation of Labor.\
\
8. How does organized labor become involved with outside forces?\
\
9. Outline the rise of the socialist movement. How did it come into\
contact with the American Federation?\
\
10. What was the relation of the Federation to the extreme radicals? To\
national politics? To the public?\
\
11. Explain the injunction.\
\
12. Why are labor and immigration closely related?\
\
13. Outline the history of restrictions on immigration.\
\
14. What problems arise in connection with the assimilation of the alien\
to American life?\
\
\
\
\
CHAPTER XXV\
\
PRESIDENT WILSON AND THE WORLD WAR\
\
\
"The welfare, the happiness, the energy, and the spirit of the men and\
women who do the daily work in our mines and factories, on our\
railroads, in our offices and ports of trade, on our farms, and on the\
sea are the underlying necessity of all prosperity." Thus spoke Woodrow\
Wilson during his campaign for election. In this spirit, as President,\
he gave the signal for work by summoning Congress in a special session\
on April 7, 1913. He invited the cooperation of all "forward-looking\
men" and indicated that he would assume the role of leadership. As an\
evidence of his resolve, he appeared before Congress in person to read\
his first message, reviving the old custom of Washington and Adams. Then\
he let it be known that he would not give his party any rest until it\
fulfilled its pledges to the country. When Democratic Senators balked at\
tariff reductions, they were sharply informed that the party had\
plighted its word and that no excuses or delays would be tolerated.\
\
\
DOMESTIC LEGISLATION\
\
=Financial Measures.=--Under this spirited leadership Congress went to\
work, passing first the Underwood tariff act of 1913, which made a\
downward revision in the rates of duty, fixing them on the average about\
twenty-six per cent lower than the figures of 1907. The protective\
principle was retained, but an effort was made to permit a moderate\
element of foreign competition. As a part of the revenue act Congress\
levied a tax on incomes as authorized by the sixteenth amendment to the\
Constitution. The tax which roused such party passions twenty years\
before was now accepted as a matter of course.\
\
Having disposed of the tariff, Congress took up the old and vexatious\
currency question and offered a new solution in the form of the federal\
reserve law of December, 1913. This measure, one of the most interesting\
in the history of federal finance, embraced four leading features. In\
the first place, it continued the prohibition on the issuance of notes\
by state banks and provided for a national currency. In the second\
place, it put the new banking system under the control of a federal\
reserve board composed entirely of government officials. To prevent the\
growth of a "central money power," it provided, in the third place, for\
the creation of twelve federal reserve banks, one in each of twelve\
great districts into which the country is divided. All local national\
banks were required and certain other banks permitted to become members\
of the new system and share in its control. Finally, with a view to\
expanding the currency, a step which the Democrats had long urged upon\
the country, the issuance of paper money, under definite safeguards, was\
authorized.\
\
Mindful of the agricultural interest, ever dear to the heart of\
Jefferson's followers, the Democrats supplemented the reserve law by the\
Farm Loan Act of 1916, creating federal agencies to lend money on farm\
mortgages at moderate rates of interest. Within a year $20,000,000 had\
been lent to farmers, the heaviest borrowing being in nine Western and\
Southern states, with Texas in the lead.\
\
=Anti-trust Legislation.=--The tariff and currency laws were followed by\
three significant measures relative to trusts. Rejecting utterly the\
Progressive doctrine of government regulation, President Wilson\
announced that it was the purpose of the Democrats "to destroy monopoly\
and maintain competition as the only effective instrument of business\
liberty." The first step in this direction, the Clayton Anti-trust Act,\
carried into great detail the Sherman law of 1890 forbidding and\
penalizing combinations in restraint of interstate and foreign trade. In\
every line it revealed a determined effort to tear apart the great\
trusts and to put all business on a competitive basis. Its terms were\
reinforced in the same year by a law creating a Federal Trade Commission\
empowered to inquire into the methods of corporations and lodge\
complaints against concerns "using any unfair method of competition." In\
only one respect was the severity of the Democratic policy relaxed. An\
act of 1918 provided that the Sherman law should not apply to companies\
engaged in export trade, the purpose being to encourage large\
corporations to enter foreign commerce.\
\
The effect of this whole body of anti-trust legislation, in spite of\
much labor on it, remained problematical. Very few combinations were\
dissolved as a result of it. Startling investigations were made into\
alleged abuses on the part of trusts; but it could hardly be said that\
huge business concerns had lost any of their predominance in American\
industry.\
\
=Labor Legislation.=--By no mere coincidence, the Clayton Anti-trust law\
of 1914 made many concessions to organized labor. It declared that "the\
labor of a human being is not a commodity or an article of commerce,"\
and it exempted unions from prosecution as "combinations in restraint of\
trade." It likewise defined and limited the uses which the federal\
courts might make of injunctions in labor disputes and guaranteed trial\
by jury to those guilty of disobedience (see p. 581).\
\
The Clayton law was followed the next year by the Seamen's Act giving\
greater liberty of contract to American sailors and requiring an\
improvement of living conditions on shipboard. This was such a drastic\
law that shipowners declared themselves unable to meet foreign\
competition under its terms, owing to the low labor standards of other\
countries.\
\
Still more extraordinary than the Seamen's Act was the Adamson law of\
1916 fixing a standard eight-hour work-day for trainmen on railroads--a\
measure wrung from Congress under a threat of a great strike by the four\
Railway Brotherhoods. This act, viewed by union leaders as a triumph,\
called forth a bitter denunciation of "trade union domination," but it\
was easier to criticize than to find another solution of the problem.\
\
Three other laws enacted during President Wilson's administration were\
popular in the labor world. One of them provided compensation for\
federal employees injured in the discharge of their duties. Another\
prohibited the labor of children under a certain age in the industries\
of the nation. A third prescribed for coal miners in Alaska an\
eight-hour day and modern safeguards for life and health. There were\
positive proofs that organized labor had obtained a large share of power\
in the councils of the country.\
\
=Federal and State Relations.=--If the interference of the government\
with business and labor represented a departure from the old idea of\
"the less government the better," what can be said of a large body of\
laws affecting the rights of states? The prohibition of child labor\
everywhere was one indication of the new tendency. Mr. Wilson had once\
declared such legislation unconstitutional; the Supreme Court declared\
it unconstitutional; but Congress, undaunted, carried it into effect\
under the guise of a tax on goods made by children below the age limit.\
There were other indications of the drift. Large sums of money were\
appropriated by Congress in 1916 to assist the states in building and\
maintaining highways. The same year the Farm Loan Act projected the\
federal government into the sphere of local money lending. In 1917\
millions of dollars were granted to states in aid of vocational\
education, incidentally imposing uniform standards throughout the\
country. Evidently the government was no longer limited to the duties of\
the policeman.\
\
=The Prohibition Amendment.=--A still more significant form of\
intervention in state affairs was the passage, in December, 1917, of an\
amendment to the federal Constitution establishing national prohibition\
of the manufacture and sale of intoxicating liquors as beverages. This\
was the climax of a historical movement extending over half a century.\
In 1872, a National Prohibition party, launched three years before,\
nominated its first presidential candidate and inaugurated a campaign of\
agitation. Though its vote was never large, the cause for which it\
stood found increasing favor among the people. State after state by\
popular referendum abolished the liquor traffic within its borders. By\
1917 at least thirty-two of the forty-eight were "dry." When the federal\
amendment was submitted for approval, the ratification was surprisingly\
swift. In a little more than a year, namely, on January 16, 1919, it was\
proclaimed. Twelve months later the amendment went into effect.\
\
\
COLONIAL AND FOREIGN POLICIES\
\
=The Philippines and Porto Rico.=--Independence for the Philippines and\
larger self-government for Porto Rico had been among the policies of the\
Democratic party since the campaign of 1900. President Wilson in his\
annual messages urged upon Congress more autonomy for the Filipinos and\
a definite promise of final independence. The result was the Jones\
Organic Act for the Philippines passed in 1916. This measure provided\
that the upper as well as the lower house of the Philippine legislature\
should be elected by popular vote, and declared it to be the intention\
of the United States to grant independence "as soon as a stable\
government can be established." This, said President Wilson on signing\
the bill, is "a very satisfactory advance in our policy of extending to\
them self-government and control of their own affairs." The following\
year Congress, yielding to President Wilson's insistence, passed a new\
\
organic act for Porto Rico, making both houses of the legislature\
elective and conferring American citizenship upon the inhabitants of the\
island.\
\
[Illustration: THE CARIBBEAN REGION]\
\
=American Power in the Caribbean.=--While extending more self-government\
to its dominions, the United States enlarged its sphere of influence in\
the Caribbean. The supervision of finances in Santo Domingo, inaugurated\
in Roosevelt's administration, was transformed into a protectorate under\
Wilson. In 1914 dissensions in the republic led to the landing of\
American marines to "supervise" the elections. Two years later, an\
officer in the American navy, with authority from Washington, placed\
the entire republic "in a state of military occupation." He proceeded to\
suspend the government and laws of the country, exile the president,\
suppress the congress, and substitute American military authority. In\
1919 a consulting board of four prominent Dominicans was appointed to\
aid the American military governor; but it resigned the next year after\
making a plea for the restoration of independence to the republic. For\
all practical purposes, it seemed, the sovereignty of Santo Domingo had\
been transferred to the United States.\
\
In the neighboring republic of Haiti, a similar state of affairs\
existed. In the summer of 1915 a revolution broke out there--one of a\
long series beginning in 1804--and our marines were landed to restore\
order. Elections were held under the supervision of American officers,\
and a treaty was drawn up placing the management of Haitian finances and\
the local constabulary under American authority. In taking this action,\
our Secretary of State was careful to announce: "The United States\
government has no purpose of aggression and is entirely disinterested in\
promoting this protectorate." Still it must be said that there were\
vigorous protests on the part of natives and American citizens against\
the conduct of our agents in the island. In 1921 President Wilson was\
considering withdrawal.\
\
In line with American policy in the West Indian waters was the purchase\
in 1917 of the Danish Islands just off the coast of Porto Rico. The\
strategic position of the islands, especially in relation to Haiti and\
Porto Rico, made them an object of American concern as early as 1867,\
when a treaty of purchase was negotiated only to be rejected by the\
Senate of the United States. In 1902 a second arrangement was made, but\
this time it was defeated by the upper house of the Danish parliament.\
The third treaty brought an end to fifty years of bargaining and the\
Stars and Stripes were raised over St. Croix, St. Thomas, St. John, and\
numerous minor islands scattered about in the neighborhood. "It would be\
suicidal," commented a New York newspaper, "for America, on the\
threshold of a great commercial expansion in South America, to suffer a\
Heligoland, or a Gibraltar, or an Aden to be erected by her rivals at\
the mouth of her Suez." On the mainland American power was strengthened\
by the establishment of a protectorate over Nicaragua in 1916.\
\
=Mexican Relations.=--The extension of American enterprise southward\
into Latin America, of which the operations in the Caribbean regions\
were merely one phase, naturally carried Americans into Mexico to\
develop the natural resources of that country. Under the iron rule of\
General Porfirio Diaz, established in 1876 and maintained with only a\
short break until 1911, Mexico had become increasingly attractive to our\
business men. On the invitation of President Diaz, they had invested\
huge sums in Mexican lands, oil fields, and mines, and had laid the\
foundations of a new industrial order. The severe regime instituted by\
Diaz, however, stirred popular discontent. The peons, or serfs, demanded\
the break-up of the great estates, some of which had come down from the\
days of Cortez. Their clamor for "the restoration of the land to the\
people could not be silenced." In 1911 Diaz was forced to resign and\
left the country.\
\
Mexico now slid down the path to disorder. Revolutions and civil\
commotions followed in swift succession. A liberal president, Madero,\
installed as the successor to Diaz, was deposed in 1913 and brutally\
murdered. Huerta, a military adventurer, hailed for a time as another\
"strong man," succeeded Madero whose murder he was accused of\
instigating. Although Great Britain and nearly all the powers of Europe\
accepted the new government as lawful, the United States steadily\
withheld recognition. In the meantime Mexico was torn by insurrections\
under the leadership of Carranza, a friend of Madero, Villa, a bandit of\
generous pretensions, and Zapata, a radical leader of the peons. Without\
the support of the United States, Huerta was doomed.\
\
In the summer of 1914, the dictator resigned and fled from the capital,\
leaving the field to Carranza. For six years the new president,\
recognized by the United States, held a precarious position which he\
vigorously strove to strengthen against various revolutionary movements.\
At length in 1920, he too was deposed and murdered, and another military\
chieftain, Obregon, installed in power.\
\
These events right at our door could not fail to involve the government\
of the United States. In the disorders many American citizens lost their\
lives. American property was destroyed and land owned by Americans was\
confiscated. A new Mexican constitution, in effect nationalizing the\
natural resources of the country, struck at the rights of foreign\
investors. Moreover the Mexican border was in constant turmoil. Even in\
the last days of his administration, Mr. Taft felt compelled to issue a\
solemn warning to the Mexican government protesting against the\
violation of American rights.\
\
President Wilson, soon after his inauguration, sent a commissioner to\
Mexico to inquire into the situation. Although he declared a general\
policy of "watchful waiting," he twice came to blows with Mexican\
forces. In 1914 some American sailors at Tampico were arrested by a\
Mexican officer; the Mexican government, although it immediately\
released the men, refused to make the required apology for the incident.\
As a result President Wilson ordered the landing of American forces at\
Vera Cruz and the occupation of the city. A clash of arms followed in\
which several Americans were killed. War seemed inevitable, but at this\
juncture the governments of Argentina, Brazil, and Chile tendered their\
good offices as mediators. After a few weeks of negotiation, during\
which Huerta was forced out of power, American forces were withdrawn\
from Vera Cruz and the incident closed.\
\
In 1916 a second break in amicable relations occurred. In the spring of\
that year a band of Villa's men raided the town of Columbus, New Mexico,\
killing several citizens and committing robberies. A punitive expedition\
under the command of General Pershing was quickly sent out to capture\
the offenders. Against the protests of President Carranza, American\
forces penetrated deeply into Mexico without effecting the object of\
the undertaking. This operation lasted until January, 1917, when the\
imminence of war with Germany led to the withdrawal of the American\
soldiers. Friendly relations were resumed with the Mexican government\
and the policy of "watchful waiting" was continued.\
\
\
THE UNITED STATES AND THE EUROPEAN WAR\
\
=The Outbreak of the War.=--In the opening days of August, 1914, the\
age-long jealousies of European nations, sharpened by new imperial\
ambitions, broke out in another general conflict such as had shaken the\
world in the days of Napoleon. On June 28, the heir to the\
Austro-Hungarian throne was assassinated at Serajevo, the capital of\
Bosnia, an Austrian province occupied mainly by Serbs. With a view to\
stopping Serbian agitation for independence, Austria-Hungary laid the\
blame for this incident on the government of Serbia and made humiliating\
demands on that country. Germany at once proposed that the issue should\
be regarded as "an affair which should be settled solely between\
Austria-Hungary and Serbia"; meaning that the small nation should be\
left to the tender mercies of a great power. Russia refused to take this\
view. Great Britain proposed a settlement by mediation. Germany backed\
up Austria to the limit. To use the language of the German authorities:\
"We were perfectly aware that a possible warlike attitude of\
Austria-Hungary against Serbia might bring Russia upon the field and\
that it might therefore involve us in a war, in accordance with our\
duties as allies. We could not, however, in these vital interests of\
Austria-Hungary which were at stake, advise our ally to take a yielding\
attitude not compatible with his dignity nor deny him our assistance."\
That made the war inevitable.\
\
Every day of the fateful August, 1914, was crowded with momentous\
events. On the 1st, Germany declared war on Russia. On the 2d, the\
Germans invaded the little duchy of Luxemburg and notified the King of\
Belgium that they were preparing to violate the neutrality of his realm\
on their way to Paris. On the same day, Great Britain, anxiously\
besought by the French government, promised the aid of the British navy\
if German warships made hostile demonstrations in the Channel. August\
3d, the German government declared war on France. The following day,\
Great Britain demanded of Germany respect for Belgian neutrality and,\
failing to receive the guarantee, broke off diplomatic relations. On the\
5th, the British prime minister announced that war had opened between\
England and Germany. The storm now broke in all its pitiless fury.\
\
=The State of American Opinion.=--Although President Wilson promptly\
proclaimed the neutrality of the United States, the sympathies of a\
large majority of the American people were without doubt on the side of\
Great Britain and France. To them the invasion of the little kingdom of\
Belgium and the horrors that accompanied German occupation were odious\
in the extreme. Moreover, they regarded the German imperial government\
as an autocratic power wielded in the interest of an ambitious military\
party. The Kaiser, William II, and the Crown Prince were the symbols of\
royal arrogance. On the other hand, many Americans of German descent, in\
memory of their ties with the Fatherland, openly sympathized with the\
Central Powers; and many Americans of Irish descent, recalling their\
long and bitter struggle for home rule in Ireland, would have regarded\
British defeat as a merited redress of ancient grievances.\
\
Extremely sensitive to American opinion, but ill informed about it, the\
German government soon began systematic efforts to present its cause to\
the people of the United States in the most favorable light possible.\
Dr. Bernhard Dernburg, the former colonial secretary of the German\
empire, was sent to America as a special agent. For months he filled the\
newspapers, magazines, and periodicals with interviews, articles, and\
notes on the justice of the Teutonic cause. From a press bureau in New\
York flowed a stream of pamphlets, leaflets, and cartoons. A magazine,\
"The Fatherland," was founded to secure "fair play for Germany and\
Austria." Several professors in American universities, who had received\
their training in Germany, took up the pen in defense of the Central\
Empires. The German language press, without exception it seems, the\
National German Alliance, minor German societies, and Lutheran churches\
came to the support of the German cause. Even the English language\
papers, though generally favorable to the Entente Allies, opened their\
columns in the interest of equal justice to the spokesmen for all the\
contending powers of Europe.\
\
Before two weeks had elapsed the controversy had become so intense that\
President Wilson (August 18, 1914) was moved to caution his countrymen\
against falling into angry disputes. "Every man," he said, "who really\
loves America will act and speak in the true spirit of neutrality which\
is the spirit of impartiality and fairness and friendliness to all\
concerned.... We must be impartial in thought as well as in action, must\
put a curb upon our sentiments as well as upon every transaction that\
might be construed as a preference of one party to the struggle before\
another."\
\
=The Clash over American Trade.=--As in the time of the Napoleonic wars,\
the conflict in Europe raised fundamental questions respecting rights of\
Americans trading with countries at peace as well as those at war. On\
this point there existed on August 1, 1914, a fairly definite body of\
principles by which nations were bound. Among them the following were of\
vital significance. In the first place, it was recognized that an enemy\
merchant ship caught on the high seas was a legitimate prize of war\
which might be seized and confiscated. In the second place, it was\
agreed that "contraband of war" found on an enemy or neutral ship was a\
lawful prize; any ship suspected of carrying it was liable to search and\
if caught with forbidden goods was subject to seizure. In the third\
place, international law prescribed that a peaceful merchant ship,\
whether belonging to an enemy or to a neutral country, should not be\
destroyed or sunk without provision for the safety of crew and\
passengers. In the fourth place, it was understood that a belligerent\
had the right, if it could, to blockade the ports of an enemy and\
prevent the ingress and egress of all ships; but such a blockade, to be\
lawful, had to be effective.\
\
These general principles left undetermined two important matters: "What\
is an effective blockade?" and "What is contraband of war?" The task of\
answering these questions fell to Great Britain as mistress of the seas.\
Although the German submarines made it impossible for her battleships to\
maintain a continuous patrol of the waters in front of blockaded ports,\
\
she declared the blockade to be none the less "effective" because her\
navy was supreme. As to contraband of war Great Britain put such a broad\
interpretation upon the term as to include nearly every important\
article of commerce. Early in 1915 she declared even cargoes of grain\
and flour to be contraband, defending the action on the ground that the\
German government had recently taken possession of all domestic stocks\
of corn, wheat, and flour.\
\
A new question arose in connection with American trade with the neutral\
countries surrounding Germany. Great Britain early began to intercept\
ships carrying oil, gasoline, and copper--all war materials of prime\
importance--on the ground that they either were destined ultimately to\
Germany or would release goods for sale to Germans. On November 2, 1914,\
the English government announced that the Germans wore sowing mines in\
open waters and that therefore the whole of the North Sea was a military\
zone. Ships bound for Denmark, Norway, and Sweden were ordered to come\
by the English Channel for inspection and sailing directions. In effect,\
Americans were now licensed by Great Britain to trade in certain\
commodities and in certain amounts with neutral countries.\
\
Against these extraordinary measures, the State Department at Washington\
lodged pointed objections, saying: "This government is reluctantly\
forced to the conclusion that the present policy of His Majesty's\
government toward neutral ships and cargoes exceeds the manifest\
necessity of a belligerent and constitutes restrictions upon the rights\
of American citizens on the high seas, which are not justified by the\
rules of international law or required under the principle of\
self-preservation."\
\
=Germany Begins the Submarine Campaign.=--Germany now announced that, on\
and after February 18, 1915, the whole of the English Channel and the\
waters around Great Britain would be deemed a war zone and that every\
enemy ship found therein would be destroyed. The German decree added\
that, as the British admiralty had ordered the use of neutral flags by\
English ships in time of distress, neutral vessels would be in danger of\
destruction if found in the forbidden area. It was clear that Germany\
intended to employ submarines to destroy shipping. A new factor was thus\
introduced into naval warfare, one not provided for in the accepted laws\
of war. A warship overhauling a merchant vessel could easily take its\
crew and passengers on board for safe keeping as prescribed by\
international law; but a submarine ordinarily could do nothing of the\
sort. Of necessity the lives and the ships of neutrals, as well as of\
belligerents, were put in mortal peril. This amazing conduct Germany\
justified on the ground that it was mere retaliation against Great\
Britain for her violations of international law.\
\
The response of the United States to the ominous German order was swift\
and direct. On February 10, 1915, it warned Germany that if her\
commanders destroyed American lives and ships in obedience to that\
decree, the action would "be very hard indeed to reconcile with the\
friendly relations happily subsisting between the two governments." The\
American note added that the German imperial government would be held to\
"strict accountability" and all necessary steps would be taken to\
safeguard American lives and American rights. This was firm and clear\
language, but the only response which it evoked from Germany was a\
suggestion that, if Great Britain would allow food supplies to pass\
through the blockade, the submarine campaign would be dropped.\
\
=Violations of American Rights.=--Meanwhile Germany continued to ravage\
shipping on the high seas. On January 28, a German raider sank the\
American ship, _William P. Frye_, in the South Atlantic; on March 28, a\
British ship, the _Falaba_, was sunk by a submarine and many on board,\
including an American citizen, were killed; and on April 28, a German\
airplane dropped bombs on the American steamer _Cushing_. On the morning\
of May 1, 1915, Americans were astounded to see in the newspapers an\
advertisement, signed by the German Imperial Embassy, warning travelers\
of the dangers in the war zone and notifying them that any who ventured\
on British ships into that area did so at their own risk. On that day,\
the _Lusitania_, a British steamer, sailed from New York for Liverpool.\
On May 7, without warning, the ship was struck by two torpedoes and in a\
few minutes went down by the bow, carrying to death 1153 persons\
including 114 American men, women, and children. A cry of horror ran\
through the country. The German papers in America and a few American\
people argued that American citizens had been duly warned of the danger\
and had deliberately taken their lives into their own hands; but the\
terrible deed was almost universally condemned by public opinion.\
\
=The _Lusitania_ Notes.=--On May 14, the Department of State at\
Washington made public the first of three famous notes on the\
_Lusitania_ case. It solemnly informed the German government that "no\
warning that an unlawful and inhumane act will be committed can possibly\
be accepted as an excuse or palliation for that act or as an abatement\
of the responsibility for its commission." It called upon the German\
government to disavow the act, make reparation as far as possible, and\
take steps to prevent "the recurrence of anything so obviously\
subversive of the principles of warfare." The note closed with a clear\
caution to Germany that the government of the United States would not\
"omit any word or any act necessary to the performance of its sacred\
duty of maintaining the rights of the United States and its citizens and\
of safeguarding their free exercise and enjoyment." The die was cast;\
but Germany in reply merely temporized.\
\
In a second note, made public on June 11, the position of the United\
States was again affirmed. William Jennings Bryan, the Secretary of\
State, had resigned because the drift of President Wilson's policy was\
not toward mediation but the strict maintenance of American rights, if\
need be, by force of arms. The German reply was still evasive and German\
naval commanders continued their course of sinking merchant ships. In a\
third and final note of July 21, 1915, President Wilson made it clear to\
Germany that he meant what he said when he wrote that he would maintain\
the rights of American citizens. Finally after much discussion and\
shifting about, the German ambassador on September 1, 1915, sent a brief\
note to the Secretary of State: "Liners will not be sunk by our\
submarines without warning and without safety of the lives of\
non-combatants, provided the liners do not try to escape or offer\
resistance." Editorially, the New York _Times_ declared: "It is a\
triumph not only of diplomacy but of reason, of humanity, of justice,\
and of truth." The Secretary of State saw in it "a recognition of the\
fundamental principles for which we have contended."\
\
=The Presidential Election of 1916.=--In the midst of this crisis came\
the presidential campaign. On the Republican side everything seemed to\
depend upon the action of the Progressives. If the breach created in\
1912 could be closed, victory was possible; if not, defeat was certain.\
A promise of unity lay in the fact that the conventions of the\
Republicans and Progressives were held simultaneously in Chicago. The\
friends of Roosevelt hoped that both parties would select him as their\
candidate; but this hope was not realized. The Republicans chose, and\
the Progressives accepted, Charles E. Hughes, an associate justice of\
the federal Supreme Court who, as governor of New York, had won a\
national reputation by waging war on "machine politicians."\
\
In the face of the clamor for expressions of sympathy with one or the\
other of the contending powers of Europe, the Republicans chose a middle\
course, declaring that they would uphold all American rights "at home\
and abroad, by land and by sea." This sentiment Mr. Hughes echoed in his\
acceptance speech. By some it was interpreted to mean a firmer policy in\
dealing with Great Britain; by others, a more vigorous handling of the\
submarine menace. The Democrats, on their side, renominated President\
Wilson by acclamation, reviewed with pride the legislative achievements\
of the party, and commended "the splendid diplomatic victories of our\
great President who has preserved the vital interests of our government\
and its citizens and kept us out of war."\
\
In the election which ensued President Wilson's popular vote exceeded\
that cast for Mr. Hughes by more than half a million, while his\
electoral vote stood 277 to 254. The result was regarded, and not\
without warrant, as a great personal triumph for the President. He had\
received the largest vote yet cast for a presidential candidate. The\
Progressive party practically disappeared, and the Socialists suffered a\
severe set-back, falling far behind the vote of 1912.\
\
=President Wilson Urges Peace upon the Warring Nations.=--Apparently\
convinced that his pacific policies had been profoundly approved by his\
countrymen, President Wilson, soon after the election, addressed "peace\
notes" to the European belligerents. On December 16, the German Emperor\
proposed to the Allied Powers that they enter into peace negotiations, a\
suggestion that was treated as a mere political maneuver by the opposing\
governments. Two days later President Wilson sent a note to the warring\
nations asking them to avow "the terms upon which war might be\
concluded." To these notes the Central Powers replied that they were\
ready to meet their antagonists in a peace conference; and Allied Powers\
answered by presenting certain conditions precedent to a satisfactory\
settlement. On January 22, 1917, President Wilson in an address before\
the Senate, declared it to be a duty of the United States to take part\
in the establishment of a stable peace on the basis of certain\
principles. These were, in short: "peace without victory"; the right of\
nationalities to freedom and self-government; the independence of\
Poland; freedom of the seas; the reduction of armaments; and the\
abolition of entangling alliances. The whole world was discussing the\
President's remarkable message, when it was dumbfounded to hear, on\
January 31, that the German ambassador at Washington had announced the\
official renewal of ruthless submarine warfare.\
\
\
THE UNITED STATES AT WAR\
\
=Steps toward War.=--Three days after the receipt of the news that the\
German government intended to return to its former submarine policy,\
President Wilson severed diplomatic relations with the German empire. At\
the same time he explained to Congress that he desired no conflict with\
Germany and would await an "overt act" before taking further steps to\
preserve American rights. "God grant," he concluded, "that we may not be\
challenged to defend them by acts of willful injustice on the part of\
the government of Germany." Yet the challenge came. Between February 26\
and April 2, six American merchant vessels were torpedoed, in most cases\
without any warning and without regard to the loss of American lives.\
President Wilson therefore called upon Congress to answer the German\
menace. The reply of Congress on April 6 was a resolution, passed with\
only a few dissenting votes, declaring the existence of a state of war\
with Germany. Austria-Hungary at once severed diplomatic relations with\
the United States; but it was not until December 7 that Congress, acting\
on the President's advice, declared war also on that "vassal of the\
German government."\
\
=American War Aims.=--In many addresses at the beginning and during the\
course of the war, President Wilson stated the purposes which actuated\
our government in taking up arms. He first made it clear that it was a\
war of self-defense. "The military masters of Germany," he exclaimed,\
"denied us the right to be neutral." Proof of that lay on every hand.\
Agents of the German imperial government had destroyed American lives\
and American property on the high seas. They had filled our communities\
with spies. They had planted bombs in ships and munition works. They had\
fomented divisions among American citizens.\
\
Though assailed in many ways and compelled to resort to war, the United\
States sought no material rewards. "The world must be made safe for\
democracy. Its peace must be planted upon the tested foundations of\
political liberty. We have no selfish ends to serve. We desire no\
conquest, no dominion. We seek no indemnities for ourselves."\
\
In a very remarkable message read to Congress on January 8, 1918,\
President Wilson laid down his famous "fourteen points" summarizing the\
ideals for which we were fighting. They included open treaties of peace,\
openly arrived at; absolute freedom of navigation upon the seas; the\
removal, as far as possible, of trade barriers among nations; reduction\
of armaments; adjustment of colonial claims in the interest of the\
populations concerned; fair and friendly treatment of Russia; the\
restoration of Belgium; righting the wrong done to France in 1871 in the\
matter of Alsace-Lorraine; adjustment of Italian frontiers along the\
lines of nationality; more liberty for the peoples of Austria-Hungary;\
the restoration of Serbia and Rumania; the readjustment of the Turkish\
Empire; an independent Poland; and an association of nations to afford\
mutual guarantees to all states great and small. On a later occasion\
President Wilson elaborated the last point, namely, the formation of a\
league of nations to guarantee peace and establish justice among the\
powers of the world. Democracy, the right of nations to determine their\
own fate, a covenant of enduring peace--these were the ideals for which\
the American people were to pour out their blood and treasure.\
\
=The Selective Draft.=--The World War became a war of nations. The\
powers against which we were arrayed had every able-bodied man in\
service and all their resources, human and material, thrown into the\
scale. For this reason, President Wilson summoned the whole people of\
the United States to make every sacrifice necessary for victory.\
Congress by law decreed that the national army should be chosen from all\
male citizens and males not enemy aliens who had declared their\
intention of becoming citizens. By the first act of May 18, 1917, it\
fixed the age limits at twenty-one to thirty-one inclusive. Later, in\
August, 1918, it extended them to eighteen and forty-five. From the men\
of the first group so enrolled were chosen by lot the soldiers for the\
World War who, with the regular army and the national guard, formed the\
American Expeditionary Force upholding the American cause on the\
battlefields of Europe. "The whole nation," said the President, "must be\
a team in which each man shall play the part for which he is best\
fitted."\
\
=Liberty Loans and Taxes.=--In order that the military and naval forces\
should be stinted in no respect, the nation was called upon to place its\
financial resources at the service of the government. Some urged the\
"conscription of wealth as well as men," meaning the support of the war\
out of taxes upon great fortunes; but more conservative counsels\
prevailed. Four great Liberty Loans were floated, all the agencies of\
modern publicity being employed to enlist popular interest. The first\
loan had four and a half million subscribers; the fourth more than\
twenty million. Combined with loans were heavy taxes. A progressive tax\
was laid upon incomes beginning with four per cent on incomes in the\
lower ranges and rising to sixty-three per cent of that part of any\
income above $2,000,000. A progressive tax was levied upon inheritances.\
An excess profits tax was laid upon all corporations and partnerships,\
rising in amount to sixty per cent of the net income in excess of\
thirty-three per cent on the invested capital. "This," said a\
distinguished economist, "is the high-water mark in the history of\
taxation. Never before in the annals of civilization has an attempt been\
made to take as much as two-thirds of a man's income by taxation."\
\
=Mobilizing Material Resources.=--No stone was left unturned to provide\
the arms, munitions, supplies, and transportation required in the\
gigantic undertaking. Between the declaration of war and the armistice,\
Congress enacted law after law relative to food supplies, raw materials,\
railways, mines, ships, forests, and industrial enterprises. No power\
over the lives and property of citizens, deemed necessary to the\
prosecution of the armed conflict, was withheld from the government. The\
farmer's wheat, the housewife's sugar, coal at the mines, labor in the\
factories, ships at the wharves, trade with friendly countries, the\
railways, banks, stores, private fortunes--all were mobilized and laid\
under whatever obligations the government deemed imperative. Never was a\
nation more completely devoted to a single cause.\
\
A law of August 10, 1917, gave the President power to fix the prices of\
wheat and coal and to take almost any steps necessary to prevent\
monopoly and excessive prices. By a series of measures, enlarging the\
principles of the shipping act of 1916, ships and shipyards were brought\
under public control and the government was empowered to embark upon a\
great ship-building program. In December, 1917, the government assumed\
for the period of the war the operation of the railways under a\
presidential proclamation which was elaborated in March, 1918, by act of\
Congress. In the summer of 1918 the express, telephone, and telegraph\
business of the entire country passed under government control. By war\
risk insurance acts allowances were made for the families of enlisted\
men, compensation for injuries was provided, death benefits were\
instituted, and a system of national insurance was established in the\
interest of the men in service. Never before in the history of the\
country had the government taken such a wise and humane view of its\
obligations to those who served on the field of battle or on the seas.\
\
=The Espionage and Sedition Acts.=--By the Espionage law of June 15,\
1917, and the amending law, known as the Sedition act, passed in May of\
the following year, the government was given a drastic power over the\
expression of opinion. The first measure penalized those who conveyed\
information to a foreign country to be used to the injury of the United\
States; those who made false statements designed to interfere with the\
military or naval forces of the United States; those who attempted to\
stir up insubordination or disloyalty in the army and navy; and those\
who willfully obstructed enlistment. The Sedition act was still more\
severe and sweeping in its terms. It imposed heavy penalties upon any\
person who used "abusive language about the government or institutions\
of the country." It authorized the dismissal of any officer of the\
government who committed "disloyal acts" or uttered "disloyal language,"\
and empowered the Postmaster General to close the mails to persons\
violating the law. This measure, prepared by the Department of Justice,\
encountered vigorous opposition in the Senate, where twenty-four\
Republicans and two Democrats voted against it. Senator Johnson of\
California denounced it as a law "to suppress the freedom of the press\
in the United States and to prevent any man, no matter who he is, from\
expressing legitimate criticism concerning the present government." The\
constitutionality of the acts was attacked; but they were sustained by\
the Supreme Court and stringently enforced.\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
THE LAUNCHING OF A SHIP AT THE GREAT NAVAL YARDS, NEWARK, N.J.]\
\
=Labor and the War.=--In view of the restlessness of European labor\
during the war and especially the proletarian revolution in Russia in\
November, 1917, some anxiety was early expressed as to the stand which\
organized labor might take in the United States. It was, however, soon\
dispelled. Samuel Gompers, speaking for the American Federation of\
Labor, declared that "this is labor's war," and pledged the united\
support of all the unions. There was some dissent. The Socialist party\
denounced the war as a capitalist quarrel; but all the protests combined\
were too slight to have much effect. American labor leaders were sent to\
Europe to strengthen the wavering ranks of trade unionists in war-worn\
England, France, and Italy. Labor was given representation on the\
important boards and commissions dealing with industrial questions.\
Trade union standards were accepted by the government and generally\
applied in industry. The Department of Labor became one of the powerful\
war centers of the nation. In a memorable address to the American\
Federation of Labor, President Wilson assured the trade unionists that\
labor conditions should not be made unduly onerous by the war and\
received in return a pledge of loyalty from the Federation. Recognition\
of labor's contribution to winning the war was embodied in the treaty of\
peace, which provided for a permanent international organization to\
promote the world-wide effort of labor to improve social conditions.\
"The league of nations has for its object the establishment of universal\
peace," runs the preamble to the labor section of the treaty, "and such\
a peace can be established only if it is based upon social justice....\
The failure of any nation to adopt humane conditions of labor is an\
obstacle in the way of other nations which desire to improve the\
conditions in their own countries."\
\
=The American Navy in the War.=--As soon as Congress declared war the\
fleet was mobilized, American ports were thrown open to the warships of\
the Allies, immediate provision was made for increasing the number of\
men and ships, and a contingent of war vessels was sent to cooperate\
with the British and French in their life-and-death contest with\
submarines. Special effort was made to stimulate the production of\
"submarine chasers" and "scout cruisers" to be sent to the danger zone.\
Convoys were provided to accompany the transports conveying soldiers to\
France. Before the end of the war more than three hundred American\
vessels and 75,000 officers and men were operating in European waters.\
Though the German fleet failed to come out and challenge the sea power\
of the Allies, the battleships of the United States were always ready to\
do their full duty in such an event. As things turned out, the service\
of the American navy was limited mainly to helping in the campaign that\
wore down the submarine menace to Allied shipping.\
\
=The War in France.=--Owing to the peculiar character of the warfare in\
France, it required a longer time for American military forces to get\
into action; but there was no unnecessary delay. Soon after the\
declaration of war, steps were taken to give military assistance to the\
Allies. The regular army was enlarged and the troops of the national\
guard were brought into national service. On June 13, General John J.\
Pershing, chosen head of the American Expeditionary Forces, reached\
Paris and began preparations for the arrival of our troops. In June, the\
vanguard of the army reached France. A slow and steady stream followed.\
As soon as the men enrolled under the draft were ready, it became a\
flood. During the period of the war the army was enlarged from about\
190,000 men to 3,665,000, of whom more than 2,000,000 were in France\
when the armistice was signed.\
\
Although American troops did not take part on a large scale until the\
last phase of the war in 1918, several battalions of infantry were in\
the trenches by October, 1917, and had their first severe encounter with\
the Germans early in November. In January, 1918, they took over a part\
of the front line as an American sector. In March, General Pershing\
placed our forces at the disposal of General Foch, commander-in-chief of\
the Allied armies. The first division, which entered the Montdidier\
salient in April, soon was engaged with the enemy, "taking with splendid\
dash the town of Cantigny and all other objectives, which were organized\
and held steadfastly against vicious counter attacks and galling\
artillery fire."\
\
[Illustration: _Copyright by Underwood and Underwood, N.Y._\
\
TROOPS RETURNING FROM FRANCE]\
\
When the Germans launched their grand drives toward the Marne and Paris,\
in June and July, 1918, every available man was placed at General Foch's\
command. At Belleau Wood, at Chateau-Thierry, and other points along the\
deep salient made by the Germans into the French lines, American\
soldiers distinguished themselves by heroic action. They also played an\
important role in the counter attack that "smashed" the salient and\
drove the Germans back.\
\
In September, American troops, with French aid, "wiped out" the German\
salient at St. Mihiel. By this time General Pershing was ready for the\
great American drive to the northeast in the Argonne forest, while he\
also cooperated with the British in the assault on the Hindenburg line.\
In the Meuse-Argonne battle, our soldiers encountered some of the most\
severe fighting of the war and pressed forward steadily against the most\
stubborn resistance from the enemy. On the 6th of November, reported\
General Pershing, "a division of the first corps reached a point on the\
Meuse opposite Sedan, twenty-five miles from our line of departure. The\
strategical goal which was our highest hope was gained. We had cut the\
enemy's main line of communications and nothing but a surrender or an\
armistice could save his army from complete disaster." Five days later\
the end came. On the morning of November 11, the order to cease firing\
went into effect. The German army was in rapid retreat and\
demoralization had begun. The Kaiser had abdicated and fled into\
Holland. The Hohenzollern dreams of empire were shattered. In the\
fifty-second month, the World War, involving nearly every civilized\
nation on the globe, was brought to a close. More than 75,000 American\
soldiers and sailors had given their lives. More than 250,000 had been\
wounded or were missing or in German prison camps.\
\
[Illustration: WESTERN BATTLE LINES OF THE VARIOUS YEARS OF THE\
WORLD WAR]\
\
\
THE SETTLEMENT AT PARIS\
\
=The Peace Conference.=--On January 18, 1919, a conference of the Allied\
and Associated Powers assembled to pronounce judgment upon the German\
empire and its defeated satellites: Austria-Hungary, Bulgaria, and\
Turkey. It was a moving spectacle. Seventy-two delegates spoke for\
thirty-two states. The United States, Great Britain, France, Italy, and\
Japan had five delegates each. Belgium, Brazil, and Serbia were each\
assigned three. Canada, Australia, South Africa, India, China, Greece,\
Hedjaz, Poland, Portugal, Rumania, Siam, and Czechoslovakia were\
allotted two apiece. The remaining states of New Zealand, Bolivia, Cuba,\
Ecuador, Guatemala, Haiti, Honduras, Liberia, Nicaragua, Panama, Peru,\
and Uruguay each had one delegate. President Wilson spoke in person for\
the United States. England, France, and Italy were represented by their\
premiers: David Lloyd George, Georges Clemenceau, and Vittorio Orlando.\
\
[Illustration: PREMIERS LLOYD GEORGE, ORLANDO AND CLEMENCEAU AND\
PRESIDENT WILSON AT PARIS]\
\
=The Supreme Council.=--The real work of the settlement was first\
committed to a Supreme Council of ten representing the United States,\
Great Britain, France, Italy, and Japan. This was later reduced to five\
members. Then Japan dropped out and finally Italy, leaving only\
President Wilson and the Premiers, Lloyd George and Clemenceau, the\
"Big Three," who assumed the burden of mighty decisions. On May 6, their\
work was completed and in a secret session of the full conference the\
whole treaty of peace was approved, though a few of the powers made\
reservations or objections. The next day the treaty was presented to the\
Germans who, after prolonged protests, signed on the last day of grace,\
June 28. This German treaty was followed by agreements with Austria,\
Hungary, Bulgaria, and Turkey. Collectively these great documents formed\
the legal basis of the general European settlement.\
\
=The Terms of the Settlement.=--The combined treaties make a huge\
volume. The German treaty alone embraces about 80,000 words.\
Collectively they cover an immense range of subjects which may be\
summarized under five heads: (1) The territorial settlement in Europe;\
(2) the destruction of German military power; (3) reparations for\
damages done by Germany and her allies; (4) the disposition of German\
colonies and protectorates; and (5) the League of Nations.\
\
Germany was reduced by the cession of Alsace-Lorraine to France and the\
loss of several other provinces. Austria-Hungary was dissolved and\
dismembered. Russia was reduced by the creation of new states on the\
west. Bulgaria was stripped of her gains in the recent Balkan wars.\
Turkey was dismembered. Nine new independent states were created:\
Poland, Finland, Lithuania, Latvia, Esthonia, Ukraine, Czechoslovakia,\
Armenia, and Hedjaz. Italy, Greece, Rumania, and Serbia were enlarged by\
cessions of territory and Serbia was transformed into the great state of\
Jugoslavia.\
\
The destruction of German military power was thorough. The entire navy,\
with minor exceptions, was turned over to the Allied and Associated\
Powers; Germany's total equipment for the future was limited to six\
battleships and six light cruisers, with certain small vessels but no\
submarines. The number of enlisted men and officers for the army was\
fixed at not more than 100,000; the General Staff was dissolved; and the\
manufacture of munitions restricted.\
\
Germany was compelled to accept full responsibility for all damages; to\
pay five billion dollars in cash and goods, and to make certain other\
payments which might be ordered from time to time by an inter-allied\
reparations commission. She was also required to deliver to Belgium,\
France, and Italy, millions of tons of coal every year for ten years;\
while by way of additional compensation to France the rich coal basin of\
the Saar was placed under inter-allied control to be exploited under\
French administration for a period of at least fifteen years. Austria\
and the other associates of Germany were also laid under heavy\
obligations to the victors. Damages done to shipping by submarines and\
other vessels were to be paid for on the basis of ton for ton.\
\
The disposition of the German colonies and the old Ottoman empire\
presented knotty problems. It was finally agreed that the German\
colonies and Turkish provinces which were in a backward stage of\
development should be placed under the tutelage of certain powers acting\
as "mandatories" holding them in "a sacred trust of civilization." An\
exception to the mandatory principle arose in the case of German rights\
in Shantung, all of which were transferred directly to Japan. It was\
this arrangement that led the Chinese delegation to withhold their\
signatures from the treaty.\
\
=The League of Nations.=--High among the purposes which he had in mind\
in summoning the nation to arms, President Wilson placed the desire to\
put an end to war. All through the United States the people spoke of the\
"war to end war." No slogan called forth a deeper response from the\
public. The President himself repeatedly declared that a general\
association of nations must be formed to guard the peace and protect all\
against the ambitions of the few. "As I see it," he said in his address\
on opening the Fourth Liberty Loan campaign, "the constitution of the\
League of Nations and the clear definition of its objects must be a\
part, in a sense the most essential part, of the peace settlement\
itself."\
\
Nothing was more natural, therefore, than Wilson's insistence at Paris\
upon the formation of an international association. Indeed he had gone\
to Europe in person largely to accomplish that end. Part One of the\
treaty with Germany, the Covenant of the League of Nations, was due to\
his labors more than to any other influence. Within the League thus\
created were to be embraced all the Allied and Associated Powers and\
nearly all the neutrals. By a two-thirds vote of the League Assembly the\
excluded nations might be admitted.\
\
The agencies of the League of Nations were to be three in number: (1) a\
permanent secretariat located at Geneva; (2) an Assembly consisting of\
one delegate from each country, dominion, or self-governing colony\
(including Canada, Australia, South Africa, New Zealand, and India); (3)\
and a Council consisting of representatives of the United States, Great\
Britain, France, Italy, and Japan, and four other representatives\
selected by the Assembly from time to time.\
\
The duties imposed on the League and the obligations accepted by its\
members were numerous and important. The Council was to take steps to\
formulate a scheme for the reduction of armaments and to submit a plan\
for the establishment of a permanent Court of International Justice. The\
members of the League (Article X) were to respect and preserve as\
against external aggression the territorial integrity and existing\
political independence of all the associated nations. They were to\
submit to arbitration or inquiry by the Council all disputes which could\
not be adjusted by diplomacy and in no case to resort to war until three\
months after the award. Should any member disregard its covenants, its\
action would be considered an act of war against the League, which would\
accordingly cut off the trade and business of the hostile member and\
recommend through the Council to the several associated governments the\
military measures to be taken. In case the decision in any arbitration\
of a dispute was unanimous, the members of the League affected by it\
were to abide by it.\
\
Such was the settlement at Paris and such was the association of nations\
formed to promote the peace of the world. They were quickly approved by\
most of the powers, and the first Assembly of the League of Nations met\
at Geneva late in 1920.\
\
=The Treaty in the United States.=--When the treaty was presented to the\
United States Senate for approval, a violent opposition appeared. In\
that chamber the Republicans had a slight majority and a two-thirds vote\
was necessary for ratification. The sentiment for and against the treaty\
ran mainly along party lines; but the Republicans were themselves\
divided. The major portion, known as "reservationists," favored\
ratification with certain conditions respecting American rights; while a\
small though active minority rejected the League of Nations in its\
entirety, announcing themselves to be "irreconcilables." The grounds of\
this Republican opposition lay partly in the terms of peace imposed on\
Germany and partly in the Covenant of the League of Nations. Exception\
was taken to the clauses which affected the rights of American citizens\
in property involved in the adjustment with Germany, but the burden of\
criticism was directed against the League. Article X guaranteeing\
against external aggression the political independence and territorial\
integrity of the members of the League was subjected to a specially\
heavy fire; while the treatment accorded to China and the sections\
affecting American internal affairs were likewise attacked as "unjust\
and dangerous." As an outcome of their deliberations, the Republicans\
proposed a long list of reservations which touched upon many of the\
vital parts of the treaty. These were rejected by President Wilson as\
amounting in effect to a "nullification of the treaty." As a deadlock\
ensued the treaty was definitely rejected, owing to the failure of its\
sponsors to secure the requisite two-thirds vote.\
\
[Illustration: EUROPE]\
\
=The League of Nations in the Campaign of 1920.=--At this juncture the\
presidential campaign of 1920 opened. The Republicans, while condemning\
the terms of the proposed League, endorsed the general idea of an\
international agreement to prevent war. Their candidate, Senator\
Warren G. Harding of Ohio, maintained a similar position without saying\
definitely whether the League devised at Paris could be recast in such a\
manner as to meet his requirements. The Democrats, on the other hand,\
while not opposing limitations clarifying the obligations of the United\
States, demanded "the immediate ratification of the treaty without\
reservations which would impair its essential integrity." The Democratic\
candidate, Governor James M. Cox, of Ohio, announced his firm conviction\
that the United States should "go into the League," without closing the\
door to mild reservations; he appealed to the country largely on that\
issue. The election of Senator Harding, in an extraordinary "landslide,"\
coupled with the return of a majority of Republicans to the Senate, made\
uncertain American participation in the League of Nations.\
\
=The United States and International Entanglements.=--Whether America\
entered the League or not, it could not close its doors to the world and\
escape perplexing international complications. It had ever-increasing\
financial and commercial connections with all other countries. Our\
associates in the recent war were heavily indebted to our government.\
The prosperity of American industries depended to a considerable extent\
upon the recovery of the impoverished and battle-torn countries of\
Europe.\
\
There were other complications no less specific. The United States was\
compelled by force of circumstances to adopt a Russian policy. The\
government of the Czar had been overthrown by a liberal revolution,\
which in turn had been succeeded by an extreme, communist\
"dictatorship." The Bolsheviki, or majority faction of the socialists,\
had obtained control of the national council of peasants, workingmen,\
and soldiers, called the soviet, and inaugurated a radical regime. They\
had made peace with Germany in March, 1918. Thereupon the United States\
joined England, France, and Japan in an unofficial war upon them. After\
the general settlement at Paris in 1919, our government, while\
withdrawing troops from Siberia and Archangel, continued in its refusal\
to recognize the Bolshevists or to permit unhampered trade with them.\
President Wilson repeatedly denounced them as the enemies of\
civilization and undertook to lay down for all countries the principles\
which should govern intercourse with Russia.\
\
Further international complications were created in connection with the\
World War, wholly apart from the terms of peace or the League of\
Nations. The United States had participated in a general European\
conflict which changed the boundaries of countries, called into being\
new nations, and reduced the power and territories of the vanquished.\
Accordingly, it was bound to face the problem of how far it was prepared\
to cooperate with the victors in any settlement of Europe's\
difficulties. By no conceivable process, therefore, could America be\
disentangled from the web of world affairs. Isolation, if desirable, had\
become impossible. Within three hundred years from the founding of the\
tiny settlements at Jamestown and Plymouth, America, by virtue of its\
institutions, its population, its wealth, and its commerce, had become\
first among the nations of the earth. By moral obligations and by\
practical interests its fate was thus linked with the destiny of all\
mankind.\
\
\
SUMMARY OF DEMOCRACY AND THE WORLD WAR\
\
The astounding industrial progress that characterized the period\
following the Civil War bequeathed to the new generation many perplexing\
problems connected with the growth of trusts and railways, the\
accumulation of great fortunes, the increase of poverty in the\
industrial cities, the exhaustion of the free land, and the acquisition\
of dominions in distant seas. As long as there was an abundance of land\
in the West any able-bodied man with initiative and industry could\
become an independent farmer. People from the cities and immigrants from\
Europe had always before them that gateway to property and prosperity.\
When the land was all gone, American economic conditions inevitably\
became more like those of Europe.\
\
Though the new economic questions had been vigorously debated in many\
circles before his day, it was President Roosevelt who first discussed\
them continuously from the White House. The natural resources of the\
country were being exhausted; he advocated their conservation. Huge\
fortunes were being made in business creating inequalities in\
opportunity; he favored reducing them by income and inheritance taxes.\
Industries were disturbed by strikes; he pressed arbitration upon\
capital and labor. The free land was gone; he declared that labor was in\
a less favorable position to bargain with capital and therefore should\
organize in unions for collective bargaining. There had been wrong-doing\
on the part of certain great trusts; those responsible should be\
punished.\
\
The spirit of reform was abroad in the land. The spoils system was\
attacked. It was alleged that the political parties were dominated by\
"rings and bosses." The United States Senate was called "a millionaires'\
club." Poverty and misery were observed in the cities. State\
legislatures and city governments were accused of corruption.\
\
In answer to the charges, remedies were proposed and adopted. Civil\
service reform was approved. The Australian ballot, popular election of\
Senators, the initiative, referendum, and recall, commission and city\
manager plans for cities, public regulation of railways, compensation\
for those injured in industries, minimum wages for women and children,\
pensions for widows, the control of housing in the cities--these and a\
hundred other reforms were adopted and tried out. The national watchword\
became: "America, Improve Thyself."\
\
The spirit of reform broke into both political parties. It appeared in\
many statutes enacted by Congress under President Taft's leadership. It\
disrupted the Republicans temporarily in 1912 when the Progressive party\
entered the field. It led the Democratic candidate in that year,\
Governor Wilson, to make a "progressive appeal" to the voters. It\
inspired a considerable program of national legislation under President\
Wilson's two administrations.\
\
In the age of change, four important amendments to the federal\
constitution, the first in more than forty years, were adopted. The\
sixteenth empowered Congress to lay an income tax. The seventeenth\
assured popular election of Senators. The eighteenth made prohibition\
national. The nineteenth, following upon the adoption of woman suffrage\
in many states, enfranchised the women of the nation.\
\
In the sphere of industry, equally great changes took place. The major\
portion of the nation's business passed into the hands of corporations.\
In all the leading industries of the country labor was organized into\
trade unions and federated in a national organization. The power of\
organized capital and organized labor loomed upon the horizon. Their\
struggles, their rights, and their place in the economy of the nation\
raised problems of the first magnitude.\
\
While the country was engaged in a heated debate upon its domestic\
issues, the World War broke out in Europe in 1914. As a hundred years\
before, American rights upon the high seas became involved at once. They\
were invaded on both sides; but Germany, in addition to assailing\
American ships and property, ruthlessly destroyed American lives. She\
set at naught the rules of civilized warfare upon the sea. Warnings from\
President Wilson were without avail. Nothing could stay the hand of the\
German war party.\
\
After long and patient negotiations, President Wilson in 1917 called\
upon the nation to take up arms against an assailant that had in effect\
declared war upon America. The answer was swift and firm. The national\
resources, human and material, were mobilized. The navy was enlarged, a\
draft army created, huge loans floated, heavy taxes laid, and the spirit\
of sacrifice called forth in a titanic struggle against an autocratic\
power that threatened to dominate Europe and the World.\
\
In the end, American financial, naval, and military assistance counted\
heavily in the scale. American sailors scoured the seas searching for\
the terrible submarines. American soldiers took part in the last great\
drives that broke the might of Germany's army. Such was the nation's\
response to the President's summons to arms in a war "for democracy" and\
"to end war."\
\
When victory crowned the arms of the powers united against Germany,\
President Wilson in person took part in the peace council. He sought to\
redeem his pledge to end wars by forming a League of Nations to keep the\
peace. In the treaty drawn at the close of the war the first part was a\
covenant binding the nations in a permanent association for the\
settlement of international disputes. This treaty, the President offered\
to the United States Senate for ratification and to his country for\
approval.\
\
Once again, as in the days of the Napoleonic wars, the people seriously\
discussed the place of America among the powers of the earth. The Senate\
refused to ratify the treaty. World politics then became an issue in the\
campaign of 1920. Though some Americans talked as if the United States\
could close its doors and windows against all mankind, the victor in the\
election, Senator Harding, of Ohio, knew better. The election returns\
were hardly announced before he began to ask the advice of his\
countrymen on the pressing theme that would not be downed: "What part\
shall America--first among the nations of the earth in wealth and\
power--assume at the council table of the world?"\
\
\
=General References=\
\
Woodrow Wilson, _The New Freedom_.\
\
C.L. Jones, _The Caribbean Interests of the United States_.\
\
H.P. Willis, _The Federal Reserve_.\
\
C.W. Barron, _The Mexican Problem_ (critical toward Mexico).\
\
L.J. de Bekker, _The Plot against Mexico_ (against American\
intervention).\
\
Theodore Roosevelt, _America and the World War_.\
\
E.E. Robinson and V.J. West, _The Foreign Policy of Woodrow Wilson_.\
\
J.S. Bassett, _Our War with Germany_.\
\
Carlton J.H. Hayes, _A Brief History of the Great War_.\
\
J.B. McMaster, _The United States in the World War_.\
\
\
=Research Topics=\
\
=President Wilson's First Term.=--Elson, _History of the United States_,\
pp. 925-941.\
\
=The Underwood Tariff Act.=--Ogg, _National Progress_ (The American\
Nation Series), pp. 209-226.\
\
=The Federal Reserve System.=--Ogg, pp. 228-232.\
\
=Trust and Labor Legislation.=--Ogg, pp. 232-236.\
\
=Legislation Respecting the Territories.=--Ogg, pp. 236-245.\
\
=American Interests in the Caribbean.=--Ogg, pp. 246-265.\
\
=American Interests in the Pacific.=--Ogg, pp. 304-324.\
\
=Mexican Affairs.=--Haworth, pp. 388-395; Ogg, pp. 284-304.\
\
=The First Phases of the European War.=--Haworth, pp. 395-412; Ogg, pp.\
325-343.\
\
=The Campaign of 1916.=--Haworth, pp. 412-418; Ogg, pp. 364-383.\
\
=America Enters the War.=--Haworth, pp. 422-440; pp. 454-475. Ogg, pp.\
384-399; Elson, pp. 951-970.\
\
=Mobilizing the Nation.=--Haworth, pp. 441-453.\
\
=The Peace Settlement.=--Haworth, pp. 475-497; Elson, pp. 971-982.\
\
\
=Questions=\
\
1. Enumerate the chief financial measures of the Wilson administration.\
Review the history of banks and currency and give the details of the\
Federal reserve law.\
\
2. What was the Wilson policy toward trusts? Toward labor?\
\
3. Review again the theory of states' rights. How has it fared in recent\
years?\
\
4. What steps were taken in colonial policies? In the Caribbean?\
\
5. Outline American-Mexican relations under Wilson.\
\
6. How did the World War break out in Europe?\
\
7. Account for the divided state of opinion in America.\
\
8. Review the events leading up to the War of 1812. Compare them with\
the events from 1914 to 1917.\
\
9. State the leading principles of international law involved and show\
how they were violated.\
\
10. What American rights were assailed in the submarine campaign?\
\
11. Give Wilson's position on the _Lusitania_ affair.\
\
12. How did the World War affect the presidential campaign of 1916?\
\
13. How did Germany finally drive the United States into war?\
\
14. State the American war aims given by the President.\
\
15. Enumerate the measures taken by the government to win the war.\
\
16. Review the part of the navy in the war. The army.\
\
17. How were the terms of peace formulated?\
\
18. Enumerate the principal results of the war.\
\
19. Describe the League of Nations.\
\
20. Trace the fate of the treaty in American politics.\
\
21. Can there be a policy of isolation for America?\
\
\
\
\
APPENDIX\
\
CONSTITUTION OF THE UNITED STATES\
\
\
We the people of the United States, in order to form a more\
perfect union, establish justice, insure domestic tranquillity, provide\
for the common defence, promote the general welfare, and secure the\
blessings of liberty to ourselves and our posterity, do ordain and\
establish this Constitution for the United States of America.\
\
\
ARTICLE I\
\
SECTION 1. All legislative powers herein granted shall be vested in a\
Congress of the United States, which shall consist of a Senate and House\
of Representatives.\
\
\
SECTION 2. 1. The House of Representatives shall be composed of members\
chosen every second year by the people of the several States, and the\
electors in each State shall have the qualifications requisite for\
electors of the most numerous branch of the State legislature.\
\
2. No person shall be a representative who shall not have attained to\
the age of twenty-five years, and been seven years a citizen of the\
United States, and who shall not, when elected, be an inhabitant of that\
State in which he shall be chosen.\
\
3. Representatives and direct taxes[3] shall be apportioned among the\
several States which may be included within this Union, according to\
their respective numbers, which shall be determined by adding to the\
whole number of free persons, including those bound to service for a\
term of years, and excluding Indians not taxed, three-fifths of all\
other persons.[3] The actual enumeration shall be made within three\
years after the first meeting of the Congress of the United States, and\
within every subsequent term of ten years, in such manner as they shall\
by law direct. The number of representatives shall not exceed one for\
every thirty thousand, but each State shall have at least one\
representative; and until such enumeration shall be made, the State of\
New Hampshire shall be entitled to choose three, Massachusetts eight,\
Rhode Island and Providence Plantations one, Connecticut five, New York\
six, New Jersey four, Pennsylvania eight, Delaware one, Maryland six,\
Virginia ten, North Carolina five, South Carolina five, and Georgia\
three.\
\
4. When vacancies happen in the representation from any State, the\
executive authority thereof shall issue writs of election to fill such\
vacancies.\
\
5. The House of Representatives shall choose their speaker and other\
officers; and shall have the sole power of impeachment.\
\
\
SECTION 3. 1. The Senate of the United States shall be composed of two\
senators from each State, chosen by the legislature thereof, for six\
years; and each senator shall have one vote.[4]\
\
2. Immediately after they shall be assembled in consequence of the first\
election, they shall be divided as equally as may be into three classes.\
The seats of the senators of the first class shall be vacated at the\
expiration of the second year, of the second class at the expiration of\
the fourth year, and of the third class at the expiration of the sixth\
year, so that one-third may be chosen every second year; and if\
vacancies happen by resignation, or otherwise, during the recess of the\
legislature of any State, the executive thereof may make temporary\
appointments until the next meeting of the legislature, which shall then\
fill such vacancies.[5]\
\
3. No person shall be a senator who shall not have attained to the age\
of thirty years, and been nine years a citizen of the United States, and\
who shall not, when elected, be an inhabitant of that State for which he\
shall be chosen.\
\
4. The Vice-President of the United States shall be President of the\
Senate, but shall have no vote, unless they be equally divided.\
\
5. The Senate shall choose their other officers, and also a President\
_pro tempore_, in the absence of the Vice-President, or when he shall\
exercise the office of President of the United States.\
\
6. The Senate shall have the sole power to try all impeachments. When\
sitting for that purpose, they shall be on oath or affirmation. When the\
President of the United States is tried, the chief justice shall\
preside: And no person shall be convicted without the concurrence of\
two-thirds of the members present.\
\
7. Judgment in cases of impeachment shall not extend further than to\
removal from office, and disqualification to hold and enjoy any office\
of honor, trust, or profit under the United States: but the party\
convicted shall nevertheless be liable and subject to indictment, trial,\
judgment, and punishment, according to law.\
\
\
SECTION 4. 1. The times, places, and manner of holding elections for\
senators and representatives, shall be prescribed in each State by the\
legislature thereof; but the Congress may at any time by law make or\
alter such regulations, except as to the places of choosing senators.\
\
2. The Congress shall assemble at least once in every year, and such\
meeting shall be on the first Monday in December, unless they shall by\
law appoint a different day.\
\
\
SECTION 5. 1. Each House shall be the judge of the elections, returns\
and qualifications of its own members, and a majority of each shall\
constitute a quorum to do business; but a smaller number may adjourn\
from day to day, and may be authorized to compel the attendance of\
absent members, in such manner, and under such penalties as each House\
may provide.\
\
2. Each House may determine the rules of its proceedings, punish its\
members for disorderly behaviour, and, with the concurrence of\
two-thirds, expel a member.\
\
3. Each House shall keep a journal of its proceedings, and from time to\
time publish the same, excepting such parts as may in their judgment\
require secrecy; and the yeas and nays of the members of either House on\
any question shall, at the desire of one-fifth of those present, be\
entered on the journal.\
\
4. Neither House, during the session of Congress, shall, without the\
consent of the other, adjourn for more than three days, nor to any other\
place than that in which the two Houses shall be sitting.\
\
\
SECTION 6. 1. The senators and representatives shall receive a\
compensation for their services, to be ascertained by law, and paid out\
of the Treasury of the United States. They shall in all cases, except\
treason, felony, and breach of the peace, be privileged from arrest\
during their attendance at the sessions of their respective Houses, and\
in going to and returning from the same; and, for any speech or debate\
in either House, they shall not be questioned in any other place.\
\
2. No senator or representative shall, during the time for which he was\
elected, be appointed to any civil office under the authority of the\
United States, which shall have been created, or the emoluments whereof\
shall have been increased during such time; and no person, holding any\
office under the United States, shall be a member of either House during\
his continuance in office.\
\
\
SECTION 7. 1. All bills for raising revenue shall originate in the House\
of Representatives; but the Senate may propose or concur with amendments\
as on other bills.\
\
2. Every bill, which shall have passed the House of Representatives; and\
the Senate, shall, before it become a law, be presented to the President\
of the United States; if he approve he shall sign it, but if not he\
shall return it with his objections to that House, in which it shall\
have originated, who shall enter the objections at large on their\
journal, and proceed to reconsider it. If after such reconsideration\
two-thirds of that House shall agree to pass the bill, it shall be sent,\
together with the objections, to the other House, by which it shall\
likewise be reconsidered, and if approved by two-thirds of that House,\
it shall become a law. But in all such cases the votes of both Houses\
shall be determined by yeas and nays, and the names of the persons\
voting for and against the bill shall be entered on the journal of each\
House respectively. If any bill shall not be returned by the President\
within ten days (Sundays excepted) after it shall have been presented to\
him, the same shall be a law, in like manner as if he had signed it,\
unless the Congress by their adjournment prevent its return, in which\
case it shall not be a law.\
\
3. Every order, resolution, or vote to which the concurrence of the\
Senate and House of Representatives may be necessary (except on a\
question of adjournment) shall be presented to the President of the\
United States and before the same shall take effect, shall be approved\
by him, or being disapproved by him, shall be repassed by two-thirds of\
the Senate and House of Representatives, according to the rules and\
limitations prescribed in the case of a bill.\
\
\
SECTION 8. The Congress shall have power: 1. To lay and collect taxes,\
duties, imposts, and excises, to pay the debts and provide for the\
common defence and general welfare of the United States; but all duties,\
imposts, and excises shall be uniform throughout the United States;\
\
2. To borrow money on the credit of the United States;\
\
3. To regulate commerce with foreign nations, and among the several\
States, and with the Indian tribes;\
\
4. To establish an uniform rule of naturalization, and uniform laws on\
the subject of bankruptcies throughout the United States;\
\
5. To coin money, regulate the value thereof, and of foreign coin, and\
fix the standard of weights and measures;\
\
6. To provide for the punishment of counterfeiting the securities and\
current coin of the United States;\
\
7. To establish post offices and post roads;\
\
8. To promote the progress of science and useful arts by securing for\
limited times to authors and inventors the exclusive right to their\
respective writings and discoveries;\
\
9. To constitute tribunals inferior to the Supreme Court;\
\
10. To define and punish piracies and felonies committed on the high\
seas, and offences against the law of nations;\
\
11. To declare war, grant letters of marque and reprisal, and make rules\
concerning captures on land and water;\
\
12. To raise and support armies, but no appropriation of money to that\
use shall be for a longer term than two years;\
\
13. To provide and maintain a navy;\
\
14. To make rules for the government and regulation of the land and\
naval forces;\
\
15. To provide for calling forth the militia to execute the laws of the\
Union, suppress insurrections, and repel invasions;\
\
16. To provide for organizing, arming, and disciplining the militia,\
and for governing such part of them as may be employed in the service\
of the United States, reserving to the States respectively the\
appointment of the officers, and the authority of training the militia\
according to the discipline prescribed by Congress.\
\
17. To exercise exclusive legislation in all cases whatsoever, over such\
district (not exceeding ten miles square) as may, by cession of\
particular States and the acceptance of Congress, become the seat of the\
government of the United States, and to exercise like authority over all\
places purchased by the consent of the legislature of the State in which\
the same shall be, for the erection of forts, magazines, arsenals,\
dock-yards, and other needful buildings;--and\
\
18. To make all laws which shall be necessary and proper for carrying\
into execution the foregoing powers, and all other powers vested by this\
Constitution in the government of the United States, or in any\
department or officer thereof.\
\
\
SECTION 9. 1. The migration or importation of such persons as any of the\
States now existing shall think proper to admit, shall not be prohibited\
by the Congress prior to the year one thousand eight hundred and eight,\
but a tax or duty may be imposed on such importation, not exceeding ten\
dollars for each person.\
\
2. The privilege of the writ of _habeas corpus_ shall not be suspended,\
unless when in cases of rebellion or invasion the public safety may\
require it.\
\
3. No bill of attainder or _ex post facto_ law shall be passed.\
\
4. No capitation, or other direct, tax shall be laid, unless in\
proportion to the census or enumeration hereinbefore directed to be\
taken.[6]\
\
5. No tax or duty shall be laid on articles exported from any State.\
\
6. No preference shall be given by any regulation of commerce or revenue\
to the ports of one State over those of another: nor shall vessels bound\
to, or from, one State, be obliged to enter, clear, or pay duties in\
another.\
\
7. No money shall be drawn from the Treasury, but in consequence of\
appropriations made by law; and a regular statement and account of the\
receipts and expenditures of all public money shall be published from\
time to time.\
\
8. No title of nobility shall be granted by the United States; and no\
person, holding any office of profit or trust under them, shall, without\
the consent of the Congress, accept of any present, emolument, office,\
or title, of any kind whatever, from any king, prince, or foreign State.\
\
\
SECTION 10. 1. No State shall enter into any treaty, alliance, or\
confederation; grant letters of marque and reprisal; coin money; emit\
bills of credit; make anything but gold and silver coin a tender in\
payment of debts; pass any bill of attainder, _ex post facto_ law, or\
law impairing the obligation of contracts, or grant any title of\
nobility.\
\
2. No State shall, without the consent of the Congress, lay any imposts\
or duties on imports or exports, except what may be absolutely necessary\
for executing its inspection laws: and the net produce of all duties and\
imposts, laid by any State on imports or exports, shall be for the use\
of the Treasury of the United States; and all such laws shall be subject\
to the revision and control of the Congress.\
\
3. No State shall, without the consent of Congress, lay any duty of\
tonnage, keep troops, or ships of war in time of peace, enter into any\
agreement or compact with another State, or with a foreign power, or\
engage in war unless actually invaded, or in such imminent danger as\
will not admit of delay.\
\
\
ARTICLE II\
\
SECTION 1. 1. The executive power shall be vested in a President of the\
United States of America. He shall hold his office during the term of\
four years, and, together with the Vice-President, chosen for the same\
term, be elected, as follows:\
\
2. Each State shall appoint, in such manner as the legislature thereof\
may direct, a number of electors, equal to the whole number of senators\
and representatives to which the State may be entitled in the Congress;\
but no senator or representative, or person holding an office of trust\
or profit under the United States, shall be appointed an elector.[7] The\
electors shall meet in their respective States, and vote by ballot for\
two persons, of whom one at least shall not be an inhabitant of the same\
State with themselves. And they shall make a list of all the persons\
voted for, and of the number of votes for each; which list they shall\
sign and certify, and transmit sealed to the seat of the government of\
the United States, directed to the president of the Senate. The\
President of the Senate shall, in the presence of the Senate and House\
of Representatives, open all the certificates, and the votes shall then\
be counted. The person having the greatest number of votes shall be the\
President, if such number be a majority of the whole number of electors\
appointed; and if there be more than one who have such majority, and\
have an equal number of votes, then the House of Representatives shall\
immediately choose by ballot one of them for President; and if no person\
have a majority, then from the five highest on the list the said House\
shall in like manner choose the President. But in choosing the\
President, the votes shall be taken by States, the representation from\
each State having one vote; a quorum for this purpose shall consist of a\
member or members from two-thirds of the States and a majority of all\
the States shall be necessary to a choice. In every case, after the\
choice of the President, the person having the greatest number of votes\
of the electors shall be the Vice-President. But if there should remain\
two or more who have equal votes, the Senate shall choose from them by\
ballot the Vice-President.[8]\
\
3. The Congress may determine the time of choosing the electors, and the\
day on which they shall give their votes; which day shall be the same\
throughout the United States.\
\
4. No person except a natural born citizen, or a citizen of the United\
States, at the time of the adoption of this Constitution, shall be\
eligible to the office of President; neither shall any person be\
eligible to that office who shall not have attained to the age of\
thirty-five years, and been fourteen years a resident within the United\
States.\
\
5. In case of the removal of the President from office, or of his death,\
resignation, or inability to discharge the powers and duties of the said\
office, the same shall devolve on the Vice-President, and the Congress\
may by law provide for the case of removal, death, resignation, or\
inability both of the President and Vice-President, declaring what\
officer shall then act as President, and such officer shall act\
accordingly, until the disability be removed, or a President shall be\
elected.\
\
6. The President shall, at stated times, receive for his services a\
compensation, which shall neither be increased nor diminished during the\
period for which he shall have been elected, and he shall not receive\
within that period any other emolument from the United States, or any of\
them.\
\
7. Before he enter on the execution of his office, he shall take the\
following oath or affirmation:--"I do solemnly swear (or affirm) that I\
will faithfully execute the office of President of the United States,\
and will to the best of my ability, preserve, protect, and defend the\
Constitution of the United States."\
\
\
SECTION 2. 1. The President shall be commander-in-chief of the army and\
navy of the United States, and of the militia of the several States,\
when called into the actual service of the United States; he may require\
the opinion, in writing, of the principal officer in each of the\
executive departments, upon any subject relating to the duties of their\
respective offices, and he shall have power to grant reprieves and\
pardons for offences against the United States, except in cases of\
impeachment.\
\
2. He shall have power, by and with the advice and consent of the\
Senate, to make treaties, provided two-thirds of the senators present\
concur; and he shall nominate, and by and with the advice and consent of\
the Senate, shall appoint ambassadors, other public ministers and\
consuls, judges of the Supreme Court, and all other officers of the\
United States, whose appointments are not herein otherwise provided for,\
and which shall be established by law: but the Congress may by law vest\
the appointment of such inferior officers, as they think proper, in the\
President alone, in the courts of law, or in the heads of departments.\
\
3. The President shall have power to fill all vacancies that may happen\
during the recess of the Senate, by granting commissions which shall\
expire at the end of their next session.\
\
\
SECTION 3. He shall from time to time give to the Congress information\
on the state of the Union, and recommend to their consideration such\
measures as he shall judge necessary and expedient; he may, on\
extraordinary occasions, convene both Houses, or either of them, and in\
case of disagreement between them, with respect to the time of\
adjournment, he may adjourn them to such time as he shall think proper;\
he shall receive ambassadors and other public ministers; he shall take\
care that the laws be faithfully executed, and shall commission all the\
officers of the United States.\
\
\
SECTION 4. The President, Vice-President, and all civil officers of the\
United States shall be removed from office on impeachment for, and\
conviction of, treason, bribery, or other high crimes and misdemeanors.\
\
\
ARTICLE III\
\
SECTION 1. The judicial power of the United States shall be vested in\
one Supreme Court, and in such inferior courts as the Congress may from\
time to time ordain and establish. The judges, both of the Supreme and\
inferior courts, shall hold their offices during good behaviour, and\
shall, at stated times, receive for their services a compensation, which\
shall not be diminished during their continuance in office.\
\
\
SECTION 2. 1. The judicial power shall extend to all cases, in law and\
equity, arising under this Constitution, the laws of the United States,\
and treaties made, or which shall be made, under their authority;--to\
all cases affecting ambassadors, other public ministers and consuls;--to\
all cases of admiralty and maritime jurisdiction;--to controversies to\
which the United States shall be a party;--to controversies between two\
or more States;--between a State and citizens of another\
State;[9]--between citizens of different States;--between citizens of\
the same State claiming lands under grants of different States;--and\
between a State, or the citizens thereof, and foreign States, citizens,\
or subjects.\
\
2. In all cases affecting ambassadors, other public ministers and\
consuls and those in which a State shall be a party, the Supreme Court\
shall have original jurisdiction. In all the other cases before\
mentioned, the Supreme Court shall have appellate jurisdiction, both as\
to law and fact, with such exceptions and under such regulations as the\
Congress shall make.\
\
3. The trial of all crimes, except in cases of impeachment, shall be by\
jury; and such trial shall be held in the State where the said crimes\
shall have been committed; but when not committed within any State, the\
trial shall be at such place or places as the Congress may by law have\
directed.\
\
\
SECTION 3. 1. Treason against the United States shall consist only in\
levying war against them, or in adhering to their enemies, giving them\
aid and comfort. No person shall be convicted of treason unless on the\
testimony of two witnesses to the same overt act, or on confession in\
open court.\
\
2. The Congress shall have power to declare the punishment of treason,\
but no attainder of treason shall work corruption of blood or forfeiture\
except during the life of the person attainted.\
\
\
ARTICLE IV\
\
SECTION 1. Full faith and credit shall be given in each State to the\
public acts, records, and judicial proceedings of every other State. And\
the Congress may by general laws prescribe the manner in which such\
acts, records, and proceedings shall be proved, and the effect thereof.\
\
\
SECTION 2. 1. The citizens of each State shall be entitled to all\
privileges and immunities of citizens in the several States.\
\
2. A person charged in any State with treason, felony, or other crime,\
who shall flee from justice, and be found in another State, shall on\
demand of the executive authority of the State from which he fled, be\
delivered up, to be removed to the State having jurisdiction of the\
crime.\
\
3. No person held to service or labor in one State, under the laws\
thereof, escaping into another, shall, in consequence of any law or\
regulation therein, be discharged from such service or labor, but shall\
be delivered up on claim of the party to whom such service or labor may\
be due.\
\
\
SECTION 3. 1. New States may be admitted by the Congress into this\
Union; but no new State shall be formed or erected within the\
jurisdiction of any other State; nor any State be formed by the junction\
of two or more States, or parts of States, without the consent of the\
legislatures of the States concerned as well as of the Congress.\
\
2. The Congress shall have power to dispose of and make all needful\
rules and regulations respecting the territory or other property\
belonging to the United States; and nothing in this Constitution shall\
be so construed as to prejudice any claims, of the United States, or of\
any particular State.\
\
\
SECTION 4. The United States shall guarantee to every State in this\
Union a republican form of government, and shall protect each of them\
against invasion; and on application of the legislature, or of the\
executive (when the legislature cannot be convened), against domestic\
violence.\
\
\
ARTICLE V\
\
The Congress, whenever two-thirds of both Houses shall deem it\
necessary, shall propose amendments to this Constitution, or, on the\
application of the legislatures of two-thirds of the several States,\
shall call a convention for proposing amendments, which, in either case,\
shall be valid to all intents and purposes as part of this Constitution,\
when ratified by the legislatures of three-fourths of the several\
States, or by conventions in three-fourths thereof, as the one or the\
other mode of ratification may be proposed by the Congress; provided\
that no amendment which may be made prior to the year one thousand eight\
hundred and eight shall in any manner affect the first and fourth\
clauses in the ninth Section of the first article; and that no State,\
without its consent, shall be deprived of its equal suffrage in the\
Senate.\
\
\
ARTICLE VI\
\
1. All debts contracted and engagements entered into, before the\
adoption of this Constitution, shall be as valid against the United\
States under this Constitution, as under the Confederation.\
\
2. This Constitution and the laws of the United States which shall be\
made in pursuance thereof and all treaties made, or which shall be made,\
under the authority of the United States, shall be the supreme law of\
the land; and the judges in every State shall be bound thereby, anything\
in the Constitution or laws of any State to the contrary\
notwithstanding.\
\
3. The senators and representatives before mentioned, and the members of\
the several State legislatures, and all executive and judicial officers,\
both of the United States and of the several States, shall be bound by\
oath or affirmation to support this Constitution; but no religious test\
shall ever be required as a qualification to any office or public trust\
under the United States.\
\
\
ARTICLE VII\
\
The ratification of the conventions of nine States shall be sufficient\
for the establishment of this Constitution between the States so\
ratifying the same.\
\
Done in Convention by the unanimous consent of the States present the\
seventeenth day of September in the year of our Lord one thousand seven\
hundred and eighty-seven and of the independence of the United States of\
America the twelfth. In witness whereof we have hereunto subscribed our\
names,\
\
     G^O. WASHINGTON--\
     Presidt. and Deputy from Virginia\
\
[and thirty-eight members from all the States except Rhode Island.]\
\
       *       *       *       *       *\
\
\
Articles in addition to, and amendment of, the Constitution of the\
United States of America, proposed by Congress, and ratified by the\
legislatures of the several States pursuant to the fifth article of the\
original Constitution.\
\
\
ARTICLE I[10]\
\
Congress shall make no law respecting an establishment of religion, or\
prohibiting the free exercise thereof; or abridging the freedom of\
speech, or of the press; or the right of the people peaceably to\
assemble, and to petition the government for a redress of grievances.\
\
\
ARTICLE II\
\
A well regulated militia, being necessary to the security of a free\
State, the right of the people to keep and bear arms shall not be\
infringed.\
\
\
ARTICLE III\
\
No soldier shall, in time of peace, be quartered in any house, without\
the consent of the owner, nor in time of war, but in a manner to be\
prescribed by law.\
\
\
ARTICLE IV\
\
The right of the people to be secure in their persons, houses, papers,\
and effects, against unreasonable searches and seizures, shall not be\
violated, and no warrants shall issue, but upon probable cause,\
supported by oath or affirmation, and particularly describing the place\
to be searched, and the persons or things to be seized.\
\
\
ARTICLE V\
\
No person shall be held to answer for a capital, or otherwise infamous\
crime, unless on a presentment or indictment of a grand jury, except in\
cases arising in the land or naval forces, or in the militia, when in\
actual service in time of war or public danger; nor shall any person be\
subject for the same offence to be twice put in jeopardy of life or\
limb; nor shall be compelled in any criminal case to be a witness\
against himself; nor be deprived of life, liberty, or property, without\
due process of law; nor shall private property be taken for public use,\
without just compensation.\
\
\
ARTICLE VI\
\
In all criminal prosecutions, the accused shall enjoy the right to a\
speedy and public trial, by an impartial jury of the State and district\
wherein the crime shall have been committed, which district shall have\
been previously ascertained by law, and to be informed of the nature and\
cause of the accusation; to be confronted with the witnesses against\
him; to have compulsory process for obtaining witnesses in his favor,\
and to have the assistance of counsel for his defence.\
\
\
ARTICLE VII\
\
In suits at common law, where the value in controversy shall exceed\
twenty dollars, the right of trial by jury shall be preserved, and no\
fact tried by a jury shall be otherwise reexamined in any court of the\
United States, than according to the rules of the common law.\
\
\
ARTICLE VIII\
\
Excessive bail shall not be required, nor excessive fines imposed, nor\
cruel and unusual punishments inflicted.\
\
\
ARTICLE IX\
\
The enumeration in the Constitution, of certain rights, shall not be\
construed to deny or disparage others retained by the people.\
\
\
ARTICLE X\
\
The powers not delegated to the United States by the Constitution, nor\
prohibited by it to the States, are reserved to the States respectively,\
or to the people.\
\
\
ARTICLE XI[11]\
\
The judicial power of the United States shall not be construed to extend\
to any suit in law or equity, commenced or prosecuted against one of the\
United States by citizens of another State, or by citizens or subjects\
of any foreign State.\
\
\
ARTICLE XII[12]\
\
The electors shall meet in their respective States, and vote by ballot\
for President and Vice-President, one of whom at least shall not be an\
inhabitant of the same State with themselves; they shall name in their\
ballots the person voted for as President, and in distinct ballots the\
person voted for as Vice-President, and they shall make distinct lists\
of all persons voted for as President, and of all persons voted for as\
Vice-President, and of the number of votes for each, which lists they\
shall sign and certify, and transmit sealed to the seat of the\
government of the United States, directed to the President of the\
Senate;--The President of the Senate shall, in presence of the Senate\
and House of Representatives, open all the certificates and the votes\
shall then be counted;--The person having the greatest number of votes\
for President, shall be the President, if such number be a majority of\
the whole number of electors appointed; and if no person have such\
majority, then from the persons having the highest numbers not exceeding\
three on the list of those voted for as President, the House of\
Representatives shall choose immediately, by ballot, the President. But\
in choosing the President, the votes shall be taken by States, the\
representation from each State having one vote; a quorum for this\
purpose shall consist of a member or members from two-thirds of the\
States, and a majority of all the States shall be necessary to a choice.\
And if the House of Representatives shall not choose a President\
whenever the right of choice shall devolve upon them, before the fourth\
day of March next following, then the Vice-President shall act as\
President, as in the case of the death or other constitutional\
disability of the President. The person having the greatest number of\
votes as Vice-President, shall be the Vice-President, if such number be\
a majority of the whole number of electors appointed, and if no person\
have a majority, then from the two highest members on the list, the\
Senate shall choose the Vice-President; a quorum for the purpose shall\
consist of two-thirds of the whole number of senators, and a majority of\
the whole number shall be necessary to a choice. But no person\
constitutionally ineligible to the office of President shall be eligible\
to that of Vice-President of the United States.\
\
\
ARTICLE XIII[13]\
\
SECTION 1. Neither slavery nor involuntary servitude, except as a\
punishment for crime whereof the party shall have been duly convicted,\
shall exist within the United States, or any place subject to their\
jurisdiction.\
\
SECTION 2. Congress shall have power to enforce this article by\
appropriate legislation.\
\
\
ARTICLE XIV[14]\
\
SECTION 1. All persons born or naturalized in the United States, and\
subject to the jurisdiction thereof, are citizens of the United States\
and of the State wherein they reside. No State shall make or enforce any\
law which shall abridge the privileges or immunities of citizens of the\
United States; nor shall any State deprive any person of life, liberty,\
or property without due process of law; nor deny to any person within\
its jurisdiction the equal protection of the laws.\
\
SECTION 2. Representatives shall be apportioned among the several States\
according to their respective numbers, counting the whole number of\
persons in each State, excluding Indians not taxed. But when the right\
to vote at any election for the choice of electors for President and\
Vice-President of the United States, representatives in Congress, the\
executive and judicial officers of a State, or the members of the\
legislature thereof, is denied to any of the male inhabitants of such\
State, being twenty-one years of age, and citizens of the United States,\
or in any way abridged, except for participation in rebellion or other\
crime, the basis of representation therein shall be reduced in the\
proportion which the number of such male citizens shall bear to the\
whole number of male citizens twenty-one years of age in such State.\
\
SECTION 3. No person shall be a senator or representative in Congress,\
or elector of President and Vice-President, or hold any office, civil or\
military, under the United States, or under any State, who, having\
previously taken an oath, as a member of Congress, or as an officer of\
the United States, or as a member of any State legislature, or as an\
executive or judicial officer of any State, to support the Constitution\
of the United States, shall have engaged in insurrection or rebellion\
against the same, or given aid or comfort to the enemies thereof. But\
Congress may by two-thirds vote of each House, remove such disability.\
\
SECTION 4. The validity of the public debt of the United States,\
authorized by law, including debts incurred for payment of pensions and\
bounties for services in suppressing insurrection or rebellion, shall\
not be questioned. But neither the United States nor any State shall\
assume or pay any debt or obligation incurred in aid of insurrection or\
rebellion against the United States, or any claim for the loss or\
emancipation of any slave; but all such debts, obligations, and claims\
shall be held illegal and void.\
\
SECTION 5. The Congress shall have power to enforce, by appropriate\
legislation, the provisions of this article.\
\
\
ARTICLE XV[15]\
\
SECTION 1. The right of citizens of the United States to vote shall not\
be denied or abridged by the United States or by any State on account of\
race, color, or previous condition of servitude.\
\
SECTION 2. The Congress shall have power to enforce this article by\
appropriate legislation.\
\
\
ARTICLE XVI[16]\
\
The Congress shall have power to lay and collect taxes on incomes, from\
whatever source derived, without apportionment among the several States,\
and without regard to any census or enumeration.\
\
\
ARTICLE XVII[17]\
\
The Senate of the United States shall be composed of two senators from\
each State, elected by the people thereof, for six years; and each\
senator shall have one vote. The electors in each State shall have the\
qualifications requisite for electors of the most numerous branch of the\
State legislature.\
\
When vacancies happen in the representation of any State in the Senate,\
the executive authority of each State shall issue writs of election to\
fill such vacancies: _Provided_ that the legislature of any State may\
empower the executive thereof to make temporary appointments until the\
people fill the vacancies by election as the legislature may direct.\
\
This amendment shall not be so construed as to effect the election or\
term of any senator chosen before it becomes valid as part of the\
Constitution.\
\
\
ARTICLE XVIII[18]\
\
SECTION 1. After one year from the ratification of this article the\
manufacture, sale, or transportation of intoxicating liquors within, the\
importation thereof into, or the exportation thereof from the United\
States and all territory subject to the jurisdiction thereof for\
beverage purposes is hereby prohibited.\
\
SECTION 2. The Congress and the several States shall have concurrent\
power to enforce this article by appropriate legislation.\
\
SECTION 3. This article shall be inoperative unless it shall have been\
ratified as an amendment to the Constitution by the legislatures of the\
several States, as provided in the Constitution, within seven years from\
the date of the submission hereof to the States by the Congress.\
\
\
ARTICLE XIX[19]\
\
The right of citizens of the United States to vote shall not be denied\
or abridged by the United States or any State on account of sex.\
\
The Congress shall have power to enforce this article by appropriate\
legislation.\
\
\
\
POPULATION OF THE UNITED STATES, BY STATES: 1920, 1910, 1900\
\
+---------------------+--------------------------------------------+\
|      STATES         |                  POPULATION                |\
+                     +--------------+--------------+--------------+\
|                     |     1920     |     1910     |     1900     |\
+---------------------+--------------+--------------+--------------+\
|United States        | 105,708,771  |  91,972,266  |  75,994,575  |\
+---------------------+--------------+--------------+--------------+\
|Alabama              |   2,348,174  |   2,138,093  |   1,828,697  |\
|Arizona              |     333,903  |     204,354  |     122,931  |\
|Arkansas             |   1,752,204  |   1,574,449  |   1,311,564  |\
|California           |   3,426,861  |   2,377,549  |   1,485,053  |\
|Colorado             |     939,629  |     799,024  |     539,700  |\
|Connecticut          |   1,380,631  |   1,114,756  |     908,420  |\
|Delaware             |     223,003  |     202,322  |     184,735  |\
|District of Columbia |     437,571  |     331,069  |     278,718  |\
|Florida              |     968,470  |     752,619  |     528,542  |\
|Georgia              |   2,895,832  |   2,609,121  |   2,216,331  |\
|Idaho                |     431,866  |     325,594  |     161,772  |\
|Illinois             |   6,485,280  |   5,638,591  |   4,821,550  |\
|Indiana              |   2,930,390  |   2,700,876  |   2,516,462  |\
|Iowa                 |   2,404,021  |   2,224,771  |   2,231,853  |\
|Kansas               |   1,769,257  |   1,690,949  |   1,470,495  |\
|Kentucky             |   2,416,630  |   2,289,905  |   2,147,174  |\
|Louisiana            |   1,798,509  |   1,656,388  |   1,381,625  |\
|Maine                |     768,014  |     742,371  |     694,466  |\
|Maryland             |   1,449,661  |   1,295,346  |   1,188,044  |\
|Massachusetts        |   3,852,356  |   3,366,416  |   2,805,346  |\
|Michigan             |   3,668,412  |   2,810,173  |   2,420,982  |\
|Minnesota            |   2,387,125  |   2,075,708  |   1,751,394  |\
|Mississippi          |   1,790,618  |   1,797,114  |   1,551,270  |\
|Missouri             |   3,404,055  |   3,293,335  |   3,106,665  |\
|Montana              |     548,889  |     376,053  |     243,329  |\
|Nebraska             |   1,296,372  |   1,192,214  |   1,066,300  |\
|Nevada               |      77,407  |      81,875  |      42,335  |\
|New Hampshire        |     443,407  |     430,572  |     411,588  |\
|New Jersey           |   3,155,900  |   2,537,167  |   1,883,669  |\
|New Mexico           |     360,350  |     327,301  |     195,310  |\
|New York             |  10,384,829  |   9,113,614  |   7,268,894  |\
|North Carolina       |   2,559,123  |   2,206,287  |   1,893,810  |\
|North Dakota         |     645,680  |     577,056  |     319,146  |\
|Ohio                 |   5,759,394  |   4,767,121  |   4,157,545  |\
|Oklahoma             |   2,028,283  |   1,657,155  |     790,391  |\
|Oregon               |     783,389  |     672,765  |     413,536  |\
|Pennsylvania         |   8,720,017  |   7,665,111  |   6,302,115  |\
|Rhode Island         |     604,397  |     542,610  |     428,556  |\
|South Carolina       |   1,683,724  |   1,515,400  |   1,340,316  |\
|South Dakota         |     636,547  |     583,888  |     401,570  |\
|Tennessee            |   2,337,885  |   2,184,789  |   2,020,616  |\
|Texas                |   4,663,228  |   3,896,542  |   3,048,710  |\
|Utah                 |     449,396  |     373,351  |     276,749  |\
|Vermont              |     352,428  |     355,956  |     343,641  |\
|Virginia             |   2,309,187  |   2,061,612  |   1,854,184  |\
|Washington           |   1,356,621  |   1,141,990  |     518,103  |\
|West Virginia        |   1,463,701  |   1,221,119  |     958,800  |\
|Wisconsin            |   2,632,067  |   2,333,860  |   2,069,042  |\
|Wyoming              |     194,402  |     145,965  |      92,531  |\
+---------------------+--------------+--------------+--------------+\
\
FOOTNOTES:\
\
[3] Partly superseded by the 14th Amendment, p. 639.\
\
[4] See the 17th Amendment, p. 641.\
\
[5] _Ibid._, p. 641.\
\
[6] See the 16th Amendment, p. 640.\
\
[7] The following paragraph was in force only from 1788 to 1803.\
\
[8] Superseded by the 12th Amendment, p. 638.\
\
[9] See the 11th Amendment, p. 638.\
\
[10] First ten amendments proposed by Congress, Sept. 25, 1789.\
Proclaimed to be in force Dec. 15, 1791.\
\
[11] Proposed Sept. 5, 1794. Declared in force January 8, 1798.\
\
[12] Adopted in 1804.\
\
[13] Adopted in 1865.\
\
[14] Adopted in 1868.\
\
[15] Proposed February 27, 1869. Declared in force March 30, 1870.\
\
[16] Passed July, 1909; proclaimed February 25, 1913.\
\
[17] Passed May, 1912, in lieu of paragraph one, Section 3, Article I,\
of the Constitution and so much of paragraph two of the same Section as\
relates to the filling of vacancies; proclaimed May 31, 1913.\
\
[18] Ratified January 16, 1919.\
\
[19] Ratified August 26, 1920.\
\
\
\
\
APPENDIX\
\
TABLE OF PRESIDENTS\
\
NAME                    STATE  PARTY     YEAR IN    VICE-PRESIDENT\
                                         OFFICE\
1 George Washington      Va.    Fed.    1789-1797   John Adams\
2 John Adams             Mass.  Fed.    1797-1801   Thomas Jefferson\
3 Thomas Jefferson       Va.    Rep.    1801-1809   Aaron Burr\
                                                    George Clinton\
4 James Madison          Va.    Rep.    1809-1817   George Clinton\
                                                    Elbridge Gerry\
5 James Monroe           Va.    Rep.    1817-1825   Daniel D. Tompkins\
6 John Q. Adams          Mass.  Rep.    1825-1829   John C. Calhoun\
7 Andrew Jackson         Tenn.  Dem.    1829-1837   John C. Calhoun\
                                                    Martin Van Buren\
8 Martin Van Buren       N.Y.   Dem.    1837-1841   Richard M. Johnson\
9 Wm. H. Harrison        Ohio   Whig    1841-1841   John Tyler\
10 John Tyler[20]        Va.    Whig    1841-1845\
11 James K. Polk         Tenn.  Dem.    1845-1849   George M. Dallas\
12 Zachary Taylor        La.    Whig    1849-1850   Millard Fillmore\
13 Millard Fillmore[20]  N.Y.   Whig    1850-1853\
14 Franklin Pierce       N.H.   Dem.    1853-1857   William R. King\
15 James Buchanan        Pa.    Dem.    1857-1861   J.C. Breckinridge\
16 Abraham Lincoln       Ill.   Rep.    1861-1865   Hannibal Hamlin\
                                                    Andrew Johnson\
17 Andrew Johnson[20]    Tenn.  Rep.    1865-1869\
18 Ulysses S. Grant      Ill.   Rep.    1869-1877   Schuyler Colfax\
                                                    Henry Wilson\
19 Rutherford B. Hayes   Ohio   Rep.    1877-1881   Wm. A. Wheeler\
20 James A. Garfield     Ohio   Rep.    1881-1881   Chester A. Arthur\
21 Chester A. Arthur[20] N.Y.   Rep.    1881-1885\
22 Grover Cleveland      N.Y.   Dem.    1885-1889   Thomas A. Hendricks\
23 Benjamin Harrison     Ind.   Rep.    1889-1893   Levi P. Morton\
24 Grover Cleveland      N.Y.   Dem.    1893-1897   Adlai E. Stevenson\
25 William McKinley      Ohio   Rep.    1897-1901   Garrett A. Hobart\
                                                    Theodore Roosevelt\
26 Theodore Roosevelt[20]N.Y.   Rep.    1901-1909   Chas. W. Fairbanks\
27 William H. Taft       Ohio   Rep.    1909-1913   James S. Sherman\
28 Woodrow Wilson        N.J.   Dem.    1913-1921   Thomas R. Marshall\
29 Warren G. Harding     Ohio   Rep.    1921-       Calvin Coolidge\
\
\
FOOTNOTES:\
\
[20] Promoted from the vice-presidency on the death of the president.\
\
POPULATION OF THE OUTLYING POSSESSIONS: 1920 AND 1910\
\
----------------------------------------+--------------+---------------\
                AREA                    |     1920     |     1910\
----------------------------------------+--------------+---------------\
United States with outlying possessions |117,857,509   | 101,146,530\
                                        +--------------+---------------\
Continental United States               |105,708,771   | 91,972,266\
Outlying Possessions                    | 12,148,738   |  9,174,264\
                                        +--------------|---------------\
  Alaska                                |     54,899   |     64,356\
  American Samoa                        |      8,056   |      7,251[21]\
  Guam                                  |     13,275   |     11,806\
  Hawaii                                |    255,912   |    191,909\
  Panama Canal Zone                     |     22,858   |     62,810[21]\
  Porto Rico                            |  1,299,809   |  1,118,012\
  Military  and  naval,  etc.,  service |              |\
    abroad                              |    117,238   |     55,608\
  Philippine Islands                    |10,350,640[22]|  7,635,426[23]\
  Virgin Islands of the United States   |    26,051[24]|     27,086[25]\
----------------------------------------+--------------+---------------\
\
FOOTNOTES:\
\
[21] Population in 1912.\
\
[22] Population in 1918.\
\
[23] Population in 1903.\
\
[24] Population in 1917.\
\
[25] Population in 1911.\
\
\
\
\
A TOPICAL SYLLABUS\
\
As a result of a wholesome reaction against the purely chronological\
treatment of history, there is now a marked tendency in the direction of\
a purely topical handling of the subject. The topical method, however,\
may also be pushed too far. Each successive stage of any topic can be\
understood only in relation to the forces of the time. For that reason,\
the best results are reached when there is a combination of the\
chronological and the topical methods. It is therefore suggested that\
the teacher first follow the text closely and then review the subject\
with the aid of this topical syllabus. The references are to pages.\
\
\
=Immigration=\
\
     I. Causes: religious (1-2, 4-11, 302), economic (12-17, 302-303),\
        and political (302-303).\
     II. Colonial immigration.\
       1. Diversified character: English, Scotch-Irish, Irish, Jews,\
          Germans and other peoples (6-12).\
       2. Assimilation to an American type; influence of the land\
          system (23-25, 411).\
       3. Enforced immigration: indentured servitude, slavery, etc.\
          (13-17).\
     III. Immigration between 1789-1890.\
       1. Nationalities: English, Irish, Germans, and Scandinavians\
          (278, 302-303).\
       2. Relations to American life (432-433, 445).\
     IV. Immigration and immigration questions after 1890.\
       1. Change in nationalities (410-411).\
       2. Changes in economic opportunities (411).\
       3. Problems of congestion and assimilation (410).\
       4. Relations to labor and illiteracy (582-586).\
       5. Oriental immigration (583).\
       6. The restriction of immigration (583-585).\
\
=Expansion of the United States=\
\
     I. Territorial growth.\
       1. Territory of the United States in 1783 (134 and color map).\
       2. Louisiana purchase, 1803 (188-193 and color map).\
       3. Florida purchase, 1819 (204).\
       4. Annexation of Texas, 1845 (278-281).\
       5. Acquisition of Arizona, New Mexico, California, and other\
          territory at close of Mexican War, 1848 (282-283).\
       6. The Gadsden purchase, 1853 (283).\
       7. Settlement of the Oregon boundary question, 1846 (284-286).\
       8. Purchase of Alaska from Russia, 1867 (479).\
       9. Acquisition of Tutuila in Samoan group, 1899 (481-482).\
       10. Annexation of Hawaii, 1898 (484).\
       11. Acquisition of Porto Rico, the Philippines, and Guam at\
           close of Spanish War, 1898 (493-494).\
       12. Acquisition of Panama Canal strip, 1904 (508-510).\
       13. Purchase of Danish West Indies, 1917 (593).\
       14. Extension of protectorate over Haiti, Santo Domingo, and\
           Nicaragua (593-594).\
     II. Development of colonial self-government.\
       1. Hawaii (485).\
       2. Philippines (516-518).\
       3. Porto Rico (515-516).\
     III. Sea power.\
       1. In American Revolution (118).\
       2. In the War of 1812 (193-201).\
       3. In the Civil War (353-354).\
       4. In the Spanish-American War (492).\
       5. In the Caribbean region (512-519).\
       6. In the Pacific (447-448, 481).\
       7. The role of the American navy (515).\
\
=The Westward Advance of the People=\
\
     I. Beyond the Appalachians.\
       1. Government and land system (217-231).\
       2. The routes (222-224).\
       3. The settlers (221-223, 228-230).\
       4. Relations with the East (230-236).\
     II. Beyond the Mississippi.\
       1. The lower valley (271-273).\
       2. The upper valley (275-276).\
     III. Prairies, plains, and desert.\
       1. Cattle ranges and cowboys (276-278, 431-432).\
       2. The free homesteads (432-433).\
       3. Irrigation (434-436, 523-525).\
     IV. The Far West.\
       1. Peculiarities of the West (433-440).\
       2. The railways (425-431).\
       3. Relations to the East and Europe (443-447).\
       4. American power in the Pacific (447-449).\
\
=The Wars of American History=\
\
     I. Indian wars (57-59).\
     II. Early colonial wars: King William's, Queen Anne's, and King\
         George's (59).\
     III. French and Indian War (Seven Years' War), 1754-1763 (59-61).\
     IV. Revolutionary War, 1775-1783 (99-135).\
     V. The War of 1812, 1812-1815 (193-201).\
     VI. The Mexican War, 1845-1848 (276-284).\
     VII. The Civil War, 1861-1865 (344-375).\
     VIII. The Spanish War, 1898 (485-497).\
     IX. The World War, 1914-1918 [American participation, 1917-1918]\
         (596-625).\
\
=Government=\
\
     I. Development of the American system of government.\
       1. Origin and growth of state government.\
         _a._ The trading corporation (2-4), religious congregation\
              (4-5), and proprietary system (5-6).\
         _b._ Government of the colonies (48-53).\
         _c._ Formation of the first state constitutions (108-110).\
         _d._ The admission of new states (_see_ Index under each\
              state).\
         _e._ Influence of Jacksonian Democracy (238-247).\
         _f._ Growth of manhood suffrage (238-244).\
         _g._ Nullification and state sovereignty (180-182, 251-257).\
         _h._ The doctrine of secession (345-346).\
         _i._ Effects of the Civil War on position of states (366,\
              369-375).\
         _j._ Political reform--direct government--initiative,\
              referendum, and recall (540-544).\
       2. Origin and growth of national government.\
         _a._ British imperial control over the colonies (64-72).\
         _b._ Attempts at intercolonial union--New England\
              Confederation, Albany plan (61-62).\
         _c._ The Stamp Act Congress (85-86).\
         _d._ The Continental Congresses (99-101).\
         _e._ The Articles of Confederation (110-111, 139-143).\
         _f._ The formation of the federal Constitution (143-160).\
         _g._ Development of the federal Constitution.\
           (1) Amendments 1-11--rights of persons and states (163).\
           (2) Twelfth amendment--election of President (184, note).\
           (3) Amendments 13-15--Civil War settlement (358, 366, 369,\
               370, 374, 375).\
           (4) Sixteenth amendment--income tax (528-529).\
           (5) Seventeenth amendment--election of Senators (541-542).\
           (6) Eighteenth amendment--prohibition (591-592).\
           (7) Nineteenth amendment--woman suffrage (563-568).\
       3. Development of the suffrage.\
         _a._ Colonial restrictions (51-52).\
         _b._ Provisions of the first state constitutions\
              (110, 238-240).\
         _c._ Position under federal Constitution of 1787 (149).\
         _d._ Extension of manhood suffrage (241-244).\
         _e._ Extension and limitation of negro suffrage (373-375,\
              382-387).\
         _f._ Woman suffrage (560-568).\
     II. Relation of government to economic and social welfare.\
       1. Debt and currency.\
         _a._ Colonial paper money (80).\
         _b._ Revolutionary currency and debt (125-127).\
         _c._ Disorders under Articles of Confederation (140-141).\
         _d._ Powers of Congress under the Constitution to coin money\
              (_see_ Constitution in the Appendix).\
         _e._ First United States bank notes (167).\
         _f._ Second United States bank notes (257).\
         _g._ State bank notes (258).\
         _h._ Civil War greenbacks and specie payment (352-353, 454).\
         _i._ The Civil War debt (252).\
         _j._ Notes of National Banks under act of 1864 (369).\
         _k._ Demonetization of silver and silver legislation\
              (452-458).\
         _l._ The gold standard (472).\
         _m._ The federal reserve notes (589).\
         _n._ Liberty bonds (606).\
       2. Banking systems.\
         _a._ The first United States bank (167).\
         _b._ The second United States bank--origin and destruction\
              (203, 257-259).\
         _c._ United States treasury system (263).\
         _d._ State banks (258).\
         _e._ The national banking system of 1864 (369).\
         _f._ Services of banks (407-409).\
         _g._ Federal reserve system (589).\
       3. The tariff.\
         _a._ British colonial system (69-72).\
         _b._ Disorders under Articles of Confederation (140).\
         _c._ The first tariff under the Constitution (150, 167-168).\
         _d._ Development of the tariff, 1816-1832 (252-254).\
         _f._ Tariff and nullification (254-256).\
         _g._ Development to the Civil War--attitude of South and West\
              (264, 309-314, 357).\
         _h._ Republicans and Civil War tariffs (352, 367).\
         _i._ Revival of the tariff controversy under Cleveland (422).\
         _j._ Tariff legislation after 1890--McKinley bill (422),\
              Wilson bill (459), Dingley bill (472), Payne-Aldrich bill\
              (528), Underwood bill (588).\
       4. Foreign and domestic commerce and transportation\
          (_see_ Tariff, Immigration, and Foreign Relations).\
         _a._ British imperial regulations (69-72).\
         _b._ Confusion under Articles of Confederation (140).\
         _c._ Provisions of federal Constitution (150).\
         _d._ Internal improvements--aid to roads, canals, etc.\
              (230-236).\
         _e._ Aid to railways (403).\
         _f._ Service of railways (402).\
         _g._ Regulation of railways (460-461, 547-548).\
         _h._ Control of trusts and corporations (461-462, 589-590).\
       5. Land and natural resources.\
         _a._ British control over lands (80).\
         _b._ Early federal land measures (219-221).\
         _c._ The Homestead act (368, 432-445).\
         _d._ Irrigation and reclamation (434-436, 523-525).\
         _e._ Conservation of natural resources (523-526).\
       6. Legislation advancing human rights and general welfare\
          (_see_ Suffrage).\
         _a._ Abolition of slavery: civil and political rights of\
              negroes (357-358, 373-375).\
         _b._ Extension of civil and political rights to women\
              (554-568).\
         _c._ Legislation relative to labor conditions (549-551,\
              579-581, 590-591).\
         _d._ Control of public utilities (547-549).\
         _e._ Social reform and the war on poverty (549-551).\
         _f._ Taxation and equality of opportunity (551-552).\
\
=Political Parties and Political Issues=\
\
     I. The Federalists _versus_ the Anti-Federalists [Jeffersonian\
        Republicans] from about 1790 to about 1816 (168-208, 201-203).\
       1. Federalist leaders: Hamilton, John Adams, John Marshall,\
          Robert Morris.\
       2. Anti-Federalist leaders: Jefferson, Madison, Monroe.\
       3. Issues: funding the debt, assumption of state debts, first\
          United States bank, taxation, tariff, strong central\
          government _versus_ states' rights, and the Alien and\
          Sedition acts.\
     II. Era of "Good Feeling" from about 1816 to about 1824, a period\
         of no organized party opposition (248).\
     III. The Democrats [former Jeffersonian Republicans] _versus_ the\
          Whigs [or National Republicans] from about 1832 to 1856\
         (238-265, 276-290, 324-334).\
       1. Democratic leaders: Jackson, Van Buren, Calhoun, Benton.\
\
       2. Whig leaders: Webster and Clay.\
       3. Issues: second United States bank, tariff, nullification,\
          Texas, internal improvements, and disposition of Western\
          lands.\
     IV. The Democrats _versus_ the Republicans from about 1856 to the\
         present time (334-377, 388-389, 412-422, 451-475, 489-534,\
         588-620).\
       1. Democratic leaders: Jefferson Davis, Tilden, Cleveland,\
          Bryan, and Wilson.\
       2. Republican leaders: Lincoln, Blaine, McKinley, Roosevelt.\
       3. Issues: Civil War and reconstruction, currency, tariff,\
          taxation, trusts, railways, foreign policies, imperialism,\
          labor questions, and policies with regard to land and\
          conservation.\
     V. Minor political parties.\
       1. Before the Civil War: Free Soil (319) and Labor Parties\
          (306-307).\
       2. Since the Civil War: Greenback (463-464), Populist (464),\
          Liberal Republican (420), Socialistic (577-579), Progressive\
         (531-534, 602-603).\
\
=The Economic Development of the United States=\
\
     I. The land and natural resources.\
       1. The colonial land system: freehold, plantation, and manor\
          (20-25).\
       2. Development of the freehold in the West (220-221, 228-230).\
       3. The Homestead act and its results (368, 432-433).\
       4. The cattle range and cowboy (431-432).\
       5. Disappearance of free land (443-445).\
       6. Irrigation and reclamation (434-436).\
       7. Movement for the conservation of resources (523-526).\
     II. Industry.\
       1. The rise of local and domestic industries (28-32).\
       2. British restrictions on American enterprise (67-69, 70-72).\
       3. Protective tariffs (see above, 648-649).\
       4. Development of industry previous to the Civil War (295-307).\
       5. Great progress of industry after the war (401-406).\
       6. Rise and growth of trusts and combinations (406-412,\
          472-474).\
     III. Commerce and transportation.\
       1. Extent of colonial trade and commerce (32-35).\
       2. British regulation (69-70).\
       3. Effects of the Revolution and the Constitution\
          (139-140, 154).\
       4. Growth of American shipping (195-196).\
       5. Waterways and canals (230-236).\
       6. Rise and extension of the railway system (298-300).\
       7. Growth of American foreign trade (445-449).\
     IV. Rise of organized labor.\
       1. Early phases before the Civil War: local unions, city\
          federations, and national unions in specific trades\
          (304-307).\
       2. The National Trade Union, 1866-1872 (574-575).\
       3. The Knights of Labor (575-576).\
       4. The American Federation of Labor (573-574).\
         _a._ Policies of the Federation (576-577).\
         _b._ Relations to politics (579-581).\
         _c._ Contests with socialists and radicals (577-579).\
         _d._ Problems of immigration (582-585).\
       5. The relations of capital and labor.\
         _a._ The corporation and labor (410, 570-571).\
         _b._ Company unions and profit-sharing (571-572).\
         _c._ Welfare work (573).\
         _d._ Strikes (465, 526, 580-581).\
         _e._ Arbitration (581-582).\
\
=American Foreign Relations=\
\
     I. Colonial period.\
       1. Indian relations (57-59).\
       2. French relations (59-61).\
     II. Period of conflict and independence.\
       1. Relations with Great Britain (77-108, 116-125, 132-135).\
       2. Establishment of connections with European powers (128).\
       3. The French alliance of 1778 (128-130).\
       4. Assistance of Holland and Spain (130).\
     III. Relations with Great Britain since 1783.\
       1. Commercial settlement in Jay treaty of 1794 (177-178).\
       2. Questions arising out of European wars [1793-1801]\
          (176-177, 180).\
       3. Blockade and embargo problems (193-199).\
       4. War of 1812 (199-201).\
       5. Monroe Doctrine and Holy Alliance (205-207).\
       6. Maine boundary--Webster-Ashburton treaty (265).\
       7. Oregon boundary (284-286).\
       8. Attitude of Great Britain during Civil War (354-355).\
       9. Arbitration of _Alabama_ claims (480-481).\
       10. The Samoan question (481-482)\
       11. The Venezuelan question (482-484).\
       12. British policy during Spanish-American War (496-497).\
       13. Controversy over blockade, 1914-1917 (598-600).\
       14. The World War (603-620).\
     IV. Relations with France.\
       1. The colonial wars (59-61).\
       2. The French alliance of 1778 (128-130).\
       3. Controversies over the French Revolution (128-130).\
       4. Commercial questions arising out of the European wars\
          (176-177, 180, 193-199).\
       5. Attitude of Napoleon III toward the Civil War (354-355).\
       6. The Mexican entanglement (478-479).\
       7. The World War (596-620).\
     V. Relations with Germany.\
       1. Negotiations with Frederick, king of Prussia (128).\
       2. The Samoan controversy (481-482).\
       3. Spanish-American War (491).\
       4. The Venezuelan controversy (512).\
       5. The World War (596-620).\
     VI. Relations with the Orient.\
       1. Early trading connections (486-487).\
       2. The opening of China (447).\
       3. The opening of Japan (448).\
       4. The Boxer rebellion and the "open door" policy (499-502).\
       5. Roosevelt and the close of the Russo-Japanese War (511).\
       6. The Oriental immigration question (583-584).\
     VII. The United States and Latin America.\
       1. Mexican relations.\
         _a._ Mexican independence and the Monroe Doctrine (205-207).\
         _b._ Mexico and French intervention--policy of the United\
              States (478-479).\
         _c._ The overthrow of Diaz (1911) and recent questions\
              (594-596).\
       2. Cuban relations.\
         _a._ Slavery and the "Ostend Manifesto" (485-486).\
         _b._ The revolutionary period, 1867-1877 (487).\
         _c._ The revival of revolution (487-491).\
         _d._ American intervention and the Spanish War (491-496).\
         _e._ The Platt amendment and American protection (518-519).\
       3. Caribbean and other relations.\
         _a._ Acquisition of Porto Rico (493).\
         _b._ The acquisition of the Panama Canal strip (508-510).\
         _c._ Purchase of Danish West Indies (593).\
         _d._ Venezuelan controversies (482-484, 512).\
         _e._ Extension of protectorate over Haiti, Santo Domingo,\
              and Nicaragua (513-514, 592-594).\
\
\
\
\
INDEX\
\
\
Abolition, 318, 331\
\
Adams, Abigail, 556\
\
Adams, John, 97, 128, 179ff.\
\
Adams, J.Q., 247, 319\
\
Adams, Samuel, 90, 99, 108\
\
Adamson law, 590\
\
Aguinaldo, 497\
\
Alabama, admission, 227\
\
_Alabama_ claims, 480\
\
Alamance, battle, 92\
\
Alamo, 280\
\
Alaska, purchase, 479\
\
Albany, plan of union, 62\
\
Algonquins, 57\
\
Alien law, 180\
\
Amendment, method of, 156\
\
Amendments to federal Constitution: first eleven, 163\
  twelfth, 184, note\
  thirteenth, 358\
  fourteenth, 366, 369, 387\
  fifteenth, 358\
  sixteenth, 528\
  seventeenth, 542\
  eighteenth, 591\
  nineteenth, 563ff.\
\
American expeditionary force, 610\
\
American  Federation  of  Labor,  573, 608\
\
Americanization, 585\
\
Amnesty, for Confederates, 383\
\
Andros, 65\
\
Annapolis, convention, 144\
\
Antietam, 357\
\
Anti-Federalists, 169\
\
Anti-slavery. _See_ Abolition\
\
Anthony, Susan, 564\
\
Appomattox, 363\
\
Arbitration:  international,  480,  514, 617\
  labor disputes, 582\
\
Arizona, admission, 443\
\
Arkansas, admission, 272\
\
Arnold, Benedict, 114, 120\
\
Articles of Confederation, 110, 139ff., 146\
\
Ashburton, treaty, 265\
\
Assembly, colonial, 49ff., 89ff.\
\
Assumption, 164ff.\
\
Atlanta, 361\
\
Australian ballot, 540\
\
\
Bacon, Nathaniel, 58\
\
Ballot:  Australian, 540\
  short, 544\
\
Baltimore, Lord, 6\
\
Bank: first U.S., 167\
  second, 203, 257ff.\
\
Banking system:  state, 300\
  U.S. national, 369\
  services of, 407\
  _See also_ Federal reserve\
\
Barry, John, 118\
\
Bastille, 172\
\
Bell, John, 341\
\
Belleau Wood, 611\
\
Berlin decree, 194\
\
Blockade: by England and France, 193ff.\
  Southern ports, 353\
  law and practice in 1914, 598ff.\
\
Bond servants, 13ff.\
\
Boone, Daniel, 28, 218\
\
Boston:  massacre, 91\
  evacuation, 116\
  port bill, 94\
\
Bowdoin, Governor, 142\
\
Boxer rebellion, 499\
\
Brandywine, 129\
\
Breckinridge, J.C., 340\
\
Bright, John, 355\
\
Brown, John, 338\
\
Brown University, 45\
\
Bryan, W.J., 468ff., 495, 502, 503, 527\
\
Buchanan, James, 335, 368\
\
Budget system, 529\
\
Bull Run, 350\
\
Bunker Hill, 102\
\
Burgoyne, General, 116, 118, 130\
\
Burke, Edmund, 87, 96ff., 132, 175\
\
Burr, Aaron, 183, 231\
\
Business. _See_  Industry\
\
\
Calhoun, J.C., 198ff., 203, 208, 281, 321, 328\
\
California, 286ff.\
\
Canada, 61, 114, 530\
\
Canals, 233, 298, 508\
\
Canning, British premier, 206\
\
Cannon, J.G., 530\
\
Cantigny, 611\
\
Caribbean, 479\
\
Carpet baggers, 373\
\
Cattle ranger, 431ff.\
\
Caucus, 245\
\
Censorship. _See_ Newspapers\
\
Charles I, 3\
\
Charles II, 65\
\
Charleston, 36, 116\
\
Charters, colonial, 2ff., 41\
\
Chase, Justice, 187\
\
Chateau-Thierry, 611\
\
Checks and balances, 153\
\
_Chesapeake_, the, 195\
\
Chickamauga, 361\
\
Child labor law, 591\
\
China, 447, 499ff.\
\
Chinese labor, 583\
\
Churches, colonial, 39ff., 42, 43\
\
Cities, 35, 36, 300ff., 395, 410, 544\
\
City manager plan, 545\
\
Civil liberty, 358ff., 561\
\
Civil service, 419, 536, 538ff.\
\
Clarendon, Lord, 6\
\
Clark, G.R., 116, 218\
\
Clay, Henry, 198, 203, 248, 261, 328\
\
Clayton anti-trust act, 489\
\
Clergy. _See_ Churches\
\
Cleveland, Grover, 421, 465, 482, 484, 489, 582\
\
Clinton, Sir Henry, 119\
\
Colorado, admission, 441\
\
Combination. _See_ Trusts\
\
Commerce, colonial, 33ff.\
  disorders after 1781, 140\
  Constitutional provisions on, 154\
  Napoleonic wars, 176, 193ff.\
  domestic growth of, 307\
  congressional regulation of, 460ff., 547\
  _See also_ Trusts and Railways\
\
Commission government, 544\
\
Committees of correspondence, 108\
\
_Commonsense_, pamphlet, 103\
\
Communism, colonial, 20f.\
\
Company, trading, 2f.\
\
Compromises: of Constitution, 148, 150, 151\
  Missouri, 325, 332\
  of 1850, 328ff.\
  Crittenden, 350\
\
Conciliation, with England, 131\
\
Concord, battle, 100\
\
Confederacy, Southern, 346ff.\
\
Confederation: New England, 61f.\
  _See also_ Articles of\
\
Congregation, religious, 4\
\
Congress:  stamp act, 85\
  continental, 99ff.\
  under Articles, 139f.\
  under Constitution, 152\
  powers of, 153\
\
Connecticut: founded, 4ff.\
  self-government, 49\
  _See also_ Suffrage\
  constitutions, state\
\
Conservation, 523ff.\
\
Constitution: formation of, 143ff.\
  _See also_ Amendment\
\
_Constitution_, the, 200\
\
Constitutions, state, 109ff., 238ff., 385ff.\
\
Constitutional union party, 340\
\
Contract labor law, 584\
\
Convention: 1787, 144ff.\
  nominating, 405\
\
Convicts, colonial, 15\
\
Conway Cabal, 120\
\
Cornwallis, General, 116, 119, 131\
\
Corporation and labor, 571. _See also_ Trusts\
\
Cotton. _See_ Planting system\
\
Cowboy, 431ff.\
\
Cowpens, battle, 116\
\
Cox, J.M., 619\
\
_Crisis, The_, pamphlet, 115\
\
Crittenden Compromise, 350\
\
Cuba, 485ff., 518\
\
Cumberland Gap, 223\
\
Currency. _See_ Banking\
\
\
Danish West Indies, purchased, 593\
\
Dartmouth College, 45\
\
Daughters of liberty, 84\
\
Davis, Jefferson, 346ff.\
\
Deane, Silas, 128\
\
Debs, E.V., 465, 534\
\
Debt, national, 164ff.\
\
Decatur, Commodore, 477\
\
Declaration of Independence, 101ff.\
\
Defense, national, 154\
\
De Kalb, 121\
\
Delaware, 3, 49\
\
De Lome affair, 490\
\
Democratic party, name assumed, 260\
  _See also_ Anti-Federalists\
\
Dewey, Admiral, 492\
\
Diplomacy: of the Revolution, 127ff.\
  Civil War, 354\
\
Domestic industry, 28\
\
Donelson, Fort, 361\
\
Dorr Rebellion, 243\
\
Douglas, Stephen A., 333, 337, 368\
\
Draft: Civil War, 351\
  World War, 605\
\
Draft riots, 351\
\
Dred Scott case, 335, 338\
\
Drug act, 523\
\
Duquesne, Fort, 60\
\
Dutch, 3, 12\
\
\
East India Company, 93\
\
Education, 43ff., 557, 591\
\
Electors, popular election of, 245\
\
Elkins law, 547\
\
Emancipation, 357ff.\
\
Embargo acts, 186ff.\
\
England: Colonial policy of, 64ff.\
  Revolutionary War, 99ff.\
  Jay treaty, 177\
  War of 1812, 198ff.\
  Monroe Doctrine, 206\
  Ashburton treaty, 265\
  Civil War, 354\
  _Alabama_ claims, 480\
  Samoa, 481\
  Venezuela question, 482\
  Spanish War, 496\
  World War, 596ff.\
\
Erie Canal, 233\
\
Esch-Cummins bill, 582\
\
Espionage act, 607\
\
Excess profits tax, 606\
\
Executive, federal, plans for, 151\
\
Expunging resolution, 260\
\
\
Farm loan act, 589\
\
Federal reserve act, 589\
\
Federal trade commission, 590\
\
_Federalist_, the, 158\
\
Federalists, 168ff., 201ff.\
\
Feudal elements in colonies, 21f.\
\
Filipino revolt. _See_ Philippines\
\
Fillmore, President, 485\
\
Finances: colonial, 64\
  revolutionary, 125ff.\
  disorders, 140\
  Civil War, 347, 352ff.\
  World War, 606\
  _See also_ Banking\
\
Fishing industry, 31\
\
Fleet, world tour, 515\
\
Florida, 134, 204\
\
Foch, General, 611\
\
Food and fuel law, 607\
\
Force bills, 384 ff., 375\
\
Forests, national, 525ff.\
\
Fourteen points, 605\
\
Fox, C.J., 132\
\
France: colonization, 59ff.\
  French and Indian War, 60ff.\
  American Revolution, 116, 123, 128ff.\
  French Revolution, 165ff.\
  Quarrel with, 180\
  Napoleonic wars, 193ff.\
  Louisiana purchase, 190\
  French Revolution of 1830, 266\
  Civil War, 354\
  Mexican affair, 478\
  World War, 596ff.\
\
Franchises, utility, 548\
\
Franklin, Benjamin, 45, 62, 82, 86, 128, 134\
\
Freedmen. _See_ Negro\
\
Freehold. _See_ Land\
\
Free-soil party, 319\
\
Fremont, J.C., 288, 334\
\
French. _See_ France\
\
Friends, the, 5\
\
Frontier. _See_ Land\
\
Fugitive slave act, 329\
\
Fulton, Robert, 231, 234\
\
Fundamental articles, 5\
\
Fundamental orders, 5\
\
\
Gage, General, 95, 100\
\
Garfield, President, 416\
\
Garrison, William Lloyd, 318\
\
_Gaspee_, the, 92\
\
Gates, General, 116, 120, 131\
\
Genet, 177\
\
George I, 66\
\
George II, 4, 66, 82\
\
George III, 77ff.\
\
Georgia: founded, 4\
  royal province, 49\
  state constitution, 109\
  _See also_ Secession\
\
Germans: colonial immigration, 9ff.\
  in Revolutionary War, 102ff.\
  later immigration, 303\
\
Germany: Samoa, 481\
  Venezuela affair, 512\
  World War, 596f.\
\
Gerry, Elbridge, 148\
\
Gettysburg, 362\
\
Gibbon, Edward, 133\
\
Gold: discovery, 288\
  standard, 466, 472\
\
Gompers, Samuel, 573, 608\
\
Governor, royal, 49ff.\
\
Grandfather clause, 386f.\
\
Grangers, 460ff.\
\
Grant, General, 361, 416, 480, 487\
\
Great Britain. _See_ England\
\
Greeley, Horace, 420\
\
Greenbacks, 454ff.\
\
Greenbackers, 462ff.\
\
Greene, General, 117, 120\
\
Grenville, 79ff.\
\
Guilford, battle, 117\
\
\
Habeas corpus, 358\
\
Hague conferences, 514\
\
Haiti, 593\
\
Hamilton, Alexander, 95, 143, 158, 162, 168ff., 231\
\
Harding, W.G., 389, 619\
\
Harlem Heights, battle, 114\
\
Harper's Ferry, 339\
\
Harrison, Benjamin, 422, 484\
\
Harrison, W.H., 198, 263f.\
\
Hartford convention, 201ff., 238\
\
Harvard, 44\
\
Hawaii, 484f.\
\
Hay, John, 477, 500ff.\
\
Hayne, Robert, 256\
\
Hays, President, 416f.\
\
Henry, Patrick, 85\
\
Hepburn act, 523\
\
Hill, James J., 429\
\
Holland, 130\
\
Holy Alliance, 205\
\
Homestead act, 368, 432\
\
Hooker, Thomas, 5\
\
Houston, Sam, 279ff.\
\
Howe, General, 118\
\
Hughes, Charles E., 602\
\
Huguenots, 10\
\
Hume, David, 132\
\
Hutchinson, Anne, 5\
\
\
Idaho, admission, 442\
\
Income tax, 459, 466, 528, 588, 606\
\
Inheritance tax, 606\
\
Illinois, admission, 226\
\
Illiteracy, 585\
\
Immigration: colonial, 1-17\
  before Civil War, 302, 367\
  after Civil War, 410ff.\
  problems of, 582ff.\
\
Imperialism, 494ff., 498f., 502ff.\
\
Implied powers, 212\
\
Impressment of seamen, 194\
\
Indentured servants, 13f.\
\
Independence, Declaration of, 107\
\
Indiana, admission, 226\
\
Indians, 57ff., 81, 431\
\
Industry: colonial, 28ff.\
  growth of, 296ff.\
  during Civil War, 366\
  after 1865, 390ff., 401ff., 436ff., 559\
  _See also_ Trusts\
\
Initiative, the, 543\
\
Injunction, 465, 580\
\
Internal improvements, 260, 368\
\
Interstate commerce act, 461, 529\
\
Intolerable acts, 93\
\
Invisible government, 537\
\
Iowa, admission, 275\
\
Irish, 11, 302\
\
Iron. _See_ Industry\
\
Irrigation, 434ff., 523ff.\
\
\
Jackson, Andrew, 201, 204, 246, 280\
\
Jacobins, 174\
\
James I, 3\
\
James II, 65\
\
Jamestown, 3, 21\
\
Japan, relations with, 447, 511, 583\
\
Jay, John, 128, 158, 177\
\
Jefferson, Thomas: Declaration of Independence, 107\
  Secretary of State, 162ff.\
  political leader, 169\
  as President, 183ff.\
  Monroe Doctrine, 206, 231\
\
Jews, migration of, 11\
\
Johnson, Andrew, 365, 368, 371f.\
\
Johnson, Samuel, 132\
\
Joliet, 59\
\
Jones, John Paul, 118\
\
Judiciary: British system, 67\
  federal, 152\
\
\
Kansas, admission, 441\
\
Kansas-Nebraska bill, 333\
\
Kentucky: admission, 224\
  Resolutions, 182\
\
King George's War, 59\
\
King Philip's War, 57\
\
King William's War, 59\
\
King's College (Columbia), 45\
\
Knights of Labor, 575ff.\
\
Kosciusko, 121\
\
Ku Klux Klan, 382\
\
\
Labor:  rise of organized, 304\
  parties, 462ff.\
  question, 521\
  American Federation, 573ff.\
  legislation, 590\
  World War, 608ff.\
\
Lafayette, 121\
\
La Follette, Senator, 531\
\
Land: tenure 20ff.\
  sales restricted, 80\
  Western survey, 219\
  federal sales policy, 220\
  Western tenure, 228\
  disappearance of free, 445\
  new problems, 449\
  _See also_ Homestead act\
\
La Salle, 59\
\
Lawrence, Captain, 200\
\
League of Nations, 616ff.\
\
Le Boeuf, Fort, 59\
\
Lee, General Charles, 131\
\
Lee, R.E., 357\
\
Lewis and Clark expedition, 193\
\
Lexington, battle, 100\
\
Liberal Republicans, 420\
\
Liberty loan, 606\
\
Lincoln: Mexican War, 282\
  Douglas debates, 336f.\
  election, 341\
  Civil War, 344ff.\
  reconstruction, 371\
\
Literacy test, 585\
\
Livingston, R.R., 191\
\
Locke, John, 95\
\
London Company, 3\
\
Long Island, battle, 114\
\
Lords of trade, 67ff.\
\
Louis XVI, 171ff.\
\
Louisiana: ceded to Spain, 61\
  purchase, 190ff.\
  admission, 227\
\
Loyalists. _See_ Tories\
\
_Lusitania_, the, 601ff.\
\
\
McClellan, General, 362, 365\
\
McCulloch _vs._ Maryland, 211\
\
McKinley, William, 422, 467ff., 489ff.\
\
Macaulay, Catherine, 132\
\
Madison, James, 158, 197ff.\
\
Maine, 325\
\
_Maine_, the, 490\
\
Manila Bay, battle, 492\
\
Manors, colonial, 22\
\
Manufactures. _See_ Industry\
\
Marbury _vs._ Madison, 209\
\
Marietta, 220\
\
Marion, Francis, 117, 120\
\
Marquette, 59\
\
Marshall, John, 208ff.\
\
Martineau, Harriet, 267\
\
Maryland, founded, 6, 49, 109, 239, 242\
\
Massachusetts: founded, 3ff.\
  _See also_ Immigration, Royal province, Industry, Revolutionary War,\
     Constitutions, state, Suffrage, Commerce, and Industry\
\
Massachusetts Bay Company, 3\
  founded, 3ff.\
  _See also_ Immigration, Royal province\
\
_Mayflower_ compact, 4\
\
Mercantile theory, 69\
\
Merchants. _See_ Commerce\
\
_Merrimac_, the, 353\
\
Meuse-Argonne, battle, 612\
\
Mexico: and Texas, 278ff.\
  later relations, 594f.\
\
Michigan, admission, 273\
\
Midnight appointees, 187\
\
Milan Decree, 194\
\
Militia, Revolutionary War, 122\
\
Minimum wages, 551\
\
Minnesota, admission, 275\
\
Mississippi River, and West, 189f.\
\
Missouri Compromise, 207, 227, 271, 325, 332\
\
Molasses act, 71\
\
Money, paper, 80, 126, 155, 369\
\
_Monitor_, the, 353\
\
Monroe, James, 204ff., 191\
\
Monroe Doctrine, 205, 512\
\
Montana, admission, 442\
\
Montgomery, General, 114\
\
Morris, Robert, 127\
\
Mothers' pensions, 551\
\
Mohawks, 57\
\
Muckraking, 536f.\
\
Mugwumps, 420\
\
Municipal ownership, 549\
\
\
Napoleon I, 190\
\
Napoleon III: Civil War, 354f.\
  Mexico, 477\
\
National Labor Union, 574\
\
National road, 232\
\
Nationalism, colonial, 56ff.\
\
Natural rights, 95\
\
Navigation acts, 69\
\
Navy: in Revolution, 188\
  War of 1812, 195\
  Civil War, 353\
  World War, 610.\
  _See also_ Sea Power\
\
Nebraska, admission, 441\
\
Negro: Civil rights, 370ff.\
  in agriculture, 393ff.\
  status of, 396ff.\
  _See also_ Slavery\
\
New England: colonial times, 6ff., 35, 40ff.\
  _See also_ Industry, Suffrage, Commerce, and Wars\
\
New Hampshire: founded, 4ff.\
  _See also_ Immigration, Royal province, Suffrage, and Constitutions,\
    state\
\
New Jersey, founded, 6.\
   _See also_ Immigration, Royal province, Suffrage, and\
     Constitutions, state\
\
Newlands, Senator, 524\
\
New Mexico, admission, 443\
\
New Orleans, 59, 190\
  battle, 201\
\
Newspapers, colonial, 46ff.\
\
New York: founded by Dutch, 3\
  transferred to English, 49\
  _See also_ Dutch, Immigration, Royal province, Commerce, Suffrage,\
    and Constitutions, state\
\
New York City, colonial, 36\
\
Niagara, Fort, 59\
\
Nicaragua protectorate, 594\
\
Non-intercourse act, 196ff.\
\
Non-importation, 84ff., 99\
\
North, Lord, 100, 131, 133\
\
North Carolina: founded, 6.\
  _See also_ Royal province, Immigration, Suffrage, and Constitutions,\
    state\
\
North Dakota, admission, 442\
\
Northwest Ordinance, 219\
\
Nullification, 182, 251ff.\
\
\
Oglethorpe, James, 3\
\
Ohio, admission, 225\
\
Oklahoma, admission, 443\
\
Open door policy, 500\
\
Oregon, 284ff.\
\
Ostend Manifesto, 486\
\
Otis, James, 88, 95f.\
\
\
Pacific, American influence, 447\
\
Paine, Thomas, 103, 115, 175\
\
Panama Canal, 508ff.\
\
Panics: 1837, 262\
  1857, 336\
  1873, 464\
  1893, 465\
\
Parcel post, 529\
\
Parker, A.B., 527\
\
Parties: rise of, 168ff.\
  Federalists, 169ff.\
  Anti-Federalists (Jeffersonian Republicans), 169ff.\
  Democrats, 260\
  Whigs, 260ff.\
  Republicans, 334ff.\
  Liberal Republicans, 420\
  Constitutional union, 340\
  minor parties, 462ff.\
\
Paterson, William, 196ff.\
\
Penn, William, 6\
\
Pennsylvania: founded, 6\
  _See also_ Penn, Germans, Immigration, Industry, Revolutionary War,\
    Constitutions, state, Suffrage\
\
Pennsylvania University, 45\
\
Pensions, soldiers and sailors, 413, 607\
  mothers', 551\
\
Pequots, 57\
\
Perry, O.H., 200\
\
Pershing, General, 610\
\
Philadelphia, 36, 116\
\
Philippines, 492ff., 516ff., 592\
\
Phillips, Wendell, 320\
\
Pierce, Franklin, 295, 330\
\
Pike, Z., 193, 287\
\
Pilgrims, 4\
\
Pinckney, Charles, 148\
\
Pitt, William, 61, 79, 87, 132\
\
Planting system, 22f., 25, 149, 389, 393ff.\
\
Plymouth, 4, 21\
\
Polk, J.K., 265, 285f.\
\
Polygamy, 290f.\
\
Populist party, 464\
\
Porto Rico, 515, 592\
\
Postal savings bank, 529\
\
Preble, Commodore, 196\
\
Press. _See_ Newspapers\
\
Primary, direct, 541\
\
Princeton, battle, 129\
  University, 45\
\
Profit sharing, 572\
\
Progressive party, 531f.\
\
Prohibition, 591f.\
\
Proprietary colonies, 3, 6\
\
Provinces, royal, 49ff.\
\
Public service, 538ff.\
\
Pulaski, 121\
\
Pullman strike, 465\
\
Pure food act, 523\
\
Puritans, 3, 7, 40ff.\
\
\
Quakers, 6ff.\
\
Quartering act, 83\
\
Quebec act, 94\
\
Queen Anne's War, 59\
\
Quit rents, 21f.\
\
\
Radicals, 579\
\
Railways,  298, 402, 425, 460ff., 547, 621\
\
Randolph, Edmund, 146, 147, 162\
\
Ratification, of Constitution, 156ff.\
\
Recall, 543\
\
Reclamation, 523ff.\
\
Reconstruction, 370ff.\
\
Referendum, the, 543\
\
Reign of terror, 174\
\
Republicans: Jeffersonian, 179\
  rise of present party, 334ff.\
  supremacy of, 412ff.\
  _See also_ McKinley, Roosevelt, and Taft\
\
Resumption, 454\
\
Revolution: American, 99ff.\
  French, 171ff.\
  Russian, 619\
\
Rhode Island: founded, 4ff.\
  self-government, 49\
  _See also_ Suffrage\
\
Roosevelt, Theodore, 492, 500ff., 531, 570\
\
Royal province, 49ff.\
\
Russia, 205, 207, 355, 479, 619\
\
Russo-Japanese War, 511f.\
\
\
Saint Mihiel, 612\
\
Samoa, 481\
\
San Jacinto, 280\
\
Santa Fe trail, 287\
\
Santo Domingo, 480, 513, 592\
\
Saratoga, battle, 116, 130\
\
Savannah, 116, 131\
\
Scandinavians, 278\
\
Schools. _See_ Education\
\
Scott, General, 283, 330\
\
Scotch-Irish, 7ff.\
\
Seamen's act, 590\
\
Sea power: American Revolution, 118\
  Napoleonic wars, 193ff.\
  Civil War, 353\
  Caribbean, 593\
  Pacific, 447\
  World War, 610ff.\
\
Secession, 344ff.\
\
Sedition: act of 1798, 180ff., 187\
  of 1918, 608\
\
Senators, popular election, 527, 541ff.\
\
Seven Years' War, 60ff.\
\
Sevier, John, 218\
\
Seward, W.H., 322, 342\
\
Shafter, General, 492\
\
Shays's rebellion, 142\
\
Sherman, General, 361\
\
Sherman: anti-trust law, 461\
  silver act, 458\
\
Shiloh, 361\
\
Shipping. _See_ Commerce\
\
Shipping act, 607\
\
Silver, free, 455ff.\
\
Slavery: colonial, 16f.\
  trade, 150\
  in Northwest, 219\
  decline in North, 316f.\
  growth in South, 320ff.\
  and the Constitution, 324\
  and territories, 325ff.\
  compromises, 350\
  abolished, 357ff.\
\
Smith, Joseph, 290\
\
Socialism, 577ff.\
\
Solid South, 388\
\
Solomon, Hayn, 126\
\
Sons of liberty, 82\
\
South: economic and political views, 309ff.\
  _See also_ Slavery and Planting system, and Reconstruction\
\
South Carolina: founded, 6\
  nullification, 253ff.\
  _See also_ Constitutions, state, Suffrage, Slavery, and Secession\
\
South Dakota, 442\
\
Spain: and Revolution, 130\
  Louisiana, 190\
  Monroe Doctrine, 205\
  Spanish War, 490ff.\
\
Spoils system, 244, 250, 418, 536ff.\
\
Stamp act, 82ff.\
\
Stanton, Elizabeth Cady, 564\
\
States: disorders under Articles of Confederation, 141\
  constitutions, federal limits on, 155\
  position after Civil War, 366ff.\
  _See also_ Suffrage, Nullification, and Secession\
\
Steamboat, 234\
\
Stowe, H.B., 332\
\
Strikes: of 1877, 581\
  Pullman, 581\
  coal, 526\
  _See also_ Labor\
\
Submarine campaign, 600ff.\
\
Suffrage: colonial, 42, 51\
  first state constitutions, 239\
  White manhood, 242\
  Negro, 374ff., 385f.\
  Woman, 110, 562ff.\
\
Sugar act, 81\
\
Sumner, Charles, 319\
\
Sumter, Fort, 350\
\
Swedes, 3, 13\
\
\
Taft, W.H., 527ff.\
\
Tammany Hall, 306, 418\
\
Taney, Chief Justice, 357\
\
Tariff: first, 167\
  of 1816, 203\
  development of, 251ff.\
  abominations, 249, 253\
  nullification, 251\
  of 1842, 264\
  Southern views of, 309ff.\
  of 1857, 337\
  Civil War, 367\
  Wilson bill, 459\
  McKinley bill, 422\
  Dingley bill, 472\
  Payne-Aldrich, 528\
  Underwood, 588\
\
Taxation: and representation, 149\
  and Constitution, 154\
  Civil War, 353\
  and wealth, 522, 551\
  and World War, 606\
\
Tea act, 88\
\
Tea party, 92\
\
Tenement house reform, 549\
\
Tennessee, 28, 224\
\
Territories, Northwest, 219\
  South of the Ohio, 219\
  _See also_ Slavery and Compromise\
\
Texas, 278ff.\
\
Tippecanoe, battle, 198\
\
Tocqueville, 267\
\
Toleration, religious, 42\
\
Tories, colonial, 84\
  in Revolution, 112\
\
Townshend acts, 80, 87\
\
Trade, colonial, 70\
  legislation, 70. _See_ Commerce\
\
Transylvania company, 28\
\
Treasury, independent, 263\
\
Treaties, of 1763, 61\
  alliance with France, 177\
  of 1783 with England, 134\
  Jay, 177, 218\
  Louisiana purchase, 191f.\
  of 1815, 201\
  Ashburton, 265\
  of 1848 with Mexico, 283\
  Washington with England, 481\
  with Spain, 492\
  Versailles (1919), 612ff.\
\
Trenton, battle, 116\
\
Trollope, Mrs., 268\
\
Trusts, 405ff., 461, 472ff., 521, 526, 530\
\
Tweed, W.M., 418\
\
Tyler, President, 264ff., 281, 349\
\
\
"Uncle Tom's Cabin," 332\
\
Union party, 365\
\
Unions. _See_ Labor\
\
Utah, 290ff., 329, 442\
\
Utilities, municipal, 548\
\
\
Vallandigham, 360\
\
Valley Forge, 116, 129\
\
Van Buren, Martin, 262\
\
Venango, Fort, 59\
\
Venezuela, 482ff., 512\
\
Vermont, 223\
\
Vicksburg, 361\
\
Virginia: founded, 3.\
  _See also_ Royal province, Constitutions, state, Planting system,\
    Slavery, Secession, and Immigration\
\
\
Walpole, Sir Robert, 66\
\
Wars: colonial, 57ff.\
  Revolutionary, 99ff.\
  of 1812, 199ff.\
  Mexican, 282ff.\
  Civil, 344ff.\
  Spanish, 490ff.\
  World, 596ff.\
\
Washington: warns French, 60\
  in French war, 63\
  commander-in-chief, 101ff.\
  and movement for Constitution, 142ff.\
  as President, 166ff.\
  Farewell Address, 178\
\
Washington City, 166\
\
Washington State, 442\
\
Webster, 256, 265, 328\
\
Welfare work, 573\
\
Whigs: English, 78\
  colonial, 83\
  rise of party, 260ff., 334, 340\
\
Whisky Rebellion, 171\
\
White Camelia, 382\
\
White Plains, battle, 114\
\
Whitman, Marcus, 284\
\
William and Mary College, 45\
\
Williams, Roger, 5, 42\
\
Wilmot Proviso, 326\
\
Wilson, James, 147\
\
Wilson, Woodrow, election, 533f.\
  administrations, 588ff.\
\
Winthrop, John, 3\
\
Wisconsin, admission, 274\
\
Witchcraft, 41\
\
Wollstonecraft, Mary, 556\
\
Women: colonial, 28\
  Revolutionary War, 124\
  labor, 305\
  education and civil rights, 554ff.\
  suffrage, 562ff.\
\
Workmen's compensation, 549\
\
Writs of assistance, 88\
\
Wyoming, admission, 442\
\
\
X, Y, Z affair, 180\
\
\
Yale, 44\
\
Young, Brigham, 290\
\
\
Zenger, Peter, 48\
\
       *       *       *       *       *\
\
Printed in the United States of America.\
\
       *       *       *       *       *\
\
[Transcriber's notes:\
\
Punctuation normalized in all _Underwood and Underwood, N.Y._\
\
Superscripted letters are denoted with a caret. For example, G^O\
WASHINGTON.\
\
Period added after Mass on verso page. Original read "Mass, U.S.A."\
\
Chapter I, page 19, period added to pp. 55-159 and pp. 242-244.\
\
Chapter IV, page 61 cooperation changed to cooperation twice to match\
rest of text usage. Also on page 620.\
\
Chapter VI, page 121 changed maneuvered to manoevered.\
\
Chapter VIII, page 185, period added to "Vol." Original read "Vol III,"\
\
Chapter X, page 219, changed coordinate to coordinate to reflect rest of\
text usage.\
\
Chapter X, page 234, Italicized habeus corpus to match rest of text.\
\
Chapter XI, page 257 changed reestablished to reestablished to conform\
to rest of text usage.\
\
Chapter XI, page 259 changed reelection to reelection\
\
Chapter XII, page 269 added period after "Vol" Vol. II\
\
Chapter XII, page 270. Title of work reads "_Selected Documents of\
United States History, 1776-1761_". Research shows the document does\
have this title.\
\
Chapter XV, page 351. changed "bout" to "about". "for only about"\
\
Chapter XVI, page 385. changed "provisons" to "provisions".\
\
Chapter XX, page 478. changed "aniversary" to "anniversary".\
\
Chapter XXIV, page 579 word "on" changed to "one" "five commissioners,\
one of whom,"\
\
Topical Syllabus. Missing periods added to normalize punctuation in\
entries such as on page 648 (4) Sixteenth Amendment--income tax\
(528-529).\
\
Appendix, page 631, comma changed to semi-colon on "bills of credit;" to\
match rest of list. Also on "obligation of contracts;"\
\
Index, page 657, changed "Freesoil" to Free-soil to match rest of text\
usage.\
\
Index, page 660, space removed from "396 ff." changed to "status of,\
396ff."\
\
Index, Page 662, added comma to States: disorders under Articles of\
Constitution, 141]\
\
\
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Title: Manual of Surgery\
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\
\
\
                     OXFORD MEDICAL PUBLICATIONS\
\
\
\
                          MANUAL OF SURGERY\
\
\
\
                                  BY\
\
                     ALEXIS THOMSON, F.R.C.S.Ed.\
           _PROFESSOR OF SURGERY, UNIVERSITY OF EDINBURGH_\
                  SURGEON EDINBURGH ROYAL INFIRMARY\
\
                                 AND\
\
                     ALEXANDER MILES, F.R.C.S.Ed.\
                  SURGEON EDINBURGH ROYAL INFIRMARY\
\
\
                             VOLUME FIRST\
                           GENERAL SURGERY\
\
\
                       _SIXTH EDITION REVISED_\
                       _WITH 169 ILLUSTRATIONS_\
\
\
\
                                LONDON\
                 HENRY FROWDE and HODDER & STOUGHTON\
                        THE _LANCET_ BUILDING\
                 1 & 2 BEDFORD STREET, STRAND, W.C.2\
\
\
\
\
\
\
    First Edition                                             1904\
    Second Edition                                            1907\
    Third Edition                                             1909\
    Fourth Edition                                            1911\
      "       "    Second Impression                          1913\
    Fifth Edition                                             1915\
      "       "    Second Impression                          1919\
    Sixth Edition                                             1921\
\
\
\
                     PRINTED IN GREAT BRITAIN BY\
                  MORRISON AND GIBB LTD., EDINBURGH\
\
\
\
\
PREFACE TO SIXTH EDITION\
\
\
Much has happened since this Manual was last revised, and many surgical\
lessons have been learned in the hard school of war. Some may yet have\
to be unlearned, and others have but little bearing on the problems\
presented to the civilian surgeon. Save in its broadest principles, the\
surgery of warfare is a thing apart from the general surgery of civil\
life, and the exhaustive literature now available on every aspect of it\
makes it unnecessary that it should receive detailed consideration in a\
manual for students. In preparing this new edition, therefore, we have\
endeavoured to incorporate only such additions to our knowledge and\
resources as our experience leads us to believe will prove of permanent\
value in civil practice.\
\
For the rest, the text has been revised, condensed, and in places\
rearranged; a number of old illustrations have been discarded, and a\
greater number of new ones added. Descriptions of operative procedures\
have been omitted from the _Manual_, as they are to be found in the\
companion volume on _Operative Surgery_, the third edition of which\
appeared some months ago.\
\
We have retained the Basle anatomical nomenclature, as extended\
experience has confirmed our preference for it. For the convenience of\
readers who still employ the old terms, these are given in brackets\
after the new.\
\
This edition of the _Manual_ appears in three volumes; the first being\
devoted to General Surgery, the other two to Regional Surgery. This\
arrangement has enabled us to deal in a more consecutive manner than\
hitherto with the surgery of the Extremities, including Fractures and\
Dislocations.\
\
We have once more to express our thanks to colleagues in the Edinburgh\
School and to other friends for aiding us in providing new\
illustrations, and for other valuable help, as well as to our publishers\
for their generosity in the matter of illustrations.\
\
EDINBURGH,\
    _March_ 1921.\
\
\
\
\
CONTENTS\
\
\
                                                                   PAGE\
    CHAPTER I\
    REPAIR                                                            1\
\
    CHAPTER II\
    CONDITIONS WHICH INTERFERE WITH REPAIR                           17\
\
    CHAPTER III\
    INFLAMMATION                                                     31\
\
    CHAPTER IV\
    SUPPURATION                                                      45\
\
    CHAPTER V\
    ULCERATION AND ULCERS                                            68\
\
    CHAPTER VI\
    GANGRENE                                                         86\
\
    CHAPTER VII\
    BACTERIAL AND OTHER WOUND INFECTIONS                            107\
\
    CHAPTER VIII\
    TUBERCULOSIS                                                    133\
\
    CHAPTER IX\
    SYPHILIS                                                        146\
\
    CHAPTER X\
    TUMOURS                                                         181\
\
    CHAPTER XI\
    INJURIES                                                        218\
\
    CHAPTER XII\
    METHODS OF WOUND TREATMENT                                      241\
\
    CHAPTER XIII\
    CONSTITUTIONAL EFFECTS OF INJURIES                              249\
\
    CHAPTER XIV\
    THE BLOOD VESSELS                                               258\
\
    CHAPTER XV\
    THE LYMPH VESSELS AND GLANDS                                    321\
\
    CHAPTER XVI\
    THE NERVES                                                      342\
\
    CHAPTER XVII\
    SKIN AND SUBCUTANEOUS TISSUES                                   376\
\
    CHAPTER XVIII\
    THE MUSCLES, TENDONS, AND TENDON SHEATHS                        405\
\
    CHAPTER XIX\
    THE BURSAE                                                       426\
\
    CHAPTER XX\
    DISEASES OF BONE                                                434\
\
    CHAPTER XXI\
    DISEASES OF JOINTS                                              501\
\
    INDEX                                                           547\
\
\
\
\
LIST OF ILLUSTRATIONS\
\
\
  FIG.                                                             PAGE\
\
    1. Ulcer of Back of Hand grafted from Abdominal Wall             15\
\
    2. Staphylococcus aureus in Pus from case of Osteomyelitis       25\
\
    3. Streptococci in Pus from case of Diffuse Cellulitis           26\
\
    4. Bacillus coli communis in Pus from Abdominal Abscess          27\
\
    5. Fraenkel's Pneumococci in Pus from Empyema following          28\
       Pneumonia\
\
    6. Passive Hyperaemia of Hand and Forearm induced by Bier's       37\
       Bandage\
\
    7. Passive Hyperaemia of Finger induced by Klapp's Suction        38\
       Bell\
\
    8. Passive Hyperaemia induced by Klapp's Suction Bell for         39\
       Inflammation of Inguinal Gland\
\
    9. Diagram of various forms of Whitlow                           56\
\
   10. Charts of Acute Sapraemia                                      61\
\
   11. Chart of Hectic Fever                                         62\
\
   12. Chart of Septicaemia followed by Pyaemia                        63\
\
   13. Chart of Pyaemia following on Acute Osteomyelitis              65\
\
   14. Leg Ulcers associated with Varicose Veins                     71\
\
   15. Perforating Ulcers of Sole of Foot                            74\
\
   16. Bazin's Disease in a girl aet. 16                              75\
\
   17. Syphilitic Ulcers in region of Knee                           76\
\
   18. Callous Ulcer showing thickened edges                         78\
\
   19. Tibia and Fibula, showing changes due to Chronic Ulcer of     80\
       Leg\
\
   20. Senile Gangrene of the Foot                                   89\
\
   21. Embolic Gangrene of Hand and Arm                              92\
\
   22. Gangrene of Terminal Phalanx of Index-Finger                 100\
\
   23. Cancrum Oris                                                 103\
\
   24. Acute Bed Sores over right Buttock                           104\
\
   25. Chart of Erysipelas occurring in a wound                     108\
\
   26. Bacillus of Tetanus                                          113\
\
   27. Bacillus of Anthrax                                          120\
\
   28. Malignant Pustule third day after infection                  122\
\
   29. Malignant Pustule fourteen days after infection              122\
\
   30. Colony of Actinomyces                                        126\
\
   31. Actinomycosis of Maxilla                                     128\
\
   32. Mycetoma, or Madura Foot                                     130\
\
   33. Tubercle bacilli                                             134\
\
   34. Tuberculous Abscess in Lumbar Region                         141\
\
   35. Tuberculous Sinus injected through its opening in the        144\
       Forearm with Bismuth Paste\
\
   36. Spirochaete pallida                                           147\
\
   37. Spirochaeta refrigerans from scraping of Vagina               148\
\
   38. Primary Lesion on Thumb, with Secondary Eruption on          154\
       Forearm\
\
   39. Syphilitic Rupia                                             159\
\
   40. Ulcerating Gumma of Lips                                     169\
\
   41. Ulceration in inherited Syphilis                             170\
\
   42. Tertiary Syphilitic Ulceration in region of Knee and on      171\
       both Thumbs\
\
   43. Facies of Inherited Syphilis                                 174\
\
   44. Facies of Inherited Syphilis                                 175\
\
   45. Subcutaneous Lipoma                                          185\
\
   46. Pedunculated Lipoma of Buttock                               186\
\
   47. Diffuse Lipomatosis of Neck                                  187\
\
   48. Zanthoma of Hands                                            188\
\
   49. Zanthoma of Buttock                                          189\
\
   50. Chondroma growing from Infra-Spinous Fossa of Scapula        190\
\
   51. Chondroma of Metacarpal Bone of Thumb                        190\
\
   52. Cancellous Osteoma of Lower End of Femur                     192\
\
   53. Myeloma of Shaft of Humerus                                  195\
\
   54. Fibro-myoma of Uterus                                        196\
\
   55. Recurrent Sarcoma of Sciatic Nerve                           198\
\
   56. Sarcoma of Arm fungating                                     199\
\
   57. Carcinoma of Breast                                          206\
\
   58. Epithelioma of Lip                                           209\
\
   59. Dermoid Cyst of Ovary                                        213\
\
   60. Carpal Ganglion in a woman aet. 25                            215\
\
   61. Ganglion on lateral aspect of Knee                           216\
\
   62. Radiogram showing pellets embedded in Arm                    228\
\
   63. Cicatricial Contraction following Severe Burn                236\
\
   64. Genealogical Tree of Haemophilic Family                       278\
\
   65. Radiogram showing calcareous degeneration of Arteries        284\
\
   66. Varicose Vein with Thrombosis                                289\
\
   67. Extensive Varix of Internal Saphena System on Left Leg       291\
\
   68. Mixed Naevus of Nose                                          296\
\
   69. Cirsoid Aneurysm of Forehead                                 299\
\
   70. Cirsoid Aneurysm of Orbit and Face                           300\
\
   71. Radiogram of Aneurysm of Aorta                               303\
\
   72. Sacculated Aneurysm of Abdominal Aorta                       304\
\
   73. Radiogram of Innominate Aneurysm after Treatment by          309\
       Moore-Corradi method\
\
   74. Thoracic Aneurysm threatening to rupture                     313\
\
   75. Innominate Aneurysm in a woman                               315\
\
   76. Congenital Cystic Tumour or Hygroma of Axilla                328\
\
   77. Tuberculous Cervical Gland with Abscess formation            331\
\
   78. Mass of Tuberculous Glands removed from Axilla               333\
\
   79. Tuberculous Axillary Glands                                  335\
\
   80. Chronic Hodgkin's Disease in boy aet. 11                      337\
\
   81. Lymphadenoma in a woman aet. 44                               338\
\
   82. Lympho Sarcoma removed from Groin                            339\
\
   83. Cancerous Glands in Neck, secondary to Epithelioma of Lip    341\
\
   84. Stump Neuromas of Sciatic Nerve                              345\
\
   85. Stump Neuromas, showing changes at ends of divided Nerves    354\
\
   86. Diffuse Enlargement of Nerves in generalised                 356\
       Neuro-Fibromatosis\
\
   87. Plexiform Neuroma of small Sciatic Nerve                     357\
\
   88. Multiple Neuro-Fibromas of Skin (Molluscum fibrosum)         358\
\
   89. Elephantiasis Neuromatosa in a woman aet. 28                  359\
\
   90. Drop-Wrist following Fracture of Shaft of Humerus            365\
\
   91. To illustrate the Loss of Sensation produced by Division     367\
       of the Median Nerve\
\
   92. To illustrate Loss of Sensation produced by Complete         368\
       Division of Ulnar Nerve\
\
   93. Callosities and Corns on Sole of Foot                        377\
\
   94. Ulcerated Chilblains on Fingers                              378\
\
   95. Carbuncle on Back of Neck                                    381\
\
   96. Tuberculous Elephantiasis                                    383\
\
   97. Elephantiasis in a woman aet. 45                              387\
\
   98. Elephantiasis of Penis and Scrotum                           388\
\
   99. Multiple Sebaceous Cysts or Wens                             390\
\
  100. Sebaceous Horn growing from Auricle                          392\
\
  101. Paraffin Epithelioma                                         394\
\
  102. Rodent Cancer of Inner Canthus                               395\
\
  103. Rodent Cancer with destruction of contents of Orbit          396\
\
  104. Diffuse Melanotic Cancer of Lymphatics of Skin               398\
\
  105. Melanotic Cancer of Forehead with Metastasis in Lymph        399\
       Glands\
\
  106. Recurrent Keloid                                             401\
\
  107. Subungual Exostosis                                          403\
\
  108. Avulsion of Tendon                                           410\
\
  109. Volkmann's Ischaemic Contracture                              414\
\
  110. Ossification in Tendon of Ilio-psoas Muscle                  417\
\
  111. Radiogram of Calcification and Ossification in Biceps and    418\
       Triceps\
\
  112. Ossification in Muscles of Trunk in generalised Ossifying    419\
       Myositis\
\
  113. Hydrops of Prepatellar Bursa                                 427\
\
  114. Section through Gouty Bursa                                  428\
\
  115. Tuberculous Disease of Sub-Deltoid Bursa                     429\
\
  116. Great Enlargement of the Ischial Bursa                       431\
\
  117. Gouty Disease of Bursae                                       432\
\
  118. Shaft of the Femur after Acute Osteomyelitis                 444\
\
  119. Femur and Tibia showing results of Acute Osteomyelitis       445\
\
  120. Segment of Tibia resected for Brodie's Abscess               449\
\
  121. Radiogram of Brodie's Abscess in Lower End of Tibia          451\
\
  122. Sequestrum of Femur after Amputation                         453\
\
  123. New Periosteal Bone on Surface of Femur from Amputation      454\
       Stump\
\
  124. Tuberculous Osteomyelitis of Os Magnum                       456\
\
  125. Tuberculous Disease of Tibia                                 457\
\
  126. Diffuse Tuberculous Osteomyelitis of Right Tibia             458\
\
  127. Advanced Tuberculous Disease in Region of Ankle              459\
\
  128. Tuberculous Dactylitis                                       460\
\
  129. Shortening of Middle Finger of Adult, the result of          461\
       Tuberculous Dactylitis in Childhood\
\
  130. Syphilitic Disease of Skull                                  463\
\
  131. Syphilitic Hyperostosis and Sclerosis of Tibia               464\
\
  132. Sabre-blade Deformity of Tibia                               467\
\
  133. Skeleton of Rickety Dwarf                                    470\
\
  134. Changes in the Skull resulting from Ostitis Deformans        474\
\
  135. Cadaver, illustrating the alterations in the Lower Limbs     475\
       resulting from Ostitis Deformans\
\
  136. Osteomyelitis Fibrosa affecting Femora                       476\
\
  137. Radiogram of Upper End of Femur in Osteomyelitis Fibrosa     478\
\
  138. Radiogram of Right Knee showing Multiple Exostoses           482\
\
  139. Multiple Exostoses of Limbs                                  483\
\
  140. Multiple Cartilaginous Exostoses                             484\
\
  141. Multiple Cartilaginous Exostoses                             486\
\
  142. Multiple Chondromas of Phalanges and Metacarpals             488\
\
  143. Skiagram of Multiple Chondromas                              489\
\
  144. Multiple Chondromas in Hand                                  490\
\
  145. Radiogram of Myeloma of Humerus                              492\
\
  146. Periosteal Sarcoma of Femur                                  493\
\
  147. Periosteal Sarcoma of Humerus                                493\
\
  148. Chondro-Sarcoma of Scapula                                   494\
\
  149. Central Sarcoma of Femur invading Knee Joint                 495\
\
  150. Osseous Shell of Osteo-Sarcoma of Femur                      495\
\
  151. Radiogram of Osteo-Sarcoma of Femur                          496\
\
  152. Radiogram of Chondro-Sarcoma of Humerus                      497\
\
  153. Epitheliomatus Ulcer of Leg invading Tibia                   499\
\
  154. Osseous Ankylosis of Femur and Tibia                         503\
\
  155. Osseous Ankylosis of Knee                                    504\
\
  156. Caseating focus in Upper End of Fibula                       513\
\
  157. Arthritis Deformans of Elbow                                 525\
\
  158. Arthritis Deformans of Knee                                  526\
\
  159. Hypertrophied Fringes of Synovial Membrane of Knee           527\
\
  160. Arthritis Deformans of Hands                                 529\
\
  161. Arthritis Deformans of several Joints                        530\
\
  162. Bones of Knee in Charcot's Disease                           533\
\
  163. Charcot's Disease of Left Knee                               534\
\
  164. Charcot's Disease of both Ankles: front view                 535\
\
  165. Charcot's Disease of both Ankles: back view                  536\
\
  166. Radiogram of Multiple Loose Bodies in Knee-joint             540\
\
  167. Loose Body from Knee-joint                                   541\
\
  168. Multiple partially ossified Chondromas of Synovial           542\
       Membrane from Shoulder-joint\
\
  169. Multiple Cartilaginous Loose Bodies from Knee-joint          543\
\
\
\
\
MANUAL OF SURGERY\
\
\
\
\
CHAPTER I\
\
REPAIR\
\
\
Introduction--Process of repair--Healing by primary union--Granulation\
    tissue--Cicatricial tissue--Modifications of process of\
    repair--Repair in individual tissues--Transplantation or grafting\
    of tissues--Conditions--Sources of grafts--Grafting of individual\
    tissues--Methods.\
\
\
INTRODUCTION\
\
To prolong human life and to alleviate suffering are the ultimate\
objects of scientific medicine. The two great branches of the healing\
art--Medicine and Surgery--are so intimately related that it is\
impossible to draw a hard-and-fast line between them, but for\
convenience Surgery may be defined as "the art of treating lesions and\
malformations of the human body by manual operations, mediate and\
immediate." To apply his art intelligently and successfully, it is\
essential that the surgeon should be conversant not only with the normal\
anatomy and physiology of the body and with the various pathological\
conditions to which it is liable, but also with the nature of the\
process by which repair of injured or diseased tissues is effected.\
Without this knowledge he is unable to recognise such deviations from\
the normal as result from mal-development, injury, or disease, or\
rationally to direct his efforts towards the correction or removal of\
these.\
\
\
PROCESS OF REPAIR\
\
The process of repair in living tissue depends upon an inherent power\
possessed by vital cells of reacting to the irritation caused by injury\
or disease. The cells of the damaged tissues, under the influence of\
this irritation, undergo certain proliferative changes, which are\
designed to restore the normal structure and configuration of the part.\
The process by which this restoration is effected is essentially the\
same in all tissues, but the extent to which different tissues can carry\
the recuperative process varies. Simple structures, such as skin,\
cartilage, bone, periosteum, and tendon, for example, have a high power\
of regeneration, and in them the reparative process may result in almost\
perfect restitution to the normal. More complex structures, on the other\
hand, such as secreting glands, muscle, and the tissues of the central\
nervous system, are but imperfectly restored, simple cicatricial\
connective tissue taking the place of what has been lost or destroyed.\
Any given tissue can be replaced only by tissue of a similar kind, and\
in a damaged part each element takes its share in the reparative process\
by producing new material which approximates more or less closely to the\
normal according to the recuperative capacity of the particular tissue.\
The normal process of repair may be interfered with by various\
extraneous agencies, the most important of which are infection by\
disease-producing micro-organisms, the presence of foreign substances,\
undue movement of the affected part, and improper applications and\
dressings. The effect of these agencies is to delay repair or to prevent\
the individual tissues carrying the process to the furthest degree of\
which they are capable.\
\
In the management of wounds and other diseased conditions the main\
object of the surgeon is to promote the natural reparative process by\
preventing or eliminating any factor by which it may be disturbed.\
\
#Healing by Primary Union.#--The most favourable conditions for the\
progress of the reparative process are to be found in a clean-cut wound\
of the integument, which is uncomplicated by loss of tissue, by the\
presence of foreign substances, or by infection with disease-producing\
micro-organisms, and its edges are in contact. Such a wound in virtue of\
the absence of infection is said to be _aseptic_, and under these\
conditions healing takes place by what is called "primary union"--the\
"healing by first intention" of the older writers.\
\
#Granulation Tissue.#--The essential and invariable medium of repair in\
all structures is an elementary form of new tissue known as _granulation\
tissue_, which is produced in the damaged area in response to the\
irritation caused by injury or disease. The vital reaction induced by\
such irritation results in dilatation of the vessels of the part,\
emigration of leucocytes, transudation of lymph, and certain\
proliferative changes in the fixed tissue cells. These changes are\
common to the processes of inflammation and repair; no hard-and-fast\
line can be drawn between these processes, and the two may go on\
together. It is, however, only when the proliferative changes have come\
to predominate that the reparative process is effectively established by\
the production of healthy granulation tissue.\
\
_Formation of Granulation Tissue._--When a wound is made in the\
integument under aseptic conditions, the passage of the knife through\
the tissues is immediately followed by an oozing of blood, which soon\
coagulates on the cut surfaces. In each of the divided vessels a clot\
forms, and extends as far as the nearest collateral branch; and on the\
surface of the wound there is a microscopic layer of bruised and\
devitalised tissue. If the wound is closed, the narrow space between its\
edges is occupied by blood-clot, which consists of red and white\
corpuscles mixed with a quantity of fibrin, and this forms a temporary\
uniting medium between the divided surfaces. During the first twelve\
hours, the minute vessels in the vicinity of the wound dilate, and from\
them lymph exudes and leucocytes migrate into the tissues. In from\
twenty-four to thirty-six hours, the capillaries of the part adjacent to\
the wound begin to throw out minute buds and fine processes, which\
bridge the gap and form a firmer, but still temporary, connection\
between the two sides. Each bud begins in the wall of the capillary as a\
small accumulation of granular protoplasm, which gradually elongates\
into a filament containing a nucleus. This filament either joins with a\
neighbouring capillary or with a similar filament, and in time these\
become hollow and are filled with blood from the vessels that gave them\
origin. In this way a series of young _capillary loops_ is formed.\
\
The spaces between these loops are filled by cells of various kinds, the\
most important being the _fibroblasts_, which are destined to form\
cicatricial fibrous tissue. These fibroblasts are large irregular\
nucleated cells derived mainly from the proliferation of the fixed\
connective-tissue cells of the part, and to a less extent from the\
lymphocytes and other mononuclear cells which have migrated from the\
vessels. Among the fibroblasts, larger multi-nucleated cells--_giant\
cells_--are sometimes found, particularly when resistant substances,\
such as silk ligatures or fragments of bone, are embedded in the\
tissues, and their function seems to be to soften such substances\
preliminary to their being removed by the phagocytes. Numerous\
_polymorpho-nuclear leucocytes_, which have wandered from the vessels,\
are also present in the spaces. These act as phagocytes, their function\
being to remove the red corpuscles and fibrin of the original clot, and\
this performed, they either pass back into the circulation in virtue of\
their amoeboid movement, or are themselves eaten up by the growing\
fibroblasts. Beyond this phagocytic action, they do not appear to play\
any direct part in the reparative process. These young capillary loops,\
with their supporting cells and fluids, constitute granulation tissue,\
which is usually fully formed in from three to five days, after which it\
begins to be replaced by cicatricial or scar tissue.\
\
_Formation of Cicatricial Tissue._--The transformation of this temporary\
granulation tissue into scar tissue is effected by the fibroblasts,\
which become elongated and spindle-shaped, and produce in and around\
them a fine fibrillated material which gradually increases in quantity\
till it replaces the cell protoplasm. In this way white fibrous tissue\
is formed, the cells of which are arranged in parallel lines and\
eventually become grouped in bundles, constituting fully formed white\
fibrous tissue. In its growth it gradually obliterates the capillaries,\
until at the end of two, three, or four weeks both vessels and cells\
have almost entirely disappeared, and the original wound is occupied by\
cicatricial tissue. In course of time this tissue becomes consolidated,\
and the cicatrix undergoes a certain amount of contraction--_cicatricial\
contraction_.\
\
_Healing of Epidermis._--While these changes are taking place in the\
deeper parts of the wound, the surface is being covered over by\
_epidermis_ growing in from the margins. Within twelve hours the cells\
of the rete Malpighii close to the cut edge begin to sprout on to the\
surface of the wound, and by their proliferation gradually cover the\
granulations with a thin pink pellicle. As the epithelium increases in\
thickness it assumes a bluish hue and eventually the cells become\
cornified and the epithelium assumes a greyish-white colour.\
\
_Clinical Aspects._--So long as the process of repair is not complicated\
by infection with micro-organisms, there is no interference with the\
general health of the patient. The temperature remains normal; the\
circulatory, gastro-intestinal, nervous, and other functions are\
undisturbed; locally, the part is cool, of natural colour and free from\
pain.\
\
#Modifications of the Process of Repair.#--The process of repair by\
primary union, above described, is to be looked upon as the type of all\
reparative processes, such modifications as are met with depending\
merely upon incidental differences in the conditions present, such as\
loss of tissue, infection by micro-organisms, etc.\
\
_Repair after Loss or Destruction of Tissue._--When the edges of a wound\
cannot be approximated either because tissue has been lost, for example\
in excising a tumour or because a drainage tube or gauze packing has\
been necessary, a greater amount of granulation tissue is required to\
fill the gap, but the process is essentially the same as in the ideal\
method of repair.\
\
The raw surface is first covered by a layer of coagulated blood and\
fibrin. An extensive new formation of capillary loops and fibroblasts\
takes place towards the free surface, and goes on until the gap is\
filled by a fine velvet-like mass of granulation tissue. This\
granulation tissue is gradually replaced by young cicatricial tissue,\
and the surface is covered by the ingrowth of epithelium from the edges.\
\
This modification of the reparative process can be best studied\
clinically in a recent wound which has been packed with gauze. When the\
plug is introduced, the walls of the cavity consist of raw tissue with\
numerous oozing blood vessels. On removing the packing on the fifth or\
sixth day, the surface is found to be covered with minute, red,\
papillary granulations, which are beginning to fill up the cavity. At\
the edges the epithelium has proliferated and is covering over the newly\
formed granulation tissue. As lymph and leucocytes escape from the\
exposed surface there is a certain amount of serous or sero-purulent\
discharge. On examining the wound at intervals of a few days, it is\
found that the granulation tissue gradually increases in amount till the\
gap is completely filled up, and that coincidently the epithelium\
spreads in and covers over its surface. In course of time the epithelium\
thickens, and as the granulation tissue is slowly replaced by young\
cicatricial tissue, which has a peculiar tendency to contract and so to\
obliterate the blood vessels in it, the scar that is left becomes\
smooth, pale, and depressed. This method of healing is sometimes spoken\
of as "healing by granulation"--although, as we have seen, it is by\
granulation that all repair takes place.\
\
_Healing by Union of two Granulating Surfaces._--In gaping wounds union\
is sometimes obtained by bringing the two surfaces into apposition after\
each has become covered with healthy granulations. The exudate on the\
surfaces causes them to adhere, capillary loops pass from one to the\
other, and their final fusion takes place by the further development of\
granulation and cicatricial tissue.\
\
_Reunion of Parts entirely Separated from the Body._--Small portions of\
tissue, such as the end of a finger, the tip of the nose or a portion of\
the external ear, accidentally separated from the body, if accurately\
replaced and fixed in position, occasionally adhere by primary union.\
\
In the course of operations also, portions of skin, fascia, or bone, or\
even a complete joint may be transplanted, and unite by primary union.\
\
_Healing under a Scab._--When a small superficial wound is exposed to\
the air, the blood and serum exuded on its surface may dry and form a\
hard crust or _scab_, which serves to protect the surface from external\
irritation in the same way as would a dry pad of sterilised gauze. Under\
this scab the formation of granulation tissue, its transformation into\
cicatricial tissue, and the growth of epithelium on the surface, go on\
until in the course of time the crust separates, leaving a scar.\
\
_Healing by Blood-clot._--In subcutaneous wounds, for example tenotomy,\
in amputation wounds, and in wounds made in excising tumours or in\
operating upon bones, the space left between the divided tissues becomes\
filled with blood-clot, which acts as a temporary scaffolding in which\
granulation tissue is built up. Capillary loops grow into the coagulum,\
and migrated leucocytes from the adjacent blood vessels destroy the red\
corpuscles, and are in turn disposed of by the developing fibroblasts,\
which by their growth and proliferation fill up the gap with young\
connective tissue. It will be evident that this process only differs\
from healing by primary union in the _amount_ of blood-clot that is\
present.\
\
_Presence of a Foreign Body._--When an aseptic foreign body is present\
in the tissues, _e.g._ a piece of unabsorbable chromicised catgut, the\
healing process may be modified. After primary union has taken place the\
scar may broaden, become raised above the surface, and assume a\
bluish-brown colour; the epidermis gradually thins and gives way,\
revealing the softened portion of catgut, which can be pulled out in\
pieces, after which the wound rapidly heals and resumes a normal\
appearance.\
\
\
REPAIR IN INDIVIDUAL TISSUES\
\
_Skin and Connective Tissue._--The mode of regeneration of these tissues\
under aseptic conditions has already been described as the type of ideal\
repair. In highly vascular parts, such as the face, the reparative\
process goes on with great rapidity, and even extensive wounds may be\
firmly united in from three to five days. Where the anastomosis is less\
free the process is more prolonged. The more highly organised elements\
of the skin, such as the hair follicles, the sweat and sebaceous glands,\
are imperfectly reproduced; hence the scar remains smooth, dry, and\
hairless.\
\
_Epithelium._--Epithelium is only reproduced from pre-existing\
epithelium, and, as a rule, from one of a similar type, although\
metaplastic transformation of cells of one kind of epithelium into\
another kind can take place. Thus a granulating surface may be covered\
entirely by the ingrowing of the cutaneous epithelium from the margins;\
or islets, originating in surviving cells of sebaceous glands or sweat\
glands, or of hair follicles, may spring up in the centre of the raw\
area. Such islets may also be due to the accidental transference of\
loose epithelial cells from the edges. Even the fluid from a blister, in\
virtue of the isolated cells of the rete Malpighii which it contains, is\
capable of starting epithelial growth on a granulating surface. Hairs\
and nails may be completely regenerated if a sufficient amount of the\
hair follicles or of the nail matrix has escaped destruction. The\
epithelium of a mucous membrane is regenerated in the same way as that\
on a cutaneous surface.\
\
Epithelial cells have the power of living for some time after being\
separated from their normal surroundings, and of growing again when once\
more placed in favourable circumstances. On this fact the practice of\
skin grafting is based (p. 11).\
\
_Cartilage._--When an articular cartilage is divided by incision or by\
being implicated in a fracture involving the articular end of a bone, it\
is repaired by ordinary cicatricial fibrous tissue derived from the\
proliferating cells of the perichondrium. Cartilage being a non-vascular\
tissue, the reparative process goes on slowly, and it may be many weeks\
before it is complete.\
\
It is possible for a metaplastic transformation of connective-tissue\
cells into cartilage cells to take place, the characteristic hyaline\
matrix being secreted by the new cells. This is sometimes observed as an\
intermediary stage in the healing of fractures, especially in young\
bones. It may also take place in the regeneration of lost portions of\
cartilage, provided the new tissue is so situated as to constitute part\
of a joint and to be subjected to pressure by an opposing cartilaginous\
surface. This is illustrated by what takes place after excision of\
joints where it is desired to restore the function of the articulation.\
By carrying out movements between the constituent parts, the fibrous\
tissue covering the ends of the bones becomes moulded into shape, its\
cells take on the characters of cartilage cells, and, forming a matrix,\
so develop a new cartilage.\
\
Conversely, it is observed that when articular cartilage is no longer\
subjected to pressure by an opposing cartilage, it tends to be\
transformed into fibrous tissue, as may be seen in deformities attended\
with displacement of articular surfaces, such as hallux valgus and\
club-foot.\
\
After fractures of costal cartilage or of the cartilages of the larynx\
the cicatricial tissue may be ultimately replaced by bone.\
\
_Tendons._--When a tendon is divided, for example by subcutaneous\
tenotomy, the end nearer the muscle fibres is drawn away from the other,\
leaving a gap which is speedily filled by blood-clot. In the course of a\
few days this clot becomes permeated by granulation tissue, the\
fibroblasts of which are derived from the sheath of the tendon, the\
surrounding connective tissue, and probably also from the divided ends\
of the tendon itself. These fibroblasts ultimately develop into typical\
tendon cells, and the fibres which they form constitute the new tendon\
fibres. Under aseptic conditions repair is complete in from two to three\
weeks. In the course of the reparative process the tendon and its sheath\
may become adherent, which leads to impaired movement and stiffness. If\
the ends of an accidentally divided tendon are at once brought into\
accurate apposition and secured by sutures, they unite directly with a\
minimum amount of scar tissue, and function is perfectly restored.\
\
_Muscle._--Unstriped muscle does not seem to be capable of being\
regenerated to any but a moderate degree. If the ends of a divided\
striped muscle are at once brought into apposition by stitches, primary\
union takes place with a minimum of intervening fibrous tissue. The\
nuclei of the muscle fibres in close proximity to this young cicatricial\
tissue proliferate, and a few new muscle fibres may be developed, but\
any gross loss of muscular tissue is replaced by a fibrous cicatrix. It\
would appear that portions of muscle transplanted from animals to fill\
up gaps in human muscle are similarly replaced by fibrous tissue. When a\
muscle is paralysed from loss of its nerve supply and undergoes complete\
degeneration, it is not capable of being regenerated, even should the\
integrity of the nerve be restored, and so its function is permanently\
lost.\
\
_Secretory Glands._--The regeneration of secretory glands is usually\
incomplete, cicatricial tissue taking the place of the glandular\
substance which has been destroyed. In wounds of the liver, for example,\
the gap is filled by fibrous tissue, but towards the periphery of the\
\
wound the liver cells proliferate and a certain amount of regeneration\
takes place. In the kidney also, repair mainly takes place by\
cicatricial tissue, and although a few collecting tubules may be\
reformed, no regeneration of secreting tissue takes place. After the\
operation of decapsulation of the kidney a new capsule is formed, and\
during the process young blood vessels permeate the superficial parts\
of the kidney and temporarily increase its blood supply, but in the\
consolidation of the new fibrous tissue these vessels are ultimately\
obliterated. This does not prove that the operation is useless, as the\
temporary improvement of the circulation in the kidney may serve to tide\
the patient over a critical period of renal insufficiency.\
\
_Stomach and Intestine._--Provided the peritoneal surfaces are\
accurately apposed, wounds of the stomach and intestine heal with great\
rapidity. Within a few hours the peritoneal surfaces are glued together\
by a thin layer of fibrin and leucocytes, which is speedily organised\
and replaced by fibrous tissue. Fibrous tissue takes the place of the\
muscular elements, which are not regenerated. The mucous lining is\
restored by ingrowth from the margins, and there is evidence that some\
of the secreting glands may be reproduced.\
\
Hollow viscera, like the oesophagus and urinary bladder, in so far\
as they are not covered by peritoneum, heal less rapidly.\
\
_Nerve Tissues._--There is no trustworthy evidence that regeneration of\
the tissues of the brain or spinal cord in man ever takes place. Any\
loss of substance is replaced by cicatricial tissue.\
\
The repair of _Bone_, _Blood Vessels_, and _Peripheral Nerves_ is more\
conveniently considered in the chapters dealing with these structures.\
\
#Rate of Healing.#--While the rate at which wounds heal is remarkably\
constant there are certain factors that influence it in one direction or\
the other. Healing is more rapid when the edges are in contact, when\
there is a minimum amount of blood-clot between them, when the patient\
is in normal health and the vitality of the tissues has not been\
impaired. Wounds heal slightly more quickly in the young than in the\
old, although the difference is so small that it can only be\
demonstrated by the most careful observations.\
\
Certain tissues take longer to heal than others: for example, a fracture\
of one of the larger long bones takes about six weeks to unite, and\
divided nerve trunks take much longer--about a year.\
\
Wounds of certain parts of the body heal more quickly than others: those\
of the scalp, face, and neck, for example, heal more quickly than those\
over the buttock or sacrum, probably because of their greater\
vascularity.\
\
The extent of the wound influences the rate of healing; it is only\
\
natural that a long and deep wound should take longer to heal than a\
short and superficial one, because there is so much more work to be\
done in the conversion of blood-clot into granulation tissue, and this\
again into scar tissue that will be strong enough to stand the strain on\
the edges of the wound.\
\
\
THE TRANSPLANTATION OR GRAFTING OF TISSUES\
\
Conditions are not infrequently met with in which healing is promoted\
and restoration of function made possible by the transference of a\
portion of tissue from one part of the body to another; the tissue\
transferred is known as the _graft_ or the _transplant_. The simplest\
example of grafting is the transplantation of skin.\
\
In order that the graft may survive and have a favourable chance of\
"taking," as it is called, the transplanted tissue must retain its\
vitality until it has formed an organic connection with the tissue in\
which it is placed, so that it may derive the necessary nourishment from\
its new bed. When these conditions are fulfilled the tissues of the\
graft continue to proliferate, producing new tissue elements to replace\
those that are lost and making it possible for the graft to become\
incorporated with the tissue with which it is in contact.\
\
Dead tissue, on the other hand, can do neither of these things; it is\
only capable of acting as a model, or, at the most, as a scaffolding for\
such mobile tissue elements as may be derived from, the parent tissue\
with which the graft is in contact: a portion of sterilised marine\
sponge, for example, may be observed to become permeated with\
granulation tissue when it is embedded in the tissues.\
\
A successful graft of living tissue is not only capable of regeneration,\
but it acquires a system of lymph and blood vessels, so that in time it\
bleeds when cut into, and is permeated by new nerve fibres spreading in\
from the periphery towards the centre.\
\
It is instructive to associate the period of survival of the different\
tissues of the body after death, with their capacity of being used for\
grafting purposes; the higher tissues such as those of the central\
nervous system and highly specialised glandular tissues like those of\
the kidney lose their vitality quickly after death and are therefore\
useless for grafting; connective tissues, on the other hand, such as\
fat, cartilage, and bone retain their vitality for several hours after\
death, so that when they are transplanted, they readily "take" and do\
all that is required of them: the same is true of the skin and its\
appendages.\
\
_Sources of Grafts._--It is convenient to differentiate between\
_autoplastic_ grafts, that is those derived from the same individual;\
_homoplastic_ grafts, derived from another animal of the same species;\
and _heteroplastic_ grafts, derived from an animal of another species.\
Other conditions being equal, the prospects of success are greatest with\
autoplastic grafts, and these are therefore preferred whenever possible.\
\
There are certain details making for success that merit attention: the\
graft must not be roughly handled or allowed to dry, or be subjected to\
chemical irritation; it must be brought into accurate contact with the\
new soil, no blood-clot intervening between the two, no movement of the\
one upon the other should be possible and all infection must be\
excluded; it will be observed that these are exactly the same conditions\
that permit of the primary healing of wounds, with which of course the\
healing of grafts is exactly comparable.\
\
_Preservation of Tissues for Grafting._--It was at one time believed\
that tissues might be taken from the operating theatre and kept in cold\
storage until they were required. It is now agreed that tissues which\
have been separated from the body for some time inevitably lose their\
vitality, become incapable of regeneration, and are therefore unsuited\
for grafting purposes. If it is intended to preserve a portion of tissue\
for future grafting, it should be embedded in the subcutaneous tissue of\
the abdominal wall until it is wanted; this has been carried out with\
portions of costal cartilage and of bone.\
\
\
INDIVIDUAL TISSUES AS GRAFTS\
\
#The Blood# lends itself in an ideal manner to transplantation, or, as\
it has long been called, _transfusion_. Being always a homoplastic\
transfer, the new blood is not always tolerated by the old, in which\
case biochemical changes occur, resulting in haemolysis, which\
corresponds to the disintegration of other unsuccessful homoplastic\
grafts. (See article on Transfusion, _Op. Surg._, p. 37.)\
\
#The Skin.#--The skin was the first tissue to be used for grafting\
purposes, and it is still employed with greater frequency than any\
other, as lesions causing defects of skin are extremely common and\
without the aid of grafts are tedious in healing.\
\
Skin grafts may be applied to a raw surface or to one that is covered\
with granulations.\
\
_Skin grafting of raw surfaces_ is commonly indicated after operations\
for malignant disease in which considerable areas of skin must be\
sacrificed, and after accidents, such as avulsion of the scalp by\
machinery.\
\
_Skin grafting of granulating surfaces_ is chiefly employed to promote\
healing in the large defects of skin caused by severe burns; the\
grafting is carried out when the surface is covered by a uniform layer\
of healthy granulations and before the inevitable contraction of scar\
tissue makes itself manifest. Before applying the grafts it is usual to\
scrape away the granulations until the young fibrous tissue underneath\
is exposed, but, if the granulations are healthy and can be rendered\
aseptic, the grafts may be placed on them directly.\
\
If it is decided to scrape away the granulations, the oozing must be\
arrested by pressure with a pad of gauze, a sheet of dental rubber or\
green protective is placed next the raw surface to prevent the gauze\
adhering and starting the bleeding afresh when it is removed.\
\
#Methods of Skin-Grafting.#--Two methods are employed: one in which the\
epidermis is mainly or exclusively employed--epidermis or epithelial\
grafting; the other, in which the graft consists of the whole thickness\
of the true skin--cutis-grafting.\
\
_Epidermis or Epithelial Grafting._--The method introduced by the late\
Professor Thiersch of Leipsic is that almost universally practised. It\
consists in transplanting strips of epidermis shaved from the surface of\
the skin, the razor passing through the tips of the papillae, which\
appear as tiny red points yielding a moderate ooze of blood.\
\
The strips are obtained from the front and lateral aspects of the thigh\
or upper arm, the skin in those regions being pliable and comparatively\
free from hairs.\
\
They are cut with a sharp hollow-ground razor or with Thiersch's\
grafting knife, the blade of which is rinsed in alcohol and kept\
moistened with warm saline solution. The cutting is made easier if the\
skin is well stretched and kept flat and perfectly steady, the\
operator's left hand exerting traction on the skin behind, the hands of\
the assistant on the skin in front, one above and the other below the\
seat of operation. To ensure uniform strips being cut, the razor is kept\
parallel with the surface and used with a short, rapid, sawing movement,\
so that, with a little practice, grafts six or eight inches long by one\
or two inches broad can readily be cut. The patient is given a general\
anaesthetic, or regional anaesthesia is obtained by injections of a\
solution of one per cent. novocain into the line of the lateral and\
middle cutaneous nerves; the disinfection of the skin is carried out on\
the usual lines, any chemical agent being finally got rid of, however,\
by means of alcohol followed by saline solution.\
\
The strips of epidermis wrinkle up on the knife and are directly\
transferred to the surface, for which they should be made to form a\
complete carpet, slightly overlapping the edges of the area and of one\
another; some blunt instrument is used to straighten out the strips,\
which are then subjected to firm pressure with a pad of gauze to express\
blood and air-bells and to ensure accurate contact, for this must be as\
close as that between a postage stamp and the paper to which it is\
affixed.\
\
As a dressing for the grafted area and of that also from which the\
grafts have been taken, gauze soaked in _liquid paraffin_--the patent\
variety known as _ambrine_ is excellent--appears to be the best; the\
gauze should be moistened every other day or so with fresh paraffin, so\
that, at the end of a week, when the grafts should have united, the\
gauze can be removed without risk of detaching them. _Dental wax_ is\
another useful type of dressing; as is also _picric acid_ solution. Over\
the gauze, there is applied a thick layer of cotton wool, and the whole\
dressing is kept in place by a firmly applied bandage, and in the case\
of the limbs some form of splint should be added to prevent movement.\
\
A dressing may be dispensed with altogether, the grafts being protected\
by a wire cage such as is used after vaccination, but they tend to dry\
up and come to resemble a scab.\
\
When the grafts have healed, it is well to protect them from injury and\
to prevent them drying up and cracking by the liberal application of\
lanoline or vaseline.\
\
The new skin is at first insensitive and is fixed to the underlying\
connective tissue or bone, but in course of time (from six weeks\
onwards) sensation returns and the formation of elastic tissue beneath\
renders the skin pliant and movable so that it can be pinched up between\
the finger and thumb.\
\
_Reverdin's_ method consists in planting out pieces of skin not bigger\
than a pin-head over a granulating surface. It is seldom employed.\
\
_Grafts of the Cutis Vera._--Grafts consisting of the entire thickness\
of the true skin were specially advocated by Wolff and are often\
associated with his name. They should be cut oval or spindle-shaped, to\
facilitate the approximation of the edges of the resulting wound. The\
graft should be cut to the exact size of the surface it is to cover;\
Gillies believes that tension of the graft favours its taking. These\
grafts may be placed either on a fresh raw surface or on healthy\
granulations. It is sometimes an advantage to stitch them in position,\
especially on the face. The dressing and the after-treatment are the\
same as in epidermis grafting.\
\
There is a degree of uncertainty about the graft retaining its vitality\
long enough to permit of its deriving the necessary nourishment from its\
new surroundings; in a certain number of cases the flap dies and is\
thrown off as a slough--moist or dry according to the presence or\
absence of septic infection.\
\
The technique for cutis-grafting must be without a flaw, and the asepsis\
absolute; there must not only be a complete absence of movement, but\
there must be no traction on the flap that will endanger its blood\
supply.\
\
Owing to the uncertainty in the results of cutis-grafting the\
_two-stage_ or _indirect method_ has been introduced, and its almost\
uniform success has led to its sphere of application being widely\
extended. The flap is raised as in the direct method but is left\
attached at one of its margins for a period ranging from 14 to 21 days\
until its blood supply from its new bed is assured; the detachment is\
then made complete. The blood supply of the proposed flap may influence\
its selection and the way in which it is fashioned; for example, a flap\
cut from the side of the head to fill a defect in the cheek, having in\
its margin of attachment or pedicle the superficial temporal artery, is\
more likely to take than a flap cut with its base above.\
\
Another modification is to raise the flap but leave it connected at both\
ends like the piers of a bridge; this method is well suited to defects\
of skin on the dorsum of the fingers, hand and forearm, the bridge of\
skin is raised from the abdominal wall and the hand is passed beneath it\
and securely fixed in position; after an interval of 14 to 21 days, when\
the flap is assured of its blood supply, the piers of the bridge are\
divided (Fig. 1). With undermining it is usually easy to bring the\
edges of the gap in the abdominal wall together, even in children; the\
skin flap on the dorsum of the hand appears rather thick and\
prominent--almost like the pad of a boxing-glove--for some time, but\
the restoration of function in the capacity to flex the fingers is\
gratifying in the extreme.\
\
[Illustration: FIG. 1.--Ulcer of back of Hand covered by flap of skin\
raised from anterior abdominal wall. The lateral edges of the flap are\
divided after the graft has adhered.]\
\
The indirect element of this method of skin-grafting may be carried\
still further by transferring the flap of skin first to one part of the\
body and then, after it has taken, transferring it to a third part.\
Gillies has especially developed this method in the remedying of\
deformities of the face caused by gunshot wounds and by petrol burns in\
air-men. A rectangular flap of skin is marked out in the neck and chest,\
the lateral margins of the flap are raised sufficiently to enable them\
to be brought together so as to form a tube of skin: after the\
circulation has been restored, the lower end of the tube is detached and\
is brought up to the lip or cheek, or eyelid, where it is wanted; when\
this end has derived its new blood supply, the other end is detached\
from the neck and brought up to where it is wanted. In this way, skin\
from the chest may be brought up to form a new forehead and eyelids.\
\
Grafts of _mucous membrane_ are used to cover defects in the lip, cheek,\
and conjunctiva. The technique is similar to that employed in\
skin-grafting; the sources of mucous membrane are limited and the\
element of septic infection cannot always be excluded.\
\
_Fat._--Adipose tissue has a low vitality, but it is easily retained and\
it readily lends itself to transplantation. Portions of fat are often\
obtainable at operations--from the omentum, for example, otherwise the\
subcutaneous fat of the buttock is the most accessible; it may be\
employed to fill up cavities of all kinds in order to obtain more rapid\
and sounder healing and also to remedy deformity, as in filling up a\
depression in the cheek or forehead. It is ultimately converted into\
ordinary connective tissue _pari passu_ with the absorption of the fat.\
\
The _fascia lata of the thigh_ is widely and successfully used as a\
graft to fill defects in the dura mater, and interposed between the\
bones of a joint--if the articular cartilage has been destroyed--to\
prevent the occurrence of ankylosis.\
\
The _peritoneum_ of hydrocele and hernial sacs and of the omentum\
readily lends itself to transplantation.\
\
_Cartilage and bone_, next to skin, are the tissues most frequently\
employed for grafting purposes; their sphere of action is so extensive\
and includes so much of technical detail in their employment, that they\
will be considered later with the surgery of the bones and joints and\
with the methods of re-forming the nose.\
\
_Tendons and blood vessels_ readily lend themselves to transplantation\
and will also be referred to later.\
\
_Muscle and nerve_, on the other hand, do not retain their vitality when\
severed from their surroundings and do not functionate as grafts except\
for their connective-tissue elements, which it goes without saying are\
more readily obtainable from other sources.\
\
Portions of the _ovary_ and of the _thyreoid_ have been successfully\
transplanted into the subcutaneous cellular tissue of the abdominal wall\
by Tuffier and others. In these new surroundings, the ovary or thyreoid\
is vascularised and has been shown to functionate, but there is not\
sufficient regeneration of the essential tissue elements to "carry on";\
the secreting tissue is gradually replaced by connective tissue and the\
special function comes to an end. Even such temporary function may,\
however, tide a patient over a difficult period.\
\
\
\
\
CHAPTER II\
\
CONDITIONS WHICH INTERFERE WITH REPAIR\
\
\
SURGICAL BACTERIOLOGY\
\
Want of rest--Irritation--Unhealthy tissues--Pathogenic bacteria.\
    SURGICAL BACTERIOLOGY--General characters of\
    bacteria--Classification of bacteria--Conditions of bacterial\
    life--Pathogenic powers of bacteria--Results of bacterial\
    growth--Death of bacteria--Immunity--Antitoxic sera--Identification\
    of bacteria--Pyogenic bacteria.\
\
In the management of wounds and other surgical conditions it is\
necessary to eliminate various extraneous influences which tend to delay\
or arrest the natural process of repair.\
\
Of these, one of the most important is undue movement of the affected\
part. "The first and great requisite for the restoration of injured\
parts is _rest_," said John Hunter; and physiological and mechanical\
rest as the chief of natural therapeutic agents was the theme of John\
Hilton's classical work--_Rest and Pain_. In this connection it must be\
understood that "rest" implies more than the mere state of physical\
repose: all physiological as well as mechanical function must be\
prevented as far as is possible. For instance, the constituent bones of\
a joint affected with tuberculosis must be controlled by splints or\
other appliances so that no movement can take place between them, and\
the limb may not be used for any purpose; physiological rest may be\
secured to an inflamed colon by making an artificial anus in the caecum;\
the activity of a diseased kidney may be diminished by regulating the\
quantity and quality of the fluids taken by the patient.\
\
Another source of interference with repair in wounds is _irritation_,\
either by mechanical agents such as rough, unsuitable dressings,\
bandages, or ill-fitting splints; or by chemical agents in the form of\
strong lotions or other applications.\
\
An _unhealthy or devitalised condition of the patient's tissues_ also\
hinders the reparative process. Bruised or lacerated skin heals less\
kindly than skin cut with a smooth, sharp instrument; and persistent\
\
venous congestion of a part, such as occurs, for example, in the leg\
when the veins are varicose, by preventing the access of healthy blood,\
tends to delay the healing of open wounds. The existence of grave\
constitutional disease, such as Bright's disease, diabetes, syphilis,\
scurvy, or alcoholism, also impedes healing.\
\
Infection by disease-producing micro-organisms or _pathogenic bacteria_\
is, however, the most potent factor in disturbing the natural process of\
repair in wounds.\
\
\
SURGICAL BACTERIOLOGY\
\
The influence of micro-organisms in the causation of disease, and the\
role played by them in interfering with the natural process of repair,\
are so important that the science of applied bacteriology has now come\
to dominate every department of surgery, and it is from the standpoint\
of bacteriology that nearly all surgical questions have to be\
considered.\
\
The term _sepsis_ as now used in clinical surgery no longer retains its\
original meaning as synonymous with "putrefaction," but is employed to\
denote all conditions in which bacterial infection has taken place, and\
more particularly those in which pyogenic bacteria are present. In the\
same way the term _aseptic_ conveys the idea of freedom from all forms\
of bacteria, putrefactive or otherwise; and the term _antiseptic_ is\
used to denote a power of counteracting bacteria and their products.\
\
#General Characters of Bacteria.#--A _bacterium_ consists of a finely\
granular mass of protoplasm, enclosed in a thin gelatinous envelope.\
Many forms are motile--some in virtue of fine thread-like flagella, and\
others through contractility of the protoplasm. The great majority\
multiply by simple fission, each parent cell giving rise to two daughter\
cells, and this process goes on with extraordinary rapidity. Other\
varieties, particularly bacilli, are propagated by the formation of\
_spores_. A spore is a minute mass of protoplasm surrounded by a dense,\
tough membrane, developed in the interior of the parent cell. Spores are\
remarkable for their tenacity of life, and for the resistance they offer\
to the action of heat and chemical germicides.\
\
Bacteria are most conveniently classified according to their shape. Thus\
we recognise (1) those that are globular--_cocci_; (2) those that\
resemble a rod--_bacilli_; (3) the spiral or wavy forms--_spirilla_.\
\
_Cocci_ or _micrococci_ are minute round bodies, averaging about 1 u in\
diameter. The great majority are non-motile. They multiply by fission;\
and when they divide in such a way that the resulting cells remain in\
pairs, are called _diplococci_, of which the bacteria of gonorrhoea and\
pneumonia are examples (Fig. 5). When they divide irregularly, and form\
grape-like bunches, they are known as _staphylococci_, and to this\
\
variety the commonest pyogenic or pus-forming organisms belong (Fig. 2).\
When division takes place only in one axis, so that long chains are\
formed, the term _streptococcus_ is applied (Fig. 3). Streptococci are\
met with in erysipelas and various other inflammatory and suppurative\
processes of a spreading character.\
\
_Bacilli_ are rod-shaped bacteria, usually at least twice as long as\
they are broad (Fig. 4). Some multiply by fission, others by\
sporulation. Some forms are motile, others are non-motile. Tuberculosis,\
tetanus, anthrax, and many other surgical diseases are due to different\
forms of bacilli.\
\
_Spirilla_ are long, slender, thread-like cells, more or less spiral or\
wavy. Some move by a screw-like contraction of the protoplasm, some by\
flagellae. The spirochaete associated with syphilis (Fig. 36) is the most\
important member of this group.\
\
#Conditions of Bacterial Life.#--Bacteria require for their growth and\
development a suitable food-supply in the form of proteins,\
carbohydrates, and salts of calcium and potassium which they break up\
into simpler elements. An alkaline medium favours bacterial growth; and\
moisture is a necessary condition; spores, however, can survive the want\
of water for much longer periods than fully developed bacteria. The\
necessity for oxygen varies in different species. Those that require\
oxygen are known as _aerobic bacilli_ or _aerobes_; those that cannot\
live in the presence of oxygen are spoken of as _anaerobes_. The great\
majority of bacteria, however, while they prefer to have oxygen, are\
able to live without it, and are called _facultative anaerobes_.\
\
The most suitable temperature for bacterial life is from 95 o to 102 o F.,\
roughly that of the human body. Extreme or prolonged cold paralyses but\
does not kill micro-organisms. Few, however, survive being raised to a\
temperature of 134 1/2 o F. Boiling for ten to twenty minutes will kill all\
bacteria, and the great majority of spores. Steam applied in an\
autoclave under a pressure of two atmospheres destroys even the most\
resistant spores in a few minutes. Direct sunlight, electric light, or\
even diffuse daylight, is inimical to the growth of bacteria, as are\
also Rontgen rays and radium emanations.\
\
#Pathogenic Properties of Bacteria.#--We are now only concerned with\
pathogenic bacteria--that is, bacteria capable of producing disease in\
the human subject. This capacity depends upon two sets of factors--(1)\
certain features peculiar to the invading bacteria, and (2) others\
peculiar to the host. Many bacteria have only the power of living upon\
dead matter, and are known as _saphrophytes_. Such as do nourish in\
living tissue are, by distinction, known as _parasites_. The power a\
given parasitic micro-organism has of multiplying in the body and giving\
rise to disease is spoken of as its _virulence_, and this varies not\
only with different species, but in the same species at different times\
and under varying circumstances. The actual number of organisms\
introduced is also an important factor in determining their pathogenic\
power. Healthy tissues can resist the invasion of a certain number of\
bacteria of a given species, but when that number is exceeded, the\
organisms get the upper hand and disease results. When the organisms\
gain access directly to the blood-stream, as a rule they produce their\
effects more certainly and with greater intensity than when they are\
introduced into the tissues.\
\
Further, the virulence of an organism is modified by the condition of\
the patient into whose tissues it is introduced. So long as a person is\
in good health, the tissues are able to resist the attacks of moderate\
numbers of most bacteria. Any lowering of the vitality of the\
individual, however, either locally or generally, at once renders him\
more susceptible to infection. Thus bruised or torn tissue is much more\
liable to infection with pus-producing organisms than tissues clean-cut\
with a knife; also, after certain diseases, the liability to infection\
by the organisms of diphtheria, pneumonia, or erysipelas is much\
increased. Even such slight depression of vitality as results from\
bodily fatigue, or exposure to cold and damp, may be sufficient to turn\
the scale in the battle between the tissues and the bacteria. Age is an\
important factor in regard to the action of certain bacteria. Young\
subjects are attacked by diphtheria, tuberculosis, acute osteomyelitis,\
and some other diseases with greater frequency and severity than those\
of more advanced years.\
\
In different races, localities, environment, and seasons, the pathogenic\
powers of certain organisms, such as those of erysipelas, diphtheria,\
and acute osteomyelitis, vary considerably.\
\
There is evidence that a _mixed infection_--that is, the introduction of\
more than one species of organism, for example, the tubercle bacillus\
and a pyogenic staphylococcus--increases the severity of the resulting\
disease. If one of the varieties gain the ascendancy, the poisons\
produced by the others so devitalise the tissue cells, and diminish\
their power of resistance, that the virulence of the most active\
organisms is increased. On the other hand, there is reason to believe\
that the products of certain organisms antagonise one another--for\
example, an attack of erysipelas may effect the cure of a patch of\
tuberculous lupus.\
\
Lastly, in patients suffering from chronic wasting diseases, bacteria\
may invade the internal organs by the blood-stream in enormous numbers\
and with great rapidity, during the period of extreme debility which\
shortly precedes death. The discovery of such collections of organisms\
on post-mortem examination may lead to erroneous conclusions being drawn\
as to the cause of death.\
\
#Results of Bacterial Growth.#--Some organisms, such as those of tetanus\
and erysipelas, and certain of the pyogenic bacteria, show little\
tendency to pass far beyond the point at which they gain an entrance to\
the body. Others, on the contrary--for example, the tubercle bacillus\
and the organism of acute osteomyelitis--although frequently remaining\
localised at the seat of inoculation, tend to pass to distant parts,\
lodging in the capillaries of joints, bones, kidney, or lungs, and there\
producing their deleterious effects.\
\
In the human subject, multiplication in the blood-stream does not occur\
to any great extent. In some general acute pyogenic infections, such as\
osteomyelitis, cellulitis, etc., pure cultures of staphylococci or of\
streptococci may be obtained from the blood. In pneumococcal and typhoid\
infections, also, the organisms may be found in the blood.\
\
It is by the vital changes they bring about in the parts where they\
settle that micro-organisms disturb the health of the patient. In\
deriving nourishment from the complex organic compounds in which they\
nourish, the organisms evolve, probably by means of a ferment, certain\
chemical products of unknown composition, but probably colloidal in\
nature, and known as _toxins_. When these poisons are absorbed into the\
general circulation they give rise to certain groups of symptoms--such\
as rise of temperature, associated circulatory and respiratory\
derangements, interference with the gastro-intestinal functions and also\
with those of the nervous system--which go to make up the condition\
known as blood-poisoning, toxaemia, or _bacterial intoxication_. In\
addition to this, certain bacteria produce toxins that give rise to\
definite and distinct groups of symptoms--such as the convulsions of\
tetanus, or the paralyses that follow diphtheria.\
\
_Death of Bacteria._--Under certain circumstances, it would appear that\
the accumulation of the toxic products of bacterial action tends to\
interfere with the continued life and growth of the organisms\
themselves, and in this way the natural cure of certain diseases is\
brought about. Outside the body, bacteria may be killed by starvation,\
by want of moisture, by being subjected to high temperature, or by the\
action of certain chemical agents of which carbolic acid, the\
perchloride and biniodide of mercury, and various chlorine preparations\
are the most powerful.\
\
#Immunity.#--Some persons are insusceptible to infection by certain\
diseases, from which they are said to enjoy a _natural immunity_. In\
many acute diseases one attack protects the patient, for a time at\
least, from a second attack--_acquired immunity_.\
\
_Phagocytosis._--In the production of immunity the leucocytes and\
certain other cells play an important part in virtue of the power they\
possess of ingesting bacteria and of destroying them by a process of\
intra-cellular digestion. To this process Metchnikoff gave the name of\
_phagocytosis_, and he recognised two forms of _phagocytes_: (1) the\
_microphages_, which are the polymorpho-nuclear leucocytes of the blood;\
and (2) the _macrophages_, which include the larger hyaline leucocytes,\
endothelial cells, and connective-tissue corpuscles.\
\
During the process of phagocytosis, the polymorpho-nuclear leucocytes in\
the circulating blood increase greatly in numbers (_leucocytosis_), as\
well as in their phagocytic action, and in the course of destroying the\
bacteria they produce certain ferments which enter the blood serum.\
These are known as _opsonins_ or _alexins_, and they act on the bacteria\
by a process comparable to narcotisation, and render them an easy prey\
for the phagocytes.\
\
_Artificial or Passive Immunity._--A form of immunity can be induced by\
the introduction of protective substances obtained from an animal which\
has been actively immunised. The process by which passive immunity is\
acquired depends upon the fact that as a result of the reaction between\
the specific virus of a particular disease (the _antigen_) and the\
tissues of the animal attacked, certain substances--_antibodies_--are\
produced, which when transferred to the body of a susceptible animal\
protect it against that disease. The most important of these antibodies\
are the _antitoxins_. From the study of the processes by which immunity\
is secured against the effects of bacterial action the serum and vaccine\
methods of treating certain infective diseases have been evolved. The\
_serum treatment_ is designed to furnish the patient with a sufficiency\
of antibodies to neutralise the infection. The anti-diphtheritic and the\
anti-tetanic act by neutralising the specific toxins of the\
disease--_antitoxic serums_; the anti-streptcoccic and the serum for\
anthrax act upon the bacteria--_anti-bacterial serums_.\
\
A _polyvalent_ serum, that is, one derived from an animal which has been\
immunised by numerous strains of the organism derived from various\
sources, is much more efficacious than when a single strain has been\
used.\
\
_Clinical Use of Serums._--Every precaution must be taken to prevent\
organismal contamination of the serum or of the apparatus by means of\
which it is injected. Syringes are so made that they can be sterilised\
by boiling. The best situations for injection are under the skin of the\
abdomen, the thorax, or the buttock, and the skin should be purified at\
the seat of puncture. If the bulk of the full dose is large, it should\
be divided and injected into different parts of the body, not more than\
20 c.c. being injected at one place. The serum may be introduced\
directly into a vein, or into the spinal canal, _e.g._ anti-tetanic\
serum. The immunity produced by injections of antitoxic sera lasts only\
for a comparatively short time, seldom longer than a few weeks.\
\
_"Serum Disease" and Anaphylaxis._--It is to be borne in mind that some\
patients exhibit a supersensitiveness with regard to protective sera, an\
injection being followed in a few days by the appearance of an\
urticarial or erythematous rash, pain and swelling of the joints, and a\
variable degree of fever. These symptoms, to which the name _serum\
disease_ is applied, usually disappear in the course of a few days.\
\
The term _anaphylaxis_ is applied to an allied condition of\
supersensitiveness which appears to be induced by the injection of\
certain substances, including toxins and sera, that are capable of\
acting as antigens. When a second injection is given after an interval\
of some days, if anaphylaxis has been established by the first dose, the\
patient suddenly manifests toxic symptoms of the nature of profound\
shock which may even prove fatal. The conditions which render a person\
liable to develop anaphylaxis and the mechanism by which it is\
established are as yet imperfectly understood.\
\
_Vaccine Treatment._--The vaccine treatment elaborated by A. E. Wright\
consists in injecting, while the disease is still active, specially\
prepared dead cultures of the causative organisms, and is based on the\
fact that these "vaccines" render the bacteria in the tissues less able\
to resist the attacks of the phagocytes. The method is most successful\
when the vaccine is prepared from organisms isolated from the patient\
himself, _autogenous vaccine_, but when this is impracticable, or takes\
a considerable time, laboratory-prepared polyvalent _stock vaccines_ may\
be used.\
\
_Clinical Use of Vaccines._--Vaccines should not be given while a\
patient is in a negative phase, as a certain amount of the opsonin in\
the blood is used up in neutralising the substances injected, and this\
may reduce the opsonic index to such an extent that the vaccines\
themselves become dangerous. As a rule, the propriety of using a vaccine\
can be determined from the general condition of the patient. The initial\
dose should always be a small one, particularly if the disease is acute,\
and the subsequent dosage will be regulated by the effect produced. If\
marked constitutional disturbance with rise of temperature follows the\
use of a vaccine, it indicates a negative phase, and calls for a\
diminution in the next dose. If, on the other hand, the local as well as\
the general condition of the patient improves after the injection, it\
indicates a positive phase, and the original dose may be repeated or\
even increased. Vaccines are best introduced subcutaneously, a part\
being selected which is not liable to pressure, as there is sometimes\
considerable local reaction. Repeated doses may be necessary at\
intervals of a few days.\
\
The vaccine treatment has been successfully employed in various\
tuberculous lesions, in pyogenic infections such as acne, boils,\
sycosis, streptococcal, pneumococcal, and gonococcal conditions, in\
infections of the accessory air sinuses, and in other diseases caused by\
bacteria.\
\
\
PYOGENIC BACTERIA\
\
From the point of view of the surgeon the most important varieties of\
micro-organisms are those that cause inflammation and suppuration--the\
_pyogenic bacteria_. This group includes a great many species, and these\
are so widely distributed that they are to be met with under all\
conditions of everyday life.\
\
The nature of the inflammatory and suppurative processes will be\
considered in detail later; suffice it here to say that they are brought\
about by the action of one or other of the organisms that we have now to\
consider.\
\
It is found that the _staphylococci_, which cluster into groups, tend to\
produce localised lesions; while the chain-forms--_streptococci_--give\
rise to diffuse, spreading conditions. Many varieties of pyogenic\
bacteria have now been differentiated, the best known being the\
staphylococcus aureus, the streptococcus, and the bacillus coli\
communis.\
\
[Illustration: FIG. 2.--Staphylococcus aureus in Pus from case of\
Osteomyelitis. x 1000 diam. Gram's stain.]\
\
_Staphylococcus Aureus._--This is the commonest organism found in\
localised inflammatory and suppurative conditions. It varies greatly in\
its virulence, and is found in such widely different conditions as skin\
pustules, boils, carbuncles, and some acute inflammations of bone. As\
seen by the microscope it occurs in grape-like clusters, fission of the\
individual cells taking place irregularly (Fig. 2). When grown in\
artificial media, the colonies assume an orange-yellow colour--hence the\
name _aureus_. It is of high vitality and resists more prolonged\
exposure to high temperatures than most non-sporing bacteria. It is\
capable of lying latent in the tissues for long periods, for example, in\
the marrow of long bones, and of again becoming active and causing a\
fresh outbreak of suppuration. This organism is widely distributed: it\
is found on the skin, in the mouth, and in other situations in the body,\
and as it is present in the dust of the air and on all objects upon\
which dust has settled, it is a continual source of infection unless\
means are taken to exclude it from wounds.\
\
The _staphylococcus albus_ is much less common than the aureus, but has\
the same properties and characters, save that its growth on artificial\
media assumes a white colour. It is the common cause of stitch\
abscesses, the skin being its normal habitat.\
\
[Illustration: FIG. 3.--Streptococci in Pus from an acute abscess in\
subcutaneous tissue. x 1000 diam. Gram's stain.]\
\
_Streptococcus Pyogenes._--This organism also varies greatly in its\
virulence; in some instances--for example in erysipelas--it causes a\
sharp attack of acute spreading inflammation, which soon subsides\
without showing any tendency to end in suppuration; under other\
conditions it gives rise to a generalised infection which rapidly proves\
fatal. The streptococcus has less capacity of liquefying the tissues\
than the staphylococcus, so that pus formation takes place more slowly.\
At the same time its products are very potent in destroying the tissues\
in their vicinity, and so interfering with the exudation of leucocytes\
which would otherwise exercise their protective influence. Streptococci\
invade the lymph spaces, and are associated with acute spreading\
conditions such as phlegmonous or erysipelatous inflammations and\
suppurations, lymphangitis and suppuration in lymph glands, and\
inflammation of serous and synovial membranes, also with a form of\
pneumonia which is prone to follow on severe operations in the mouth and\
throat. Streptococci are also concerned in the production of spreading\
gangrene and pyaemia.\
\
Division takes place in one axis, so that chains of varying length are\
formed (Fig. 3). It is less easily cultivated by artificial media than\
the staphylococcus; it forms a whitish growth.\
\
[Illustration: FIG. 4.--Bacillus coli communis in Urine, from a case of\
Cystitis. x 1000 diam. Leishman's stain.]\
\
_Bacillus Coli Communis._--This organism, which is a normal inhabitant\
of the intestinal tract, shows a great tendency to invade any organ or\
tissue whose vitality is lowered. It is causatively associated with such\
conditions as peritonitis and peritoneal suppuration resulting from\
strangulated hernia, appendicitis, or perforation in any part of the\
alimentary canal. In cystitis, pyelitis, abscess of the kidney,\
suppuration in the bile-ducts or liver, and in many other abdominal\
conditions, it plays a most important part. The discharge from wounds\
infected by this organism has usually a foetid, or even a faecal odour,\
and often contains gases resulting from putrefaction.\
\
It is a small rod-shaped organism with short flagellae, which render it\
motile (Fig. 4). It closely resembles the typhoid bacillus, but is\
distinguished from it by its behaviour in artificial culture media.\
\
[Illustration: FIG. 5.--Fraenkel's Pneumococci in Pus from Empyema\
following Pneumonia. x 100 diam. Stained with Muir's capsule stain.]\
\
_Pneumo-bacteria._--Two forms of organism associated with\
pneumonia--_Fraenkel's pneumococcus_ (one of the diplococci) (Fig. 5)\
and _Friedlander's pneumo-bacillus_ (a short rod-shaped form)--are\
frequently met with in inflammations of the serous and synovial\
membranes, in suppuration in the liver, and in various other\
inflammatory and suppurative conditions.\
\
_Bacillus Typhosus._--This organism has been found in pure culture in\
suppurative conditions of bone, of cellular tissue, and of internal\
organs, especially during convalescence from typhoid fever. Like the\
staphylococcus, it is capable of lying latent in the tissues for long\
periods.\
\
_Other Pyogenic Bacteria._--It is not necessary to do more than name\
some of the other organisms that are known to be pyogenic, such as the\
bacillus pyocyaneus, which is found in green and blue pus, the\
micrococcus tetragenus, the gonococcus, actinomyces, the glanders\
bacillus, and the tubercle bacillus. Most of these will receive further\
mention in connection with the diseases to which they give rise.\
\
#Leucocytosis.#--Most bacterial diseases, as well as certain other\
pathological conditions, are associated with an increase in the number\
of leucocytes in the blood throughout the circulatory system. This\
condition of the blood, which is known as _leucocytosis_, is believed to\
be due to an excessive output and rapid formation of leucocytes by the\
bone marrow, and it probably has as its object the arrest and\
destruction of the invading organisms or toxins. To increase the\
resisting power of the system to pathogenic organisms, an artificial\
leucocytosis may be induced by subcutaneous injection of a solution of\
nucleinate of soda (16 minims of a 5 per cent. solution).\
\
The _normal_ number of leucocytes per cubic millimetre varies in\
different individuals, and in the same individual under different\
conditions, from 5000 to 10,000: 7500 is a normal average, and anything\
above 12,000 is considered abnormal. When leucocytosis is present, the\
number may range from 12,000 to 30,000 or even higher; 40,000 is looked\
upon as a high degree of leucocytosis. According to Ehrlich, the\
following may be taken as the standard proportion of the various forms\
of leucocytes in normal blood: polynuclear neutrophile leucocytes, 70 to\
72 per cent.; lymphocytes, 22 to 25 per cent.; eosinophile cells, 2 to 4\
per cent.; large mononuclear and transitional leucocytes, 2 to 4 per\
cent.; mast-cells, 0.5 to 2 per cent.\
\
In estimating the clinical importance of a leucocytosis, it is not\
sufficient merely to count the aggregate number of leucocytes present. A\
differential count must be made to determine which variety of cells is\
in excess. In the majority of surgical affections it is chiefly the\
granular polymorpho-nuclear neutrophile leucocytes that are in excess\
(_ordinary leucocytosis_). In some cases, and particularly in parasitic\
diseases such as trichiniasis and hydatid disease, the eosinophile\
leucocytes also show a proportionate increase (_eosinophilia_). The term\
_lymphocytosis_ is applied when there is an increase in the number of\
circulating lymphocytes, as occurs, for example, in lymphatic leucaemia,\
and in certain cases of syphilis.\
\
Leucocytosis is met with in nearly all acute infective diseases, and in\
acute pyogenic inflammatory affections, particularly in those attended\
with suppuration. In exceptionally acute septic conditions the extreme\
virulence of the toxins may prevent the leucocytes reacting, and\
leucocytosis may be absent. The absence of leucocytosis in a disease in\
which it is usually present is therefore to be looked upon as a grave\
omen, particularly when the general symptoms are severe. In some cases\
of malignant disease the number of leucocytes is increased to 15,000 or\
20,000. A few hours after a severe haemorrhage also there is usually a\
leucocytosis of from 15,000 to 30,000, which lasts for three or four\
days (Lyon). In cases of haemorrhage the leucocytosis is increased by\
infusion of fluids into the circulation. After all operations there is\
at least a transient leucocytosis (_post-operative leucocytosis_)\
(F. I. Dawson).\
\
The leucocytosis begins soon after the infection manifests itself--for\
example, by shivering, rigor, or rise of temperature. The number of\
leucocytes rises somewhat rapidly, increases while the condition is\
progressing, and remains high during the febrile period, but there is no\
constant correspondence between the number of leucocytes and the height\
of the temperature. The arrest of the inflammation and its resolution\
are accompanied by a fall in the number of leucocytes, while the\
occurrence of suppuration is attended with a further increase in their\
number.\
\
In interpreting the "blood count," it is to be kept in mind that a\
_physiological leucocytosis_ occurs within three or four hours of taking\
a meal, especially one rich in proteins, from 1500 to 2000 being added\
to the normal number. In this _digestion leucocytosis_ the increase is\
chiefly in the polynuclear neutrophile leucocytes. Immediately before\
and after delivery, particularly in primiparae, there is usually a\
moderate degree of leucocytosis. If the labour is normal and the\
puerperium uncomplicated, the number of leucocytes regains the normal in\
about a week. Lactation has no appreciable effect on the number of\
leucocytes. In new-born infants the leucocyte count is abnormally high,\
ranging from 15,000 to 20,000. In children under one year of age, the\
normal average is from 10,000 to 20,000.\
\
_Absence of Leucocytosis--Leucopenia._--In certain infective diseases\
the number of leucocytes in the circulating blood is abnormally\
low--3000 or 4000--and this condition is known as _leucopenia_. It\
occurs in typhoid fever, especially in the later stages of the disease,\
in tuberculous lesions unaccompanied by suppuration, in malaria, and in\
most cases of uncomplicated influenza. The occurrence of leucocytosis in\
any of these conditions is to be looked upon as an indication that a\
mixed infection has taken place, and that some suppurative process is\
present.\
\
The absence of leucocytosis in some cases of virulent septic poisoning\
has already been referred to.\
\
It will be evident that too much reliance must not be placed upon a\
single observation, particularly in emergency cases. Whenever possible,\
a series of observations should be made, the blood being examined about\
four hours after meals, and about the same hour each day.\
\
The clinical significance of the blood count in individual diseases will\
be further referred to.\
\
_The Iodine or Glycogen Reaction._--The leucocyte count may be\
supplemented by staining films of the blood with a watery solution of\
iodine and potassium iodide. In all advancing purulent conditions, in\
septic poisonings, in pneumonia, and in cancerous growths associated\
with ulceration, a certain number of the polynuclear leucocytes are\
stained a brown or reddish-brown colour, due to the action of the iodine\
on some substance in the cells of the nature of glycogen. This reaction\
is absent in serous effusions, in unmixed tuberculous infections, in\
uncomplicated typhoid fever, and in the early stages of cancerous\
growths.\
\
\
\
\
CHAPTER III\
\
INFLAMMATION\
\
\
Definition--Nature of inflammation from surgical point of\
    view--Sequence of changes in bacterial inflammation--Clinical\
    aspects of inflammation--General principles of treatment--Chronic\
    inflammation.\
\
Inflammation may be defined as the series of vital changes that occurs\
in the tissues in response to irritation. These changes represent the\
reaction of the tissue elements to the irritant, and constitute the\
attempt made by nature to arrest or to limit its injurious effects, and\
to repair the damage done by it.\
\
The phenomena which characterise the inflammatory reaction can be\
induced by any form of irritation--such, for example, as mechanical\
injury, the application of heat or of chemical substances, or the action\
of pathogenic bacteria and their toxins--and they are essentially\
similar in kind whatever the irritant may be. The extent to which the\
process may go, however, and its effects on the part implicated and on\
the system as a whole, vary with different irritants and with the\
intensity and duration of their action. A mechanical, a thermal, or a\
chemical irritant, acting alone, induces a degree of reaction directly\
proportionate to its physical properties, and so long as it does not\
completely destroy the vitality of the part involved, the changes in the\
tissues are chiefly directed towards repairing the damage done to the\
part, and the inflammatory reaction is not only compatible with the\
occurrence of ideal repair, but may be looked upon as an integral step\
in the reparative process.\
\
The irritation caused by infection with bacteria, on the other hand, is\
cumulative, as the organisms not only multiply in the tissues, but in\
addition produce chemical poisons (toxins) which aggravate the\
irritative effects. The resulting reaction is correspondingly\
progressive, and has as its primary object the expulsion of the irritant\
and the limitation of its action. If the natural protective effort is\
successful, the resulting tissue changes subserve the process of repair,\
but if the bacteria gain the upper hand in the struggle, the\
inflammatory reaction becomes more intense, certain of the tissue\
elements succumb, and the process for the time being is a destructive\
one. During the stage of bacterial inflammation, reparative processes\
are in abeyance, and it is only after the inflammation has been allayed,\
either by natural means or by the aid of the surgeon, that repair takes\
place.\
\
In applying the antiseptic principle to the treatment of wounds, our\
main object is to exclude or to eliminate the bacterial factor, and so\
to prevent the inflammatory reaction going beyond the stage in which it\
is protective, and just in proportion as we succeed in attaining this\
object, do we favour the occurrence of ideal repair.\
\
#Sequence of Changes in Bacterial Inflammation.#--As the form of\
inflammation with which we are most concerned is that due to the action\
of bacteria, in describing the process by which the protective influence\
of the inflammatory reaction is brought into play, we shall assume the\
presence of a bacterial irritant.\
\
The introduction of a colony of micro-organisms is quickly followed by\
an accumulation of wandering cells, and proliferation of\
connective-tissue cells in the tissues at the site of infection. The\
various cells are attracted to the bacteria by a peculiar chemical or\
biological power known as _chemotaxis_, which seems to result from\
variations in the surface tension of different varieties of cells,\
probably caused by some substance produced by the micro-organisms.\
Changes in the blood vessels then ensue, the arteries becoming dilated\
and the rate of the current in them being for a time increased--_active\
hyperaemia_. Soon, however, the rate of the blood flow becomes slower\
than normal, and in course of time the current may cease (_stasis_), and\
the blood in the vessels may even coagulate (_thrombosis_). Coincidently\
with these changes in the vessels, the leucocytes in the blood of the\
inflamed part rapidly increase in number, and they become viscous and\
adhere to the vessel wall, where they may accumulate in large numbers.\
In course of time the leucocytes pass through the vessel\
wall--_emigration of leucocytes_--and move towards the seat of\
infection, giving rise to a marked degree of _local leucocytosis_.\
Through the openings by which the leucocytes have escaped from the\
vessels, red corpuscles may be passively extruded--_diapedesis of red\
corpuscles_. These processes are accompanied by changes in the\
endothelium of the vessel walls, which result in an increased formation\
of lymph, which transudes into the meshes of the connective tissue\
giving rise to an _inflammatory oedema_, or, if the inflammation is on a\
free surface, forming an _inflammatory exudate_. The quantity and\
characters of this exudate vary in different parts of the body, and\
according to the nature, virulence, and location of the organisms\
causing the inflammation. Thus it may be _serous_, as in some forms of\
synovitis; _sero-fibrinous_, as in certain varieties of peritonitis, the\
fibrin tending to limit the spread of the inflammation by forming\
adhesions; _croupous_, when it coagulates on a free surface and forms a\
false membrane, as in diphtheria; _haemorrhagic_ when mixed with blood;\
or _purulent_, when suppuration has occurred. The protective effects of\
the inflammatory reaction depend for the most part upon the transudation\
of lymph and the emigration of leucocytes. The lymph contains the\
opsonins which act on the bacteria and render them less able to resist\
the attack of the phagocytes, as well as the various protective\
antibodies which neutralise the toxins. The polymorph leucocytes are the\
principal agents in the process of phagocytosis (p. 22), and together\
with the other forms of phagocytes they ingest and destroy the bacteria.\
\
If the attempt to repel the invading organisms is successful, the\
irritant effects are overcome, the inflammation is arrested, and\
_resolution_ is said to take place.\
\
Certain of the vascular and cellular changes are now utilised to restore\
the condition to the normal, and _repair_ ensues after the manner\
already described. In certain situations, notably in tendon sheaths, in\
the cavities of joints, and in the interior of serous cavities, for\
example the pleura and peritoneum, the restoration to the normal is not\
perfect, adhesions forming between the opposing surfaces.\
\
If, however, the reaction induced by the infection is insufficient to\
check the growth and spread of the organisms, or to inhibit their toxin\
production, local necrosis of tissue may take place, either in the form\
of suppuration or of gangrene, or the toxins absorbed into the\
circulation may produce blood-poisoning, which may even prove fatal.\
\
#Clinical Aspects of Inflammation.#--It must clearly be understood that\
inflammation is not to be looked upon as a disease in itself, but rather\
as an evidence of some infective process going on in the tissues in\
which it occurs, and of an effort on the part of these tissues to\
overcome the invading organisms and their products. The chief danger to\
the patient lies, not in the reactive changes that constitute the\
inflammatory process, but in the fact that he is liable to be poisoned\
by the toxins of the bacteria at work in the inflamed area.\
\
Since the days of Celsus (first century A.D.), heat, redness, swelling,\
and pain have been recognised as cardinal signs of inflammation, and to\
these may be added, interference with function in the inflamed part, and\
general constitutional disturbance. Variations in these signs and\
symptoms depend upon the acuteness of the condition, the nature of the\
causative organism and of the tissue attacked, the situation of the part\
in relation to the surface, and other factors.\
\
The _heat_ of the inflamed part is to be attributed to the increased\
quantity of blood present in it, and the more superficial the affected\
area the more readily is the local increase of temperature detected by\
the hand. This clinical point is best tested by placing the palm of the\
hand and fingers for a few seconds alternately over an uninflamed and an\
inflamed area, otherwise under similar conditions as to coverings and\
exposure. In this way even slight differences may be recognised.\
\
_Redness_, similarly, is due to the increased afflux of blood to the\
inflamed part. The shade of colour varies with the stage of the\
inflammation, being lighter and brighter in the early, hyperaemic stages,\
and darker and duskier when the blood flow is slowed or when stasis has\
occurred and the oxygenation of the blood is defective. In the\
thrombotic stage the part may assume a purplish hue.\
\
The _swelling_ is partly due to the increased amount of blood in the\
affected part and to the accumulation of leucocytes and proliferated\
tissue cells, but chiefly to the exudate in the connective\
tissue--_inflammatory oedema_. The more open the structure of the tissue\
of the part, the greater is the amount of swelling--witness the marked\
degree of oedema that occurs in such parts as the scrotum or the eyelids.\
\
_Pain_ is a symptom seldom absent in inflammation. _Tenderness_--that\
is, pain elicited on pressure--is one of the most valuable diagnostic\
signs we possess, and is often present before pain is experienced by the\
patient. That the area of tenderness corresponds to the area of\
inflammation is almost an axiom of surgery. Pain and tenderness are due\
to the irritation of nerve filaments of the part, rendered all the more\
sensitive by the abnormal conditions of their blood supply. In\
inflammatory conditions of internal organs, for example the abdominal\
viscera, the pain is frequently referred to other parts, usually to an\
area supplied by branches from the same segment of the cord as that\
supplying the inflamed part.\
\
For purposes of diagnosis, attention should be paid to the terms in\
which the patient describes his pain. For example, the pain caused by\
an inflammation of the skin is usually described as of a _burning_ or\
_itching_ character; that of inflammation in dense tissues like\
periosteum or bone, or in encapsuled organs, as _dull_, _boring_, or\
_aching_. When inflammation is passing on to suppuration the pain\
assumes a _throbbing_ character, and as the pus reaches the surface, or\
"points," as it is called, sharp, _darting_, or _lancinating_ pains are\
experienced. Inflammation involving a nerve-trunk may cause a _boring_\
or a _tingling_ pain; while the implication of a serous membrane such as\
the pleura or peritoneum gives rise to a pain of a sharp, _stabbing_\
character.\
\
_Interference with the function_ of the inflamed part is always present\
to a greater or less extent.\
\
#Constitutional Disturbances.#--Under the term constitutional\
disturbances are included the presence of fever or elevation of\
temperature; certain changes in the pulse rate and the respiration;\
gastro-intestinal and urinary disturbances; and derangements of the\
central nervous system. These are all due to the absorption of toxins\
into the general circulation.\
\
_Temperature._--A marked rise of temperature is one of the most constant\
and important concomitants of acute inflammatory conditions, and the\
temperature chart forms a fairly reliable index of the state of the\
patient. The toxins interfere with the nerve-centres in the medulla that\
regulate the balance between the production and the loss of body heat.\
\
Clinically the temperature is estimated by means of a self-registering\
thermometer placed, for from one to five minutes, in close contact with\
the skin in the axilla, or in the mouth. Sometimes the thermometer is\
inserted into the rectum, where, however, the temperature is normally\
3/4 o F. higher than in the axilla.\
\
_In health_ the temperature of the body is maintained at a mean of about\
98.4 o F. (37 o C.) by the heat-regulating mechanism. It varies from hour\
to hour even in health, reaching its maximum between four and eight in\
the evening, when it may rise to 99 o F., and is at its lowest between\
four and six in the morning, when it may be about 97 o F.\
\
The temperature is more easily disturbed in children than in adults, and\
may become markedly elevated (104 o or 105 o F.) from comparatively slight\
causes; in the aged it is less liable to change, so that a rise to 103 o\
or 104 o F. is to be looked upon as indicating a high state of fever.\
\
A sudden rise of temperature is usually associated with a feeling of\
chilliness down the back and in the limbs, which may be so marked that\
the patient shivers violently, while the skin becomes cold, pale, and\
shrivelled--_cutis anserina_. This is a nervous reaction due to a want\
of correspondence between the internal and the surface temperature of\
the body, and is known clinically as a _rigor_. When the temperature\
rises gradually the chill is usually slight and may be unobserved. Even\
during the cold stage, however, the internal temperature is already\
raised, and by the time the chill has passed off its maximum has been\
reached.\
\
The _pulse_ is always increased in frequency, and usually varies\
directly with the height of the temperature. _Respiration_ is more\
active during the progress of an inflammation; and bronchial catarrh is\
common apart from any antecedent respiratory disease.\
\
_Gastro-intestinal disturbances_ take the form of loss of appetite,\
vomiting, diminished secretion of the alimentary juices, and weakening\
of the peristalsis of the bowel, leading to thirst, dry, furred tongue,\
and constipation. Diarrhoea is sometimes present. The _urine_ is usually\
scanty, of high specific gravity, rich in nitrogenous substances,\
especially urea and uric acid, and in calcium salts, while sodium\
chloride is deficient. Albumin and hyaline casts may be present in cases\
of severe inflammation with high temperature. The significance of\
general _leucocytosis_ has already been referred to.\
\
#General Principles of Treatment.#--The capacity of the inflammatory\
reaction for dealing with bacterial infections being limited, it often\
becomes necessary for the surgeon to aid the natural defensive\
processes, as well as to counteract the local and general effects of the\
reaction, and to relieve symptoms.\
\
The ideal means of helping the tissues is by removing the focus of\
infection, and when this can be done, as for example in a carbuncle or\
an anthrax pustule, the infected area may be completely excised. When\
the focus is not sufficiently limited to admit of this, the infected\
tissue may be scraped away with the sharp spoon, or destroyed by\
caustics or by the actual cautery. If this is inadvisable, the organisms\
may be attacked by strong antiseptics, such as pure carbolic acid.\
\
Moist dressings favour the removal of bacteria by promoting the escape\
of the inflammatory exudate, in which they are washed out.\
\
#Artificial Hyperaemia.#--When such direct means as the above are\
impracticable, much can be done to aid the tissues in their struggle by\
improving the condition of the circulation in the inflamed area, so as\
to ensure that a plentiful supply of fresh arterial blood reaches it.\
The beneficial effects of _hot fomentations and poultices_ depend on\
their causing a dilatation of the vessels, and so inducing a hyperaemia\
in the affected area. It has been shown experimentally that repeated,\
short applications of moist heat (not exceeding 106 o F.) are more\
efficacious than continuous application. It is now believed that the\
so-called _counter-irritants_--mustard, iodine, cantharides, actual\
cautery--act in the same way; and the method of treating erysipelas by\
applying a strong solution of iodine around the affected area is based\
on the same principle.\
\
[Illustration: FIG. 6.--Passive Hyperaemia of Hand and Forearm induced by\
Bier's Bandage.]\
\
While these and similar methods have long been employed in the treatment\
of inflammatory conditions, it is only within comparatively recent years\
that their mode of action has been properly understood, and to August\
Bier belongs the credit of having put the treatment of inflammation on a\
scientific and rational basis. Recognising the "beneficent intention" of\
the inflammatory reaction, and the protective action of the leucocytosis\
which accompanies the hyperaemic stages of the process, Bier was led to\
study the effects of increasing the hyperaemia by artificial means. As a\
result of his observations, he has formulated a method of treatment\
which consists in inducing an artificial hyperaemia in the inflamed area,\
either by obstructing the venous return from the part (_passive\
hyperaemia_), or by stimulating the arterial flow through it (_active\
hyperaemia_).\
\
_Bier's Constricting Bandage._--To induce a _passive hyperaemia_ in a\
limb, an elastic bandage is applied some distance above the inflamed\
area sufficiently tightly to obstruct the venous return from the distal\
parts without arresting in any way the inflow of arterial blood (Fig. 6).\
If the constricting band is correctly applied, the parts beyond\
become swollen and oedematous, and assume a bluish-red hue, but they\
retain their normal temperature, the pulse is unchanged, and there is no\
pain. If the part becomes blue, cold, or painful, or if any existing\
pain is increased, the band has been applied too tightly. The hyperaemia\
is kept up from twenty to twenty-two hours out of the twenty-four, and\
in the intervals the limb is elevated to get rid of the oedema and to\
empty it of impure blood, and so make room for a fresh supply of healthy\
blood when the bandage is re-applied. As the inflammation subsides, the\
period during which the band is kept on each day is diminished; but the\
treatment should be continued for some days after all signs of\
inflammation have subsided.\
\
This method of treating acute inflammatory conditions necessitates\
close supervision until the correct degree of tightness of the band has\
been determined.\
\
[Illustration: FIG. 7.--Passive Hyperaemia of Finger induced by Klapp's\
Suction Bell.]\
\
_Klapp's Suction Bells._--In inflammatory conditions to which the\
constricting band cannot be applied, as for example an acute mastitis, a\
bubo in the groin, or a boil on the neck, the affected area may be\
rendered hyperaemic by an appropriately shaped glass bell applied over it\
and exhausted by means of a suction-pump, the rarefaction of the air in\
the bell determining a flow of blood into the tissues enclosed within it\
(Figs. 7 and 8). The edge of the bell is smeared with vaseline, and the\
suction applied for from five to ten minutes at a time, with a\
corresponding interval between the applications. Each sitting lasts for\
from half an hour to an hour, and the treatment may be carried out once\
or twice a day according to circumstances. This apparatus acts in the\
same way as the old-fashioned _dry cup_, and is more convenient and\
equally efficacious.\
\
[Illustration: FIG. 8.--Passive Hyperaemia induced by Klapp's Suction\
Bell for Inflammation of Inguinal Gland.]\
\
_Active hyperaemia_ is induced by the local application of heat,\
particularly by means of hot air. It has not proved so useful in acute\
inflammation as passive hyperaemia, but is of great value in hastening\
the absorption of inflammatory products and in overcoming adhesions and\
stiffness in tendons and joints.\
\
_General Treatment._--The patient should be kept at rest, preferably in\
bed, to diminish the general tissue waste; and the diet should be\
restricted to fluids, such as milk, beef-tea, meat juices or gruel, and\
these may be rendered more easily assimilable by artificial digestion if\
necessary. To counteract the general effect of toxins absorbed into\
the circulation, specific antitoxic sera are employed in certain forms\
of infection, such as diphtheria, streptococcal septicaemia, and tetanus.\
In other forms of infection, vaccines are employed to increase the\
opsonic power of the blood. When such means are not available, the\
circulating toxins may to some extent be diluted by giving plenty of\
bland fluids by the mouth or normal salt solution by the rectum.\
\
The elimination of the toxins is promoted by securing free action of the\
emunctories. A saline purge, such as half an ounce of sulphate of\
magnesium in a small quantity of water, ensures a free evacuation of the\
bowels. The kidneys are flushed by such diluent drinks as equal parts of\
milk and lime water, or milk with a dram of liquor calcis saccharatus\
added to each tumblerful. Barley-water and "Imperial drink," which\
consists of a dram and a half of cream of tartar added to a pint of\
boiling water and sweetened with sugar after cooling, are also useful\
and non-irritating diuretics. The skin may be stimulated by Dover's\
powder (10 grains) or liquor ammoniae acetatis in three-dram doses every\
four hours.\
\
Various drugs administered internally, such as quinine, salol,\
salicylate of iron, and others, have a reputation, more or less\
deserved, as internal antiseptics.\
\
Weakness of the heart, as indicated by the condition of the pulse, is\
treated by the use of such drugs as digitalis, strophanthus, or\
strychnin, according to circumstances.\
\
Gastro-intestinal disturbances are met by ordinary medical means.\
Vomiting, for example, can sometimes be checked by effervescing drinks,\
such as citrate of caffein, or by dilute hydrocyanic acid and bismuth.\
In severe cases, and especially when the vomited matter resembles\
coffee-grounds from admixture with altered blood--the so-called\
post-operative haematemesis--the best means of arresting the vomiting is\
by washing out the stomach. Thirst is relieved by rectal injections of\
saline solution. The introduction of saline solution into the veins or\
by the rectum is also useful in diluting and hastening the elimination\
of circulating toxins.\
\
In surgical inflammations, as a rule, nothing is gained by lowering the\
temperature, unless at the same time the cause is removed. When severe\
or prolonged pyrexia becomes a source of danger, the use of hot or cold\
sponging, or even the cold bath, is preferable to the administration of\
drugs.\
\
_Relief of Symptoms._--For the relief of _pain_, rest is essential. The\
inflamed part should be placed in a splint or other appliance which will\
prevent movement, and steps must be taken to reduce its functional\
activity as far as possible. Locally, warm and moist dressings, such as\
a poultice or fomentation, may be used. To make a fomentation, a piece\
of flannel or lint is wrung out of very hot water or antiseptic lotion\
and applied under a sheet of mackintosh. Fomentations should be renewed\
as often as they cool. An ordinary india-rubber bag filled with hot\
water and fixed over the fomentation, by retaining the heat, obviates\
the necessity of frequently changing the application. The addition of a\
few drops of laudanum sprinkled on the flannel has a soothing effect.\
Lead and opium lotion is a useful, soothing application employed as a\
fomentation. We prefer the application of lint soaked in a 10 per cent.\
aqueous or glycerine solution of ichthyol, or smeared with ichthyol\
ointment (1 in 3). Belladonna and glycerine, equal parts, may be used.\
\
Dry cold obtained by means of icebags, or by Leiter's lead tubes through\
which a continuous stream of ice-cold water is kept flowing, is\
sometimes soothing to the patient, but when the vessels in the inflamed\
part are greatly congested its use is attended with considerable risk,\
as it not only contracts the arterioles supplying the part, but also\
diminishes the outflow of venous blood, and so may determine gangrene of\
tissues already devitalised.\
\
A milder form of employing cold is by means of evaporating lotions: a\
thin piece of lint or gauze is applied over the inflamed part and kept\
constantly moist with the lotion, the dressing being left freely exposed\
to allow of continuous evaporation. A useful evaporating lotion is made\
up as follows: take of chloride of ammonium, half an ounce; rectified\
spirit, one ounce; and water, seven ounces.\
\
The administration of opiates may be necessary for the relief of pain.\
\
The accumulation of an excessive amount of inflammatory exudate may\
endanger the vitality of the tissues by pressing on the blood vessels to\
such an extent as to cause stasis, and by concentrating the local action\
of the toxins. Under such conditions the tension should be relieved and\
the exudate with its contained toxins removed by making an incision into\
the inflamed tissues, and applying a suction bell. When the exudate has\
collected in a synovial cavity, such as a joint or bursa, it may be\
withdrawn by means of a trocar and cannula. There are other methods of\
withdrawing blood and exudate from an inflamed area, for example by\
leeches or wet-cupping, but they are seldom employed now.\
\
Before applying leeches the part must be thoroughly cleansed, and if\
the leech is slow to bite, may be smeared with cream. The leech is\
retained in position under an inverted wine-glass or wide test-tube till\
it takes hold. After it has sucked its fill it usually drops off, having\
withdrawn a dram or a dram and a half of blood. If it be desirable to\
withdraw more blood, hot fomentations should be applied to the bite. As\
it is sometimes necessary to employ considerable pressure to stop the\
bleeding, leeches should, if possible, be applied over a bone which will\
furnish the necessary resistance. The use of styptics may be called for.\
\
_Wet-cupping_ has almost entirely been superseded by the use of Klapp's\
suction bells.\
\
_General blood-letting_ consists in opening a superficial vein\
(venesection) and allowing from eight to ten ounces of blood to flow\
from it. It is seldom used in the treatment of surgical forms of\
inflammation.\
\
_Counter-irritants._--In deep-seated inflammations, counter-irritants\
are sometimes employed in the form of mustard leaves or blisters,\
according to the degree of irritation required. A mustard leaf or\
plaster should not be left on longer than ten or fifteen minutes, unless\
it is desired to produce a blister. Blistering may be produced by a\
_cantharides plaster_, or by painting with _liquor epispasticus_. The\
plaster should be left on from eight to ten hours, and if it has failed\
to raise a blister, a hot fomentation should be applied to the part.\
_Liquor epispasticus_, alone or mixed with equal parts of collodion, is\
painted on the part with a brush. Several paintings are often required\
before a blister is raised. The preliminary removal of the natural\
grease from the skin favours the action of these applications.\
\
The treatment of inflammation in special tissues and organs will be\
considered in the sections devoted to regional surgery.\
\
#Chronic Inflammation.#--A variety of types of chronic and subacute\
inflammation are met with which, owing to ignorance of their causations,\
cannot at present be satisfactorily classified.\
\
The best defined group is that of the _granulomata_, which includes such\
important diseases as tuberculosis and syphilis, and in which different\
types of chronic inflammation are caused by infection with a specific\
organism, all having the common character, however, that abundant\
granulation tissue is formed in which cellular changes are more in\
evidence than changes in the blood vessels, and in which the subsequent\
degeneration and necrosis of the granulation tissue results in the\
breaking down and destruction of the tissue in which it is formed.\
Another group is that in which chronic inflammation is due to mild or\
attenuated forms of pyogenic infection affecting especially the lymph\
glands and the bone marrow. In the glands of the groin, for example,\
associated with various forms of irritation about the external genitals,\
different types of _chronic lymphadenitis_ are met with; they do not\
frankly suppurate as do the acute types, but are attended with a\
hyperplasia of the tissue elements which results in enlargement of the\
affected glands of a persistent, and sometimes of a relapsing character.\
Similar varieties of _osteomyelitis_ are met with that do not, like the\
acute forms, go on to suppuration or to death of bone, but result in\
thickening of the bone affected, both on the surface and in the\
interior, resulting in obliteration of the medullary canal.\
\
A third group of chronic inflammations are those that begin as an acute\
pyogenic inflammation, which, instead of resolving completely, persists\
in a chronic form. It does so apparently because there is some factor\
aiding the organisms and handicapping the tissues, such as the presence\
of a foreign body, a piece of glass or metal, or a piece of dead bone;\
in these circumstances the inflammation persists in a chronic form,\
attended with the formation of fibrous tissue, and, in the case of bone,\
with the formation of new bone in excess. It will be evident that in\
this group, chronic inflammation and repair are practically\
interchangeable terms.\
\
There are other groups of chronic inflammation, the origin of which\
continues to be the subject of controversy. Reference is here made to\
the chronic inflammations of the synovial membrane of joints, of tendon\
sheaths and of bursae--_chronic synovitis_, _teno-synovitis_ and\
_bursitis_; of the fibrous tissues of joints--chronic forms of\
_arthritis_; of the blood vessels--chronic forms of _endarteritis_ and\
of _phlebitis_ and of the peripheral nerves--_neuritis_. Also in the\
breast and in the prostate, with the waning of sexual life there may\
occur a formation of fibrous tissue--chronic _interstitial mastitis_,\
_chronic prostatitis_, having analogies with the chronic interstitial\
inflammations of internal organs like the kidney--_chronic interstitial\
nephritis_; and in the breast and prostate, as in the kidney, the\
formation of fibrous tissue leads to changes in the secreting epithelium\
resulting in the formation of cysts.\
\
Lastly, there are still other types of chronic inflammation attended\
with the formation of fibrous tissue on such a liberal scale as to\
suggest analogies with new growths. The best known of these are the\
systematic forms of fibromatosis met with in the central nervous system\
and in the peripheral nerves--_neuro-fibromatosis_; in the submucous\
coat of the stomach--_gastric fibromatosis_; and in the\
colon--_intestinal fibromatosis_.\
\
These conditions will be described with the tissues and organs in which\
they occur.\
\
In the _treatment of chronic inflammations_, pending further knowledge\
as to their causation, and beyond such obvious indications as to help\
the tissues by removing a foreign body or a piece of dead bone, there\
are employed--empirically--a number of procedures such as the induction\
of hyperaemia, exposure to the X-rays, and the employment of blisters,\
cauteries, and setons. Vaccines may be had recourse to in those of\
bacterial origin.\
\
\
\
\
CHAPTER IV\
\
SUPPURATION\
\
\
Definition--Pus--_Varieties_--Acute circumscribed abscess--_Acute\
    suppuration in a wound_--_Acute Suppuration in a mucous\
    membrane_--Diffuse cellulitis and diffuse suppuration--\
    _Whitlow_--_Suppurative cellulitis in different situations_--Chronic\
    suppuration--Sinus, Fistula--Constitutional manifestations of\
    pyogenic infection--_Sapraemia_--_Septicaemia_--_Pyaemia_.\
\
Suppuration, or the formation of pus, is one of the results of the\
action of bacteria on the tissues. The invading organism is usually one\
of the staphylococci, less frequently a streptococcus, and still less\
frequently one of the other bacteria capable of producing pus, such as\
the bacillus coli communis, the gonococcus, the pneumococcus, or the\
typhoid bacillus.\
\
So long as the tissues are in a healthy condition they are able to\
withstand the attacks of moderate numbers of pyogenic bacteria of\
ordinary virulence, but when devitalised by disease, by injury, or by\
inflammation due to the action of other pathogenic organisms,\
suppuration ensues.\
\
It would appear, for example, that pyogenic organisms can pass through\
the healthy urinary tract without doing any damage, but if the pelvis of\
the kidney, the ureter, or the bladder is the seat of stone, they give\
rise to suppuration. Similarly, a calculus in one of the salivary ducts\
frequently results in an abscess forming in the floor of the mouth. When\
the lumen of a tubular organ, such as the appendix or the Fallopian tube\
is blocked also, the action of pyogenic organisms is favoured and\
suppuration ensues.\
\
#Pus.#--The fluid resulting from the process of suppuration is known\
as _pus_. In its typical form it is a yellowish creamy substance, of\
alkaline reaction, with a specific gravity of about 1030, and it has a\
peculiar mawkish odour. If allowed to stand in a test-tube it does not\
coagulate, but separates into two layers: the upper, transparent,\
straw-coloured fluid, the _liquor puris_ or pus serum, closely\
resembling blood serum in its composition, but containing less protein\
and more cholestrol; it also contains leucin, tyrosin, and certain\
albumoses which prevent coagulation.\
\
The layer at the bottom of the tube consists for the most part of\
polymorph leucocytes, and proliferated connective tissue and endothelial\
cells (_pus corpuscles_). Other forms of leucocytes may be present,\
especially in long-standing suppurations; and there are usually some red\
corpuscles, dead bacteria, fat cells and shreds of tissue, cholestrol\
crystals, and other detritus in the deposit.\
\
If a film of fresh pus is examined under the microscope, the pus cells\
are seen to have a well-defined rounded outline, and to contain a finely\
granular protoplasm and a multi-partite nucleus; if still warm, the\
cells may exhibit amoeboid movement. In stained films the nuclei take the\
stain well. In older pus cells the outline is irregular, the protoplasm\
coarsely granular, and the nuclei disintegrated, no longer taking the\
stain.\
\
_Variations from Typical Pus._--Pus from old-standing sinuses is often\
watery in consistence (ichorous), with few cells. Where the granulations\
are vascular and bleed easily, it becomes sanious from admixture with\
red corpuscles; while, if a blood-clot be broken down and the debris\
mixed with the pus, it contains granules of blood pigment and is said to\
be "grumous." The _odour_ of pus varies with the different bacteria\
producing it. Pus due to ordinary pyogenic cocci has a mawkish odour;\
when putrefactive organisms are present it has a putrid odour; when it\
forms in the vicinity of the intestinal canal it usually contains the\
bacillus coli communis and has a faecal odour.\
\
The _colour_ of pus also varies: when due to one or other of the\
varieties of the bacillus pyocyaneus, it is usually of a blue or green\
colour; when mixed with bile derivatives or altered blood pigment, it\
may be of a bright orange colour. In wounds inflicted with rough iron\
implements from which rust is deposited, the pus often presents the same\
colour.\
\
The pus may form and collect within a circumscribed area, constituting a\
localised _abscess_; or it may infiltrate the tissues over a wide\
area--_diffuse suppuration_.\
\
\
ACUTE CIRCUMSCRIBED ABSCESS\
\
Any tissue of the body may be the seat of an acute abscess, and there\
are many routes by which the bacteria may gain access to the affected\
area. For example: an abscess in the integument or subcutaneous\
cellular tissue usually results from infection by organisms which have\
entered through a wound or abrasion of the surface, or along the ducts\
of the skin; an abscess in the breast from organisms which have passed\
along the milk ducts opening on the nipple, or along the lymphatics\
which accompany these. An abscess in a lymph gland is usually due to\
infection passing by way of the lymph channels from the area of skin or\
mucous membrane drained by them. Abscesses in internal organs, such as\
the kidney, liver, or brain, usually result from organisms carried in\
the blood-stream from some focus of infection elsewhere in the body.\
\
A knowledge of the possible avenues of infection is of clinical\
importance, as it may enable the source of a given abscess to be traced\
and dealt with. In suppuration in the Fallopian tube (pyosalpynx), for\
example, the fact that the most common origin of the infection is in the\
genital passage, leads to examination for vaginal discharge; and if none\
is present, the abscess is probably due to infection carried in the\
blood-stream from some primary focus about the mouth, such as a gumboil\
or an infective sore throat.\
\
The exact location of an abscess also may furnish a key to its source;\
in axillary abscess, for example, if the suppuration is in the lymph\
glands the infection has come through the afferent lymphatics; if in the\
cellular tissue, it has spread from the neck or chest wall; if in the\
hair follicles, it is a local infection through the skin.\
\
#Formation of an Abscess.#--When pyogenic bacteria are introduced into\
the tissue there ensues an inflammatory reaction, which is characterised\
by dilatation of the blood vessels, exudation of large numbers of\
leucocytes, and proliferation of connective-tissue cells. These\
wandering cells soon accumulate round the focus of infection, and form a\
protective barrier which tends to prevent the spread of the organisms\
and to restrict their field of action. Within the area thus\
circumscribed the struggle between the bacteria and the phagocytes takes\
place, and in the process toxins are formed by the organisms, a certain\
number of the leucocytes succumb, and, becoming degenerated, set free\
certain proteolytic enzymes or ferments. The toxins cause\
coagulation-necrosis of the tissue cells with which they come in\
contact, the ferments liquefy the exudate and other albuminous\
substances, and in this way _pus_ is formed.\
\
If the bacteria gain the upper hand, this process of liquefaction which\
is characteristic of suppuration, extends into the surrounding tissues,\
the protective barrier of leucocytes is broken down, and the\
suppurative process spreads. A fresh accession of leucocytes, however,\
forms a new barrier, and eventually the spread is arrested, and the\
collection of pus so hemmed in constitutes an _abscess_.\
\
Owing to the swelling and condensation of the parts around, the pus thus\
formed is under considerable pressure, and this causes it to burrow\
along the lines of least resistance. In the case of a subcutaneous\
abscess the pus usually works its way towards the surface, and "points,"\
as it is called. Where it approaches the surface the skin becomes soft\
and thin, and eventually sloughs, allowing the pus to escape.\
\
An abscess forming in the deeper planes is prevented from pointing\
directly to the surface by the firm fasciae and other fibrous structures.\
The pus therefore tends to burrow along the line of the blood vessels\
and in the connective-tissue septa, till it either finds a weak spot or\
causes a portion of fascia to undergo necrosis and so reaches the\
surface. Accordingly, many abscess cavities resulting from deep-seated\
suppuration are of irregular shape, with pouches and loculi in various\
directions--an arrangement which interferes with their successful\
treatment by incision and drainage.\
\
The relief of tension which follows the bursting of an abscess, the\
removal of irritation by the escape of pus, and the casting off of\
bacteria and toxins, allow the tissues once more to assert themselves,\
and a process of repair sets in. The walls of the abscess fall in;\
granulation tissue grows into the space and gradually fills it; and\
later this is replaced by cicatricial tissue. As a result of the\
subsequent contraction of the cicatricial tissue, the scar is usually\
depressed below the level of the surrounding skin surface.\
\
If an abscess is prevented from healing--for example, by the presence of\
a foreign body or a piece of necrosed bone--a sinus results, and from it\
pus escapes until the foreign body is removed.\
\
#Clinical Features of an Acute Circumscribed Abscess.#--In the initial\
stages the usual symptoms of inflammation are present. Increased\
elevation of temperature, with or without a rigor, progressive\
leucocytosis, and sweating, mark the transition between inflammation and\
suppuration. An increasing leucocytosis is evidence that a suppurative\
process is spreading.\
\
The local symptoms vary with the seat of the abscess. When it is\
situated superficially--for example, in the breast tissue--the affected\
area is hot, the redness of inflammation gives place to a dusky purple\
colour, with a pale, sometimes yellow, spot where the pus is near the\
surface. The swelling increases in size, the firm brawny centre becomes\
soft, projects as a cone beyond the level of the rest of the swollen\
area, and is usually surrounded by a zone of induration.\
\
By gently palpating with the finger-tips over the softened area, a fluid\
wave may be detected--_fluctuation_--and when present this is a certain\
indication of the existence of fluid in the swelling. Its recognition,\
however, is by no means easy, and various fallacies are to be guarded\
against in applying this test clinically. When, for example, the walls\
of the abscess are thick and rigid, or when its contents are under\
excessive tension, the fluid wave cannot be elicited. On the other hand,\
a sensation closely resembling fluctuation may often be recognised in\
oedematous tissues, in certain soft, solid tumours such as fatty tumours\
or vascular sarcomata, in aneurysm, and in a muscle when it is palpated\
in its transverse axis.\
\
When pus has formed in deeper parts, and before it has reached the\
surface, oedema of the overlying skin is frequently present, and the skin\
pits on pressure.\
\
With the formation of pus the continuous burning or boring pain of\
inflammation assumes a throbbing character, with occasional sharp,\
lancinating twinges. Should doubt remain as to the presence of pus,\
recourse may be had to the use of an exploring needle.\
\
_Differential Diagnosis of Acute Abscess._--A practical difficulty which\
frequently arises is to decide whether or not pus has actually formed.\
It may be accepted as a working rule in practice that when an acute\
inflammation has lasted for four or five days without showing signs of\
abatement, suppuration has almost certainly occurred. In deep-seated\
suppuration, marked oedema of the skin and the occurrence of rigors and\
sweating may be taken to indicate the formation of pus.\
\
There are cases on record where rapidly growing sarcomatous and\
angiomatous tumours, aneurysms, and the bruises that occur in\
haemophylics, have been mistaken for acute abscesses and incised, with\
disastrous results.\
\
#Treatment of Acute Abscesses.#--The dictum of John Bell, "Where there\
is pus, let it out," summarises the treatment of abscess. The extent and\
situation of the incision and the means taken to drain the cavity,\
however, vary with the nature, site, and relations of the abscess. In a\
superficial abscess, for example a bubo, or an abscess in the breast or\
face where a disfiguring scar is undesirable, a small puncture should be\
made where the pus threatens to point, and a Klapp's suction bell be\
applied as already described (p. 39). A drain is not necessary, and in\
the intervals between the applications of the bell the part is covered\
with a moist antiseptic dressing.\
\
In abscesses deeply placed, as for example under the gluteal or pectoral\
muscles, one or more incisions should be made, and the cavity drained by\
glass or rubber tubes or by strips of rubber tissue.\
\
The wound should be dressed the next day, and the tube shortened, in the\
case of a rubber tube, by cutting off a portion of its outer end. On the\
second day or later, according to circumstances, the tube is removed,\
and after this the dressing need not be repeated oftener than every\
second or third day.\
\
Where pus has formed in relation to important structures--as, for\
example, in the deeper planes of the neck--_Hilton's method_ of opening\
the abscess may be employed. An incision is made through the skin and\
fascia, a grooved director is gently pushed through the deeper tissues\
till pus escapes along its groove, and then the track is widened by\
passing in a pair of dressing forceps and expanding the blades. A tube,\
or strip of rubber tissue, is introduced, and the subsequent treatment\
carried out as in other abscesses. When the drain lies in proximity to a\
large blood vessel, care must be taken not to leave it in position long\
enough to cause ulceration of the vessel wall by pressure.\
\
In some abscesses, such as those in the vicinity of the anus, the cavity\
should be laid freely open in its whole extent, stuffed with iodoform or\
bismuth gauze, and treated by the open method.\
\
It is seldom advisable to wash out an abscess cavity, and squeezing out\
the pus is also to be avoided, lest the protective zone be broken down\
and the infection be diffused into the surrounding tissues.\
\
The importance of taking precautions against further infection in\
opening an abscess can scarcely be exaggerated, and the rapidity with\
which healing occurs when the access of fresh bacteria is prevented is\
in marked contrast to what occurs when such precautions are neglected\
and further infection is allowed to take place.\
\
_Acute Suppuration in a Wound._--If in the course of an operation\
infection of the wound has occurred, a marked inflammatory reaction soon\
manifests itself, and the same changes as occur in the formation of an\
acute abscess take place, modified, however, by the fact that the pus\
can more readily reach the surface. In from twenty-four to forty-eight\
hours the patient is conscious of a sensation of chilliness, or may\
even have a rigor. At the same time he feels generally out of sorts,\
with impaired appetite, headache, and it may be looseness of the bowels.\
His temperature rises to 100 o or 101 o F., and the pulse quickens to 100\
or 110.\
\
On exposing the wound it is found that the parts for some distance\
around are red, glazed, and oedematous. The discoloration and swelling\
are most intense in the immediate vicinity of the wound, the edges of\
which are everted and moist. Any stitches that may have been introduced\
are tight, and the deep ones may be cutting into the tissues. There is\
heat, and a constant burning or throbbing pain, which is increased by\
pressure. If the stitches be cut, pus escapes, the wound gapes, and its\
surfaces are found to be inflamed and covered with pus.\
\
The open method is the only safe means of treating such wounds. The\
infected surface may be sponged over with pure carbolic acid, the excess\
of which is washed off with absolute alcohol, and the wound either\
drained by tubes or packed with iodoform gauze. The practice of scraping\
such surfaces with the sharp spoon, squeezing or even of washing them\
out with antiseptic lotions, is attended with the risk of further\
diffusing the organisms in the tissue, and is only to be employed under\
exceptional circumstances. Continuous irrigation of infected wounds or\
their immersion in antiseptic baths is sometimes useful. The free\
opening up of the wound is almost immediately followed by a fall in the\
temperature. The surrounding inflammation subsides, the discharge of pus\
lessens, and healing takes place by the formation of granulation\
tissue--the so-called "healing by second intention."\
\
Wound infection may take place from _catgut_ which has not been\
efficiently prepared. The local and general reactions may be slight,\
and, as a rule, do not appear for seven or eight days after the\
operation, and, it may be, not till after the skin edges have united.\
The suppuration is strictly localised to the part of the wound where\
catgut was employed for stitches or ligatures, and shows little tendency\
to spread. The infected part, however, is often long of healing. The\
irritation in these cases is probably due to toxins in the catgut and\
not to bacteria.\
\
When suppuration occurs in connection with buried sutures of\
unabsorbable materials, such as silk, silkworm gut, or silver wire, it\
is apt to persist till the foreign material is cast off or removed.\
\
Suppuration may occur in the track of a skin stitch, producing a _stitch\
abscess_. The infection may arise from the material used, especially\
catgut or silk, or, more frequently perhaps, from the growth of\
staphylococcus albus from the skin of the patient when this has been\
imperfectly disinfected. The formation of pus under these conditions may\
not be attended with any of the usual signs of suppuration, and beyond\
some induration around the wound and a slight tenderness on pressure\
there may be nothing to suggest the presence of an abscess.\
\
_Acute Suppuration of a Mucous Membrane._--When pyogenic organisms gain\
access to a mucous membrane, such as that of the bladder, urethra, or\
middle ear, the usual phenomena of acute inflammation and suppuration\
ensue, followed by the discharge of pus on the free surface. It would\
appear that the most marked changes take place in the submucous tissue,\
causing the covering epithelium in places to die and leave small\
superficial ulcers, for example in gonorrhoeal urethritis, the\
cicatricial contraction of the scar subsequently leading to the\
formation of stricture. When mucous glands are present in the membrane,\
the pus is mixed with mucus--_muco-pus_.\
\
\
DIFFUSE CELLULITIS AND DIFFUSE SUPPURATION\
\
Cellulitis is an acute affection resulting from the introduction of some\
organism--commonly the _streptococcus pyogenes_--into the cellular\
connective tissue of the integument, intermuscular septa, tendon\
sheaths, or other structures. Infection always takes place through a\
breach of the surface, although this may be superficial and\
insignificant, such as a pin-prick, a scratch, or a crack under a nail,\
and the wound may have been healed for some time before the inflammation\
becomes manifest. The cellulitis, also, may develop at some distance\
from the seat of inoculation, the organisms having travelled by the\
lymphatics.\
\
The virulence of the organisms, the loose, open nature of the tissues in\
which they develop, and the free lymphatic circulation by means of which\
they are spread, account for the diffuse nature of the process.\
Sometimes numbers of cocci are carried for a considerable distance from\
the primary area before they are arrested in the lymphatics, and thus\
several patches of inflammation may appear with healthy areas between.\
\
The pus infiltrates the meshes of the cellular tissue, there is\
sloughing of considerable portions of tissue of low vitality, such as\
fat, fascia, or tendon, and if the process continues for some time\
several collections of pus may form.\
\
_Clinical Features._--The reaction in cases of diffuse cellulitis is\
severe, and is usually ushered in by a distinct chill or even a rigor,\
while the temperature rises to 103 o, 104 o, or 105 o F. The pulse is\
proportionately increased in frequency, and is small, feeble, and often\
irregular. The face is flushed, the tongue dry and brown, and the\
patient may become delirious, especially during the night. Leucocytosis\
is present in cases of moderate severity; but in severe cases the\
virulence of the toxins prevents reaction taking place, and leucocytosis\
is absent.\
\
The local manifestations vary with the relation of the seat of the\
inflammation to the surface. When the superficial cellular tissue is\
involved, the skin assumes a dark bluish-red colour, is swollen,\
oedematous, and the seat of burning pain. To the touch it is firm, hot,\
and tender. When the primary focus is in the deeper tissues, the\
constitutional disturbance is aggravated, while the local signs are\
delayed, and only become prominent when pus forms and approaches the\
surface. It is not uncommon for blebs containing dark serous fluid to\
form on the skin. The infection frequently spreads along the line of the\
main lymph vessels of the part (_septic lymphangitis_) and may reach the\
lymph glands (_septic lymphadenitis_).\
\
With the formation of pus the skin becomes soft and boggy at several\
points, and eventually breaks, giving exit to a quantity of thick\
grumous discharge. Sometimes several small collections under the skin\
fuse, and an abscess is formed in which fluctuation can be detected.\
Occasionally gases are evolved in the tissues, giving rise to emphysema.\
It is common for portions of fascia, ligaments, or tendons to slough,\
and this may often be recognised clinically by a peculiar crunching or\
grating sensation transmitted to the fingers on making firm pressure on\
the part.\
\
If it is not let out by incision, the pus, travelling along the lines of\
least resistance, tends to point at several places on the surface, or to\
open into joints or other cavities.\
\
_Prognosis._--The occurrence of _septicaemia_ is the most serious risk,\
and it is in cases of diffuse suppurative cellulitis that this form of\
blood-poisoning assumes its most aggravated forms. The toxins of the\
streptococci are exceedingly virulent, and induce local death of tissue\
so rapidly that the protective emigration of leucocytes fails to take\
place. In some cases the passage of masses of free cocci in the\
lymphatics, or of infective emboli in the blood vessels, leads to the\
formation of _pyogenic abscesses_ in vital organs, such as the brain,\
lungs, liver, kidneys, or other viscera. _Haemorrhage_ from erosion of\
arterial or venous trunks may take place and endanger life.\
\
_Treatment._--The treatment of diffuse cellulitis depends to a large\
extent on the situation and extent of the affected area, and on the\
stage of the process.\
\
_In the limbs_, for example, where the application of a constricting\
band is practicable, Bier's method of inducing passive hyperaemia yields\
excellent results. If pus is formed, one or more small incisions are\
made and a light moist dressing placed over the wounds to absorb the\
discharge, but no drain is inserted. The whole of the inflamed area\
should be covered with gauze wrung out of a 1 in 10 solution of ichthyol\
in glycerine. The dressing is changed as often as necessary, and in the\
intervals when the band is off, gentle active and passive movements\
should be carried out to prevent the formation of adhesions. After\
incisions have been made, we have found the _immersion_ of the limb, for\
a few hours at a time, in a water-bath containing warm boracic lotion or\
eusol a useful adjuvant to the passive hyperaemia.\
\
_Continuous irrigation_ of the part by a slow, steady stream of lotion,\
at the body temperature, such as eusol, or Dakin's solution, or boracic\
acid, or frequent washing with peroxide of hydrogen, has been found of\
value.\
\
A suitably arranged splint adds to the comfort of the patient; and the\
limb should be placed in the attitude which, in the event of stiffness\
resulting, will least interfere with its usefulness. The elbow, for\
example, should be flexed to a little less than a right angle; at the\
wrist, the hand should be dorsiflexed and the fingers flexed slightly\
towards the palm.\
\
Massage, passive movement, hot and cold douching, and other measures,\
may be necessary to get rid of the chronic oedema, adhesions of tendons,\
and stiffness of joints which sometimes remain.\
\
In situations where a constricting band cannot be applied, for example,\
on the trunk or the neck, Klapp's suction bells may be used, small\
incisions being made to admit of the escape of pus.\
\
If these measures fail or are impracticable, it may be necessary to make\
one or more free incisions, and to insert drainage-tubes, portions of\
rubber dam, or iodoform worsted.\
\
The general treatment of toxaemia must be carried out, and in cases due\
to infection by streptococci, anti-streptococcic serum may be used.\
\
In a few cases, amputation well above the seat of disease, by removing\
the source of toxin production, offers the only means of saving the\
patient.\
\
\
WHITLOW\
\
The clinical term whitlow is applied to an acute infection, usually\
followed by suppuration, commonly met with in the fingers, less\
frequently in the toes. The point of infection is often trivial--a\
pin-prick, a puncture caused by a splinter of wood, a scratch, or even\
an imperceptible lesion of the skin.\
\
Several varieties of whitlow are recognised, but while it is convenient\
to describe them separately, it is to be clearly understood that\
clinically they merge one into another, and it is not always possible to\
determine in which connective-tissue plane a given infection has\
originated.\
\
_Initial Stage._--Attention is usually first attracted to the condition\
by a sensation of tightness in the finger and tenderness when the part\
is squeezed or knocked against anything. In the course of a few hours\
the part becomes red and swollen; there is continuous pain, which soon\
assumes a throbbing character, particularly when the hand is dependent,\
and may be so severe as to prevent sleep, and the patient may feel\
generally out of sorts.\
\
If a constricting band is applied at this stage, the infection can\
usually be checked and the occurrence of suppuration prevented. If this\
fails, or if the condition is allowed to go untreated, the inflammatory\
reaction increases and terminates in suppuration, giving rise to one or\
other of the forms of whitlow to be described.\
\
_The Purulent Blister._--In the most superficial variety, pus forms\
between the rete Malpighii and the stratum corneum of the skin, the\
latter being raised as a blister in which fluctuation can be detected\
(Fig. 9, a). This is commonly met with in the palm of the hand of\
labouring men who have recently resumed work after a spell of idleness.\
When the blister forms near the tip of the finger, the pus burrows under\
the nail--which corresponds to the stratum corneum--raising it from its\
bed.\
\
There is some local heat and discoloration, and considerable pain and\
tenderness, but little or no constitutional disturbance. Superficial\
lymphangitis may extend a short distance up the forearm. By clipping\
away the raised epidermis, and if necessary the nail, the pus is allowed\
to escape, and healing speedily takes place.\
\
_Whitlow at the Nail Fold._--This variety, which is met with among those\
who handle septic material, occurs in the sulcus between the nail and\
the skin, and is due to the introduction of infective matter at the root\
of the nail (Fig. 9, b). A small focus of suppuration forms under the\
nail, with swelling and redness of the nail fold, causing intense pain\
and discomfort, interfering with sleep, and producing a constitutional\
reaction out of all proportion to the local lesion.\
\
To allow the pus to escape, it is necessary, under local anaesthesia, to\
cut away the nail fold as well as the portion of nail in the infected\
area, or, it may be, to remove the nail entirely. If only a small\
opening is made in the nail it is apt to be blocked by granulations.\
\
[Illustration: FIG. 9.--Diagram of various forms of Whitlow.\
  a = Purulent blister.\
  b = Suppuration at nail fold.\
  c = Subcutaneous whitlow.\
  d = Whitlow in sheath of flexor tendon (e). ]\
\
_Subcutaneous Whitlow._--In this variety the infection manifests itself\
as a cellulitis of the pulp of the finger (Fig. 9, c), which sometimes\
spreads towards the palm of the hand. The finger becomes red, swollen,\
and tense; there is severe throbbing pain, which is usually worst at\
night and prevents sleep, and the part is extremely tender on pressure.\
When the palm is invaded there may be marked oedema of the back of the\
hand, the dense integument of the palm preventing the swelling from\
appearing on the front. The pus may be under such tension that\
fluctuation cannot be detected. The patient is usually able to flex the\
finger to a certain extent without increasing the pain--a point which\
indicates that the tendon sheaths have not been invaded. The\
suppurative process may, however, spread to the tendon sheaths, or even\
to the bone. Sometimes the excessive tension and virulent toxins induce\
actual gangrene of the distal part, or even of the whole finger. There\
is considerable constitutional disturbance, the temperature often\
reaching 101 o or 102 o F.\
\
The treatment consists in applying a constriction band and making an\
incision over the centre of the most tender area, care being taken to\
avoid opening the tendon sheath lest the infection be conveyed to it.\
Moist dressings should be employed while the suppuration lasts. Carbolic\
fomentations, however, are to be avoided on account of the risk of\
inducing gangrene.\
\
_Whitlow of the Tendon Sheaths._--In this form the main incidence of the\
infection is on the sheaths of the flexor tendons, but it is not always\
possible to determine whether it started there or spread thither from\
the subcutaneous cellular tissue (Fig. 9, d). In some cases both\
connective tissue planes are involved. The affected finger becomes red,\
painful, and swollen, the swelling spreading to the dorsum. The\
involvement of the tendon sheath is usually indicated by the patient\
being unable to flex the finger, and by the pain being increased when he\
attempts to do so. On account of the anatomical arrangement of the\
tendon sheaths, the process may spread into the forearm--directly in the\
case of the thumb and little finger, and after invading the palm in the\
case of the other fingers--and there give rise to a diffuse cellulitis\
which may result in sloughing of fasciae and tendons. When the infection\
spreads into the common flexor sheath under the transverse carpal\
(anterior annular) ligament, it is not uncommon for the intercarpal and\
wrist joints to become implicated. Impaired movement of tendons and\
joints is, therefore, a common sequel to this variety of whitlow.\
\
The _treatment_ consists in inducing passive hyperaemia by Bier's method,\
and, if this is done early, suppuration may be avoided. If pus forms,\
small incisions are made, under local anaesthesia, to relieve the tension\
in the sheath and to diminish the risk of the tendons sloughing. No form\
of drain should be inserted. In the fingers the incisions should be made\
in the middle line, and in the palm they should be made over the\
metacarpal bones to avoid the digital vessels and nerves. If pus has\
spread under the transverse carpal ligament, the incision must be made\
above the wrist. Passive movements and massage must be commenced as\
early as possible and be perseveringly employed to diminish the\
formation of adhesions and resulting stiffness.\
\
_Subperiosteal Whitlow._--This form is usually an extension of the\
subcutaneous or of the thecal variety, but in some cases the\
inflammation begins in the periosteum--usually of the terminal phalanx.\
It may lead to necrosis of a portion or even of the entire phalanx. This\
is usually recognised by the persistence of suppuration long after the\
acute symptoms have passed off, and by feeling bare bone with the probe.\
In such cases one or more of the joints are usually implicated also, and\
lateral mobility and grating may be elicited. Recovery does not take\
place until the dead bone is removed, and the usefulness of the finger\
is often seriously impaired by fibrous or bony ankylosis of the\
interphalangeal joints. This may render amputation advisable when a\
stiff finger is likely to interfere with the patient's occupation.\
\
\
SUPPURATIVE CELLULITIS IN DIFFERENT SITUATIONS\
\
_Cellulitis of the forearm_ is usually a sequel to one of the deeper\
varieties of whitlow.\
\
In the _region of the elbow-joint_, cellulitis is common around the\
olecranon. It may originate as an inflammation of the olecranon bursa,\
or may invade the bursa secondarily. In exceptional cases the\
elbow-joint is also involved.\
\
Cellulitis of the _axilla_ may originate in suppuration in the lymph\
glands, following an infected wound of the hand, or it may spread from a\
septic wound on the chest wall or in the neck. In some cases it is\
impossible to discover the primary seat of infection. A firm, brawny\
swelling forms in the armpit and extends on to the chest wall. It is\
attended with great pain, which is increased on moving the arm, and\
there is marked constitutional disturbance. When suppuration occurs, its\
spread is limited by the attachments of the axillary fascia, and the pus\
tends to burrow on to the chest wall beneath the pectoral muscles, and\
upwards towards the shoulder-joint, which may become infected. When the\
pus forms in the axillary space, the treatment consists in making free\
incisions, which should be placed on the thoracic side of the axilla to\
avoid the axillary vessels and nerves. If the pus spreads on to the\
chest wall, the abscess should be opened below the clavicle by Hilton's\
method, and a counter opening may be made in the axilla.\
\
Cellulitis of the _sole of the foot_ may follow whitlow of the toes.\
\
In the _region of the ankle_ cellulitis is not common; but _around the\
knee_ it frequently occurs in relation to the prepatellar bursa and to\
the popliteal lymph glands, and may endanger the knee-joint. It is also\
met with in the _groin_ following on inflammation and suppuration of the\
inguinal glands, and cases are recorded in which the sloughing process\
has implicated the femoral vessels and led to secondary haemorrhage.\
\
Cellulitis of the scalp, orbit, neck, pelvis, and perineum will be\
considered with the diseases of these regions.\
\
\
CHRONIC SUPPURATION\
\
While it is true that a chronic pyogenic abscess is sometimes met\
with--for example, in the breast and in the marrow of long bones--in the\
great majority of instances the formation of a chronic or cold abscess\
is the result of the action of the tubercle bacillus. It is therefore\
more convenient to study this form of suppuration with tuberculosis\
(p. 139).\
\
\
SINUS AND FISTULA\
\
#Sinus.#--A sinus is a track leading from a focus of suppuration to a\
cutaneous or mucous surface. It usually represents the path by which the\
discharge escapes from an abscess cavity that has been prevented from\
closing completely, either from mechanical causes or from the persistent\
formation of discharge which must find an exit. A sinus is lined by\
granulation tissue, and when it is of long standing the opening may be\
dragged below the level of the surrounding skin by contraction of the\
scar tissue around it. As a sinus will persist until the obstacle to\
closure of the original abscess is removed, it is necessary that this\
should be sought for. It may be a foreign body, such as a piece of dead\
bone, an infected ligature, or a bullet, acting mechanically or by\
keeping up discharge, and if the body is removed the sinus usually\
heals. The presence of a foreign body is often suggested by a mass of\
redundant granulations at the mouth of the sinus. If a sinus passes\
through a muscle, the repeated contractions tend to prevent healing\
until the muscle is kept at rest by a splint, or put out of action by\
division of its fibres. The sinuses associated with empyema are\
prevented from healing by the rigidity of the chest wall, and will only\
close after an operation which admits of the cavity being obliterated.\
In any case it is necessary to disinfect the track, and, it may be, to\
remove the unhealthy granulations lining it, by means of the sharp\
spoon, or to excise it bodily. To encourage healing from the bottom the\
cavity should be packed with bismuth or iodoform gauze. The healing of\
long and tortuous sinuses is often hastened by the injection of Beck's\
bismuth paste (p. 145). If disfigurement is likely to follow from\
cicatricial contraction--for example, in a sinus over the lower jaw\
associated with a carious tooth--the sinus should be excised and the raw\
surfaces approximated with stitches.\
\
The _tuberculous sinus_ is described under Tuberculosis.\
\
A #fistula# is an abnormal canal passing from a mucous surface to the\
skin or to another mucous surface. Fistulae resulting from suppuration\
usually occur near the natural openings of mucous canals--for example,\
on the cheek, as a salivary fistula; beside the inner angle of the eye,\
as a lacrymal fistula; near the ear, as a mastoid fistula; or close to\
the anus, as a fistula-in-ano. Intestinal fistulae are sometimes met with\
in the abdominal wall after strangulated hernia, operations for\
appendicitis, tuberculous peritonitis, and other conditions. In the\
perineum, fistulae frequently complicate stricture of the urethra.\
\
Fistulae also occur between the bladder and vagina (_vesico-vaginal\
fistula_), or between the bladder and the rectum (_recto-vesical\
fistula_).\
\
The _treatment_ of these various forms of fistula will be described in\
the sections dealing with the regions in which they occur.\
\
_Congenital fistulae_, such as occur in the neck from imperfect closure\
of branchial clefts, or in the abdomen from unobliterated foetal ducts\
such as the urachus or Meckel's diverticulum, will be described in their\
proper places.\
\
\
CONSTITUTIONAL MANIFESTATIONS OF PYOGENIC INFECTION\
\
We have here to consider under the terms Sapraemia, Septicaemia, and\
Pyaemia certain general effects of pyogenic infection, which, although\
their clinical manifestations may vary, are all associated with the\
action of the same forms of bacteria. They may occur separately or in\
combination, or one may follow on and merge into another.\
\
#Sapraemia#, or septic intoxication, is the name applied to a form of\
poisoning resulting from the absorption into the blood of the toxic\
products of pyogenic bacteria. These products, which are of the nature\
of alkaloids, act immediately on their entrance into the circulation,\
and produce effects in direct proportion to the amount absorbed. As the\
toxins are gradually eliminated from the body the symptoms abate, and if\
no more are introduced they disappear. Sapraemia in these respects,\
therefore, is comparable to poisoning by any other form of alkaloid,\
such as strychnin or morphin.\
\
_Clinical Features._--The symptoms of sapraemia seldom manifest\
themselves within twenty-four hours of an operation or injury, because\
it takes some time for the bacteria to produce a sufficient dose of\
their poisons. The onset of the condition is marked by a feeling of\
chilliness, sometimes amounting to a rigor, and a rise of temperature to\
102 o, 103 o, or 104 o F., with morning remissions (Fig. 10). The heart's\
action is markedly depressed, and the pulse is soft and compressible.\
The appetite is lost, the tongue dry and covered with a thin\
brownish-red fur, so that it has the appearance of "dried beef." The\
urine is scanty and loaded with urates. In severe cases diarrhoea and\
vomiting of dark coffee-ground material are often prominent features.\
Death is usually impending when the skin becomes cold and clammy, the\
mucous membranes livid, the pulse feeble and fluttering, the discharges\
involuntary, and when a low form of muttering delirium is present.\
\
[Illustration: FIG. 10.--Charts of Acute sapraemia from (a) case of\
crushed foot, and (b) case of incomplete abortion.]\
\
A local form of septic infection is always present--it may be an\
abscess, an infected compound fracture, or an infection of the cavity of\
the uterus, for example, from a retained portion of placenta.\
\
_Treatment._--The first indication is the immediate and complete removal\
of the infected material. The wound must be freely opened, all\
blood-clot, discharge, or necrosed tissue removed, and the area\
disinfected by washing with sterilised salt solution, peroxide of\
hydrogen, or eusol. Stronger lotions are to be avoided as being likely\
to depress the tissues, and so interfere with protective phagocytosis.\
On account of its power of neutralising toxins, iodoform is useful in\
these cases, and is best employed by packing the wound with iodoform\
gauze, and treating it by the open method, if this is possible.\
\
The general treatment is carried out on the same lines as for other\
infective conditions.\
\
#Chronic sapraemia or Hectic Fever.#--Hectic fever differs from acute\
sapraemia merely in degree. It usually occurs in connection with\
tuberculous conditions, such as bone or joint disease, psoas abscess, or\
empyema, which have opened externally, and have thereby become infected\
with pyogenic organisms. It is gradual in its development, and is of a\
mild type throughout.\
\
[Illustration: FIG. 11.--Chart of Hectic Fever.]\
\
The pulse is small, feeble, and compressible, and the temperature rises\
in the afternoon or evening to 102 o or 103 o F. (Fig. 11), the cheeks\
becoming characteristically flushed. In the early morning the\
temperature falls to normal or below it, and the patient breaks into a\
profuse perspiration, which leaves him pale, weak, and exhausted. He\
becomes rapidly and markedly emaciated, even although in some cases the\
appetite remains good and is even voracious.\
\
The poisons circulating in the blood produce _waxy degeneration_ in\
certain viscera, notably the liver, spleen, kidneys, and intestines. The\
process begins in the arterial walls, and spreads thence to the\
connective-tissue structures, causing marked enlargement of the affected\
organs. Albuminuria, ascites, oedema of the lower limbs, clubbing of the\
fingers, and diarrhoea are among the most prominent symptoms of this\
condition.\
\
The _prognosis_ in hectic fever depends on the completeness with which\
the further absorption of toxins can be prevented. In many cases this\
can only be effected by an operation which provides for free drainage,\
and, if possible, the removal of infected tissues. The resulting wound\
is best treated by the open method. Even advanced waxy degeneration does\
not contra-indicate this line of treatment, as the diseased organs\
usually recover if the focus from which absorption of toxic material is\
taking place is completely eradicated.\
\
[Illustration: FIG. 12.--Chart of case of Septicaemia followed by\
Pyaemia.]\
\
#Septicaemia.#--This form of blood-poisoning is the result of the action\
of pyogenic bacteria, which not only produce their toxins at the primary\
seat of infection, but themselves enter the blood-stream and are carried\
to other parts, where they settle and produce further effects.\
\
_Clinical Features._--There may be an incubation period of some hours\
between the infection and the first manifestation of acute septicaemia.\
In such conditions as acute osteomyelitis or acute peritonitis, we see\
the most typical clinical pictures of this condition. The onset is\
marked by a chill, or a rigor, which may be repeated, while the\
temperature rises to 103 o or 104 o F., although in very severe cases the\
temperature may remain subnormal throughout, the virulence of the toxins\
preventing reaction. It is in the general appearance of the patient and\
in the condition of the pulse that we have our best guides as to the\
severity of the condition. If the pulse remains firm, full, and regular,\
and does not exceed 110 or even 120, while the temperature is moderately\
raised, the outlook is hopeful; but when the pulse becomes small and\
compressible, and reaches 130 or more, especially if at the same time\
the temperature is low, a grave prognosis is indicated. The tongue is\
often dry and coated with a black crust down the centre, while the sides\
are red. It is a good omen when the tongue becomes moist again. Thirst\
is most distressing, especially in septicaemia of intestinal origin.\
Persistent vomiting of dark-brown material is often present, and\
diarrhoea with blood-stained stools is not uncommon. The urine is small\
in amount, and contains a large proportion of urates. As the poisons\
accumulate, the respiration becomes shallow and laboured, the face of a\
dull ashy grey, the nose pinched, and the skin cold and clammy.\
Capillary haemorrhages sometimes take place in the skin or mucous\
membranes; and in a certain proportion of cases cutaneous eruptions\
simulating those of scarlet fever or measles appear, and are apt to lead\
to errors in diagnosis. In other cases there is slight jaundice. The\
mental state is often one of complete apathy, the patient failing to\
realise the gravity of his condition; sometimes there is delirium.\
\
The _prognosis_ is always grave, and depends on the possibility of\
completely eradicating the focus of infection, and on the reserve force\
the patient has to carry him over the period during which he is\
eliminating the poison already circulating in his blood.\
\
The _treatment_ is carried out on the same lines as in sapraemia, but it\
is less likely to be successful owing to the organisms having entered\
the circulation. When possible, the primary focus of infection should be\
dealt with.\
\
#Pyaemia# is a form of blood-poisoning characterised by the development\
of secondary foci of suppuration in different parts of the body. Toxins\
are thus introduced into the blood, not only at the primary seat of\
infection, but also from each of these metastatic collections. Like\
septicaemia, this condition is due to pyogenic bacteria, the\
_streptococcus pyogenes_ being the commonest organism found. The primary\
infection is usually in a wound--for example, a compound fracture--but\
cases occur in which the point of entrance of the bacteria is not\
discoverable. The dissemination of the organisms takes place through the\
medium of infected emboli which form in a thrombosed vein in the\
vicinity of the original lesion, and, breaking loose, are carried\
thence in the blood-stream. These emboli lodge in the minute vessels of\
the lungs, spleen, liver, kidneys, pleura, brain, synovial membranes, or\
cellular tissue, and the bacteria they contain give rise to secondary\
foci of suppuration. Secondary abscesses are thus formed in those parts,\
and these in turn may be the starting-point of new emboli which give\
rise to fresh areas of pus formation. The organs above named are the\
commonest situations of pyaemic abscesses, but these may also occur in\
the bone marrow, the substance of muscles, the heart and pericardium,\
lymph glands, subcutaneous tissue, or, in fact, in any tissue of the\
body. Organisms circulating in the blood are prone to lodge on the\
valves of the heart and give rise to endocarditis.\
\
[Illustration: FIG. 13.--Chart of Pyaemia following on Acute\
Osteomyelitis.]\
\
_Clinical Features._--Before antiseptic surgery was practised, pyaemia\
was a common complication of wounds. In the present day it is not only\
infinitely less common, but appears also to be of a less severe type.\
Its rarity and its mildness may be related as cause and effect, because\
it was formerly found that pyaemia contracted from a pyaemic patient was\
more virulent than that from other sources.\
\
In contrast with sapraemia and septicaemia, pyaemia is late of developing,\
and it seldom begins within a week of the primary infection. The first\
sign is a feeling of chilliness, or a violent rigor lasting for perhaps\
half an hour, during which time the temperature rises to 103 o, 104 o, or\
105 o F. In the course of an hour it begins to fall again, and the\
patient breaks into a profuse sweat. The temperature may fall several\
degrees, but seldom reaches the normal. In a few days there is a second\
rigor with rise of temperature, and another remission, and such attacks\
may be repeated at diminishing intervals during the course of the\
illness (Figs. 12 and 13). The pulse is soft, and tends to remain\
abnormally rapid even when the temperature falls nearly to normal.\
\
The face is flushed, and wears a drawn, anxious expression, and the eyes\
are bright. A characteristic sweetish odour, which has been compared to\
that of new-mown hay, can be detected in the breath and may pervade the\
patient. The appetite is lost; there may be sickness and vomiting and\
profuse diarrhoea; and the patient emaciates rapidly. The skin is\
continuously hot, and has often a peculiar pungent feel. Patches of\
erythema sometimes appear scattered over the body. The skin may assume a\
dull sallow or earthy hue, or a bright yellow icteric tint may appear.\
The conjunctivae also may be yellow. In the latter stages of the disease\
the pulse becomes small and fluttering; the tongue becomes dry and\
brown; sordes collect on the teeth; and a low muttering form of delirium\
supervenes.\
\
Secondary infection of the parotid gland frequently occurs, and gives\
rise to a suppurative parotitis. This condition is associated with\
severe pain, gradually extending from behind the angle of the jaw on to\
the face. There is also swelling over the gland, and eventually\
suppuration and sloughing of the gland tissue and overlying skin.\
\
Secondary abscesses in the lymph glands, subcutaneous tissue, or joints\
are often so insidious and painless in their development that they are\
only discovered accidentally. When the abscess is evacuated, healing\
often takes place with remarkable rapidity, and with little impairment\
of function.\
\
The general symptoms may be simulated by an attack of malaria.\
\
_Prognosis._--The prognosis in acute pyaemia is much less hopeless than\
it once was, a considerable proportion of the patients recovering. In\
acute cases the disease proves fatal in ten days or a fortnight, death\
being due to toxaemia. Chronic cases often run a long course, lasting for\
weeks or even months, and prove fatal from exhaustion and waxy disease\
following on prolonged suppuration.\
\
_Treatment._--In such conditions as compound fractures and severe\
lacerated wounds, much can be done to avert the conditions which lead to\
pyaemia, by applying a Bier's constricting bandage as soon as there is\
evidence of infection having taken place, or even if there is reason to\
suspect that the wound is not aseptic.\
\
If sepsis is already established, and evidence of general infection is\
present, the wound should be opened up sufficiently to admit of thorough\
disinfection and drainage, and the constricting bandage applied to aid\
the defensive processes going on in the tissues. If these measures fail,\
amputation of the limb may be the only means of preventing further\
dissemination of infective material from the primary source of\
infection.\
\
Attempts have been made to interrupt the channel along which the\
infective emboli spread, by ligating or resecting the main vein of the\
affected part, but this is seldom feasible except in the case of the\
internal jugular vein for infection of the transverse sinus.\
\
Secondary abscesses must be aspirated or opened and drained whenever\
possible.\
\
The general treatment is conducted on the same lines as on other forms\
of pyogenic infection.\
\
\
\
\
CHAPTER V\
\
ULCERATION AND ULCERS\
\
\
Definitions--Clinical examination of an ulcer--The healing\
    sore.--Classification of ulcers--A. According to cause:\
    _Traumatism_, _Imperfect circulation_, _Imperfect nerve-supply_,\
    _Constitutional causes_--B. According to condition: _Healing_,\
    _Stationary_, _Spreading_.--Treatment.\
\
The process of _ulceration_ may be defined as the molecular or cellular\
death of tissue taking place on a free surface. It is essentially of the\
same nature as the process of suppuration, only that the purulent\
discharge, instead of collecting in a closed cavity and forming an\
abscess, at once escapes on the surface.\
\
An _ulcer_ is an open wound or sore in which there are present certain\
conditions tending to prevent it undergoing the natural process of\
repair. Of these, one of the most important is the presence of\
pathogenic bacteria, which by their action not only prevent healing, but\
so irritate and destroy the tissues as to lead to an actual increase in\
the size of the sore. Interference with the nutrition of a part by oedema\
or chronic venous congestion may impede healing; as may also induration\
of the surrounding area, by preventing the contraction which is such an\
important factor in repair. Defective innervation, such as occurs in\
injuries and diseases of the spinal cord, also plays an important part\
in delaying repair. In certain constitutional conditions, too--for\
example, Bright's disease, diabetes, or syphilis--the vitiated state of\
the tissues is an impediment to repair. Mechanical causes, such as\
unsuitable dressings or ill-fitting appliances, may also act in the same\
direction.\
\
#Clinical Examination of an Ulcer.#--In examining any ulcer, we\
observe--(1) Its _base_ or _floor_, noting the presence or absence of\
granulations, their disposition, size, colour, vascularity, and whether\
they are depressed or elevated in relation to the surrounding parts. (2)\
The _discharge_ as to quantity, consistence, colour, composition, and\
odour. (3) The _edges_, noting particularly whether or not the marginal\
epithelium is attempting to grow over the surface; also their shape,\
regularity, thickness, and whether undermined or overlapping, everted or\
depressed. (4) The _surrounding tissues_, as to whether they are\
congested, oedematous, inflamed, indurated, or otherwise. (5) Whether or\
not there is _pain_ or tenderness in the raw surface or its\
surroundings. (6) The _part of the body_ on which it occurs, because\
certain ulcers have special seats of election--for example, the varicose\
ulcer in the lower third of the leg, the perforating ulcer on the sole\
of the foot, and so on.\
\
#The Healing Sore.#--If a portion of skin be excised aseptically, and no\
attempt made to close the wound, the raw surface left is soon covered\
over with a layer of coagulated blood and lymph. In the course of a few\
days this is replaced by the growth of _granulations_, which are of\
uniform size, of a pinkish-red colour, and moist with a slight serous\
exudate containing a few dead leucocytes. They grow until they reach the\
level of the surrounding skin, and so fill the gap with a fine velvety\
mass of granulation tissue. At the edges, the young epithelium may be\
seen spreading in over the granulations as a fine bluish-white pellicle,\
which gradually covers the sore, becoming paler in colour as it\
thickens, and eventually forming the smooth, non-vascular covering of\
the cicatrix. There is no pain, and the surrounding parts are healthy.\
\
This may be used as a type with which to compare the ulcers seen at the\
bedside, so that we may determine how far, and in what particulars,\
these differ from the type; and that we may in addition recognise the\
conditions that have to be counteracted before the characters of the\
typical healing sore are assumed.\
\
For purposes of contrast we may indicate the characters of an open sore\
in which bacterial infection with pathogenic bacteria has taken place.\
The layer of coagulated blood and lymph becomes liquefied and is thrown\
off, and instead of granulations being formed, the tissues exposed on\
the floor of the ulcer are destroyed by the bacterial toxins, with the\
formation of minute sloughs and a quantity of pus.\
\
The discharge is profuse, thin, acrid, and offensive, and consists of\
pus, broken-down blood-clot, and sloughs. The edges are inflamed,\
irregular, and ragged, showing no sign of growing epithelium--on the\
contrary, the sore may be actually increasing in area by the\
breaking-down of the tissues at its margins. The surrounding parts are\
hot, red, swollen, and oedematous; and there is pain and tenderness both\
in the sore itself and in the parts around.\
\
#Classification of Ulcers.#--The nomenclature of ulcers is much involved\
and gives rise to great confusion, chiefly for the reason that no one\
basis of classification has been adopted. Thus some ulcers are named\
according to the causes at work in producing or maintaining them--for\
example, the traumatic, the septic, and the varicose ulcer; some from\
the constitutional element present, as the gouty and the diabetic ulcer;\
and others according to the condition in which they happen to be when\
seen by the surgeon, such as the weak, the inflamed, and the callous\
ulcer.\
\
So long as we retain these names it will be impossible to find a single\
basis for classification; and yet many of the terms are so descriptive\
and so generally understood that it is undesirable to abolish them. We\
must therefore remain content with a clinical arrangement of ulcers,--it\
cannot be called a classification,--considering any given ulcer from two\
points of view: first its _cause_, and second its _present condition_.\
This method of studying ulcers has the practical advantage that it\
furnishes us with the main indications for treatment as well as for\
diagnosis: the cause must be removed, and the condition so modified as\
to convert the ulcer into an aseptic healing sore.\
\
A. #Arrangement of Ulcers according to their Cause.#--Although any given\
ulcer may be due to a combination of causes, it is convenient to\
describe the following groups:\
\
_Ulcers due to Traumatism._--Traumatism in the form of a _crush_ or\
_bruise_ is a frequent cause of ulcer formation, acting either by\
directly destroying the skin, or by so diminishing its vitality that it\
is rendered a suitable soil for bacteria. If these gain access, in the\
course of a few days the damaged area of skin becomes of a greyish\
colour, blebs form on it, and it undergoes necrosis, leaving an\
unhealthy raw surface when the slough separates.\
\
_Heat_ and _prolonged exposure to the Rontgen rays_ or _to radium\
emanations_ act in a similar way.\
\
The _pressure_ of improperly padded splints or other appliances may so\
far interfere with the circulation of the part pressed upon, that the\
skin sloughs, leaving an open sore. This is most liable to occur in\
patients who suffer from some nerve lesion--such as anterior\
poliomyelitis, or injury of the spinal cord or nerve-trunks.\
Splint-pressure sores are usually situated over bony prominences, such\
as the malleoli, the condyles of the femur or humerus, the head of the\
fibula, the dorsum of the foot, or the base of the fifth metatarsal\
bone. On removing the splint, the skin of the part pressed upon is found\
to be of a red or pink colour, with a pale grey patch in the centre,\
which eventually sloughs and leaves an ulcer. Certain forms of\
_bed-sore_ are also due to prolonged pressure.\
\
Pressure sores are also known to have been produced artificially by\
malingerers and hysterical subjects.\
\
[Illustration: FIG. 14.--Leg Ulcers associated with Varicose Veins and\
Pigmentation of the Skin.]\
\
_Ulcers due to Imperfect Circulation._--Imperfect circulation is an\
important causative factor in ulceration, especially when it is the\
_venous return_ that is defective. This is best illustrated in the\
so-called _leg ulcer_, which occurs most frequently on the front and\
medial aspect of the lower third of the leg. At this point the\
anastomosis between the superficial and deep veins of the leg is less\
free than elsewhere, so that the extra stress thrown upon the surface\
veins interferes with the nutrition of the skin (Hilton). The importance\
of imperfect venous return in the causation of such ulcers is evidenced\
by the fact that as soon as the condition of the circulation is improved\
by confining the patient to bed and elevating the limb, the ulcer begins\
to heal, even although all methods of local treatment have hitherto\
proved ineffectual. In a considerable number of cases, but by no means\
in all, this form of ulcer is associated with the presence of varicose\
veins, and in such cases it is spoken of as the _varicose ulcer_ (Fig. 14).\
The presence of varicose veins is frequently associated with a\
diffuse brownish or bluish pigmentation of the skin of the lower third\
of the leg, or with an obstinate form of dermatitis (_varicose eczema_),\
and the scratching or rubbing of the part is liable to cause a breach of\
the surface and permit of infection which leads to ulceration. Varicose\
ulcers may also originate from the bursting of a small peri-phlebitic\
abscess.\
\
Varicose veins in immediate relation to the base of a large chronic\
ulcer usually become thrombosed, and in time are reduced to fibrous\
cords, and therefore in such cases haemorrhage is not a common\
complication. In smaller and more superficial ulcers, however, the\
destructive process is liable to implicate the wall of the vessel before\
the occurrence of thrombosis, and to lead to profuse and it may be\
dangerous bleeding.\
\
These ulcers are at first small and superficial, but from want of care,\
from continued standing or walking, or from injudicious treatment, they\
gradually become larger and deeper. They are not infrequently multiple,\
and this, together with their depth, may lead to their being mistaken\
for ulcers due to syphilis. The base of the ulcer is covered with\
imperfectly formed, soft, oedematous granulations, which give off a thin\
sero-purulent discharge. The edges are slightly inflamed, and show no\
evidence of healing. The parts around are usually pigmented and slightly\
oedematous, and as a rule there is little pain. This variety of ulcer is\
particularly prone to pass into the condition known as callous.\
\
In _anaemic_ patients, especially young girls, ulcers are occasionally\
met with which have many of the clinical characters of those associated\
with imperfect venous return. They are slow to heal, and tend to pass\
into the condition known as weak.\
\
_Ulcers due to Interference with Nerve-Supply._--Any interference with\
the nerve-supply of the superficial tissues predisposes to ulceration.\
For example, _trophic_ ulcers are liable to occur in injuries or\
diseases of the spinal cord, in cerebral paralysis, in limbs weakened by\
poliomyelitis, in ascending or peripheral neuritis, or after injuries of\
nerve-trunks.\
\
The _acute bed-sore_ is a rapidly progressing form of ulceration, often\
amounting to gangrene, of portions of skin exposed to pressure when\
their trophic nerve-supply has been interfered with.\
\
[Illustration: FIG. 15.--Perforating Ulcers of Sole of Foot.\
\
(From Photograph lent by Sir Montagu Cotterill.)]\
\
The _perforating ulcer of the foot_ is a peculiar type of sore which\
occurs in association with the different forms of peripheral neuritis,\
and with various lesions of the brain and spinal cord, such as general\
paralysis, locomotor ataxia, or syringo-myelia (Fig. 15). It also occurs\
in patients suffering from glycosuria, and is usually associated with\
arterio-sclerosis--local or general. Perforating ulcer is met with most\
frequently under the head of the metatarsal bone of the great toe. A\
callosity forms and suppuration occurs under it, the pus escaping\
through a small hole in the centre. The process slowly and gradually\
spreads deeper and deeper, till eventually the bone or joint is reached,\
and becomes implicated in the destructive process--hence the term\
"perforating ulcer." The flexor tendons are sometimes destroyed, the toe\
being dorsiflexed by the unopposed extensors. The depth of the track\
being so disproportionate to its superficial area, the condition closely\
simulates a tuberculous sinus, for which it is liable to be mistaken.\
The raw surface is absolutely insensitive, so that the probe can be\
freely employed without the patient even being aware of it or suffering\
the least discomfort--a significant fact in diagnosis. The cavity is\
filled with effete and decomposing epidermis, which has a most offensive\
odour. The chronic and intractable character of the ulcer is due to\
interference with the trophic nerve-supply of the parts, and to the fact\
that the epithelium of the skin grows in and lines the track leading\
down to the deepest part of the ulcer and so prevents closure. While\
they are commonest on the sole of the foot and other parts subjected to\
pressure, perforating ulcers are met with on the sides and dorsum of the\
foot and toes, on the hands, and on other parts where no pressure has\
been exerted.\
\
The _tuberculous ulcer_, so often seen in the neck, in the vicinity of\
joints, or over the ribs and sternum, usually results from the bursting\
through the skin of a tuberculous abscess. The base is soft, pale, and\
covered with feeble granulations and grey shreddy sloughs. The edges are\
of a dull blue or purple colour, and gradually thin out towards their\
free margins, and in addition are characteristically undermined, so that\
a probe can be passed for some distance between the floor of the ulcer\
and the thinned-out edges. Thin, devitalised tags of skin often stretch\
from side to side of the ulcer. The outline is irregular; small\
perforations often occur through the skin, and a thin, watery discharge,\
containing grey shreds of tuberculous debris, escapes.\
\
_Bazin's Disease._--This term is applied to an affection of the skin and\
subcutaneous tissue which bears certain resemblances to tuberculosis. It\
is met with almost exclusively between the knee and the ankle, and it\
usually affects both legs. It is commonest in girls of delicate\
constitution, in whose family history there is evidence of a tuberculous\
taint. The patient often presents other lesions of a tuberculous\
character, notably enlarged cervical glands, and phlyctenular\
ophthalmia. The tubercle bacillus has rarely been found, but we have\
always observed characteristic epithelioid cells and giant cells in\
sections made from the edge or floor of the ulcer.\
\
[Illustration: FIG. 16.--Bazin's Disease in a girl aet. 16.]\
\
The condition begins by the formation in the skin and subcutaneous\
tissue of dusky or livid nodules of induration, which soften and\
ulcerate, forming small open sores with ragged and undermined edges, not\
unlike those resulting from the breaking down of superficial syphilitic\
gummata (Fig. 16). Fresh crops of nodules appear in the neighbourhood of\
the ulcers, and in turn break down. While in the nodular stage the\
affection is sometimes painful, but with the formation of the ulcer the\
pain subsides.\
\
The disease runs a chronic course, and may slowly extend over a wide\
area in spite of the usual methods of treatment. After lasting for some\
months, or even years, however, it may eventually undergo spontaneous\
cure. The most satisfactory treatment is to excise the affected tissues\
and fill the gap with skin-grafts.\
\
[Illustration: FIG. 17.--Syphilitic Ulcers in region of Knee, showing\
punched-out appearance and raised indurated edges.]\
\
The _syphilitic ulcer_ is usually formed by the breaking down of a\
cutaneous or subcutaneous gumma in the tertiary stage of syphilis. When\
the gummatous tissue is first exposed by the destruction of the skin or\
mucous membrane covering it, it appears as a tough greyish slough,\
compared to "wash leather," which slowly separates and leaves a more or\
less circular, deep, punched-out gap which shows a few feeble unhealthy\
granulations and small sloughs on its floor. The edges are raised and\
indurated; and the discharge is thick, glairy, and peculiarly offensive.\
The parts around the ulcer are congested and of a dark brown colour.\
There are usually several such ulcers together, and as they tend to heal\
at one part while they spread at another, the affected area assumes a\
sinuous or serpiginous outline. Syphilitic ulcers may be met with in any\
part of the body, but are most frequent in the upper part of the leg\
(Fig. 17), especially around the knee-joint in women, and over the ribs\
and sternum. On healing, they usually leave a depressed and adherent\
cicatrix.\
\
The _scorbutic ulcer_ occurs in patients suffering from scurvy, and is\
characterised by its prominent granulations, which show a marked\
tendency to bleed, with the formation of clots, which dry and form a\
spongy crust on the surface.\
\
In _gouty_ patients small ulcers which are exceedingly irritable and\
painful are liable to occur.\
\
_Ulcers associated with Malignant Disease._--Cancer and sarcoma when\
situated in the subcutaneous tissue may destroy the overlying skin so\
that the substance of the tumour is exposed. The fungating masses thus\
produced are sometimes spoken of as malignant ulcers, but as they are\
essentially different in their nature from all other forms of ulcers,\
and call for totally different treatment, it is best to consider them\
along with the tumours with which they are associated. Rodent ulcer,\
which is one form of cancer of the skin, will be discussed with new\
growths of the skin.\
\
B. #Arrangement of Ulcers according to their Condition.#--Having arrived\
at an opinion as to the cause of a given ulcer, and placed it in one or\
other of the preceding groups, the next question to ask is, In what\
condition do I find this ulcer at the present moment?\
\
Any ulcer is in one of three states--healing, stationary, or spreading;\
although it is not uncommon to find healing going on at one part while\
the destructive process is extending at another.\
\
_The Healing Condition._--The process of healing in an ulcer has already\
been studied, and we have learned that it takes place by the formation\
of granulation tissue, which becomes converted into connective tissue,\
and is covered over by epithelium growing in from the edges.\
\
Those ulcers which are _stationary_--that is, neither healing nor\
spreading--may be in one of several conditions.\
\
_The Weak Condition._--Any ulcer may get into a weak state from\
receiving a blood supply which is defective either in quantity or in\
quality. The granulations are small and smooth, and of a pale yellow or\
grey colour, the discharge is small in amount, and consists of thin\
serum and a few pus cells, and as this dries on the edges it forms scabs\
which interfere with the growth of epithelium.\
\
Should the part become oedematous, either from general causes, such as\
heart or kidney disease, or from local causes, such as varicose veins,\
the granulations share in the oedema, and there is an abundant serous\
discharge.\
\
The excessive use of moist dressings leads to a third variety of weak\
ulcer--namely, one in which the granulations become large, soft, pale,\
and flabby, projecting beyond the level of the skin and overlapping the\
edges, which become pale and sodden. The term "proud flesh" is popularly\
applied to such redundant granulations.\
\
[Illustration: FIG. 18.--Callous Ulcer, showing thickened edges and\
indurated swelling of surrounding parts.]\
\
_The Callous Condition._--This condition is usually met with in ulcers\
on the lower third of the leg, and is often associated with the presence\
of varicose veins. It is chiefly met with in hospital practice. The want\
of healing is mainly due to impeded venous return and to oedema and\
induration of the surrounding skin and cellular tissues (Fig. 18). The\
induration results from coagulation and partial organisation of the\
inflammatory effusion, and prevents the necessary contraction of the\
sore. The base of a callous ulcer lies at some distance below the level\
of the swollen, thickened, and white edges, and presents a glazed\
appearance, such granulations as are present being unhealthy and\
irregular. The discharge is usually watery, and cakes in the dressing.\
When from neglect and want of cleanliness the ulcer becomes inflamed,\
there is considerable pain, and the discharge is purulent and often\
offensive.\
\
The prolonged hyperaemia of the tissues in relation to a callous ulcer of\
the leg often leads to changes in the underlying bones. The periosteum\
is abnormally thick and vascular, the superficial layers of the bone\
become injected and porous, and the bones, as a whole, are thickened. In\
the macerated bone "the surface is covered with irregular,\
stalactite-like processes or foliaceous masses, which, to a certain\
extent, follow the line of attachment of the interosseous membrane and\
of the intermuscular septa" (Cathcart) (Fig. 19). When the whole\
thickness of the soft tissues is destroyed by the ulcerative process,\
the area of bone that comes to form the base of the ulcer projects as a\
flat, porous node, which in its turn may be eroded. These changes as\
seen in the macerated specimen are often mistaken for disease\
originating in the bone.\
\
[Illustration: FIG. 19.--Tibia and Fibula, showing changes due to\
chronic ulcer of leg.]\
\
The _irritable condition_ is met with in ulcers which occur, as a rule,\
just above the external malleolus in women of neurotic temperament. They\
are small in size and have prominent granulations, and by the aid of a\
probe points of excessive tenderness may be discovered. These, Hilton\
believed, correspond to exposed nerve filaments.\
\
_Ulcers which are spreading_ may be met with in one of several\
conditions.\
\
_The Inflamed Condition._--Any ulcer may become acutely inflamed from\
the access of fresh organisms, aided by mechanical irritation from\
trauma, ill-fitting splints or bandages, or want of rest, or from\
chemical irritants, such as strong antiseptics. The best clinical\
example of an inflamed ulcer is the venereal soft sore. The base of the\
ulcer becomes red and angry-looking, the granulations disappear, and a\
copious discharge of thin yellow pus, mixed with blood, escapes. Sloughs\
of granulation tissue or of connective tissue may form. The edges become\
red, ragged, and everted, and the ulcer increases in size by spreading\
into the inflamed and oedematous surrounding tissues. Such ulcers are\
frequently multiple. Pain is a constant symptom, and is often severe,\
and there is usually some constitutional disturbance.\
\
The _phagedaenic condition_ is the result of an ulcer being infected with\
specially virulent bacteria. It occurs in syphilitic ulcers, and rapidly\
leads to a widespread destruction of tissue. It is also met with in the\
throat in some cases of scarlet fever, and may give rise to fatal\
haemorrhage by ulcerating into large blood vessels. All the local and\
constitutional signs of a severe septic infection are present.\
\
#Treatment of Ulcers.#--An ulcer is not only an immediate cause of\
suffering to the patient, crippling and incapacitating him for his work,\
but is a distinct and constant menace to his health: the prolonged\
discharge reduces his strength; the open sore is a possible source of\
infection by the organisms of suppuration, erysipelas, or other specific\
diseases; phlebitis, with formation of septic emboli, leading to pyaemia,\
is liable to occur; and in old persons it is not uncommon for ulcers of\
long standing to become the seat of cancer. In addition, the offensive\
odour of many ulcers renders the patient a source of annoyance and\
discomfort to others. The primary object of treatment in any ulcer is to\
bring it into the condition of a healing sore. When this has been\
effected, nature will do the rest, provided extraneous sources of\
irritation are excluded.\
\
Steps must be taken to facilitate the venous return from the ulcerated\
part, and to ensure that a sufficient supply of fresh, healthy blood\
reaches it. The septic element must be eliminated by disinfecting the\
ulcer and its surroundings, and any other sources of irritation must be\
removed.\
\
If the patient's health is below par, good nourishing food, tonics, and\
general hygienic treatment are indicated.\
\
_Management of a Healing Sore._--Perhaps the best dressing for a healing\
sore is a layer of Lister's perforated oiled-silk protective, which is\
made to cover the raw surface and the skin for about a quarter of an\
inch beyond the margins of the sore. Over this three or four thicknesses\
of sterilised gauze, wrung out of eusol, creolin, or sterilised water,\
are applied, and covered by a pad of absorbent wool. As far as possible\
the part should be kept at rest, and the position should be adjusted so\
as to favour the circulation in the affected area.\
\
The dressing may be renewed at intervals, and care must be taken to\
avoid any rough handling of the sore. Any discharge that lies on the\
surface should be removed by a gentle stream of lotion rather than by\
wiping. The area round the sore should be cleansed before the fresh\
dressing is applied.\
\
In some cases, healing goes on more rapidly under a dressing of weak\
boracic ointment (one-quarter the strength of the pharmacopoeial\
preparation). The growth of epithelium may be stimulated by a 6 to 8 per\
cent. ointment of scarlet-red.\
\
Dusting powders and poultice dressings are best avoided in the treatment\
of healing sores.\
\
In extensive ulcers resulting from recent burns, if the granulations are\
healthy and aseptic, skin-grafts may safely be placed on them directly.\
If, however, their asepticity cannot be relied upon, it is necessary to\
scrape away the superficial layer of the granulations, the young fibrous\
tissue underneath being conserved, as it is sufficiently vascular to\
nourish the grafts placed on it.\
\
#Treatment of Special Varieties of Ulcers.#--Before beginning to treat a\
given ulcer, two questions have to be answered--first, What are the\
causative conditions present? and second, In what condition do I find\
the ulcer?--in other words, In what particulars does it differ from a\
healthy healing sore?\
\
If the cause is a local one, it must be removed; if a constitutional\
one, means must be taken to counteract it. This done, the condition of\
the ulcer must be so modified as to bring it into the state of a healing\
sore, after which it will be managed on the lines already laid down.\
\
#Treatment in relation to the Cause of the Ulcer.#--_Traumatic\
Group._--The _prophylaxis_ of these ulcers consists in excluding\
bacteria, by cleansing crushed or bruised parts, and applying sterilised\
dressings and properly adjusted splints. If there is reason to fear that\
the disinfection has not been complete, a Bier's constricting bandage\
should be applied for some hours each day. These measures will often\
prevent a grossly injured portion of skin dying, and will ensure\
asepticity should it do so. In the event of the skin giving way, the\
same form of dressing should be continued till the slough has separated\
and a healthy granulating surface is formed. The protective dressing\
appropriate to a healing sore is then substituted. _Pressure sores_ are\
treated on the same lines.\
\
The treatment of ulcers caused by _burns and scalds_ will be described\
later.\
\
In _ulcers of the leg due to interference with the venous return_, the\
primary indication is to elevate the limb in order to facilitate the\
flow of the blood in the veins, and so admit of fresh blood reaching the\
part. The limb may be placed on pillows, or the foot of the bed raised\
on blocks, so that the ulcer lies on a higher level than the heart.\
Should varicose veins be present, the question of operative treatment\
must be considered.\
\
When an _imperfect nerve supply_ is the main factor underlying ulcer\
formation, prophylaxis is the chief consideration. In patients suffering\
from spinal injuries or diseases, cerebral paralysis, or affections of\
the peripheral nerves, all sources of irritation, such as ill-fitting\
splints, tight bandages, moist applications, and hot bottles, should be\
avoided. Any part liable to pressure, from the position of the patient\
or otherwise, must be carefully protected by pads of wool, air-cushions,\
or water-bags, and must be kept absolutely dry. The skin should be\
hardened by daily applications of methylated spirit.\
\
Should an ulcer form in spite of these precautions, the mildest\
antiseptics must be employed for bathing and dressing it, and as far as\
possible all dressings should be dry.\
\
The _perforating ulcer_ of the foot calls for special treatment. To\
avoid pressure on the sole of the foot, the patient must be confined to\
bed. As the main local obstacle to healing is the down-growth of\
epithelium along the sides of the ulcer, this must be removed by the\
knife or sharp spoon. The base also should be excised, and any bone\
which may have become involved should be gouged away, so as to leave a\
healthy and vascular surface. The cavity thus formed is stuffed with\
bismuth or iodoform gauze and encouraged to heal from the bottom. As the\
parts are insensitive an anaesthetic is not required. After the ulcer has\
healed, the patient should wear in his boot a thick felt sole with a\
hole cut out opposite the situation of the cicatrix. When a joint has\
been opened into, the difficulty of thoroughly getting rid of all\
unhealthy and infected granulations is so great that amputation may be\
advisable, but it is to be remembered that ulceration may recur in the\
stump if pressure is put upon it. The treatment of any nervous disease\
or glycosuria which may coexist is, of course, indicated.\
\
Exposure of the plantar nerves by an incision behind the medial\
malleolus, and subjecting them to forcible stretching, has been employed\
by Chipault and others in the treatment of perforating ulcers of the\
foot.\
\
The ulcer that forms in relation to callosities on the sole of the foot\
is treated by paring away all the thickened skin, after softening it\
with soda fomentations, removing the unhealthy granulations, and\
applying stimulating dressings.\
\
_Treatment of Ulcers due to Constitutional Causes._--When ulcers are\
associated with such diseases as tuberculosis, syphilis, diabetes,\
Bright's disease, scurvy, or gout, these must receive appropriate\
treatment.\
\
The local treatment of the _tuberculous ulcer_ calls for special\
mention. If the ulcer is of limited extent and situated on an exposed\
part of the body, the most satisfactory method is complete removal, by\
means of the knife, scissors, or sharp spoon, of the ulcerated surface\
and of all the infected area around it, so as to leave a healthy surface\
from which granulations may spring up. Should the raw surface left be\
likely to result in an unsightly scar or in cicatricial contraction,\
skin-grafting should be employed.\
\
For extensive ulcers on the limbs, the chest wall, or on other covered\
parts, or when operative treatment is contra-indicated, the use of\
tuberculin and exposure to the Rontgen rays have proved beneficial. The\
induction of passive hyperaemia, by Bier's or by Klapp's apparatus,\
should also be used, either alone or supplementary to other measures.\
\
No ulcerative process responds so readily to medicinal treatment as the\
_syphilitic ulcer_ does to the intra-venous administration of arsenical\
preparations of the "606" or "914" groups or to full doses of iodide of\
potassium and mercury, and the local application of black wash. When the\
ulceration has lasted for a long time, however, and is widespread and\
deep, the duration of treatment is materially shortened by a thorough\
scraping with the sharp spoon.\
\
#Treatment in relation to the Condition of the Ulcer.#--_Ulcers in a\
weak condition._--If the weak condition of the ulcer is due to anaemia\
or kidney disease, these affections must first be treated. Locally, the\
imperfect granulations should be scraped away, and some stimulating\
agent applied to the raw surface to promote the growth of healthy\
granulations. For this purpose the sore may be covered with gauze\
smeared with a 6 to 8 per cent. ointment of scarlet-red, the surrounding\
parts being protected from the irritant action of the scarlet-red by a\
layer of vaseline. A dressing of gauze moistened with eusol or of\
boracic lint wrung out of red lotion (2 grains of sulphate of zinc, and\
10 minims of compound tincture of lavender, to an ounce of water), and\
covered with a layer of gutta-percha tissue, is also useful.\
\
When the condition has resulted from the prolonged use of moist\
dressings, these must be stopped, the redundant granulations clipped\
away with scissors, the surface rubbed with silver nitrate or sulphate\
of copper (blue-stone), and dry dressings applied.\
\
When the ulcer has assumed the characters of a healing sore, skin-grafts\
may be applied to hasten cicatrisation.\
\
_Ulcers in a callous condition_ call for treatment in three\
directions--(1) The infective element must be eliminated. When the ulcer\
is foul, relays of charcoal poultices (three parts of linseed meal to\
one of charcoal), maintained for thirty-six to forty-eight hours, are\
useful as a preliminary step. The base of the ulcer and the thickened\
edges should then be freely scraped with a sharp spoon, and the\
resulting raw surface sponged over with undiluted carbolic acid or\
iodine, after which an antiseptic dressing is applied, and changed daily\
till healthy granulations appear. (2) The venous return must be\
facilitated by elevation of the limb and massage. (3) The induration of\
the surrounding parts must be got rid of before contraction of the sore\
is possible. For this purpose the free application of blisters, as first\
recommended by Syme, leaves little to be desired. Liquor epispasticus\
painted over the parts, or a large fly-blister (emplastrum cantharidis)\
applied all round the ulcer, speedily disperses the inflammatory\
products which cause the induration. The use of elastic pressure or of\
strapping, of hot-air baths, or the making of multiple incisions in the\
skin around the ulcer, fulfils the same object.\
\
As soon as the ulcer assumes the characters of a healing sore, it should\
be covered with skin-grafts, which furnish a much better cicatrix than\
that which forms when the ulcer is allowed to heal without such aid.\
\
A more radical method of treatment consists in excising the whole\
ulcer, including its edges and about a quarter of an inch of the\
surrounding tissue, as well as the underlying fibrous tissue, and\
grafting the raw surface.\
\
_Ambulatory Treatment._--When the circumstances of the patient forbid\
his lying up in bed, the healing of the ulcer is much delayed. He should\
be instructed to take every possible opportunity of placing the limb in\
an elevated position, and must constantly wear a firm bandage of\
_elastic webbing_. This webbing is porous and admits of evaporation of\
the skin and wound secretions--an advantage it has over Martin's rubber\
bandage. The bandage should extend from the toes to well above the knee,\
and should always be applied while the patient is in the recumbent\
position with the leg elevated, preferably before getting out of bed in\
the morning. Additional support is given to the veins if the bandage is\
applied as a figure of eight.\
\
We have found the following method satisfactory in out-patient\
practice. The patient lying on a couch, the limb is raised about\
eighteen inches and kept in this position for five minutes--till the\
excess of blood has left it. With the limb still raised, the ulcer with\
the surrounding skin is covered with a layer, about half an inch thick,\
of finely powdered boracic acid, and the leg, from foot to knee,\
excluding the sole, is enveloped in a thick layer of wood-wool wadding.\
This is held in position by ordinary cotton bandages, painted over with\
liquid starch; while the starch is drying the limb is kept elevated.\
With this appliance the patient may continue to work, and the dressing\
does not require to be changed oftener than once in three or four weeks\
(W. G. Richardson).\
\
When an ulcer becomes acutely _inflamed_ as a result of superadded\
infection, antiseptic measures are employed to overcome the infection,\
and ichthyol or other soothing applications may be used to allay the\
pain.\
\
The _phagedaenic ulcer_ calls for more energetic means of disinfection;\
the whole of the affected surface is touched with the actual cautery at\
a white heat, or is painted with pure carbolic acid. Relays of charcoal\
poultices are then applied until the spread of the disease is arrested.\
\
For the _irritable ulcer_ the most satisfactory treatment is complete\
excision and subsequent skin-grafting.\
\
\
\
\
CHAPTER VI\
\
GANGRENE\
\
\
Definition--Types: _Dry_, _Moist_--Varieties--Gangrene primarily due to\
    interference with circulation: _Senile gangrene_; _Embolic\
    gangrene_; _Gangrene following ligation of arteries_; _Gangrene\
    from mechanical causes_; _Gangrene from heat, chemical agents, and\
    cold_; _Diabetic gangrene_; _Gangrene associated with spasm of\
    blood vessels_; _Raynaud's disease_; _Angio-sclerotic gangrene_;\
    _Gangrene from ergot_. Bacterial varieties of gangrene.\
    _Pathology_--clinical varieties--_Acute infective gangrene_;\
    _Malignant oedema_; _Acute emphysematous_ or _gas gangrene_;\
    _Cancrum oris_, _etc_. Bed-sores: _Acute_; _chronic_.\
\
Gangrene or mortification is the process by which a portion of tissue\
dies _en masse_, as distinguished from the molecular or cellular death\
which constitutes ulceration. The dead portion is known as a _slough_.\
\
In this chapter we shall confine our attention to the process as it\
affects the limbs and superficial parts, leaving gangrene of the viscera\
to be described in regional surgery.\
\
\
TYPES OF GANGRENE\
\
Two distinct types of gangrene are met with, which, from their most\
obvious point of difference, are known respectively as _dry_ and\
_moist_, and there are several clinical varieties of each type.\
\
Speaking generally, it may be said that dry gangrene is essentially due\
to a simple _interference with the blood supply_ of a part; while the\
main factor in the production of moist gangrene is _bacterial\
infection_.\
\
The cardinal signs of gangrene are: change in the colour of the part,\
coldness, loss of sensation and motor power, and, lastly, loss of\
pulsation in the arteries.\
\
#Dry Gangrene# or #Mummification# is a comparatively slow form of local\
death due, as a rule, to a diminution in the arterial blood supply of\
the affected part, resulting from such causes as the gradual narrowing\
of the lumen of the arteries by disease of their coats, or the blocking\
of the main vessel by an embolus.\
\
As the fluids in the tissues are lost by evaporation the part becomes\
dry and shrivelled, and as the skin is usually intact, infection does\
not take place, or if it does, the want of moisture renders the part an\
unsuitable soil, and the organisms do not readily find a footing. Any\
spread of the process that may take place is chiefly influenced by the\
anatomical distribution of the blocked arteries, and is arrested as soon\
as it reaches an area rich in anastomotic vessels. The dead portion is\
then cast off, the irritation resulting from the contact of the dead\
with the still living tissue inducing the formation of granulations on\
the proximal side of the junction, and these by slowly eating into the\
dead portion produce a furrow--the _line of demarcation_--which\
gradually deepens until complete separation is effected. As the muscles\
and bones have a richer blood supply than the integument, the death of\
skin and subcutaneous tissues extends higher than that of muscles and\
bone, with the result that the stump left after spontaneous separation\
is conical, the end of the bone projecting beyond the soft parts.\
\
_Clinical Features._--The part undergoing mortification becomes colder\
than normal, the temperature falling to that of the surrounding\
atmosphere. In many instances, but not in all, the onset of the process\
is accompanied by severe neuralgic pain in the part, probably due to\
anaemia of the nerves, to neuritis, or to the irritation of the exposed\
axis cylinders by the dead and dying tissues around them. This pain soon\
ceases and gives place to a complete loss of sensation. The dead part\
becomes dry, horny, shrivelled, and semi-transparent--at first of a dark\
brown, but finally of a black colour, from the dissemination of blood\
pigment throughout the tissues. There is no putrefaction, and therefore\
no putrid odour; and the condition being non-infective, there is not\
necessarily any constitutional disturbance. In itself, therefore, dry\
gangrene does not involve immediate risk to life; the danger lies in the\
fact that the breach of surface at the line of demarcation furnishes a\
possible means of entrance for bacteria, which may lead to infective\
complications.\
\
#Moist Gangrene# is an acute process, the dead part retaining its fluids\
and so affording a favourable soil for the development of bacteria. The\
action of the organisms and their toxins on the adjacent tissues leads\
to a rapid and wide spread of the process. The skin becomes moist and\
macerated, and bullae, containing dark-coloured fluid or gases, form\
under the epidermis. The putrefactive gases evolved cause the skin to\
become emphysematous and crepitant and produce an offensive odour. The\
tissues assume a greenish-black colour from the formation in them of a\
sulphide of iron resulting from decomposition of the blood pigment.\
Under certain conditions the dead part may undergo changes resembling\
more closely those of ordinary post-mortem decomposition. Owing to its\
nature the spread of the gangrene is seldom arrested by the natural\
protective processes, and it usually continues until the condition\
proves fatal from the absorption of toxins into the circulation.\
\
The _clinical features_ vary in the different varieties of moist\
gangrene, but the local results of bacterial action and the\
constitutional disturbance associated with toxin absorption are present\
in all; the prognosis therefore is grave in the extreme.\
\
From what has been said, it will be gathered that in dry gangrene there\
is no urgent call for operation to save the patient's life, the primary\
indication being to prevent the access of bacteria to the dead part, and\
especially to the surface exposed at the line of demarcation. In moist\
gangrene, on the contrary, organisms having already obtained a footing,\
immediate removal of the dead and dying tissues, as a rule, offers the\
only hope of saving life.\
\
\
VARIETIES OF GANGRENE\
\
#Varieties of Gangrene essentially due to Interference with the\
Circulation#\
\
While the varieties of gangrene included in this group depend primarily\
on interference with the circulation, it is to be borne in mind that the\
clinical course of the affection may be profoundly influenced by\
superadded infection with micro-organisms. Although the bacteria do not\
play the most important part in producing tissue necrosis, their\
\
subsequent introduction is an accident of such importance that it may\
change the whole aspect of affairs and convert a dry form of gangrene\
into one of the moist type. Moreover, the low state of vitality of the\
tissues, and the extreme difficulty of securing and maintaining asepsis,\
make it a sequel of great frequency.\
\
#Senile Gangrene.#--Senile gangrene is the commonest example of local\
death produced by a _gradual_ diminution in the quantity of blood\
passing through the parts, as a result of arterio-sclerosis or other\
chronic disease of the arteries leading to diminution of their calibre.\
It is the most characteristic example of the dry type of gangrene. As\
the term indicates, it occurs in old persons, but the patient's age is\
to be reckoned by the condition of his arteries rather than by the\
number of his years. Thus the vessels of a comparatively young man who\
has suffered from syphilis and been addicted to alcohol are more liable\
to atheromatous degeneration leading to this form of gangrene than are\
those of a much older man who has lived a regular and abstemious life.\
This form of gangrene is much more common in men than in women. While it\
usually attacks only one foot, it is not uncommon for the other foot to\
be affected after an interval, and in some cases it is bilateral from\
the outset. It must clearly be understood that any form of gangrene may\
\
occur in old persons, the term senile being here restricted to that\
variety which results from arterio-sclerosis.\
\
[Illustration: FIG. 20.--Senile Gangrene of the Foot, showing line of\
demarcation.]\
\
_Clinical Features._--The commonest seat of the disease is in the toes,\
especially the great toe, whence it spreads up the foot to the heel, or\
even to the leg (Fig. 20). There is often a history of some slight\
injury preceding its onset. The vitality of the tissues is so low that\
the balance between life and death may be turned by the most trivial\
injury, such as a cut while paring a toe-nail or a corn, a blister\
caused by an ill-fitting shoe or the contact of a hot-bottle. In some\
cases the actual gangrene is determined by thrombosis of the popliteal\
or tibial arteries, which are already narrowed by obliterating\
endarteritis.\
\
It is common to find that the patient has been troubled for a long time\
before the onset of definite signs of gangrene, with cold feet, with\
tingling and loss of feeling, or a peculiar sensation as if walking on\
cotton wool.\
\
The first evidence of the death of the part varies in different cases.\
Sometimes a dark-blue spot appears on the medial side of the great toe\
and gradually increases in size; or a blister containing blood-stained\
fluid may form. Streaks or patches of dark-blue mottling appear higher\
up on the foot or leg. In other cases a small sore surrounded by a\
congested areola forms in relation to the nail and refuses to heal. Such\
sores on the toes of old persons are always to be looked upon with\
suspicion and treated with the greatest care; and the urine should be\
examined for sugar. There is often severe, deep-seated pain of a\
neuralgic character, with cramps in the limb, and these may persist long\
after a line of demarcation has formed. The dying part loses sensibility\
to touch and becomes cold and shrivelled.\
\
All the physical appearances and clinical symptoms associated with dry\
gangrene supervene, and the dead portion is delimited by a line of\
demarcation. If this forms slowly and irregularly it indicates a very\
unsatisfactory condition of the circulation; while, if it forms quickly\
and decidedly, the presumption is that the circulation in the parts\
above is fairly good. The separation of the dead part is always attended\
with the risk of infection taking place, and should this occur, the\
temperature rises and other evidences of toxaemia appear.\
\
_Prophylaxis._--The toes and feet of old people, the condition of whose\
circulation predisposes them to gangrene, should be protected from\
slight injuries such as may be received while paring nails, cutting\
corns, or wearing ill-fitting boots. The patient should also be warned\
of the risk of exposure to cold, the use of hot-bottles, and of placing\
the feet near a fire. Attempts have been made to improve the peripheral\
circulation by establishing an anastomosis between the main artery of a\
limb and its companion vein, so that arterial blood may reach the\
peripheral capillaries--reversal of the circulation--but the clinical\
results have proved disappointing. (See _Op. Surg._, p. 29.)\
\
_Treatment._--When there is evidence that gangrene has occurred, the\
first indication is to prevent infection by purifying the part, and\
after careful drying to wrap it in a thick layer of absorbent and\
antiseptic wool, retained in place by a loosely applied bandage. A\
slight degree of elevation of the limb is an advantage, but it must not\
be sufficient to diminish the amount of blood entering the part.\
Hot-bottles are to be used with the utmost caution. As absolute dryness\
is essential, ointments or other greasy dressings are to be avoided, as\
they tend to prevent evaporation from the skin. Opium should be given\
freely to alleviate pain. Stimulation is to be avoided, and the patient\
should be carefully dieted.\
\
When the gangrene is limited to the toes in old and feeble patients,\
some surgeons advocate the expectant method of treatment, waiting for a\
line of demarcation to form and allowing the dead part to be separated.\
This takes place so slowly, however, that it necessitates the patient\
being laid up for many weeks, or even months; and we agree with the\
majority in advising early amputation.\
\
In this connection it is worthy of note that there are certain points at\
which gangrene naturally tends to become arrested--namely, at the highly\
vascular areas in the neighbourhood of joints. Thus gangrene of the\
great toe often stops when it reaches the metatarso-phalangeal joint; or\
if it trespasses this limit it may be arrested either at the\
tarso-metatarsal or at the ankle joint. If these be passed, it usually\
spreads up the leg to just below the knee before signs of arrestment\
appear. Further, it is seen from pathological specimens that the spread\
is greater on the dorsal than on the plantar aspect, and that the death\
of skin and subcutaneous tissues extends higher than that of bone and\
muscle.\
\
These facts furnish us with indications as to the seat and method of\
amputation. Experience has proved that in senile gangrene of the lower\
extremity the most reliable and satisfactory results are obtained by\
amputating in the region of the knee, care being taken to perform the\
operation so as to leave the prepatellar anastomosis intact by retaining\
the patella in the anterior flap. The most satisfactory operation in\
these cases is Gritti's supra-condylar amputation. Haemorrhage is easily\
controlled by digital pressure, and the use of a tourniquet should be\
dispensed with, as the constriction of the limb is liable to interfere\
with the vitality of the flaps.\
\
When the tibial vessels can be felt pulsating at the ankle it may be\
justifiable, if the patient urgently desires it, to amputate lower than\
the knee; but there is considerable risk of gangrene recurring in the\
stump and necessitating a second operation.\
\
That amputation for senile gangrene performed between the ankle and the\
knee seldom succeeds, is explained by the fact that the vascular\
obstruction is usually in the upper part of the posterior tibial artery,\
and the operation is therefore performed through tissues with an\
inadequate blood supply. It is not uncommon, indeed, on amputating above\
the knee, to find even the popliteal artery plugged by a clot. This\
should be removed at the amputation by squeezing the vessel from above\
downward by a "milking" movement, or by "catheterising the artery" with\
the aid of a cannula with a terminal aperture.\
\
It is to be borne in mind that the object of amputation in these cases\
is merely to remove the gangrenous part, and so relieve the patient of\
the discomfort and the risks from infection which its presence involves.\
While it is true that in many of these patients the operation is borne\
remarkably well, it must be borne in mind that those who suffer from\
senile gangrene are of necessity bad lives, and a guarded opinion should\
be expressed as to the prospects of survival. The possibility of the\
disease developing in the other limb has already been referred to.\
\
[Illustration: FIG. 21.--Embolic Gangrene of Hand and Arm.]\
\
#Embolic Gangrene# (Fig. 21).--This is the most typical form of gangrene\
resulting from the _sudden_ occlusion of the main artery of a part,\
whether by the impaction of an embolus or the formation of a thrombus in\
its lumen, when the collateral circulation is not sufficiently free to\
maintain the vitality of the tissues.\
\
There is sudden pain at the site of impaction of the embolus, and the\
pulses beyond are lost. The limb becomes cold, numb, insensitive, and\
powerless. It is often pale at first--hence the term "white gangrene"\
sometimes applicable to the early appearances, which closely resemble\
those presented by the limb of a corpse.\
\
If the part is aseptic it shrivels, and presents the ordinary features\
of dry gangrene. It is liable, however, especially in the lower\
extremity and when the veins also are obstructed, to become infected and\
to assume the characters of the moist type.\
\
The extent of the gangrene depends upon the site of impaction of the\
embolus, thus if the _abdominal aorta_ becomes suddenly occluded by an\
embolus at its bifurcation, the obstruction of the iliacs and femorals\
induces symmetrical gangrene of both extremities as high as the inguinal\
ligaments. When gangrene follows occlusion of the _external iliac_ or of\
the _femoral artery_ above the origin of its deep branch, the death of\
the limb extends as high as the middle or upper third of the thigh. When\
the _femoral_ below the origin of its deep branch or the _popliteal\
artery_ is obstructed, the veins remaining pervious, the anastomosis\
through the profunda is sufficient to maintain the vascular supply, and\
gangrene does not necessarily follow. The rupture of a popliteal\
aneurysm, however, by compressing the vein and the articular branches,\
usually determines gangrene. When an embolus becomes impacted at the\
_bifurcation of the popliteal_, if gangrene ensues it usually spreads\
well up the leg.\
\
When the _axillary artery_ is the seat of embolic impaction, and\
gangrene ensues, the process usually reaches the middle of the upper\
arm. Gangrene following the blocking of the _brachial_ at its\
bifurcation usually extends as far as the junction of the lower and\
middle thirds of the forearm.\
\
Gangrene due to thrombosis or embolism is sometimes met with in patients\
recovering from typhus, typhoid, or other fevers, such as that\
associated with child-bed. It occurs in peripheral parts, such as the\
toes, fingers, nose, or ears.\
\
_Treatment._--The general treatment of embolic gangrene is the same as\
that for the senile form. Success has followed opening the artery and\
removing the embolus. The artery is exposed at the seat of impaction\
and, having been clamped above and below, a longitudinal opening is made\
and the clot carefully extracted with the aid of forceps; it is\
sometimes unexpectedly long (one recorded from the femoral artery\
measured nearly 34 inches); the wound in the artery is then sewn up with\
fine silk soaked in paraffin. When amputation is indicated, it must be\
performed sufficiently high to ensure a free vascular supply to the\
flaps.\
\
#Gangrene following Ligation of Arteries.#--After the ligation of an\
artery in its continuity--for example, in the treatment of aneurysm--the\
limb may for some days remain in a condition verging on gangrene, the\
distal parts being cold, devoid of sensation, and powerless. As the\
collateral circulation is established, the vitality of the tissues is\
gradually restored and these symptoms pass off. In some cases,\
however,--and especially in the lower extremity--gangrene ensues and\
presents the same characters as those resulting from embolism. It tends\
to be of the dry type. The occlusion of the vein as well as the artery\
is not found to increase the risk of gangrene.\
\
#Gangrene from Mechanical Constriction of the Vessels of the part.#--The\
application of a bandage or plaster-of-Paris case too tightly, or of a\
tourniquet for too long a time, has been known to lead to death of the\
part beyond; but such cases are rare, as are also those due to the\
pressure of a fractured bone or of a tumour on a large artery or vein.\
When gangrene occurs from such causes, it tends to be of the moist type.\
\
Much commoner is it to meet with localised areas of necrosis due to the\
excessive _pressure of splints_ over bony prominences, such as the\
lateral malleolus, the medial condyle of the humerus, or femur, or over\
the dorsum of the foot. This is especially liable to occur when the\
nutrition of the skin is depressed by any interference with its\
nerve-supply, such as follows injuries to the spine or peripheral\
nerves, disease of the brain, or acute anterior poliomyelitis. When the\
splint is removed the skin pressed upon is found to be of a pale yellow\
or grey colour, and is surrounded by a ring of hyperaemia. If protected\
from infection, the clinical course is that of dry gangrene.\
\
Bed-sores, which are closely allied to pressure sores, will be described\
at the end of this chapter.\
\
When a localised portion of tissue, for example, a piece of skin, is so\
severely _crushed_ or _bruised_ that its blood vessels are occluded and\
its structure destroyed, it dies, and, if not infected with bacteria,\
dries up, and the shrivelled brown skin is slowly separated by the\
growth of granulation tissue beneath and around it.\
\
Fingers, toes, or even considerable portions of limbs may in the same\
way be suddenly destroyed by severe trauma, and undergo mummification.\
If organisms gain access, typical moist gangrene may ensue, or changes\
similar to those of ordinary post-mortem decomposition may take place.\
\
_Treatment._--The first indication is to exclude bacteria by purifying\
the damaged part and its surroundings, and applying dry, non-irritating\
dressings.\
\
When these measures are successful, dry gangrene ensues. The raw surface\
left after the separation of the dead skin may be allowed to heal by\
granulation, or may be covered by skin-grafts. In the case of a finger\
or a limb it is not necessary to wait until spontaneous separation takes\
place, as this is often a slow process. When a well-marked line of\
demarcation has formed, amputation may be performed just sufficiently\
far above it to enable suitable flaps to be made.\
\
The end of a stump, after spontaneous separation of the gangrenous\
portion, requires to be trimmed, sufficient bone being removed to permit\
of the soft parts coming together.\
\
If moist gangrene supervenes, amputation must be performed without\
delay, and at a higher level.\
\
#Gangrene from Heat, Chemical Agents, and Cold.#--Severe #burns# and\
#scalds# may be followed by necrosis of tissue. So long as the parts are\
kept absolutely dry--as, for example, by the picric acid method of\
treatment--the grossly damaged portions of tissue undergo dry gangrene;\
but when wet or oily dressings are applied and organisms gain access,\
moist gangrene follows.\
\
Strong #chemical agents#, such as caustic potash, nitric or sulphuric\
acid, may also induce local tissue necrosis, the general appearances of\
the lesions produced being like those of severe burns. The resulting\
sloughs are slow to separate, and leave deep punched-out cavities which\
are long of healing.\
\
#Carbolic Gangrene.#--Carbolic acid, even in comparatively weak\
solution, is liable to induce dry gangrene when applied as a fomentation\
to a finger, especially in women and children. Thrombosis occurs in the\
blood vessels of the part, which at first is pale and soft, but later\
becomes dark and leathery. On account of the anaesthetic action of\
carbolic acid, the onset of the process is painless, and the patient\
does not realise his danger. A line of demarcation soon forms, but the\
dead part separates very slowly.\
\
#Gangrene from Frost-bite.#--It is difficult to draw the line between\
the third degree of chilblain and the milder forms of true frost-bite;\
the difference is merely one of degree. Frost-bite affects chiefly the\
toes and fingers--especially the great toe and the little finger--the\
ears, and the nose. In this country it is seldom seen except in members\
of the tramp class, who, in addition to being exposed to cold by\
sleeping in the open air, are ill-fed and generally debilitated. The\
condition usually manifests itself after the parts, having been\
subjected to extreme cold, are brought into warm surroundings. The first\
symptom is numbness in the part, followed by a sense of weight,\
tingling, and finally by complete loss of sensation. The part attacked\
becomes white and bleached-looking, feels icy cold, and is insensitive\
to touch. Either immediately, or, it may be, not for several days, it\
becomes discoloured and swollen, and finally contracts and shrivels.\
Above the dead area the limb may be the seat of excruciating pain. The\
dead portion is cast off, as in other forms of dry gangrene, by the\
formation of a line of demarcation.\
\
To prevent the occurrence of gangrene from frost-bite it is necessary to\
avoid the sudden application of heat. The patient should be placed in a\
cold room, and the part rubbed with snow, or put in a cold bath, and\
have light friction applied to it. As the circulation is restored the\
general surroundings and the local applications are gradually made\
warmer. Elevation of the part, wrapping it in cotton wool, and removal\
to a warmer room, are then permissible, and stimulants and warm drinks\
may be given with caution. When by these means the occurrence of\
gangrene is averted, recovery ensues, its onset being indicated by the\
white parts assuming a livid red hue and becoming the seat of an acute\
burning sensation.\
\
A condition known as _Trench feet_ was widely prevalent amongst the\
troops in France during the European War. Although allied to frost-bite,\
cold appears to play a less important part in its causation than\
humidity and constriction of the limbs producing ischaemia of the feet.\
Changes were found in the endothelium of the blood vessels, the axis\
cylinders of nerves, and the muscles. The condition does not occur in\
civil life.\
\
#Diabetic Gangrene.#--This form of gangrene is prone to occur in persons\
over fifty years of age who suffer from glycosuria. The arteries are\
often markedly diseased. In some cases the existence of the glycosuria\
is unsuspected before the onset of the gangrene, and it is only on\
examining the urine that the cause of the condition is discovered. The\
gangrenous process seldom begins as suddenly as that associated with\
embolism, and, like senile gangrene, which it may closely simulate in\
its early stages, it not infrequently begins after a slight injury to\
one of the toes. It but rarely, however, assumes the dry, shrivelling\
type, as a rule being attended with swelling, oedema, and dusky redness\
of the foot, and severe pain. According to Paget, the dead part remains\
warm longer than in other forms of senile gangrene; there is a greater\
tendency for patches of skin at some distance from the primary seat of\
disease to become gangrenous, and for the death of tissue to extend\
upwards in the subcutaneous planes, leaving the overlying skin\
unaffected. The low vitality of the tissues favours the growth of\
bacteria, and if these gain access, the gangrene assumes the characters\
of the moist type and spreads rapidly.\
\
The rules for amputation are the same as those governing the treatment\
of senile gangrene, the level at which the limb is removed depending\
upon whether the gangrene is of the dry or moist type. The general\
treatment for diabetes must, of course, be employed whether amputation\
is performed or not. Paget recommended that the dietetic treatment\
should not be so rigid as in uncomplicated diabetes, and that opium\
should be given freely.\
\
The _prognosis_ even after amputation is unfavourable. In many cases the\
patient dies with symptoms of diabetic coma within a few days of the\
operation; or, if he survives this, he may eventually succumb to\
diabetes. In others there is sloughing of the flaps and death results\
from toxaemia. Occasionally the other limb becomes gangrenous. On the\
other hand, the glycosuria may diminish or may even disappear after\
amputation.\
\
#Gangrene associated with Spasm of Blood Vessels.#--#Raynaud's Disease#,\
or symmetrical gangrene, is supposed to be due to spasm of the\
arterioles, resulting from peripheral neuritis. It occurs oftenest in\
women, between the ages of eighteen and thirty, who are the subjects of\
uterine disorders, anaemia, or chlorosis. Cold is an aggravating factor,\
as the disease is commonest during the winter months. The digits of both\
hands or the toes of both feet are simultaneously attacked, and the\
disease seldom spreads beyond the phalanges or deeper than the skin.\
\
The first evidence is that the fingers become cold, white, and\
insensitive to touch and pain. These attacks of _local syncope_ recur at\
varying intervals for months or even years. They last for a few minutes\
or even for some hours, and as they pass off the parts become hyperaemic\
and painful.\
\
A more advanced stage of the disease is known as _local asphyxia_. The\
circulation through the fingers becomes exceedingly sluggish, and the\
parts assume a dull, livid hue. There is swelling and burning or\
shooting pain. This may pass off in a few days, or may increase in\
severity, with the formation of bullae, and end in dry gangrene. As a\
rule, the slough which forms is comparatively small and superficial,\
but it may take some months to separate. The condition tends to recur in\
successive winters.\
\
The _treatment_ consists in remedying any nervous or uterine disorder\
that may be present, keeping the parts warm by wrapping them in cotton\
wool, and in the use of hot-air or electric baths, the parts being\
immersed in water through which a constant current is passed. When\
gangrene occurs, it is treated on the same lines as other forms of dry\
gangrene, but if amputation is called for it is only with a view to\
removing the dead part.\
\
#Angio-sclerotic Gangrene.#--A form of gangrene due to _angio-sclerosis_\
is occasionally met with in young persons, even in children. It bears\
certain analogies to Raynaud's disease in that spasm of the vessels\
plays a part in determining the local death.\
\
The main arteries are narrowed by hyperplastic endarteritis followed by\
thrombosis, and similar changes are found in the veins. The condition is\
usually met with in the feet, but the upper extremity may be affected,\
and is attended with very severe pain, rendering sleep impossible.\
\
The patient is liable to sudden attacks of numbness, tingling and\
weakness of the limbs which pass off with rest--_intermittent\
claudication_. During these attacks the large arteries--femoral,\
brachial, and subclavian--can be felt as firm cords, while pulsation is\
lost in the peripheral vessels. Gangrene eventually ensues, is attended\
with great pain and runs a slow course. It is treated on the same lines\
as Raynaud's disease.\
\
#Gangrene from Ergot.#--Gangrene may occur from interference with blood\
supply, the result of tetanic contraction of the minute vessels, such as\
results in ill-nourished persons who eat large quantities of coarse rye\
bread contaminated with the _claviceps purpurea_ and containing the\
ergot of rye. It has also occurred in the fingers of patients who have\
taken ergot medicinally over long periods. The gangrene, which attacks\
the toes, fingers, ears, or nose, is preceded by formication, numbness,\
and pains in the parts to be affected, and is of the dry variety.\
\
In this country it is usually met with in sailors off foreign ships,\
whose dietary largely consists of rye bread. Trivial injuries may be the\
starting-point, the anaesthesia produced by the ergotin preventing the\
patient taking notice of them. Alcoholism is a potent predisposing\
cause.\
\
As it is impossible to predict how far the process will spread, it is\
advisable to wait for the formation of a line of demarcation before\
operating, and then to amputate immediately above the dead part.\
\
\
BACTERIAL VARIETIES OF GANGRENE\
\
The acute bacillary forms of gangrene all assume the moist type from the\
first, and, spreading rapidly, result in extensive necrosis of tissue,\
and often end fatally.\
\
The infection is usually a mixed one in which anaerobic bacteria\
predominate. The anaerobe most constantly present is the _bacillus\
aerogenes capsulatus_, usually in association with other anaerobes, and\
sometimes with pyogenic diplo- and streptococci. According to the mode of\
action of the associated organisms and the combined effects of their\
toxins on the tissues, the gangrenous process presents different\
pathological and clinical features. Some combinations, for example,\
result in a rapidly spreading cellulitis with early necrosis of\
connective tissue accompanied by thrombosis throughout the capillary and\
venous circulation of the parts implicated; other combinations cause\
great oedema of the part, and others again lead to the formation of gases\
in the tissues, particularly in the muscles.\
\
These different effects do not appear to be due to a specific action of\
any one of the organisms present, but to the combined effect of a\
particular group living in symbiosis.\
\
According as the cellulitic, the oedematous, or the gaseous\
characteristics predominate, the clinical varieties of bacillary\
gangrene may be separately described, but it must be clearly understood\
that they frequently overlap and cannot always be distinguished from one\
another.\
\
#Clinical Varieties of Bacillary Gangrene.#--#Acute infective gangrene#\
is the form most commonly met with in civil practice. It may follow such\
trivial injuries as a pin-prick or a scratch, the signs of acute\
cellulitis rapidly giving place to those of a spreading gangrene. Or it\
may ensue on a severe railway, machinery, or street accident, when\
lacerated and bruised tissues are contaminated with gross dirt. Often\
within a few hours of the injury the whole part rapidly becomes painful,\
swollen, oedematous, and tense. The skin is at first glazed, and perhaps\
paler than normal, but soon assumes a dull red or purplish hue, and\
bullae form on the surface. Putrefactive gases may be evolved in the\
tissues, and their presence is indicated by emphysematous crackling when\
the part is handled. The spread of the disease is so rapid that its\
progress is quite visible from hour to hour, and may be traced by the\
occurrence of red lines along the course of the lymphatics of the limb.\
In the most acute cases the death of the affected part takes place so\
rapidly that the local changes indicative of gangrene have not time to\
occur, and the fact that the part is dead may be overlooked.\
\
[Illustration: FIG. 22.--Gangrene of Terminal Phalanx of Index-Finger,\
following cellulitis of hand resulting from a scratch on the palm of the\
hand.]\
\
Rigors may occur, but the temperature is not necessarily raised--indeed,\
it is sometimes subnormal. The pulse is small, feeble, rapid, and\
irregular. Unless amputation is promptly performed, death usually\
follows within thirty-six or forty-eight hours. Even early operation\
does not always avert the fatal issue, because the quantity of toxin\
absorbed and its extreme virulence are often more than even a robust\
subject can outlive.\
\
_Treatment._--Every effort must be made to purify all such wounds as are\
contaminated by earth, street dust, stable refuse, or other forms of\
gross dirt. Devitalised and contaminated tissue is removed with the\
knife or scissors and the wound purified with antiseptics of the\
chlorine group or with hydrogen peroxide. If there is a reasonable\
prospect that infection has been overcome, the wound may be at once\
sutured, but if this is doubtful it is left open and packed or\
irrigated.\
\
When acute gangrene has set in no treatment short of amputation is of\
any avail, and the sooner this is done, the greater is the hope of\
saving the patient. The limb must be amputated well beyond the apparent\
limits of the infected area, and stringent precautions must be taken to\
avoid discharge from the already gangrenous area reaching the operation\
wound. An assistant or nurse, who is to take no other part in the\
operation, is told off to carry out the preliminary purification, and to\
hold the limb during the operation.\
\
#Malignant Oedema.#--This form of acute gangrene has been defined as\
"a spreading inflammatory oedema attended with emphysema, and ultimately\
followed by gangrene of the skin and adjacent parts." The predominant\
organism is the _bacillus of malignant oedema_ or _vibrion septique_ of\
Pasteur, which is found in garden soil, dung, and various putrefying\
substances. It is anaerobic, and occurs as long, thick rods with\
somewhat rounded ends and several laterally placed flagella. Spores,\
which have a high power of resistance, form in the centre of the rods,\
and bulge out the sides so as to give the organisms a spindle-shaped\
outline. Other pathogenic organisms are also present and aid the\
specific bacillus in its action.\
\
At the bedside it is difficult, if not impossible, to distinguish it\
from acute infective gangrene. Both follow on the same kinds of injury\
and run an exceedingly rapid course. In malignant oedema, however, the\
incidence of the disease is mainly on the superficial parts, which\
become oedematous and emphysematous, and acquire a marbled appearance\
with the veins clearly outlined. Early disappearance of sensation is a\
particularly grave symptom. Bullae form on the skin, and the tissues\
have "a peculiar heavy but not putrid odour." The constitutional effects\
are extremely severe, and death may ensue within a few hours.\
\
#Acute Emphysematous# or #Gas Gangrene# was prevalent in certain areas\
at various periods during the European War. It follows infection of\
lacerated wounds with the _bacillus aerogenes capsulatus_, usually in\
combination with other anaerobes, and its main incidence is on the\
muscles, which rapidly become infiltrated with gas that spreads\
throughout the whole extent of the muscle, disintegrating its fibres and\
leading to necrosis. The gangrenous process spreads with appalling\
rapidity, the limb becoming enormously swollen, painful, and crepitant\
or even tympanitic. Patches of coppery or purple colour appear on the\
skin, and bullae containing blood-stained serum form on the surface. The\
toxaemia is profound, and the face and lips assume a characteristic\
cyanosis. The condition is attended with a high mortality. Only in the\
early stages and when the infection is limited are local measures\
successful in arresting the spread; in more severe cases amputation is\
the only means of saving life.\
\
#Cancrum Oris# or #Noma#.--This disease is believed to be due to a\
specific bacillus, which occurs in long delicate rods, and is chiefly\
found at the margin of the gangrenous area. It is prone to attack\
unhealthy children from two to five years of age, especially during\
their convalescence from such diseases as measles, scarlet fever, or\
typhoid, but may attack adults when they are debilitated. It is most\
common in the mouth, but sometimes occurs on the vulva. In the mouth it\
begins as an ulcerative stomatitis, more especially affecting the gums\
or inner aspect of the cheek. The child lies prostrated, and from the\
open mouth foul-smelling saliva, streaked with blood, escapes; the face\
is of an ashy-grey colour, the lips dark and swollen. On the inner\
aspect of the cheek is a deeply ulcerated surface, with sloughy shreds\
of dark-brown or black tissue covering its base; the edges are\
irregular, firm, and swollen, and the surrounding mucous membrane is\
infiltrated and oedematous. In the course of a few hours a dark spot\
appears on the outer aspect of the cheek, and rapidly increases in size;\
towards the centre it is black, shading off through blue and grey into a\
dark-red area which extends over the cheek (Fig. 23). The tissue\
implicated is at first firm and indurated, but as it loses its vitality\
it becomes doughy and sodden. Finally a slough forms, and, when it\
separates, the cheek is perforated.\
\
Meanwhile the process spreads inside the mouth, and the gums, the floor\
of the mouth, or even the jaws, may become gangrenous and the teeth fall\
out. The constitutional disturbance is severe, the temperature raised,\
and the pulse feeble and rapid.\
\
The extremely foetid odour which pervades the room or even the house the\
patient occupies, is usually sufficient to suggest the diagnosis of\
cancrum oris. The odour must not be mistaken for that due to\
decomposition of sordes on the teeth and gums of a debilitated patient.\
\
The _prognosis_ is always grave in the extreme, the main risks being\
general toxaemia and septic pneumonia. When recovery takes place there is\
serious deformity, and considerable portions of the jaws may be lost by\
necrosis.\
\
[Illustration: FIG. 23.--Cancrum oris.\
\
(From a photograph lent by Sir George T. Beatson.)]\
\
_Treatment._--The only satisfactory treatment is thorough removal under\
an anaesthetic of all the sloughy tissue, with the surrounding zone in\
which the organisms are active. This is most efficiently accomplished by\
the knife or scissors, cutting until the tissue bleeds freely, after\
which the raw surface is painted with undiluted carbolic acid and\
dressed with iodoform gauze. It may be necessary to remove large pieces\
of bone when the necrotic process has implicated the jaws. The mouth\
must be constantly sprayed with peroxide of hydrogen, and washed out\
with a disinfectant and deodorant lotion, such as Condy's fluid. The\
patient's general condition calls for free stimulation.\
\
The deformity resulting from these necessarily heroic measures is not so\
great as might be expected, and can be further diminished by plastic\
operations, which should be undertaken before cicatricial contraction\
has occurred.\
\
\
BED-SORES\
\
Bed-sores are most frequently met with in old and debilitated patients,\
or in those whose tissues are devitalised by acute or chronic diseases\
associated with stagnation of blood in the peripheral veins. Any\
interference with the nerve-supply of the skin, whether from injury or\
disease of the central nervous system or of the peripheral nerves,\
strongly predisposes to the formation of bed-sores. Prolonged and\
excessive pressure over a bony prominence, especially if the parts be\
moist with skin secretions, urine, or wound discharges, determines the\
formation of a sore. Excoriations, which may develop into true\
bed-sores, sometimes form where two skin surfaces remain constantly\
apposed, as in the region of the scrotum or labium, under pendulous\
mammae, or between fingers or toes confined in a splint.\
\
[Illustration: FIG. 24.--Acute Bed-Sores over Right Buttock.]\
\
_Clinical Features._--Two clinical varieties are met with--the acute\
and the chronic bed-sore.\
\
The _acute_ bed-sore usually occurs over the sacrum or buttock. It\
develops rapidly after spinal injuries and in the course of certain\
brain diseases. The part affected becomes red and congested, while the\
surrounding parts are oedematous and swollen, blisters form, and the skin\
loses its vitality (Fig. 24).\
\
In advanced cases of general paralysis of the insane, a peculiar form of\
acute bed-sore beginning as a blister, and passing on to the formation\
of a black, dry eschar, which slowly separates, occurs on such parts as\
the medial side of the knee, the angle of the scapula, and the heel.\
\
The _chronic_ bed-sore begins as a dusky reddish purple patch, which\
gradually becomes darker till it is almost black. The parts around are\
oedematous, and a blister may form. This bursts and exposes the papillae\
of the skin, which are of a greenish hue. A tough greyish-black slough\
forms, and is slowly separated. It is not uncommon for the gangrenous\
area to continue to spread both in width and in depth till it reaches\
the periosteum or bone. Bed-sores over the sacrum sometimes implicate\
the vertebral canal and lead to spinal meningitis, which usually proves\
fatal.\
\
In old and debilitated patients the septic absorption taking place from\
a bed-sore often proves a serious complication of other surgical\
conditions. From this cause, for example, old people may succumb during\
the treatment of a fractured thigh.\
\
The granulating surface left on the separation of the slough tends to\
heal comparatively rapidly.\
\
_Prevention of Bed-sores._--The first essential in the prevention of\
bed-sores is the regular changing of the patient's position, so that no\
one part of the body is continuously pressed upon for any length of\
time. Ring-pads of wool, air-cushions, or water-beds are necessary to\
remove pressure from prominent parts. Absolute dryness of the skin is\
all-important. At least once a day, the sacrum, buttocks,\
shoulder-blades, heels, elbows, malleoli, or other parts exposed to\
pressure, must be sponged with soap and water, thoroughly dried, and\
then rubbed with methylated spirit, which is allowed to dry on the skin.\
Dusting the part with boracic acid powder not only keeps it dry, but\
prevents the development of bacteria in the skin secretions.\
\
In operation cases, care must be taken that irritating chemicals used to\
purify the skin do not collect under the patient and remain in contact\
with the skin of the sacrum and buttocks during the time he is on the\
operating-table. There is reason to believe that the so-called\
"post-operation bed-sore" may be due to such causes. A similar result\
has been known to follow soiling of the sheets by the escape of a\
turpentine enema.\
\
_Treatment._--Once a bed-sore has formed, every effort must be made to\
prevent its spread. Alcohol is used to cleanse the broken surface, and\
dry absorbent dressings are applied and frequently changed. It is\
sometimes found necessary to employ moist or oily substances, such as\
boracic poultices, eucalyptus ointment, or balsam of Peru, to facilitate\
the separation of sloughs, or to promote the growth of granulations. In\
patients who are not extremely debilitated the slough may be excised,\
the raw surface scraped, and then painted with iodine.\
\
Skin-grafting is sometimes useful in covering in the large raw surface\
left after separation or removal of sloughs.\
\
\
\
\
CHAPTER VII\
\
BACTERIAL AND OTHER WOUND INFECTIONS\
\
\
_Erysipelas_--_Diphtheria_--_Tetanus_--_Hydrophobia_--_Anthrax_--\
    _Glanders_--_Actinomycosis_--_Mycetoma_--_Delhi\
    boil_--_Chigoe_--_Poisoning by insects_--_Snake-bites_.\
\
\
ERYSIPELAS\
\
Erysipelas, popularly known as "rose," is an acute spreading infective\
disease of the skin or of a mucous membrane due to the action of a\
streptococcus. Infection invariably takes place through an abrasion of\
the surface, although this may be so slight that it escapes observation\
even when sought for. The streptococci are found most abundantly in the\
lymph spaces just beyond the swollen margin of the inflammatory area,\
and in the serous blebs which sometimes form on the surface.\
\
#Clinical Features.#--_Facial erysipelas_ is the commonest clinical\
variety, infection usually occurring through some slight abrasion in the\
region of the mouth or nose, or from an operation wound in this area.\
From this point of origin the inflammation may spread all over the face\
and scalp as far back as the nape of the neck. It stops, however, at the\
chin, and never extends on to the front of the neck. There is great\
oedema of the face, the eyes becoming closed up, and the features\
unrecognisable. The inflammation may spread to the meninges, the\
intracranial venous sinuses, the eye, or the ear. In some cases the\
erysipelas invades the mucous membrane of the mouth, and spreads to the\
fauces and larynx, setting up an oedema of the glottis which may prove\
dangerous to life.\
\
Erysipelas occasionally attacks an operation wound that has become\
septic; and it may accompany septic infection of the genital tract in\
puerperal women, or the separation of the umbilical cord in infants\
(_erysipelas neonatorum_). After an incubation period, which varies from\
fifteen to sixty hours, the patient complains of headache, pains in the\
back and limbs, loss of appetite, nausea, and frequently there is\
vomiting. He has a chill or slight rigor, initiating a rise of\
temperature to 103 o, 104 o, or 105 o F.; and a full bounding pulse of\
about 100 (Fig. 25). The tongue is foul, the breath heavy, and, as a\
rule, the bowels are constipated. There is frequently albuminuria, and\
occasionally nocturnal delirium. A moderate degree of leucocytosis\
(15,000 to 20,000) is usually present.\
\
Around the seat of inoculation a diffuse red patch forms, varying in hue\
from a bright scarlet to a dull brick-red. The edges are slightly raised\
above the level of the surrounding skin, as may readily be recognised by\
gently stroking the part from the healthy towards the affected area. The\
skin is smooth, tense, and glossy, and presents here and there blisters\
filled with serous fluid. The local temperature is raised, and the part\
is the seat of a burning sensation and is tender to the touch, the most\
tender area being the actively spreading zone which lies about half an\
inch beyond the red margin.\
\
[Illustration: FIG. 25.--Chart of Erysipelas occurring in a wound.]\
\
The disease tends to spread spasmodically and irregularly, and the\
direction and extent of its progress may be recognised by mapping out\
the peripheral zone of tenderness. Red streaks appear along the lines of\
the superficial lymph vessels, and the deep lymphatics may sometimes be\
palpated as firm, tender cords. The neighbouring glands, also, are\
generally enlarged and tender.\
\
The disease lasts for from two or three days to as many weeks, and\
relapses are frequent. Spontaneous resolution usually takes place, but\
the disease may prove fatal from absorption of toxins, involvement of\
the brain or meninges, or from general streptococcal infection.\
\
#Complications.#--_Diffuse suppurative cellulitis_ is the most serious\
local complication, and results from a mixed infection with other\
pyogenic bacteria. Small _localised superficial abscesses_ may form\
during the convalescent stage. They are doubtless due to the action of\
skin bacteria, which attack the tissues devitalised by the erysipelas. A\
persistent form of _oedema_ sometimes remains after recurrent attacks of\
erysipelas, especially when they affect the face or the lower extremity,\
a condition which is referred to with elephantiasis.\
\
#Treatment.#--The first indication is to endeavour to arrest the spread\
of the process. We have found that by painting with linimentum iodi, a\
ring half an inch broad, about an inch in front of the peripheral tender\
zone--not the red margin--an artificial leucocytosis is produced, and\
the advancing streptococci are thereby arrested. Several coats of the\
iodine are applied, one after the other, and this is repeated daily for\
several days, even although the erysipelas has not overstepped the ring.\
Success depends upon using the liniment of iodine (the tincture is not\
strong enough), and in applying it well in front of the disease. To\
allay pain the most useful local applications are ichthyol ointment (1\
in 6), or lead and opium fomentations.\
\
The general treatment consists in attending to the emunctories, in\
administrating quinine in small--two-grain--doses every four hours, or\
salicylate of iron (2-5 gr. every three hours), and in giving plenty of\
fluid nourishment. It is worthy of note that the anti-streptococcic\
serum has proved of less value in the treatment of erysipelas than might\
have been expected, probably because the serum is not made from the\
proper strain of streptococcus.\
\
It is not necessary to isolate cases of erysipelas, provided the usual\
precautions against carrying infection from one patient to another are\
rigidly carried out.\
\
\
DIPHTHERIA\
\
Diphtheria is an acute infective disease due to the action of a specific\
bacterium, the _bacillus diphtheriae_ or _Klebs-Loffler bacillus_. The\
disease is usually transmitted from one patient to another, but it may\
be contracted from cats, fowls, or through the milk of infected cows.\
Cases have occurred in which the surgeon has carried the infection from\
one patient to another through neglect of antiseptic precautions. The\
incubation period varies from two to seven days.\
\
#Clinical Features.#--In _pharyngeal diphtheria_, on the first or\
second day of the disease, redness and swelling of the mucous membrane\
of the pharynx, tonsils, and palate are well marked, and small, circular\
greenish or grey patches of false membrane, composed of necrosed\
epithelium, fibrin, leucocytes, and red blood corpuscles, begin to\
appear. These rapidly increase in area and thickness, till they coalesce\
and form a complete covering to the parts. In the pharynx the false\
membrane is less adherent to the surface than it is when the disease\
affects the air-passages. The diphtheritic process may spread from the\
pharynx to the nasal cavities, causing blocking of the nares, with a\
profuse ichorous discharge from the nostrils, and sometimes severe\
epistaxis. The infection may spread along the nasal duct to the\
conjunctiva. The middle ear also may become involved by spread along the\
auditory (Eustachian) tube.\
\
The lymph glands behind the angle of the jaw enlarge and become tender,\
and may suppurate from superadded infection. There is pain on\
swallowing, and often earache; and the patient speaks with a nasal\
accent. He becomes weak and anaemic, and loses his appetite. There is\
often albuminuria. Leucocytosis is usually well marked before the\
injection of antitoxin; after the injection there is usually a\
diminution in the number of leucocytes. The false membrane may separate\
and be cast off, after which the patient gradually recovers. Death may\
take place from gradual failure of the heart's action or from syncope\
during some slight exertion.\
\
_Laryngeal Diphtheria._--The disease may arise in the larynx, although,\
as a rule, it spreads thence from the pharynx. It first manifests itself\
by a short, dry, croupy cough, and hoarseness of the voice. The first\
difficulty in breathing usually takes place during the night, and once\
it begins, it rapidly gets worse. Inspiration becomes noisy, sometimes\
stridulous or metallic or sibilant, and there is marked indrawing of the\
epigastrium and lower intercostal spaces. The hoarseness becomes more\
marked, the cough more severe, and the patient restless. The difficulty\
of breathing occurs in paroxysms, which gradually increase in frequency\
and severity, until at length the patient becomes asphyxiated. The\
duration of the disease varies from a few hours to four or five days.\
\
After the acute symptoms have passed off, various localised\
paralyses may develop, affecting particularly the nerves of the palatal\
and orbital muscles, less frequently the lower limbs.\
\
#Diagnosis.#--The finding of the Klebs-Loffler bacillus is the only\
conclusive evidence of the disease. The bacillus may be obtained by\
swabbing the throat with a piece of aseptic--not antiseptic--cotton wool\
or clean linen rag held in a pair of forceps, and rotated so as to\
entangle portions of the false membrane or exudate. The swab thus\
obtained is placed in a test-tube, previously sterilised by having had\
some water boiled in it, and sent to a laboratory for investigation. To\
identify the bacillus a piece of the membrane from the swab is rubbed on\
a cover glass, dried, and stained with methylene blue or other basic\
stain; or cultures may be made on agar or other suitable medium. When a\
bacteriological examination is impossible, or when the clinical features\
do not coincide with the results obtained, the patient should always be\
treated on the assumption that he suffers from diphtheria. So much doubt\
exists as to the real nature of membranous croup and its relationship to\
true diphtheria, that when the diagnosis between the two is uncertain\
the safest plan is to treat the case as one of diphtheria.\
\
In children, diphtheria may occur on the vulva, vagina, prepuce, or\
glans penis, and give rise to difficulty in diagnosis, which is only\
cleared up by demonstration of the bacillus.\
\
#Treatment.#--An attempt may be made to destroy or to counteract the\
organisms by swabbing the throat with strong antiseptic solutions, such\
as 1 in 1000 corrosive sublimate or 1 in 30 carbolic acid, or by\
spraying with peroxide of hydrogen.\
\
The antitoxic serum is our sheet-anchor in the treatment of diphtheria,\
and recourse should be had to its use as early as possible.\
\
Difficulty of swallowing may be met by the use of a stomach tube passed\
either through the mouth or nose. When this is impracticable, nutrient\
enemata are called for.\
\
In laryngeal diphtheria, the interference with respiration may call for\
intubation of the larynx, or tracheotomy, but the antitoxin treatment\
has greatly diminished the number of cases in which it becomes necessary\
to have recourse to these measures.\
\
Intubation consists in introducing through the mouth into the larynx a\
tube which allows the patient to breathe freely during the period while\
the membrane is becoming separated and thrown off. This is best done\
with the apparatus of O'Dwyer; but when this instrument is not\
available, a simple gum-elastic catheter with a terminal opening (as\
suggested by Macewen and Annandale) may be employed.\
\
When intubation is impracticable, the operation of tracheotomy is\
called for if the patient's life is endangered by embarrassment of\
respiration. Unless the patient is in hospital with skilled assistance\
available, tracheotomy is the safer of the two procedures.\
\
\
TETANUS\
\
Tetanus is a disease resulting from infection of a wound by a specific\
micro-organism, the _bacillus tetani_, and characterised by increased\
reflex excitability, hypertonus, and spasm of one or more groups of\
voluntary muscles.\
\
_Etiology and Morbid Anatomy._--The tetanus bacillus, which is a perfect\
anaerobe, is widely distributed in nature and can be isolated from\
garden earth, dung-heaps, and stable refuse. It is a slender rod-shaped\
bacillus, with a single large spore at one end giving it the shape of a\
drum-stick (Fig. 26). The spores, which are the active agents in\
producing tetanus, are highly resistant to chemical agents, retain their\
vitality in a dry condition, and even survive boiling for five minutes.\
\
The organism does not readily establish itself in the human body, and\
seems to flourish best when it finds a nidus in necrotic tissue and is\
accompanied by aerobic organisms, which, by using up the oxygen in the\
tissues, provide for it a suitable environment. The presence of a\
foreign body in the wound seems to favour its action. The infection is\
for all practical purposes a local one, the symptoms of the disease\
being due to the toxins produced in the wound of infection acting upon\
the central nervous system.\
\
The toxin acts principally on the nerve centres in the spinal medulla,\
to which it travels from the focus of infection by way of the nerve\
fibres supplying the voluntary muscles. Its first effect on the motor\
ganglia of the cord is to render them hypersensitive, so that they are\
excited by mild stimuli, which under ordinary conditions would produce\
no reaction. As the toxin accumulates the reflex arc is affected, with\
the result that when a stimulus reaches the ganglia a motor discharge\
takes place, which spreads by ascending and descending collaterals to\
the reflex apparatus of the whole cord. As the toxin spreads it causes\
both motor hyper-tonus and hyper-excitability, which accounts for the\
tonic contraction and the clonic spasms characteristic of tetanus.\
\
[Illustration: FIG. 26.--Bacillus of Tetanus from scraping of a wound of\
finger, x 1000 diam. Basic fuchsin stain.]\
\
#Clinical Varieties of Tetanus.#--_Acute_ or _Fulminating\
Tetanus_.--This variety is characterised by the shortness of the\
incubation period, the rapidity of its progress, the severity of its\
symptoms, and its all but universally fatal issue in spite of\
treatment, death taking place in from one to four days. The\
characteristic symptoms may appear within three or four days of the\
infliction of the wound, but the incubation period may extend to three\
weeks, and the wound may be quite healed before the disease declares\
itself--_delayed tetanus_. Usually, however, the wound is inflamed and\
suppurating, with ragged and sloughy edges. A slight feverish attack may\
mark the onset of the tetanic condition, or the patient may feel\
perfectly well until the spasms begin. If careful observations be made,\
it may be found that the muscles in the immediate neighbourhood of the\
wound are the first to become contracted; but in the majority of\
instances the patient's first complaint is of pain and stiffness in the\
muscles of mastication, notably the masseter, so that he has difficulty\
in opening the mouth--hence the popular name "lock-jaw." The muscles of\
expression soon share in the rigidity, and the face assumes a taut,\
mask-like aspect. The angles of the mouth may be retracted, producing a\
grinning expression known as the _risus sardonicus_.\
\
The next muscles to become stiff and painful are those of the neck,\
especially the sterno-mastoid and trapezius. The patient is inclined to\
attribute the pain and stiffness to exposure to cold or rheumatism. At\
an early stage the diaphragm and the muscles of the anterior abdominal\
wall become contracted; later the muscles of the back and thorax are\
involved; and lastly those of the limbs. Although this is the typical\
order of involvement of the different groups of muscles, it is not\
always adhered to.\
\
To this permanent tonic contraction of the muscles there are soon added\
clonic spasms. These spasms are at first slight and transient, with\
prolonged intervals between the attacks, but rapidly tend to become more\
frequent, more severe, and of longer duration, until eventually the\
patient simply passes out of one seizure into another.\
\
The distribution of the spasms varies in different cases: in some it is\
confined to particular groups of muscles, such as those of the neck,\
back, abdominal walls, or limbs; in others all these groups are\
simultaneously involved.\
\
When the muscles of the back become spasmodically contracted, the body\
is raised from the bed, sometimes to such an extent that the patient\
rests only on his heels and occiput--the position of _opisthotonos_.\
Lateral arching of the body from excessive action of the muscles on one\
side--_pleurosthotonos_--is not uncommon, the arching usually taking\
place towards the side on which the wound of infection exists. Less\
frequently the body is bent forward so that the knees and chin almost\
meet (_emprosthotonos_). Sometimes all the muscles simultaneously become\
rigid, so that the body assumes a statuesque attitude (_orthotonos_).\
When the thoracic muscles, including the diaphragm, are thrown into\
spasm, the patient experiences a distressing sensation as if he were\
gripped in a vice, and has extreme difficulty in getting breath. Between\
the attacks the limbs are kept rigidly extended. The clonic spasms may\
be so severe as to rupture muscles or even to fracture one of the long\
bones.\
\
As time goes on, the clonic exacerbations become more and more frequent,\
and the slightest external stimulus, such as the feeling of the pulse, a\
whisper in the room, a noise in the street, a draught of cold air, the\
effort to swallow, a question addressed to the patient or his attempt to\
answer, is sufficient to determine an attack. The movements are so\
forcible and so continuous that the nurse has great difficulty in\
keeping the bedclothes on the patient, or even in keeping him in bed.\
\
The general condition of the patient is pitiful in the extreme. He is\
fully conscious of the gravity of the disease, and his mind remains\
clear to the end. The suffering induced by the cramp-like spasms of the\
muscles keeps him in a constant state of fearful apprehension of the\
next seizure, and he is unable to sleep until he becomes utterly\
exhausted.\
\
The temperature is moderately raised (100 o to 102 o F.), or may remain\
normal throughout. Shortly before death very high temperatures (110 o F.)\
have been recorded, and it has been observed that the thermometer\
sometimes continues to rise after death, and may reach as high as\
112 o F. or more.\
\
The pulse corresponds with the febrile condition. It is accelerated\
during the spasms, and may become exceedingly rapid and feeble before\
death, probably from paralysis of the vagus. Sudden death from cardiac\
paralysis or from cardiac spasm is not uncommon.\
\
The respiration is affected in so far as the spasms of the respiratory\
muscles produce dyspnoea, and a feeling of impending suffocation which\
adds to the horrors of the disease.\
\
One of the most constant symptoms is a copious perspiration, the patient\
being literally bathed in sweat. The urine is diminished in quantity,\
but as a rule is normal in composition; as in other acute infective\
conditions, albumen and blood may be present. Retention of urine may\
result from spasm of the urethral muscles, and necessitate the use of\
the catheter.\
\
The fits may cease some time before death, or, on the other hand, death\
may occur during a paroxysm from fixation of the diaphragm and arrest of\
respiration.\
\
_Differential Diagnosis._--There is little difficulty, as a rule, in\
diagnosing a case of fulminating tetanus, but there are several\
conditions with which it may occasionally be confused. In _strychnin\
poisoning_, for example, the spasms come on immediately after the\
patient has taken a toxic dose of the drug; they are clonic in\
character, but the muscles are relaxed between the fits. If the dose is\
not lethal, the spasms soon cease. In _hydrophobia_ a history of having\
been bitten by a rabid animal is usually forthcoming; the spasms, which\
are clonic in character, affect chiefly the muscles of respiration and\
deglutition, and pass off entirely in the intervals between attacks.\
Certain cases of _haemorrhage into the lateral ventricles_ of the brain\
also simulate tetanus, but an analysis of the symptoms will prevent\
errors in diagnosis. _Cerebro-spinal meningitis_ and _basal meningitis_\
present certain superficial resemblances to tetanus, but there is no\
trismus, and the spasms chiefly affect the muscles of the neck and\
back. _Hysteria and catalepsy_ may assume characters resembling those\
of tetanus, but there is little difficulty in distinguishing between\
these diseases. Lastly, in the _tetany_ of children, or that following\
operations on the thyreoid gland, the spasms are of a jerking character,\
affect chiefly the hands and fingers, and yield to medicinal treatment.\
\
#Chronic Tetanus.#--The difference between this and acute tetanus is\
mainly one of degree. Its incubation period is longer, it is more slow\
and insidious in its progress, and it never reaches the same degree of\
severity. Trismus is the most marked and constant form of spasm; and\
while the trunk muscles may be involved, those of respiration as a rule\
escape. Every additional day the patient lives adds to the probability\
of his ultimate recovery. When the disease does prove fatal, it is from\
exhaustion, and not from respiratory or cardiac spasm. The usual\
duration is from six to ten weeks.\
\
#Delayed Tetanus.#--During the European War acute tetanus occasionally\
developed many weeks or even months after a patient had been injured,\
and when the original wound had completely healed. It usually followed\
some secondary operation, _e.g._, for the removal of a foreign body, or\
the breaking down of adhesions, which aroused latent organisms.\
\
#Local Tetanus.#--This term is applied to a form of the disease in which\
the hypertonus and spasms are localised to the muscles in the vicinity\
of the wound. It usually occurs in patients who have had prophylactic\
injections of anti-tetanic serum, the toxins entering the blood being\
probably neutralised by the antibodies in circulation, while those\
passing along the motor nerves are unaffected.\
\
When it occurs in the _limbs_, attention is usually directed to the fact\
by pain accompanying the spasms; the muscles are found to be hard and\
there are frequent twitchings of the limb. A characteristic reflex is\
present in the lower extremity, namely, extension of the foot and leg\
when the sole is tickled.\
\
_Cephalic Tetanus_ is another localised variety which follows injury in\
the distribution of the facial nerve. It is characterised by the\
occurrence on the same side as the injury, of facial spasm, rapidly\
followed by more or less complete paralysis of the muscles of\
expression, with unilateral trismus and difficulty in swallowing. Other\
cranial nerves, particularly the oculomotor and the hypoglossal, may\
also be implicated. A remarkable feature of this condition is that\
although the muscles are irresponsive to ordinary physiological stimuli,\
they are thrown into spasm by the abnormal impulses of tetanus.\
\
_Trismus._--This term is used to denote a form of tetanic spasm limited\
to the muscles of mastication. It is really a mild form of chronic\
tetanus, and the prognosis is favourable. It must not be confused with\
the fixation of the jaw sometimes associated with a wisdom-tooth\
gumboil, with tonsillitis, or with affections of the temporo-mandibular\
articulation.\
\
_Tetanus neonatorum_ is a form of tetanus occurring in infants of about\
a week old. Infection takes place through the umbilicus, and manifests\
itself clinically by spasms of the muscles of mastication. It is almost\
invariably fatal within a few days.\
\
_Prophylaxis._--Experience in the European War has established the\
fact that the routine injection of anti-tetanic serum to all patients\
with lacerated and contaminated wounds greatly reduces the frequency of\
tetanus. The sooner the serum is given after the injury, the more\
certain is its effect; within twenty-four hours 1500 units injected\
subcutaneously is sufficient for the initial dose; if a longer period\
has elapsed, 2000 to 3000 units should be given intra-muscularly, as\
this ensures more rapid absorption. A second injection is given a week\
after the first.\
\
The wound must be purified in the usual way, and all instruments and\
appliances used for operations on tetanic patients must be immediately\
sterilised by prolonged boiling.\
\
_Treatment._--When tetanus has developed the main indications are to\
prevent the further production of toxins in the wound, and to neutralise\
those that have been absorbed into the nervous system. Thorough\
purification with antiseptics, excision of devitalised tissues, and\
drainage of the wound are first carried out. To arrest the absorption of\
toxins intra-muscular injections of 10,000 units of serum are given\
daily into the muscles of the affected limb, or directly into the nerve\
trunks leading from the focus of infection, in the hope of "blocking"\
the nerves with antitoxin and so preventing the passage of toxins\
towards the spinal cord.\
\
To neutralise the toxins that have already reached the spinal cord, 5000\
units should be injected intra-thecally daily for four or five days, the\
foot of the bed being raised to enable the serum to reach the upper\
parts of the cord.\
\
The quantity of toxin circulating in the blood is so small as to be\
practically negligible, and the risk of anaphylactic shock attending\
intra-venous injection outweighs any benefit likely to follow this\
procedure.\
\
Baccelli recommends the injection of 20 c.c. of a 1 in 100 solution of\
carbolic acid into the subcutaneous tissues every four hours during the\
period that the contractions persist. Opinions vary as to the\
efficiency of this treatment. The intra-thecal injection of 10 c.c. of a\
15 per cent. solution of magnesium sulphate has proved beneficial in\
alleviating the severity of the spasms, but does not appear to have a\
curative effect.\
\
To conserve the patient's strength by preventing or diminishing the\
severity of the spasms, he should be placed in a quiet room, and every\
form of disturbance avoided. Sedatives, such as bromides, paraldehyde,\
or opium, must be given in large doses. Chloral is perhaps the best, and\
the patient should rarely have less than 150 grains in twenty-four\
hours. When he is unable to swallow, it should be given by the rectum.\
The administration of chloroform is of value in conserving the strength\
of the patient, by abolishing the spasms, and enabling the attendants to\
administer nourishment or drugs either through a stomach tube or by the\
rectum. Extreme elevation of temperature is met by tepid sponging. It is\
necessary to use the catheter if retention of urine occurs.\
\
\
HYDROPHOBIA\
\
Hydrophobia is an acute infective disease following on the bite of a\
rabid animal. It most commonly follows the bite or lick of a rabid dog\
or cat. The virus appears to be communicated through the saliva of the\
animal, and to show a marked affinity for nerve tissues; and the disease\
is most likely to develop when the patient is infected on the face or\
other uncovered part, or in a part richly endowed with nerves.\
\
A dog which has bitten a person should on no account be killed until its\
condition has been proved one way or the other. Should rabies develop\
and its destruction become necessary, the head and spinal cord should be\
retained and forwarded, packed in ice, to a competent observer. Much\
anxiety to the person bitten and to his friends would be avoided if\
these rules were observed, because in many cases it will be shown that\
the animal did not after all suffer from rabies, and that the patient\
consequently runs no risk. If, on the other hand, rabies is proved to be\
present, the patient should be submitted to the Pasteur treatment.\
\
_Clinical Features._--There is almost always a history of the patient\
having been bitten or licked by an animal supposed to suffer from\
rabies. The incubation period averages about forty days, but varies from\
a fortnight to seven or eight months, and is shorter in young than in\
old persons. The original wound has long since healed, and beyond a\
slight itchiness or pain shooting along the nerves of the part, shows no\
sign of disturbance. A few days of general malaise, with chills and\
giddiness precede the onset of the acute manifestations, which affect\
chiefly the muscles of deglutition and respiration. One of the earliest\
signs is that the patient has periodically a sudden catch in his\
breathing "resembling what often occurs when a person goes into a cold\
bath." This is due to spasm of the diaphragm, and is frequently\
accompanied by a loud-sounding hiccough, likened by the laity to the\
barking of a dog. Difficulty in swallowing fluids may be the first\
symptom.\
\
The spasms rapidly spread to all the muscles of deglutition and\
respiration, so that the patient not only has the greatest difficulty in\
swallowing, but has a constant sense of impending suffocation. To add to\
his distress, a copious secretion of viscid saliva fills his mouth. Any\
voluntary effort, as well as all forms of external stimuli, only serve\
to aggravate the spasms which are always induced by the attempt to\
swallow fluid, or even by the sound of running water.\
\
The temperature is raised; the pulse is small, rapid, and intermittent;\
and the urine may contain sugar and albumen.\
\
The mind may remain clear to the end, or the patient may have delusions,\
supposing himself to be surrounded by terrifying forms. There is always\
extreme mental agitation and despair, and the sufferer is in constant\
fear of his impending fate. Happily the inevitable issue is not long\
delayed, death usually occurring in from two to four days from the\
onset. The symptoms of the disease are so characteristic that there is\
no difficulty in diagnosis. The only condition with which it is liable\
to be confused is the variety of cephalic tetanus in which the muscles\
of deglutition are specially involved--the so-called tetanus\
hydrophobicus.\
\
_Prophylaxis._--The bite of an animal suspected of being rabid should be\
cauterised at once by means of the actual or Paquelin cautery, or by a\
strong chemical escharotic such as pure carbolic acid, after which\
antiseptic dressings are applied.\
\
It is, however, to Pasteur's _preventive inoculation_ that we must look\
for our best hope of averting the onset of symptoms. "It may now be\
taken as established that a grave responsibility rests on those\
concerned if a person bitten by a mad animal is not subjected to the\
Pasteur treatment" (Muir and Ritchie).\
\
This method is based on the fact that the long incubation period of the\
disease admits of the patient being inoculated with a modified virus\
producing a mild attack, which protects him from the natural disease.\
\
_Treatment._--When the symptoms have once developed they can only be\
palliated. The patient must be kept absolutely quiet and free from all\
sources of irritation. The spasms may be diminished by means of chloral\
and bromides, or by chloroform inhalation.\
\
\
ANTHRAX\
\
Anthrax is a comparatively rare disease, communicable to man from\
certain of the lower animals, such as sheep, oxen, horses, deer, and\
other herbivora. In animals it is characterised by symptoms of acute\
general poisoning, and, from the fact that it produces a marked\
enlargement of the spleen, is known in veterinary surgery as "splenic\
fever."\
\
The _bacillus anthracis_ (Fig. 27), the largest of the known pathogenic\
bacteria, occurs in groups or in chains made up of numerous bacilli,\
each bacillus measuring from 6 to 8 u in length. The organisms are found\
in enormous numbers throughout the bodies of animals that have died of\
anthrax, and are readily recognised and cultivated. Sporulation only\
takes place outside the body, probably because free oxygen is necessary\
to the process. In the spore-free condition, the organisms are readily\
destroyed by ordinary germicides, and by the gastric juice. The spores,\
on the other hand, have a high degree of resistance. Not only do they\
remain viable in the dry state for long periods, even up to a year, but\
they survive boiling for five minutes, and must be subjected to dry heat\
at 140 o C. for several hours before they are destroyed.\
\
[Illustration: FIG. 27.--Bacillus of Anthrax in section of skin, from a\
case of malignant pustule; shows vesicle containing bacilli. x 400 diam.\
Gram's stain.]\
\
_Clinical Varieties of Anthrax._--In man, anthrax may manifest itself in\
one of three clinical forms.\
\
It may be transmitted by means of spores or bacilli directly from a\
diseased animal to those who, by their occupation or otherwise, are\
brought into contact with it--for example, shepherds, butchers,\
veterinary surgeons, or hide-porters. Infection may occur on the face by\
the use of a shaving-brush contaminated by spores. The path of infection\
is usually through an abrasion of the skin, and the primary\
manifestations are local, constituting what is known as _the malignant\
pustule_.\
\
In other cases the disease is contracted through the inhalation of the\
dried spores into the respiratory passages. This occurs oftenest in\
those who work amongst wool, fur, and rags, and a form of acute\
pneumonia of great virulence ensues. This affection is known as\
_wool-sorter's disease_, and is almost universally fatal.\
\
There is reason to believe that infection may also take place by means\
of spores ingested into the alimentary canal in meat or milk derived\
from diseased animals, or in infected water.\
\
#Clinical Features of Malignant Pustule.#--We shall here confine\
ourselves to the consideration of the local lesion as it occurs in the\
skin--_the malignant pustule_.\
\
The point of infection is usually on an uncovered part of the body, such\
as the face, hands, arms, or back of the neck, and the wound may be\
exceedingly minute. After an incubation period varying from a few hours\
to several days, a reddish nodule resembling a small boil appears at the\
seat of inoculation, the immediately surrounding skin becomes swollen\
and indurated, and over the indurated area there appear a number of\
small vesicles containing serum, which at first is clear but soon\
becomes blood-stained (Fig. 28). Coincidently the subcutaneous tissue\
for a considerable distance around becomes markedly oedematous, and the\
skin red and tense. Within a few hours, blood is extravasated in the\
centre of the indurated area, the blisters burst, and a dark brown or\
black eschar, composed of necrosed skin and subcutaneous tissue and\
altered blood, forms (Fig. 29). Meanwhile the induration extends, fresh\
vesicles form and in turn burst, and the eschar increases in size. The\
neighbouring lymph glands soon become swollen and tender. The affected\
part is hot and itchy, but the patient does not complain of great pain.\
There is a moderate degree of constitutional disturbance, with headache,\
nausea, and sometimes shivering.\
\
If the infection becomes generalised--_anthracaemia_--the temperature\
rises to 103 o or 104 o F., the pulse becomes feeble and rapid, and other\
signs of severe blood-poisoning appear: vomiting, diarrhoea, pains in the\
limbs, headache and delirium, and the condition proves fatal in from\
five to eight days.\
\
_Differential Diagnosis._--When the malignant pustule is fully\
developed, the central slough with the surrounding vesicles and the\
widespread oedema are characteristic. The bacillus can be obtained from\
the peripheral portion of the slough, from the blisters, and from the\
adjacent lymph vessels and glands. The occupation of the patient may\
suggest the possibility of anthrax infection.\
\
[Illustration: FIG. 28.--Malignant Pustule, third day after infection\
with Anthrax, showing great oedema of upper extremity and pectoral region\
(cf. Fig. 29).]\
\
[Illustration: FIG. 29.--Malignant Pustule, fourteen days after\
infection, showing black eschar in process of separation. The oedema has\
largely disappeared. Treated by Sclavo's serum (cf. Fig. 28).]\
\
_Prophylaxis._--Any wound suspected of being infected with anthrax\
should at once be cauterised with caustic potash, the actual cautery, or\
pure carbolic acid.\
\
_Treatment._--The best results hitherto obtained have followed the use\
of the anti-anthrax serum introduced by Sclavo. The initial dose is 40\
c.c., and if the serum is given early in the disease, the beneficial\
effects are manifest in a few hours. Favourable results have also\
followed the use of pyocyanase, a vaccine prepared from the bacillus\
pyocyaneus.\
\
By some it is recommended that the local lesion should be freely\
excised; others advocate cauterisation of the affected part with solid\
caustic potash till all the indurated area is softened. Graf has had\
excellent results by the latter method in a large series of cases, the\
oedema subsiding in about twenty-four hours and the constitutional\
symptoms rapidly improving. Wolff and Wiewiorowski, on the other hand,\
have had equally good results by simply protecting the local lesion with\
a mild antiseptic dressing, and relying upon general treatment.\
\
The general treatment consists in feeding and stimulating the patient as\
freely as possible. Quinine, in 5 to 10 grain doses every four hours,\
and powdered ipecacuanha, in 40 to 60 grain doses every four hours, have\
also been employed with apparent benefit.\
\
\
GLANDERS\
\
Glanders is due to the action of a specific bacterium, the _bacillus\
mallei_, which resembles the tubercle bacillus, save that it is somewhat\
shorter and broader, and does not stain by Gram's method. It requires\
higher temperatures for its cultivation than the tubercle bacillus, and\
its growth on potato is of a characteristic chocolate-brown colour, with\
a greenish-yellow ring at the margin of the growth. The bacillus mallei\
retains its vitality for long periods under ordinary conditions, but is\
readily killed by heat and chemical agents. It does not form spores.\
\
_Clinical Features._--Both in the lower animals and in man the bacillus\
gives rise to two distinct types of disease--_acute glanders_, and\
_chronic glanders_ or _farcy_.\
\
Acute Glanders is most commonly met with in the horse and in other\
equine animals, horned cattle being immune. It affects the septum of the\
nose and adjacent parts, firm, translucent, greyish nodules containing\
lymphoid and epithelioid cells appearing in the mucous membrane. These\
nodules subsequently break down in the centre, forming irregular\
ulcers, which are attended with profuse discharge, and marked\
inflammatory swelling. The cervical lymph glands, as well as the lungs,\
spleen, and liver, may be the seat of secondary nodules.\
\
_In man_, acute glanders is commoner than the chronic variety. Infection\
always takes place through an abraded surface, and usually on one of the\
uncovered parts of the body--most commonly the skin of the hands, arms,\
or face; or on the mucous membrane of the mouth, nose, or eye. The\
disease has been acquired by accidental inoculation in the course of\
experimental investigations in the laboratory, and proved fatal. The\
incubation period is from three to five days.\
\
The _local_ manifestations are pain and swelling in the region of the\
infected wound, with inflammatory redness around it and along the lines\
of the superficial lymphatics. In the course of a week, small, firm\
nodules appear, and are rapidly transformed into pustules. These may\
occur on the face and in the vicinity of joints, and may be mistaken for\
the eruption of small-pox.\
\
After breaking down, these pustules give rise to irregular ulcers, which\
by their confluence lead to extensive destruction of skin. Sometimes the\
nasal mucous membrane becomes affected, and produces a discharge--at\
first watery, but later sanious and purulent. Necrosis of the bones of\
the nose may take place, in which case the discharge becomes peculiarly\
offensive. In nearly every case metastatic abscesses form in different\
parts of the body, such as the lungs, joints, or muscles.\
\
During the development of the disease the patient feels ill, complains\
of headache and pains in the limbs, the temperature rises to 104 o or\
even to 106 o F., and assumes a pyaemic type. The pulse becomes rapid and\
weak. The tongue is dry and brown. There is profuse sweating,\
albuminuria, and often insomnia with delirium. Death may take place\
within a week, but more frequently occurs during the second or third\
week.\
\
_Differential Diagnosis._--There is nothing characteristic in the site\
of the primary lesion in man, and the condition may, during the early\
stages, be mistaken for a boil or carbuncle, or for any acute\
inflammatory condition. Later, the disease may simulate acute articular\
rheumatism, or may manifest all the symptoms of acute septicaemia or\
pyaemia. The diagnosis is established by the recognition of the bacillus.\
Veterinary surgeons attach great importance to the mallein test as a\
means of diagnosis in animals, but in the human subject its use is\
attended with considerable risk and is not to be recommended.\
\
_Treatment._--Excision of the primary nodule, followed by the\
application of the thermo-cautery and sponging with pure carbolic acid,\
should be carried out, provided the condition is sufficiently limited to\
render complete removal practicable.\
\
When secondary abscesses form in accessible situations, they must be\
incised, disinfected, and drained. The general treatment is carried out\
on the same lines as in other acute infective diseases.\
\
#Chronic Glanders.#--_In the horse_ the chronic form of glanders is\
known as _farcy_, and follows infection through an abrasion of the skin,\
involving chiefly the superficial lymph vessels and glands. The\
lymphatics become indurated and nodular, constituting what veterinarians\
call _farcy pipes_ and _farcy buds_.\
\
_In man_ also the clinical features of the chronic variety of the\
disease are somewhat different from those of the acute form. Here, too,\
infection takes place through a broken cutaneous surface, and leads to a\
superficial lymphangitis with nodular thickening of the lymphatics\
(_farcy buds_). The neighbouring glands soon become swollen and\
indurated. The primary lesion meanwhile inflames, suppurates, and, after\
breaking down, leaves a large, irregular ulcer with thickened edges and\
a foul, purulent or bloody discharge. The glands break down in the same\
way, and lead to wide destruction of skin, and the resulting sinuses and\
ulcers are exceedingly intractable. Secondary deposits in the\
subcutaneous tissue, the muscles, and other parts, are not uncommon, and\
the nasal mucous membrane may become involved. The disease often runs a\
chronic course, extending to four or five months, or even longer.\
Recovery takes place in about 50 per cent. of cases, but the\
convalescence is prolonged, and at any time the disease may assume the\
characters of the acute variety and speedily prove fatal.\
\
The _differential diagnosis_ is often difficult, especially in the\
chronic nodules, in which it may be impossible to demonstrate the\
bacillus. The ulcerated lesions of farcy have to be distinguished from\
those of tubercle, syphilis, and other forms of infective granuloma.\
\
_Treatment._--Limited areas of disease should be completely excised. The\
general condition of the patient must be improved by tonics, good food,\
and favourable hygienic surroundings. In some cases potassium iodide\
acts beneficially.\
\
\
ACTINOMYCOSIS\
\
Actinomycosis is a chronic disease due to the action of an organism\
somewhat higher in the vegetable scale than ordinary bacteria--the\
_streptothrix actinomyces_ or _ray fungus_.\
\
[Illustration: FIG. 30.--Section of Actinomycosis Colony in Pus from\
Abscess of Liver, showing filaments and clubs of streptothrix\
actinomyces. x 400 diam. Gram's stain.]\
\
_Etiology and Morbid Anatomy._--The actinomyces, which has never been\
met with outside the body, gives rise in oxen, horses, and other animals\
to tumour-like masses composed of granulation tissue; and in man to\
chronic suppurative processes which may result in a condition resembling\
chronic pyaemia. The actinomyces is more complex in structure than other\
pathogenic organisms, and occurs in the tissues in the form of small,\
round, semi-translucent bodies, about the size of a pin-head or less,\
and consisting of colonies of the fungus. On account of their yellow\
tint they are spoken of as "sulphur grains." Each colony is made up of a\
series of thin, interlacing, and branching _filaments_, some of which\
are broken up so as to form masses or chains of _cocci_; and around the\
periphery of the colony are elongated, pear-shaped, hyaline, _club-like\
bodies_ (Fig. 30).\
\
Infection is believed to be conveyed by the husks of cereals, especially\
barley; and the organism has been found adhering to particles of grain\
embedded in the tissues of animals suffering from the disease. In the\
human subject there is often a history of exposure to infection from\
such sources, and the disease is said to be most common during the\
harvesting months.\
\
Around each colony of actinomyces is a zone of granulation tissue in\
which suppuration usually occurs, so that the fungus comes to lie in a\
bath of greenish-yellow pus. As the process spreads these purulent foci\
become confluent and form abscess cavities. When metastasis takes place,\
as it occasionally does, the fungus is transmitted by the blood vessels,\
as in pyaemia.\
\
_Clinical features._--In man the disease may be met with in the skin,\
the organisms gaining access through an abrasion, and spreading by the\
formation of new nodules in the same way as tuberculosis.\
\
The region of the mouth and jaws is one of the commonest sites of\
surgical actinomycosis. Infection takes place, as a rule, along the side\
of a carious tooth, and spreads to the lower jaw. A swelling is slowly\
and insidiously developed, but when the loose connective tissue of the\
neck becomes infiltrated, the spread is more rapid. The whole region\
becomes infiltrated and swollen, and the skin ultimately gives way and\
free suppuration occurs, resulting in the formation of sinuses. The\
characteristic greenish-grey or yellow granules are seen in the pus, and\
when examined microscopically reveal the colonies of actinomyces.\
\
Less frequently the maxilla becomes affected, and the disease may spread\
to the base of the skull and brain. The vertebrae may become involved by\
infection taking place through the pharynx or oesophagus, and leading to\
a condition simulating tuberculous disease of the spine. When it\
implicates the intestinal canal and its accessory glands, the lungs,\
pleura, and bronchial tubes, or the brain, the disease is not amenable\
to surgical treatment.\
\
_Differential Diagnosis._--The conditions likely to be mistaken for\
surgical actinomycosis are sarcoma, tubercle, and syphilis. In the early\
stages the differential diagnosis is exceedingly difficult. In many\
cases it is only possible when suppuration has occurred and the fungus\
can be demonstrated.\
\
The slow destruction of the affected tissue by suppuration, the absence\
of pain, tenderness, and redness, simulate tuberculosis, but the absence\
of glandular involvement helps to distinguish it.\
\
Syphilitic lesions are liable to be mistaken for actinomycosis, all the\
more that in both diseases improvement follows the administration of\
iodides. When it affects the lower jaw, in its early stages,\
actinomycosis may closely simulate a periosteal sarcoma.\
\
[Illustration: FIG. 31.--Actinomycosis of Maxilla. The disease spread to\
opposite side; finally implicated base of skull, and proved fatal.\
Treated by radium.\
\
(Mr. D. P. D. Wilkie's case.)]\
\
The recognition of the fungus is the crucial point in diagnosis.\
\
_Prognosis._--Spontaneous cure rarely occurs. When the disease\
implicates internal organs, it is almost always fatal. On external parts\
the destructive process gradually spreads, and the patient eventually\
succumbs to superadded septic infection. When, from its situation, the\
primary focus admits of removal, the prognosis is more favourable.\
\
_Treatment._--The surgical treatment is early and free removal of the\
affected tissues, after which the wound is cauterised by the actual\
cautery, and sponged over with pure carbolic acid. The cavity is packed\
with iodoform gauze, no attempt being made to close the wound.\
\
Success has attended the use of a vaccine prepared from cultures of the\
organism; and the X-rays and radium, combined with the administration of\
iodides in large doses, or with intra-muscular injections of a 10 per\
cent. solution of cacodylate of soda, have proved of benefit.\
\
MYCETOMA, OR MADURA FOOT.--Mycetoma is a chronic disease due to\
an organism resembling that of actinomycosis, but not identical with it.\
It is endemic in certain tropical countries, and is most frequently met\
with in India. Infection takes place through an abrasion of the skin,\
and the disease usually occurs on the feet of adult males who work\
barefooted in the fields.\
\
_Clinical Features._--The disease begins on the foot as an indurated\
patch, which becomes discoloured and permeated by black or yellow\
nodules containing the organism. These nodules break down by\
suppuration, and numerous minute abscesses lined by granulation tissues\
are thus formed. In the pus are found yellow particles likened to\
fish-roe, or black pigmented granules like gunpowder. Sinuses form, and\
the whole foot becomes greatly swollen and distorted by flattening of\
the sole and dorsiflexion of the toes. Areas of caries or necrosis occur\
in the bones, and the disease gradually extends up the leg (Fig. 32).\
There is but little pain, and no glandular involvement or constitutional\
disturbance. The disease runs a prolonged course, sometimes lasting for\
twenty or thirty years. Spontaneous cure never takes place, and the risk\
to life is that of prolonged suppuration.\
\
If the disease is localised, it may be removed by the knife or sharp\
spoon, and the part afterwards cauterised. As a rule, amputation well\
above the disease is the best line of treatment. Unlike actinomycosis,\
this disease does not appear to be benefited by iodides.\
\
[Illustration: FIG. 32.--Mycetoma, or Madura Foot. (Museum of Royal\
College of Surgeons, Edinburgh.)]\
\
DELHI BOIL.--_Synonyms_--Aleppo boil, Biskra button, Furunculus\
orientalis, Natal sore.\
\
Delhi boil is a chronic inflammatory disease, most commonly met with in\
India, especially towards the end of the wet season. The disease occurs\
oftenest on the face, and is believed to be due to an organism, although\
this has not been demonstrated. The infection is supposed to be conveyed\
through water used for washing, or by the bites of insects.\
\
_Clinical Features._--A red spot, resembling the mark of a mosquito\
bite, appears on the affected part, and is attended with itching. After\
becoming papular and increasing to the size of a pea, desquamation takes\
place, leaving a dull-red surface, over which in the course of several\
weeks there develops a series of small yellowish-white spots, from which\
serum exudes, and, drying, forms a thick scab. Under this scab the skin\
ulcerates, leaving small oval sores with sharply bevelled edges, and an\
uneven floor covered with yellow or sanious pus. These sores vary in\
number from one to forty or fifty. They may last for months and then\
heal spontaneously, or may continue to spread until arrested by suitable\
treatment. There is no enlargement of adjacent glands, and but little\
inflammatory reaction in the surrounding tissues; nor is there any\
marked constitutional disturbance. Recovery is often followed by\
cicatricial contraction leading to deformity of the face.\
\
The _treatment_ consists in destroying the original papule by the actual\
cautery, acid nitrate of mercury, or pure carbolic acid. The ulcers\
should be scraped with the sharp spoon, and cauterised.\
\
CHIGOE.--Chigoe or jigger results from the introduction of the\
eggs of the sand-flea (_Pulex penetrans_) into the tissues. It occurs in\
tropical Africa, South America, and the West Indies. The impregnated\
female flea remains attached to the part till the eggs mature, when by\
their irritation they cause localised inflammation with pustules or\
vesicles on the surface. Children are most commonly attacked,\
particularly about the toe-nails and on the scrotum. The treatment\
consists in picking out the insect with a blunt needle, special care\
being taken not to break it up. The puncture is then cauterised. The\
application of essential oils to the feet acts as a preventive.\
\
POISONING BY INSECTS.--The bites of certain insects, such as\
mosquitoes, midges, different varieties of flies, wasps, and spiders,\
may be followed by serious complications. The effects are mainly due to\
the injection of an irritant acid secretion, the exact nature of which\
has not been ascertained.\
\
The local lesion is a puncture, surrounded by a zone of hyperaemia,\
wheals, or vesicles, and is associated with burning sensations and\
itching which usually pass off in a few hours, but may recur at\
intervals, especially when the patient is warm in bed. Scratching also\
reproduces the local signs and symptoms. Where the connective tissue is\
loose--for example, in the eyelid or scrotum--there is often\
considerable swelling; and in the mouth and fauces this may lead to\
oedema of the glottis, which may prove fatal.\
\
The _treatment_ consists in the local application of dilute alkalies\
such as ammonia water, solutions of carbonate or bicarbonate of soda, or\
sal-volatile. Weak carbolic lotions, or lead and opium lotion, are\
useful in allaying the local irritation. One of the best means of\
neutralising the poison is to apply to the sting a drop of a mixture\
containing equal parts of pure carbolic acid and liquor ammoniae.\
\
Free stimulation is called for when severe constitutional symptoms are\
present.\
\
SNAKE-BITES.--We are here only concerned with the injuries\
inflicted by the venomous varieties of snakes, the most important of\
which are the hooded snakes of India, the rattle-snakes of America, the\
horned snakes of Africa, the viper of Europe, and the adder of the\
United Kingdom.\
\
While the virulence of these creatures varies widely, they are all\
capable of producing in a greater or less degree symptoms of acute\
poisoning in man and other animals. By means of two recurved fangs\
attached to the upper jaw, and connected by a duct with poison-secreting\
glands, they introduce into their prey a thick, transparent, yellowish\
fluid, of acid reaction, probably of the nature of an albumose, and\
known as the _venom_.\
\
The _clinical features_ resulting from the injection of the venom vary\
directly in intensity with the amount of the poison introduced, and the\
rapidity with which it reaches the circulating blood, being most marked\
when it immediately enters a large vein. The poison is innocuous when\
taken into the stomach.\
\
_Locally_ the snake inflicts a double wound, passing vertically into the\
subcutaneous tissue; the edges of the punctures are ecchymosed, and the\
adjacent vessels the seat of thrombosis. Immediately there is intense\
pain, and considerable swelling with congestion, which tends to spread\
towards the trunk. Extensive gangrene may ensue. There is no special\
involvement of the lymphatics.\
\
The _general symptoms_ may come on at once if the snake is a\
particularly venomous one, or not for some hours if less virulent. In\
the majority of viper or adder bites the constitutional disturbance is\
slight and transient, if it appears at all. Snake-bites in children are\
particularly dangerous.\
\
The patient's condition is one of profound shock with faintness,\
giddiness, dimness of sight, and a feeling of great terror. The pupils\
dilate, the skin becomes moist with a clammy sweat, and nausea with\
vomiting, sometimes of blood, ensues. High fever, cramps, loss of\
sensation, haematuria, and melaena are among the other symptoms that may\
be present. The pulse becomes feeble and rapid, the respiratory nerve\
centres are profoundly depressed, and delirium followed by coma usually\
precedes the fatal issue, which may take place in from five to\
forty-eight hours. If the patient survives for two days the prognosis is\
favourable.\
\
_Treatment._--A broad ligature should be tied tightly round the limb\
above the seat of infection, to prevent the poison passing into the\
general circulation, and bleeding from the wound should be encouraged.\
The application of an elastic bandage from above downward to empty the\
blood out of the infected portion of the limb has been recommended. The\
whole of the bite should at once be excised, and crystals of\
permanganate of potash rubbed into the wound until it is black, or\
peroxide of hydrogen applied with the object of destroying the poison by\
oxidation.\
\
The general treatment consists in free stimulation with whisky, brandy,\
ammonia, digitalis, etc. Hypodermic injections of strychnin in doses\
sufficiently large to produce a slight degree of poisoning by the drug\
are particularly useful. The most rational treatment, when it is\
available, is the use of the _antivenin_ introduced by Fraser and\
Calmette.\
\
\
\
\
CHAPTER VIII\
\
TUBERCULOSIS\
\
\
Tubercle bacillus--Methods of infection--Inherited and acquired\
    predisposition--Relationship of tuberculosis to injury--Human and\
    bovine tuberculosis--Action of the bacillus upon the\
    tissues--Tuberculous granulation tissue--Natural cure--Recrudescence\
    of the disease--THE TUBERCULOUS ABSCESS--Contents and wall of the\
    abscess--Tuberculous sinuses.\
\
Tuberculosis occurs more frequently in some situations than in others;\
it is common, for example, in lymph glands, in bones and joints, in the\
peritoneum, the intestine, the kidney, prostate and testis, and in the\
skin and subcutaneous cellular tissue; it is seldom met with in the\
breast or in muscles, and it rarely affects the ovary, the pancreas, the\
parotid, or the thyreoid.\
\
_Tubercle bacilli_ vary widely in their virulence, and they are more\
tenacious of life than the common pyogenic bacteria. In a dry state, for\
example, they can retain their vitality for months; and they can also\
survive immersion in water for prolonged periods. They resist the action\
of the products of putrefaction for a considerable time, and are not\
destroyed by digestive processes in the stomach and intestine. They may\
be killed in a few minutes by boiling, or by exposure to steam under\
pressure, or by immersion for less than a minute in 1 in 20 carbolic\
lotion.\
\
#Methods of Infection.#--In marked contrast to what obtains in the\
infective diseases that have already been described, tuberculosis rarely\
results from the _infection of a wound_. In exceptional instances,\
however, this does occur, and in illustration of the fact may be cited\
the case of a servant who cut her finger with a broken spittoon\
containing the sputum of her consumptive master; the wound subsequently\
showed evidence of tuberculous infection, which ultimately spread up\
along the lymph vessels of the arm. Pathologists, too, whose hands,\
before the days of rubber gloves, were frequently exposed to the contact\
of tuberculous tissues and pus, were liable to suffer from a form of\
tuberculosis of the skin of the finger, known as _anatomical tubercle_.\
Slight wounds of the feet in children who go about barefoot in towns\
sometimes become infected with tubercle. Operation wounds made with\
instruments contaminated with tuberculous material have also been known\
to become infected. It is highly probable that the common form of\
tuberculosis of the skin known as "lupus" arises by direct infection\
from without.\
\
[Illustration: FIG. 33.--Tubercle Bacilli in caseous material\
x 1000 diam. Z. Neilsen stain.]\
\
In the vast majority of cases the tubercle bacillus gains entrance to\
the body by way of the mucous surfaces, the organisms being either\
inhaled or swallowed; those inhaled are mostly derived from the human\
subject, those swallowed, from cattle. Bacilli, whether inhaled or\
swallowed, are especially apt to lodge about the pharynx and pass to the\
pharyngeal lymphoid tissue and tonsils, and by way of the lymph vessels\
to the glands. The glands most frequently infected in this way are the\
cervical glands, and those within the cavity of the chest--particularly\
the bronchial glands at the root of the lung. From these, infection\
extends at any later period in life to the bones, joints, and internal\
organs.\
\
There is reason to believe that the organisms may lie in a dormant\
condition for an indefinite period in these glands, and only become\
active long afterwards, when some depression of the patient's health\
produces conditions which favour their growth. When the organisms become\
active in this way, the tuberculous tissue undergoes softening and\
disintegration, and the infective material, by bursting into an adjacent\
vein, may enter the blood-stream, in which it is carried to distant\
parts of the body. In this way a _general tuberculosis_ may be set up,\
or localised foci of tuberculosis may develop in the tissues in which\
the organisms lodge. Many tuberculous patients are to be regarded as\
possessing in their bronchial glands, or elsewhere, an internal store of\
bacilli, to which the disease for which advice is sought owes its\
origin, and from which similar outbreaks of tuberculosis may originate\
in the future.\
\
_The alimentary mucous membrane_, especially that of the lower ileum and\
caecum, is exposed to infection by swallowed sputum and by food\
materials, such as milk, containing tubercle bacilli. The organisms may\
lodge in the mucous membrane and cause tuberculous ulceration, or they\
may be carried through the wall of the bowel into the lacteals, along\
which they pass to the mesenteric glands where they become arrested and\
give rise to tuberculous disease.\
\
#Relationship of Tuberculosis to Trauma.#--Any tissue whose vitality has\
been lowered by injury or disease furnishes a favourable nidus for the\
lodgment and growth of tubercle bacilli. The injury or disease, however,\
is to be looked upon as determining the _localisation_ of the\
tuberculous lesion rather than as an essential factor in its causation.\
In a person, for example, in whose blood tubercle bacilli are\
circulating and reaching every tissue and organ of the body, the\
occurrence of tuberculous disease in a particular part may be determined\
by the depression of the tissues resulting from an injury of that part.\
There can be no doubt that excessive movement and jarring of a limb\
aggravates tuberculous disease of a joint; also that an injury may light\
up a focus that has been long quiescent, but we do not agree with\
those--Da Costa, for example--who maintain that injury may be a\
determining cause of tuberculosis. The question is not one of mere\
academic interest, but one that may raise important issues in the law\
courts.\
\
#Human and Bovine Tuberculosis.#--The frequency of the bovine bacillus\
in the abdominal and in the glandular and osseous tuberculous lesions of\
children would appear to justify the conclusion that the disease is\
transmissible from the ox to the human subject, and that the milk of\
tuberculous cows is probably a common vehicle of transmission.\
\
#Changes in the Tissues following upon the successful Lodgment of\
Tubercle Bacilli.#--The action of the bacilli on the tissues results in\
the formation of granulation tissue comprising characteristic tissue\
elements and with a marked tendency to undergo caseation.\
\
The recognition of the characteristic elements, with or without\
caseation, is usually sufficient evidence of the tuberculous nature of\
any portion of tissue examined for diagnostic purposes. The recognition\
of the bacillus itself by appropriate methods of staining makes the\
diagnosis a certainty; but as it is by no means easy to identify the\
organism in many forms of surgical tuberculosis, it may be necessary to\
have recourse to experimental inoculation of susceptible animals such as\
guinea-pigs.\
\
The changes subsequent to the formation of tuberculous granulation\
tissue are liable to many variations. It must always be borne in mind\
that although the bacilli have effected a lodgment and have inaugurated\
disease, the relation between them and the tissues remains one of mutual\
antagonism; which of them is to gain and keep the upper hand in the\
conflict depends on their relative powers of resistance.\
\
If the tissues prevail, there ensues a process of repair. In the\
immediate vicinity of the area of infection young connective tissue, and\
later, fibrous tissue, is formed. This may replace the tuberculous\
tissue and bring about repair--a fibrous cicatrix remaining to mark the\
scene of the previous contest. Scars of this nature are frequently\
discovered at the apex of the lung after death in persons who have at\
one time suffered from pulmonary phthisis. Under other circumstances,\
the tuberculous tissue that has undergone caseation, or even\
calcification, is only encapsulated by the new fibrous tissue, like a\
foreign body. Although this may be regarded as a victory for the\
tissues, the cure, if such it may be called, is not necessarily a\
permanent one, for at any subsequent period, if the part affected is\
disturbed by injury or through some other influence, the encapsulated\
tubercle may again become active and get the upper hand of the tissues,\
and there results a relapse or recrudescence of the disease. This\
_tendency to relapse_ after apparent cure is a notable feature of\
tuberculous disease as it is met with in the spine, or in the\
hip-joint, and it necessitates a prolonged course of treatment to give\
the best chance of a lasting cure.\
\
If, however, at the inauguration of the tuberculous disease the bacilli\
prevail, the infection tends to spread into the tissues surrounding\
those originally infected, and more and more tuberculous granulation\
tissue is formed. Finally the tuberculous tissue breaks down and\
liquefies, resulting in the formation of a cold abscess. In their\
struggle with the tissues, tubercle bacilli receive considerable support\
and assistance from any pyogenic organisms that may be present. A\
tuberculous infection may exhibit its aggressive qualities in a more\
serious manner by sending off detachments of bacilli, which are carried\
by the lymphatics to the nearest glands, or by the blood-stream to more\
distant, and it may be to all, parts of the body. When the infection is\
thus generalised, the condition is called _general tuberculosis_.\
Considering the extraordinary frequency of localised forms of surgical\
tuberculosis, general dissemination of the disease is rare.\
\
#The clinical features# of surgical tuberculosis will be described with\
the individual tissues and organs, as they vary widely according to the\
situation of the lesion.\
\
#The general treatment# consists in combating the adverse influences\
that have been mentioned as increasing the liability to tuberculous\
infection. Within recent years the value of the "open-air" treatment has\
been widely recognised. An open-air life, even in the centre of a city,\
may be followed by marked improvement, especially in the hospital class\
of patient, whose home surroundings tend to favour the progress of the\
disease. The purer air of places away from centres of population is\
still better; and, according to the idiosyncrasies of the individual\
patient, mountain air or that of the sea coast may be preferred. In view\
of the possible discomforts and gastric disturbance which may attend a\
sea-voyage, this should be recommended to patients suffering from\
tuberculous lesions with more caution than has hitherto been exercised.\
The diet must be a liberal one, and should include those articles which\
are at the same time easily digested and nourishing, especially proteids\
and fats; milk obtained from a reliable source and underdone\
butcher-meat are among the best. When the ordinary nourishment taken is\
insufficient, it may be supplemented by such articles as malt extract,\
stout, and cod-liver oil. The last is specially beneficial in patients\
who do not take enough fat in other forms. It is noteworthy that many\
tuberculous patients show an aversion to fat.\
\
For _the use of tuberculin in diagnosis_ and for _the vaccine treatment\
of tuberculosis_ the reader is referred to text-books on medicine.\
\
In addition to increasing the resisting power of the patient, it is\
important to enable the fluids of the body, so altered, to come into\
contact with the tuberculous focus. One of the obstacles to this is that\
the focus is often surrounded by tissues or fluids which have been\
almost entirely deprived of bactericidal substances. In the case of\
caseated glands in the neck, for example, it is obvious that the removal\
of this inert material is necessary before the tissues can be irrigated\
with fluids of high bactericidal value. Again, in tuberculous ascites\
the abdominal cavity is filled with a fluid practically devoid of\
anti-bacterial substances, so that the bacilli are able to thrive and\
work their will on the tissues. When the stagnant fluid is got rid of by\
laparotomy, the parts are immediately douched with lymph charged with\
protective substances, the bactericidal power of which may be many times\
that of the fluid displaced.\
\
It is probable that the beneficial influence of _counter-irritants_,\
such as blisters, and exposure to the _Finsen light_ and other forms of\
_rays_, is to be attributed in part to the increased flow of blood to\
the infected tissues.\
\
_Artificial Hyperaemia._--As has been explained, the induction of\
hyperaemia by the method devised by Bier, constitutes one of our most\
efficient means of combating bacterial infection. The treatment of\
tuberculosis on this plan has been proved by experience to be a valuable\
addition to our therapeutic measures, and the simplicity of its\
application has led to its being widely adopted in practice. It results\
in an increase in the reactive changes around the tuberculous focus, an\
increase in the immigration of leucocytes, and infiltration with the\
lymphocytes.\
\
The constricting bandage should be applied at some distance above the\
seat of infection; for instance, in disease of the wrist, it is put on\
above the elbow, and it must not cause pain either where it is applied\
or in the diseased part. The bandage is only applied for a few hours\
each day, either two hours at a time or twice a day for one hour, and,\
while it is on, all dressings are removed save a piece of sterile gauze\
over any wound or sinus that may be present. The process of cure takes a\
long time--nine or even twelve months in the case of a severe joint\
affection.\
\
In cases in which a constricting bandage is inapplicable, for example,\
in cold abscesses, tuberculous glands or tendon sheaths, Klapp's suction\
bell is employed. The cup is applied for five minutes at a time and then\
taken off for three minutes, and this is repeated over a period of\
about three-quarters of an hour. The pus is allowed to escape by a small\
incision, and no packing or drain should be introduced.\
\
It has been found that tuberculous lesions tend to undergo cure\
when the infected tissues are exposed to the rays of the\
sun--_heliotherapy_--therefore whenever practicable this therapeutic\
measure should be had recourse to.\
\
Since the introduction of the methods of treatment described above, and\
especially by their employment at an early stage in the disease, the\
number of cases of tuberculosis requiring operative interference has\
greatly diminished. There are still circumstances, however, in which an\
operation is required; for example, in disease of the lymph glands for\
the removal of inert masses of caseous material, in disease of bone for\
the removal of sequestra, or in disease of joints to improve the\
function of the limb. It is to be understood, however, that operative\
treatment must always be preceded by and combined with other therapeutic\
measures.\
\
\
TUBERCULOUS ABSCESS\
\
The caseation of tuberculous granulation tissue and its liquefaction is\
a slow and insidious process, and is unattended with the classical signs\
of inflammation--hence the terms "cold" and "chronic" applied to the\
tuberculous abscess.\
\
In a cold abscess, such as that which results from tuberculous disease\
of the vertebrae, the clinical appearances are those of a soft, fluid\
swelling without heat, redness, pain, or fever. When toxic symptoms are\
present, they are usually due to a mixed infection.\
\
A tuberculous abscess results from the disintegration and liquefaction\
of tuberculous granulation tissue which has undergone caseation. Fluid\
and cells from the adjacent blood vessels exude into the cavity, and\
lead to variations in the character of its contents. In some cases the\
contents consist of a clear amber-coloured fluid, in which are suspended\
fragments of caseated tissue; in others, of a white material like\
cream-cheese. From the addition of a sufficient number of leucocytes,\
the contents may resemble the pus of an ordinary abscess.\
\
The wall of the abscess is lined with tuberculous granulation tissue,\
the inner layers of which are undergoing caseation and disintegration,\
and present a shreddy appearance; the outer layers consist of\
tuberculous tissue which has not yet undergone caseation. The abscess\
tends to increase in size by progressive liquefaction of the inner\
layers, caseation of the outer layers, and the further invasion of the\
surrounding tissues by tubercle bacilli. In this way a tuberculous\
abscess is capable of indefinite extension and increase in size until it\
reaches a free surface and ruptures externally. The direction in which\
it spreads is influenced by the anatomical arrangement of the tissues,\
and possibly to some extent by gravity, and the abscess may reach the\
surface at a considerable distance from its seat of origin. The best\
illustration of this is seen in the psoas abscess, which may originate\
in the dorsal vertebrae, extend downwards within the sheath of the psoas\
muscle, and finally appear in the thigh.\
\
#Clinical Features.#--The insidious development of the tuberculous\
abscess is one of its characteristic features. The swelling may attain a\
considerable size without the patient being aware of its existence, and,\
as a matter of fact, it is often discovered accidentally. The absence of\
toxaemia is to be associated with the incapacity of the wall of the\
abscess to permit of absorption; this is shown also by the fact that\
when even a large quantity of iodoform is inserted into the cavity of\
the abscess, there are no symptoms of poisoning. The abscess varies in\
size from a small cherry to a cavity containing several pints of pus.\
Its shape also varies; it is usually that of a flattened sphere, but it\
may present pockets or burrows running in various directions. Sometimes\
it is hour-glass or dumb-bell shaped, as is well illustrated in the\
region of the groin in disease of the spine or pelvis, where there may\
be a large sac occupying the venter ilii, and a smaller one in the\
thigh, the two communicating by a narrow channel under Poupart's\
ligament. By pressing with the fingers the pus may be displaced from one\
compartment to the other. The usual course of events is that the abscess\
progresses slowly, and finally reaches a free surface--generally the\
skin. As it does so there may be some pain, redness, and local elevation\
of temperature. Fluctuation becomes evident and superficial, and the\
skin becomes livid and finally gives way. If the case is left to nature,\
the discharge of pus continues, and the track opening on the skin\
remains as a _sinus_. The persistence of suppuration is due to the\
presence in the wall of the abscess and of the sinus, of tuberculous\
granulation tissue, which, so long as it remains, continues to furnish\
discharge, and so prevents healing. Sooner or later pyogenic organisms\
gain access to the sinus, and through it to the wall of the abscess.\
They tend further to depress the resisting power of the tissues, and\
thereby aggravate and perpetuate the tuberculous disease. This\
superadded infection with pyogenic organisms exposes the patient to the\
further risks of septic intoxication, especially in the form of hectic\
fever and septicaemia, and increases the liability to general\
tuberculosis, and to waxy degeneration of the internal organs. The mixed\
infection is chiefly responsible for the pyrexia, sweating, and\
emaciation which the laity associate with consumptive disease. A\
tuberculous abscess may in one or other of these ways be a cause of\
death.\
\
_Residual abscess_ is the name given to an abscess that makes its\
appearance months, or even years, after the apparent cure of tuberculous\
disease--as, for example, in the hip-joint or spine. It is called\
residual because it has its origin in the remains of the original\
disease.\
\
[Illustration: FIG. 34.--Tuberculous Abscess in right lumbar region in a\
woman aged thirty.]\
\
#Diagnosis.#--A cold abscess is to be diagnosed from a syphilitic gumma,\
a cyst, and from lipoma and other soft tumours. The differential\
diagnosis of these affections will be considered later; it is often made\
easier by recognising the presence of a lesion that is likely to cause a\
cold abscess, such as tuberculous disease of the spine or of the\
sacro-iliac joint. When it is about to burst externally, it may be\
difficult to distinguish a tuberculous abscess from one due to infection\
with pyogenic organisms. Even when the abscess is opened, the\
appearances of the pus may not supply the desired information, and it\
may be necessary to submit it to bacteriological examination. When the\
pus is found to be sterile, it is usually safe to assume that the\
condition is tuberculous, as in other forms of suppuration the causative\
organisms can usually be recognised. Experimental inoculation will\
establish a definite diagnosis, but it implies a delay of two to three\
weeks.\
\
#Treatment.#--The tuberculous abscess may recede and disappear under\
general treatment. Many surgeons advise that so long as the abscess is\
quiescent it should be left alone. All agree, however, that if it shows\
a tendency to spread, to increase in size, or to approach the skin or a\
mucous membrane, something should be done to avoid the danger of its\
bursting and becoming infected with pyogenic organisms. Simple\
evacuation of the abscess by a hollow needle may suffice, or bismuth or\
iodoform may be introduced after withdrawal of the contents.\
\
_Evacuation of the Abscess and Injection of Iodoform._--The iodoform is\
employed in the form of a 10 per cent. solution in ether or the same\
proportion suspended in glycerin. Either form becomes sterile soon after\
it is prepared. Its curative effects would appear to depend upon the\
liberation of iodine, which restrains the activity of the bacilli, and\
upon its capacity for irritating the tissues and so inducing a\
protective leucocytosis, and also of stimulating the formation of scar\
tissue. An anaesthetic is rarely called for, except in children. The\
abscess is first evacuated by means of a large trocar and cannula\
introduced obliquely through the overlying soft parts, avoiding any part\
where the skin is thin or red. If the cannula becomes blocked with\
caseous material, it may be cleared with a probe, or a small quantity of\
saline solution is forced in by the syringe. The iodoform is injected by\
means of a glass-barrelled syringe, which is firmly screwed on to the\
cannula. The amount injected varies with the size of the abscess and the\
age of the patient; it may be said to range from two or three drams in\
the case of children to several ounces in large abscesses in adults. The\
cannula is withdrawn, the puncture is closed by a Michel's clip, and a\
dressing applied so as to exert a certain amount of compression. If the\
abscess fills up again, the procedure should be repeated; in doing so,\
the contents show the coloration due to liberated iodine. When the\
contents are semi-solid, and cannot be withdrawn even through a large\
cannula, an incision must be made, and, after the cavity has been\
emptied, the iodoform is introduced through a short rubber tube attached\
to the syringe. Experience has shown that even large abscesses, such as\
those associated with spinal disease, may be cured by iodoform\
injection, and this even when rupture of the abscess on the skin surface\
has appeared to be imminent.\
\
Another method of treatment which is less popular now than it used to\
be, and which is chiefly applicable in abscesses of moderate size, is by\
_incision of the abscess and removal of the tuberculous tissue in its\
wall_ with the sharp spoon. An incision is made which will give free\
access to the interior of the abscess, so that outlying pockets or\
recesses may not be overlooked. After removal of the pus, the wall of\
the abscess is scraped with the Volkmann spoon or with Barker's flushing\
spoon, to get rid of the tuberculous tissue with which it is lined. In\
using the spoon, care must be taken that its sharp edge does not\
perforate the wall of a vein or other important structure. Any debris\
which may adhere to the walls is removed by rubbing with dry gauze. The\
oozing of blood is arrested by packing the cavity for a few minutes with\
gauze. After the packing is removed, iodoform powder is rubbed into the\
raw surface. The soft parts divided by the incision are sutured in\
layers so as to ensure primary union. If, on the other hand, there is\
fear of a mixed infection, especially in abscesses near the rectum or\
anus, it is safer to treat it by the open method, packing the cavity\
with iodoform worsted or bismuth gauze, which is renewed at intervals of\
a week or ten days as the cavity heals from the bottom.\
\
Another method is to incise the abscess, cleanse the cavity with gauze,\
irrigate with Carrel-Dakin solution and pack with gauze smeared with the\
dilute non-toxic B.I.P.P. (bismuth and iodoform 2 parts, vaseline 12\
parts, hard paraffin, sufficient to give the consistence of butter). The\
wound is closed with "bipped" silk sutures; one of these--the "waiting\
suture"--is left loose to permit of withdrawal of the gauze after\
forty-eight hours; the waiting suture is then tied, and delayed primary\
union is thus effected.\
\
When the skin over the abscess is red, thin, and about to give way, as\
is frequently the case when the abscess is situated in the subcutaneous\
cellular tissue, any skin which is undermined and infected with tubercle\
should be removed with the scissors at the same time that the abscess is\
dealt with.\
\
In abscesses treated by the open method, when the cavity has become\
lined with healthy granulations, it may be closed by secondary suture,\
or, if the granulating surface is flush with the skin, healing may be\
hastened by skin-grafting.\
\
If the tuberculous abscess has burst and left a _sinus_, this is apt to\
persist because of the presence of tuberculous tissue in its wall, and\
of superadded pyogenic infection, or because it serves as an avenue for\
the escape of discharge from a focus of tubercle in a bone or a lymph\
gland.\
\
[Illustration: FIG. 35.--Tuberculous Sinus injected through its opening\
in the forearm with bismuth paste.\
\
(Mr. Pirie Watson's case--Radiogram by Dr. Hope Fowler.)]\
\
The treatment varies with the conditions present, and must include\
measures directed to the lesion from which the sinus has originated. The\
extent and direction of any given sinus may be demonstrated by the use\
of the probe, or, more accurately, by injecting the sinus with a paste\
consisting of white vaseline containing 10 to 30 per cent. of bismuth\
subcarbonate, and following its track with the X-rays (Fig. 35).\
\
It was found by Beck of Chicago that the injection of bismuth paste is\
frequently followed by healing of the sinus, and that, if one injection\
fails to bring about a cure, repeating the injection every second day\
may be successful. Some caution must be observed in this treatment, as\
symptoms of poisoning have been observed to follow its use. If they\
manifest themselves, an injection of warm olive oil should be given; the\
oil, left in for twelve hours or so, forms an emulsion with the bismuth,\
which can be withdrawn by aspiration. Iodoform suspended in glycerin may\
be employed in a similar manner. When these and other non-operative\
measures fail, and the whole track of the sinus is accessible, it should\
be laid open, scraped, and packed with bismuth or iodoform gauze until\
it heals from the bottom.\
\
The _tuberculous ulcer_ is described in the chapter on ulcers.\
\
\
\
\
CHAPTER IX\
\
SYPHILIS\
\
\
Definition.--Virus.--ACQUIRED SYPHILIS--Primary period:\
    _Incubation, primary chancre, glandular enlargement_;\
    _Extra-genital chancres_--Treatment--Secondary period: _General\
    symptoms, skin affections, mucous patches, affections of bones,\
    joints, eyes_, etc.--Treatment: _Salvarsan_--_Methods of\
    administering mercury_--Syphilis and marriage--Intermediate\
    stage--_Reminders_--Tertiary period: _General symptoms_,\
    _gummata_, _tertiary ulcers_, _tertiary lesions of skin, mucous\
    membrane, bones, joints_, etc.--Second attacks.--INHERITED\
    SYPHILIS--Transmission--_Clinical features in infancy, in later\
    life_--Contagiousness--Treatment.\
\
Syphilis is an infective disease due to the entrance into the body of a\
specific virus. It is nearly always communicated from one individual to\
another by contact infection, the discharge from a syphilitic lesion\
being the medium through which the virus is transmitted, and the seat of\
inoculation is almost invariably a surface covered by squamous\
epithelium. The disease was unknown in Europe before the year 1493, when\
it was introduced into Spain by Columbus' crew, who were infected in\
Haiti, where the disease had been endemic from time immemorial (Bloch).\
\
The granulation tissue which forms as a result of the reaction of the\
tissues to the presence of the virus is chiefly composed of lymphocytes\
and plasma cells, along with an abundant new formation of capillary\
blood vessels. Giant cells are not uncommon, but the endothelioid cells,\
which are so marked a feature of tuberculous granulation tissue, are\
practically absent.\
\
When syphilis is communicated from one individual to another by contact\
infection, the condition is spoken of as _acquired syphilis_, and the\
first visible sign of the disease appears at the site of inoculation,\
and is known as _the primary lesion_. Those who have thus acquired the\
disease may transmit it to their offspring, who are then said to suffer\
from _inherited syphilis_.\
\
#The Virus of Syphilis.#--The cause of syphilis, whether acquired or\
inherited, is the organism, described by Schaudinn and Hoffman, in 1905,\
under the name of _spirochaeta pallida_ or _spironema pallidum_. It is a\
delicate, thread-like spirilla, in length averaging from 8 to 10 u and\
in width about 0.25 u, and is distinguished from other spirochaetes by\
its delicate shape, its dead-white appearance, together with its closely\
twisted spiral form, with numerous undulations (10 to 26), which are\
perfectly regular, and are characteristic in that they remain the same\
during rest and in active movement (Fig. 36). In a fresh specimen, such\
as a scraping from a hard chancre suspended in a little salt solution,\
it shows active movements. The organism is readily destroyed by heat,\
and perishes in the absence of moisture. It has been proved\
experimentally that it remains infective only up to six hours after its\
removal from the body. Noguchi has succeeded in obtaining pure cultures\
from the infected tissues of the rabbit.\
\
[Illustration: FIG. 36.--Spirochaeta pallida from scraping of hard\
Chancre of Prepuce. x 1000 diam. Burri method.]\
\
The spirochaete may be recognised in films made by scraping the deeper\
parts of the primary lesion, from papules on the skin, or from blisters\
artificially raised on lesions of the skin or on the immediately\
adjacent portion of healthy skin. It is readily found in the mucous\
patches and condylomata of the secondary period. It is best stained by\
Giemsa's method, and its recognition is greatly aided by the use of the\
ultra-microscope.\
\
The spirochaete has been demonstrated in every form of syphilitic lesion,\
and has been isolated from the blood--with difficulty--and from lymph\
withdrawn by a hollow needle from enlarged lymph glands. The saliva of\
persons suffering from syphilitic lesions of the mouth also contains the\
organism.\
\
[Illustration: FIG. 37.--Spirochaeta refrigerans from scraping of Vagina.\
x 1000 diam. Burri method.]\
\
In tertiary lesions there is greater difficulty in demonstrating the\
spirochaete, but small numbers have been found in the peripheral parts of\
gummata and in the thickened patches in syphilitic disease of the aorta.\
Noguchi and Moore have discovered the spirochaete in the brain in a\
number of cases of general paralysis of the insane. The spirochaete may\
persist in the body for a long time after infection; its presence has\
been demonstrated as long as sixteen years after the original\
acquisition of the disease.\
\
In inherited syphilis the spirochaete is present in enormous numbers\
throughout all the organs and fluids of the body.\
\
Considerable interest attaches to the observations of Metchnikoff, Roux,\
and Neisser, who have succeeded in conveying syphilis to the chimpanzee\
and other members of the ape tribe, obtaining primary and secondary\
lesions similar to those observed in man, and also containing the\
spirochaete. In animals the disease has been transmitted by material from\
all kinds of syphilitic lesions, including even the blood in the\
secondary and tertiary stages of the disease. The primary lesion is in\
the form of an indurated papule, in every respect resembling the\
corresponding lesion in man, and associated with enlargement and\
induration of the lymph glands. The primary lesion usually appears about\
thirty days after inoculation, to be followed, in about half the cases,\
by secondary manifestations, which are usually of a mild character; in\
no instance has any tertiary lesion been observed. The severity of the\
affection amongst apes would appear to be in proportion to the nearness\
of the relationship of the animal to the human subject. The eye of the\
rabbit is also susceptible to inoculation from syphilitic lesions; the\
material in a finely divided state is introduced into the anterior\
chamber of the eye.\
\
Attempts to immunise against the disease have so far proved negative,\
but Metchnikoff has shown that the inunction of the part inoculated with\
an ointment containing 33 per cent. of calomel, within one hour of\
infection, suffices to neutralise the virus in man, and up to eighteen\
hours in monkeys. He recommends the adoption of this procedure in the\
prophylaxis of syphilis.\
\
Noguchi has made an emulsion of dead spirochaetes which he calls\
_luetin_, and which gives a specific reaction resembling that of\
tuberculin in tuberculosis, a papule or a pustule forming at the site of\
the intra-dermal injection. It is said to be most efficacious in the\
tertiary and latent forms of syphilis, which are precisely those forms\
in which the diagnosis is surrounded with difficulties.\
\
\
ACQUIRED SYPHILIS\
\
In the vast majority of cases, infection takes place during the congress\
of the sexes. Delicate, easily abraded surfaces are then brought into\
contact, and the discharge from lesions containing the virus is placed\
under favourable conditions for conveying the disease from one person to\
the other. In the male the possibility of infection taking place is\
increased if the virus is retained under cover of a long and tight\
prepuce, and if there are abrasions on the surface with which it comes\
in contact. The frequency with which infection takes place on the\
genitals during sexual intercourse warrants syphilis being considered a\
venereal disease, although there are other ways in which it may be\
contracted.\
\
Some of these imply direct contact--such, for example, as kissing, the\
digital examination of syphilitic patients by doctors or nurses, or\
infection of the surgeon's fingers while operating upon a syphilitic\
patient. In suckling, a syphilitic wet nurse may infect a healthy\
infant, or a syphilitic infant may infect a healthy wet nurse. In other\
cases the infection is by indirect contact, the virus being conveyed\
through the medium of articles contaminated by a syphilitic\
patient--such, for example, as surgical instruments, tobacco pipes, wind\
instruments, table utensils, towels, or underclothing. Physiological\
secretions, such as saliva, milk, or tears, are not capable of\
communicating the disease unless contaminated by discharge from a\
syphilitic sore. While the saliva itself is innocuous, it can be, and\
often is, contaminated by the discharge from mucous patches or other\
syphilitic lesions in the mouth and throat, and is then a dangerous\
medium of infection. Unless these extra-genital sources of infection are\
borne in mind, there is a danger of failing to recognise the primary\
lesion of syphilis in unusual positions, such as the lip, finger, or\
nipple. When the disease is thus acquired by innocent transfer, it is\
known as _syphilis insontium_.\
\
#Stages or Periods of Syphilis.#--Following the teaching of Ricord, it\
is customary to divide the life-history of syphilis into three periods\
or stages, referred to, for convenience, as primary, secondary, and\
tertiary. This division is to some extent arbitrary and artificial, as\
the different stages overlap one another, and the lesions of one stage\
merge insensibly into those of another. Wide variations are met with in\
the manifestations of the secondary stage, and histologically there is\
no valid distinction to be drawn between secondary and tertiary lesions.\
\
_The primary period_ embraces the interval that elapses between the\
initial infection and the first constitutional manifestations,--roughly,\
from four to eight weeks,--and includes the period of incubation, the\
development of the primary sore, and the enlargement of the nearest\
lymph glands.\
\
_The secondary period_ varies in duration from one to two years, during\
which time the patient is liable to suffer from manifestations which are\
for the most part superficial in character, affecting the skin and its\
appendages, the mucous membranes, and the lymph glands.\
\
_The tertiary period_ has no time-limit except that it follows upon the\
secondary, so that during the remainder of his life the patient is\
liable to suffer from manifestations which may affect the deeper tissues\
and internal organs as well as the skin and mucous membranes.\
\
#Primary Syphilis.#--_The period of incubation_ represents the interval\
that elapses between the occurrence of infection and the appearance of\
the primary lesion at the site of inoculation. Its limits may be stated\
as varying from two to six weeks, with an average of from twenty-one to\
twenty-eight days. While the disease is incubating, there is nothing to\
show that infection has occurred.\
\
_The Primary Lesion._--The incubation period having elapsed, there\
appears at the site of inoculation a circumscribed area of infiltration\
which represents the reaction of the tissues to the entrance of the\
virus. The first appearance is that of a sharply defined papule, rarely\
larger than a split pea. Its surface is at first smooth and shiny, but\
as necrosis of the tissue elements takes place in the centre, it becomes\
concave, and in many cases the epithelium is shed, and an ulcer is\
formed. Such an ulcer has an elevated border, sharply cut edges, an\
indurated base, and exudes a scanty serous discharge; its surface is at\
first occupied by yellow necrosed tissue, but in time this is replaced\
by smooth, pale-pink granulation tissue; finally, epithelium may spread\
over the surface, and the ulcer heals. As a rule, the patient suffers\
little discomfort, and may even be ignorant of the existence of the\
lesion, unless, as a result of exposure to mechanical or septic\
irritation, ulceration ensues, and the sore becomes painful and tender,\
and yields a purulent discharge. The primary lesion may persist until\
the secondary manifestations make their appearance, that is, for several\
weeks.\
\
It cannot be emphasised too strongly that the induration of the primary\
lesion, which has obtained for it the name of "hard chancre," is its\
most important characteristic. It is best appreciated when the sore is\
grasped from side to side between the finger and thumb. The sensation on\
grasping it has been aptly compared to that imparted by a nodule of\
cartilage, or by a button felt through a layer of cloth. The evidence\
obtained by touch is more valuable than that obtained by inspection, a\
fact which is made use of in the recognition of _concealed\
chancres_--that is, those which are hidden by a tight prepuce. The\
induration is due not only to the dense packing of the connective-tissue\
spaces with lymphocytes and plasma cells, but also to the formation of\
new connective-tissue elements. It is most marked in chancres situated\
in the furrow between the glans and the prepuce.\
\
_In the male_, the primary lesion specially affects certain\
_situations_, and the appearances vary with these: (1) On the inner\
aspect of the prepuce, and in the fold between the prepuce and the\
glans; in the latter situation the induration imparts a "collar-like"\
rigidity to the prepuce, which is most apparent when it is rolled back\
over the corona. (2) At the orifice of the prepuce the primary lesion\
assumes the form of multiple linear ulcers or fissures, and as each of\
these is attended with infiltration, the prepuce cannot be pulled\
back--a condition known as _syphilitic phimosis_. (3) On the glans penis\
the infiltration may be so superficial that it resembles a layer of\
parchment, but if it invades the cavernous tissue there is a dense mass\
of induration. (4) On the external aspect of the prepuce or on the skin\
of the penis itself. (5) At either end of the torn fraenum, in the form\
of a diamond-shaped ulcer raised above the surroundings. (6) In relation\
to the meatus and canal of the urethra, in either of which situations\
the swelling and induration may lead to narrowing of the urethra, so\
that the urine is passed with pain and difficulty and in a minute\
stream; stricture results only in the exceptional cases in which the\
chancre has ulcerated and caused destruction of tissue. A chancre within\
the orifice of the urethra is rare, and, being concealed from view, it\
can only be recognised by the discharge from the meatus and by the\
induration felt between the finger and thumb on palpating the urethra.\
\
_In the female_, the primary lesion is not so typical or so easily\
recognised as in men; it is usually met with on the labia; the\
induration is rarely characteristic and does not last so long. The\
primary lesion may take the form of condylomata. Indurated oedema, with\
brownish-red or livid discoloration of one or both labia, is diagnostic\
of syphilis.\
\
The hard chancre is usually solitary, but sometimes there are two or\
more; when there are several, they are individually smaller than the\
solitary chancre.\
\
It is the exception for a hard chancre to leave a visible scar, hence,\
in examining patients with a doubtful history of syphilis, little\
reliance can be placed on the presence or absence of a scar on the\
genitals. When the primary lesion has taken the form of an open ulcer\
with purulent discharge, or has sloughed, there is a permanent scar.\
\
_Infection of the adjacent lymph glands_ is usually found to have taken\
place by the time the primary lesion has acquired its characteristic\
induration. Several of the glands along Poupart's ligament, on one or on\
both sides, become enlarged, rounded, and indurated; they are usually\
freely movable, and are rarely sensitive unless there is superadded\
septic infection. The term _bullet-bubo_ has been applied to them, and\
their presence is of great value in diagnosis. In a certain number of\
cases, one of the main _lymph vessels_ on the dorsum of the penis is\
transformed into a fibrous cord easily recognisable on palpation, and\
when grasped between the fingers appears to be in size and consistence\
not unlike the vas deferens.\
\
_Concealed chancre_ is the term applied when one or more chancres are\
situated within the sac of a prepuce which cannot be retracted. If the\
induration is well marked, the chancre can be palpated through the\
prepuce, and is tender on pressure. As under these conditions it is\
impossible for the patient to keep the parts clean, septic infection\
becomes a prominent feature, the prepuce is oedematous and inflamed, and\
there is an abundant discharge of pus from its orifice. It occasionally\
happens that the infection assumes a virulent character and causes\
sloughing of the prepuce--a condition known as _phagedaena_. The\
discharge is then foul and blood-stained, and the prepuce becomes of a\
dusky red or purple colour, and may finally slough, exposing the glans.\
\
_Extra-genital or Erratic Chancres_ (Fig. 38).--Erratic chancre is the\
term applied by Jonathan Hutchinson to the primary lesion of syphilis\
when it appears on parts of the body other than the genitals. It differs\
in some respects from the hard chancre as met with on the penis; it is\
usually larger, the induration is more diffused, and the enlarged glands\
are softer and more sensitive. The glands in nearest relation to the\
sore are those first affected, for example, the epitrochlear or axillary\
glands in chancre of the finger; the submaxillary glands in chancre of\
the lip or mouth; or the pre-auricular gland in chancre of the eyelid or\
forehead. In consequence of their divergence from the typical chancre,\
and of their being often met with in persons who, from age,\
surroundings, or moral character, are unlikely subjects of venereal\
disease, the true nature of erratic chancres is often overlooked until\
the persistence of the lesion, its want of resemblance to anything else,\
or the onset of constitutional symptoms, determines the diagnosis of\
syphilis. A solitary, indolent sore occurring on the lip, eyelid,\
finger, or nipple, which does not heal but tends to increase in size,\
and is associated with induration and enlargement of the adjacent\
glands, is most likely to be the primary lesion of syphilis.\
\
[Illustration: FIG. 38.--Primary Lesion on Thumb, with Secondary\
Eruption on Forearm.[1]]\
\
[1] From _A System of Syphilis_, vol. ii., edited by D'Arcy Power and\
J. Keogh Murphy, Oxford Medical Publications.\
\
#The Soft Sore, Soft Chancre, or Chancroid.#--The differential diagnosis\
of syphilis necessitates the consideration of the _soft sore_, _soft\
chancre_, or _chancroid_, which is also a common form of venereal\
disease, and is due to infection with a virulent pus-forming bacillus,\
first described by Ducrey in 1889. Ducrey's bacillus occurs in the form\
of minute oval rods measuring about 1.5 u in length, which stain readily\
with any basic aniline dye, but are quickly decolorised by Gram's\
method. They are found mixed with other organisms in the purulent\
discharge from the sore, and are chiefly arranged in small groups or in\
short chains. Soft sores are always contracted by direct contact from\
another individual, and the incubation period is a short one of from two\
to five days. They are usually situated in the vicinity of the fraenum,\
and, in women, about the labia minora or fourchette; they probably\
originate in abrasions in these situations. They appear as pustules,\
which are rapidly converted into small, acutely inflamed ulcers with\
sharply cut, irregular margins, which bleed easily and yield an abundant\
yellow purulent discharge. They are devoid of the induration of\
syphilis, are painful, and nearly always multiple, reproducing\
themselves in successive crops by auto-inoculation. Soft sores are often\
complicated by phimosis and balanitis, and they frequently lead to\
infection of the glands in the groin. The resulting bubo is ill-defined,\
painful, and tender, and suppuration occurs in about one-fourth of the\
cases. The overlying skin becomes adherent and red, and suppuration\
takes place either in the form of separate foci in the interior of the\
individual glands, or around them; in the latter case, on incision, the\
glands are found lying bathed in pus. Ducrey's bacillus is found in pure\
culture in the pus. Sometimes other pyogenic organisms are superadded.\
After the bubo has been opened the wound may take on the characters of a\
soft sore.\
\
_Treatment._--Soft sores heal rapidly when kept clean. If concealed\
under a tight prepuce, an incision should be made along the dorsum to\
give access to the sores. They should be washed with eusol, and dusted\
with a mixture of one part iodoform and two parts boracic or salicylic\
acid, or, when the odour of iodoform is objected to, of equal parts of\
boracic acid and carbonate of zinc. Immersion of the penis in a bath of\
eusol for some hours daily is useful. The sore is then covered with a\
piece of gauze kept in position by drawing the prepuce over it, or by a\
few turns of a narrow bandage. Sublimed sulphur frequently rubbed into\
the sore is recommended by C. H. Mills. If the sores spread in spite of\
this, they should be painted with cocaine and then cauterised. When the\
glands in the groin are infected, the patient must be confined to bed,\
and a dressing impregnated with ichthyol and glycerin (10 per cent.)\
applied; the repeated use of a suction bell is of great service.\
Harrison recommends aspiration of a bubonic abscess, followed by\
injection of 1 in 20 solution of tincture of iodine into the cavity;\
this is in turn aspirated, and then 1 or 2 c.c. of the solution injected\
and left in. This is repeated as often as the cavity refills. It is\
sometimes necessary to let the pus out by one or more small incisions\
and continue the use of the suction bell.\
\
_Diagnosis of Primary Syphilis._--In cases in which there is a history\
of an incubation period of from three to five weeks, when the sore is\
indurated, persistent, and indolent, and attended with bullet-buboes in\
the groin, the diagnosis of primary syphilis is not difficult. Owing,\
however, to the great importance of instituting treatment at the\
earliest possible stage of the infection, an effort should be made to\
establish the diagnosis without delay by demonstrating the spirochaete.\
Before any antiseptic is applied, the margin of the suspected sore is\
rubbed with gauze, and the serum that exudes on pressure is collected\
in a capillary tube and sent to a pathologist for microscopical\
examination. A better specimen can sometimes be obtained by puncturing\
an enlarged lymph gland with a hypodermic needle, injecting a few minims\
of sterile saline solution and then aspirating the blood-stained fluid.\
\
The Wassermann test must not be relied upon for diagnosis in the early\
stage, as it does not appear until the disease has become generalised\
and the secondary manifestations are about to begin. The practice of\
waiting in doubtful cases before making a diagnosis until secondary\
manifestations appear is to be condemned.\
\
Extra-genital chancres, _e.g._ sores on the fingers of doctors or\
nurses, are specially liable to be overlooked, if the possibility of\
syphilis is not kept in mind.\
\
It is important to bear in mind _the possibility of a patient having\
acquired a mixed infection_ with the virus of soft chancre, which will\
manifest itself a few days after infection, and the virus of syphilis,\
which shows itself after an interval of several weeks. This occurrence\
was formerly the source of much confusion in diagnosis, and it was\
believed at one time that syphilis might result from soft sores, but it\
is now established that syphilis does not follow upon soft sores unless\
the virus of syphilis has been introduced at the same time. The\
practitioner must be on his guard, therefore, when a patient asks his\
advice concerning a venereal sore which has appeared within a few days\
of exposure to infection. Such a patient is naturally anxious to know\
whether he has contracted syphilis or not, but neither a positive nor a\
negative answer can be given--unless the spirochaete can be identified.\
\
Syphilis is also to be diagnosed from _epithelioma_, the common form of\
cancer of the penis. It is especially in elderly patients with a tight\
prepuce that the induration of syphilis is liable to be mistaken for\
that associated with epithelioma. In difficult cases the prepuce must be\
slit open.\
\
Difficulty may occur in the diagnosis of primary syphilis from _herpes_,\
as this may appear as late as ten days after connection; it commences as\
a group of vesicles which soon burst and leave shallow ulcers with a\
yellow floor; these disappear quickly on the use of an antiseptic\
dusting powder.\
\
Apprehensive patients who have committed sexual indiscretions are apt to\
regard as syphilitic any lesion which happens to be located on the\
penis--for example, acne pustules, eczema, psoriasis papules, boils,\
balanitis, or venereal warts.\
\
_The local treatment_ of the primary sore consists in attempting to\
destroy the organisms _in situ_. An ointment made up of calomel 33\
parts, lanoline 67 parts, and vaseline 10 parts (Metchnikoff's cream) is\
rubbed into the sore several times a day. If the surface is unbroken, it\
may be dusted lightly with a powder composed of equal parts of calomel\
and carbonate of zinc. A gauze dressing is applied, and the penis and\
scrotum should be supported against the abdominal wall by a triangular\
handkerchief or bathing-drawers; if there is inflammatory oedema the\
patient should be confined to bed.\
\
In _concealed chancres_ with phimosis, the sac of the prepuce should be\
slit up along the dorsum to admit of the ointment being applied. If\
phagedaena occurs, the prepuce must be slit open along the dorsum, or if\
sloughing, cut away, and the patient should have frequent sitz baths of\
weak sublimate lotion. When the chancre is within the meatus, iodoform\
bougies are inserted into the urethra, and the urine should be rendered\
bland by drinking large quantities of fluid.\
\
General treatment is considered on p. 149.\
\
#Secondary Syphilis.#--The following description of secondary syphilis\
is based on the average course of the disease in untreated cases. The\
onset of constitutional symptoms occurs from six to twelve weeks after\
infection, and the manifestations are the result of the entrance of the\
virus into the general circulation, and its being carried to all parts\
of the body. The period during which the patient is liable to suffer\
from secondary symptoms ranges from six months to two years.\
\
In some cases the general health is not disturbed; in others the patient\
is feverish and out of sorts, losing appetite, becoming pale and anaemic,\
complaining of lassitude, incapacity for exertion, headache, and pains\
of a rheumatic type referred to the bones. There is a moderate degree of\
leucocytosis, but the increase is due not to the polymorpho-nuclear\
leucocytes but to lymphocytes. In isolated cases the temperature rises\
to 101 o or 102 o F. and the patient loses flesh. The lymph glands,\
particularly those along the posterior border of the sterno-mastoid,\
become enlarged and slightly tender. The hair comes out, eruptions\
appear on the skin and mucous membranes, and the patient may suffer from\
sore throat and affections of the eyes. The local lesions are to be\
regarded as being of the nature of reactions against accumulations of\
the parasite, lymphocytes and plasma cells being the elements chiefly\
concerned in the reactive process.\
\
_Affections of the Skin_ are among the most constant manifestations. An\
evanescent macular rash, not unlike that of measles--_roseola_--is the\
first to appear, usually in from six to eight weeks from the date of\
infection; it is widely diffused over the trunk, and the original dull\
rose-colour soon fades, leaving brownish stains, which in time\
disappear. It is usually followed by a _papular eruption_, the\
individual papules being raised above the surface of the skin, smooth or\
scaly, and as they are due to infiltration of the skin they are more\
persistent than the roseoles. They vary in size and distribution, being\
sometimes small, hard, polished, and closely aggregated like lichen,\
sometimes as large as a shilling-piece, with an accumulation of scales\
on the surface like that seen in psoriasis. The co-existence of scaly\
papules and faded roseoles is very suggestive of syphilis.\
\
Other types of eruption are less common, and are met with from the third\
month onwards. A _pustular_ eruption, not unlike that of acne, is\
sometimes a prominent feature, but is not characteristic of syphilis\
unless it affects the scalp and forehead and is associated with the\
remains of the papular eruption. The term _ecthyma_ is applied when the\
pustules are of large size, and, after breaking on the surface, give\
rise to superficial ulcers; the discharge from the ulcer often dries up\
and forms a scab or crust which is continually added to from below as\
the ulcer extends in area and depth. The term _rupia_ is applied when\
the crusts are prominent, dark in colour, and conical in shape, roughly\
resembling the shell of a limpet. If the crust is detached, a sharply\
defined ulcer is exposed, and when this heals it leaves a scar which is\
usually circular, thin, white, shining like satin, and the surrounding\
skin is darkly pigmented; in the case of deep ulcers, the scar is\
depressed and adherent (Fig. 39).\
\
[Illustration: FIG. 39.--Syphilitic Rupia, showing the limpet-shaped\
crusts or scabs.]\
\
In the later stages there may occur a form of creeping or _spreading\
ulceration of the skin_ of the face, groin, or scrotum, healing at one\
edge and spreading at another like tuberculous lupus, but distinguished\
from this by its more rapid progress and by the pigmentation of the\
scar.\
\
_Condylomata_ are more characteristic of syphilis than any other type of\
skin lesion. They are papules occurring on those parts of the body where\
the skin is habitually moist, and especially where two skin surfaces are\
in contact. They are chiefly met with on the external genitals,\
especially in women, around the anus, beneath large pendulous mammae,\
between the toes, and at the angles of the mouth, and in these\
situations their development is greatly favoured by neglect of\
cleanliness. They present the appearance of well-defined circular or\
ovoid areas in which the skin is thickened and raised above the surface;\
they are covered with a white sodden epidermis, and furnish a scanty but\
very infective discharge. Under the influence of irritation and want of\
rest, as at the anus or at the angle of the mouth, they are apt to\
become fissured and superficially ulcerated, and the discharge then\
becomes abundant and may crust on the surface, forming yellow scabs. At\
the angle of the mouth the condylomatous patches may spread to the\
cheek, and when they ulcerate may leave fissure-like scars radiating\
from the mouth--an appearance best seen in inherited syphilis (Fig. 44).\
\
_The Appendages of the Skin._--The _hair_ loses its gloss, becomes dry\
and brittle, and readily falls out, either as an exaggeration of the\
normal shedding of the hair, or in scattered areas over the scalp\
(_syphilitic alopoecia_). The hair is not re-formed in the scars which\
result from ulcerated lesions of the scalp. The _nail-folds_\
occasionally present a pustular eruption and superficial ulceration, to\
which the name _syphilitic onychia_ has been applied; more commonly the\
nails become brittle and ragged, and they may even be shed.\
\
_The Mucous Membranes_, and especially those of the _mouth_ and\
_throat_, suffer from lesions similar to those met with on the skin. On\
a mucous surface the papular eruption assumes the form of _mucous\
patches_, which are areas with a congested base covered with a thin\
white film of sodden epithelium like wet tissue-paper. They are best\
seen on the inner aspect of the cheeks, the soft palate, uvula, pillars\
of the fauces, and tonsils. In addition to mucous patches, there may be\
a number of small, _superficial, kidney-shaped ulcers_, especially along\
the margins of the tongue and on the tonsils. In the absence of mucous\
patches and ulcers, the sore throat may be characterised by a bluish\
tinge of the inflamed mucous membrane and a thin film of shed epithelium\
on the surface. Sometimes there is an elongated sinuous film which has\
been likened to the track of a snail. In the _larynx_ the presence of\
congestion, oedema, and mucous patches may be the cause of persistent\
hoarseness. The _tongue_ often presents a combination of lesions,\
including ulcers, patches where the papillae are absent, fissures, and\
raised white papules resembling warts, especially towards the centre of\
the dorsum. These lesions are specially apt to occur in those who smoke,\
drink undiluted alcohol or spirits, or eat hot condiments to excess, or\
who have irregular, sharp-cornered teeth. At a later period, and in\
those who are broken down in health from intemperance or other cause,\
the sore throat may take the form of rapidly spreading, penetrating\
ulcers in the soft palate and pillars of the fauces, which may lead to\
extensive destruction of tissue, with subsequent scars and deformity\
highly characteristic of previous syphilis.\
\
In the _Bones_, lesions occur which assume the clinical features of an\
evanescent periostitis, the patient complaining of nocturnal pains over\
the frontal bone, sternum, tibiae, and ulnae, and localised tenderness on\
tapping over these bones.\
\
In the _Joints_, a serous synovitis or hydrops may occur, chiefly in the\
knee, on one or on both sides.\
\
_The Affections of the Eyes_, although fortunately rare, are of great\
importance because of the serious results which may follow if they are\
not recognised and treated. _Iritis_ is the commonest of these, and may\
occur in one or in both eyes, one after the other, from three to eight\
months after infection. The patient complains of impairment of sight and\
of frontal or supraorbital pain. The eye waters and is hypersensitive,\
the iris is discoloured and reacts sluggishly to light, and there is a\
zone of ciliary congestion around the cornea. The appearance of minute\
white nodules or flakes of lymph at the margin of the pupil is\
especially characteristic of syphilitic iritis. When adhesions have\
formed between the iris and the structures in relation to it, the pupil\
dilates irregularly under atropin. Although complete recovery is to be\
expected under early and energetic treatment, if neglected, _iritis_ may\
result in occlusion of the pupil and permanent impairment or loss of\
sight.\
\
The other lesions of the eye are much rarer, and can only be discovered\
on ophthalmoscopic examination.\
\
The virus of syphilis exerts a special influence upon the _Blood\
Vessels_, exciting a proliferation of the endothelial lining which\
results in narrowing of their lumen, _endarteritis_, and a perivascular\
infiltration in the form of accumulations of plasma cells around the\
vessels and in the lymphatics that accompany them.\
\
In the _Brain_, in the later periods of secondary and in tertiary\
syphilis, changes occur as a result of the narrowing of the lumen of the\
arteries, or of their complete obliteration by thrombosis. By\
interfering with the nutrition of those parts of the brain supplied by\
the affected arteries, these lesions give rise to clinical features of\
which severe headache and paralysis are the most prominent.\
\
Affections of the _Spinal Cord_ are extremely rare, but paraplegia from\
myelitis has been observed.\
\
Lastly, attention must be directed to the remarkable variations observed\
in different patients. Sometimes the virulent character of the disease\
can only be accounted for by an idiosyncrasy of the patient.\
Constitutional symptoms, particularly pyrexia and anaemia, are most often\
met with in young women. Patients over forty years of age have greater\
difficulty in overcoming the infection than younger adults. Malarial and\
other infections, and the conditions attending life in tropical\
countries, from the debility which they cause, tend to aggravate and\
prolong the disease, which then assumes the characters of what has been\
called _malignant syphilis_. All chronic ailments have a similar\
influence, and alcoholic intemperance is universally regarded as a\
serious aggravating factor.\
\
_Diagnosis of Secondary Syphilis._--A routine examination should be made\
of the parts of the body which are most often affected in this\
disease--the scalp, mouth, throat, posterior cervical glands, and the\
trunk, the patient being stripped and examined by daylight. Among the\
_diagnostic features of the skin affections_ the following may be\
mentioned: They are frequently, and sometimes to a marked degree,\
symmetrical; more than one type of eruption--papules and pustules, for\
example--are present at the same time; there is little itching; they are\
at first a dull-red colour, but later present a brown pigmentation which\
has been likened to the colour of raw ham; they exhibit a predilection\
for those parts of the forehead and neck which are close to the roots of\
the hair; they tend to pass off spontaneously; and they disappear\
rapidly under treatment.\
\
#Serum Diagnosis--Wassermann Reaction.#--Wassermann found that if an\
extract of syphilitic liver rich in spirochaetes is mixed with the serum\
from a syphilitic patient, a large amount of complement is fixed. The\
application of the test is highly complicated and can only be carried\
out by an expert pathologist. For the purpose he is supplied with from 5\
c.c. to 10 c.c. of the patient's blood, withdrawn under aseptic\
conditions from the median basilic vein by means of a serum syringe, and\
transferred to a clean and dry glass tube. There is abundant evidence\
that the Wassermann test is a reliable means of establishing a diagnosis\
of syphilis.\
\
A definitely positive reaction can usually be obtained between the\
fifteenth and thirtieth day after the appearance of the primary lesion,\
and as time goes on it becomes more marked. During the secondary period\
the reaction is practically always positive. In the tertiary stage also\
it is positive except in so far as it is modified by the results of\
treatment. In para-syphilitic lesions such as general paralysis and\
tabes a positive reaction is almost always present. In inherited\
syphilis the reaction is positive in every case. A positive reaction may\
be present in other diseases, for example, frambesia, trypanosomiasis,\
and leprosy.\
\
As the presence of the reaction is an evidence of the activity of the\
spirochaetes, repeated applications of the test furnish a valuable means\
of estimating the efficacy of treatment. The object aimed at is to\
change a persistently positive reaction to a permanently negative one.\
\
#Treatment of Syphilis.#--In the treatment of syphilis the two main\
objects are to maintain the general health at the highest possible\
standard, and to introduce into the system therapeutic agents which will\
inhibit or destroy the invading parasite.\
\
The second of these objects has been achieved by the researches of\
Ehrlich, who, in conjunction with his pupil, Hata, has built up a\
compound, the dihydrochloride of dioxydiamido-arseno-benzol, popularly\
known as salvarsan or "606." Other preparations, such as kharsivan,\
arseno-billon, and diarsenol, are chemically equivalent to salvarsan,\
containing from 27 to 31 per cent. of arsenic, and are equally\
efficient. The full dose is 0.6 grm. All these members of the "606"\
group form an acid solution when dissolved in water, and must be\
rendered alkaline before being injected. As subcutaneous and\
intra-muscular injections cause considerable pain, and may cause\
sloughing of the tissues, "606" preparations must be injected\
intravenously. Ehrlich has devised a preparation--neo-salvarsan, or\
"914," which is more easily prepared and forms a neutral solution. It\
contains from 18 to 20 per cent. of arsenic. Neo-kharsivan,\
novo-arseno-billon, and neo-diarsenol belong to the "914" group, the\
full dosage of which is 0.9 grm. As subcutaneous and intra-muscular\
injections of the "914" group are not painful, and even more efficient\
than intravenous injections, the administration is simpler.\
\
Galyl, luargol, and other preparations act in the same way as the "606"\
and "914" groups.\
\
The "606" preparations may be introduced into the veins by injection or\
by means of an apparatus which allows the solution to flow in by\
gravity. The left median basilic vein is selected, and a platino-iridium\
needle with a short point and a bore larger than that of the ordinary\
hypodermic syringe is used. The needle is passed for a few millimetres\
along the vein, and the solution is then slowly introduced; before\
withdrawing the needle some saline is run in to diminish the risk of\
thrombosis.\
\
The "914" preparations may be injected either into the subcutaneous\
tissue of the buttock or into the substance of the gluteus muscle. The\
part is then massaged for a few minutes, and the massage is repeated\
daily for a few days.\
\
No hard-and-fast rules can be laid down as to what constitutes a\
complete course of treatment. Harrison recommends as a _minimum_ course\
of one of the "914" preparations in _early primary cases_ an initial\
dose of 0.45 grm. given intra-muscularly or into the deep subcutaneous\
tissue; the same dose a week later; 0.6 grm. the following week; then\
miss a week and give 9.6 grms. on two successive weeks; then miss two\
weeks and give 0.6 grm. on two more successive weeks.\
\
When a _positive Wassermann reaction_ is present before treatment is\
commenced, the above course is prolonged as follows: for three weeks is\
given a course of potassium iodide, after which four more weekly\
injections of 0.6 grm. of "914" are given.\
\
With each injection of "914" after the first, throughout the whole\
course 1 grain of mercury is injected intra-muscularly.\
\
In the course of a few hours, there is usually some indisposition, with\
a feeling of chilliness and slight rise of temperature; these symptoms\
pass off within twenty-four hours, and in a few days there is a decided\
improvement of health. Three or four days after an intra-muscular\
injection there may be pain and stiffness in the gluteal region.\
\
These preparations are the most efficient therapeutic agents that have\
yet been employed in the treatment of syphilis.\
\
The manifestations of the disease disappear with remarkable rapidity.\
Observations show that the spirochaetes lose their capacity for movement\
within an hour or two of the administration, and usually disappear\
altogether in from twenty-four to thirty-six hours. Wassermann's\
reaction usually yields a negative result in from three weeks to two\
months, but later may again become positive. Subsequent doses of the\
arsenical preparation are therefore usually indicated, and should be\
given in from 7 to 21 days according to the dose.\
\
When syphilis occurs in a _pregnant woman_, she should be given in the\
early months an ordinary course of "914," followed by 10-grain doses of\
potassium iodide twice daily. The injections may be repeated two months\
later, and during the remainder of the pregnancy 2-grain mercury pills\
are given twice daily (A. Campbell). The presence of albumen in the\
urine contra-indicates arsenical treatment.\
\
It need scarcely be pointed out that the use of powerful drugs like\
"606" and "914" is not free from risk; it may be mentioned that each\
dose contains nearly three grains of arsenic. Before the administration\
the patient must be overhauled; its administration is contra-indicated\
in the presence of disease of the heart and blood vessels, especially a\
combination of syphilitic aortitis and sclerosis of the coronary\
arteries, with degeneration of the heart muscle; in affections of the\
central nervous system, especially advanced paralysis, and in such\
disturbances of metabolism as are associated with diabetes and Bright's\
disease. Its use is not contra-indicated in any lesion of active\
syphilis.\
\
The administration is controlled by the systematic examination of the\
urine for arsenic.\
\
_The Administration of Mercury._--The success of the arsenical\
preparations has diminished the importance of mercury in the treatment\
of syphilis, but it is still used to supplement the effect of the\
injections. The amount of mercury to be given in any case must be\
proportioned to the idiosyncrasies of the patient, and it is advisable,\
before commencing the treatment, to test his urine and record his\
body-weight. The small amount of mercury given at the outset is\
gradually increased. If the body-weight falls, or if the gums become\
sore and the breath foul, the mercury should be stopped for a time. If\
salivation occurs, the drinking of hot water and the taking of hot baths\
should be insisted upon, and half-dram doses of the alkaline sulphates\
prescribed.\
\
_Methods of Administering Mercury._--(1) _By the Mouth._--This was for\
long the most popular method in this country, the preparation usually\
employed being grey powder, in pills or tablets, each of which contains\
one grain of the powder. Three of these are given daily in the first\
instance, and the daily dose is increased to five or even seven grains\
till the standard for the individual patient is arrived at. As the grey\
powder alone sometimes causes irritation of the bowels, it should be\
combined with iron, as in the following formula: Hydrarg. c. cret. gr. 1;\
ferri sulph. exsiccat. gr. 1 or 2.\
\
(2) _By Inunction._--Inunction consists in rubbing into the pores of the\
skin an ointment composed of equal parts of 20 per cent. oleate of\
mercury and lanolin. Every night after a hot bath, a dram of the\
ointment (made up by the chemist in paper packets) is rubbed for fifteen\
minutes into the skin where it is soft and comparatively free from\
hairs. When the patient has been brought under the influence of the\
mercury, inunction may be replaced by one of the other methods, of\
administering the drug.\
\
(3) _By Intra-muscular Injection._--This consists in introducing the\
drug by means of a hypodermic syringe into the substance of the gluteal\
muscles. The syringe is made of glass, and has a solid glass piston; the\
needle of platino-iridium should be 5 cm. long and of a larger calibre\
than the ordinary hypodermic needle. The preparation usually employed\
consists of: metallic mercury or calomel 1 dram, lanolin and olive oil\
each 2 drams; it must be warmed to allow of its passage through the\
needle. Five minims--containing one grain of metallic mercury--represent\
a dose, and this is injected into the muscles above and behind the great\
trochanter once a week. The contents of the syringe are slowly\
expressed, and, after withdrawing the needle, gentle massage of the\
buttock should be employed. Four courses each of ten injections are\
given the first year, three courses of the same number during the second\
and third years, and two courses during the fourth year (Lambkin).\
\
_The General Health._--The patient must lead a regular life and\
cultivate the fresh-air habit, which is as beneficial in syphilis as in\
tuberculosis. Anaemia, malaria, and other sources of debility must\
receive appropriate treatment. The diet should be simple and easily\
digested, and should include a full supply of milk. Alcohol is\
prohibited. The excretory organs are encouraged to act by the liberal\
drinking of hot water between meals, say five or six tumblerfuls in the\
twenty-four hours. The functions of the skin are further aided by\
frequent hot baths, and by the wearing of warm underclothing. While the\
patient should avoid exposure to cold, and taxing his energies by undue\
exertion, he should be advised to take exercise in the open air. On\
account of the liability to lesions of the mouth and throat, he should\
use tobacco in moderation, his teeth should be thoroughly overhauled by\
the dentist, and he should brush them after every meal, using an\
antiseptic tooth powder or wash. The mouth and throat should be rinsed\
out night and morning with a solution of chlorate of potash and alum, or\
with peroxide of hydrogen.\
\
_Treatment of the Local Manifestations._--_The skin lesions_ are treated\
on the same lines as similar eruptions of other origin. As local\
applications, preparations of mercury are usually selected, notably the\
ointments of the red oxide of mercury, ammoniated mercury, or oleate of\
mercury (5 per cent.), or the mercurial plaster introduced by Unna. In\
the treatment of condylomata the greatest attention must be paid to\
cleanliness and dryness. After washing and drying the affected patches,\
they are dusted with a powder consisting of equal parts of calomel and\
carbonate of zinc; and apposed skin surfaces, such as the nates or\
labia, are separated by sublimate wool. In the ulcers of later secondary\
syphilis, crusts are got rid of in the first instance by means of a\
boracic poultice, after which a piece of lint or gauze cut to the size\
of the ulcer and soaked in black wash is applied and covered with\
oil-silk. If the ulcer tends to spread in area or in depth, it should be\
scraped with a sharp spoon, and painted over with acid nitrate of\
mercury, or a local hyperaemia may be induced by Klapp's suction\
apparatus.\
\
_In lesions of the mouth and throat_, the teeth should be attended to;\
the best local application is a solution of chromic acid--10 grains to\
the ounce--painted on with a brush once daily. If this fails, the\
lesions may be dusted with calomel the last thing at night. For deep\
ulcers of the throat the patient should gargle frequently with chlorine\
water or with perchloride of mercury (1 in 2000); if the ulcer continues\
to spread it should be painted with acid nitrate of mercury.\
\
In the treatment of _iritis_ the eyes are shaded from the light and\
completely rested, and the pupil is well dilated by atropin to prevent\
adhesions. If there is much pain, a blister may be applied to the\
temple.\
\
_The Relations of Syphilis to Marriage._--Before the introduction of the\
Ehrlich-Hata treatment no patient was allowed to marry until three years\
had elapsed after the disappearance of the last manifestation. While\
marriage might be entered upon under these conditions without risk of\
the husband infecting the wife, the possibility of his conveying the\
disease to the offspring cannot be absolutely excluded. It is\
recommended, as a precautionary measure, to give a further mercurial\
course of two or three months' duration before marriage, and an\
intravenous injection of an arsenical preparation.\
\
#Intermediate Stage.#--After the dying away of the secondary\
manifestations and before the appearance of tertiary lesions, the\
patient may present certain symptoms which Hutchinson called\
_reminders_. These usually consist of relapses of certain of the\
affections of the skin, mouth, or throat, already described. In the\
skin, they may assume the form of peeling patches in the palms, or may\
appear as spreading and confluent circles of a scaly papular eruption,\
which if neglected may lead to the formation of fissures and superficial\
ulcers. Less frequently there is a relapse of the eye affections, or of\
paralytic symptoms from disease of the cerebral arteries.\
\
#Tertiary Syphilis.#--While the manifestations of primary and secondary\
syphilis are common, those of the tertiary period are by comparison\
rare, and are observed chiefly in those who have either neglected\
treatment or who have had their powers of resistance lowered by\
privation, by alcoholic indulgence, or by tropical disease.\
\
It is to be borne in mind that in a certain proportion of men and in a\
larger proportion of women, the patient has no knowledge of having\
suffered from syphilis. Certain slight but important signs may give the\
clue in a number of cases, such as irregularity of the pupils or failure\
to react to light, abnormality of the reflexes, and the discovery of\
patches of leucoplakia on the tongue, cheek, or palate.\
\
The _general character of tertiary manifestations_ may be stated as\
follows: They attack by preference the tissues derived from the\
mesoblastic layer of the embryo--the cellular tissue, bones, muscles,\
and viscera. They are often localised to one particular tissue or organ,\
such, for example, as the subcutaneous cellular tissue, the bones, or\
the liver, and they are rarely symmetrical. They are usually aggressive\
and persistent, with little tendency to natural cure, and they may be\
dangerous to life, because of the destructive changes produced in such\
organs as the brain or the larynx. They are remarkably amenable to\
treatment if instituted before the stage which is attended with\
destruction of tissue is reached. Early tertiary lesions may be\
infective, and the disease may be transmitted by the discharges from\
them; but the later the lesions the less is the risk of their containing\
an infective virus.\
\
The most prominent feature of tertiary syphilis consists in the\
formation of granulation tissue, and this takes place on a scale\
considerably larger than that observed in lesions of the secondary\
period. The granulation tissue frequently forms a definite swelling or\
tumour-like mass (syphiloma), which, from its peculiar elastic\
consistence, is known as a _gumma_. In its early stages a gumma is a\
firm, semi-translucent greyish or greyish-red mass of tissue; later it\
becomes opaque, yellow, and caseous, with a tendency to soften and\
liquefy. The gumma does harm by displacing and replacing the normal\
tissue elements of the part affected, and by involving these in the\
degenerative changes, of the nature of caseation and necrosis, which\
produce the destructive lesions of the skin, mucous membranes, and\
internal organs. This is true not only of the circumscribed gumma, but\
of the condition known as _gummatous infiltration_ or _syphilitic\
cirrhosis_, in which the granulation tissue is diffused throughout the\
connective-tissue framework of such organs as the tongue or liver. Both\
the gummatous lesions and the fibrosis of tertiary syphilis are directly\
excited by the spirochaetes.\
\
The life-history of an untreated gumma varies with its environment. When\
protected from injury and irritation in the substance of an internal\
organ such as the liver, it may become encapsulated by fibrous tissue,\
and persist in this condition for an indefinite period, or it may be\
absorbed and leave in its place a fibrous cicatrix. In the interior of a\
long bone it may replace the rigid framework of the shaft to such an\
extent as to lead to pathological fracture. If it is near the surface of\
the body--as, for example, in the subcutaneous or submucous cellular\
tissue, or in the periosteum of a superficial bone, such as the palate,\
the skull, or the tibia--the tissue of which it is composed is apt to\
undergo necrosis, in which the overlying skin or mucous membrane\
frequently participates, the result being an ulcer--the tertiary\
syphilitic ulcer (Figs. 40 and 41).\
\
_Tertiary Lesions of the Skin and Subcutaneous Cellular Tissue._--The\
clinical features of a _subcutaneous gumma_ are those of an indolent,\
painless, elastic swelling, varying in size from a pea to an almond or\
walnut. After a variable period it usually softens in the centre, the\
skin over it becomes livid and dusky, and finally separates as a slough,\
exposing the tissue of the gumma, which sometimes appears as a mucoid,\
yellowish, honey-like substance, more frequently as a sodden, caseated\
tissue resembling wash-leather. The caseated tissue of a gumma differs\
from that of a tuberculous lesion in being tough and firm, of a buff\
colour like wash-leather, or whitish, like boiled fish. The degenerated\
tissue separates slowly and gradually, and in untreated cases may be\
visible for weeks in the floor of the ulcer.\
\
[Illustration: FIG. 40.--Ulcerating Gumma of Lips.\
\
(From a photograph lent by Dr. Stopford Taylor and Dr. R. W. Mackenna.)]\
\
_The tertiary ulcer_ may be situated anywhere, but is most frequently\
met with on the leg, especially in the region of the knee (Fig. 42) and\
over the calf. There may be one or more ulcers, and also scars of\
antecedent ulcers. The edges are sharply cut, as if punched out; the\
margins are rounded in outline, firm, and congested; the base is\
occupied by gummatous tissue, or, if this has already separated and\
sloughed out, by unhealthy granulations and a thick purulent discharge.\
When the ulcer has healed it leaves a scar which is depressed, and if\
over a bone, is adherent to it. The features of the tertiary ulcer,\
however, are not always so characteristic as the above description would\
imply. It is to be diagnosed from the "leg ulcer," which occurs almost\
exclusively on the lower third of the leg; from Bazin's disease (p. 74);\
from the ulcers that result from certain forms of malignant disease,\
such as rodent cancer, and from those met with in chronic glanders.\
\
_Gummatous Infiltration of the Skin_ ("Syphilitic Lupus").--This is a\
lesion, met with chiefly on the face and in the region of the external\
genitals, in which the skin becomes infiltrated with granulation tissue\
so that it is thickened, raised above the surface, and of a brownish-red\
colour. It appears as isolated nodules, which may fuse together; the\
epidermis becomes scaly and is shed, giving rise to superficial ulcers\
which are usually covered by crusted discharge. The disease tends to\
spread, creeping over the skin with a serpiginous, crescentic, or\
horse-shoe margin, while the central portion may heal and leave a scar.\
From the fact of its healing in the centre while it spreads at the\
margin, it may resemble tuberculous disease of the skin. It can usually\
be differentiated by observing that the infiltration is on a larger\
scale; the progress is much more rapid, involving in the course of\
months an area which in the case of tuberculosis would require as many\
years; the scars are sounder and are less liable to break down again;\
and the disease rapidly yields to anti-syphilitic treatment.\
\
[Illustration: FIG. 41.--Ulceration of nineteen year's duration\
in a woman aet. 24, the subject of inherited syphilis, showing active\
ulceration, cicatricial contraction, and sabre-blade deformity of\
tibiae.]\
\
_Tertiary lesions of mucous membrane and of the submucous cellular\
tissue_ are met with chiefly in the tongue, nose, throat, larynx, and\
rectum. They originate as gummata or as gummatous infiltrations, which\
are liable to break down and lead to the formation of ulcers which may\
prove locally destructive, and, in such situations as the larynx, even\
dangerous to life. In the tongue the tertiary ulcer may prove the\
starting-point of cancer; and in the larynx or rectum the healing of the\
ulcer may lead to cicatricial stenosis.\
\
Tertiary lesions of the _bones and joints_, of the _muscles_, and of the\
_internal organs_, will be described under these heads. The part played\
by syphilis in the production of disease of arteries and of aneurysm\
will be referred to along with diseases of blood vessels.\
\
[Illustration: FIG. 42.--Tertiary Syphilitic Ulceration in region of\
Knee and on both Thumbs of woman aet. 37.]\
\
_Treatment._--The most valuable drugs for the treatment of the\
manifestations of the tertiary period are the arsenical preparations and\
the iodides of sodium and potassium. On account of their depressing\
effects, the latter are frequently prescribed along with carbonate of\
ammonium. The dose is usually a matter of experiment in each individual\
case; 5 grains three times a day may suffice, or it may be necessary to\
increase each dose to 20 or 25 grains. The symptoms of iodism which may\
follow from the smaller doses usually disappear on giving a larger\
amount of the drug. It should be taken after meals, with abundant water\
or other fluid, especially if given in tablet form. It is advisable to\
continue the iodides for from one to three months after the lesions for\
which they are given have cleared up. If the potassium salt is not\
tolerated, it may be replaced by the ammonium or sodium iodide.\
\
_Local Treatment._--The absorption of a subcutaneous gumma is often\
hastened by the application of a fly-blister. When a gumma has broken on\
the surface and caused an ulcer, this is treated on general principles,\
with a preference, however, for applications containing mercury or\
iodine, or both. If a wet dressing is required to cleanse the ulcer,\
black wash may be used; if a powder to promote dryness, one containing\
iodoform; if an ointment is indicated, the choice lies between the red\
oxide of mercury or the dilute nitrate of mercury ointment, and one\
consisting of equal parts of lanolin and vaselin with 2 per cent. of\
iodine. Deep ulcers, and obstinate lesions of the bones, larynx, and\
other parts may be treated by excision or scraping with the sharp spoon.\
\
#Second Attacks of Syphilis.#--Instances of re-infection of syphilis\
have been recorded with greater frequency since the more general\
introduction of arsenical treatment. A remarkable feature in such cases\
is the shortness of the interval between the original infection and the\
alleged re-infection; in a recent series of twenty-eight cases, this\
interval was less than a year. Another feature of interest is that when\
patients in the tertiary stage of syphilis are inoculated with the virus\
from lesions from these in the primary and secondary stage lesions of\
the tertiary type are produced.\
\
Reference may be made to the #relapsing false indurated chancre#,\
described by Hutchinson and by Fournier, as it may be the source of\
difficulty in diagnosis. A patient who has had an infecting chancre one\
or more years before, may present a slightly raised induration on the\
penis at or close to the site of his original sore. This relapsed\
induration is often so like that of a primary chancre that it is\
impossible to distinguish between them, except by the history. If there\
has been a recent exposure to venereal infection, it is liable to be\
regarded as the primary lesion of a second attack of syphilis, but the\
further progress shows that neither bullet-buboes nor secondary\
manifestations develop. These facts, together with the disappearance of\
the induration under treatment, make it very likely that the lesion is\
really gummatous in character.\
\
\
INHERITED SYPHILIS\
\
One of the most striking features of syphilis is that it may be\
transmitted from infected parents to their offspring, the children\
exhibiting the manifestations that characterise the acquired form of the\
disease.\
\
The more recent the syphilis in the parent, the greater is the risk of\
the disease being communicated to the offspring; so that if either\
parent suffers from secondary syphilis the infection is almost\
inevitably transmitted.\
\
While it is certain that either parent may be responsible for\
transmitting the disease to the next generation, the method of\
transmission is not known. In the case of a syphilitic mother it is most\
probable that the infection is conveyed to the foetus by the placental\
circulation. In the case of a syphilitic father, it is commonly believed\
that the infection is conveyed to the ovum through the seminal fluid at\
the moment of conception. If a series of children, one after the other,\
suffer from inherited syphilis, it is almost invariably the case that\
the mother has been infected.\
\
In contrast to the acquired form, inherited syphilis is remarkable for\
the absence of any primary stage, the infection being a general one from\
the outset. The spirochaete is demonstrated in incredible numbers in the\
liver, spleen, lung, and other organs, and in the nasal secretion, and,\
from any of these, successful inoculations in monkeys can readily be\
made. The manifestations differ in degree rather than in kind from those\
of the acquired disease; the difference is partly due to the fact that\
the virus is attacking developing instead of fully formed tissues.\
\
The virus exercises an injurious influence on the foetus, which in many\
cases dies during the early months of intra-uterine life, so that\
miscarriage results, and this may take place in repeated pregnancies,\
the date at which the miscarriage occurs becoming later as the virus in\
the mother becomes attenuated. Eventually a child is carried to full\
term, and it may be still-born, or, if born alive, may suffer from\
syphilitic manifestations. It is difficult to explain such vagaries of\
syphilitic inheritance as the infection of one twin and the escape of\
the other.\
\
_Clinical Features._--We are not here concerned with the severe forms of\
the disease which prove fatal, but with the milder forms in which the\
infant is apparently healthy when born, but after from two to six weeks\
begins to show evidence of the syphilitic taint.\
\
The usual phenomena are that the child ceases to thrive, becomes thin\
and sallow, and suffers from eruptions on the skin and mucous membranes.\
There is frequently a condition known as _snuffles_, in which the nasal\
passages are obstructed by an accumulation of thin muco-purulent\
discharge which causes the breathing to be noisy. It usually begins\
within a month after birth and before the eruptions on the skin appear.\
When long continued it is liable to interfere with the development of\
the nasal bones, so that when the child grows up there results a\
condition known as the "saddle-nose" deformity (Figs. 43 and 44).\
\
[Illustration: FIG. 43.--Facies of Inherited Syphilis.\
\
(From Dr. Byrom Bramwell's _Atlas of Clinical Medicine_.)]\
\
_Affections of the Skin._--Although all types of skin affection are met\
with in the inherited disease, the most important is a _papular_\
eruption, the papules being of large size, with a smooth shining top and\
of a reddish-brown colour. It affects chiefly the buttocks and thighs,\
the genitals, and other parts which are constantly moist. It is\
necessary to distinguish this specific eruption from a form of eczema\
which occurs in these situations in non-syphilitic children, the points\
that characterise the syphilitic condition being the infiltration of the\
skin and the coppery colour of the eruption. At the anus the papules\
acquire the characters of _condylomata_, also at the angles of the\
mouth, where they often ulcerate and leave radiating scars.\
\
_Affections of the Mucous Membranes._--The inflammation of the nasal\
mucous membrane that causes snuffles has already been referred to. There\
may be mucous patches in the mouth, or a stomatitis which is of\
importance, because it results in interference with the development of\
the permanent teeth. The mucous membrane of the larynx may be the seat\
of mucous patches or of catarrh, and as a result the child's cry is\
hoarse.\
\
_Affections of the Bones._--Swellings at the ends of the long bones, due\
to inflammation at the epiphysial junctions, are most often observed at\
the upper end of the humerus and in the bones in the region of the\
elbow. Partial displacement and mobility at the ossifying junction may\
be observed. The infant cries when the part is touched; and as it does\
not move the limb voluntarily, the condition is spoken of as _the\
pseudo-paralysis of syphilis_. Recovery takes place under\
anti-syphilitic treatment and immobilisation of the limb.\
\
Diffuse thickening of the shafts of the long bones, due to a deposit of\
new bone by the periosteum, is sometimes met with.\
\
[Illustration: FIG. 44.--Facies of Inherited Syphilis.]\
\
The conditions of the skull known as Parrot's nodes or bosses, and\
craniotabes, were formerly believed to be characteristic of inherited\
syphilis, but they are now known to occur, particularly in rickety\
children, from other causes. The _bosses_ result from the heaping up of\
new spongy bone beneath the pericranium, and they may be grouped\
symmetrically around the anterior fontanelle, or may extend along either\
side of the sagittal suture, which appears as a deep groove--the\
"natiform skull." The bosses disappear in time, but the skull may remain\
permanently altered in shape, the frontal and parietal eminences\
appearing unduly prominent. The term _craniotabes_ is applied when the\
bone becomes thin and soft, reverting to its original membranous\
condition, so that the affected areas dimple under the finger like\
parchment or thin cardboard; its localisation in the posterior parts of\
the skull suggests that the disappearance of the osseous tissue is\
influenced by the pressure of the head on the pillow. Craniotabes is\
recovered from as the child improves in health.\
\
Between the ages of three and six months, certain other phenomena may be\
met with, such as _effusion into the joints_, especially the knees;\
_iritis_, in one or in both eyes, and enlargement of the spleen and\
liver.\
\
In the majority of cases the child recovers from these early\
manifestations, especially when efficiently treated, and may enjoy an\
indefinite period of good health. On the other hand, when it attains the\
age of from two to four years, it may begin to manifest lesions which\
correspond to those of the tertiary period of acquired syphilis.\
\
#Later Lesions.#--In the skin and subcutaneous tissue, the later\
manifestations may take the form of localised gummata, which tend to\
break down and form ulcers, on the leg for example, or of a spreading\
gummatous infiltration which is also liable to ulcerate, leaving\
disfiguring scars, especially on the face. The palate and fauces may be\
destroyed by ulceration. In the nose, especially when the ulcerative\
process is associated with a putrid discharge--ozaena--the destruction of\
tissue may be considerable and result in unsightly deformity. The entire\
palatal portions of the upper jaws, the vomer, turbinate, and other\
bones bounding the nasal and oral cavities, may disappear, so that on\
looking into the mouth the base of the skull is readily seen. Gummatous\
disease is frequently observed also in the flat bones of the skull, in\
the bones of the hand, as syphilitic dactylitis, and in the bones of the\
forearm and leg. When the tibia is affected the disease is frequently\
bilateral, and may assume the form of gummatous ulcers and sinuses. In\
later years the tibia may present alterations in shape resulting from\
antecedent gummatous disease--for example, nodular thickenings of the\
shaft, flattening of the crest, or a more uniform increase in thickness\
and length of the shaft of the bone, which, when it is curved in\
addition, is described as the "sabre-blade" deformity. Among lesions of\
the viscera, mention should be made of gumma of the testis, which causes\
the organ to become enlarged, uneven, and indurated. This has even been\
observed in infants a few months old.\
\
Occasionally a syphilitic child suffers from a succession of these\
gummatous lesions with resulting ill-health, and, it may be, waxy\
disease of the internal organs; on the other hand, it may recover and\
present no further manifestations of the inherited taint.\
\
_Affections of the Eyes._--At or near puberty there is frequently\
observed an affection of the eyes, known as _chronic interstitial\
keratitis_, the relationship of which to inherited syphilis was first\
established by Hutchinson. It occurs between the ages of six and sixteen\
years, and usually affects one eye before the other. It commences as a\
diffuse haziness or steaminess near the centre of the cornea, and as it\
spreads the entire cornea assumes the appearance of ground glass. The\
chief complaint is of dimness of sight, which may almost amount to\
blindness, but there is little pain or photophobia; a certain amount of\
conjunctival and ciliary congestion is usually present, and there may be\
_iritis_ in addition. The cornea, or parts of it, may become of a deep\
pink or salmon colour from the formation in it of new blood vessels. The\
affection may last for from eighteen months to two years. Complete\
recovery usually takes place, but slight opacities, especially in the\
site of former salmon patches, may persist, and the disease occasionally\
relapses. _Choroiditis_ and _retinitis_ may also occur, and leave\
permanent changes easily recognised on examination with the\
ophthalmoscope.\
\
Among the rarer and more serious lesions of the inherited disease may be\
mentioned gummatous disease in the _larynx and trachea_, attended with\
ulceration and resulting in stenosis; and lesions of the _nervous\
system_ which may result in convulsions, paralysis, or dementia.\
\
In a limited number of cases, about the period of puberty there may\
develop _deafness_, which is usually bilateral and may become absolute.\
\
_Changes in the Permanent Teeth._--These affect specially the upper\
central incisors, which are dwarfed and stand somewhat apart in the gum,\
with their free edges converging towards one another. They are tapering\
or peg-shaped, and present at their cutting margin a deep semilunar\
notch. These appearances are commonly associated with the name of\
Hutchinson, who first described them. Affecting as they do the\
permanent teeth, they are not available for diagnosis until the child is\
over eight years of age. Henry Moon drew attention to a change in the\
first molars; these are reduced in size and dome-shaped through dwarfing\
of the central tubercle of each cusp.\
\
#Diagnosis of Inherited Syphilis.#--When there is a typical eruption on\
the buttocks and snuffles there is no difficulty in recognising the\
disease. When, however, the rash is scanty or is obscured by co-existing\
eczema, most reliance should be placed on the distribution of the\
eruption, on the brown stains which are left after it has passed off, on\
the presence of condylomata, and of fissuring and scarring at the angles\
of the mouth. The history of the mother relative to repeated\
miscarriages and still-born children may afford confirmatory evidence.\
In doubtful cases, the diagnosis may be aided by the Wassermann test and\
by noting the therapeutic effects of grey powder, which, in syphilitic\
infants, usually effects a marked and rapid improvement both in the\
symptoms and in the general health.\
\
While a considerable number of syphilitic children grow up without\
showing any trace of their syphilitic inheritance, the majority retain\
throughout life one or more of the following characteristics, which may\
therefore be described as _permanent signs of the inherited disease_:\
Dwarfing of stature from interference with growth at the epiphysial\
junctions; the forehead low and vertical, and the parietal and frontal\
eminences unduly prominent; the bridge of the nose sunken and rounded;\
radiating scars at the angles of the mouth; perforation or destruction\
of the hard palate; Hutchinson's teeth; opacities of the cornea from\
antecedent keratitis; alterations in the fundus oculi from choroiditis;\
deafness; depressed scars or nodes on the bones from previous gummata;\
"sabre-blade" or other deformity of the tibiae.\
\
#The Contagiousness of Inherited Syphilis.#--In 1837, Colles of Dublin\
stated his belief that, while a syphilitic infant may convey the disease\
to a healthy wet nurse, it is incapable of infecting its own mother if\
nursed by her, even although she may never have shown symptoms of the\
disease. This doctrine, which is known as _Colles' law_, is generally\
accepted in spite of the alleged occurrence of occasional exceptions.\
The older the child, the less risk there is of its communicating the\
disease to others, until eventually the tendency dies out altogether, as\
it does in the tertiary period of acquired syphilis. It should be\
added, however, that the contagiousness of inherited syphilis is denied\
by some observers, who affirm that, when syphilitic infants prove\
infective, the disease has been really acquired at or soon after birth.\
\
There is general agreement that the subjects of inherited syphilis\
cannot transmit the disease by inheritance to their offspring, and that,\
although they very rarely acquire the disease _de novo_, it is possible\
for them to do so.\
\
#Prognosis of Inherited Syphilis.#--Although inherited syphilis is\
responsible for a large but apparently diminishing mortality in infancy,\
the subjects of this disease may grow up to be as strong and healthy as\
their neighbours. Hutchinson insisted on the fact that there is little\
bad health in the general community that can be attributed to inherited\
syphilis.\
\
#Treatment.#--Arsenical injections are as beneficial in the inherited as\
in the acquired disease. An infant the subject of inherited syphilis\
should, if possible, be nursed by its mother, and failing this it should\
be fed by hand. In infants at the breast, the drug may be given to the\
mother; in others, it is administered in the same manner as already\
described--only in smaller doses. On the first appearance of syphilitic\
manifestations it should be given 0.05 grm, novarsenbillon, injected\
into the deep subcutaneous tissues every week for six weeks, followed by\
one year's mercurial inunction--a piece of mercurial ointment the size\
of a pea being inserted under the infant's binder. In older children the\
dose is proportionately increased. The general health should be improved\
in every possible direction; considerable benefit may be derived from\
the use of cod-liver oil, and from preparations containing iron and\
calcium. Surgical interference may be required in the destructive\
gummatous lesions of the nose, throat, larynx, and bones, either with\
the object of arresting the spread of the disease, or of removing or\
alleviating the resulting deformities. In children suffering from\
keratitis, the eyes should be protected from the light by smoked or\
coloured glasses, and the pupils should be dilated with atropin from\
time to time, especially in cases complicated with iritis.\
\
#Acquired Syphilis in Infants and Young Children.#--When syphilis is met\
with in infants and young children, it is apt to be taken for granted\
that the disease has been inherited. It is possible, however, for them\
to acquire the disease--as, for example, while passing through the\
maternal passages during birth, through being nursed or kissed by\
infected women, or through the rite of circumcision. The risk of\
infection which formerly existed by the arm-to-arm method of\
vaccination has been abolished by the use of calf lymph.\
\
The clinical features of the acquired disease in infants and young\
children are similar to those observed in the adult, with a tendency,\
however, to be more severe, probably because the disease is often late\
in being recognised and treated.\
\
\
\
\
CHAPTER X\
\
TUMOURS[2]\
\
\
Definition--Etiology--General characters of innocent and malignant\
    tumours. CLASSIFICATION OF TUMOURS: I. Connective-tissue tumours:\
    (1) _Innocent_: _Lipoma_, _Xanthoma_, _Chondroma_, _Osteoma_,\
    _Odontoma_, _Fibroma_, _Myxoma_, _Endothelioma_, etc.; (2)\
    _Malignant_: _Sarcoma_--II. Epithelial tumours: (1) _Innocent_:\
    _Papilloma_, _Adenoma_, _Cystic Adenoma_; (2) _Malignant_:\
    _Epithelioma_, _Glandular Cancer_, _Rodent Cancer_, _Melanotic\
    Cancer_--III. Dermoids--IV. Teratoma. Cysts: _Retention_,\
    _Exudation_, _Implantation_, _Parasitic_, _Lymphatic or Serous_.\
    Ganglion.\
\
[2] For the histology of tumours the reader is referred to a text-book\
of pathology.\
\
A tumour or neoplasm is a localised swelling composed of newly formed\
tissue which fulfils no physiological function. Tumours increase in size\
quite independently of the growth of the body, and there is no natural\
termination to their growth. They are to be distinguished from such\
over-growths as are of the nature of simple hypertrophy or local\
giantism, and also from inflammatory swellings, which usually develop\
under the influence of a definite cause, have a natural termination, and\
tend to disappear when the cause ceases to act.\
\
The _etiology of tumours_ is imperfectly understood. Various factors,\
acting either singly or in combination, may be concerned in their\
development. Certain tumours, for example, are the result of some\
congenital malformation of the particular tissue from which they take\
origin. This would appear to be the case in many tumours of blood\
vessels (angioma), of cartilage (chondroma), of bone (osteoma), and of\
secreting gland tissue (adenoma). The theory that tumours originate from\
foetal residues or "rests," is associated with the name of Cohnheim.\
These rests are supposed to be undifferentiated embryonic cells which\
remain embedded amongst fully formed tissue elements, and lie dormant\
until they are excited into active growth and give rise to a tumour.\
This mode of origin is illustrated by the development of dermoids from\
sequestrated portions of epidermis.\
\
Among the local factors concerned in the development of tumours,\
reference must be made to the influence of irritation. This is probably\
an important agent in the causation of many of the tumours met with in\
the skin and in mucous membranes--for example, cancer of the skin, of\
the lip, and of the tongue. The part played by injury is doubtful. It\
not infrequently happens that the development of a tumour is preceded by\
an injury of the part in which it grows, but it does not necessarily\
follow that the injury and the tumour are related as cause and effect.\
It is possible that an injury may stimulate into active growth\
undifferentiated tissue elements or "rests," and so determine the growth\
of a tumour, or that it may alter the characters of a tumour which\
already exists, causing it to grow more rapidly.\
\
The popular belief that there is some constitutional peculiarity\
concerned in the causation of tumours is largely based on the fact that\
certain forms of new growth--for example, cancer--are known to occur\
with undue frequency in certain families. The same influence is more\
striking in the case of certain innocent tumours--particularly multiple\
osteomas and lipomas--which are hereditary in the same sense as\
supernumerary or webbed fingers, and appear in members of the same\
family through several generations.\
\
\
INNOCENT AND MALIGNANT TUMOURS\
\
For clinical purposes, tumours are arbitrarily divided into two\
classes--the innocent and the malignant. The outstanding difference\
between them is, that while the evil effects of innocent tumours are\
entirely local and depend for their severity on the environment of the\
growth, malignant tumours wherever situated, in addition to producing\
similar local effects, injure the general health and ultimately cause\
death.\
\
_Innocent_, benign, or simple tumours present a close structural\
resemblance to the normal tissues of the body. They grow slowly, and are\
usually definitely circumscribed by a fibrous capsule, from which they\
are easily enucleated, and they do not tend to recur after removal. In\
their growth they merely push aside and compress adjacent parts, and\
they present no tendency to ulcerate and bleed unless the overlying skin\
or mucous membrane is injured. Although usually solitary, some are\
multiple from the outset--for example, fatty, fibrous, and bony tumours,\
warts, and fibroid tumours of the uterus. They produce no constitutional\
disturbance. They only threaten life when growing in the vicinity of\
vital organs, and then only in virtue of their situation--for example,\
death may result from an innocent tumour in the air-passage causing\
suffocation, in the intestine causing obstruction of the bowels, or in\
the vertebral canal causing pressure on the spinal medulla.\
\
_Malignant tumours_ usually show a marked departure from the structure\
and arrangement of the normal tissues of the body. Although the cells of\
which they are composed are derived from normal tissue cells, they tend\
to take on a lower, more vegetative form; they may be regarded as\
parasites living at the expense of the organism, multiplying\
indefinitely and destroying everything with which they come in contact.\
\
Malignant tumours grow more rapidly than innocent tumours, and tend to\
infiltrate their surroundings by sending out prolongations or offshoots;\
they are therefore liable to recur after an operation which is\
restricted to the removal of the main tumour. They are not encapsulated,\
although they may appear to be circumscribed by condensation of the\
surrounding tissues; they are rarely multiple at the outset, but show a\
marked tendency to spread to other parts of the body. Fragments of the\
parent tumour may become separated and be carried off in the lymph or\
blood-stream and deposited in other parts of the body, where they give\
rise to secondary growths. Malignant tumours tend to invade and destroy\
the overlying skin or mucous membrane, and thus give rise to bleeding\
ulcers; if the tumour tissue protrudes through the gap in the skin, it\
is said to _fungate_. In course of time they give rise to a condition of\
ill-health or _cachexia_, the patient becoming pale, sallow, feverish,\
and emaciated, probably as a result of chronic poisoning from the\
absorption of toxic products from the tumour. They ultimately destroy\
life, it may be by their local effects, such as ulceration and\
haemorrhage, by favouring the entrance of septic infection, by\
interfering with the function of organs which are essential to life, by\
cachexia, or by a combination of these effects.\
\
The situation of a malignant tumour exercises considerable influence on\
the rapidity, as well as on the mode, in which it causes death. Some\
cancers, such as that known as "rodent," show malignant features which\
are entirely local, while others, such as melanotic cancer, exhibit a\
malignancy characterised by rapid generalisation of growths throughout\
the body. Tumours that are structurally alike may show variations in\
malignancy, according to their situation and to the age of the patient,\
as well as to other factors which are as yet unknown.\
\
In attempting to arrive at a conclusion as to the innocence or\
malignancy of any tumour, too much reliance must not be placed on its\
histological features; its situation, rate of growth, and other clinical\
features must also be taken into consideration. It cannot be too\
emphatically stated that there is no hard-and-fast line between innocent\
and malignant growths; there is an indefinite transition from one to the\
other. The possibility of the transformation of a benign into a\
malignant tumour must be admitted. Such a transformation implies a\
change in the structure of the growth, and has been observed especially\
in fibrous and cartilaginous tumours, in tumours of the thyreoid gland,\
and in uterine fibroids. The alteration in character may take place\
under the influence of injury, prolonged or repeated irritation,\
incomplete removal of the benign tumour by operation, or the altered\
physiological conditions of the tissues which attend upon advancing\
years.\
\
After a tumour has been removed by operation it should as a routine\
measure be subjected to microscopical examination; the results are often\
instructive and sometimes other than what was expected.\
\
#Varieties of Tumours.#--In the following description, tumours are\
classified on an anatomical basis, taking in order first the\
connective-tissue group and subsequently those that originate in\
epithelium.\
\
\
INNOCENT CONNECTIVE-TISSUE TUMOURS\
\
#Lipoma.#--A lipoma is composed of fat resembling that normally present\
in the body. The commonest variety is the _subcutaneous lipoma_, which\
grows from the subcutaneous fat, and forms a soft, irregularly lobulated\
tumour (Fig. 45). The fat is arranged in lobules separated by\
connective-tissue septa, which are continuous with the capsule\
surrounding the tumour and with the overlying skin, which becomes\
dimpled or puckered when an attempt is made to pinch it up. As the fat\
is almost fluid at the body temperature, fluctuation can usually be\
detected. These tumours vary greatly in size, occur at all ages, grow\
slowly, and, while generally solitary, are sometimes multiple. They are\
most commonly met with on the shoulder, buttock, or back. In certain\
situations, such as the thigh and perineum, they tend to become\
pedunculated (Fig. 46).\
\
A fatty tumour is to be diagnosed from a cold abscess and from a cyst.\
The distinguishing features of the lipoma are the tacking down and\
dimpling of the overlying skin, the lobulation of the tumour, which is\
recognised when it is pressed upon with the flat of the hand, and, more\
reliable than either of these, the mobility, the tumour slipping away\
when pressed upon at its margin.\
\
[Illustration: FIG. 45.--Subcutaneous Lipoma showing lobulation.]\
\
The prognosis is more favourable than in any other tumour as it never\
changes its characters; the only reasons for its removal by operation\
are its unsightliness and its probable increase in size in the course of\
years. The operation consists in dividing the skin and capsule over the\
tumour and shelling it out. Care must be taken that none of the outlying\
lobules are left behind. If the overlying skin is damaged or closely\
adherent, it should be removed along with the tumour.\
\
[Illustration: FIG. 46.--Pedunculated Lipoma of Buttock of forty years'\
duration in a woman aet. 68.]\
\
_Multiple subcutaneous lipomas_ are frequently symmetrical, and in a\
certain group of cases, met with chiefly in women, pain is a prominent\
symptom, hence the term _adiposis dolorosa_ (Dercum). These multiple\
tumours show little or no tendency to increase in size, and the pain\
which attends their development does not persist.\
\
In the neck, axilla, and pubes a diffuse overgrowth of the subcutaneous\
fat is sometimes met with, forming symmetrical tumour-like masses, known\
as _diffuse lipoma_. As this is not, strictly speaking, a tumour, the\
term _diffuse lipomatosis_ is to be preferred. A similar condition was\
described by Jonathan Hutchinson as being met with in the domestic\
animals. If causing disfigurement, the mass of fat may be removed by\
operation.\
\
[Illustration: FIG. 47.--Diffuse Lipomatosis of Neck.]\
\
_Lipoma in other Situations._--The _periosteal lipoma_ is usually\
congenital, and is most often met with in the hand; it forms a\
projecting lobulated tumour, which, when situated in the palm, resembles\
an angioma or a lymphangioma. The _subserous lipoma_ arises from the\
extra-peritoneal fat in the posterior abdominal wall, in which case it\
tends to grow forwards between the layers of the mesentery and to give\
rise to an abdominal tumour; or it may grow from the extra-peritoneal\
fat in the anterior abdominal wall and protrude from one of the hernial\
openings or through an abnormal opening in the parietes, constituting a\
_fatty hernia_. A _subsynovial lipoma_ grows from the fat surrounding\
the synovial membrane of a joint, and projects into its interior, giving\
rise to the symptoms of loose body. Lipomas are also met with growing\
from the adipose connective tissue _between or in the substance of\
muscles_, and, when situated beneath the deep fascia, such as the fascia\
lata of the thigh, the characteristic signs are obscured and a\
differential diagnosis is difficult. It may be differentiated from a\
cold abscess by puncture with an exploring needle.\
\
[Illustration: FIG. 48.--Zanthoma of Hands in a girl aet. 14, showing\
multiple subcutaneous tumours (cf. Fig. 49).\
\
(Sir H. J. Stiles' case.)]\
\
#Zanthoma# is a rare but interesting form of tumour, composed of a\
fibrous and fatty tissue, containing a granular orange-yellow pigment,\
resembling that of the corpus luteum. It originates in the corium and\
presents two clinical varieties. In the first of these, it occurs in the\
form of raised yellow patches, usually in the skin of the eyelids of\
persons after middle life, and in many instances is associated with\
chronic jaundice; the patches are often symmetrical, and as they\
increase in size they tend to fuse with another.\
\
The second form occurs in children and adolescents; it may affect\
several generations of the same family, and is often multiple, there\
being a combination of thickened yellow patches of skin and projecting\
tumours, some of which may attain a considerable size (Figs. 48 and 49).\
On section, the tumour tissue presents a brilliant orange or saffron\
colour.\
\
There is no indication for removing the tumours unless for the deformity\
which they cause; exposure to the X-rays is to be preferred to\
operation.\
\
[Illustration: FIG. 49.--Zanthoma showing Subcutaneous Tumours on\
Buttocks. From same patient as Fig. 48.]\
\
#Chondroma.#--A chondroma is mainly composed of cartilage. Processes of\
vascular connective tissue pass in between the nodules of cartilage\
composing the tumour from the fibrous capsule which surrounds it. On\
section it is of a greyish-blue colour and semi-translucent. The tumour\
is firm and elastic in consistence, but certain portions may be densely\
hard from calcification or ossification, while other portions may be\
soft and fluctuating as a result of myxomatous degeneration and\
liquefaction. These tumours grow slowly and painlessly, and may surround\
nerves and arteries without injuring them. They may cause a deep hollow\
in the bone from which they originate. All intermediate forms between\
the innocent chondroma and the malignant chondro-sarcoma are met with.\
Chondroma may occur in a multiple form, especially in relation to the\
phalanges and metacarpal bones. When growing in the interior of a bone\
it causes a spindle-shaped enlargement of the shaft, which in the case\
of a phalanx or metacarpal bone may resemble the dactylitis resulting\
from tubercle or syphilis. A chondroma appears as a clear area in a\
skiagram.\
\
A _skiagram_ of a bone in which there is a chondroma shows a clear\
rounded area in the position of the tumour, which must be differentiated\
from similar clear areas due to other kinds of tumour, especially the\
myeloma; when it has undergone calcification or ossification, it gives a\
shadow as dark as bone.\
\
[Illustration: FIG. 50.--Chondroma growing from infraspinous fossa of\
Scapula.]\
\
[Illustration: FIG. 51.--Chondroma of Metacarpal Bone of Thumb.]\
\
_Treatment._--In view of the unstable quality of the chondroma,\
especially of its liability to become malignant, it should be removed as\
soon as it is recognised. In those projecting from the surface of a\
bone, both the tumour and its capsule should be removed. If in the\
interior, a sufficient amount of the cortex should be removed to allow\
of the tumour being scraped out, and care must be taken that no nodules\
of cartilage are left behind. In multiple chondromas of the hand, when\
the fingers are crippled and useless, exposure to the X-rays should be\
given a trial, and in extreme cases the question of amputation may have\
to be considered. When a cartilaginous tumour takes on active growth, it\
must be treated as malignant.\
\
The chondromas that are met with at the ends of the long bones in\
children and young adults form a group by themselves. They are usually\
related to the epiphysial cartilage, and it was suggested by Virchow\
that they take origin from islands of cartilage which have not been used\
up in the process of ossification. They are believed to occur more\
frequently in those who have suffered from rickets. They have no\
malignant tendencies and tend to undergo ossification concurrently with\
the epiphysial cartilage from which they take origin, and constitute\
what are known as _cartilaginous exostoses_. These are sometimes met\
with in a multiple form, and may occur in several generations of the\
same family. They are considered in greater detail in the chapter\
dealing with tumours of bone.\
\
Minute nodules of cartilage sometimes form in the synovial membrane of\
joints and lining of tendon sheaths and bursae: they tend to become\
detached from the membrane and constitute loose bodies; they also\
undergo a variable amount of calcification and ossification, so as to be\
visible in skiagrams. They are further considered with loose bodies in\
joints.\
\
Cartilaginous tumours in the parotid, submaxillary gland, and testicle\
belong to a class of "mixed tumours" that will be referred to later.\
\
#Osteoma.#--The true osteoma is composed of bony tissue, and originates\
from the skeleton. Two varieties are recognised--the spongy or\
cancellous, and the ivory or compact. The _spongy_ or _cancellous\
osteoma_ is really an ossified chondroma, and is met with at the ends of\
the long bones (Fig. 52). From the fact that it projects from the\
surface of the bone it is often spoken of as an _exostosis_. It grows\
slowly, and rarely causes any discomfort unless it presses upon a\
nerve-trunk or upon a bursa which has developed over it. The Rontgen\
rays show a dark shadow corresponding to the ossified portion of the\
tumour, and continuous with that of the bone from which it is growing\
(Fig. 138). Operative interference is only indicated when the tumour is\
giving rise to inconvenience. It is then removed, its base or neck being\
divided by means of the chisel. The multiple variety of osteoma is\
considered with the diseases of bone.\
\
The bony outgrowth from the terminal phalanx of the great toe--known as\
the _subungual exostosis_--is described and figured on p. 404. Bony\
projections or "spurs" sometimes occur on the under surface of the\
calcaneus, and, projecting downwards and forwards from the greater\
process, cause pain on putting the heel to the ground.\
\
[Illustration: FIG. 52.--Cancellous Osteoma of lower end of Femur.]\
\
The _ivory_ or _compact osteoma_ is composed of dense bone, and usually\
grows from the skull. It is generally sessile and solitary, and may grow\
into the interior of the skull, into the frontal sinus, into the cavity\
of the orbit or nose, or may fill up the external auditory meatus,\
causing most unsightly deformity and interference with sight, breathing,\
and hearing.\
\
Bony formations occur in _muscles and tendons_, especially at their\
points of attachment to the skeleton, and are known as false exostoses;\
they are described with the diseases of muscles.\
\
#Odontoma.#--An odontoma is composed of dental tissues in varying\
proportions and different degrees of development, arising from\
tooth-germs or from teeth still in process of growth (Bland Sutton).\
Odontomas resemble teeth in so far that during their development they\
remain hidden below the mucous membrane and give no evidence of their\
existence. There then succeeds, usually between the twentieth and\
twenty-fifth years, an eruptive stage, which is often attended with\
suppuration, and this may be the means of drawing attention to the\
tumour. Following Bland Sutton, several varieties of odontoma may be\
distinguished according to the part of the tooth-germ concerned in their\
formation.\
\
The _epithelial odontoma_ is derived from persistent portions of the\
epithelium of the enamel organ, and constitutes a multilocular cystic\
tumour which is chiefly met with in the mandible. The cystic spaces of\
the tumour contain a brownish glairy fluid. These tumours have been\
described by Eve under the name of multilocular cystic epithelial\
tumours of the jaw.\
\
The _follicular odontoma_, also known as a _dentigerous cyst_, is\
derived from the distension of a tooth follicle. It constitutes a cyst\
containing a viscid fluid, and an imperfectly formed tooth is often\
found embedded in its wall. The cyst usually forms in relation to one of\
the permanent molars, and may attain considerable dimensions.\
\
The _fibrous odontoma_ is the result of an overgrowth of fibrous tissue\
surrounding the tooth sac, which encapsulates the tooth and prevents its\
eruption. The thickened tooth sac is usually mistaken for a fibrous\
tumour, until, after removal, the tooth is recognised in its interior.\
\
_Composite Odontoma._--This is a convenient term to apply to certain\
hard dental tumours which are met with in the jaws, and consist of\
enamel, dentine, and cement. The tumour is to be regarded as being\
derived from an abnormal growth of all the elements of a tooth germ, or\
of two or more tooth germs, indiscriminately fused with one another. It\
may appear in childhood, and form a smooth unyielding tumour, often of\
considerable size, replacing the corresponding permanent tooth. It may\
cause a purulent discharge, and in some cases it has been extruded after\
sloughing of the overlying soft parts. Many examples of this variety of\
odontoma, growing in the nasal cavity or in the maxillary sinus, have\
been erroneously regarded as osteomas even after removal.\
\
On section, the tumour is usually laminated, and is seen to consist\
mainly of dentine with a partial covering of enamel and cement.\
\
_Diagnosis._--Odontomas are often only diagnosed after removal. When\
attended with suppuration, the condition has been mistaken for disease\
of the jaw. Fibrous odontomas have been mistaken for sarcoma, and\
portions of the maxilla removed unnecessarily. Any circumscribed tumour\
of the jaw, particularly when met with in a young adult, should suggest\
the possibility of an odontoma. Skiagrams often give useful information\
both for diagnosis and for treatment.\
\
_Treatment._--The solid varieties of odontoma can usually be shelled out\
after dividing the overlying soft parts. In the follicular variety, it\
is usually sufficient to excise a portion of the wall, scrape out the\
interior, and remove any tooth that may be present. The cavity is then\
packed and allowed to heal from the bottom.\
\
#Fibroma.#--A fibroma is a tumour composed of fibrous connective tissue.\
A distinction may be made between the _soft fibroma_, which is\
comparatively rich in cells and blood vessels, and in which the fibres\
are arranged loosely; and the _hard fibroma_, which is composed of\
closely packed bundles of fibres often arranged in a concentric fashion\
around the blood vessels. The cut surface of the soft fibroma presents a\
pinkish-white, fleshy appearance, resembling the slowly growing forms of\
sarcoma; that of a hard fibroma presents a dry, glistening appearance,\
aptly compared to watered silk. The soft variety grows much more rapidly\
than the hard. In certain fibromas--in those, for example, which grow\
from the periosteum of the base of the skull and project into the\
naso-pharynx--the blood vessels are dilated into sinuses and have no\
proper sheaths; they therefore tend to remain open when divided, and to\
bleed excessively. Transition forms between soft fibroma and sarcoma are\
met with, so that in operating for their removal it is safer to take\
away the capsule along with the tumour, and the patient should be kept\
under observation in view of the risk of recurrence.\
\
The skin--especially the skin of the buttock--is one of the favourite\
seats of fibroma, and it may occur in a multiple form. It is met with\
also in the subcutaneous and intermuscular cellular tissue, and in the\
abdominal wall, where it sometimes attains considerable dimensions.\
Various forms of fibroma are met with in the mamma and are described\
with diseases of that organ. The fibrous overgrowths in the skin, known\
as _keloid_ and _molluscum fibrosum_, and those met with in the _sheaths\
of nerves_, are described elsewhere. Fibroid tumours of the uterus are\
described with myoma.\
\
_Diffuse fibroma_ or _Fibromatosis_, analogous to lipomatosis, is met\
with in the connective tissue of the skin and sheaths of nerves, and\
constitutes one form of neuro-fibromatosis; a similar change is also met\
with in the stomach and colon.\
\
#Myxoma.#--A myxoma is composed of tissue of a soft gelatinous,\
semifluid consistence. The pure myxoma is extremely rare, and\
clinically resembles the lipoma. Myxomatous tissue is, however,\
frequently found in other connective-tissue tumours as a result of\
degeneration, for example, in cartilaginous tumours and in sarcomas.\
Myxomatous tissue is also a prominent constituent of the "innocent\
parotid tumour." Mucous polypus of the nose, which is often described as\
a myxoma, is merely a pendulous process of oedematous mucous membrane.\
\
[Illustration: FIG. 53.--Myeloma of Shaft of Humerus, causing\
pathological fracture. (Mr. J. W. Struthers' case.)\
\
(The unusual site of the tumour is to be noted.)]\
\
#Myeloma.#--A myeloma is composed of large multinuclear giant cells\
surrounded by round and spindle cells. The cut surface of the tumour\
presents a deep red or maroon colour. While occasionally met with in\
tendon sheaths and bursae, and is then of an orange-yellow colour, the\
myeloma occurs most frequently in the cancellous tissue at the ends of\
the long bones, its favourite site being the upper end of the tibia.\
Although formerly classified as a sarcoma, it is the exception for it to\
present malignant features, and it can usually be extirpated by local\
measures without fear of recurrence. The diagnosis, X-ray appearances,\
and the method of removal are considered with the diseases of bone.\
Sometimes the myeloma is met with in multiple form in the skeleton, in\
association with an unusual form of protein in the urine (Bence Jones).\
\
#Myoma.#--A myoma is composed of non-striped muscle fibres. A pure myoma\
is very rare, and is met with in organs possessed of non-striped muscle,\
such as the stomach, intestine, urinary bladder, and prostate. In the\
uterus, which is the most common situation, these tumours contain a\
considerable admixture of fibrous tissue, and are known as _fibroids_ or\
_fibro-myomas_. They present on section a fasciculated appearance, which\
may resemble that of a section of balls of cotton (Fig. 54). They are\
encapsulated and vascular, frequently attain a large size, and may be\
single or multiple. While they may occasion neither inconvenience nor\
suffering, they frequently give rise to profuse haemorrhage from the\
uterus, and may cause serious symptoms by pressing injuriously on the\
ureters or the intestine, or by complicating pregnancy and parturition.\
\
The #Rhabdomyoma# is an extremely rare form of tumour, met with in the\
kidney, uterus, and testicle. It contains striped muscle fibres, and is\
supposed to originate from a residue of muscular tissue which has become\
sequestrated during development.\
\
[Illustration: FIG. 54.--Fibro-myoma of Uterus.\
\
(Anatomical Museum, University of Edinburgh.)]\
\
#Glioma.#--A glioma is a tumour composed of neuroglia. It is met with\
exclusively in the central nervous system, retina, and optic nerve. It\
is a slowly growing, soft, ill-defined tumour, which displaces the\
adjacent nerve centres and nerve tracts, and is liable to become the\
seat of haemorrhage and thus to give rise to pressure symptoms resembling\
apoplexy. The glioma of the retina tends to grow into the vitreous\
humour and to perforate the globe. It is usually of the nature of a\
glio-sarcoma and is highly malignant.\
\
#Endotheliomas# take origin from the endothelium of lymph vessels and\
blood vessels, and serous cavities. They show great variation in type,\
partly because of the number of different kinds of endothelium from\
which they are derived, and partly because the new connective tissue\
which is formed is liable to undergo transformation into other tissues.\
They may be soft or hard, solid or cystic, diffuse or circumscribed;\
they grow very slowly, and are almost always innocent, although\
recurrence has been occasionally observed. Cases of multiple\
endotheliomata of the skin have recently been described by Wise.\
\
_Angioma_, _lymphangioma_, and _neuroma_ are described with the disease\
of the individual tissues.\
\
\
MALIGNANT CONNECTIVE-TISSUE TUMOURS--SARCOMA\
\
The term sarcoma is applied to any connective-tissue tumour which\
exhibits malignant characters. The essential structural feature is the\
predominance of the cellular elements over the intercellular substance\
or stroma, in which respect a sarcoma resembles the connective tissue of\
the embryo. The typical sarcoma consists chiefly of immature or\
embryonic connective tissue. It most frequently originates from fascia,\
intermuscular connective tissue, periosteum, bone-marrow, and skin, and\
forms a rounded or nodulated tumour which appears to be encapsulated,\
but the capsule merely consists of the condensed surrounding tissues,\
and usually contains sarcomatous elements. The consistence of the tumour\
depends on the nature and amount of the stroma, and on the presence of\
degenerative changes. The softer medullary forms are composed almost\
exclusively of cells; while the harder forms--such as the fibro-,\
chondro-, and osteo-sarcoma--are provided with an abundant stroma and\
are relatively poor in cells. Degenerative changes may produce areas of\
softening or liquefaction which result in the formation of cystic\
cavities in the interior of the tumour. The colour depends on the amount\
of blood in the tumour, and on the presence of the products of\
degeneration.\
\
The blood vessels are usually represented by mere chinks or spaces\
between the cells. This peculiarity accounts for the facility with which\
haemorrhage takes place into the substance of the tumour, the persistence\
of the bleeding when it is incised or ulcerates through the skin, and\
the readiness with which the sarcomatous cells are carried off and\
infect distant parts through the blood-stream. Sarcomas are devoid of\
lymphatics, and unless originating in lymphatic structures--for example,\
in the tonsil--they rarely infect the lymph glands. Minute portions of\
the tumour grow into the small veins, and, becoming detached, are\
transported by the blood-current to distant organs, where they are\
arrested in the capillaries and give rise to secondary growths. These\
are most frequently situated in the lungs, except when the primary\
growth lies within the territory of the portal circulation, in which\
case they occur in the liver. The secondary growths closely resemble the\
parent tumour. Sarcoma may invade an adjacent vein on such a scale that\
if the invading portion becomes detached it may constitute a dangerous\
embolus. This may be observed in sarcoma of the kidney, the growth\
taking place along the renal vein until it projects into the vena cava.\
\
[Illustration: FIG. 55.--Recurrent Sarcoma of Sciatic Nerve in a woman\
aet. 27. Recurrence twenty months after removal of primary growth.]\
\
In its growth, a sarcoma compresses and destroys neighbouring parts,\
surrounds vessels and nerves, and may lead to destruction of the skin,\
either by invading it, or more commonly by causing sloughing from\
pressure. Inflammatory and suppurative changes may take place as a\
result of pyogenic infection following upon sloughing of the overlying\
skin or upon an exploratory incision. Once the skin is broken the tumour\
fungates through the opening. Sarcomas vary in malignancy, especially as\
regards rapidity of growth and capacity for dissemination. Certain of\
them, such as the so-called "recurrent fibroid of Paget," grow\
comparatively slowly, and are only malignant in the sense that they tend\
to recur locally after removal; others--especially the more cellular\
ones--grow with extreme rapidity, and are early disseminated throughout\
the body, resembling in these respects the most malignant forms of\
cancer. They are usually solitary in the first instance, although\
primary multiple growths are occasionally met with in the skin and in\
the bones.\
\
Many varieties of sarcoma are recognised, according to its structural\
peculiarities. Thus, in virtue of the size and character of the cells,\
we have the _small round-celled_ and the _large round-celled_ sarcoma,\
the _small_ and the _large spindle-celled_, the _giant-celled_ and the\
_mixed-celled_ sarcoma. The _lympho-sarcoma_ presents a structure\
similar to that of lymph-follicular tissue, and the _alveolar sarcoma_\
an arrangement of cells in alveoli resembling that seen in cancers. When\
there is a considerable amount of intercellular fibrous tissue, the\
tumour is called a _fibro-sarcoma_.\
\
[Illustration: FIG. 56.--Fungating Sarcoma of Arm.\
\
(Dr. J. M'Watt's case.)]\
\
The term _lymphangio-sarcoma_ is applied when the cells of the tumour\
are derived from the endothelium of lymph spaces and vessels. The\
_angio-sarcomas_ are those in which blood vessels form a prominent\
element in the structure of the tumour. They are sometimes derived from\
innocent angiomas, and they may be so vascular as to pulsate and on\
auscultation yield a blowing murmur like an aneurysm. The\
_glio-sarcoma_, _myxo-sarcoma_, _chondro-sarcoma_, and _myo-sarcoma_ are\
mixed forms which usually develop in pre-existing innocent tumours. The\
_osteo-sarcoma_ is characterised by the formation in the tumour of bone,\
the medullary spaces being occupied by sarcomatous cells in place of\
marrow. The _osteoid sarcoma_ is characterised by the formation of a\
tissue resembling bone but deficient in lime salts, and the _petrifying\
sarcoma_ by the formation of calcified areas in the stroma. These\
varieties, although met with chiefly in the bones, may occur in soft\
tissues such as muscle, and in such organs as the mamma. The pigmented\
varieties include the _chloroma_, which is of a light-green colour, and\
the _melanotic sarcoma_, which is brown or black. The _psammoma_ is a\
sarcoma containing a material resembling sand; it is chiefly met with in\
the membranes of the brain. The _chordoma_ is a rare form of tumour\
originating from the remains of the notochord in the region of the\
spheno-occipital synchondrosis or in the sacro-coccygeal region.\
\
_Diagnosis of Sarcoma._--A sarcoma is to be differentiated from an\
inflammatory swelling such as results from tubercle, actinomycosis, or\
syphilis, from an innocent tumour, and from a cancer. The points on\
which the diagnosis is founded are discussed with the different tissues\
and organs.\
\
_Treatment._--The removal of the tumour by operation is the most\
reliable method of treatment; in order to be successful it must be\
undertaken before dissemination has taken place, and a considerable area\
of healthy tissue beyond the apparent margin of the growth must be\
removed, and in tumours near the surface of the body, the overlying skin\
also.\
\
In order to prevent recurrence, a tube of _radium_, to which a silk\
thread is attached, is inserted into the space from which the tumour was\
removed; the thread is brought out at the drain-opening, and at the end\
of a week or ten days the tube of radium is removed by pulling on the\
thread. Radium causes a reaction in the tissues attended with exudation\
from the vessels, for the escape of which provision must be made. If\
radium is not available, the affected area is repeatedly exposed to the\
action of the _X-rays_ as soon as the wound has healed. The employment\
of these measures has diminished to a remarkable degree the recurrence\
of sarcoma after operation.\
\
It will readily be understood that the less thoroughly or radically the\
growth has been removed, the more do we depend upon radium or the X-rays\
for bringing about a permanent cure, and that in advanced cases of\
sarcoma and in cases in which, on account of their anatomical situation,\
removal by operation is necessarily incomplete, the prospect of cure is\
still more dependent on the use of radium or of the X-rays. Finally,\
there are cases in which removal by operation is impossible, the\
so-called _inoperable sarcoma_; a tube of radium, to which a silk thread\
is attached, is inserted into the substance of the tumour, either\
through an opening made by a large trocar, or, when necessary, by open\
dissection. A second tube of radium is placed upon the skin over the\
tumour and is secured there by a stitch or by a strip of plaster, thus\
securing a cross-fire action of the radium rays, both from within and\
without, as this is found to be much more efficacious in destroying or\
inhibiting the cellular elements of the growth. The tubes of radium are\
left _in situ_ for from eight to fourteen days, according to the power\
of the radium employed, but are moved about every second day or so in\
order that every part of the tumour may be efficiently radiated. If the\
tumour shrinks in size after the use of radium and becomes operable, it\
should be removed before time is given it to resume its growth. It will\
depend upon the subsequent course of the disease, whether or not a\
second, or it may be even a third, application of radium will be\
required.\
\
Where neither radium nor X-rays is available or applicable, recourse may\
be had to the injection of Coley's fluid, a preparation containing the\
mixed toxins of the streptococcus of erysipelas and the bacillus\
prodigiosus; or of selenium.\
\
\
EPITHELIAL TUMOURS\
\
An excessive and erratic growth of epithelium is the essential and\
distinguishing feature of these tumours. The innocent forms are the\
papilloma and the adenoma; the malignant, the carcinoma or cancer.\
\
#Papilloma.#--A papilloma is a tumour which projects from a cutaneous or\
mucous surface, and consists of a central axis of vascular fibrous\
tissue with a covering of epithelium resembling that of the surface from\
which the tumour grows. In the papillomas of the skin--commonly known as\
_warts_--the covering consists of epidermis; in those growing from\
mucous surfaces it consists of the epithelium covering the mucous\
membrane. When the surface epithelium projects as filiform processes,\
the tumour is called a _villous papilloma_, the best-known example of\
which is met with in the urinary bladder. Papillomatous growths are\
also met with in the larynx, in the ducts of the breast, and in the\
interior of certain cystic tumours of the breast and of the ovary.\
Although papillomas are primarily innocent, they may become the\
starting-point of cancer, especially in persons past middle life and if\
the papilloma has been subjected to irritation and has ulcerated. The\
clinical features and treatment of the various forms of papilloma are\
considered with the individual tissues and organs.\
\
#Adenoma.#--An adenoma is a tumour constructed on the type of, and\
growing in connection with, a secreting gland. In the substance of such\
glands as the mamma, parotid, thyreoid, and prostate, adenomas are met\
with as encapsulated tumours. When they originate from the glands of the\
skin or of a mucous membrane, they tend to project from the surface, and\
form pedunculated tumours or polypi.\
\
Adenomas may be single or multiple, and they vary greatly in size. The\
tumour is seldom composed entirely of gland tissue; it usually contains\
a considerable proportion of fibrous tissue, and is then called a\
_fibro-adenoma_. When it contains myxomatous tissue it is called a\
_myxo-adenoma_, and when the gland spaces of the tumour become distended\
with accumulated secretion, a _cystic adenoma_, the best examples of\
which are met with in the mamma and ovary. A characteristic feature of\
the cystic variety is the tendency the tumour tissue exhibits to project\
into the interior of the cysts, constituting what are known as\
_intracystic growths_. They are essentially innocent, but intracystic\
growths, especially in the mamma of women over fifty, should be regarded\
with suspicion and therefore should be removed on radical lines.\
Transition forms between adenoma and carcinoma are also met with in the\
rectum and large intestine, and these should be treated on the same\
lines as cancer.\
\
\
CARCINOMA OR CANCER\
\
A cancer is a malignant tumour which originates in epithelium. The\
cancer cells are derived by proliferation from already existing\
epithelium, and they invade the sub-epithelial connective tissue in the\
form of simple or branching columns. These columns are enclosed in\
spaces--termed alveoli--which are probably dilated lymph spaces, and\
which communicate freely with the lymph vessels. The cells composing the\
columns and filling the alveoli vary with the character of the\
epithelium in which the cancer originates. The malignancy of cancer\
depends on the tendency which the epithelium has of invading the tissues\
in its neighbourhood, and on the capacity of the cells, when\
transported elsewhere by the lymph or blood-stream, of giving rise to\
secondary growths.\
\
Cancer may arise on any surface covered by epithelium or in any of the\
secreting glands of the body, but it is much more common in some\
situations than in others. It is frequently met with, for example, in\
the skin, in the stomach and large intestine, in the breast, the uterus,\
and the external genitals; less frequently in the gall-bladder, larynx,\
thyreoid, prostate, and urinary bladder.\
\
Tissues appear to be most liable to cancer when, having attained\
maturity, they enter upon the phase of decadence or involution, and this\
phase is reached by different tissues at different periods. It is not so\
much, therefore, the age of the person in whom it occurs, as the age of\
the tissue in which it arises, that determines the maximum incidence of\
cancer. Cancer of the stomach appears and attains a maximum frequency\
earlier than cancer of the skin; cancer of the uterus and mamma is more\
frequent towards the decline of reproductive activity than in the later\
years of life; rectal cancer is not infrequently met with during the\
second and third decades. There is evidence that the irritation caused\
by alcohol and tobacco plays a part in the causation of cancer, in the\
fact that a large proportion of those who become the subjects of cancer\
of the mouth are excessive drinkers and smokers.\
\
A cancer may appear as a papillary growth on a mucous or a skin surface,\
as a nodule in the substance of an organ, or as a diffuse thickening of\
a tubular organ such as the stomach or intestine. The absence of\
definition in cancerous tumours explains the difficulty of completely\
removing them by surgical measures, and has led to the practice of\
complete extirpation of cancerous organs wherever this is possible. The\
boundaries of the affected organ, moreover, are frequently transgressed\
by the disease, and the epithelial infiltration implicates the\
surrounding parts. In cancer of the breast, for example, the disease\
often extends to the adjacent skin, fat, and muscle; in cancer of the\
lip or tongue, to the mandible; in cancer of the uterus or intestine, to\
the investing peritoneum.\
\
In addition to its tendency to infiltrate adjacent tissues and organs,\
cancer is also liable to give rise to _secondary growths_. These are\
most often met with in the nearest lymph glands; those in the neck, for\
example, becoming infected from cancer of the lip, tongue, or throat;\
those in the axilla, from cancer of the breast; those along the\
curvatures of the stomach, from cancer of the pylorus; and those in the\
groin, from cancer of the external genitals. In lymph vessels the cancer\
cells may merely accumulate so as to fill the lumen and form indurated\
cords, or they may proliferate and give rise to secondary nodules along\
the course of the vessels. When the lymphatic network in the skin is\
diffusely infected, the appearance is either that of a multitude of\
secondary nodules or of a diffuse thickening, so that the skin comes to\
resemble coarse leather. On the wall of the chest this condition is\
known as _cancer en cuirasse_. Although the cancer cells constantly\
attack the walls of the adjacent veins and spread into their interior at\
a comparatively early period, secondary growths due to dissemination by\
the blood-stream rarely show themselves clinically until late in the\
course of the disease. It is probable that many of the cancer cells\
which are carried away in the blood or lymph stream undergo necrosis and\
fail to give rise to secondary growths. Secondary growths present a\
faithful reproduction of the structure of the primary tumour. Apart from\
the lymph glands, the chief seats of secondary growths are the liver,\
lungs, serous membranes, and bone marrow.\
\
It is generally believed that the secondary growths in cancer that\
develop at a distance from the primary tumour, those, for example, in\
the medullary canal of the femur or in the diploe of the skull occurring\
in advanced cases of cancer of the breast, are the result of\
dissemination of cancer cells by way of the blood-stream and are to be\
regarded as emboli. Sampson Handley disagrees with this view; he\
believes that the dissemination is accomplished in a more subtle way,\
namely, by the actual growth of cancer cells along the finer vessels of\
the lymph plexuses that ramify in the deep fascia, a method of spread\
which he calls _permeation_. It is maintained also that permeation\
occurs as readily against the lymph stream as with it. He compares the\
spread of cancer to that of an invisible annular ringworm. The growing\
edge extends in a wider and wider circle, within which a healing process\
may occur, so that the area of permeation is a ring, rather than a disc.\
Healing occurs by a process of "peri-lymphatic fibrosis," but as the\
natural process of healing may fail at isolated points, nodules of\
cancer appear, which, although apparently separate from the primary\
growth, have developed in continuity with it, peri-lymphatic fibrosis\
having destroyed the cancer chain connecting the nodule with the primary\
growth. This centrifugal spread of cancer is clearly seen in the\
distribution of the subcutaneous secondary nodules so frequently met\
with in the late stages of mammary cancer. The area within which the\
secondary nodules occur is a circle of continually increasing diameter\
with the primary growth in the centre.\
\
In the rare cases in which the skin of the greater part of the body is\
affected, the nodules rarely appear below the level of the deltoid or\
the middle third of the thigh, the patient dying before the spread can\
reach the distal portions of the limbs.\
\
Handley argues against the embolic origin of the metastases in the bones\
because of the rarity of these in the bones of the distal parts of the\
limbs, because of the fact that secondary cancer of the femur nearly\
always commences in the upper third of the shaft, which harmonises with\
the intimate connection of the deep fascia with the periosteum over the\
great trochanter, thus favouring invasion of the bone marrow when\
permeation has spread thus far. He claims support for the permeation\
theory from the fact that the humerus is rarely involved below the\
insertion of the deltoid, and that spontaneous fracture of the femur is\
three times more common on the side on which the breast cancer is\
situated.\
\
The tumour tissue may undergo necrosis, and when the overlying skin or\
mucous membrane gives way an ulcer is formed. The margins of a\
_cancerous ulcer_ (Fig. 57) are made up of tumour tissue which has not\
broken down. Usually they are irregular, nodularly thickened or\
indurated; sometimes they are raised and crater-like. The floor of the\
ulcer is smooth and glazed, or occupied by necrosed tissue, and the\
discharge is watery and blood-stained, and as a result of putrefactive\
changes may become offensive. Haemorrhage is rarely a prominent feature,\
but discharge of blood may constitute a symptom of considerable\
diagnostic importance in cancer of internal organs such as the rectum,\
the bladder, or the uterus.\
\
[Illustration: FIG. 57.--Carcinoma of Breast with Cancerous Ulcer.]\
\
_The Contagiousness of Cancer._--A limited number of cases are on record\
in which a cancer appears to have been transferred by contact, as from\
the lower to the upper lip, from one labium majus to the other, from the\
tongue to the cheek, and from one vocal cord to the other; these being\
all examples of cancer involving surfaces which are constantly or\
frequently in contact. The transference of cancer from one human being\
to another, whether by accident, as in the case of a surgeon wounding\
his finger while operating for cancer, or by the deliberate introduction\
of a portion of cancerous tumour into the tissues, has never been known\
to occur. It is by no means infrequent, however, that when recurrence\
takes place after an operation for the removal of cancer, the recurrent\
nodules make their appearance in the main scar or in the scars of\
stitches in its neighbourhood. In the lower animals the grafting of\
cancer only succeeds in animals of the same species; for example, a\
cancer taken from a mouse will not grow in the tissues of a rat, but\
only in a mouse of the same variety as that from which the graft was\
taken.\
\
While cancer cannot be regarded as either contagious or infectious, it\
is important to bear in mind the possibility of infection of a wound\
with cancer when operating for the disease. A cancer should not be cut\
into unless this is essential for purposes of diagnosis, and the wound\
made for exploration should be tightly closed by stitches before the\
curative operation is proceeded with; the instruments used for the\
exploration must not be used again until they have been boiled. The\
greatest care should be taken that a cancer which has softened or broken\
down is not opened into during the operation.\
\
Investigations regarding the cause of cancer have been prosecuted with\
great energy during recent years, but as yet without positive result. It\
is recognised that there are a number of conditions which favour the\
development of cancer, such as prolonged irritation, and a considerable\
number of cases have been recorded in which cancer of the skin of the\
hands has followed prolonged and repeated exposure to the Rontgen rays.\
\
_The Alleged Increase of Cancer._--Regarding the alleged increase of\
cancer, it may be pointed out that it is impossible to ascertain how\
much of the apparent increase is due to more accurate diagnosis and\
improved registration. It is probable also that some increase has taken\
place in consequence of the increased average duration of life; a larger\
proportion of persons now reach the age at which cancer is frequent.\
\
_The prognosis_ largely depends on the variety of cancer and on its\
situation. Certain varieties--such as the atrophic cancer of the breast\
which occurs in old people, and some forms of cancer in the rectum--are\
so indolent in their progress that they can scarcely be said to shorten\
life; while others--such as the softer varieties of mammary cancer\
occurring in young women--are among the most malignant of tumours. The\
mode in which cancer causes death depends to a large extent upon its\
situation. In the gullet, for example, it usually causes death by\
starvation; in the larynx or thyreoid, by suffocation; in the intestine,\
by obstruction of the bowels; in the uterus, prostate, and bladder, by\
haemorrhage or by implication of the ureters and kidneys. Independently\
of their situation, however, cancers frequently cause death by giving\
rise to a progressive impairment of health known as the _cancerous\
cachexia_, a condition which is due to the continued absorption of\
poisonous products from the tumour. The patient loses appetite, becomes\
emaciated, pale, and feverish, and gradually loses strength until he\
dies. In many cases, especially those in which ulceration has occurred,\
the addition of pyogenic infection may also be concerned in the failure\
of health.\
\
_Treatment._--Removal by surgical means affords the best prospect of\
cure. If carcinomatous disease is to be rooted out, its mode of spread\
by means of the lymph vessels must be borne in mind, and as this occurs\
at an early stage, and is not evident on examination, a wide area must\
be included in the operation. The organ from which the original growth\
springs should, if practicable, be altogether removed, because its lymph\
vessels generally communicate freely with each other, and secondary\
deposits have probably already taken place in various parts of it. In\
addition, the nearest chain of lymph glands must also be removed, even\
though they may not be noticeably enlarged, and in some cases--in cancer\
of the breast, for example--the intervening lymph vessels should be\
removed at the same time.\
\
The treatment of cancer by other than operative methods has received a\
great deal of attention within recent years, and many agents have been\
put to the test, _e.g._ colloidal suspensions of selenium, but without\
any positive results. Most benefit has resulted from the use of radium\
and of the X-rays, and one or other should be employed as a routine\
measure after every operation for cancer.\
\
It has been demonstrated that cancer cells are more sensitive to radium\
and to the Rontgen rays than the normal cells of the body, and are more\
easily killed. The effect varies a good deal with the nature and seat of\
the tumour. In rodent cancers of the skin, for example, both radium and\
X-ray treatment are very successful, and are to be preferred to\
operation because they yield a better cosmetic result. While small\
epitheliomas of the skin may be cured by means of the rays, they are not\
so amenable as rodent cancers.\
\
Cancers of mucous membranes are less amenable to ray treatment because\
they are less circumscribed and are difficult of access. In cancers\
under the skin, the Rontgen rays are less efficient; if radium is\
employed, the tube containing it should be inserted into the substance\
of the tumour after the method described in connection with sarcoma--and\
another tube should be placed on the overlying skin.\
\
In the employment of X-rays and of radium in the treatment of cancer,\
experience is required, not only to obtain the maximum effect of the\
rays, but to avoid damage to the adjacent and overlying tissues.\
\
Ray treatment is not to be looked upon as a rival but as a powerful\
supplement to the operative treatment of cancer.\
\
\
VARIETIES OF CANCER\
\
The varieties of cancer are distinguished according to the character and\
arrangement of the epithelial cells.\
\
The _squamous epithelial cancer_ or _epithelioma_ originates from a\
surface covered by squamous epithelium, such as the skin, or the mucous\
membrane of the mouth, gullet, or larynx. The cancer cells retain the\
characters of squamous epithelium, and, being confined within the lymph\
spaces of the sub-epithelial connective tissue, become compressed and\
undergo a horny change. This results in the formation of concentrically\
laminated masses known as cell nests.\
\
The clinical features are those of a slowly growing indurated tumour,\
which nearly always ulcerates; there is a characteristic induration of\
the edges and floor of the ulcer, and its surface is often covered with\
warty or cauliflower-like outgrowths (Fig. 58). The infection of the\
lymph glands is early and constant, and constitutes the most dangerous\
feature of the disease; the secondary growths in the glands exhibit the\
characteristic induration, and may themselves break down and lead to the\
formation of ulcers.\
\
[Illustration: FIG. 58.--Epithelioma of Lip.]\
\
Epithelioma frequently originates in long-standing ulcers or sinuses,\
and in scars, and probably results from the displacement and\
sequestration of epithelial cells during the process of cicatrisation.\
\
The _columnar epithelial cancer_ or _columnar epithelioma_ originates in\
mucous membranes covered with columnar epithelium, and is chiefly met\
with in the stomach and intestine. As it resembles an adenoma in\
structure it is sometimes described as a _malignant adenoma_. Its\
malignancy is shown by the proliferating epithelium invading the other\
coats of the stomach or intestine, and by the development of secondary\
growths.\
\
_Glandular carcinoma_ originates in organs such as the breast, and in\
the glands of mucous membranes and skin. The epithelial cells are not\
arranged on any definite plan, but are closely packed in irregularly\
shaped alveoli. If the alveoli are large and the intervening stroma is\
scanty and delicate, the tumour is soft and brain-like, and is described\
as a _medullary_ or _encephaloid cancer_. If the alveoli are small and\
the intervening stroma is abundant and composed of dense fibrous tissue,\
the tumour is hard, and is known as a _scirrhous cancer_--a form which\
is most frequently met with in the breast. If the cells undergo\
degeneration and absorption and the stroma contracts, the tumour becomes\
still harder, and tends to shrink and to draw in the surrounding parts,\
leading, in the breast, to retraction of the nipple and overlying skin,\
and in the stomach and colon to narrowing of the lumen. When the cells\
of the tumour undergo colloid degeneration, a _colloid cancer_ results;\
if the degeneration is complete, as may occur in the breast, the\
malignancy is thereby greatly diminished; if only partial, as is more\
common in rectal cancer, the malignancy is not appreciably affected.\
Melanin pigment is formed in relation to the cells and stroma of certain\
epithelial tumours, giving rise to _melanotic cancer_, one of the most\
malignant of all new growths. Cyst-like spaces may form in the tumour by\
the accumulation of the secretion of the epithelial cells, or as a\
result of their degeneration--_cystic carcinoma_. This is met with\
chiefly in the breast and ovary, and the tumour resembles the cystic\
adenoma, but it tends to infect its surroundings and gives rise to\
secondary growths.\
\
_Rodent cancer_ originates in the glands of the skin, and presents a\
special tendency to break down and ulcerate on the surface (Figs. 102\
and 103). It almost never infects the lymph glands.\
\
\
DERMOIDS\
\
A dermoid is a tumour containing skin or mucous membrane, occurring in a\
situation where these tissues are not met under normal conditions.\
\
The _skin dermoid_, or _derma-cyst_ as it has been called by Askanazy,\
arises from a portion of epiblast, which has become sequestrated during\
the process of coalescence of two cutaneous surfaces in development.\
This form is therefore most frequently met with on the face and neck in\
the situations which correspond to the various clefts and fissures of\
the embryo. It occurs also on the trunk in situations where the lateral\
halves of the body coalesce during development. Such a dermoid usually\
takes the form of a globular cyst, the wall of which consists of skin,\
and the contents of turbid fluid containing desquamated epithelium, fat\
droplets, cholestrol crystals, and detached hairs. Delicate hairs may\
also be found projecting from the epithelial lining of the cyst.\
\
Faulty coalescence of the cutaneous covering of the back occurs most\
frequently over the lower sacral vertebrae, giving rise to small\
congenital recesses, known as post-anal dimples and coccygeal sinuses.\
These recesses are lined with skin, which is furnished with hairs,\
sebaceous and sweat glands. If the external orifice becomes occluded,\
there results a dermoid cyst.\
\
_Tubulo-dermoids_ arise from embryonic ducts and passages that are\
normally obliterated at birth, for example, _lingual dermoids_ develop\
in relation to the thyreo-glossal duct; _rectal and post-rectal_\
dermoids to the post-anal gut; and _branchial dermoids_ in relation to\
the branchial clefts. Tubulo-dermoids present the same structure as skin\
dermoids, save that mucous membrane takes the place of skin in the wall\
of the cyst, and the contents consist of the pent-up secretion of mucous\
glands.\
\
_Clinical Features._--Although dermoids are of congenital origin, they\
are rarely evident at birth, and may not give rise to visible tumours\
until puberty, when the skin and its appendages become more active, or\
not till adult life. Superficial dermoids, such as those met with at the\
outer angle of the orbit, form rounded, definitely limited tumours over\
which the skin is freely movable. They are usually adherent to the\
deeper parts, and when situated over the skull may be lodged in a\
depression or actual gap in the bone. Sometimes the cyst becomes\
infected and suppurates, and finally ruptures on the surface. This may\
lead to a natural cure, or a persistent sinus may form. Dermoids more\
deeply placed, such as those within the thorax, or those situated\
between the rectum and sacrum, give rise to difficulty in diagnosis,\
even with the help of the X-rays, and their nature is seldom recognised\
until the escape of the contents--particularly hairs--supplies the clue.\
The literature of dermoid cysts is full of accounts of puzzling tumours\
met with in all sorts of situations.\
\
The treatment is to remove the cyst. When it is impossible to remove the\
whole of the lining membrane by dissection, the portion that is left\
should be destroyed with the cautery.\
\
_Ovarian Dermoids._--Dermoids are not uncommon in the ovary (Fig. 59).\
They usually take the form of unilocular or multilocular cysts, the\
wall of which contains skin, mucous membrane, hair follicles, sebaceous,\
sweat, and mucous glands, nails, teeth, nipples, and mammary glands. The\
cavity of the cyst usually contains a pultaceous mixture of shed\
epithelium, fluid fat, and hair. If the cyst ruptures, the epithelial\
elements are diffused over the peritoneum, and may give rise to\
secondary dermoids.\
\
[Illustration: FIG. 59.--Dermoid Cyst of Ovary showing Teeth in its\
interior.]\
\
The ovarian dermoid appears clinically as an abdominal or pelvic tumour\
provided with a pedicle; if the pedicle becomes twisted, the tumour\
undergoes strangulation, an event which is attended with urgent\
symptoms, not unlike those of strangulated hernia.\
\
The treatment consists in removing the tumour by laparotomy.\
\
#Teratoma.#--A teratoma is believed to result from partial dichotomy or\
cleavage of the trunk axis of the embryo, and is found exclusively in\
connection with the skull and vertebral column. It may take the form of\
a monstrosity such as conjoined twins or a parasitic foetus, but more\
commonly it is met with as an irregularly shaped tumour, usually growing\
from the sacrum. On dissection, such a tumour is found to contain a\
curious mixture of tissues--bones, skin, and portions of viscera, such\
as the intestine or liver. The question of the removal of the tumour\
requires to be considered in relation to the conditions present in each\
individual case.\
\
\
CYSTS[3]\
\
[3] Cysts which form in relation to new-growths have been considered\
with tumours.\
\
Cysts are rounded sacs, the wall being composed of fibrous tissue lined\
by epithelium or endothelium; the contents are fluid or semi-solid, and\
vary in character according to the tissue in which the cyst has\
originated.\
\
_Retention and Exudation Cysts._--_Retention cysts_ develop when the\
duct of a secreting gland is partly obstructed; the secretion\
accumulates, and the gland and its duct become distended into a cyst.\
They are met with in the mamma and in the salivary glands. Sebaceous\
cysts or wens are described with diseases of the skin. _Exudation cysts_\
arise from the distension of cavities which are not provided with\
excretory ducts, such as those in the thyreoid.\
\
_Implantation cysts_ are caused by the accidental transference of\
portions of the epidermis into the underlying connective tissue, as may\
occur in wounds by needles, awls, forks, or thorns. The implanted\
epidermis proliferates and forms a small cyst. They are met with chiefly\
on the palmar aspect of the fingers, and vary in size from a split pea\
to a cherry. The treatment consists in removing them by dissection.\
\
_Parasitic cysts_ are produced by the growth within the tissues of\
cyst-forming parasites, the best known being the taenia echinococcus,\
which gives rise to the _hydatid cyst_. The liver is by far the most\
common site of hydatid cysts in the human subject.\
\
With regard to the further life-history of hydatids, the living elements\
of the cyst may die and degenerate, or the cyst may increase in size\
until it ruptures. As a result of pyogenic infection the cyst may be\
converted into an abscess.\
\
The _clinical features_ of hydatids vary so much with their situation\
and size, that they are best discussed with the individual organs. In\
general it may be said that there is a slow formation of a globular,\
elastic, fluctuating, painless swelling. Fluctuation is detected when\
the cyst approaches the surface, and it is then also that percussion\
may elicit the "hydatid thrill" or fremitus. This thrill is not often\
obtainable, and in any case is not pathognomonic of hydatids, as it may\
be elicited in ascites and in other abdominal cysts. Pressure of the\
cyst upon adjacent structures, and the occurrence of suppuration, are\
attended with characteristic clinical features.\
\
The _diagnosis_ of hydatids will be considered with the individual\
organs. The disease is more common in certain parts of Australia and in\
Shetland and Iceland than in countries where the association of dogs in\
the domestic life of the inhabitants is less intimate. Pfeiler, who has\
worked at the _serum diagnosis of hydatid disease_, regards the\
complement deviation method as the most reliable; he believes that a\
positive reaction may almost be regarded as absolutely diagnostic of an\
echinococcal lesion.\
\
The _treatment_ is to excise the cyst completely, or to inject into it a\
1 per cent. solution of formalin. In operating upon hydatids the utmost\
care must be taken to avoid leakage of the contents of the cyst, as\
these may readily disseminate the infection.\
\
A _blood cyst_ or haematoma results from the encapsulation of\
extravasated blood in the tissues, from haemorrhage taking place into a\
preformed cyst, or from the saccular pouching of a varicose vein.\
\
A _lymph cyst_ usually results from a contusion in which the skin is\
forcibly displaced from the subjacent tissues, and lymph vessels are\
thereby torn across. The cyst is usually situated between the skin and\
fascia, and contains clear or blood-stained serum. At first it is lax\
and fluctuates readily, later it becomes larger and more tense. The\
treatment consists in drawing off the contents through a hollow needle\
and applying firm pressure. Apart from injury, lymph cysts are met with\
as the result of the distension of lymph spaces and vessels\
(_lymphangiectasis_); and in lymphangiomas, of which the best-known\
example is the cystic hygroma or hydrocele of the neck.\
\
\
GANGLION\
\
This term is applied to a cyst filled with a clear colourless jelly or\
colloid material, met with in the vicinity of a joint or tendon sheath.\
\
The commonest variety--the _carpal ganglion_--popularly known as a\
sprained sinew--is met with as a smooth, rounded, or oval swelling on\
the dorsal aspect of the carpus, usually towards its radial side (Fig. 60).\
It is situated over one of the intercarpal or other joints in this\
region, and may be connected with one or other of the extensor tendons.\
The skin and fascia are movable over the cyst. The cyst varies in size\
from a pea to a pigeon's egg, and usually attains its maximum size\
within a few months and then remains stationary. It becomes tense and\
prominent when the hand is flexed towards the palm. Its appearance is\
usually ascribed to some strain of the wrist--for example, in girls\
learning gymnastics. It may cause no symptoms or it may interfere with\
the use of the hand, especially in grasping movements and when the hand\
is dorsiflexed. In girls it may give rise to pain which shoots up the\
arm. Ganglia are also met with on the dorsum of the metacarpus and on\
the palmar aspect of the wrist.\
\
[Illustration: FIG. 60.--Carpal Ganglion in a woman aet. 25.]\
\
The _tarsal ganglion_ is situated on the dorsum of the foot over one or\
other of the intertarsal joints. It is usually smaller, flatter, and\
more tense than that met with over the wrist, so that it is sometimes\
mistaken for a bony tumour. It rarely causes symptoms, unless so\
situated as to be pressed upon by the boot.\
\
_Ganglia in the region of the knee_ are usually situated over the\
interval between the femur and tibia, most often on the lateral aspect\
of the joint in front of the tendon of the biceps (Fig. 61). The\
swelling, which may attain the size of half a walnut, is tense and hard\
when the knee is extended, and becomes softer and more prominent when it\
is flexed. They are met with in young adults who follow laborious\
occupations or who indulge in athletics, and they cause stiffness,\
discomfort, and impairment of the use of the limb. A ganglion is\
sometimes met with on the median aspect of the head of the metatarsal\
bone of the great toe and may be the cause of considerable suffering; it\
is indistinguishable from the thickened and enlarged bursa so commonly\
present in this situation in the condition known as bunion.\
\
[Illustration: FIG. 61.--Ganglion on lateral aspect of Knee in a young\
woman.]\
\
Ganglionic cysts are met with in other situations than those mentioned,\
but they are so rare as not to require separate description.\
\
Ganglia are to be diagnosed by their situation and physical characters;\
enlarged bursae, synovial cysts, and new-growths are the swellings most\
likely to be mistaken for them. The diagnosis is sometimes only cleared\
up by withdrawing the clear, jelly-like contents through a hollow\
needle.\
\
_Pathological Anatomy._--The wall of the cyst is composed of fibrous\
tissue closely adherent to or fused with the surrounding tissues, so\
that it cannot be shelled out. There is no endothelial lining, and the\
fibrous tissue of the wall is in immediate contact with the colloid\
material in the interior, which appears to be derived by a process of\
degeneration from the surrounding connective tissue. In the region of\
the knee the ganglion is usually multilocular, and consists of a\
meshwork of fibrous tissue, the meshes of which are occupied by colloid\
material.\
\
It is often stated that a ganglion originates from a hernial protrusion\
of the synovial membrane of a joint or tendon sheath. We have not been\
able to demonstrate any communication between the cavity of the cyst\
and that of an adjacent tendon sheath or joint. It is possible, however,\
that the cyst may originate from a minute portion of synovial membrane\
being protruded and strangulated so that it becomes disconnected from\
that to which it originally belonged; it may then degenerate and give\
rise to colloid material, which accumulates and forms a cyst. Ledderhose\
and others regard ganglia as entirely new formations in the\
peri-articular tissues, resulting from colloid degeneration of the\
fibrous tissue of the capsular ligament, occurring at first in numerous\
small areas which later coalesce. Ganglia are probably, therefore, of\
the nature of degeneration cysts arising in the capsule of joints, in\
tendons, and in their sheaths.\
\
_Treatment._--A ganglion can usually be got rid of by a modification of\
the old-fashioned seton. The skin and cyst wall are transfixed by a\
stout needle carrying a double thread of silkworm gut; some of the\
colourless jelly escapes from the punctures; the ends of the thread are\
tied and cut short, and a dressing is applied. A week later the threads\
are removed and the minute punctures are sealed with collodion. The\
action of the threads is to convert the cyst wall into granulation\
tissue, which undergoes the usual conversion into scar tissue. If the\
cyst re-forms, it should be removed by open dissection under local\
anaesthesia. Puncture with a tenotomy knife and scraping the interior,\
and the injection of irritants, are alternative, but less satisfactory,\
methods of treatment.\
\
_Ganglia_ in the substance of _tendons_ are rare. The diagnosis rests on\
the observation that the small tumour is cystic, and that it follows the\
movements of the tendon. The cyst is at first multiple, but the\
partitions disappear, and the spaces are thrown into one. The tendon is\
so weakened that it readily ruptures. The best treatment is to resect\
the affected segment of tendon.\
\
The so-called "compound palmar ganglion" is a tuberculous disease of the\
tendon sheaths, and is described with diseases of tendon sheaths.\
\
\
\
\
CHAPTER XI\
\
INJURIES\
\
\
CONTUSIONS--WOUNDS: _Varieties_--WOUNDS BY FIREARMS AND\
    EXPLOSIVES: _Pistol-shot wounds_; _Wounds by sporting guns_;\
    _Wounds by rifle bullets_; _Wounds received in warfare_; _Shell\
    wounds_. _Embedded foreign bodies_--BURNS AND\
    SCALDS--INJURIES PRODUCED BY ELECTRICITY: _X-ray and\
    radium_; _Electrical burns_; _Lightning stroke_.\
\
\
CONTUSIONS\
\
A contusion or bruise is a laceration of the subcutaneous soft tissues,\
without solution of continuity of the skin. When the integument gives\
way at the same time, a _contused-wound_ results. Bruising occurs when\
force is applied to a part by means of a blunt object, whether as a\
direct blow, a crush, or a grazing form of violence. If the force acts\
at right angles to the part, it tends to produce localised lesions which\
extend deeply; while, if it acts obliquely, it gives rise to lesions\
which are more diffuse, but comparatively superficial. It is well to\
remember that those who suffer from scurvy, or haemophilia (bleeders),\
and fat and anaemic females, are liable to be bruised by comparatively\
trivial injuries.\
\
_Clinical Features._--The less severe forms of contusion are associated\
with _ecchymosis_, numerous minute and discrete punctate haemorrhages\
being scattered through the superficial layers of the skin, which is\
slightly oedematous. The effused blood is soon reabsorbed.\
\
The more severe forms are attended with _extravasation_, the\
extravasated blood being widely diffused through the cellular tissue of\
the part, especially where this is loose and lax, as in the region of\
the orbit, the scrotum and perineum, and on the chest wall. A blue or\
bluish-black discoloration occurs in patches, varying in size and depth\
with the degree of force which produced the injury, and in shape with\
the instrument employed. It is most intense in regions where the skin is\
naturally thin and pigmented. In parts where the extravasated blood is\
only separated from the oxygen of the air by a thin layer of epidermis\
or by a mucous membrane, it retains its bright arterial colour. These\
points are often well illustrated in cases of black eye, where the blood\
effused under the conjunctiva is bright red, while that in the eyelids\
is almost black. In severe contusions associated with great tension of\
the skin--for example, over the front of the tibia or around the\
ankle--blisters often form on the surface and constitute a possible\
avenue of infection. When deeply situated, the blood tends to spread\
along the lines of least resistance, partly under the influence of\
gravity, passing under fasciae, between muscles, along the sheaths of\
vessels, or in connective-tissue spaces, so that it may only reach the\
surface after some time, and at a considerable distance from the seat of\
injury. This fact is sometimes of importance in diagnosis, as, for\
example, in certain fractures of the base of the skull, where\
discoloration appears under the conjunctiva or behind the mastoid\
process some days after the accident.\
\
Blood extravasated deeply in the tissues gives rise to a firm,\
resistant, doughy swelling, in which there may be elicited on deep\
palpation a peculiar sensation, not unlike the crepitus of fracture.\
\
It frequently happens that, from the tearing of lymph vessels, serous\
fluid is extravasated, and a _lymphatic_ or _serous cyst_ may form.\
\
In all contusions accompanied by extravasation, there is marked swelling\
of the area involved, as well as pain and tenderness. The temperature\
may rise to 101 o F., or, in the large extravasations that occur in\
bleeders, even higher--a form of aseptic fever. The degree of shock is\
variable, but sudden syncope frequently results from severe bruises of\
the testicle, abdomen, or head, and occasionally marked nervous\
depression follows these injuries.\
\
Contusion of muscles or nerves may produce partial atrophy and paresis,\
as is often seen after injuries in the region of the shoulder.\
\
In alcoholic or other debilitated patients, suppuration is liable to\
ensue in bruised parts, infection taking place from cocci circulating in\
the blood, or through the overlying skin.\
\
_Terminations of Contusions._--The usual termination is a complete\
return to the normal, some of the extravasated blood being organised,\
but most of it being reabsorbed. During the process characteristic\
alterations in the colour of the effused blood take place as a result of\
changes in the blood pigment. In from twenty-four to forty-eight hours\
the margins of the blue area become of a violet hue, and as time goes on\
the discoloured area increases in size, and becomes successively green,\
yellow, and lemon-coloured at its margins, the central part being the\
last to change. The rate at which this play of colours proceeds is so\
variable, and depends on so many circumstances, that no time-limits can\
be laid down. During the disintegration of the effused blood the\
adjacent lymph glands may become enlarged, and on dissection may be\
found to be pigmented. Sometimes the blood persists as a collection of\
fluid with a newly formed connective-tissue capsule, constituting a\
_haematoma_ or _blood cyst_, more often met with in the scalp than in\
other parts.\
\
The impairment of the blood supply of the skin may lead to the formation\
of _blisters_, or to _necrosis_. Death of skin is more liable to occur\
in bleeders, and when the slough separates the blood-clot is exposed and\
the reparative changes go on extremely slowly. _Suppuration_ may occur\
and lead to the formation of an abscess as a result of direct infection\
from the skin or through the circulation.\
\
_Treatment._--If the patient is seen immediately after the accident,\
elevation of the part, and firm pressure applied by means of a thick pad\
of cotton wool and an elastic bandage, are useful in preventing effusion\
of blood. Ice-bags and evaporating lotions are to be used with caution,\
as they are liable to lower the vitality of the damaged tissues and lead\
to necrosis of the skin.\
\
When extravasation has already taken place, massage is the most speedy\
and efficacious means of dispersing the effused blood. The part should\
be massaged several times a day, unless the presence of blebs or\
abrasions of the skin prevents this being done. When this is the case,\
the use of antiseptic dressings is called for to prevent infection and\
to promote healing, after which massage is employed.\
\
When the tension caused by the extravasated blood threatens the vitality\
of the skin, incisions may be made, if asepsis can be assured. The blood\
from a haematoma may be withdrawn by an exploring needle, and the\
puncture sealed with collodion. Infective complications must be looked\
for and dealt with on general principles.\
\
\
WOUNDS\
\
A wound is a solution in the continuity of the skin or mucous membrane\
and of the underlying tissues, caused by violence.\
\
Three varieties of wounds are described: incised, punctured, and\
contused and lacerated.\
\
#Incised Wounds.#--Typical examples of incised wounds are those made by\
the surgeon in the course of an operation, wounds accidentally inflicted\
by cutting instruments, and suicidal cut-throat wounds. It should be\
borne in mind in connection with medico-legal inquiries, that wounds of\
soft parts that closely overlie a bone, such as the skull, the tibia, or\
the patella, although, inflicted by a blunt instrument, may have all the\
appearances of incised wounds.\
\
_Clinical Features._--One of the characteristic features of an incised\
wound is its tendency to gape. This is evident in long skin wounds, and\
especially when the cut runs across the part, or when it extends deeply\
enough to divide muscular fibres at right angles to their long axis. The\
gaping of a wound, further, is more marked when the underlying tissues\
are in a state of tension--as, for example, in inflamed parts. Incised\
wounds in the palm of the hand, the sole of the foot, or the scalp,\
however, have little tendency to gape, because of the close attachment\
of the skin to the underlying fascia.\
\
Incised wounds, especially in inflamed tissues, tend to bleed profusely;\
and when a vessel is only partly divided and is therefore unable to\
contract, it continues to bleed longer than when completely cut across.\
\
The _special risks_ of incised wounds are: (1) division of large blood\
vessels, leading to profuse haemorrhage; (2) division of nerve-trunks,\
resulting in motor and sensory disturbances; and (3) division of tendons\
or muscles, interfering with movement.\
\
_Treatment._--If haemorrhage is still going on, it must be arrested by\
pressure, torsion, or ligature, as the accumulation of blood in a wound\
interferes with union. If necessary, the wound should be purified by\
washing with saline solution or eusol, and the surrounding skin painted\
with iodine, after which the edges are approximated by sutures. The raw\
surfaces must be brought into accurate apposition, care being taken that\
no inversion of the cutaneous surface takes place. In extensive and deep\
wounds, to ensure more complete closure and to prevent subsequent\
stretching of the scar, it is advisable to unite the different\
structures--muscles, fasciae, and subcutaneous tissue--by separate series\
of _buried sutures_ of catgut or other absorbable material. For the\
approximation of the skin edges, stitches of horse-hair, fishing-gut, or\
fine silk are the most appropriate. These _stitches of coaptation_ may\
be interrupted or continuous. In small superficial wounds on exposed\
parts, stitch marks may be avoided by approximating the edges with\
strips of gauze fixed in position by collodion, or by subcutaneous\
sutures of fine catgut. Where the skin is loose, as, for example, in the\
neck, on the limbs, or in the scrotum, the use of Michel's clips is\
advantageous in so far as these bring the deep surfaces of the skin into\
accurate apposition, are introduced with comparatively little pain, and\
leave only a slight mark if removed within forty-eight hours.\
\
When there is any difficulty in bringing the edges of the wound into\
apposition, a few interrupted _relaxation stitches_ may be introduced\
wide of the margins, to take the strain off the coaptation stitches.\
Stout silk, fishing-gut, or silver wire may be employed for this\
purpose. When the tension is extreme, Lister's button suture may be\
employed. The tension is relieved and death of skin prevented by scoring\
it freely with a sharp knife. Relaxation stitches should be removed in\
four or five days, and stitches of coaptation in from seven to ten days.\
On the face and neck, wounds heal rapidly, and stitches may be removed\
in two or three days, thus diminishing the marks they leave.\
\
_Drainage._--In wounds in which no cavity has been left, and in which\
there is no reason to suspect infection, drainage is unnecessary. When,\
however, the deeper parts of an extensive wound cannot be brought into\
accurate apposition, and especially when there is any prospect of oozing\
of blood or serum--as in amputation stumps or after excision of the\
breast--drainage is indicated. It is a wise precaution also to insert\
drainage tubes into wounds in fat patients when there is the slightest\
reason to suspect the presence of infection. Glass or rubber tubes are\
the best drains; but where it is desirable to leave little mark, a few\
strands of horse-hair, or a small roll of rubber, form a satisfactory\
substitute. Except when infection occurs, the drain is removed in from\
one to four days and the opening closed with a Michel's clip or a\
suture.\
\
#Punctured Wounds.#--Punctured wounds are produced by narrow, pointed\
instruments, and the sharper and smoother the instrument the more does\
the resulting injury resemble an incised wound; while from more rounded\
and rougher instruments the edges of the wound are more or less contused\
or lacerated. The depth of punctured wounds greatly exceeds their width,\
and the damage to subcutaneous parts is usually greater than that to the\
skin. When the instrument transfixes a part, the edges of the wound of\
entrance may be inverted, and those of the exit wound everted. If the\
instrument is a rough one, these conditions may be reversed by its\
sudden withdrawal.\
\
Punctured wounds neither gape nor bleed much. Even when a large vessel\
is implicated, the bleeding usually takes place into the tissues rather\
than externally.\
\
The _risks_ incident to this class of wounds are: (1) the extreme\
difficulty, especially when a dense fascia has been perforated, of\
rendering them aseptic, on account of the uncertainty as to their depth,\
and of the way in which the surface wound closes on the withdrawal of\
the instrument; (2) different forms of aneurysm may result from the\
puncture of a large vessel; (3) perforation of a joint, or of a serous\
cavity, such as the abdomen, thorax, or skull, materially adds to the\
danger.\
\
_Treatment._--The first indication is to purify the whole extent of the\
wound, and to remove any foreign body or blood-clot that may be in it.\
It is usually necessary to enlarge the wound, freely dividing injured\
fasciae, paring away bruised tissues, and purifying the whole\
wound-surface. Any blood vessel that is punctured should be cut across\
and tied; and divided muscles, tendons, or nerves must be sutured. After\
haemorrhage has been arrested, iodoform and bismuth paste is rubbed into\
the raw surface, and the wound closed. If there is any reason to doubt\
the asepticity of the wound, it is better treated by the open method,\
and a Bier's bandage should be applied.\
\
#Contused and Lacerated Wounds.#--These may be considered together, as\
they so occur in practice. They are produced by crushing, biting, or\
tearing forms of violence--such as result from machinery accidents,\
firearms, or the bites of animals. In addition to the irregular wound of\
the integument, there is always more or less bruising of the parts\
beneath and around, and the subcutaneous lesions are much wider than\
appears on the surface.\
\
Wounds of this variety usually gape considerably, especially when there\
is much laceration of the skin. It is not uncommon to have considerable\
portions of skin, muscle, or tendon completely torn away.\
\
Haemorrhage is seldom a prominent feature, as the crushing or tearing of\
the vessel wall leads to the obliteration of the lumen.\
\
The _special risks_ of these wounds are: (1) Sloughing of the bruised\
tissues, especially when attempts to sterilise the wound have not been\
successful. (2) Reactionary haemorrhage after the initial shock has\
passed off. (3) Secondary haemorrhage as a result of infective processes\
ensuing in the wound. (4) Loss of muscle or tendon, interfering with\
motion. (5) Cicatricial contraction. (6) Gangrene, which may follow\
occlusion of main vessels, or virulent infective processes. (7) It is\
not uncommon to have particles of carbon embedded in the tissues after\
lacerated wounds, leaving unsightly, pigmented scars. This is often seen\
in coal-miners, and in those injured by firearms, and is to be prevented\
by removing all gross dirt from the edges of the wound.\
\
_Treatment._--In severe wounds of this class implicating the\
extremities, the most important question that arises is whether or not\
the limb can be saved. In examining the limb, attention should first be\
directed to the state of the main blood vessels, in order to determine\
if the vascular supply of the part beyond the lesion is sufficient to\
maintain its vitality. Amputation is usually called for if there is\
complete absence of pulsation in the distal arteries and if the part\
beyond is cold. If at the same time important nerve-trunks are\
lacerated, so that the function of the limb would be seriously impaired,\
it is not worth running the risk of attempting to save it. If, in\
addition, there is extensive destruction of large muscular masses or of\
important tendons, or comminution of the bones, amputation is usually\
imperative. Stripping of large areas of skin is not in itself a reason\
for removing a limb, as much can be done by skin grafting, but when it\
is associated with other lesions it favours amputation. In considering\
these points, it must be borne in mind that the damage to the deeper\
tissues is always more extensive than appears on the surface, and that\
in many cases it is only possible to estimate the real extent of the\
injury by administering an anaesthetic and exploring the wound. In\
doubtful cases the possibility of rendering the parts aseptic will often\
decide the question for or against amputation. If thorough purification\
is accomplished, the success which attends conservative measures is\
often remarkable. It is permissible to run an amount of risk to save an\
upper extremity which would be unjustifiable in the case of a lower\
limb. The age and occupation of the patient must also be taken into\
account.\
\
It having been decided to try and save the limb, the question is only\
settled for the moment; it may have to be reconsidered from day to day,\
or even from hour to hour, according to the progress of the case.\
\
When it is decided to make the attempt to save the limb, the wound must\
be thoroughly purified. All bruised tissue in which gross dirt has\
become engrained should be cut away with knife or scissors. The raw\
surface is then cleansed with eusol, washed with sterilised salt\
solution followed by methylated spirit, and rubbed all over with "bipp"\
paste. If the purification is considered satisfactory the wound may be\
closed, otherwise it is left open, freely drained or packed with gauze,\
and the limb is immobilised by suitable splints.\
\
\
WOUNDS BY FIREARMS AND EXPLOSIVES\
\
It is not necessary here to do more than indicate the general characters\
of wounds produced by modern weapons. For further details the reader is\
referred to works on military surgery. Experience has shown that the\
nature and severity of the injuries sustained in warfare vary widely in\
\
different campaigns, and even in different fields of the same campaign.\
Slight variations in the size, shape, and weight of rifle bullets, for\
example, may profoundly modify the lesions they produce: witness the\
destructive effect of the pointed bullet compared with that of the\
conical form previously used. The conditions under which the fighting is\
carried on also influence the wounds. Those sustained in the open,\
long-range fighting of the South African campaign of 1899-1902 were very\
different from those met with in the entrenched warfare in France in\
1914-1918. It has been found also that the infective complications are\
greatly influenced by the terrain in which the fighting takes place. In\
the dry, sandy, uncultivated veldt of South Africa, bullet wounds seldom\
became infected, while those sustained in the highly manured fields of\
Belgium were almost invariably contaminated with putrefactive organisms,\
and gaseous gangrene and tetanus were common complications. It has been\
found also that wounds inflicted in naval engagements present different\
characters from those sustained on land. Many other factors, such as the\
physical and mental condition of the men, the facilities for affording\
first aid, and the transport arrangements, also play a part in\
determining the nature and condition of the wounds that have to be dealt\
with by military surgeons.\
\
Whatever the nature of the weapon concerned, the wound is of the\
_punctured, contused, and lacerated_ variety. Its severity depends on\
the size, shape, and velocity of the missile, the range at which the\
weapon is discharged, and the part of the body struck.\
\
Shock is a prominent feature, but its degree, as well as the time of its\
onset, varies with the extent and seat of the injury, and with the\
mental state of the patient when wounded. We have observed pronounced\
shock in children after being shot even when no serious injury was\
sustained. At the moment of injury the patient experiences a sensation\
which is variously described as being like the lash of a whip, a blow\
with a stick, or an electric shock. There is not much pain at first, but\
later it may become severe, and is usually associated with intense\
thirst, especially when much blood has been lost.\
\
In all forms of wounds sustained in warfare, septic infection\
constitutes the main risk, particularly that resulting from\
streptococci. The presence of anaerobic organisms introduces the\
additional danger of gaseous forms of gangrene.\
\
The earlier the wound is disinfected the greater is the possibility of\
diminishing this risk. If cleansing is carried out within the first six\
hours the chance of eliminating sepsis is good; with every succeeding\
six hours it diminishes, until after twenty-four hours it is seldom\
possible to do more than mitigate sepsis. (J. T. Morrison.)\
\
The presence of a metallic foreign body having been determined and its\
position localised by means of the X-rays, all devitalised and\
contaminated tissue is excised, the foreign material, _e.g._, a missile,\
fragments of clothing, gravel and blood-clot, removed, the wound\
purified with antiseptics and closed or drained according to\
circumstances.\
\
#Pistol-shot Wounds.#--Wounds inflicted by pistols, revolvers, and small\
air-guns are of frequent occurrence in civil practice, the weapon being\
discharged usually by accident, but frequently with suicidal, and\
sometimes with homicidal intent.\
\
With all calibres and at all ranges, except actual contact, the wound of\
entrance is smaller than the bullet. If the weapon is discharged within\
a foot of the body, the skin surrounding the wound is usually stained\
with powder and burned, and the hair singed. At ranges varying from six\
inches to thirty feet, grains of powder may be found embedded in the\
skin or lying loose on the surface, the greater the range the wider\
being the area of spread. When black powder is used, the embedded grains\
usually leave a permanent bluish-black tattooing of the skin. When the\
weapon is placed in contact with the skin, the subcutaneous tissues are\
lacerated over an area of two or three inches around the opening made by\
the bullet and smoke and powder-staining and scorching are more marked\
than at longer ranges.\
\
When the bullet perforates, the exit wound is usually larger and more\
extensively lacerated than the wound of entrance. Its margins are as a\
rule everted, and it shows no marks of flame, smoke, or powder. These\
features are common to all perforations caused by bullets.\
\
Pistol wounds only produce dangerous effects when fired at close range,\
and when the cavities of the skull, the thorax, or the abdomen are\
implicated. In the abdomen a lethal injury may readily be caused even by\
pistols of the "toy" order. These injuries will be described with\
regional surgery.\
\
Pistol-shot wounds of _joints_ and _soft parts_ are seldom of serious\
import apart from the risk of haemorrhage and of infection.\
\
_Treatment._--The treatment of wounds of the soft parts consists in\
purifying the wounds of entrance and exit and the surrounding skin, and\
in providing for drainage if this is indicated.\
\
There being no urgency for the removal of the bullet, time should be\
taken to have it localised by the X-rays, preferably by stereoscopic\
plates. In some cases it is not necessary to remove the bullet.\
\
#Wounds by Sporting Guns.#--In the common sporting or scatter gun, with\
which accidents so commonly occur during the shooting season, the charge\
of small shot or pellets leave the muzzle of the gun as a solid mass\
which makes a single ragged wound having much the appearance of that\
caused by a single bullet. At a distance of from four to five feet from\
the muzzle the pellets begin to disperse so that there are separate\
punctures around the main central wound. As the range increases, these\
outlying punctures make a wider and wider pattern, until at a distance\
of from eighteen to twenty feet from the muzzle, the scattering is\
complete, there is no longer any central wound, and each individual\
pellet makes its own puncture. From these elementary data, it is usually\
possible, from the features of the wound, to arrive at an approximately\
accurate conclusion regarding the range at which the gun was discharged,\
and this may have an important bearing on the question of accident,\
suicide, or murder.\
\
As regards the effects on the tissues at close range, that is, within a\
few feet, there is widespread laceration and disruption; if a bone is\
struck it is shattered, and portions of bone may be displaced or even\
driven out through the exit wound.\
\
When the charge impinges over one of the large cavities of the body, the\
shot may scatter widely through the contained viscera, and there is\
often no exit wound. In the thorax, for example, if a rib is struck, the\
charge and possibly fragments of bone, will penetrate the pleura, and be\
dispersed throughout the lung; in the head, the skull may be shattered\
and the brain torn up; and in the abdomen, the hollow viscera may be\
perforated in many places and the solid organs lacerated.\
\
On covered parts the clothing, by deflecting the shot, influences the\
size and shape of the wound; the entrance wound is increased in size and\
more ragged, and portions of the clothes may be driven into the tissues.\
\
[Illustration: FIG. 62.--Radiogram showing Pellets embedded in Arm.\
\
(Mr. J. W. Dowden's case.)]\
\
A charge of small shot is much more destructive to blood vessels,\
tendons, and ligaments than a single bullet, which in many cases pushes\
such structures aside without dividing them. In the abdomen and chest,\
also, the damage done by a full charge of shot is much more extensive\
than that inflicted by a single bullet, the deflection of the pellets\
leading to a greater number of perforations of the intestine and more\
widespread laceration of solid viscera.\
\
When the charge impinges on one of the extremities at close range, we\
often have the opportunity of observing that the exit wound is larger,\
more ragged than that of entrance, and that its edges are everted; the\
extensive tearing and bruising of all the tissues, including the bones,\
and the marked tendency to early and progressive septic infection,\
render amputation compulsory in the majority of such cases.\
\
At a range of from twenty to thirty feet, although the scatter is\
complete, the pellets are still close together, so that if they\
encounter the shaft of a long bone, even the femur, they fracture the\
bone across, often along with some longitudinal splintering.\
\
Individual pellets striking the shafts of long bones become flattened or\
distorted, and when cancellated bone is struck they become embedded in\
it (Fig. 62).\
\
The skin, when it is closely peppered with shot, is liable to lose its\
vitality, and with the addition of a little sepsis, readily necroses and\
comes away as a slough.\
\
When the shot have diverged so as to strike singly, they seldom do much\
harm, but fatal damage may be done to the brain or to the aorta, or the\
eye may be seriously injured by a single pellet.\
\
Small shot fired at longer ranges--over about a hundred and fifty\
feet--usually go through the skin, but seldom pierce the fascia, and lie\
embedded in the subcutaneous tissue, from which they can readily be\
extracted.\
\
The wad of the cartridge behaves erratically: so long as it remains flat\
it goes off with the rest of the charge, and is often buried in the\
wound; but if it curls up or turns on its side, it is usually deflected\
and flies clear of the shot. It may make a separate wound.\
\
Wounds from sporting guns are to be _treated_ on the usual lines, the\
early efforts being directed to the alleviation of shock and the\
prevention of septic infection. There is rarely any urgency in the\
removal of pellets from the tissues.\
\
#Wounds by Rifle Bullets.#--The vast majority of wounds inflicted by\
rifle bullets are met with in the field during active warfare, and fall\
to be treated by military surgeons. They occasionally occur\
accidentally, however, during range practice for example, and may then\
come under the notice of the civil surgeon.\
\
It is only necessary here to consider the effects of modern small-bore\
rifle or machine-gun bullets.\
\
The trajectory is practically flat up to 675 yards. In destructive\
effect there is not much difference between the various high velocity\
bullets used in different armies; they will kill up to a distance of two\
miles. The hard covering is employed to enable the bullet to take the\
grooves in the rifle, and to prevent it stripping as it passes through\
the barrel. It also increases the penetrating power of the missile, but\
diminishes its "stopping" power, unless a vital part or a long bone is\
struck. By removing the covering from the point of the bullet, as is\
done in the Dum-Dum bullet, or by splitting the end, the bullet is made\
to expand or "mushroom" when it strikes the body, and its stopping power\
is thereby greatly increased, the resulting wound being much more\
severe. These "soft-nosed" expanding bullets are to be distinguished\
from "explosive" bullets which contain substances which detonate on\
impact. High velocity bullets are unlikely to lodge in the body unless\
spent, or pulled up by a sandbag, or metal buckle on a belt, or a book\
in the pocket, or the core and the case separating--"stripping" of the\
bullet. Spent shot may merely cause bruising of the surface, or they may\
pass through the skin and lodge in the subcutaneous tissue, or may even\
damage some deeper structure such as a nerve trunk.\
\
A blank cartridge fired at close range may cause a severe wound, and, if\
charged with black powder, may leave a permanent bluish-black\
pigmentation of the skin.\
\
The lesions of individual tissues--bones, nerves, blood vessels--are\
considered with these.\
\
#Treatment of Gunshot Wounds under War Conditions.#--It is only\
necessary to indicate briefly the method of dealing with gunshot wounds\
in warfare as practised in the European War.\
\
1. _On the Field._--Haemorrhage is arrested in the limbs by an improvised\
tourniquet; in the head by a pad and bandage; in the thorax or abdomen\
by packing if necessary, but this should be avoided if possible, as it\
favours septic infection. If a limb is all but detached it should be\
completely severed. A full dose of morphin is given hypodermically. The\
ampoule of iodine carried by the wounded man is broken, and its contents\
are poured over and around the wound, after which the field dressing is\
applied. In extensive wounds, the "shell-dressing" carried by the\
stretcher bearers is preferred. All bandages are applied loosely to\
allow for subsequent swelling. The fragments of fractured bones are\
immobilised by some form of emergency splint.\
\
2. _At the Advanced Dressing Station_, after the patient has had a\
liberal allowance of warm fluid nourishment, such as soup or tea, a full\
dose of anti-tetanic serum is injected. The tourniquet is removed and\
the wound inspected. Urgent amputations are performed. Moribund patients\
are detained lest they die _en route_.\
\
3. _In the Field Ambulance or Casualty Clearing Station_ further\
measures are employed for the relief of shock, and urgent operations are\
performed, such as amputation for gangrene, tracheotomy for dyspnoea, or\
laparotomy for perforated or lacerated intestine. In the majority of\
cases the main object is to guard against infection; the skin is\
disinfected over a wide area and surrounded with towels; damaged tissue,\
especially muscle, is removed with the knife or scissors, and foreign\
bodies are extracted. Torn blood vessels, and, if possible, nerves and\
tendons are repaired. The wound is then partly closed, provision being\
made for free drainage, or some special method of irrigation, such as\
that of Carrel, is adopted. Sometimes the wound is treated with bismuth,\
iodoform, and paraffin paste (B.I.P.P.) and sutured.\
\
4. _In the Base Hospital or Hospital Ship_ various measures may be\
called for according to the progress of the wound and the condition of\
the patient.\
\
#Shell Wounds and Wounds produced by Explosions.#--It is convenient to\
consider together the effects of the bursting of shells fired from heavy\
ordnance and those resulting in the course of blasting operations from\
the discharge of dynamite or other explosives, or from the bursting of\
steam boilers or pipes, the breaking of machinery, and similar accidents\
met with in civil practice.\
\
Wounds inflicted by shell fragments and shrapnel bullets tend to be\
extensive in area, and show great contusion, laceration, and destruction\
of the tissues. The missiles frequently lodge and carry portions of the\
clothing and, it may be, articles from the man's pocket, with them.\
Shell wounds are attended with a considerable degree of shock. On\
account of the wide area of contusion which surrounds the actual wound\
produced by shell fragments, amputation, when called for, should be\
performed some distance above the torn tissues, as there is considerable\
risk of sloughing of the flaps.\
\
Wounds produced by dynamite explosions and the bursting of boilers have\
the same general characters as shell wounds. Fragments of stone, coal,\
or metal may lodge in the tissues, and favour the occurrence of\
infective complications.\
\
All such injuries are to be treated on the general principles governing\
contused and lacerated wounds.\
\
\
EMBEDDED FOREIGN BODIES\
\
In the course of many operations foreign substances are introduced into\
the tissues and intentionally left there, for example, suture and\
ligature materials, steel or aluminium plates, silver wire or ivory pegs\
used to secure the fixation of bones, or solid paraffin employed to\
correct deformities. Other substances, such as gauze, drainage tubes,\
or metal instruments, may be unintentionally left in a wound.\
\
Foreign bodies may also lodge in accidentally inflicted wounds, for\
example, bullets, needles, splinters of wood, or fragments of clothing.\
The needles of hypodermic syringes sometimes break and a portion remains\
embedded in the tissues. As a result of explosions, particles of carbon,\
in the form of coal-dust or gunpowder, or portions of shale, may lodge\
in a wound.\
\
The embedded foreign body at first acts as an irritant, and induces a\
reaction in the tissues in which it lodges, in the form of hyperaemia,\
local leucocytosis, proliferation of fibroblasts, and the formation of\
granulation tissue. The subsequent changes depend upon whether or not\
the wound is infected with pyogenic bacteria. If it is so infected,\
suppuration ensues, a sinus forms, and persists until the foreign body\
is either cast out or removed.\
\
If the wound is aseptic, the fate of the foreign body varies with its\
character. A substance that is absorbable, such as catgut or fine silk,\
is surrounded and permeated by the phagocytes, which soften and\
disintegrate it, the debris being gradually absorbed in much the same\
manner as a fibrinous exudate. Minute bodies that are not capable of\
being absorbed, such as particles of carbon, or of pigment used in\
tattooing, are taken up by the phagocytes, and in course of time\
removed. Larger bodies, such as needles or bullets, which are not\
capable of being destroyed by the phagocytes, become encapsulated. In\
the granulation tissue by which they are surrounded large multinuclear\
giant-cells appear ("_foreign-body giant-cells_") and attach themselves\
to the foreign body, the fibroblasts proliferate and a capsule of scar\
tissue is eventually formed around the body. The tissues of the capsule\
may show evidence of iron pigmentation. Sometimes fluid accumulates\
around a foreign body within its capsule, constituting a cyst.\
\
Substances like paraffin, strands of silk used to bridge a gap in a\
tendon, or portions of calcined bone, instead of being encapsulated, are\
gradually permeated and eventually replaced by new connective tissue.\
\
Embedded bodies may remain in the tissues for an indefinite period\
without giving rise to inconvenience. At any time, however, they may\
cause trouble, either as a result of infective complications, or by\
inducing the formation of a mass of inflammatory tissue around them,\
which may simulate a gumma, a tuberculous focus, or a sarcoma. This\
latter condition may give rise to difficulties in diagnosis,\
particularly if there is no history forthcoming of the entrance of the\
foreign body. The ignorance of patients regarding the possible lodgment\
in the tissues of a foreign body--even of considerable size--is\
remarkable. In such cases the X-rays will reveal the presence of the\
foreign body if it is sufficiently opaque to cast a shadow. The heavy,\
lead-containing varieties of glass throw very definite shadows little\
inferior in sharpness and definition to those of metal; almost all the\
ordinary forms of commercial glass also may be shown up by the X-rays.\
\
Foreign bodies encapsulated in the peritoneal cavity are specially\
dangerous, as the proximity of the intestine furnishes a constant\
possibility of infection.\
\
The question of removal of the foreign body must be decided according to\
the conditions present in individual cases; in searching for a foreign\
body in the tissues, unless it has been accurately located, a general\
anaesthetic is to be preferred.\
\
\
BURNS AND SCALDS\
\
The distinction between a burn which results from the action of dry heat\
on the tissues of the body and a scald which results from the action of\
moist heat, has no clinical significance.\
\
In young and debilitated subjects hot poultices may produce injuries of\
the nature of burns. In old people with enfeebled circulation mere\
exposure to a strong fire may cause severe degrees of burning, the\
clothes covering the part being uninjured. This may also occur about the\
feet, legs, or knees of persons while intoxicated who have fallen asleep\
before the fire.\
\
The damage done to the tissues by strong caustics, such as fuming nitric\
acid, sulphuric acid, caustic potash, nitrate of silver, or arsenical\
paste, presents pathological and clinical features almost identical with\
those resulting from heat. Electricity and the Rontgen rays also produce\
lesions of the nature of burns.\
\
_Pathology of Burns._--Much discussion has taken place regarding the\
explanation of the rapidly fatal issue in extensive superficial burns.\
On post-mortem examination the lesions found in these cases are: (1)\
general hyperaemia of all the organs of the abdominal, thoracic, and\
cerebro-spinal cavities; (2) marked leucocytosis, with destruction of\
red corpuscles, setting free haemoglobin which lodges in the epithelial\
cells of the tubules of the kidneys; (3) minute thrombi and\
extravasations throughout the tissues of the body; (4) degeneration of\
the ganglion cells of the solar plexus; (5) oedema and degeneration of\
the lymphoid tissue throughout the body; (6) cloudy swelling of the\
liver and kidneys, and softening and enlargement of the spleen. Bardeen\
suggests that these morbid phenomena correspond so closely to those met\
with where the presence of a toxin is known to produce them, that in all\
probability death is similarly due to the action of some poison produced\
by the action of heat on the skin and on the proteins of the blood.\
\
#Clinical Features--Local Phenomena.#--The most generally accepted\
classification of burns is that of Dupuytren, which is based upon the\
depth of the lesion. Six degrees are thus, recognised: (1) hyperaemia or\
erythema; (2) vesication; (3) partial destruction of the true skin; (4)\
total destruction of the true skin; (5) charring of muscles; (6)\
charring of bones.\
\
It must be observed, however, that burns met with at the bedside always\
illustrate more than one of these degrees, the deeper forms always being\
associated with those less deep, and the clinical picture is made up of\
the combined characters of all. A burn is classified in terms of its\
most severe portion. It is also to be remarked that the extent and\
severity of a burn usually prove to be greater than at first sight\
appears.\
\
_Burns of the first degree_ are associated with erythema of the skin,\
due to hyperaemia of its blood vessels, and result from scorching by\
flame, from contact with solids or fluids below 212 o F., or from\
exposure to the sun's rays. They are characterised clinically by acute\
pain, redness, transitory swelling from oedema, and subsequent\
desquamation of the surface layers of the epidermis. A special form of\
pigmentation of the skin is seen on the front of the legs of women from\
exposure to the heat of the fire.\
\
_Burns of Second Degree--Vesication of the Skin._--These are\
characterised by the occurrence of vesicles or blisters which are\
scattered over the hyperaemic area, and contain a clear yellowish or\
brownish fluid. On removing the raised epidermis, the congested and\
highly sensitive papillae of the skin are exposed. Unna has found that\
pyogenic bacteria are invariably present in these blisters. Burns of the\
second degree leave no scar but frequently a persistent discoloration.\
In rare instances the burned area becomes the seat of a peculiar\
overgrowth of fibrous tissue of the nature of keloid (p 401).\
\
_Burns of Third Degree--Partial Destruction of the Skin._--The epidermis\
and papillae are destroyed in patches, leaving hard, dry, and insensitive\
sloughs of a yellow or black colour. The pain in these burns is\
intense, but passes off during the first or second day, to return again,\
however, when, about the end of a week, the sloughs separate and expose\
the nerve filaments of the underlying skin. Granulations spring up to\
fill the gap, and are rapidly covered by epithelium, derived partly from\
the margins and partly from the remains of skin glands which have not\
been completely destroyed. These latter appear on the surface of the\
granulations as small bluish islets which gradually increase in size,\
become of a greyish-white colour, and ultimately blend with one another\
and with the edges. The resulting cicatrix may be slightly depressed,\
but otherwise exhibits little tendency to contract and cause deformity.\
\
_Burns of Fourth Degree--Total Destruction of the Skin._--These follow\
the more prolonged action of any form of intense heat. Large, black, dry\
eschars are formed, surrounded by a zone of intense congestion. Pain is\
less severe, and is referred to the parts that have been burned to a\
less degree. Infection is liable to occur and to lead to wide\
destruction of the surrounding skin. The amount of granulation tissue\
necessary to fill the gap is therefore great; and as the epithelial\
covering can only be derived from the margins--the skin glands being\
completely destroyed--the healing process is slow. The resulting scars\
are irregular, deep and puckered, and show a great tendency to contract.\
Keloid frequently develops in such cicatrices. When situated in the\
region of the face, neck, or flexures of joints, much deformity and\
impairment of function may result (Fig. 63).\
\
[Illustration: FIG. 63.--Cicatricial Contraction following Severe Burn.]\
\
In _burns of the fifth degree_ the lesion extends through the\
subcutaneous tissue and involves the muscles; while in those of the\
_sixth degree_ it passes still more deeply and implicates the bones.\
These burns are comparatively limited in area, as they are usually\
produced by prolonged contact with hot metal or caustics. Burns of the\
fifth and sixth degrees are met with in epileptics or intoxicated\
persons who fall into the fire. Large blood vessels, nerve-trunks,\
joints, or serous cavities may be implicated.\
\
#General Phenomena.#--It is customary to divide the clinical history of\
a severe burn into three periods; but it is to be observed that the\
features characteristic of the periods have been greatly modified since\
burns have been treated on the same lines as other wounds.\
\
_The first period_ lasts for from thirty-six to forty-eight hours,\
during which time the patient remains in a more or less profound state\
of _shock_, and there is a remarkable absence of pain. When shock is\
absent or little marked, however, the amount of suffering may be great.\
When the injury proves fatal during this period, death is due to shock,\
probably aggravated by the absorption of poisonous substances produced\
in the burned tissues. In fatal cases there is often evidence of\
cerebral congestion and oedema.\
\
The _second period_ begins when the shock passes off, and lasts till the\
sloughs separate. The outstanding feature of this period is _toxaemia_,\
manifested by fever, the temperature rising to 102 o, 103 o, or 104 o F.,\
and congestive or inflammatory conditions of internal organs, giving\
rise to such clinical complications as bronchitis, broncho-pneumonia, or\
pleurisy--especially in burns of the thorax; or meningitis and\
cerebritis, when the neck or head is the seat of the burn. Intestinal\
catarrh associated with diarrhoea is not uncommon; and ulceration of the\
duodenum leading to perforation has been met with in a few cases. These\
phenomena are much more prominent when bacterial infection has taken\
place, and it seems probable that they are to be attributed chiefly to\
the infection, as they have become less frequent and less severe since\
burns have been treated like other breaches of the surface. Albuminuria\
is a fairly constant symptom in severe burns, and is associated with\
congestion of the kidneys. In burns implicating the face, neck, mouth,\
or pharynx, oedema of the glottis is a dangerous complication, entailing\
as it does the risk of suffocation.\
\
The _third period_ begins when the sloughs separate, usually between\
the seventh and fourteenth days, and lasts till the wound heals, its\
duration depending upon the size, depth, and asepticity of the raw area.\
The chief causes of death during this period are toxin absorption in any\
of its forms; waxy disease of the liver, kidneys, or intestine; less\
commonly erysipelas, tetanus, or other diseases due to infection by\
specific organisms. We have seen nothing to substantiate the belief that\
duodenal ulcers are liable to perforate during the third period.\
\
The _prognosis_ in burns depends on (1) the superficial extent, and, to\
a much less degree, the depth of the injury. When more than one-third of\
the entire surface of the body is involved, even in a mild degree, the\
prognosis is grave. (2) The situation of the burn is important. Burns\
over the serous cavities--abdomen, thorax, or skull--are, other things\
being equal, much more dangerous than burns of the limbs. The risk of\
oedema of the glottis in burns about the neck and mouth has already been\
referred to. (3) Children are more liable to succumb to shock during the\
early period, but withstand prolonged suppuration better than adults.\
(4) When the patient survives the shock, the presence or absence of\
infection is the all-important factor in prognosis.\
\
#Treatment.#--The _general treatment_ consists in combating the shock.\
When pain is severe, morphin must be injected.\
\
_Local Treatment._--The local treatment must be carried out on\
antiseptic lines, a general anaesthetic being administered, if necessary,\
to enable the purification to be carried out thoroughly. After carefully\
removing the clothing, the whole of the burned area is gently, but\
thoroughly, cleansed with peroxide of hydrogen or warm boracic lotion,\
followed by sterilised saline solution. As pyogenic bacteria are\
invariably found in the blisters of burns, these must be opened and the\
raised epithelium removed.\
\
The dressings subsequently applied should meet the following\
indications: the relief of pain; the prevention of sepsis; and the\
promotion of cicatrisation.\
\
An application which satisfactorily fulfils these requirements is\
_picric acid_. Pads of lint or gauze are lightly wrung out of a solution\
made up of picric acid, 1 1/2 drams; absolute alcohol, 3 ounces;\
distilled water, 40 ounces, and applied over the whole of the reddened\
area. These are covered with antiseptic wool, _without_ any waterproof\
covering, and retained in position by a many-tailed bandage. The\
dressing should be changed once or twice a week, under the guidance of\
the temperature chart, any portion of the original dressing which\
remains perfectly dry being left undisturbed. The value of a general\
anaesthetic in dressing extensive burns, especially in children, can\
scarcely be overestimated.\
\
Picric acid yields its best results in superficial burns, and it is\
useful as _a primary dressing_ in all. As soon as the sloughs separate\
and a granulating surface forms, the ordinary treatment for a healing\
sore is instituted. Any slough under which pus has collected should be\
cut away with scissors to permit of free drainage.\
\
An occlusive dressing of melted _paraffin_ has also been employed. A\
useful preparation consists of: Paraffin molle 25 per cent., paraffin\
durum 67 per cent., olive oil 5 per cent., oil of eucalyptus 2 per\
cent., and beta-naphthol 1/4 per cent. It has a melting point of 48 o C.\
It is also known as _Ambrine_ and _Burnol_. After the burned area has\
been cleansed and thoroughly dried, it is sponged or painted with the\
melted paraffin, and before solidification takes place a layer of\
sterilised gauze is applied and covered with a second coating of\
paraffin. Further coats of paraffin are applied every other day to\
prevent the gauze sticking to the skin.\
\
An alternative method of treating extensive burns is by immersing the\
part, or even the whole body when the trunk is affected, in a bath of\
boracic lotion kept at the body temperature, the lotion being frequently\
renewed.\
\
If a burn is already infected when first seen, it is to be treated on\
the same principles as govern the treatment of other infected wounds.\
\
All moist or greasy applications, such as Carron oil, carbolic oil and\
ointments, and all substances like collodion and dry powders, which\
retain discharges, entirely fail to meet the indications for the\
rational treatment of burns, and should be abandoned.\
\
Skin-grafting is of great value in hastening healing after extensive\
burns, and in preventing cicatricial contraction. The _deformities_\
which are so liable to develop from contraction of the cicatrices are\
treated on general principles. In the region of the face, neck, and\
flexures of joints (Fig. 63), where they are most marked, the contracted\
bands may be divided and the parts stretched, the raw surface left being\
covered by Thiersch grafts or by flaps of skin raised from adjacent\
surfaces or from other parts of the body (Fig. 1).\
\
\
INJURIES PRODUCED BY ELECTRICITY\
\
#Injuries produced by Exposure to X-Rays and Radium.#--In the routine\
treatment of disease by radiations, injury is sometimes done to the\
tissues, even when the greatest care is exercised as to dosage and\
frequency of application. Robert Knox describes the following\
ill-effects.\
\
_Acute dermatitis_ varying in degree from a slight erythema to deep\
ulceration or even necrosis of skin. When ulcers form they are extremely\
painful and slow to heal. When hair-bearing areas are affected,\
epilation may occur without destroying the hair follicles and the hairs\
are reproduced, but if the reaction is excessive permanent alopecia may\
result.\
\
_Chronic dermatitis_, which results from persistence of the acute form,\
is most intractable and may assume malignant characters. X-ray warts are\
a late manifestation of chronic dermatitis and may become malignant.\
\
Among the _late manifestations_ are neuritis, telangiectasis, and a\
painful and intractable form of ulceration, any of which may come on\
months or even years after the cessation of exposure. _Sterility_ may be\
induced in X-ray workers who are imperfectly protected from the effects\
of the rays.\
\
#Electrical burns# usually occur in those who are engaged in industrial\
undertakings where powerful electrical currents are employed.\
\
The lesions--which vary from a slight superficial scorching to complete\
charring of parts--are most evident at the points of entrance and exit\
of the current, the intervening tissues apparently escaping injury.\
\
The more superficial degrees of electrical burns differ from those\
produced by heat in being almost painless, and in healing very slowly,\
although as a rule they remain dry and aseptic.\
\
The more severe forms are attended with a considerable degree of shock,\
which is not only more profound, but also lasts much longer than the\
shock in an ordinary burn of corresponding severity. The parts at the\
point of entrance of the current are charred to a greater or lesser\
depth. The eschar is at first dry and crisp, and is surrounded by a zone\
of pallor. For the first thirty-six to forty-eight hours there is\
comparatively little suffering, but at the end of that time the parts\
become exceedingly painful. In a majority of cases, in spite of careful\
purification, a slow form of moist gangrene sets in, and the slough\
spreads both in area and in depth, until the muscles and often the\
large blood vessels and nerves are exposed. A line of demarcation\
eventually forms, but the sloughs are exceedingly slow to separate,\
taking from three to five times as long as in an ordinary burn, and\
during the process of separation there is considerable risk of secondary\
haemorrhage from erosion of large vessels.\
\
_Treatment._--Electrical burns are treated on the same lines as ordinary\
burns, by thorough purification and the application of dry dressings,\
with a view to avoiding the onset of moist gangrene. After granulations\
have formed, skin-grafting is of value in hastening healing.\
\
#Lightning-stroke.#--In a large proportion of cases lightning-stroke\
proves instantly fatal. In non-fatal cases the patient suffers from a\
profound degree of shock, and there may or may not be any external\
evidence of injury. In the mildest cases red spots or wheals--closely\
resembling those of urticaria--may appear on the body, but they usually\
fade again in the course of twenty-four hours. Sometimes large patches\
of skin are scorched or stained, the discoloured area showing an\
arborescent appearance. In other cases the injured skin becomes dry and\
glazed, resembling parchment. Appearances are occasionally met with\
corresponding to those of a superficial burn produced by heat. The chief\
difference from ordinary burns is the extreme slowness with which\
healing takes place. Localised paralysis of groups of muscles, or even\
of a whole limb, may follow any degree of lightning-stroke. Treatment is\
mainly directed towards combating the shock, the surface-lesions being\
treated on the same lines as ordinary burns.\
\
\
\
\
CHAPTER XII\
\
METHODS OF WOUND TREATMENT\
\
\
Varieties of wounds--Modes of infection--Lister's work--Means taken to\
    prevent infection of wounds: _heat_; _chemical antiseptics_;\
    _disinfection of hands_; _preparation of skin of patient_;\
    _instruments_; _ligatures_; _dressings_--Means taken to combat\
    infection: _purification_; _open-wound method_.\
\
The surgeon is called upon to treat two distinct classes of wounds: (1)\
those resulting from injury or disease in which _the skin is already\
broken_, or in which a communication with a mucous surface exists; and\
(2) those that he himself makes _through intact skin_, no infected\
mucous surface being involved.\
\
Infection by bacteria must be assumed to have taken place in all wounds\
made in any other way than by the knife of the surgeon operating through\
unbroken skin. On this assumption the modern system of wound treatment\
is based. Pathogenic bacteria are so widely distributed, that in the\
ordinary circumstances of everyday life, no matter how trivial a wound\
may be, or how short a time it may remain exposed, the access of\
organisms to it is almost certain unless preventive measures are\
employed.\
\
It cannot be emphasised too strongly that rigid precautions are to be\
taken to exclude fresh infection, not only in dealing with wounds that\
are free of organisms, but equally in the management of wounds and other\
lesions that are already infected. Any laxity in our methods which\
admits of fresh organisms reaching an infected wound adds materially to\
the severity of the infective process and consequently to the patient's\
risk.\
\
There are many ways in which accidental infection may occur. Take, for\
example, the case of a person who receives a cut on the face by being\
knocked down in a carriage accident on the street. Organisms may be\
introduced to such a wound from the shaft or wheel by which he was\
struck, from the ground on which he lay, from any portion of his\
clothing that may have come in contact with the wound, or from his own\
skin. Or, again, the hands of those who render first aid, the water used\
to bathe the wound, the handkerchief or other extemporised dressing\
applied to it, may be the means of conveying bacterial infection. Should\
the wound open on a mucous surface, such as the mouth or nasal cavity,\
the organisms constantly present in such situations are liable to prove\
agents of infection.\
\
Even after the patient has come under professional care the risks of his\
wound becoming infected are not past, because the hands of the doctor,\
his instruments, dressings, or other appliances may all, unless\
purified, become the sources of infection.\
\
In the case of an operation carried out through unbroken skin, organisms\
may be introduced into the wound from the patient's own skin, from the\
hands of the surgeon or his assistants, through the medium of\
contaminated instruments, swabs, ligature or suture materials, or other\
things used in the course of the operation, or from the dressings\
applied to the wound.\
\
Further, bacteria may gain access to devitalised tissues by way of the\
blood-stream, being carried hither from some infected area elsewhere in\
the body.\
\
_The Antiseptic System of Surgery._--Those who only know the surgical\
conditions of to-day can scarcely realise the state of matters which\
existed before the introduction of the antiseptic system by Joseph\
Lister in 1867. In those days few wounds escaped the ravages of pyogenic\
and other bacteria, with the result that suppuration ensued after most\
operations, and such diseases as erysipelas, pyaemia, and "hospital\
gangrene" were of everyday occurrence. The mortality after compound\
fractures, amputations, and many other operations was appalling, and\
death from blood-poisoning frequently followed even the most trivial\
operations. An operation was looked upon as a last resource, and the\
inherent risk from blood-poisoning seemed to have set an impassable\
barrier to the further progress of surgery. To the genius of Lister we\
owe it that this barrier was removed. Having satisfied himself that the\
septic process was due to bacterial infection, he devised a means of\
preventing the access of organisms to wounds or of counteracting their\
effects. Carbolic acid was the first antiseptic agent he employed, and\
by its use in compound fractures he soon obtained results such as had\
never before been attained. The principle was applied to other\
conditions with like success, and so profoundly has it affected the\
whole aspect of surgical pathology, that many of the infective diseases\
with which surgeons formerly had to deal are now all but unknown. The\
broad principles upon which Lister founded his system remain unchanged,\
although the methods employed to put them into practice have been\
modified.\
\
#Means taken to Prevent Infection of Wounds.#--The avenues by which\
infective agents may gain access to surgical wounds are so numerous and\
so wide, that it requires the greatest care and the most watchful\
attention on the part of the surgeon to guard them all. It is only by\
constant practice and patient attention to technical details in the\
operating room and at the bedside, that the carrying out of surgical\
manipulations in such a way as to avoid bacterial infection will become\
an instinctive act and a second nature. It is only possible here to\
indicate the chief directions in which danger lies, and to describe the\
means most generally adopted to avoid it.\
\
To prevent infection, it is essential that everything which comes into\
contact with a wound should be sterilised or disinfected, and to ensure\
the best results it is necessary that the efficiency of our methods of\
sterilisation should be periodically tested. The two chief agencies at\
our disposal are heat and chemical antiseptics.\
\
#Sterilisation by Heat.#--The most reliable, and at the same time the\
most convenient and generally applicable, means of sterilisation is by\
heat. All bacteria and spores are completely destroyed by being\
subjected for fifteen minutes to _saturated circulating steam_ at a\
temperature of 130 o to 145 o C. (= 266 o to 293 o F.). The articles to be\
sterilised are enclosed in a perforated tin casket, which is placed in a\
specially constructed steriliser, such as that of Schimmelbusch. This\
apparatus is so arranged that the steam circulates under a pressure of\
from two to three atmospheres, and permeates everything contained in it.\
Objects so sterilised are dry when removed from the steriliser. This\
method is specially suitable for appliances which are not damaged by\
steam, such, for example, as gauze swabs, towels, aprons, gloves, and\
metal instruments; it is essential that the efficiency of the steriliser\
be tested from time to time by a self-registering thermometer or other\
means.\
\
The best substitute for circulating steam is _boiling_. The articles are\
placed in a "fish-kettle steriliser" and boiled for fifteen minutes in a\
1 per cent. solution of washing soda.\
\
To prevent contamination of objects that have been sterilised they must\
on no account be touched by any one whose hands have not been\
disinfected and protected by sterilised gloves.\
\
#Sterilisation by Chemical Agents.#--For the purification of the skin of\
the patient, the hands of the surgeon, and knives and other instruments\
that are damaged by heat, recourse must be had to chemical agents.\
These, however, are less reliable than heat, and are open to certain\
other objections.\
\
#Disinfection of the Hands.#--It is now generally recognised that one of\
the most likely sources of wound infection is the hands of the surgeon\
and his assistants. It is only by carefully studying to avoid all\
contact with infective matter that the hands can be kept surgically\
pure, and that this source of wound infection can be reduced to a\
minimum. The risk of infection from this source has further been greatly\
reduced by the systematic use of rubber gloves by house-surgeons,\
dressers, and nurses. The habitual use of gloves has also been adopted\
by the great majority of surgeons; the minority, who find they are\
handicapped by wearing gloves as a routine measure, are obliged to do so\
when operating in infective cases or dressing infected wounds, and in\
making rectal and vaginal examinations.\
\
The gloves may be sterilised by steam, and are then put on dry, or by\
boiling, in which case they are put on wet. The gauntlet of the glove\
should overlap and confine the end of the sleeve of the sterilised\
overall, and the gloved hands are rinsed in lotion before and at\
frequent intervals during the operation. The hands are sterilised before\
putting on the gloves, preferably by a method which dehydrates the skin.\
Cotton gloves may be worn by the surgeon when tying ligatures, or\
between operations, and by the anaesthetist during operations on the\
head, neck, and chest.\
\
The first step in the disinfection of the hands is the mechanical\
removal of gross surface dirt and loose epithelium by soap, a stream of\
running water as hot as can be borne, and a loofah or nail-brush, that\
has been previously sterilised by heat. The nails should be cut down\
till there is no sulcus between the nail edge and the pulp of the finger\
in which organisms may lodge. They are next washed for three minutes in\
methylated spirit to dehydrate the skin, and then for two or three\
minutes in 70 per cent. sublimate or biniodide alcohol (1 in 1000).\
Finally, the hands are rubbed with dry sterilised gauze.\
\
#Preparation of the Skin of the Patient.#--In the purification of the\
skin of the patient before operation, reliance is to be placed chiefly\
in the mechanical removal of dirt and grease by the same means as are\
taken for the cleansing of the surgeon's hands. Hair-covered parts\
should be shaved. The skin is then dehydrated by washing with methylated\
spirit, followed by 70 per cent. sublimate or biniodide alcohol (1 in\
1000). This is done some hours before the operation, and the part is\
then covered with pads of dry sterilised gauze or a sterilised towel.\
Immediately before the operation the skin is again purified in the same\
way.\
\
The _iodine method_ of disinfecting the skin introduced by Grossich is\
simple, and equally efficient. The day before operation the skin, after\
being washed with soap and water, is shaved, dehydrated by means of\
methylated spirit, and then painted with a 5 per cent. solution of\
iodine in rectified spirit. The painting with iodine is repeated just\
before the operation commences, and again after it is completed. The\
final application is omitted in the case of children. In emergency\
operations the skin is shaved dry and dehydrated with spirit, after\
which the iodine is applied as described above. The staining of the skin\
is an advantage, as it enables the operator to recognise the area that\
has been prepared.\
\
If any acne pustules or infected sinuses are present, they should be\
destroyed or purified by means of the thermo-cautery or pure carbolic\
acid, after the patient is anaesthetised.\
\
#Appliances used at Operation.#--_Instruments_ that are not damaged by\
heat must be boiled in a fish-kettle or other suitable steriliser for\
fifteen minutes in a 1 per cent. solution of cresol or washing soda.\
Just before the operation begins they are removed in the tray of the\
steriliser and placed on a sterilised towel within reach of the surgeon\
or his assistant. Knives and instruments that are liable to be damaged\
by heat should be purified by being soaked in pure cresol for a few\
minutes, or in 1 in 20 carbolic for at least an hour.\
\
_Pads of Gauze_ sterilised by compressed circulating steam have almost\
entirely superseded marine sponges for operative purposes. To avoid the\
risk of leaving swabs in the peritoneal cavity, large square pads of\
gauze, to one corner of which a piece of strong tape about a foot long\
is securely stitched, should be employed. They should be removed from\
the caskets in which they are sterilised by means of sterilised forceps,\
and handed direct to the surgeon. The assistant who attends to the swabs\
should wear sterilised gloves.\
\
_Ligatures and Sutures._--To avoid the risk of implanting infective\
matter in a wound by means of the materials used for ligatures and\
sutures, great care must be taken in their preparation.\
\
_Catgut._--The following methods of preparing catgut have proved\
satisfactory: (1) The gut is soaked in juniper oil for at least a month;\
the juniper oil is then removed by ether and alcohol, and the gut\
preserved in 1 in 1000 solution of corrosive sublimate in alcohol\
(Kocher). (2) The gut is placed in a brass receiver and boiled for\
three-quarters of an hour in a solution consisting of 85 per cent.\
absolute alcohol, 10 per cent. water, and 5 per cent. carbolic acid, and\
is then stored in 90 per cent. alcohol. (3) Cladius recommends that the\
catgut, just as it is bought from the dealers, be loosely rolled on a\
spool, and then immersed in a solution of--iodine, 1 part; iodide of\
potassium, 1 part; distilled water, 100 parts. At the end of eight days\
it is ready for use. Moschcowitz has found that the tensile strength of\
catgut so prepared is increased if it is kept dry in a sterile vessel,\
instead of being left indefinitely in the iodine solution. If\
Salkindsohn's formula is used--tincture of iodine, 1 part; proof spirit,\
15 parts--the gut can be kept permanently in the solution without\
becoming brittle. To avoid contamination from the hands, catgut should\
be removed from the bottle with aseptic forceps and passed direct to the\
surgeon. Any portion unused should be thrown away.\
\
_Silk_ is prepared by being soaked for twelve hours in ether, for other\
twelve in alcohol, and then boiled for ten minutes in 1 in 1000\
sublimate solution. It is then wound on spools with purified hands\
protected by sterilised gloves, and kept in absolute alcohol. Before an\
operation the silk is again boiled for ten minutes in the same solution,\
and is used directly from this (Kocher). Linen thread is sterilised in\
the same way as silk.\
\
Fishing-gut and silver wire, as well as the needles, should be boiled\
along with the instruments. Horse-hair and fishing-gut may be sterilised\
by prolonged immersion in 1 in 20 carbolic, or in the iodine solutions\
employed to sterilise catgut.\
\
The field of operation is surrounded by sterilised towels, clipped to\
the edges of the wound, and securely fixed in position so that no\
contamination may take place from the surroundings.\
\
The surgeon and his assistants, including the anaesthetist, wear\
overalls sterilised by steam. To avoid the risk of infection from dust,\
scurf, or drops of perspiration falling from the head, the surgeon and\
his assistants may wear sterilised cotton caps. To obviate the risk of\
infection taking place by drops of saliva projected from the mouth in\
talking or coughing in the vicinity of a wound, a simple mask may be\
worn.\
\
The risk of infection from the _air_ is now known to be very small, so\
long as there is no excess of floating dust. All sweeping, dusting, and\
disturbing of curtains, blinds, or furniture must therefore be avoided\
before or during an operation.\
\
It has been shown that the presence of spectators increases the number\
of organisms in the atmosphere. In teaching clinics, therefore, the risk\
from air infection is greater than in private practice.\
\
To facilitate primary union, all haemorrhage should be arrested, and the\
accumulation of fluid in the wound prevented. When much oozing is\
anticipated, a glass or rubber drainage-tube is inserted through a small\
opening specially made for the purpose. In aseptic wounds the tube may\
be removed in from twenty-four to forty-eight hours, and where it is\
important to avoid a scar, the opening should be closed with a Michel's\
clip; in infected wounds the tube must remain as long as the discharge\
continues.\
\
The fascia and skin should be brought into accurate apposition by\
sutures. If any cavity exists in the deeper part of the wound it should\
be obliterated by buried sutures, or by so adjusting the dressing as to\
bring its walls into apposition.\
\
If these precautions have been successful, the wound will heal under the\
original dressing, which need not be interfered with for from seven to\
ten days, according to the nature of the case.\
\
#Dressings.#--_Gauze_, sterilised by heat, is almost universally\
employed for the dressing of wounds. _Double cyanide gauze_ may be used\
in such regions as the neck, axilla, or groin, where complete\
sterilisation of the skin is difficult to attain, and where it is\
desirable to leave the dressing undisturbed for ten days or more.\
_Iodoform_ or _bismuth gauze_ is of special value for the packing of\
wounds treated by the open method.\
\
One variety or another of _wool_, rendered absorbent by the extraction\
of its fat, and sterilised by heat, forms a part of almost every\
surgical dressing, and various antiseptic agents may be added to it. Of\
these, corrosive sublimate is the most generally used. Wood-wool\
dressings are more highly and more uniformly absorbent than cotton\
wools. As evaporation takes place through wool dressings, the discharge\
becomes dried, and so forms an unfavourable medium for bacterial growth.\
\
Pads of _sphagnum moss_, sterilised by heat, are highly absorbent, and\
being economical are used when there is much discharge, and in cases\
where a leakage of urine has to be soaked up.\
\
#Means adopted to combat Infection.#--As has already been indicated, the\
same antiseptic precautions are to be taken in dealing with infected as\
with aseptic wounds.\
\
In _recent injuries_ such as result from railway or machinery accidents,\
with bruising and crushing of the tissues and grinding of gross dirt\
into the wounds, the scissors must be freely used to remove the tissues\
that have been devitalised or impregnated with foreign material.\
Hair-covered parts should be shaved and the surrounding skin painted\
with iodine. Crushed and contaminated portions of bone should be\
chiselled away. Opinions differ as to the benefit derived from washing\
such wounds with chemical antiseptics, which are liable to devitalise\
the tissues with which they come in contact, and so render them less\
able to resist the action of any organisms that may remain in them. All\
are agreed, however, that free washing with normal salt solution is\
useful in mechanically cleansing the injured parts. Peroxide of hydrogen\
sprayed over such wounds is also beneficial in virtue of its oxidising\
properties. Efficient drainage must be provided, and stitches should be\
used sparingly, if at all.\
\
The best way in which to treat such wounds is by the _open method_. This\
consists in packing the wound with iodoform or bismuth gauze, which is\
left in position as long as it adheres to the raw surface. The packing\
may be renewed at intervals until the wound is filled by granulations;\
or, in the course of a few days when it becomes evident that the\
infection has been overcome, _secondary_ sutures may be introduced and\
the edges drawn together, provision being made at the ends for further\
packing or for drainage-tubes.\
\
If earth or street dirt has entered the wound, the surface may with\
advantage be painted over with pure carbolic acid, as virulent\
organisms, such as those of tetanus or spreading gangrene, are liable to\
be present. Prophylactic injection of tetanus antitoxin may be\
indicated.\
\
\
\
\
CHAPTER XIII\
\
CONSTITUTIONAL EFFECTS OF INJURIES\
\
\
SYNCOPE--SHOCK--COLLAPSE--FAT EMBOLISM--TRAUMATIC ASPHYXIA--DELIRIUM\
    IN SURGICAL PATIENTS: _Delirium in general_; _Delirium tremens_;\
    _Traumatic delirium_.\
\
\
SYNCOPE, SHOCK, AND COLLAPSE\
\
Syncope, shock, and collapse are clinical conditions which, although\
depending on different causes, bear a superficial resemblance to one\
another.\
\
#Syncope or Fainting.#--Syncope is the result of a suddenly produced\
anaemia of the brain from temporary weakening or arrest of the heart's\
action. In surgical practice, this condition is usually observed in\
nervous persons who have been subjected to pain, as in the reduction of\
a dislocation or the incision of a whitlow; or in those who have rapidly\
lost a considerable quantity of blood. It may also follow the sudden\
withdrawal of fluid from a large cavity, as in tapping an abdomen for\
ascites, or withdrawing fluid from the pleural cavity. Syncope sometimes\
occurs also during the administration of a general anaesthetic,\
especially if there is a tendency to sickness and the patient is not\
completely under. During an operation the onset of syncope is often\
recognised by the cessation of oozing from the divided vessels before\
the general symptoms become manifest.\
\
_Clinical Features._--When a person is about to faint he feels giddy,\
has surging sounds in his ears, and haziness of vision; he yawns,\
becomes pale and sick, and a free flow of saliva takes place into the\
mouth. The pupils dilate; the pulse becomes small and almost\
imperceptible; the respirations shallow and hurried; consciousness\
gradually fades away, and he falls in a heap on the floor.\
\
Sometimes vomiting ensues before the patient completely loses\
consciousness, and the muscular exertion entailed may ward off the\
actual faint. This is frequently seen in threatened syncopal attacks\
during chloroform administration.\
\
Recovery begins in a few seconds, the patient sighing or gasping, or, it\
may be, vomiting; the strength of the pulse gradually increases, and\
consciousness slowly returns. In some cases, however, syncope is fatal.\
\
_Treatment._--The head should at once be lowered--in imitation of\
nature's method--to encourage the flow of blood to the brain, the\
patient, if necessary, being held up by the heels. All tight clothing,\
especially round the neck or chest, must be loosened. The heart may be\
stimulated reflexly by dashing cold water over the face or chest, or by\
rubbing the face vigorously with a rough towel. The application of\
volatile substances, such as ammonia or smelling-salts, to the nose; the\
administration by the mouth of sal-volatile, whisky or brandy, and the\
intra-muscular injection of ether, are the most speedily efficacious\
remedies. In severe cases the application of hot cloths over the heart,\
or of the faradic current over the line of the phrenic nerve, just above\
the clavicle, may be called for.\
\
#Surgical Shock.#--The condition known as surgical shock may be looked\
upon as a state of profound exhaustion of the mechanism that exists in\
the body for the transformation of energy. This mechanism consists of\
(1) the _brain_, which, through certain special centres, regulates all\
vital activity; (2) the _adrenal glands_, the secretion of\
which--adrenalin--acting as a stimulant of the sympathetic system, so\
controls the tone of the blood vessels as to maintain efficient\
oxidation of the tissues; and (3) _the liver_, which stores and delivers\
glycogen as it is required by the muscles, and in addition, deals with\
the by-products of metabolism.\
\
Crile and his co-workers have shown that in surgical shock histological\
changes occur in the cells of the brain, the adrenals, and the liver,\
and that these are identical, whatever be the cause that leads to the\
exhaustion of the energy-transforming mechanism. These changes vary in\
degree, and range from slight alterations in the structure of the\
protoplasm to complete disorganisation of the cell elements.\
\
The influences which contribute to bring about this form of exhaustion\
that we call shock are varied, and include such emotional states as\
fear, anxiety, or worry, physical injury and toxic infection, and the\
effects of these factors are augmented by anything that tends to lower\
the vitality, such as loss of blood, exposure, insufficient food, loss\
of sleep or antecedent illness.\
\
Any one or any combination of these influences may cause shock, but the\
most potent, and the one which most concerns the surgeon, is physical\
injury, _e.g._, a severe accident or an operation (_traumatic shock_).\
This is usually associated with some emotional disturbance, such as fear\
or anxiety (_emotional shock_), or with haemorrhage; and may be followed\
by septic infection (_toxic shock_).\
\
The exaggerated afferent impulses reaching the brain as a result of\
trauma, inhibit the action of the nuclei in the region of the fourth\
ventricle and cerebellum which maintain the muscular tone, with the\
result that the muscular tone is diminished and there is a marked fall\
in the arterial blood pressure. The capillaries dilate--the blood\
stagnating in them and giving off its oxygen and transuding its fluid\
elements into the tissues--with the result that an insufficient quantity\
of oxygenated blood reaches the heart to enable it to maintain an\
efficient circulation. As the sarco-lactic acid liberated in the muscles\
is not oxygenated a condition of acidosis ensues.\
\
The more highly the injured part is endowed with sensory nerves the more\
marked is the shock; a crush of the hand, for example, is attended with\
a more intense degree of shock than a correspondingly severe crush of\
the foot; and injuries of such specially innervated parts as the testis,\
the urethra, the face, or the spinal cord, are associated with severe\
degrees, as are also those of parts innervated from the sympathetic\
system, such as the abdominal or thoracic viscera. It is to be borne in\
mind that a state of general anaesthesia does not prevent injurious\
impulses reaching the brain and causing shock during an operation. If\
the main nerves of the part are "blocked" by injection of a local\
anaesthetic, however, the central nervous system is protected from these\
impulses.\
\
While the aged frequently manifest but few signs of shock, they have a\
correspondingly feeble power of recovery; and while many young children\
suffer little, even after severe operations, others with much less cause\
succumb to shock.\
\
When the injured person's mind is absorbed with other matters than his\
own condition,--as, for example, during the heat of a battle or in the\
excitement of a railway accident or a conflagration,--even severe\
injuries may be unattended by pain or shock at the time, although when\
the period of excitement is over, the severity of the shock is all the\
greater. The same thing is observed in persons injured while under the\
influence of alcohol.\
\
_Clinical Features._--The patient is in a state of prostration. He is\
roused from his condition of indifference with difficulty, but answers\
questions intelligently, if only in a whisper. The face is pale, beads\
of sweat stand out on the brow, the features are drawn, the eyes\
sunken, and the cheeks hollow. The lips and ears are pallid; the skin of\
the body of a greyish colour, cold, and clammy. The pulse is rapid,\
fluttering, and often all but imperceptible at the wrist; the\
respiration is irregular, shallow, and sighing; and the temperature may\
fall to 96 o F. or even lower. The mouth is parched, and the patient\
complains of thirst. There is little sensibility to pain.\
\
Except in very severe cases, shock tends towards recovery within a few\
hours, the _reaction_, as it is called, being often ushered in by\
vomiting. The colour improves; the pulse becomes full and bounding; the\
respiration deeper and more regular; the temperature rises to 100 o F. or\
higher; and the patient begins to take notice of his surroundings. The\
condition of neurasthenia which sometimes follows an operation may be\
associated with the degenerative changes in nerve cells described by\
Crile.\
\
In certain cases the symptoms of traumatic shock blend with those\
resulting from toxin absorption, and it is difficult to estimate the\
relative importance of the two factors in the causation of the\
condition. The conditions formerly known as "delayed shock" and\
"prostration with excitement" are now generally recognised to be due to\
toxaemia.\
\
_Question of Operating during Shock._--Most authorities agree that\
operations should only be undertaken during profound shock when they are\
imperatively demanded for the arrest of haemorrhage, the prevention of\
infection of serous cavities, or for the relief of pain which is\
producing or intensifying the condition.\
\
_Prevention of Operation Shock._--In the preparation of a patient for\
operation, drastic purgation and prolonged fasting must be avoided, and\
about half an hour before a severe operation a pint of saline solution\
should be slowly introduced into the rectum; this is repeated, if\
necessary, during the operation, and at its conclusion. The\
operating-room must be warm--not less than 70 o F.--and the patient\
should be wrapped in cotton wool and blankets, and surrounded by\
hot-bottles. All lotions used must be warm (100 o F.); and the operation\
should be completed as speedily and as bloodlessly as possible. The\
element of fear may to some extent be eliminated by the preliminary\
administration of such drugs as scopolamin or morphin, and with a view\
to preventing the passage of exciting afferent impulses, Crile advocates\
"blocking" of the nerves by the injection of a 1 per cent. solution of\
novocaine into their substance on the proximal side of the field of\
operation. To prevent after-pain in abdominal wounds he recommends\
injecting the edges with quinine and urea hydrochlorate before suturing,\
the resulting anaesthesia lasting for twenty-four to forty-eight hours.\
To these preventive measures the term _anoci-association_ has been\
applied. In selecting an anaesthetic, it may be borne in mind that\
chloroform lowers the blood pressure more than ether does, and that with\
spinal anaesthesia there is no lowering of the blood pressure.\
\
_Treatment._--A patient suffering from shock should be placed in the\
recumbent position, with the foot of the bed raised to facilitate the\
return circulation in the large veins, and so to increase the flow of\
blood to the brain. His bed should be placed near a large fire, and the\
patient himself surrounded by cotton wool and blankets and hot-bottles.\
If he has lost much blood, the limbs should be wrapped in cotton wool\
and firmly bandaged from below upwards, to conserve as much of the\
circulating blood as possible in the trunk and head. If the shock is\
moderate in degree, as soon as the patient has been put to bed, about a\
pint of saline solution should be introduced into the rectum, and 10 to\
15 minims of adrenalin chloride (1 in 1000) may with advantage be added\
to the fluid. The injection should be repeated every two hours until the\
circulation is sufficiently restored. In severe cases, especially when\
associated with haemorrhage, transfusion of whole blood from a compatible\
donor, is the most efficient means (_Op. Surg._, p. 37). Cardiac\
stimulants such as strychnin, digitalin, or strophanthin are\
contra-indicated in shock, as they merely exhaust the already impaired\
vaso-motor centre.\
\
Artificial respiration may be useful in tiding a patient over the\
critical period of shock, especially at the end of a severe operation.\
\
Failing this, the introduction of saline solution at a temperature of\
about 105 o F. into a vein or into the subcutaneous tissue is useful\
where much blood has been lost (p. 276). Two or three pints may be\
injected into a vein, or smaller quantities under the skin.\
\
Thirst is best met by giving small quantities of warm water by the\
mouth, or by the introduction of saline solution into the rectum. Ice\
only relieves thirst for a short time, and as it is liable to induce\
flatulence should be avoided, especially in abdominal cases. Dryness of\
the tongue may be relieved by swabbing the mouth with a mixture of\
glycerine and lemon juice.\
\
If severe pain calls for the use of morphin, 1/120th grain of atropin\
should be added, or heroin alone may be given in doses of 1/24th to\
1/12th grain.\
\
#Collapse# is a clinical condition which comes on more insidiously than\
shock, and which does not attain its maximum degree of severity for\
several hours. It is met with in the course of severe illnesses,\
especially such as are associated with the loss of large quantities of\
fluid from the body--for example, by severe diarrhoea, notably in Asiatic\
cholera; by persistent vomiting; or by profuse sweating, as in some\
cases of heat-stroke. Severe degrees of collapse follow sudden and\
profuse loss of blood.\
\
Collapse often follows upon shock--for example, in intestinal\
perforations, or after abdominal operations complicated by peritonitis,\
especially if there is vomiting, as in cases of obstruction high up in\
the intestine. The symptoms of collapse are aggravated if toxin\
absorption is superadded to the loss of fluid.\
\
The _clinical features_ of this condition are practically the same as\
those of shock; and it is treated on the same lines.\
\
FAT EMBOLISM.--After various injuries and operations, but\
especially such as implicate the marrow of long bones--for example,\
comminuted fractures, osteotomies, resections of joints, or the forcible\
correction of deformities--fluid fat may enter the circulation in\
variable quantity. In the vast majority of cases no ill effects follow,\
but when the quantity is large or when the absorption is long continued\
certain symptoms ensue, either immediately, or more frequently not for\
two or three days. These are mostly referable to the lungs and brain.\
\
In the lung the fat collects in the minute blood vessels and produces\
venous congestion and oedema, and sometimes pneumonia. Dyspnoea, with\
cyanosis, a persistent cough and frothy or blood-stained sputum, a\
feeble pulse and low temperature, are the chief symptoms.\
\
When the fat lodges in the capillaries of the brain, the pulse becomes\
small, rapid, and irregular, delirium followed by coma ensues, and the\
condition is usually rapidly fatal.\
\
Fat is usually to be detected in the urine, even in mild cases.\
\
The _treatment_ consists in tiding the patient over the acute stage of\
his illness, until the fat is eliminated from the blood vessels.\
\
TRAUMATIC ASPHYXIA OR TRAUMATIC CYANOSIS.--This term has been\
applied to a condition which results when the thorax is so forcibly\
compressed that respiration is mechanically arrested for several\
minutes. It has occurred from being crushed in a struggling crowd, or\
under a fall of masonry, and in machinery accidents. When the patient is\
released, the face and the neck as low down as the level of the\
clavicles present an intense coloration, varying from deep purple to\
blue-black. The affected area is sharply defined, and on close\
inspection the appearance is found to be due to the presence of\
countless minute reddish-blue or black spots, with small areas or\
streaks of normal skin between them. The punctate nature of the\
coloration is best recognised towards the periphery of the affected\
area--at the junction of the brow with the hairy scalp, and where the\
dark patch meets the normal skin of the chest (Beach and Cobb). Pressure\
over the skin does not cause the colour to disappear as in ordinary\
cyanosis. It has been shown by Wright of Boston, that the coloration is\
due to stasis from mechanical over-distension of the veins and\
capillaries; actual extravasation into the tissues is exceptional. The\
sharply defined distribution of the coloration is attributed to the\
absence of functionating valves in the veins of the head and neck, so\
that when the increased intra-thoracic pressure is transmitted to these\
veins they become engorged. Under the conjunctivae there are\
extravasations of bright red blood; and sublingual haematoma has been\
observed (Beatson).\
\
The discoloration begins to fade within a few hours, and after the\
second or third day it disappears, without showing any of the chromatic\
changes which characterise a bruise. The sub-conjunctival ecchymosis,\
however, persists for several weeks and disappears like other\
extravasations. Apart from combating the shock, or dealing with\
concomitant injuries, no treatment is called for.\
\
\
DELIRIUM IN SURGICAL PATIENTS\
\
Delirium is a temporary disturbance of mind which occurs in the course\
of certain diseases, and sometimes after injuries or operations. It may\
be associated with any of the acute pyogenic infections; with\
erysipelas, especially when it affects the head or face; or with chronic\
infective diseases of the urinary organs. In the various forms of\
meningitis also, and in some cases of injury to the head, it is common;\
and it is sometimes met with after severe haemorrhage, and in cases of\
poisoning by such drugs as iodoform, cocain, or alcohol. Delirium may\
also, of course, be a symptom of insanity.\
\
Often there is merely incoherent muttering regarding past incidents or\
occupations, or about absent friends; or the condition may assume the\
form of excitement, of dementia, or of melancholia; and the symptoms are\
usually worst at night.\
\
#Delirium Tremens# is seen in persons addicted to alcohol, who, as the\
result of accident or operation, are suddenly compelled to lie in bed.\
Although oftenest met with in habitual drunkards or chronic tipplers, it\
is by no means uncommon in moderate drinkers, and has even been seen in\
children.\
\
_Clinical Features._--The delirium, which has been aptly described as\
being of a "busy" character, usually manifests itself within a few days\
of the patient being laid up. For two or three days he refuses food, is\
depressed, suspicious, sleepless and restless, demanding to be allowed\
up. Then he begins to mutter incoherently, to pull off the bedclothes,\
and to attempt to get out of bed. There is general muscular tremor, most\
marked in the tongue, the lips, and the hands. The patient imagines that\
he sees all sorts of horrible beings around him, and is sometimes\
greatly distressed because of rats, mice, beetles, or snakes, which he\
fancies are crawling over him. The pulse is soft, rapid, and\
compressible; the temperature is only moderately raised (100 o-101 o F.),\
and as a rule there is profuse sweating. The digestion is markedly\
impaired, and there is often vomiting. Patients in this condition are\
peculiarly insensitive to pain, and may even walk about with a fractured\
leg without apparent discomfort.\
\
In most cases the symptoms begin to pass off in three or four days; the\
patient sleeps, the hallucinations and tremors cease, and he gradually\
recovers. In other cases the temperature rises, the pulse becomes rapid,\
and death results from exhaustion.\
\
The main indication in _treatment_ is to secure sleep, and this is done\
by the administration of bromides, chloral, or paraldehyde, or of one or\
other of the drugs of which sulphonal, trional, and veronal are\
examples. Heroin in doses of from 1/24th to 1/12th grain is often of\
service. Morphin must be used with great caution. In some cases hyoscin\
(1/200 grain) injected hypodermically is found efficacious when all\
other means have failed, but this drug must be used with great\
discrimination. The patient must be encouraged to take plenty of easily\
digested fluid food, supplemented, if necessary, by nutrient enemata and\
saline infusions.\
\
In the early stage a brisk mercurial purge is often of value. Alcohol\
should be withheld, unless failing of the pulse strongly indicates its\
use, and then it should be given along with the food.\
\
A delirious patient must be constantly watched by a trained attendant or\
other competent person, lest he get out of bed and do harm to himself or\
others. Mechanical restraint is often necessary, but must be avoided if\
possible, as it is apt to increase the excitement and exhaust the\
patient. On account of the extreme restlessness, there is often great\
difficulty in carrying out the proper treatment of the primary surgical\
condition, and considerable modifications in splints and other\
appliances are often rendered necessary.\
\
A form of delirium, sometimes spoken of as #Traumatic Delirium#, may\
follow on severe injuries or operations in persons of neurotic\
temperament, or in those whose nervous system is exhausted by overwork.\
It is met with apart from alcoholic intemperance. This form of delirium\
seems to be specially prone to ensue on operations on the face, the\
thyreoid gland, or the genito-urinary organs. The symptoms appear in\
from two to five days after the operation, and take the form of\
restlessness, sleeplessness, low incoherent muttering, and picking at\
the bedclothes. It is not necessarily attended by fever or by muscular\
tremors. The patient may show hysterical symptoms. This condition is\
probably to be regarded as a form of insanity, as it is liable to merge\
into mania or melancholia.\
\
The _treatment_ is carried out on the same lines as that of delirium\
tremens.\
\
\
\
\
CHAPTER XIV\
\
THE BLOOD VESSELS\
\
\
Anatomy--INJURIES OF ARTERIES: _Varieties_--INJURIES OF\
    VEINS: _Air Embolism_--Repair of blood vessels and natural\
    arrest of haemorrhage--HAEMORRHAGE: _Varieties_;\
    _Prevention_; _Arrest_--Constitutional effects of\
    haemorrhage--Haemophilia--DISEASES OF BLOOD VESSELS:\
    Thrombosis; Embolism--Arteritis: _Varieties_;\
    Arterio-sclerosis--Thrombo-phlebitis--Phlebitis:\
    _Varieties_--VARIX--ANGIOMATA--Naevus: _Varieties_;\
    _Electrolysis_--Cirsoid aneurysm--ANEURYSM: _Varieties_;\
    _Methods of treatment_--ANEURYSMS OF INDIVIDUAL ARTERIES.\
\
#Surgical Anatomy.#--An _artery_ has three coats: an internal coat--the\
_tunica intima_--made up of a single layer of endothelial cells lining\
the lumen; outside of this a layer of delicate connective tissue; and\
still farther out a dense tissue composed of longitudinally arranged\
elastic fibres--the internal elastic lamina. The tunica intima is easily\
ruptured. The middle coat, or _tunica media_, consists of non-striped\
muscular fibres, arranged for the most part concentrically round the\
vessel. In this coat also there is a considerable proportion of elastic\
tissue, especially in the larger vessels. The thickness of the vessel\
wall depends chiefly on the development of the muscular coat. The\
external coat, or _tunica externa_, is composed of fibrous tissue,\
containing, especially in vessels of medium calibre, some yellow elastic\
fibres in its deeper layers.\
\
In most parts of the body the arteries lie in a sheath of connective\
tissue, from which fine fibrous processes pass to the tunica externa.\
The connection, however, is not a close one, and the artery when divided\
transversely is capable of retracting for a considerable distance within\
its sheath. In some of the larger arteries the sheath assumes the form\
of a definite membrane.\
\
The arteries are nourished by small vessels--the _vasa vasorum_--which\
ramify chiefly in the outer coat. They are also well supplied with\
nerves, which regulate the size of the lumen by inducing contraction or\
relaxation of the muscular coat.\
\
The _veins_ are constructed on the same general plan as the arteries,\
the individual coats, however, being thinner. The inner coat is less\
easily ruptured, and the middle coat contains a smaller proportion of\
muscular tissue. In one important point veins differ structurally from\
arteries--namely, in being provided with valves which prevent reflux of\
the blood. These valves are composed of semilunar folds of the tunica\
intima strengthened by an addition of connective tissue. Each valve\
usually consists of two semilunar flaps attached to opposite sides of\
the vessel wall, each flap having a small sinus on its cardiac side.\
The distension of these sinuses with blood closes the valve and\
prevents regurgitation. Valves are absent from the superior and inferior\
venae cavae, the portal vein and its tributaries, the hepatic, renal,\
uterine, and spermatic veins, and from the veins in the lower part of\
the rectum. They are ill-developed or absent also in the iliac and\
common femoral veins--a fact which has an important bearing on the\
production of varix in the veins of the lower extremity.\
\
The wall of _capillaries_ consists of a single layer of endothelial\
cells.\
\
\
HAEMORRHAGE\
\
Various terms are employed in relation to haemorrhage, according to its\
seat, its origin, the time at which it occurs, and other circumstances.\
\
The term _external haemorrhage_ is employed when the blood escapes on the\
surface; when the bleeding takes place into the tissues or into a cavity\
it is spoken of as _internal_. The blood may infiltrate the connective\
tissue, constituting an _extravasation_ of blood; or it may collect in a\
space or cavity and form a _haematoma_.\
\
The coughing up of blood from the lungs is known as _haemoptysis_;\
vomiting of blood from the stomach, as _haematemesis_; the passage of\
black-coloured stools due to the presence of blood altered by digestion,\
as _melaena_; and the passage of bloody urine, as _haematuria_.\
\
Haemorrhage is known as arterial, venous, or capillary, according to the\
nature of the vessel from which it takes place.\
\
In _arterial_ haemorrhage the blood is bright red in colour, and escapes\
from the cardiac end of the divided vessel in pulsating jets\
synchronously with the systole of the heart. In vascular parts--for\
example the face--both ends of a divided artery bleed freely. The blood\
flowing from an artery may be dark in colour if the respiration is\
impeded. When the heart's action is weak and the blood tension low the\
flow may appear to be continuous and not in jets. The blood from a\
divided artery at the bottom of a deep wound, escapes on the surface in\
a steady flow.\
\
_Venous_ bleeding is not pulsatile, but occurs in a continuous stream,\
which, although both ends of the vessel may bleed, is more copious from\
the distal end. The blood is dark red under ordinary conditions, but may\
be purplish, or even black, if the respiration is interfered with. When\
one of the large veins in the neck is wounded, the effects of\
respiration produce a rise and fall in the stream which may resemble\
arterial pulsation.\
\
In _capillary_ haemorrhage, red blood escapes from numerous points on the\
surface of the wound in a steady ooze. This form of bleeding is serious\
in those who are the subjects of haemophilia.\
\
\
INJURIES OF ARTERIES\
\
The following description of the injuries of arteries refers to the\
larger, named trunks. The injuries of smaller, unnamed vessels are\
included in the consideration of wounds and contusions.\
\
#Contusion.#--An artery may be contused by a blow or crush, or by the\
oblique impact of a bullet. The bruising of the vessel wall, especially\
if it is diseased, may result in the formation of a thrombus which\
occludes the lumen temporarily or even permanently, and in rare cases\
may lead to gangrene of the limb beyond.\
\
#Subcutaneous Rupture.#--An artery may be ruptured subcutaneously by a\
blow or crush, or by a displaced fragment of bone. This injury has been\
produced also during attempts to reduce dislocations, especially those\
of old standing at the shoulder. It is most liable to occur when the\
vessels are diseased. The rupture may be incomplete or complete.\
\
_Incomplete Subcutaneous Rupture._--In the majority of cases the rupture\
is incomplete--the inner and middle coats being torn, while the outer\
remains intact. The middle coat contracts and retracts, and the\
internal, because of its elasticity, curls up in the interior of the\
vessel, forming a valvular obstruction to the blood-flow. In most cases\
this results in the formation of a thrombus which occludes the vessel.\
In some cases the blood-pressure gradually distends the injured segment\
of the vessel wall and leads to the formation of an aneurysm.\
\
The pulsation in the vessels beyond the seat of rupture is arrested--for\
a time at least--owing to the occlusion of the vessel, and the limb\
becomes cold and powerless. The pulsation seldom returns within five or\
six weeks of the injury, if indeed it is not permanently arrested, but,\
as a rule, a collateral circulation is rapidly established, sufficient\
to nourish the parts beyond. If the pulsation returns within a week of\
the injury, the presumption is that the occlusion was due to pressure\
from without--for example, by haemorrhage into the sheath or the pressure\
of a fragment of bone.\
\
_Complete Subcutaneous Rupture._--When the rupture is complete, all the\
coats of the vessel are torn and the blood escapes into the surrounding\
tissues. If the original injury is attended with much shock, the\
bleeding may not take place until the period of reaction. Rupture of the\
popliteal artery in association with fracture of the femur, or of the\
axillary or brachial artery with fracture of the humerus or dislocation\
of the shoulder, are familiar examples of this injury.\
\
Like incomplete rupture, this lesion is accompanied by loss of pulsation\
and power, and by coldness of the limb beyond; a tense and excessively\
painful swelling rapidly appears in the region of the injury, and, where\
the cellular tissue is loose, may attain a considerable size. The\
pressure of the effused blood occludes the veins and leads to congestion\
and oedema of the limb beyond. The interference with the circulation, and\
the damage to the tissues, may be so great that gangrene ensues.\
\
_Treatment._--When an artery has been contused or ruptured, the limb\
must be placed in the most favourable condition for restoration of the\
circulation. The skin is disinfected and the limb wrapped in cotton wool\
to conserve its heat, and elevated to such an extent as to promote the\
venous return without at the same time interfering with the inflow of\
blood. A careful watch must be kept on the state of nutrition of the\
limb, lest gangrene occurs.\
\
If no complications supervene, the swelling subsides, and recovery may\
be complete in six or eight weeks. If the extravasation is great and the\
skin threatens to give way, or if the vitality of the limb is seriously\
endangered, it is advisable to expose the injured vessel, and, after\
clearing away the clots, to attempt to suture the rent in the artery,\
or, if torn across, to join the ends after paring the bruised edges. If\
this is impracticable, a ligature is applied above and below the\
rupture. If gangrene ensues, amputation must be performed.\
\
These descriptions apply to the larger arteries of the extremities. A\
good illustration of subcutaneous rupture of the arteries of the head is\
afforded by the tearing of the middle meningeal artery caused by the\
application of blunt violence to the skull; and of the arteries of the\
trunk--caused by the tearing of the renal artery in rupture of the\
kidney.\
\
#Open Wounds of Arteries--Laceration.#--Laceration of large arteries is\
a common complication of machinery and railway accidents. The violence\
being usually of a tearing, twisting, or crushing nature, such injuries\
are seldom associated with much haemorrhage, as torn or crushed vessels\
quickly become occluded by contraction and retraction of their coats and\
by the formation of a clot. A whole limb even may be avulsed from the\
body with comparatively little loss of blood. The risk in such cases is\
secondary haemorrhage resulting from pyogenic infection.\
\
The _treatment_ is that applicable to all wounds, with, in addition, the\
ligation of the lacerated vessels.\
\
#Punctured wounds# of blood vessels may result from stabs, or they may\
be accidentally inflicted in the course of an operation.\
\
The division of the coats of the vessel being incomplete, the natural\
haemostasis that results from curling up of the intima and contraction of\
the media, fails to take place, and bleeding goes on into the\
surrounding tissues, and externally. If the sheath of the vessel is not\
widely damaged, the gradually increasing tension of the extravasated\
blood retained within it may ultimately arrest the haemorrhage. A clot\
then forms between the lips of the wound in the vessel wall and projects\
for a short distance into the lumen, without, however, materially\
interfering with the flow through the vessel. The organisation of this\
clot results in the healing of the wound in the vessel wall.\
\
In other cases the blood escapes beyond the sheath and collects in the\
surrounding tissues, and a traumatic aneurysm results. Secondary\
haemorrhage may occur if the wound becomes infected.\
\
The _treatment_ consists in enlarging the external wound to permit of\
the damaged vessel being ligated above and below the puncture. In some\
cases it may be possible to suture the opening in the vessel wall. When\
circumstances prevent these measures being taken, the bleeding may be\
arrested by making firm pressure over the wound with a pad; but this\
procedure is liable to be followed by the formation of an aneurysm.\
\
_Minute puncture of arteries_ such as frequently occur in the hypodermic\
administration of drugs and in the use of exploring needles, are not\
attended with any escape of blood, chiefly because of the elastic recoil\
of the arterial wall; a tiny thrombus of platelets and thrombus forms at\
the point where the intima is punctured.\
\
#Incised Wounds.#--We here refer only to such incised wounds as partly\
divide the vessel wall.\
\
Longitudinal wounds show little tendency to gape, and are therefore not\
attended with much bleeding. They usually heal rapidly, but, like\
punctured wounds, are liable to be followed by the formation of an\
aneurysm.\
\
When, however, the incision in the vessel wall is oblique or transverse,\
the retraction of the muscular coat causes the opening to gape, with the\
result that there is haemorrhage, which, even in comparatively small\
arteries, may be so profuse as to prove dangerous. When the associated\
wound in the soft parts is valvular the haemorrhage is arrested and an\
aneurysm may develop.\
\
When a large arterial trunk, such as the external iliac, the femoral,\
the common carotid, the brachial, or the popliteal, has been partly\
divided, for example, in the course of an operation, the opening should\
be closed with sutures--_arteriorrhaphy_. The circulation being\
controlled by a tourniquet, or the artery itself occluded by a clamp,\
fine silk or catgut stitches are passed through the outer and middle\
coats after the method of Lembert, a fine, round needle being employed.\
The sheath of the vessel or an adjacent fascia should be stitched\
over the line of suture in the vessel wall. If infection be excluded,\
there is little risk of thrombosis or secondary haemorrhage; and even if\
thrombosis should develop at the point of suture, the artery is\
obstructed gradually, and the establishment of a collateral circulation\
takes place better than after ligation. In the case of smaller trunks,\
or when suture is impracticable, the artery should be tied above and\
below the opening, and divided between the ligatures.\
\
#Gunshot Wounds of Blood Vessels.#--In the majority of cases injuries of\
large vessels are associated with an external wound; the profusion of\
the bleeding indicates the size of the damaged vessel, and the colour of\
the blood and the nature of the flow denote whether an artery or a vein\
is implicated.\
\
When an artery is wounded a firm _haematoma_ may form, with an expansile\
pulsation and a palpable thrill--whether such a haematoma remains\
circumscribed or becomes diffuse depends upon the density or laxity of\
the tissues around it. In course of time a _traumatic arterial aneurysm_\
may develop from such a haematoma.\
\
When an artery and its companion vein are injured simultaneously an\
_arterio-venous aneurysm_ (p. 310) may develop. This frequently takes\
place without the formation of a haematoma as the arterial blood finds\
its way into the vein and so does not escape into the tissues. Even if a\
haematoma forms it seldom assumes a great size. In time a swelling is\
recognised, with a palpable thrill and a systolic bruit, loudest at the\
level of the communication and accompanied by a continuous venous hum.\
\
If leakage occurs into the tissues, the extravasated blood may occlude\
the vein by pressure, and the symptoms of arterial aneurysm replace\
those of the arterio-venous form, the systolic bruit persisting, while\
the venous hum disappears.\
\
_Gangrene_ may ensue if the blood supply is seriously interfered with,\
or the signs of _ischaemia_ may develop; the muscles lose their\
elasticity, become hard and paralysed, and anaesthesia of the "glove" or\
"stocking" type, with other alterations of sensation ensue. Apart from\
ischaemia, _reflex paralysis_ of motion and sensation of a transient kind\
may follow injury of a large vessel.\
\
_Treatment_ is carried out on the same lines as for similar injuries due\
to other causes.\
\
\
INJURIES OF VEINS\
\
Veins are subject to the same forms of injury as arteries, and the\
results are alike in both, such variations as occur being dependent\
partly on the difference in their anatomical structure, and partly on\
the conditions of the circulation through them.\
\
#Subcutaneous rupture# of veins occur most frequently in association\
with fractures and in the reduction of dislocations. The veins most\
commonly ruptured are the popliteal, the axillary, the femoral, and the\
subclavian. On account of the smaller amount of elastic and muscular\
tissue in the wall of a vein, the contraction and retraction of its\
walls are less than in an artery, and so bleeding may continue for a\
longer period. On the other hand, owing to the lower blood-pressure the\
outflow goes on more slowly, and the gradually increasing pressure\
produced by the extravasated blood is usually sufficient to arrest the\
haemorrhage before it becomes serious. As an aid in diagnosing the source\
of the bleeding, it should be remembered that the rupture of a vein does\
not affect the pulsation in the limb beyond. The risks are practically\
the same as when an artery is ruptured, excepting that of aneurysm, and\
the treatment is carried out on the same lines, but it is seldom\
necessary to operate for the purpose of applying a ligature to the\
injured vein.\
\
#Wounds# of veins--punctured and incised--frequently occur in the course\
of operations; for example, in the removal of tumours or diseased glands\
from the neck, the axilla, or the groin. They are also met with as a\
result of accidental stabs and of suicidal or homicidal injuries. The\
haemorrhage from a large vein so damaged is usually profuse, but it is\
more readily controlled by external pressure than that from an artery.\
When a vein is merely punctured, the bleeding may be arrested by\
pressure with a pad of gauze, or by a lateral ligature--that is, picking\
up the margins of the rent in the wall and securing them with a\
ligature without occluding the lumen. In the large veins, such as the\
internal jugular, the femoral, or the axillary, it is usually possible\
to suture the opening in the wall. This does not necessarily result in\
thrombosis in the vessel, or in obliteration of its lumen.\
\
When an _artery and vein are simultaneously wounded_, the features\
peculiar to each are present in greater or less degree. In the limbs\
gangrene may ensue, especially if the wound is infected. Punctured and\
gun-shot wounds implicating both artery and vein are liable to be\
followed by the development of arterio-venous aneurysm.\
\
#Entrance of Air into Veins--Air Embolism.#--This serious, though\
fortunately rare, accident is apt to occur in the course of operations\
in the region of the thorax, neck, or axilla, if a large vein is opened\
and fails to collapse on account of the rigidity of its walls, its\
incorporation in a dense fascia, or from traction being made upon it. If\
the wound in a vein is thus held open, the negative pressure during\
inspiration sucks air into the right side of the heart. This is\
accompanied by a hissing or gurgling sound, and with the next expiration\
some frothy blood escapes from the wound. The patient instantly becomes\
pale, the pupils dilate, respiration becomes laboured, and although the\
heart may continue to beat forcibly, the peripheral pulse is weak, and\
may even be imperceptible. On auscultating the heart, a churning sound\
may be heard. Death may result in a few minutes; or the heart may slowly\
regain its power and recovery take place.\
\
_Prevention._--In operations in the "dangerous area"--as the region of\
the root of the neck is called in this connection--care must be taken\
not to cut or divide any vein before it has been secured by forceps, and\
to apply ligatures securely and at once. Deep wounds in this region\
should be kept filled with normal salt solution. Immediately a cut is\
recognised in a vein, a finger should be placed over the vessel on the\
cardiac side of the wound, and kept there until the opening is secured.\
\
_Treatment._--Little can be done after the air has actually entered the\
vein beyond endeavouring to maintain the heart's action by hypodermic\
injections of ether or strychnin and the application of mustard or hot\
cloths over the chest. The head at the same time should be lowered to\
prevent syncope. Attempts to withdraw the air by suction, and the\
employment of artificial respiration, have proved futile, and are, by\
some, considered dangerous. In a desperate case massage of the heart\
might be tried.\
\
\
THE NATURAL ARREST OF HAEMORRHAGE AND THE REPAIR OF BLOOD\
VESSELS\
\
#Primary Haemorrhage.#--The term primary haemorrhage is applied to the\
bleeding which follows immediately on the wounding of a blood vessel.\
The natural process by which such haemorrhage is arrested varies with the\
character of the wound in the vessel and may be modified by accidental\
circumstances.\
\
(a) _Repair of completely divided Artery._--When an artery is\
_completely_ divided, the circular fibres of the muscular coat contract,\
so that the lumen of the cut ends is diminished, and at the same time\
each segment retracts within its sheath in virtue of the recoil of the\
elastic elements in its walls, the tunica intima curls up in the\
interior of the vessel, and the tunica externa collapses over the cut\
ends. The blood that escapes from the injured vessel fills the\
interstices of the tissues, and, coagulating, forms a clot which\
temporarily arrests the bleeding. That part of the clot which lies\
between the divided ends of the vessel and in the cellular tissue\
outside, is known as the _external clot_, while the portion which\
projects into the lumen of the vessel is known as the _internal clot_,\
and it usually extends as far as the nearest collateral branch. These\
processes constitute what is known as the _temporary arrest of\
haemorrhage_, which, it will be observed, is effected by the contraction\
and retraction of the divided artery and by clotting.\
\
The _permanent arrest_ takes place by the transformation of the clot\
into scar tissue. The internal clot plays the most important part in the\
process; it becomes invaded by leucocytes and proliferating endothelial\
and connective-tissue cells, and new blood vessels permeate the mass,\
which is thus converted into granulation tissue. This is ultimately\
replaced by fibrous tissue, which permanently occludes the end of the\
vessel. Concurrently and by the same process the external clot is\
converted into scar tissue.\
\
If a divided artery is _ligated at its cut end_, the tension of the\
ligature is usually sufficient to rupture the inner and middle coats,\
which curl up within the lumen, the outer coat alone being held in the\
grasp of the ligature. An internal clot forms and, becoming organised,\
permanently occludes the vessel as above described. The ligature and the\
small portion of vessel beyond it are subsequently absorbed.\
\
In course of time the collateral branches of the vessel above and below\
the level of section enlarge and their inter-communication becomes more\
free, so that even when large trunks have been divided the vascular\
supply of the parts beyond may be completely restored. This is known as\
the development of the _collateral circulation_.\
\
_Imperfect Collateral Circulation._--While the development of the\
collateral circulation after the ligation or obstruction from other\
cause of a main arterial trunk may be sufficient to prevent gangrene of\
the limb, it may be insufficient for its adequate nourishment; it may be\
cold, bluish in colour, and there may be necrosis of the skin over bony\
points; this is notably the case in the lower extremity after ligation\
of the femoral or popliteal artery, when patches of skin may die over\
the prominence of the heel, the balls of the toes, the projecting base\
of the fifth metatarsal and the external malleolus.\
\
If, during the period of reaction, the blood-pressure rises\
\
considerably, the occluding clot at the divided end of the vessel may be\
washed away or the ligature displaced, permitting of fresh bleeding\
taking place--_reactionary_ or _intermediary haemorrhage_ (p. 272).\
\
In the event of the wound becoming infected with pyogenic organisms, the\
occluding blood-clot or the young fibrous tissue may become\
disintegrated in the suppurative process, and the bleeding start\
afresh--_secondary haemorrhage_ (p. 273).\
\
(b) If an artery is only _partly cut across_, the divided fibres of\
the tunica muscularis contract and those of the tunica externa retract,\
with the result that a more or less circular hole is formed in the wall\
of the vessel, from which free bleeding takes place, as the conditions\
are unfavourable for the formation of an occluding clot. Even if a clot\
does form, when the blood-pressure rises it is readily displaced,\
leading to reactionary haemorrhage. Should the wound become infected,\
secondary haemorrhage is specially liable to occur. A further risk\
attends this form of injury, in that the intra-vascular tension may in\
time lead to gradual stretching of the scar tissue which closes the gap\
in the vessel wall, with the result that a localised dilatation or\
diverticulum forms, constituting a _traumatic aneurysm_.\
\
(c) When the injury merely takes the form of a _puncture_ or _small\
incision_ a blood-clot forms between the edges, becomes organised, and\
is converted into cicatricial tissue which seals the aperture. Such\
wounds may also be followed by reactionary or secondary haemorrhage, or\
later by the formation of a traumatic aneurysm.\
\
_Conditions which influence the Natural Arrest of Haemorrhage._--The\
natural arrest of bleeding is favoured by tearing or crushing of the\
vessel walls, owing to the contraction and retraction of the coats and\
the tendency of blood to coagulate when in contact with damaged tissue.\
Hence the primary haemorrhage following lacerated wounds is seldom\
copious. The occurrence of syncope or of profound shock also helps to\
stop bleeding by reducing the force of the heart's action.\
\
On the other hand, there are conditions which retard the natural arrest.\
When, for example, a vessel is only partly divided, the contraction and\
retraction of the muscular coat, instead of diminishing the calibre of\
the artery, causes the wound in the vessel to gape; by completing the\
division of the vessel under these circumstances the bleeding can often\
be arrested. In certain situations, also, the arteries are so intimately\
connected with their sheaths, that when cut across they were unable to\
retract and contract--for example, in the scalp, in the penis, and in\
bones--and copious bleeding may take place from comparatively small\
vessels. This inability of the vessels to contract and retract is met\
with also in inflamed and oedematous parts and in scar tissue. Arteries\
divided in the substance of a muscle also sometimes bleed unduly. Any\
increase in the force of the heart's action, such as may result from\
exertion, excitement, or over-stimulation, also interferes with the\
natural arrest. Lastly, in bleeders, there are conditions which\
interfere with the natural arrest of haemorrhage.\
\
#Repair of a Vessel ligated in its Continuity.#--When a ligature is\
applied to an artery it should be pulled sufficiently tight to occlude\
the lumen without causing rupture of its coats. It often happens,\
however, that the compression causes rupture of the inner and middle\
coats, so that only the outer coat remains in the grasp of the ligature.\
While this weakens the wall of the vessel, it has the advantage of\
hastening coagulation, by bringing the blood into contact with damaged\
tissue. Whether the inner and middle coats are ruptured or not, blood\
coagulates both above and below the ligature, the proximal clot being\
longer and broader than that on the distal side. In small arteries these\
clots extend as far as the nearest collateral branch, but in the larger\
trunks their length varies. The permanent occlusion of those portions of\
the vessel occupied by clot is brought about by the formation of\
granulation tissue, and its replacement by cicatricial tissue, so that\
the occluded segment of the vessel is represented by a fibrous cord. In\
this process the coagulum only plays a passive role by forming a\
scaffolding on which the granulation tissue is built up. The ligature\
surrounding the vessel, and the elements of the clot, are ultimately\
absorbed.\
\
#Repair of Veins.#--The process of repair in veins is the same as that\
in arteries, but the thrombosed area may become canalised and the\
circulation through the vessel be re-established.\
\
\
HAEMORRHAGE IN SURGICAL OPERATIONS\
\
The management of the haemorrhage which accompanies an operation includes\
(a) preventive measures, and (b) the arrest of the bleeding.\
\
#Prevention of Haemorrhage.#--Whenever possible, haemorrhage should be\
controlled by _digital compression_ of the main artery supplying the\
limb rather than by a tourniquet. If efficiently applied compression\
reduces the immediate loss of blood to a minimum, and the bleeding from\
small vessels that follows the removal of the tourniquet is avoided.\
Further, the pressure of a tourniquet has been shown to be a material\
factor in producing shock.\
\
In selecting a point at which to apply digital compression, it is\
essential that the vessel should be lying over a bone which will furnish\
the necessary resistance. The common carotid, for example, is pressed\
backward and medially against the transverse process (carotid tubercle)\
of the sixth cervical vertebra; the temporal against the temporal\
process (zygoma) in front of the ear; and the facial against the\
mandible at the anterior edge of the masseter.\
\
In the upper extremity, the subclavian is pressed against the first rib\
by making pressure downwards and backwards in the hollow above the\
clavicle; the axillary and brachial by pressing against the shaft of the\
humerus.\
\
In the lower extremity, the femoral is controlled by pressing in a\
direction backward and slightly upward against the brim of the pelvis,\
midway between the symphysis pubis and the anterior superior iliac\
spine.\
\
The abdominal aorta may be compressed against the bodies of the lumbar\
vertebrae opposite the umbilicus, if the spine is arched well forwards\
over a pillow or sand-bag, or by the method suggested by Macewen, in\
which the patient's spine is arched forwards by allowing the lower\
extremities and pelvis to hang over the end of the table, while the\
assistant, standing on a stool, applies his closed fist over the\
abdominal aorta and compresses it against the vertebral column.\
Momburg recommends an elastic cord wound round the body between the\
iliac crest and the lower border of the ribs, but this procedure has\
caused serious damage to the intestine.\
\
When digital compression is not available, the most convenient and\
certain means of preventing haemorrhage--say in an amputation--is by the\
use of some form of _tourniquet_, such as the elastic tube of Esmarch or\
of Foulis, or an elastic bandage, or the screw tourniquet of Petit.\
Before applying any of these it is advisable to empty the limb of blood.\
This is best done after the manner suggested by Lister: the limb is held\
vertical for three or four minutes; the veins are thus emptied by\
gravitation, and they collapse, and as a physiological result of this\
the arteries reflexly contract, so that the quantity of blood entering\
the limb is reduced to a minimum. With the limb still elevated the\
tourniquet is firmly applied, a part being selected where the vessel can\
be pressed directly against a bone, and where there is no risk of\
exerting injurious pressure on the nerve-trunks. The tourniquet should\
be applied over several layers of gauze or lint to protect the skin, and\
the first turn of the tourniquet must be rapidly and tightly applied to\
arrest completely the arterial flow, otherwise the veins only are\
obstructed and the limb becomes congested. In the lower extremity the\
best place to apply a tourniquet is the middle third of the thigh; in\
the upper extremity, in the middle of the arm. A tourniquet should never\
be applied tighter or left on longer than is absolutely necessary.\
\
The screw tourniquet of Petit is to be preferred when it is desired to\
intermit the flow through the main artery as in operations for aneurysm.\
\
When a tourniquet cannot conveniently be applied, or when its presence\
interferes with the carrying out of the operation--as, for example, in\
amputations at the hip or shoulder--the haemorrhage may be controlled by\
preliminary ligation of the main artery above the seat of operation--for\
instance, the external iliac or the subclavian. For such contingencies\
also the steel skewers used by Spence and Wyeth, or a special clamp or\
forceps, such as that suggested by Lynn Thomas, may be employed. In the\
case of vessels which it is undesirable to occlude permanently, such as\
the common carotid, the temporary application of a ligature or clamp is\
useful.\
\
#Arrest of Haemorrhage.#--_Ligature._--This is the best means of securing\
the larger vessels. The divided vessel having been caught with forceps\
as near to its cut end as possible, a ligature of catgut or silk is tied\
round it. When there is difficulty in applying a ligature securely, for\
example in a dense tissue like the scalp or periosteum, or in a friable\
tissue like the thyreoid gland or the mesentery, a stitch should be\
passed so as to surround the bleeding vessel a short distance from its\
end, in this way ensuring a better hold and preventing the ligature from\
slipping.\
\
If the haemorrhage is from a partly divided vessel, this should be\
completely cut across to enable its walls to contract and retract, and\
to facilitate the application of forceps and ligatures.\
\
_Torsion._--This method is seldom employed except for comparatively\
small vessels, but it is applicable to even the largest arteries. In\
employing torsion, the end of the vessel is caught with forceps, and the\
terminal portion twisted round several times. The object is to tear the\
inner and middle coats so that they curl up inside the lumen, while the\
outer fibrous coat is twisted into a cord which occludes the end of the\
vessel.\
\
_Forci-pressure._--Bleeding from the smallest arteries and from\
arterioles can usually be arrested by firmly squeezing them for a few\
minutes with artery forceps. It is usually found that on the removal of\
the forceps at the end of an operation no further haemorrhage takes\
place. By the use of specially strong clamps, such as the angiotribes of\
Doyen, large trunks may be occluded by pressure.\
\
_Cautery._--The actual cautery or Paquelin's thermo-cautery is seldom\
employed to arrest haemorrhage, but is frequently useful in preventing\
it, as, for example, in the removal of piles, or in opening the bowel in\
colostomy. It is used at a dull-red heat, which sears the divided ends\
of the vessel and so occludes the lumen. A bright-red or a white heat\
cuts the vessel across without occluding it. The separation of the\
slough produced by the charring of the tissues is sometimes attended\
with secondary bleeding.\
\
_Haemostatics_ or _Styptics_.--The local application of haemostatics is\
seldom to be recommended. In the treatment of epistaxis or bleeding from\
the nose, of haemorrhage from the socket of a tooth, and sometimes from\
ulcerating or granulating surfaces, however, they may be useful. All\
clots must be removed and the drug applied directly to the bleeding\
surface. Adrenalin and turpentine are the most useful drugs for this\
purpose.\
\
Haemorrhage from bone, for example the skull, may be arrested by means of\
Horsley's aseptic plastic wax. To stop persistent oozing from soft\
tissues, Horsley successfully applied a portion of living vascular\
tissue, such as a fragment of muscle, which readily adheres to the\
oozing surface and yields elements that cause coagulation of the blood\
by thrombo-kinetic processes. When examined after two or three days the\
muscle has been found to be closely adherent and undergoing\
organisation.\
\
#Arrest of Accidental Haemorrhage.#--The most efficient means of\
temporarily controlling haemorrhage is by pressure applied with the\
finger, or with a pad of gauze, directly over the bleeding point. While\
this is maintained an assistant makes digital pressure, or applies a\
tourniquet, over the main vessel of the limb on the proximal side of the\
bleeding point. A useful _emergency tourniquet_ may be improvised by\
folding a large handkerchief _en cravatte_, with a cork or piece of wood\
in the fold to act as a pad. The handkerchief is applied round the\
limb, with the pad over the main artery, and the ends knotted on the\
lateral aspect of the limb. With a strong piece of wood the handkerchief\
is wound up like a Spanish windlass, until sufficient pressure is\
exerted to arrest the bleeding.\
\
When haemorrhage is taking place from a number of small vessels, its\
arrest may be effected by elevation of the bleeding part, particularly\
if it is a limb. By this means the force of the circulation is\
diminished and the formation of coagula favoured. Similarly, in wounds\
of the hand or forearm, or of the foot or leg, bleeding may be arrested\
by placing a pad in the flexure and acutely flexing the limb at the\
elbow or knee respectively.\
\
#Reactionary Haemorrhage.#--Reactionary or intermediary haemorrhage\
is really a recurrence of primary bleeding. As the name indicates, it\
occurs during the period of reaction--that is, within the first twelve\
hours after an operation or injury. It may be due to the increase in the\
blood-pressure that accompanies reaction displacing clots which have\
formed in the vessels, or causing vessels to bleed which did not bleed\
during the operation; to the slipping of a ligature; or to the giving\
way of a grossly damaged portion of the vessel wall. In the scrotum, the\
relaxation of the dartos during the first few hours after operation\
occasionally leads to reactionary haemorrhage.\
\
As a rule, reactionary haemorrhage takes place from small vessels as a\
result of the displacement of occluding clots, and in many cases the\
haemorrhage stops when the bandages and soaked dressings are removed. If\
not, it is usually sufficient to remove the clots and apply firm\
pressure, and in the case of a limb to elevate it. Should the haemorrhage\
recur, the wound must be reopened, and ligatures applied to the bleeding\
vessels. Douching the wound with hot sterilised water (about 110 o F.),\
and plugging it tightly with gauze, are often successful in arresting\
capillary oozing. When the bleeding is more copious, it is usually due\
to a ligature having slipped from a large vessel such as the external\
jugular vein after operations in the neck, and the wound must be opened\
up and the vessel again secured. The internal administration of heroin\
or morphin, by keeping the patient quiet, may prove useful in preventing\
the recurrence of haemorrhage.\
\
#Secondary Haemorrhage.#--The term secondary haemorrhage refers to\
bleeding that is delayed in its onset and is due to pyogenic infection\
of the tissues around an artery. The septic process causes softening and\
erosion of the wall of the artery so that it gives way under the\
pressure of the contained blood. The leakage may occur in drops, or as a\
rush of blood, according to the extent of the erosion, the size of the\
artery concerned, and the relations of the erosion to the surrounding\
tissues. When met with as a complication of a wound there is an\
interval--usually a week to ten days--between the receipt of the wound\
and the first haemorrhage, this time being required for the extension of\
the septic process to the wall of the artery and the consequent erosion\
of its coats. When secondary haemorrhage occurs apart from a wound, there\
is a similar septic process attacking the wall of the artery from the\
outside; for example in sloughing sore-throat, the separation of a\
slough may implicate the wall of an artery and be followed by serious\
and it may be fatal haemorrhage. The mechanical pressure of a fragment of\
bone or of a rubber drainage tube upon the vessel may aid the septic\
process in causing erosion of the artery. In pre-Listerian days, the\
silk ligature around the artery likewise favoured the changes that lead\
to secondary haemorrhage, and the interesting observation was often made,\
that when the collateral circulation was well established, the leakage\
occurred on the _distal_ side of the ligature. While it may happen that\
the initial haemorrhage is rapidly fatal, as for example when the\
external carotid or one of its branches suddenly gives way, it is quite\
common to have one, two or more _warning haemorrhages_ before the leakage\
on a large scale, which is rapidly fatal.\
\
The _appearances of the wound_ in cases complicated by secondary\
haemorrhage are only characteristic in so far that while obviously\
infected, there is an absence of all reaction; instead of frankly\
suppurating, there is little or no discharge and the surrounding\
cellular tissue and the limb beyond are oedematous and pit on pressure.\
\
The _general symptoms_ of septic poisoning in cases of secondary\
haemorrhage vary widely in severity: they may be so slight that the\
general health is scarcely affected and the convalescence from an\
operation, for example, may be apparently normal except that the wound\
does not heal satisfactorily. For example, a patient may be recovering\
from an operation such as the removal of an epithelioma of the mouth,\
pharynx or larynx and the associated lymph glands in the neck, and be\
able to be up and going about his room, when, suddenly, without warning\
and without obvious cause, a rush of blood occurs from the mouth or the\
incompletely healed wound in the neck, causing death within a few\
minutes.\
\
On the other hand, the toxaemia may be of a profound type associated with\
marked pallor and progressive failure of strength, which, of itself,\
even when the danger from haemorrhage has been overcome, may have a fatal\
termination. The _prognosis_ therefore in cases of secondary haemorrhage\
can never be other than uncertain and unfavourable; the danger from loss\
of blood _per se_ is less when the artery concerned is amenable to\
control by surgical measures.\
\
_Treatment._--The treatment of secondary haemorrhage includes the use of\
local measures to arrest the bleeding, the employment of general\
measures to counteract the accompanying toxaemia, and when the loss of\
blood has been considerable, the treatment of the bloodless state.\
\
_Local Measures to arrest the Haemorrhage._--The occurrence of even\
slight haemorrhages from a septic wound in the vicinity of a large blood\
vessel is to be taken seriously; it is usually necessary to _open up the\
wound_, clear out the clots and infected tissues with a sharp spoon,\
disinfect the walls of the cavity with eusol or hydrogen peroxide, and\
_pack_ it carefully but not too tightly with gauze impregnated with some\
antiseptic, such as "bipp," so that, if the bleeding does not recur, it\
may be left undisturbed for several days. The packing should if possible\
be brought into actual contact with the leaking point in the vessel, and\
so arranged as to make pressure on the artery above the erosion. The\
dressings and bandage are then applied, with the limb in the attitude\
that will diminish the force of the stream through the main artery, for\
example, flexion at the elbow in haemorrhage from the deep palmar arch.\
Other measures for combating the local sepsis, such as the irrigation\
method of Carrel, may be considered.\
\
If the wound involves one of the extremities, it may be useful; and it\
imparts confidence to the nurse, and, it may be, to the patient, if a\
Petit's tourniquet is loosely applied above the wound, which the nurse\
is instructed to tighten up in the event of bleeding taking place.\
\
_Ligation of the Artery._--If the haemorrhage recurs in spite of packing\
the wound, or if it is serious from the outset and likely to be critical\
if repeated, ligation of the artery itself or of the trunk from which it\
springs, at a selected spot higher up, should be considered. This is\
most often indicated in wounds of the extremities.\
\
As examples of proximal ligation for secondary haemorrhage may be cited\
ligation of the hypogastric artery for haemorrhage in the buttock, of the\
common iliac for haemorrhage in the thigh, of the brachial in the upper\
arm for haemorrhage from the deep palmar arch, and of the posterior\
tibial behind the medial malleolus for haemorrhage from the sole of the\
foot.\
\
_Amputation_ is the last resource, and should be decided upon if the\
haemorrhage recurs after proximal ligation, or if this has been followed\
by gangrene of the limb; it should also be considered if the nature of\
the wound and the virulence of the sepsis would of themselves justify\
removal of the limb. Every surgeon can recall cases in which a timely\
amputation has been the means of saving life.\
\
The _counteraction of the toxaemia_ and the _treatment of the bloodless\
state_, are carried out on the usual lines.\
\
#Haemorrhage of Toxic Origin.#--Mention must also be made of haemorrhages\
which depend upon infective or toxic conditions and in which no gross\
lesion of the vessels can be discovered. The bleeding occurs as an\
oozing, which may be comparatively slight and unimportant, or by its\
persistence may become serious. It takes place into the superficial\
layers of the skin, from mucous membranes, and into the substance of\
such organs as the pancreas. Haemorrhage from the stomach and intestine,\
attended with a brown or black discoloration of the vomit and of the\
stools, is one of the best known examples: it is not uncommonly met with\
in infective conditions originating in the appendix, intestine,\
gall-bladder, and other abdominal organs. Haemorrhage from the mucous\
membrane of the stomach after abdominal operations--apparently also due\
to toxic causes and not to the operation--gives rise to the so-called\
_post-operative haematemesis_.\
\
#Constitutional Effects of Haemorrhage.#--The severity of the symptoms\
resulting from haemorrhage depends as much on the rapidity with which the\
bleeding takes place as on the amount of blood lost. The sudden loss of\
a large quantity, whether from an open wound or into a serous\
cavity--for example, after rupture of the liver or spleen--is attended\
with marked pallor of the surface of the body and coldness of the skin,\
especially of the face, feet, and hands. The skin is moist with a cold,\
clammy sweat, and beads of perspiration stand out on the forehead. The\
pulse becomes feeble, soft, and rapid, and the patient is dull and\
listless, and complains of extreme thirst. The temperature is usually\
sub-normal; and the respiration rapid, shallow, and sighing in\
character. Abnormal visual sensations, in the form of flashes of light\
or spots before the eyes; and rushing, buzzing, or ringing sounds in the\
ears, are often complained of.\
\
In extreme cases, phenomena which have been aptly described as those of\
"air-hunger" ensue. On account of the small quantity of blood\
circulating through the body, and the diminished haemoglobin content of\
the blood, the tissues are imperfectly oxygenated, and the patient\
becomes extremely restless, gasping for breath, constantly throwing\
about his arms and baring his chest in the vain attempt to breath more\
freely. Faintness and giddiness are marked features. The diminished\
supply of oxygen to the brain and to the muscles produces muscular\
twitchings, and sometimes convulsions. Finally the pupils dilate, the\
sphincters relax, and death ensues.\
\
Young children stand the loss of blood badly, but they quickly recover,\
as the regeneration of blood takes place rapidly. In old people also,\
and especially when they are fat, the loss of blood is badly borne, and\
the ill effects last longer. Women, on the whole, stand loss of blood\
better than men, and in them the blood is more rapidly re-formed. A few\
hours after a severe haemorrhage there is usually a leucocytosis of from\
15,000 to 30,000.\
\
#Treatment of the Bloodless State.#--The patient should be placed in a\
warm, well-ventilated room, and the foot of the bed elevated. Cardiac\
stimulants, such as strychnin or alcohol, must be judiciously\
administered, over-stimulation being avoided. The inhalation of oxygen\
has been found useful in relieving the urgent symptoms of dyspnoea.\
\
The blood may be emptied from the limbs into the vessels of the trunk,\
where it is more needed, by holding them vertically in the air for a few\
minutes, and then applying a firm elastic bandage over a layer of cotton\
wool, from the periphery towards the trunk.\
\
_Introduction of Fluids into the Circulation._--The most valuable\
measure for maintaining the circulation, however, is by transfusion of\
blood (_Op. Surg._, p. 37). If this is not immediately available the\
introduction of from one to three pints of physiological salt\
solution (a teaspoonful of common salt to a pint of water) into a vein,\
or a 6 per cent. solution of gum acacia, is a useful expedient. The\
solution is sterilised by boiling, and cooled to a temperature of about\
105 o F. The addition of 5 to 10 minims of adrenalin solution (1 in 1000)\
is advantageous in raising the blood-pressure (_Op. Surg._, p. 565).\
\
When the intra-venous method is not available, one or two pints of\
saline solution with adrenalin should be slowly introduced into the\
rectum, by means of a long rubber tube and a filler. Satisfactory,\
although less rapidly obtained results follow the introduction of saline\
solution into the cellular tissue--for example, under the mamma, into\
the axilla, or under the skin of the back.\
\
If the patient can retain fluids taken by the mouth--such as hot coffee,\
barley water, or soda water--these should be freely given, unless the\
injury necessitates operative treatment under a general anaesthetic.\
\
Transfusion of blood is most valuable as _a preliminary to operation_ in\
patients who are bloodless as a result of haemorrhage from gastric and\
duodenal ulcers, and in bleeders.\
\
\
HAEMOPHILIA\
\
The term haemophilia is applied to an inherited disease which renders the\
patient liable to serious haemorrhage from even the most trivial\
injuries; and the subjects of it are popularly known as "bleeders."\
\
The cause of the disease and its true nature are as yet unknown. There\
is no proof of any structural defect in the blood vessels, and beyond\
the fact that there is a diminution in the number of blood-plates, it\
has not been demonstrated that there is any alteration in the\
composition of the blood.\
\
The affection is in a marked degree hereditary, all the branches of an\
affected family being liable to suffer. Its mode of transmission to\
individuals, moreover, is characteristic: the male members of the stock\
alone suffer from the affection in its typical form, while the tendency\
is transmitted through the female line. Thus the daughters of a father\
who is a bleeder, whilst they do not themselves suffer from the disease,\
transmit the tendency to their male offspring. The sons, on the other\
hand, neither suffer themselves nor transmit the disease to their\
children (Fig. 64). The female members of a haemophilic stock are often\
very prolific, and there is usually a predominance of daughters in their\
families.\
\
\
FIG 64.--Genealogical Tree of a Haemophilic Family.\
\
Great-Great-Grandmother                Great-Great-Grandfather\
Mrs D. (Lancashire) F                  M (History not known\
                   .|                  |  as to bleeding)\
                   .|                  |\
                   .+----------+-------+\
                   ............|\
                              .|\
                           ....|\
                           .+---------+--------+\
         Great-Grandmother .|         |        |\
           (Married three  .F        MB       MB\
                times)     .|\
                           .|\
                           .|\
      By First Husband     .|                  By Second           By Third\
              ..............|                  Husband             Husband\
   +-----------+------------+----------+-------+-------+-----------+------+\
   |          .|            |          |       +-------+-----------+------+\
   M          .F            F          F       |       |           +------+\
   |          .|            |          |       MB      F Died in      No\
Died       Grandmother      |          |               | Childbed    Family\
 aet.          .|            |     +-----------+   +----+---\
 70           .|        +------+  |had family |   |\
              .|        |      |  |but history|   |\
              .|        MB    MB  |not known  |   MB\
              .|\
              .|\
              .|.............................\
+-----+----------+------------+------------+------------+-------------+\
|     |          |            |            |.           |             |\
|     |          |            |            |.           |             |\
M     M          M            MB           F.           F             F\
      |                                    |.           |             |\
      |                                  Mother   +--+--+---+--+--+   |\
    +----+                                 |.     |  |  |   |  |  |   |\
    |    |                                 |.     M  M  MB  F  F  F   |\
    M    F                                 |.                         |\
     Not Married                           |.             +---+---+---+---+\
                                           |.             |   |   |   |   |\
                                           |.             MB  M   MB  M   M\
                              .............|.\
                         +-----+-----+-----+-----+-----+\
                         |    .|    .|     |     |     |\
                         |    .|*   .|*    |     |     |\
                         M    MB    MB     F     F     F\
\
\
F = Females.  M = Males (not bleeders).  MB = Males (bleeders)\
\
 ** the patients observed by the authors. The dotted line shows the\
    transmission of the disease to our patients through four\
    generations.\
\
\
The disease is met with in boys who are otherwise healthy, and usually\
manifests itself during the first few years of life. In rare instances\
profuse haemorrhage takes place when the umbilical cord separates. As a\
rule the first evidence is the occurrence of long-continued and\
uncontrollable bleeding from a comparatively slight injury, such as the\
scratch of a pin, the extraction of a tooth, or after the operation of\
circumcision. The blood oozes slowly from the capillaries; at first it\
appears normal, but after flowing for some days, or it may be weeks, it\
becomes pale, thin, and watery, and shows less and less tendency to\
coagulate.\
\
Female members of haemophilia families sometimes show a tendency to\
excessive haemorrhage, but they seldom manifest the characteristic\
features met with in the male members.\
\
Sometimes the haemorrhage takes place apparently spontaneously from the\
gums, the nasal or the intestinal mucous membrane. In other cases the\
bleeding occurs into the cellular tissue under the skin or mucous\
membrane, producing large areas of ecchymosis and discoloration. One of\
the commonest manifestations of the disease is the occurrence of\
haemorrhage into the cavities of the large joints, especially the knee,\
elbow, or hip. The patient suffers repeatedly from such haemorrhages, the\
determining injury being often so slight as to have passed unobserved.\
\
There is evidence that the tendency to bleed is greater at certain times\
than at others--in some cases showing almost a cyclical\
character--although nothing is known as to the cause of the variation.\
\
After a severe haemorrhage into the cellular tissue or into a joint, the\
patient becomes pale and anaemic, the temperature may rise to 102 o or\
103 o F., the pulse become small and rapid, and haemic murmurs are\
sometimes developed over the heart and large arteries. The swelling is\
tense, fluctuating, and hot, and there is considerable pain and\
tenderness.\
\
In exceptional cases, blisters form over the seat of the effusion, or\
the skin may even slough, and the clinical features may therefore come\
to simulate closely those of an acute suppurative condition. When the\
skin sloughs, an ulcer is formed with altered blood-clot in its floor\
like that seen in scurvy, and there is a remarkable absence of any\
attempt at healing.\
\
The acute symptoms gradually subside, and the blood is slowly absorbed,\
the discoloration of the skin passing through the same series of changes\
as occur after an ordinary bruise. The patients seldom manifest the\
symptoms of the bloodless state, and the blood is rapidly regenerated.\
\
The _diagnosis_ is easy if the patient or his friends are aware of the\
family tendency to haemorrhage and inform the doctor of it, but they are\
often sensitive and reticent regarding the fact, and it may only be\
elicited after close investigation. From the history it is usually easy\
to exclude scurvy and purpura. Repeated haemorrhages into a joint may\
result in appearances which closely simulate those of tuberculous\
disease. Recent haemorrhages into the cellular tissue often present\
clinical features closely resembling those of acute cellulitis or\
osteomyelitis. A careful examination, however, may reveal ecchymoses on\
other parts of the body which give a clue to the nature of the\
condition, and may prevent the disastrous consequences that may follow\
incision.\
\
These patients usually succumb sooner or later to haemorrhage, although\
they often survive several severe attacks. After middle life the\
tendency to bleed appears to diminish.\
\
_Treatment._--As a rule the ordinary means of arresting haemorrhage are\
of little avail. From among the numerous means suggested, the following\
may be mentioned: The application to the bleeding point of gauze soaked\
in a 1 in 1000 solution of adrenalin; prolonged inhalation of oxygen;\
freezing the part with a spray of ethyl-chloride; one or more\
subcutaneous injections of gelatin--5 ounces of a 2 1/2 per cent.\
solution of white gelatin in normal salt solution being injected at a\
temperature of about 100 o F.; the injection of pituitary extract. The\
application of a pad of gauze soaked in the blood of a normal person\
sometimes arrests the bleeding.\
\
To prevent bleeding in haemophilics, intra-venous or subcutaneous\
injections of fresh blood serum, taken from the human subject, the\
sheep, the dog, or the horse, have proved useful. If fresh serum is not\
available, anti-diphtheritic or anti-tetanic serum or trade\
preparations, such as hemoplastin, may be employed. We have removed the\
appendix and amputated through the thigh in haemophilic subjects without\
excessive loss of blood after a course of fresh sheep's serum given by\
the mouth over a period of several weeks.\
\
The chloride and lactate of calcium, and extract of thymus gland have\
been employed to increase the coagulability of the blood. The patient\
should drink large quantities of milk, which also increases the\
coagulability of the blood. Monro has observed remarkable results from\
the hypodermic injection of emetin hydrochloride in  1/2-grain doses.\
\
\
THROMBOSIS AND EMBOLISM\
\
The processes known as thrombosis and embolism are so intimately\
associated with the diseases of blood vessels that it is convenient to\
define these terms in the first instance.\
\
#Thrombosis.#--The term _thrombus_ is applied to a clot of blood formed\
in the interior of the heart or of a blood vessel, and the process by\
which such a clot forms is known as _thrombosis_. It would appear that\
slowing or stagnation of the blood-stream, and interference with the\
integrity of the lining membrane of the vessel wall, are the most\
important factors determining the formation of the clot. Alterations in\
the blood itself, such as occur, for example, in certain toxaemias, also\
favour coagulation. When the thrombus is formed slowly, it consists of\
white blood cells with a small proportion of fibrin, and, being\
deposited in successive layers, has a distinctly laminated appearance on\
section. It is known as a _white thrombus_ or laminated clot, and is\
often met with in the sac of an aneurysm (Fig. 72). When rapidly formed\
in a vessel in which the blood is almost stagnant--as, for example, in a\
pouched varicose vein--the blood coagulates _en masse_, and the clot\
consists of all the elements of the blood, constituting a _red thrombus_\
(Fig. 66). Sometimes the thrombus is _mixed_--a red thrombus being\
deposited on a white one, it may be in alternate layers.\
\
When aseptic, a thrombus may become detached and be carried off in the\
blood-stream as an embolus; it may become organised; or it may\
degenerate and undergo calcification. Occasionally a small thrombus\
situated behind a valve in a varicose vein or in the terminal end of a\
dilated vein--for example in a pile--undergoes calcification, and is\
then spoken of as a _phlebolith_; it gives a shadow with the X-rays.\
\
When infected with pyogenic bacteria, the thrombus becomes converted\
into pus and a localised abscess forms; or portions of the thrombus may\
be carried as emboli in the circulation to distant parts, where they\
give rise to secondary foci of suppuration--pyaemic abscesses.\
\
#Embolism.#--The term _embolus_ is applied to any body carried along in\
the circulation and ultimately becoming impacted in a blood vessel. This\
occurrence is known as _embolism_. The commonest forms of embolus are\
portions of thrombi or of fibrinous formations on the valves of the\
heart, the latter being usually infected with micro-organisms.\
\
Embolism plays an important part in determining one form of gangrene, as\
has already been described. Infective emboli are the direct cause of the\
secondary abscesses that occur in pyaemia; and they are sometimes\
responsible for the formation of aneurysm.\
\
Portions of malignant tumours also may form emboli, and their impaction\
in the vessels may lead to the development of secondary growths in\
distant parts of the body.\
\
Fat and air embolism have already been referred to.\
\
\
ARTERITIS\
\
_Pyogenic._--Non-suppurative inflammation of the coats of an artery may\
so soften the wall of the vessel as to lead to aneurysmal dilatation. It\
is not uncommon in children, and explains the occurrence of aneurysm in\
young subjects.\
\
When suppuration occurs, the vessel wall becomes disintegrated and gives\
way, leading to secondary haemorrhage. If the vessel ruptures into an\
abscess cavity, dangerous bleeding may occur when the abscess bursts or\
is opened.\
\
_Syphilitic._--The inflammation associated with syphilis results in\
thickening of the tunica intima, whereby the lumen of the vessel becomes\
narrowed, or even obliterated--_endarteritis obliterans_. The middle\
coat usually escapes, but the tunica externa is generally thickened.\
These changes cause serious interference with the nutrition of the parts\
supplied by the affected arteries. In large trunks, by diminishing the\
elasticity of the vessel wall, they are liable to lead to the formation\
of aneurysm.\
\
Changes in the arterial walls closely resembling those of syphilitic\
arteritis are sometimes met with in _tuberculous_ lesions.\
\
#Arterio-sclerosis# or #Chronic Arteritis#.--These terms are applied to\
certain changes which result in narrowing of the lumen and loss of\
elasticity in the arteries. The condition may affect the whole vascular\
system or may be confined to particular areas. In the smaller arteries\
there is more or less uniform thickening of the tunica intima from\
proliferation of the endothelium and increase in the connective tissue\
in the elastic lamina--a form of obliterative endarteritis. The\
narrowing of the vessels may be sufficient to determine gangrene in the\
extremities. In course of time, particularly in the larger arteries,\
this new tissue undergoes degeneration, at first of a fatty nature, but\
progressing in the direction of calcification, and this is followed by\
the deposit of lime salts in the young connective tissue and the\
formation of calcareous plates or rings over a considerable area of the\
vessel wall. To this stage in the process the term _atheroma_ is\
applied. The endothelium over these plates often disappears, leaving\
them exposed to the blood-stream.\
\
Changes of a similar kind sometimes occur in the middle coat, the lime\
salts being deposited among the muscle fibres in concentric rings.\
\
The primary cause of arterio-sclerosis is not definitely known, but its\
almost constant occurrence, to a greater or less degree, in the aged\
suggests that it is of the nature of a senile degeneration. It is\
favoured by anything which throws excessive strain on the vessel walls,\
such as heavy muscular work; by chronic alcoholism and syphilis; or by\
such general diseases as tend to raise the blood-pressure--for example,\
chronic Bright's disease or gout. It occurs with greater frequency and\
with greater severity in men than in women.\
\
Atheromatous degeneration is most common in the large arterial trunks,\
and the changes are most marked at the arch of the aorta, opposite the\
flexures of joints, at the mouths of large branches, and at parts where\
the vessel lies in contact with bone. The presence of diseased patches\
in the wall of an artery diminishes its elasticity and favours\
aneurysmal dilatation. Such a vessel also is liable to be ruptured by\
external violence and so give rise to traumatic aneurysm. Thrombosis is\
liable to occur when calcareous plates are exposed in the lumen of the\
vessel by destruction of the endothelium, and this predisposes to\
embolism. Arterio-sclerosis also interferes with the natural arrest of\
haemorrhage, and by rendering the vessels brittle, makes it difficult to\
secure them by ligature. In advanced cases the accessible arteries--such\
as the radial, the temporal or the femoral--may be felt as firm,\
tortuous cords, which are sometimes so hard that they have been aptly\
compared to "pipe-stems." The pulse is smaller and less compressible\
than normal, and the vessel moves bodily with each pulsation. It must be\
borne in mind, however, that the condition of the radial artery may fail\
to afford a clue to that of the larger arteries. Calcified arteries are\
readily identified in skiagrams (Fig. 65).\
\
[Illustration: FIG. 65.--Radiogram showing Calcareous Degeneration\
(Atheroma) of Arteries.]\
\
We have met with a chronic form of arterial degeneration in elderly\
women, affecting especially the great vessels at the root of the neck,\
in which the artery is remarkably attenuated and dilated, and so friable\
that the wall readily tears when seized with an artery-forceps,\
rendering ligation of the vessel in the ordinary way well-nigh\
impossible. Matas suggests infolding the wall of the vessel with\
interrupted sutures that do not pierce the intima, and wrapping it\
round with a strip of peritoneum or omentum.\
\
The most serious form of arterial _thrombosis_ is that met with _in the\
abdominal aorta_, which is attended with violent pains in the lower\
limbs, rapidly followed by paralysis and arrest of the circulation.\
\
\
THROMBO-PHLEBITIS AND THROMBOSIS IN VEINS\
\
#Thrombosis# is more common in veins than in arteries, because slowing\
of the blood-stream and irritation of the endothelium of the vessel wall\
are, owing to the conditions of the venous circulation, more readily\
induced in veins.\
\
Venous thrombosis may occur from purely mechanical causes--as, for\
example, when the wall of a vein is incised, or the vessel included in a\
ligature, or when it is bruised or crushed by a fragment of a broken\
bone or by a bandage too tightly applied. Under these conditions\
thrombosis is essentially a reparative process, and has already been\
considered in relation to the repair of blood vessels.\
\
In other cases thrombosis is associated with certain constitutional\
diseases--gout, for example; the endothelium of the veins undergoing\
changes--possibly the result of irritation by abnormal constituents in\
the blood--which favour the formation of thrombi.\
\
Under these various conditions the formation of a thrombus is not\
necessarily associated with the action of bacteria, although in any\
of them this additional factor may be present.\
\
The most common cause of venous thrombosis, however, is inflammation of\
the wall of the vein--phlebitis.\
\
#Phlebitis.#--Various forms of phlebitis are met with, but for practical\
purposes they may be divided into two groups--one in which there is a\
tendency to the formation of a thrombus; the other in which the\
infective element predominates.\
\
In surgical patients, the _thrombotic form_ is almost invariably met\
with in the lower extremity, and usually occurs in those who are\
debilitated and anaemic, and who are confined to bed for prolonged\
periods--for example, during the treatment of fractures of the leg or\
pelvis, or after such operations as herniotomy, prostatectomy, or\
appendectomy.\
\
_Clinical Features._--The most typical example of this form of phlebitis\
is that so frequently met with in the great saphena vein, especially\
when it is varicose. The onset of the attack is indicated by a sudden\
pain in the lower limb--sometimes below, sometimes above the knee. This\
initial pain may be associated with shivering or even with a rigor, and\
the temperature usually rises one or two degrees. There is swelling and\
tenderness along the line of the affected vein, and the skin over it is\
a dull-red or purple colour. The swollen vein may be felt as a firm\
cord, with bead-like enlargements in the position of the valves. The\
patient experiences a feeling of stiffness and tightness throughout the\
limb. There is often oedema of the leg and foot, especially when the limb\
is in the dependent position. The acute symptoms pass off in a few days,\
but the swelling and tenderness of the vein and the oedema of the limb\
may last for many weeks.\
\
When the deep veins--iliac, femoral, popliteal--are involved, there is\
great swelling of the whole limb, which is of a firm almost "wooden"\
consistence, and of a pale-white colour; the oedema may be so great that\
it is impossible to feel the affected vein until the swelling has\
subsided. This is most often seen in puerperal women, and is known as\
_phlegmasia alba dolens_.\
\
_Treatment._--The patient must be placed at absolute rest, with the foot\
of the bed raised on blocks 10 or 12 inches high, and the limb\
immobilised by sand-bags or splints. It is necessary to avoid handling\
the parts, lest the clot be displaced and embolism occur. To avoid\
frequent movement of the limb, the necessary dressings should be kept in\
position by means of a many-tailed rather than a roller bandage.\
\
To relieve the pain, warm fomentations or lead and opium lotion should\
be applied. Later, ichthyol-glycerin, or glycerin and belladonna, may be\
substituted.\
\
When, at the end of three weeks, the danger of embolism is past,\
douching and gentle massage may be employed to disperse the oedema; and\
when the patient gets up he should wear a supporting elastic bandage.\
\
The _infective_ form usually begins as a peri-phlebitis arising in\
connection with some focus of infection in the adjacent tissues. The\
elements of the vessel wall are destroyed by suppuration, and the\
thrombus in its lumen becomes infected with pyogenic bacteria and\
undergoes softening.\
\
_Occlusion of the inferior vena cava_ as a result of infective\
thrombosis is a well-known condition, the thrombosis extending into the\
main trunk from some of its tributaries, either from the femoral or\
iliac veins below or from the hepatic veins above.\
\
Portions of the softened thrombus are liable to become detached and to\
enter the circulating blood, in which they are carried as emboli. These\
may lodge in distant parts, and give rise to secondary foci of\
suppuration--pyaemic abscesses.\
\
_Clinical Features._--Infective phlebitis is most frequently met with in\
the transverse sinus as a sequel to chronic suppuration in the mastoid\
antrum and middle ear. It also occurs in relation to the peripheral\
veins, but in these it can seldom be recognised as a separate entity,\
being merged in the general infective process from which it takes\
origin. Its occurrence may be inferred, if in the course of a\
suppurative lesion there is a sudden rise of temperature, with pain,\
redness, and swelling along the line of a venous trunk, and a rapidly\
developed oedema of the limb, with pitting of the skin on pressure. In\
rare cases a localised abscess forms in the vein and points towards the\
surface.\
\
_Treatment._--Attention must be directed towards the condition with\
which the phlebitis is associated. Ligation of the vein on the cardiac\
side of the thrombus with a view to preventing embolism is seldom\
feasible in the peripheral veins, although, as will be pointed out\
later, the jugular vein is ligated with this object in cases of\
phlebitis of the transverse sinus.\
\
\
VARIX--VARICOSE VEINS\
\
The term varix is applied to a condition in which veins are so altered\
in structure that they remain permanently dilated, and are at the same\
time lengthened and tortuous. Two types are met with: one in which\
dilatation of a large superficial vein and its tributaries is the most\
obvious feature; the other, in which bunches of distended and tortuous\
vessels develop at one or more points in the course of a vein, a\
condition to which Virchow applied the term _angioma racemosum venosum_.\
The two types may occur in combination.\
\
Any vein in the body may become varicose, but the condition is rare\
except in the veins of the lower extremity, in the veins of the\
spermatic cord (varicocele), and in the veins of the anal canal\
(haemorrhoids).\
\
We are here concerned with varix as it occurs in the veins of the lower\
extremity.\
\
_Etiology._--Considerable difference of opinion exists as to the\
essential cause of varix. The weight of evidence is in favour of the\
view that, when dilatation is the predominant element, it results from a\
congenital deficiency in the number, size, and strength of the valves of\
the affected veins, and in an inherent weakness in the vessel walls.\
The _angioma racemosum venosum_ is probably also due to a congenital\
alteration in the structure of the vessels, and is allied to tumours of\
blood vessels. The view that varix is congenital in origin, as was first\
suggested by Virchow, is supported by the fact that in a large\
proportion of cases the condition is hereditary; not only may several\
members of the same family in succeeding generations suffer from varix,\
but it is often found that the same vein, or segment of a vein, is\
involved in all of them. The frequent occurrence of varix in youth is\
also an indication of its congenital origin.\
\
In the majority of cases it is only when some exciting factor comes into\
operation that the clinical phenomena associated with varix appear. The\
most common exciting cause is increased pressure within the veins, and\
this may be produced in a variety of ways. In certain diseases of the\
heart, lungs, and liver, for example, the venous pressure may be so\
raised as to cause a localised dilatation of such veins as are\
congenitally weak. The direct pressure of a tumour, or of the gravid\
uterus on the large venous trunks in the pelvis, may so obstruct the\
flow as to distend the veins of the lower extremity. It is a common\
experience in women that the signs of varix date from an antecedent\
pregnancy. The importance of the wearing of tight garters as a factor in\
the production of varicose veins has been exaggerated, although it must\
be admitted that this practice is calculated to aggravate the condition\
when it is once established. It has been proved experimentally that the\
backward pressure in the veins may be greatly increased by straining, a\
fact which helps to explain the frequency with which varicosity occurs\
in the lower limbs of athletes and of those whose occupation involves\
repeated and violent muscular efforts. There is reason to believe,\
moreover, that a sudden strain may, by rupturing the valves and so\
rendering them incompetent, induce varicosity independently of any\
congenital defect. Prolonged standing or walking, by allowing gravity to\
act on the column of blood in the veins of the lower limbs, is also an\
important determining factor in the production of varix.\
\
Thrombosis of the deep veins--in the leg, for example--may induce marked\
dilatation of the superficial veins, by throwing an increased amount of\
work upon them. This is to be looked upon rather as a compensatory\
hypertrophy of the superficial vessels than as a true varix.\
\
_Morbid Anatomy._--In the lower extremity the varicosity most commonly\
affects the vessels of the great saphena system; less frequently those\
of the small saphena system. Sometimes both systems are involved, and\
large communicating branches may develop between the two.\
\
The essential lesion is the absence or deficiency of valves, so that\
they are incompetent and fail to support the column of blood which bears\
back upon them. Normally the valves in the femoral and iliac veins and\
in the inferior vena cava are imperfectly developed, so that in the\
erect posture the great saphena receives a large share of the backward\
pressure of the column of venous blood.\
\
The whole length of the vein may be affected, but as a rule the disease\
is confined to one or more segments, which are not only dilated, but are\
also increased in length, so that they become convoluted. The adjacent\
loops of the convoluted vein are often bound together by fibrous tissue.\
All the coats are thickened, chiefly by an increased development of\
connective tissue, and in some cases changes similar to those of\
arterio-sclerosis occur. The walls of varicose veins are often\
exceedingly brittle. In some cases the thickening is uniform, and in\
others it is irregular, so that here and there thin-walled sacs or\
pouches project from the side of the vein. These pouches vary in size\
from a bean to a hen's egg, the larger forms being called _venous\
cysts_, and being most commonly met with in the region of the saphenous\
opening and of the opening in the popliteal fascia. Such pouches, being\
exposed to injury, are frequently the seat of thrombosis (Fig. 66).\
\
[Illustration: FIG. 66.--Thrombosis in Tortuous and Pouched Great\
Saphena Vein, in longitudinal section.]\
\
_Clinical Features._--Varix is most frequently met with between puberty\
and the age of thirty, and the sexes appear to suffer about equally.\
\
The amount of discomfort bears no direct proportion to the extent of\
the varicosity. It depends rather upon the degree of pressure in the\
veins, as is shown by the fact that it is relieved by elevation of the\
limb. When the whole length of the main trunk of the great saphena is\
implicated, the pressure in the vein is high and the patient suffers a\
good deal of pain and discomfort. When, on the contrary, the upper part\
of the saphena and its valves are intact, and only the more distal veins\
are involved, the pressure is not so high and there is comparatively\
little suffering. The usual complaint is of a sense of weight and\
fulness in the limb after standing or walking, sometimes accompanied by\
actual pain, from which relief is at once obtained by raising the limb.\
Cramp-like pains in the muscles are often associated with varix of the\
deep veins.\
\
The dilated and tortuous vein can be readily seen and felt when the\
patient is examined in the upright posture. In advanced cases, bead-like\
swellings are sometimes to be detected over the position of the valves,\
and, on running the fingers along the course of the vessel, a firm\
ridge, due to periphlebitis, may be detected on each side of the vein.\
When the limb is oedematous, the outline of the veins is obscured, but\
they can be identified on palpation as gutter-like tracks. When large\
veins are implicated, a distinct impulse on coughing may be seen to pass\
down as far as the knee; and if the vessel is sharply percussed a fluid\
wave may be detected passing both up and down the vein.\
\
If the patient is placed on a couch and the limb elevated, the veins are\
emptied, and if pressure is then made over the region of the saphenous\
opening and the patient allowed to stand up, so long as the great\
saphena system alone is involved, the veins fill again very slowly from\
below. If the small saphena system also is involved, and if\
communicating branches are dilated, the veins fill up from below more\
rapidly. When the pressure over the saphenous opening is removed, the\
blood rapidly rushes into the varicose vessels from above; this is known\
as Trendelenburg's test.\
\
The most marked dilatation usually occurs on the medial side of the\
limb, between the middle of the thigh and the middle of the calf, the\
arrangement of the veins showing great variety (Fig. 67).\
\
There are usually one or more bunches of enlarged and tortuous veins in\
the region of the knee. Frequently a large branch establishes a\
communication between the systems of the great and small saphenous veins\
in the region of the popliteal space, or across the front of the upper\
part of the tibia. The superficial position of this last branch and its\
proximity to the bone render it liable to injury.\
\
[Illustration: FIG. 67.--Extensive Varix of Internal Saphena System on\
Left Leg, of many years' standing.]\
\
The small veins of the skin of the ankle and foot often show as fine\
blue streaks arranged in a stellate or arborescent manner, especially in\
women who have borne children.\
\
_Complications._--When the varix is of long standing, the skin in the\
lower part of the leg sometimes assumes a mahogany-brown or bluish hue,\
as a result of the _deposit of blood pigment_ in the tissues, and this\
is frequently a precursor of ulceration.\
\
_Chronic dermatitis_ (_varicose eczema_) is often met with in the lower\
part of the leg, and is due to interference with the nutrition of the\
skin. The incompetence of the valves allows the pressure in the varicose\
veins to equal that in the arterioles, so that the capillary circulation\
is impeded. From the same cause the blood in the deep veins is enabled\
to enter the superficial veins, where the backward pressure is so great\
that the blood flows down again, and so a vicious circle is established.\
The blood therefore loses more and more of its oxygen, and so fails to\
nourish the tissues.\
\
The _ulcer_ of the leg associated with varicose veins has already been\
described.\
\
_Haemorrhage_ may take place from a varicose vein as a result of a wound\
or of ulceration of its wall. Increased intra-venous pressure produced\
by severe muscular strain may determine rupture of a vein exposed in the\
floor of an ulcer. If the limb is dependent, the incompetency of the\
valves permits of rapid and copious bleeding, which may prove fatal,\
particularly if the patient is intoxicated when the rupture takes place\
and no means are taken to arrest the haemorrhage. The bleeding may be\
arrested at once by elevating the limb, or by applying pressure directly\
over the bleeding point.\
\
_Phlebitis and thrombosis_ are common sequelae of varix, and may prove\
dangerous, either by spreading into the large venous trunks or by giving\
rise to emboli. The larger the varix the greater is the tendency for a\
thrombus to spread upwards and to involve the deep veins. Thrombi\
usually originate in venous cysts or pouches, and at acute bends on the\
vessel, especially when these are situated in the vicinity of the knee,\
and are subjected to repeated injuries--for example in riding.\
Phleboliths sometimes form in such pouches, and may be recognised in a\
radiogram. In a certain proportion of cases, especially in elderly\
people, the occurrence of thrombosis leads to cure of the condition by\
the thrombus becoming organised and obliterating the vein.\
\
_Treatment._--At best the treatment of varicose veins is only\
palliative, as it is obviously impossible to restore to the vessels\
their normal structure. The patient must avoid wearing anything, such as\
a garter, which constricts the limb, and any obvious cause of direct\
pressure on the pelvic veins, such as a tumour, persistent\
constipation, or an ill-fitting truss, should be removed. Cardiac,\
renal, or pulmonary causes of venous congestion must also be treated,\
and the functions of the liver regulated. Severe forms of muscular\
exertion and prolonged standing or walking are to be avoided, and the\
patient may with benefit rest the limb in an elevated position for a few\
hours each day. To support the distended vessels, a closely woven silk\
or worsted stocking, or a light and porous form of elastic bandage,\
applied as a puttee, should be worn. These appliances should be put on\
before the patient leaves his bed in the morning, and should only be\
removed after he lies down at night. In this way the vessels are never\
allowed to become dilated. Elastic stockings, and bandages made entirely\
of india-rubber, are to be avoided. In early and mild cases these\
measures are usually sufficient to relieve the patient's discomfort.\
\
_Operative Treatment._--In aggravated cases, when the patient is\
suffering pain, when his occupation is interfered with by repeated\
attacks of phlebitis, or when there are large pouches on the veins,\
operative treatment is called for. The younger the patient the clearer\
is the indication to operate. It may be necessary to operate to enable a\
patient to enter one of the public services, even although no symptoms\
are present. The presence of an ulcer does not contra-indicate\
operation; the ulcer should be excised, and the raw surface covered with\
skin grafts, before dealing with the veins.\
\
The _operation of Trendelenburg_ is especially appropriate to cases in\
which the trunk of the great saphena vein in the thigh is alone\
involved. It consists in exposing three or four inches of the vein in\
its upper part, applying a ligature at the upper and lower ends of the\
exposed portion, and, after tying all tributary branches, resecting this\
portion of the vein.\
\
The procedure of C. H. Mayo is adapted to cases in which it is desirable\
to remove longer segments of the veins. It consists in the employment of\
special instruments known as "ring-enucleators" or "vein-strippers," by\
means of which long portions of the vein are removed through\
comparatively small incisions.\
\
An alternative procedure consists in avulsing segments of the vein by\
means of Babcock's stylet, which consists of a flexible steel rod, 30\
inches in length, with acorn-shaped terminals. The instrument is passed\
along the lumen of the segment to be dealt with, and a ligature applied\
around the vein above the bulbous end of the stylet enables nearly the\
whole length of the great saphena vein to be dragged out in one piece.\
These methods are not suitable when the veins are brittle, when there\
are pouches or calcareous deposits in their walls, or where there has\
been periphlebitis binding the coils together.\
\
Mitchell of Belfast advises exposing the varices at numerous points by\
half-inch incisions, and, after clamping the vein between two pairs of\
forceps, cutting it across and twisting out the segments of the vein\
between adjacent incisions. The edges of the incisions are sutured; and\
the limb is firmly bandaged from below upwards, and kept in an elevated\
position. We have employed this method with satisfactory results.\
\
The treatment of the complications of varix has already been considered.\
\
\
ANGIOMA[4]\
\
[4] In the description of angiomas we have followed the teaching of the\
late John Duncan.\
\
Tumours of blood vessels may be divided, according to the nature of the\
vessels of which they are composed, into the capillary, the venous, and\
the arterial angiomas.\
\
\
CAPILLARY ANGIOMA\
\
The most common form of capillary angioma is the naevus or congenital\
telangiectasis.\
\
#Naevus.#--A naevus is a collection of dilated capillaries, the afferent\
arterioles and the efferent venules of which often share in the\
dilatation. Little is known regarding the _etiology_ of naevi beyond the\
fact that they are of congenital origin. They often escape notice until\
the child is some days old, but attention is usually drawn to them\
within a fortnight of birth. For practical purposes the most useful\
classification of naevi is into the cutaneous, the subcutaneous, and the\
mixed forms.\
\
_The cutaneous naevus_, "mother's mark," or "port-wine stain," consists\
of an aggregation of dilated capillaries in the substance of the skin.\
On stretching the skin the vessels can be seen to form a fine network,\
or to run in leashes parallel to one another. A dilated arteriole or a\
vein winding about among the capillaries may sometimes be detected.\
These naevi occur on any part of the body, but they are most frequently\
met with on the face. They may be multiple, and vary greatly in size,\
some being no bigger than a pin-head, while others cover large areas of\
the body. In colour they present every tint from purple to brilliant\
red; in the majority there is a considerable dash of blue, especially in\
cold weather.\
\
Unlike the other forms of naevi, the cutaneous variety shows little\
tendency to disappear, and it is especially persistent when associated\
with overgrowth of the epidermis and of the hairs--_naevoid mole_.\
\
The _treatment_ of the cutaneous naevus is unsatisfactory, owing to the\
difficulty of removing the naevus without leaving a scar which is even\
more disfiguring. Very small naevi may be destroyed by a fine pointed\
Paquelin thermo-cautery, or by escharotics, such as nitric acid. For\
larger naevi, radium and solidified carbon dioxide ("CO_2 snow") may be\
used. The extensive port-wine stains so often met with on the face are\
best left alone.\
\
The _subcutaneous naevus_ is comparatively rare. It constitutes a\
well-defined, localised tumour, which may possess a distinct capsule,\
especially when it has ceased to grow or is retrogressing. On section,\
it presents the appearance of a finely reticulated sponge.\
\
Although it may be noticed at, or within a few days of, birth, a\
subcutaneous naevus is often overlooked, especially when on a covered\
part of the body, and may not be discovered till the patient is some\
years old. It forms a rounded, lobulated swelling, seldom of large size\
and yielding a sensation like that of a sponge; the skin over it is\
normal, or may exhibit a bluish tinge, especially in cold weather. In\
some cases the tumour is diminished by pressing the blood out of it, but\
slowly fills again when the pressure is relaxed, and it swells up when\
the child struggles or cries. From a cold abscess it is diagnosed by the\
history and progress of the swelling and by the absence of fluctuation.\
When situated over one of the hernial openings, it closely simulates a\
hernia; and when it occurs in the middle line of the face, head, or\
back, it may be mistaken for such other congenital conditions as\
meningocele or spina bifida. When other means fail, the use of an\
exploring needle clears up the diagnosis.\
\
_Mixed Naevus._--As its name indicates, the mixed naevus partakes of the\
characters of the other two varieties; that is, it is a subcutaneous\
naevus with involvement of the skin.\
\
It is frequently met with on the face and head, but may occur on any\
part of the body. It also affects parts covered by mucous membrane, such\
as the cheek, tongue, and soft palate. The swelling is rounded or\
lobulated, and projects beyond the level of its surroundings. Sometimes\
the skin is invaded by the naevoid tissue over the whole extent of the\
tumour, sometimes only over a limited area. Frequently the margin only\
is of a bright-red colour, while the skin in the centre resembles a\
cicatrix. The swelling is reduced by steady pressure, and increases in\
size and becomes tense when the child cries.\
\
[Illustration: FIG. 68.--Mixed Naevus of Nose which was subsequently\
cured by Electrolysis.]\
\
_Prognosis._--The rate of growth of the subcutaneous and mixed forms of\
naevi varies greatly. They sometimes increase rapidly, especially during\
the first few months of life; after this they usually grow at the same\
rate as the child, or more slowly. There is a decided tendency to\
disappearance of these varieties, fully 50 per cent. undergoing natural\
cure by a process of obliteration, similar to the obliteration of\
vessels in cicatricial tissue. This usually begins about the period of\
the first dentition, sometimes at the second dentition, and sometimes at\
puberty. On the other hand, an increased activity of growth may be shown\
at these periods. The onset of natural cure is recognised by the tumour\
becoming firmer and less compressible, and, in the mixed variety, by the\
colour becoming less bright. Injury, infection, or ulceration of the\
overlying skin may initiate the curative process.\
\
Towards adult life the spaces in a subcutaneous naevus may become greatly\
enlarged, leading to the formation of a cavernous angioma.\
\
_Treatment._--In view of the frequency with which subcutaneous and mixed\
naevi disappear spontaneously, interference is only called for when the\
growth of the tumour is out of proportion to that of the child, or when,\
from its situation--for example in the vicinity of the eye--any marked\
increase in its size would render it less amenable to treatment.\
\
The methods of treatment most generally applicable are the use of radium\
and carbon dioxide snow, igni-puncture, electrolysis, and excision.\
\
For naevi situated on exposed parts, where it is desirable to avoid a\
scar, the use of _radium_ is to be preferred. The tube of radium is\
applied at intervals to different parts of the naevus, the duration and\
frequency of the applications varying with the strength of the\
emanations and the reaction produced. The object aimed at is to induce\
obliteration of the naevoid tissue by cicatricial contraction without\
destroying the overlying skin. _Carbon-dioxide snow_ may be employed in\
the same manner, but the results are inferior to those obtained by\
radium.\
\
_Igni-puncture_ consists in making a number of punctures at different\
parts of the naevus with a fine-pointed thermo-cautery, with the object\
of starting at each point a process of cicatrisation which extends\
throughout the naevoid tissue and so obliterates the vessels.\
\
_Electrolysis_ acts by decomposing the blood and tissues into their\
constituent elements--oxygen and acids appearing at the positive,\
hydrogen and bases at the negative electrode. These substances and gases\
being given off in a nascent condition, at once enter into new\
combinations with anything in the vicinity with which they have a\
chemical affinity. In the naevus the practical result of this reaction is\
that at the positive pole nitric acid, and at the negative pole caustic\
potash, both in a state of minute subdivision, make their appearance.\
The effect on the tissues around the positive pole, therefore, is\
equivalent to that of an acid cauterisation, and on those round the\
negative pole, to an alkaline cauterisation.\
\
As the process is painful, a general anaesthetic is necessary. The\
current used should be from 20 to 80 milliamperes, gradually increasing\
from zero, without shock; three to six large Bunsen cells give a\
sufficient current, and no galvanometer is required. Steel needles,\
insulated with vulcanite to within an eighth of an inch of their points,\
are the best. Both poles are introduced into the naevus, the positive\
being kept fixed at one spot, while the negative is moved about so as to\
produce a number of different tracks of cauterisation. On no account\
must either pole be allowed to come in contact with the skin, lest a\
slough be formed. The duration of the sitting is determined by the\
effect produced, as indicated by the hardening of the tumour, the\
average duration being from fifteen to twenty minutes. If pallor of the\
skin appears, it indicates that the needles are too near the surface, or\
that the blood supply to the integument is being cut off, and is an\
indication to stop. To cauterise the track and so prevent bleeding, the\
needles should be slowly withdrawn while the current is flowing. When\
the skin is reached the current is turned off. The punctures are covered\
with collodion. Six or eight weeks should be allowed to elapse before\
repeating the procedure. From two to eight or ten sittings may be\
necessary, according to the size and character of the naevus.\
\
_Excision_ is to be preferred for naevi of moderate size situated on\
covered parts of the body, where a scar is of no importance. Its chief\
advantages over electrolysis are that a single operation is sufficient,\
and that the cure is speedy and certain. The operation is attended with\
much less haemorrhage than might be expected.\
\
#Cavernous Angioma.#--This form of angioma consists of a series of large\
blood spaces which are usually derived from the dilatation of the\
capillaries of a subcutaneous naevus. The spaces come to communicate\
freely with one another by the disappearance of adjacent capillary\
walls. While the most common situation is in the subcutaneous tissue, a\
cavernous angioma is sometimes met with in internal organs. It may\
appear at any age from early youth to middle life, and is of slow growth\
and may become stationary. The swelling is rounded or oval, there is no\
pulsation or bruit, and the tumour is but slightly compressible. The\
treatment consists in dissecting it out.\
\
#Aneurysm by Anastomosis# is the name applied to a vascular tumour in\
which the arteries, veins, and capillaries are all involved. It is met\
with chiefly on the upper part of the trunk, the neck, and the scalp. It\
tends gradually to increase in size, and may, after many years, attain\
an enormous size. The tumour is ill-defined, and varies in consistence.\
It is pulsatile, and a systolic bruit or a "thrilling" murmur may be\
heard over it. The chief risk is haemorrhage from injury or ulceration.\
\
[Illustration: FIG. 69.--Cirsoid Aneurysm of Forehead in a boy aet. 10.\
\
(Mr. J. W. Dowden's case.)]\
\
The _treatment_ is conducted on the same lines as for naevus. When\
electrolysis is employed, it should be directed towards the afferent\
vessels; and if it fails to arrest the flow through these, it is useless\
to persist with it. In some cases ligation of the afferent vessels has\
been successful.\
\
#Arterial Angioma# or #Cirsoid Aneurysm#.--This is composed of the\
enlarged branches of an arterial trunk. It originates in the smaller\
branches of an artery--usually the temporal--and may spread to the main\
trunk, and may even involve branches of other trunks with which the\
affected artery anastomoses.\
\
The condition is probably congenital in origin, though its appearance is\
frequently preceded by an injury. It almost invariably occurs in the\
scalp, and is usually met with in adolescent young adults.\
\
The affected vessels slowly increase in size, and become tortuous, with\
narrowings and dilatations here and there. Grooves and gutters are\
frequently found in the bone underlying the dilated vessels.\
\
There is a constant loud bruit in the tumour, which greatly troubles the\
patient and may interfere with sleep. There is no tendency either to\
natural cure or to rupture, but severe and even fatal haemorrhage may\
follow a wound of the dilated vessels.\
\
[Illustration: FIG. 70.--Cirsoid Aneurysm of Orbit and Face, which\
developed after a blow on the Orbit with a cricket ball.\
\
(From a photograph lent by Sir Montagu Cotterill.)]\
\
The condition may be treated by excision or by electrolysis. In excision\
the haemorrhage is controlled by an elastic tourniquet applied\
horizontally round the head, or by ligation of the feeding trunks. In\
large tumours the bleeding is formidable. In many cases electrolysis is\
to be preferred, and is performed in the same way as for naevus. The\
positive pole is placed in the centre of the tumour, while the negative\
is introduced into the main affluents one after another.\
\
\
ANEURYSM\
\
An aneurysm is a sac communicating with an artery, and containing fluid\
or coagulated blood.\
\
Two types are met with--the pathological and the traumatic. It is\
convenient to describe in this section also certain conditions in which\
there is an abnormal communication between an artery and a\
vein--arterio-venous aneurysm.\
\
\
PATHOLOGICAL ANEURYSM\
\
In this class are included such dilatations as result from weakening of\
the arterial coats, combined, in most cases, with a loss of elasticity\
in the walls and increase in the arterial tension due to\
arterio-sclerosis. In some cases the vessel wall is softened by\
arteritis--especially the embolic form--so that it yields before the\
pressure of the blood.\
\
Repeated and sudden raising of the arterial tension, as a result, for\
example, of violent muscular efforts or of excessive indulgence in\
alcohol, plays an important part in the causation of aneurysm. These\
factors probably explain the comparative frequency of aneurysm in those\
who follow such arduous occupations as soldiers, sailors,\
dock-labourers, and navvies. In these classes the condition usually\
manifests itself between the ages of thirty and fifty--that is, when the\
vessels are beginning to degenerate, although the heart is still\
vigorous and the men are hard at work. The comparative immunity of women\
may also be explained by the less severe muscular strain involved by\
their occupations and recreations.\
\
Syphilis plays an important part in the production of aneurysm, probably\
by predisposing the patient to arterio-sclerosis and atheroma, and\
inducing an increase in the vascular tension in the peripheral vessels,\
from loss of elasticity of the vessel wall and narrowing of the lumen as\
a result of syphilitic arteritis. It is a striking fact that aneurysm is\
seldom met with in women who have not suffered from syphilis.\
\
#Varieties--Fusiform Aneurysm.#--When the _whole circumference_ of an\
artery has been weakened, the tension of the blood causes the walls to\
dilate uniformly, so that a fusiform or tubular aneurysm results. All\
the coats of the vessel are stretched and form the sac of the aneurysm,\
and the affected portion is not only dilated but is also increased in\
length. This form is chiefly met with in the arch of the aorta, but may\
occur in any of the main arterial trunks. As the sac of the aneurysm\
includes all three coats, and as the inner and outer coats are usually\
thickened by the deposit in them of connective tissue, this variety\
increases in size slowly and seldom gives rise to urgent symptoms.\
\
As a rule a fusiform aneurysm contains fluid blood, but when the intima\
is roughened by disease, especially in the form of calcareous plates,\
shreds of clot may adhere to it.\
\
It has little tendency to natural cure, although this is occasionally\
effected by the emerging artery becoming occluded by a clot; it has also\
little tendency to rupture.\
\
#Sacculated Aneurysm.#--When a _limited area_ of the vessel wall is\
weakened--for example by atheroma or by other form of arteritis--this\
portion yields before the pressure of the blood, and a sacculated\
aneurysm results. The internal and middle coats being already damaged,\
or, it may be, destroyed, by the primary disease, the stress falls on\
the external coat, which in the majority of cases constitutes the sac.\
To withstand the pressure the external coat becomes thickened, and as\
the aneurysm increases in size it forms adhesions to surrounding\
tissues, so that fasciae, tendons, nerves, and other structures may be\
found matted together in its wall. The wall is further strengthened by\
the deposit on its inner aspect of blood-clot, which may eventually\
become organised.\
\
The contents of the sac consist of fluid blood and a varying amount of\
clot which is deposited in concentric layers on the inner aspect of the\
sac, where it forms a pale, striated, firm mass, which constitutes a\
laminated clot. Near the blood-current the clot is soft, red, and\
friable (Fig. 72). The laminated clot not only strengthens the sac,\
enabling it to resist the blood-pressure and so prevent rupture, but, if\
it increases sufficiently to fill the cavity, may bring about cure. The\
principle upon which all methods of treatment are based is to imitate\
nature in producing such a clot.\
\
Sacculated aneurysm, as compared with the fusiform variety, tends to\
rupture and also to cure by the formation of laminated clot; natural\
cure is sometimes all but complete when extension and rupture occur and\
cause death.\
\
An aneurysm is said to be _diffused_ when the sac ruptures and the blood\
escapes into the cellular tissue.\
\
#Clinical Features of Aneurysm.#--Surgically, the sacculated is by far\
the most important variety. The outstanding feature is the existence in\
the line of an artery of a globular swelling, which pulsates. The\
pulsation is of an expansile character, which is detected by observing\
that when both hands are placed over the swelling they are separated\
with each beat of the heart. If the main artery be compressed on the\
cardiac side of the swelling, the pulsation is arrested and the tumour\
becomes smaller and less tense, and it may be still further reduced in\
size by gentle pressure being made over it so as to empty it of fluid\
blood. On allowing the blood again to flow through the artery, the\
pulsation returns at once, but several beats are required before the sac\
regains its former size. In most cases a distinct thrill is felt on\
placing the hand over the swelling, and a blowing, systolic murmur may\
be heard with the stethoscope. It is to be borne in mind that\
occasionally, when the interchange of blood between an aneurysm and the\
artery from which it arises is small, pulsation and bruit may be slight\
or even absent. This is also the case when the sac contains a\
considerable quantity of clot. When it becomes filled with\
clot--_consolidated aneurysm_--these signs disappear, and the clinical\
features are those of a solid tumour lying in contact with an artery,\
and transmitting its pulsation.\
\
A comparison of the pulse in the artery beyond the seat of the aneurysm\
with that in the corresponding artery on the healthy side, shows that on\
the affected side the wave is smaller in volume, and delayed in time. A\
pulse tracing shows that the normal impulse and dicrotic waves are lost,\
and that the force and rapidity of the tidal wave are diminished.\
\
[Illustration: FIG. 71.--Radiogram of Aneurysm of Aorta, showing\
laminated clot and erosion of bodies of vertebrae. The intervertebral\
discs are intact.]\
\
An aneurysm exerts pressure on the surrounding structures, which are\
usually thickened and adherent to it and to one another. Adjacent veins\
may be so compressed that congestion and oedema of the parts beyond are\
produced. Pain, disturbances of sensation, and muscular paralyses may\
result from pressure on nerves. Such bones as the sternum and vertebrae\
undergo erosion and are absorbed by the gradually increasing pressure of\
the aneurysm. Cartilage, on the other hand, being elastic, yields before\
the pressure, so that the intervertebral discs or the costal cartilages\
may escape while the adjacent bones are destroyed (Fig. 71). The skin\
over the tumour becomes thinned and stretched, until finally a slough\
forms, and when it separates haemorrhage takes place.\
\
[Illustration: FIG. 72.--Sacculated Aneurysm of Abdominal Aorta nearly\
filled with laminated clot. Note greater density of clot towards\
periphery.]\
\
In the progress of an aneurysm towards rupture, timely clotting may\
avert death for the moment, but while extension in one direction has\
been arrested there is apt to be extension in another, with imminence of\
rupture, or it may be again postponed.\
\
#Differential Diagnosis.#--The diagnosis is to be made from other\
pulsatile swellings. Pulsation is sometimes transmitted from a large\
artery to a tumour, a mass of enlarged lymph glands, or an inflammatory\
swelling which lies in its vicinity, but the pulsation is not\
expansile--a most important point in differential diagnosis. Such\
swellings may, by appropriate manipulation, be moved from the artery and\
the pulsation ceases, and compression of the artery on the cardiac side\
of the swelling, although it arrests the pulsation, does not produce any\
diminution in the size or tension of the swelling, and when the pressure\
is removed the pulsation is restored immediately.\
\
Fluid swellings overlying an artery, such as cysts, abscesses, or\
enlarged bursae, may closely simulate aneurysm. An apparent expansion may\
accompany the pulsation, but careful examination usually enables this to\
be distinguished from the true expansion of an aneurysm. Compression of\
the artery makes no difference in the size or tension of the swelling.\
\
Vascular tumours, such as sarcoma and goitre, may yield an expansile\
pulsation and a soft, whifling bruit, but they differ from an aneurysm\
in that they are not diminished in size by compression of the main\
artery, nor can they be emptied by pressure.\
\
The exaggerated pulsation sometimes observed in the abdominal aorta, the\
"pulsating aorta" seen in women, should not be mistaken for aneurysm.\
\
#Prognosis.#--When _natural cure_ occurs it is usually brought about by\
the formation of laminated clot, which gradually increases in amount\
till it fills the sac. Sometimes a portion of the clot in the sac is\
separated and becomes impacted as an embolus in the artery beyond,\
leading to thrombosis which first occludes the artery and then extends\
into the sac.\
\
The progress of natural cure is indicated by the aneurysm becoming\
smaller, firmer, less expansile, and less compressible; the murmur and\
thrill diminish and the pressure effects become less marked. When the\
cure is complete the expansile pulsation is lost, and there remains a\
firm swelling attached to the vessel (_consolidated aneurysm_). While\
these changes are taking place the collateral arteries become enlarged,\
and an anastomotic circulation is established.\
\
An aneurysm may prove _fatal_ by exerting pressure on important\
structures, by causing syncope, by rupture, or from the occurrence of\
suppuration. _Pressure_ symptoms are usually most serious from aneurysms\
situated in the neck, thorax, or skull. Sudden fatal _syncope_ is not\
infrequent in cases of aneurysm of the thoracic aorta.\
\
_Rupture_ may take place through the skin, on a mucous or serous\
surface, or into the cellular tissue. The first haemorrhage is often\
slight and stops naturally, but it soon recurs, and is so profuse,\
especially when the blood escapes externally, that it rapidly proves\
fatal. When the bleeding takes place into the cellular tissue, the\
aneurysm is said to become _diffused_, and the extravasated blood\
spreads widely through the tissues, exerting great pressure on the\
surrounding structures.\
\
The _clinical features_ associated with rupture are sudden and severe\
pain in the part, and the patient becomes pale, cold, and faint. If a\
comparatively small escape of blood takes place into the tissues, the\
sudden alteration in the size, shape, and tension of the aneurysm,\
together with loss of pulsation, may be the only local signs. When the\
bleeding is profuse, however, the parts beyond the aneurysm become\
greatly swollen, livid, and cold, and the pulse beyond is completely\
lost. The arrest of the blood supply may result in gangrene. Sometimes\
the pressure of the extravasated blood causes the skin to slough and,\
later, give way, and fatal haemorrhage results.\
\
The _treatment_ is carried out on the same lines as for a ruptured\
artery (p. 261), it being remembered, however, that the artery is\
diseased and does not lend itself to reconstructive procedures.\
\
_Suppuration_ may occur in the vicinity of an aneurysm, and the aneurysm\
may burst into the abscess which forms, so that when the latter points\
the pus is mixed with broken-down blood-clot, and finally free\
haemorrhage takes place. It has more than once happened that a surgeon\
has incised such an abscess without having recognised its association\
with aneurysm, with tragic results.\
\
#Treatment.#--In treating an aneurysm, the indications are to imitate\
Nature's method of cure by means of laminated clot.\
\
_Constitutional treatment_ consists in taking measures to reduce the\
arterial tension and to diminish the force of the heart's action. The\
patient must be kept in bed. A dry and non-stimulating diet is\
indicated, the quantity being gradually reduced till it is just\
sufficient to maintain nutrition. Saline purges are employed to reduce\
the vascular tension. The benefit derived from potassium iodide\
administered in full doses, as first recommended by George W. Balfour,\
probably depends on its depressing action on the heart and its\
therapeutic benefit in syphilis. Pain or restlessness may call for the\
use of opiates, of which heroin is the most efficient.\
\
_Local Treatment._--When constitutional treatment fails, local measures\
must be adopted, and many methods are available.\
\
#Endo-aneurysmorrhaphy.#--The operation devised by Rudolf Matas in 1888\
aims at closing the opening between the sac and its feeding artery, and\
in addition, folding the wall of the sac in such a way as to leave no\
vacant space. If there is marked disease of the vessel, Matas' operation\
is not possible and recourse is then had to ligation of the artery just\
above the sac.\
\
_Extirpation of the Sac--The Old Operation._--The procedure which goes\
by this name consists in exposing the aneurysm, incising the sac,\
clearing out the clots, and ligating the artery above and below the sac.\
This method is suitable to sacculated aneurysm of the limbs, so long as\
they are circumscribed and free from complications. It has been\
successfully practised also in aneurysm of the subclavian, carotid, and\
external iliac arteries. It is not applicable to cases in which there is\
such a degree of atheroma as would interfere with the successful\
ligation of the artery. The continuity of the artery may be restored by\
grafting into the gap left after excision of the sac a segment of the\
great saphena vein.\
\
_Ligation of the Artery._--The object of tying the artery is to diminish\
or to arrest the flow of blood through the aneurysm so that the blood\
coagulates both in the sac and in the feeding artery. The ligature may\
be applied on the cardiac side of the aneurysm--proximal ligation, or to\
the artery beyond--distal ligation.\
\
_Proximal Ligation._--The ligature may be applied immediately above the\
sac (Anel, 1710) or at a distance above (John Hunter, 1785). The\
_Hunterian operation_ ensures that the ligature is applied to a part of\
the artery that is presumably healthy and where relations are\
undisturbed by the proximity of the sac; the best example is the\
ligation of the superficial femoral artery in Scarpa's triangle or in\
Hunter's canal for popliteal aneurysm; it is on record that Syme\
performed this operation with cure of the aneurysm on thirty-nine\
occasions.\
\
It is to be noted that the Hunterian ligature does not aim at\
_arresting_ the flow of blood through the sac, but is designed so to\
diminish its volume and force as to favour the deposition within the sac\
of laminated clot. The development of the collateral circulation which\
follows upon ligation of the artery at a distance above the sac may be\
attended with just that amount of return stream which favours the\
deposit of laminated clot, and consequently the cure of the aneurysm;\
the return stream may, however, be so forcible as to prevent coagulation\
of the blood in the sac, or only to allow of the formation of a red\
thrombus which may in its turn be dispersed so that pulsation in the sac\
recurs. This does not necessarily imply failure to cure, as the\
recurrent pulsation may only be temporary; the formation of laminated\
clot may ultimately take place and lead to consolidation of the\
aneurysm.\
\
The least desirable result of the Hunterian ligature is met with in\
cases where, owing to widespread arterial disease, the collateral\
circulation does not develop and gangrene of the limb supervenes.\
\
_Anel's ligature_ is only practised as part of the operation which deals\
with the sac directly.\
\
_Distal Ligation._--The tying of the artery beyond the sac, or of its\
two branches where it bifurcates (Brasdor, 1760, and Wardrop, 1825), may\
arrest or only diminish the flow of blood through the sac. It is less\
successful than the proximal ligature, and is therefore restricted to\
aneurysms so situated as not to be amenable to other methods; for\
example, in aneurysm of the common carotid near its origin, the artery\
may be ligated near its bifurcation, or in aneurysm of the innominate\
artery, the carotid and subclavian arteries are tied at the seat of\
election.\
\
_Compression._--Digital compression of the feeding artery has been given\
up except as a preparation for operations on the sac with a view to\
favouring the development of a collateral circulation.\
\
_Macewen's acupuncture or "needling"_ consists in passing one or more\
fine, highly tempered steel needles through the tissues overlying the\
aneurysm, and through its outer wall. The needles are made to touch the\
opposite wall of the sac, and the pulsation of the aneurysm imparts a\
movement to them which causes them to scarify the inner surface of the\
sac. White thrombus forms on the rough surface produced, and leads to\
further coagulation. The needles may be left in position for some hours,\
being shifted from time to time, the projecting ends being surrounded\
with sterile gauze.\
\
The _Moore-Corradi method_ consists in introducing through the wall of\
the aneurysm a hollow insulated needle, through the lumen of which from\
10 to 20 feet of highly drawn silver or other wire is passed into the\
sac, where it coils up into an open meshwork (Fig. 73). The positive\
pole of a galvanic battery is attached to the wire, and the negative\
pole placed over the patient's back. A current, varying in strength from\
20 to 70 milliamperes, is allowed to flow for about an hour. The hollow\
needle is then withdrawn, but the wire is left _in situ_. The results\
are somewhat similar to those obtained by needling, but the clot formed\
on the large coil of wire is more extensive.\
\
[Illustration: FIG. 73.--Radiogram of Innominate Aneurysm after\
treatment by the Moore-Corradi method. Two feet of finely drawn silver\
wire were introduced. The patient, a woman, aet. 47, lived for ten months\
after operation, free from pain (cf. Fig. 75).]\
\
Colt's method of wiring has been mainly used in the treatment of\
abdominal aneurysm; gilt wire in the form of a wisp is introduced\
through the cannula and expands into an umbrella shape.\
\
_Subcutaneous Injections of Gelatin._--Three or four ounces of a 2 per\
cent. solution of white gelatin in sterilised water, at a temperature of\
about 100 o F., are injected into the subcutaneous tissue of the abdomen\
every two, three, or four days. In the course of a fortnight or three\
weeks improvement may begin. The clot which forms is liable to soften\
and be absorbed, but a repetition of the injection has in several cases\
established a permanent cure.\
\
_Amputation of the limb_ is indicated in cases complicated by\
suppuration, by secondary haemorrhage after excision or ligation, or by\
gangrene. Amputation at the shoulder was performed by Fergusson in a\
case of subclavian aneurysm, as a means of arresting the blood-flow\
through the sac.\
\
\
TRAUMATIC ANEURYSM\
\
The essential feature of a traumatic aneurysm is that it is produced by\
some form of injury which divides all the coats of the artery. The walls\
of the injured vessel are presumably healthy, but they form no part of\
the sac of the aneurysm. The sac consists of the condensed and thickened\
tissues around the artery.\
\
The injury to the artery may be a subcutaneous one such as a tear by a\
fragment of bone: much more commonly it is a punctured wound from a stab\
or from a bullet.\
\
The aneurysm usually forms soon after the injury is inflicted; the blood\
slowly escapes into the surrounding tissues, gradually displacing and\
condensing them, until they form a sac enclosing the effused blood.\
\
Less frequently a traumatic aneurysm forms some considerable time after\
the injury, from gradual stretching of the fibrous cicatrix by which the\
wound in the wall of the artery has been closed. The gradual stretching\
of this cicatrix results in condensation of the surrounding structures\
which form the sac, on the inner aspect of which laminated clot is\
deposited.\
\
A traumatic aneurysm is almost always sacculated, and, so long as it\
remains circumscribed, has the same characters as a pathological\
sacculated aneurysm, with the addition that there is a scar in the\
overlying skin. A traumatic aneurysm is liable to become diffuse--a\
change which, although attended with considerable risk of gangrene, has\
sometimes been the means of bringing about a cure.\
\
The treatment is governed by the same principles as apply to the\
pathological varieties, but as the walls of the artery are not diseased,\
operative measures dealing with the sac and the adjacent segment of the\
affected artery are to be preferred.\
\
\
ARTERIO-VENOUS ANEURYSM\
\
An abnormal communication between an artery and a vein constitutes an\
arterio-venous aneurysm. Two varieties are recognised--one in which the\
communication is direct--_aneurysmal varix_; the other in which the\
vein communicates with the artery through the medium of a sac--_varicose\
aneurysm_.\
\
Either variety may result from pathological causes, but in the majority\
of cases they are traumatic in origin, being due to such injuries as\
stabs, punctured wounds, and gun-shot injuries which involve both artery\
and vein. In former times the most common situation was at the bend of\
the elbow, the brachial artery being accidentally punctured in\
blood-letting from the median basilic vein. Arterio-venous aneurysm is a\
frequent result of injuries by modern high-velocity bullets--for\
example, in the neck or groin.\
\
In _aneurysmal varix_ the higher blood pressure in the artery forces\
arterial blood into the vein, which near the point of communication with\
the artery tends to become dilated, and to form a thick-walled sac,\
beyond which the vessel and its tributaries are distended and tortuous.\
The clinical features resemble those associated with varicose veins, but\
the entrance of arterial blood into the dilated veins causes them to\
pulsate, and produces in them a vibratory thrill and a loud murmur. In\
those at the groin, the distension of the veins may be so great that\
they look like sinuses running through the muscles, a feature that must\
be taken into account in any operation.\
\
As the condition tends to remain stationary, the support of an elastic\
bandage is all that is required; but when the condition progresses and\
causes serious inconvenience, it may be necessary to cut down and expose\
the communication between the artery and vein, and, after separating the\
vessels, to close the opening in each by suture; this may be difficult\
or impossible if the parts are matted from former suppuration. If it is\
impossible thus to obliterate the communication, the artery should be\
ligated above and below the point of communication; although the risk of\
gangrene is considerable unless means are taken to develop the\
collateral circulation beforehand (Makins).\
\
_Varicose aneurysm_ usually develops in relation to a traumatic\
aneurysm, the sac becoming adherent to an adjacent vein, and ultimately\
opening into it. In this way a communication between the artery and the\
vein is established, and the clinical features are those of a\
combination of aneurysm and aneurysmal varix.\
\
As there is little tendency to spontaneous cure, and as the aneurysm is\
liable to increase in size and finally to rupture, operative treatment\
is usually called for. This is carried out on the same lines as for\
aneurysmal varix, and at the same time incising the sac, turning out the\
clots, and ligating any branches which open into the sac. If it can be\
avoided, the vein should not be ligated.\
\
\
ANEURYSMS OF INDIVIDUAL ARTERIES\
\
#Thoracic Aneurysm.#--All varieties of aneurysm occur in the aorta, the\
fusiform being the most common, although a sacculated aneurysm\
frequently springs from a fusiform dilatation.\
\
The _clinical features_ depend chiefly on the direction in which the\
aneurysm enlarges, and are not always well marked even when the sac is\
of considerable size. They consist in a pulsatile swelling--sometimes in\
the supra-sternal notch, but usually towards the right side of the\
sternum--with an increased area of dulness on percussion. With the\
X-rays a dark shadow is seen corresponding to the sac. Pain is usually a\
prominent symptom, and is largely referable to the pressure of the\
aneurysm on the vertebrae or the sternum, causing erosion of these bones.\
Pressure on the thoracic veins and on the air-passage causes cyanosis\
and dyspnoea. When the oesophagus is pressed upon, the patient may have\
difficulty in swallowing. The left recurrent nerve may be stretched or\
pressed upon as it hooks round the arch of the aorta, and hoarseness of\
the voice and a characteristic "brassy" cough may result from paralysis\
of the muscles of the larynx which it supplies. The vagus, the phrenic,\
and the spinal nerves may also be pressed upon. When the aneurysm is on\
the transverse part of the arch, the trachea is pulled down with each\
beat of the heart--a clinical phenomena known as the "tracheal tug."\
Aneurysm of the descending aorta may, after eroding the bodies of the\
vertebrae (Fig. 71) and posterior portions of the ribs, form a swelling\
in the back to the left of the spine.\
\
Inasmuch as obliteration of the sac and the feeding artery is out of the\
question, surgical treatment is confined to causing coagulation of the\
blood in an extension or pouching of the sac, which, making its way\
through the parietes of the chest, threatens to rupture externally. This\
may be achieved by Macewen's needles or by the introduction of wire into\
the sac. We have had cases under observation in which the treatment\
referred to has been followed by such an amount of improvement that the\
patient has been able to resume a laborious occupation for one or more\
years. Christopher Heath found that improvement followed ligation of the\
left common carotid in aneurysm of the transverse part of the aortic\
arch.\
\
[Illustration: FIG. 74.--Thoracic Aneurysm, threatening to rupture\
externally, but prevented from doing so by Macewen's needling. The\
needles were left in for forty-eight hours.]\
\
#Abdominal Aneurysm.#--Aneurysm is much less frequent in the abdominal\
than in the thoracic aorta. While any of the large branches in the\
abdomen may be affected, the most common seats are in the aorta itself,\
just above the origin of the coeliac artery and at the bifurcation.\
\
The _clinical features_ vary with the site of the aneurysm and with its\
rapidity and direction of growth. A smooth, rounded swelling, which\
exhibits expansile pulsation, forms, usually towards the left of the\
middle line. It may extend upwards under cover of the ribs, downwards\
towards the pelvis, or backward towards the loin. On palpation a\
systolic thrill may be detected, but the presence of a murmur is neither\
constant nor characteristic. Pain is usually present; it may be\
neuralgic in character, or may simulate renal colic. When the aneurysm\
presses on the vertebrae and erodes them, the symptoms simulate those of\
spinal caries, particularly if, as sometimes happens, symptoms of\
compression paraplegia ensue. In its growth the swelling may press upon\
and displace the adjacent viscera, and so interfere with their\
functions.\
\
The _diagnosis_ has to be made from solid or cystic tumours overlying\
the artery; from a "pulsating aorta"; and from spinal caries; much help\
is obtained by the use of the X-rays.\
\
The condition usually proves fatal, either by the aneurysm bursting into\
the peritoneal cavity, or by slow leakage into the retro-peritoneal\
tissue.\
\
The Moore-Corradi method has been successfully employed, access to the\
sac having been obtained by opening the abdomen. Ligation of the aorta\
has so far been unsuccessful, but in one case operated upon by Keen the\
patient survived forty-eight days.\
\
#Innominate aneurysm# may be of the fusiform or of the sacculated\
variety, and is frequently associated with pouching of the aorta. It\
usually grows upwards and laterally, projecting above the sternum and\
right clavicle, which may be eroded or displaced (Fig. 75). Symptoms of\
pressure on the structures in the neck, similar to those produced by\
aortic aneurysm, occur. The pulses in the right upper extremity and in\
the right carotid and its branches are diminished and delayed. Pressure\
on the right brachial plexus causes shooting pain down the arm and\
muscular paresis on that side. Vaso-motor disturbances and contraction\
of the pupil on the right side may result from pressure on the\
sympathetic. Death may take place from rupture, or from pressure on the\
air-passage.\
\
[Illustration: FIG. 75.--Innominate Aneurysm in a woman, aet. 47, eight\
months after treatment by Moore-Corradi method (cf. Fig. 73).]\
\
The available methods of treatment are ligation of the right common\
carotid and third part of the right subclavian (Wardrop's operation), of\
which a number of successful cases have been recorded. Those most\
suitable for ligation are cases in which the aneurysm is circumscribed\
and globular (Sheen). If ligation is found to be impracticable, the\
Moore-Corradi method or Macewen's needling may be tried.\
\
#Carotid Aneurysms.#--Aneurysm of the _common carotid_ is more frequent\
on the right than on the left side, and is usually situated either at\
the root of the neck or near the bifurcation. It is the aneurysm most\
frequently met with in women. From its position the swelling is liable\
to press on the vagus, recurrent and sympathetic nerves, on the\
air-passage, and on the oesophagus, giving rise to symptoms referable to\
such pressure. There may be cerebral symptoms from interference with the\
blood supply of the brain.\
\
Aneurysm near the origin has to be diagnosed from subclavian,\
innominate, and aortic aneurysm, and from other swellings--solid or\
fluid--met with in the neck. It is often difficult to determine with\
precision the trunk from which an aneurysm at the root of the neck\
originates, and not infrequently more than one vessel shares in the\
dilatation. A careful consideration of the position in which the\
swelling first appeared, of the direction in which it has progressed, of\
its pressure effects, and of the condition of the pulses beyond, may\
help in distinguishing between aortic, innominate, carotid, and\
subclavian aneurysms. Skiagraphy is also of assistance in recognising\
the vessel involved.\
\
Tumours of the thyreoid, enlarged lymph glands, and fatty and\
sarcomatous tumours can usually be distinguished from aneurysm by the\
history of the swelling and by physical examination. Cystic tumours and\
abscesses in the neck are sometimes more difficult to differentiate on\
account of the apparently expansile character of the pulsation\
transmitted to them. The fact that compression of the vessel does not\
affect the size and tension of these fluid swellings is useful in\
distinguishing them from aneurysm.\
\
_Treatment._--Digital compression of the vessel against the transverse\
process of the sixth cervical vertebra--the "carotid tubercle"--has been\
successfully employed in the treatment of aneurysm near the bifurcation.\
Proximal ligation in the case of high aneurysms, or distal ligation in\
those situated at the root of the neck, is more certain. Extirpation of\
the sac is probably the best method of treatment, especially in those of\
traumatic origin. These operations are attended with considerable risk\
of hemiplegia from interference with the blood supply of the brain.\
\
The _external carotid_ and the cervical portion of the _internal\
carotid_ are seldom the primary seat of aneurysm, although they are\
liable to be implicated by the upward spread of an aneurysm at the\
bifurcation of the common trunk. In addition to the ordinary signs of\
aneurysm, the clinical manifestations are chiefly referable to pressure\
on the pharynx and larynx, and on the hypoglossal nerve. Aneurysm of the\
internal carotid is of special importance on account of the way in which\
it bulges into the pharynx in the region of the tonsil, in some cases\
closely simulating a tonsillar abscess. Cases are on record in which\
such an aneurysm has been mistaken for an abscess and incised, with\
disastrous results.\
\
_Aneurysmal varix_ may occur in the neck as a result of stabs or bullet\
wounds. The communication is usually between the common carotid artery\
and the internal jugular vein. The resulting interference with the\
cerebral circulation causes headache, giddiness, and other brain\
symptoms, and a persistent loud murmur is usually a source of annoyance\
to the patient and may be sufficient indication for operative treatment.\
\
#Intracranial aneurysm# involves the internal carotid and its branches,\
or the basilar artery, and appears to be more frequently associated with\
syphilis and with valvular disease of the heart than are external\
aneurysms. It gives rise to symptoms similar to those of other\
intracranial tumours, and there is sometimes a loud murmur. It usually\
proves fatal by rupture, and intracranial haemorrhage. The treatment is\
to ligate the common carotid or the vertebral artery in the neck,\
according to the seat of the aneurysm.\
\
#Orbital Aneurysm.#--The term pulsating exophthalmos is employed to\
embrace a number of pathological conditions, including aneurysm, in\
which the chief symptoms are pulsation in the orbit and protrusion of\
the eyeball. There may be, in addition, congestion and oedema of the\
eyelids, and a distinct thrill and murmur, which can be controlled by\
compression of the common carotid in the neck. Varying degrees of ocular\
paralysis and of interference with vision may also be present.\
\
These symptoms are due, in the majority of cases, to an aneurysmal varix\
of the internal carotid artery and cavernous sinus, which is often\
traumatic in origin, being produced either by fracture of the base of\
the skull or by a punctured wound of the orbit. In other cases they are\
due to aneurysm of the ophthalmic artery, to thrombosis of the cavernous\
sinus, and, in rare instances, to cirsoid aneurysm.\
\
If compression of the common carotid is found to arrest the pulsation,\
ligation of this vessel is indicated.\
\
#Subclavian Aneurysm.#--Subclavian aneurysm is usually met with in men\
who follow occupations involving constant use of the shoulder--for\
example, dock-porters and coal-heavers. It is more common on the right\
side.\
\
The aneurysm usually springs from the third part of the artery, and\
appears as a tense, rounded, pulsatile swelling just above the clavicle\
and to the outer side of the sterno-mastoid muscle. It occasionally\
extends towards the thorax, where it may become adherent to the pleura.\
The radial pulse on the same side is small and delayed. Congestion and\
oedema of the arm, with pain, numbness, and muscular weakness, may result\
from pressure on the veins and nerves as they pass under the clavicle;\
and pressure on the phrenic nerve may induce hiccough. The aneurysm is\
of slow growth, and occasionally undergoes spontaneous cure.\
\
The conditions most likely to be mistaken for it are a soft, rapidly\
growing sarcoma, and a normal artery raised on a cervical rib.\
\
On account of the relations of the artery and of its branches, treatment\
is attended with greater difficulty and danger in subclavian than in\
almost any other form of external aneurysm. The available operative\
measures are proximal ligation of the innominate, and distal ligation.\
In some cases it has been found necessary to combine distal ligation\
with amputation at the shoulder-joint, to prevent the collateral\
circulation maintaining the flow through the aneurysm. Matas' operation\
has been successfully performed by Hogarth Pringle.\
\
#Axillary Aneurysm.#--This is usually met with in the right arm of\
labouring men and sailors, and not infrequently follows an injury in the\
region of the shoulder. The vessel may be damaged by the head of a\
dislocated humerus or in attempts to reduce the dislocation, by the\
fragments of a fractured bone, or by a stab or cut. Sometimes the vein\
also is injured and an arterio-venous aneurysm established.\
\
Owing to the laxity of the tissues, it increases rapidly, and it may\
soon attain a large size, filling up the axilla, and displacing the\
clavicle upwards. This renders compression of the third part of the\
subclavian difficult or impossible. It may extend beneath the clavicle\
into the neck, or, extending inwards may form adhesions to the chest\
wall, and, after eroding the ribs, to the pleura.\
\
The usual symptoms of aneurysm are present, and the pressure effects on\
the veins and nerves are similar to those produced by an aneurysm of the\
subclavian. Intra-thoracic complications, such as pleurisy or pneumonia,\
are not infrequent when there are adhesions to the chest wall and\
pleura. Rupture may take place externally, into the shoulder-joint, or\
into the pleura.\
\
Extirpation of the sac is the operation of choice, but, if this is\
impracticable, ligation of the third part of the subclavian may be had\
recourse to.\
\
#Brachial aneurysm# usually occurs at the bend of the elbow, is of\
traumatic origin, and is best treated by excision of the sac.\
\
_Aneurysmal varix_, which was frequently met with in this situation in\
the days of the barber-surgeons,--usually as a result of the artery\
having been accidentally wounded while performing venesection of the\
median basilic vein,--may be treated, according to the amount of\
discomfort it causes, by a supporting bandage, or by ligation of the\
artery above and below the point of communication.\
\
Aneurysms of the vessels of the #forearm and hand# call for no special\
mention; they are almost invariably traumatic, and are treated by\
excision of the sac.\
\
#Inguinal Aneurysm# (_Aneurysm of the Iliac and Femoral\
Arteries_).--Aneurysms appearing in the region of Poupart's ligament may\
have their origin in the external or common iliac arteries or in the\
upper part of the femoral. On account of the tension of the fascia lata,\
they tend to spread upwards towards the abdomen, and, to a less extent,\
downwards into the thigh. Sometimes a constriction occurs across the\
sac at the level of Poupart's ligament.\
\
The pressure exerted on the nerves and veins of the lower extremity\
causes pain, congestion, and oedema of the limb. Rupture may take place\
externally, or into the cellular tissue of the iliac fossa.\
\
These aneurysms have to be diagnosed from pulsating sarcoma growing from\
the pelvic bones, and from an abscess or a mass of enlarged lymph glands\
overlying the artery and transmitting its pulsation.\
\
The method of treatment that has met with most success is ligation of\
the common or external iliac, reached either by reflecting the\
peritoneum from off the iliac fossa (extra-peritoneal operation), or by\
going through the peritoneal cavity (trans-peritoneal operation).\
\
#Gluteal Aneurysm.#--An aneurysm in the buttock may arise from the\
superior or from the inferior gluteal artery, but by the time it forms a\
salient swelling it is seldom possible to recognise by external\
examination in which vessel it takes origin. The special symptoms to\
which it gives rise are pain down the limb from pressure on the sciatic\
nerve, and interference with the movements at the hip.\
\
Ligation of the hypogastric (internal iliac) by the trans-peritoneal\
route is the most satisfactory method of treatment. Extirpation of the\
sac is difficult and dangerous, especially when the aneurysm has spread\
into the pelvis.\
\
#Femoral Aneurysm.#--Aneurysm of the femoral artery beyond the origin of\
the profunda branch is usually traumatic in origin, and is more common\
in Scarpa's triangle than in Hunter's canal. Any of the methods already\
described is available for their treatment--the choice lying between\
Matas' operation and ligation of the external iliac.\
\
Aneurysm of the _profunda femoris_ is distinguished from that of the\
main trunk by the fact that the pulses beyond are, in the former,\
unaffected, and by the normal artery being felt pulsating over or\
alongside the sac.\
\
In _aneurysmal varix_, a not infrequent result of a bullet wound or a\
stab, the communication with the vein may involve the main trunk of the\
femoral artery. Should operative interference become necessary as a\
result of progressive increase in size of the tumour, or progressive\
distension of the veins of the limb, an attempt should be made to\
separate the vessels concerned and to close the opening in each by\
suture. If this is impracticable, the artery is tied above and below the\
communication; gangrene of the limb may supervene, and we have observed\
a case in which the gangrene extended up to the junction of the middle\
and lower thirds of the thigh, and in which recovery followed upon\
amputation of the thigh.\
\
#Popliteal Aneurysm.#--This is the most common surgical aneurysm, and is\
not infrequently met with in both limbs. It is generally due to disease\
of the artery, and repeated slight strains, which are so liable to occur\
at the knee, play an important part in its formation. In former times it\
was common in post-boys, from the repeated flexion and extension of the\
knee in riding.\
\
The aneurysm is usually of the sacculated variety, and may spring from\
the front or from the back of the vessel. It may exert pressure on the\
bones and ligaments of the joint, and it has been known to rupture into\
the articulation. The pain, stiffness, and effusion into the joint which\
accompany these changes often lead to an erroneous diagnosis of joint\
disease. The sac may press upon the popliteal artery or vein and their\
branches, causing congestion and oedema of the leg, and lead to gangrene.\
Pressure on the tibial and common peroneal nerves gives rise to severe\
pain, muscular cramp, and weakness of the leg.\
\
The differential diagnosis is to be made from abscess, bursal cyst,\
enlarged glands, and sarcoma, especially pulsating sarcoma of one of the\
bones entering into the knee joint.\
\
The choice of operation lies between ligation of the femoral artery in\
Hunter's canal, and Matas' operation of aneurysmo-arteriorrhaphy. The\
success which attends the Hunterian operation is evidenced by the fact\
that Syme performed it thirty-seven times without a single failure. If\
it fails, the old operation should be considered, but it is a more\
serious operation, and one which is more liable to be followed by\
gangrene of the limb. Experience shows that ligation of the vein, or\
even the removal of a portion of it, is not necessarily followed by\
gangrene. The risk of gangrene is diminished by a course of digital\
compression of the femoral artery, before operating on the aneurysm.\
\
_Aneurysmal varix_ is sometimes met with in the region of the popliteal\
space. It is characterised by the usual symptoms, and is treated by\
palliative measures, or by ligation of the artery above and below the\
point of communication.\
\
_Aneurysm_ in the #leg and foot# is rare. It is almost always traumatic,\
and is treated by excision of the sac.\
\
\
\
\
CHAPTER XV\
\
THE LYMPH VESSELS AND GLANDS\
\
\
Anatomy and Physiology--INJURIES OF LYMPH VESSELS--_Wounds of\
    thoracic duct_--DISEASES OF LYMPH VESSELS--Lymphangitis:\
    _Varieties_--Lymphangiectasis--Filarial\
    disease--Lymphangioma--DISEASES OF LYMPH\
    GLANDS--Lymphadenitis: _Septic_; _Tuberculous_;\
    _Syphilitic_--Lymphadenoma--Leucocythaemia--TUMOURS.\
\
#Surgical Anatomy and Physiology.#--Lymph is essentially blood plasma,\
which has passed through the walls of capillaries. After bathing\
and nourishing the tissues, it is collected by lymph vessels, which\
return it to the blood stream by way of the thoracic duct. These lymph\
vessels take origin in the lymph spaces of the tissues and in the\
walls of serous cavities, and they usually run alongside blood\
vessels--_perivascular lymph vessels_. They have a structure similar to\
that of veins, but are more abundantly provided with valves. Along the\
course of the lymph trunks are the _lymph glands_, which possess a\
definite capsule and are composed of a reticulated connective tissue,\
the spaces of which are packed with leucocytes. The glands act as\
filters, arresting not only inert substances, such as blood pigment\
circulating in the lymph, but also living elements, such as cancer cells\
or bacteria. As it passes through a gland the lymph is brought into\
intimate contact with the leucocytes, and in bacterial infections there\
is always a struggle between the organisms and the leucocytes, so that\
the glands may be looked upon as an important line of defence, retarding\
or preventing the passage of bacteria and their products into the\
general circulation. The infective agent, moreover, in order to reach\
the blood stream, must usually overcome the resistance of several\
glands.\
\
Lymph glands are, for the most part, arranged in groups or chains, such\
as those in the axilla, neck, and groin. In any given situation they\
vary in number and size in different individuals, and fresh glands may\
be formed on comparatively slight stimulus, and disappear when the\
stimulus is withdrawn. The best-known example of this is the increase in\
the number of glands in the axilla which takes place during lactation;\
when this function ceases, many of the glands become involuted and are\
transformed into fat, and in the event of a subsequent lactation they\
are again developed. After glands have been removed by operation, new\
ones may be formed.\
\
The following are the more important groups of glands, and the areas\
drained by them in the head and neck and in the extremities.\
\
#Head and Neck.#--_The anterior auricular (parotid and pre-auricular)\
glands_ lie beneath the parotid fascia in front of the ear, and some\
are partly embedded in the substance of the parotid gland; they drain\
the parts about the temple, cheek, eyelids, and auricle, and are\
frequently the seat of tuberculous disease. _The occipital gland_,\
situated over the origin of the trapezius from the superior curved line,\
drains the top and back of the head; it is rarely infected. _The\
posterior auricular (mastoid) glands_ lie over the mastoid process, and\
drain the side of the head and auricle. These three groups pour their\
lymph into the superficial cervical glands. _The submaxillary_--two to\
six in number--lie along the lower order of the mandible from the\
symphysis to the angle, the posterior ones (paramandibular) being\
closely connected with the submaxillary salivary gland. They receive\
lymph from the face, lips, floor of the mouth, gums, teeth, anterior\
part of tongue, and the alae nasi, and from the pre-auricular glands. The\
lymph passes from them into the deeper cervical glands. They are\
frequently infected with tubercle, with epithelioma which has spread to\
them from the mouth, and also with pyogenic organisms. _The submental\
glands_ lie in or close to the median line between the anterior bellies\
of the digastric muscles, and receive lymph from the lips. It is rare\
for them to be the seat of tubercle, but in epithelioma of the lower lip\
and floor of the mouth they are infected at an early stage of the\
disease. _The supra-hyoid gland_ lies a little farther back, immediately\
above the hyoid bone, and receives lymph from the tongue. _The\
superficial cervical (external jugular) glands_, when present, lie along\
the external jugular vein, and receives lymph from the occipital and\
auricular glands and from the auricle. _The sterno-mastoid\
glands_--glandulae concatinatae--form a chain along the posterior edge of\
the sterno-mastoid muscle, some of them lying beneath the muscle. They\
are commonly enlarged in secondary syphilis. _The superior deep cervical\
(internal jugular) glands_--from six to twenty in number--form a\
continuous chain along the internal jugular vein, beneath the\
sterno-mastoid muscle. They drain the various groups of glands which lie\
nearer the surface, also the interior of the skull, the larynx, trachea,\
thyreoid, and lower part of the pharynx, and pour their lymph into the\
main trunks at the root of the neck. Belonging to this group is one\
large gland (the tonsillar gland) which lies behind the posterior belly\
of the digastric, and rests in the angle between the internal jugular\
and common facial veins. It is commonly enlarged in affections of the\
tonsil and posterior part of the tongue. In the same group are three or\
four glands which lie entirely under cover of the upper end of the\
sterno-mastoid muscle, and surround the accessory nerve before it\
perforates the muscle. The deep cervical glands are commonly infected by\
tubercle and also by epithelioma secondary to disease in the tongue or\
throat. _The inferior deep cervical (supra-clavicular) glands_ lie in\
the posterior triangle, above the clavicle. They receive lymph from the\
lowest cervical glands, from the upper part of the chest wall, and from\
the highest axillary glands. They are frequently infected in cancer of\
the breast; those on the left side also in cancer of the stomach. The\
removal of diseased supra-clavicular glands is not to be lightly\
undertaken, as difficulties are liable to ensue in connection with the\
thoracic duct, the pleura, or the junction of the subclavian and\
internal jugular veins. _The retro-pharyngeal glands_ lie on each side\
of the median line upon the rectus capitis anticus major muscle and in\
front of the pre-vertebral layer of the cervical fascia. They receive\
part of the lymph from the posterior wall of the pharynx, the interior\
of the nose and its accessory cavities, the auditory (Eustachian) tube,\
and the tympanum. When they are infected with pyogenic organisms or\
with tubercle bacilli, they may lead to the formation of one form of\
retro-pharyngeal abscess.\
\
#Upper Extremity.#--_The epi-trochlear and cubital glands_ vary in\
number, that most commonly present lying about an inch and a half above\
the medial epi-condyle, and other and smaller glands may lie along the\
medial (internal) bicipital groove or at the bend of the elbow. They\
drain the ulnar side of the hand and forearm, and pour their lymph into\
the axillary group. The epi-trochlear gland is sometimes enlarged in\
syphilis. _The axillary glands_ are arranged in groups: a central group\
lies embedded in the axillary fascia and fat, and is often related to an\
opening in it; a posterior or subscapular group lies along the line of\
the subscapular vessels; anterior or pectoral groups lie behind the\
pectoralis minor, along the medial side of the axillary vein, and an\
inter-pectoral group, between the two pectoral muscles. The axillary\
glands receive lymph from the arm, mamma, and side of the chest, and\
pass it on into the lowest cervical glands and the main lymph trunk.\
They are frequently the seat of pyogenic, tuberculous, and cancerous\
infection, and their complete removal is an essential part of the\
operation for cancer of the breast.\
\
#Lower Extremity.#--_The popliteal glands_ include one superficial gland\
at the termination of the small saphenous vein, and several deeper ones\
in relation to the popliteal vessels. They receive lymph from the toes\
and foot, and transmit it to the inguinal glands. _The femoral glands_\
lie vertically along the upper part of the great saphenous vein, and\
receive lymph from the leg and foot; from them the lymph passes to the\
deep inguinal and external iliac glands. The femoral glands often\
participate in pyogenic infections entering through the skin of the toes\
and sole of the foot. _The superficial inguinal glands_ lie along the\
inguinal (Poupart's) ligament, and receive lymph from the external\
genitals, anus, perineum, buttock, and anterior abdominal wall. The\
lymph passes on to the deep inguinal and external iliac glands. The\
superficial glands through their relations to the genitals are\
frequently the subject of venereal infection, and also of epithelioma\
when this disease affects the genitals or anus; they are rarely the seat\
of tuberculosis. _The deep inguinal glands_ lie on the medial side of\
the femoral vein, and sometimes within the femoral canal. They receive\
lymph from the deep lymphatics of the lower limb, and some of the\
efferent vessels from the femoral and superficial inguinal glands. The\
lymph then passes on through the femoral canal to the external iliac\
glands. The extension of malignant disease, whether cancer or sarcoma,\
can often be traced along these deeper lymphatics into the pelvis, and\
as the obstruction to the flow of lymph increases there is a\
corresponding increase in the swollen dropsical condition of the lower\
limb on the same side.\
\
The glands of the _thorax_ and _abdomen_ will be considered with the\
surgery of these regions.\
\
\
INJURIES OF LYMPH VESSELS\
\
Lymph vessels are divided in all wounds, and the lymph that escapes from\
them is added to any discharge that may be present. In injuries of\
larger trunks the lymph may escape in considerable quantity as a\
colourless, watery fluid--_lymphorrhagia_; and the opening through which\
it escapes is known as a _lymphatic fistula_. This has been observed\
chiefly after extensive operation for the removal of malignant glands in\
the groin where there already exists a considerable degree of\
obstruction to the lymph stream, and in such cases the lymph, including\
that which has accumulated in the vessels of the limb, may escape in\
such abundance as to soak through large dressings and delay healing.\
Ultimately new lymph channels are formed, so that at the end of from\
four to six weeks the discharge of lymph ceases and the wound heals.\
\
_Lymphatic Oedema._--When the lymphatic return from a limb has been\
seriously interfered with,--as, for example, when the axillary contents\
has been completely cleared out in operating for cancer of the\
breast,--a condition of lymphatic oedema may result, the arm becoming\
swollen, tight, and heavy.\
\
Various degrees of the conditions are met with; in the severe forms,\
there is pain, as well as incapacity of the limb. As in ordinary oedema,\
the condition is relieved by elevation of the limb, but not nearly to\
the same degree; in time the tissues become so hard and tense as\
scarcely to pit on pressure; this is in part due to the formation of new\
connective tissue and hypertrophy of the skin; in advanced cases there\
is a gradual transition into one form of elephantiasis.\
\
Handley has devised a method of treatment--_lymphangioplasty_--the\
object of which is to drain the lymph by embedding a number of silk\
threads in the subcutaneous cellular tissue.\
\
#Wounds of the Thoracic Duct.#--The thoracic duct usually opens at the\
angle formed by the junction of the left internal jugular and subclavian\
veins, but it may open into either of these vessels by one or by several\
channels, or the duct may be double throughout its course. There is a\
smaller duct on the right side--the right lymphatic duct. The duct or\
ducts may be displaced by a tumour or a mass of enlarged glands, and may\
be accidentally wounded in dissections at the root of the neck; jets of\
milky fluid--chyle--may at once escape from it. The jets are rhythmical\
and coincide with expiration. The injury may, however, not be observed\
at the time of operation, but later through the dressings being soaked\
with chyle--_chylorrhoea_. If the wound involves the only existing main\
duct and all the chyle escapes, the patient suffers from intense thirst,\
emaciation, and weakness, and may die of inanition; but if, as is\
usually the case, only one of several collateral channels is implicated,\
the loss of chyle may be of little moment, as the discharge usually\
ceases. If the wound heals so that the chyle is prevented from escaping,\
a fluctuating swelling may form beneath the scar; in course of time it\
gradually disappears.\
\
An attempt should be made to close the wound in the duct by means of a\
fine suture; failing this, the duct must be occluded by a ligature as if\
it were a bleeding artery. The tissues are then stitched over it and the\
skin wound accurately closed, so as to obtain primary union, firm\
pressure being applied by dressings and an elastic webbing bandage. Even\
if the main duct is obliterated, a collateral circulation is usually\
established. A wound of the right lymphatic duct is of less importance.\
\
_Subcutaneous rupture of the thoracic duct_ may result from a crush of\
the thorax. The chyle escapes and accumulates in the cellular tissue of\
the posterior mediastinum, behind the peritoneum, in the pleural cavity\
(_chylo-thorax_), or in the peritoneal cavity (_chylous ascites_). There\
are physical signs of fluid in one or other of these situations, but, as\
a rule, the nature of the lesion is only recognised when chyle is\
withdrawn by the exploring needle.\
\
\
DISEASES OF LYMPH VESSELS\
\
#Lymphangitis.#--Inflammation of peripheral lymph vessels usually\
results from some primary source of pyogenic infection in the skin. This\
may be a wound or a purulent blister, and the streptococcus pyogenes is\
the organism most frequently present. _Septic_ lymphangitis is commonly\
met with in those who, from the nature of their occupation, handle\
infective material. A _gonococcal_ form has been observed in those\
suffering from gonorrhoea.\
\
The inflammation affects chiefly the walls of the vessels, and is\
attended with clotting of the lymph. There is also some degree of\
inflammation of the surrounding cellular tissue--_peri-lymphangitis_.\
One or more abscesses may form along the course of the vessels, or a\
spreading cellulitis may supervene.\
\
The _clinical features_ resemble those of other pyogenic infections, and\
there are wavy red lines running from the source of infection towards\
the nearest lymph glands. These correspond to the inflamed vessels, and\
are the seat of burning pain and tenderness. The associated glands are\
enlarged and painful. In severe cases the symptoms merge into those of\
septicaemia. When the deep lymph vessels alone are involved, the\
superficial red lines are absent, but the limb becomes greatly swollen\
and pits on pressure.\
\
In cases of extensive lymphangitis, especially when there are repeated\
attacks, the vessels are obliterated by the formation of new connective\
tissue and a persistent solid oedema results, culminating in one form of\
elephantiasis.\
\
_Treatment._--The primary source of infection is dealt with on the usual\
lines. If the lymphangitis affects an extremity, Bier's elastic bandage\
is applied, and if suppuration occurs, the pus is let out through one or\
more small incisions; in other parts of the body Klapp's suction bells\
are employed. An autogenous vaccine may be prepared and injected. When\
the condition has subsided, the limb is massaged and evenly bandaged to\
promote the disappearance of oedema.\
\
_Tuberculous Lymphangitis._--Although lymph vessels play an important\
role in the spread of tuberculosis, the clinical recognition of the\
disease in them is exceptional. The infection spreads upwards along the\
superficial lymphatics, which become nodularly thickened; at one or more\
points, larger, peri-lymphangitic nodules may form and break down into\
abscesses and ulcers; the nearest group of glands become infected at an\
early stage. When the disease is widely distributed throughout the\
lymphatics of the limb, it becomes swollen and hard--a condition\
illustrated by lupus elephantiasis.\
\
_Syphilitic lymphangitis_ is observed in cases of primary syphilis, in\
which the vessels of the dorsum of the penis can be felt as indurated\
cords.\
\
In addition to acting as channels for the conveyance of bacterial\
infection, _lymph vessels frequently convey the cells of malignant\
tumours_, and especially cancer, from the seat of the primary disease to\
the nearest lymph glands, and they may themselves become the seat of\
cancerous growth forming nodular cords. The permeation of cancer by way\
of the lymphatics, described by Sampson Handley, has already been\
referred to.\
\
#Lymphangiectasis# is a dilated or varicose condition of lymph vessels.\
It is met with as a congenital affection in the tongue and lips, or it\
may be acquired as the result of any condition which is attended with\
extensive obliteration or blocking of the main lymph trunks. An\
interesting type of lymphangiectasis is that which results from the\
presence of the _filaria Bancrofti_ in the vessels, and is observed\
chiefly in the groin, spermatic cord, and scrotum of persons who have\
lived in the tropics.\
\
_Filarial disease in the lymphatics of the groin_ appears as a soft,\
doughy swelling, varying in size from a walnut to a cocoa-nut; it may\
partly disappear on pressure and when the patient lies down.\
\
The patient gives a history of feverish attacks of the nature of\
lymphangitis during which the swelling becomes painful and tender. These\
attacks may show a remarkable periodicity, and each may be followed by\
an increase in the size of the swelling, which may extend along the\
inguinal canal into the abdomen, or down the spermatic cord into the\
scrotum. On dissection, the swelling is found to be made up of dilated,\
tortuous, and thickened lymph vessels in which the parent worm is\
sometimes found, and of greatly enlarged lymph glands which have\
undergone fibrosis, with giant-cell formation and eosinophile\
aggregations. The fluid in the dilated vessels is either clear or\
turbid, in the latter case resembling chyle. The affection is frequently\
bilateral, and may be associated with lymph scrotum, with elephantiasis,\
and with chyluria.\
\
The _diagnosis_ is to be made from such other swellings in the groin as\
hernia, lipoma, or cystic pouching of the great saphenous vein. It is\
confirmed by finding the recently dead or dying worms in the inflamed\
lymph glands.\
\
_Treatment._--When the disease is limited to the groin or scrotum,\
excision may bring about a permanent cure, but it may result in the\
formation of lymphatic sinuses and only afford temporary relief.\
\
#Lymphangioma.#--A lymphangioma is a swelling composed of a series of\
cavities and channels filled with lymph and freely communicating with\
one another. The cavities result either from the new formation of lymph\
spaces or vessels, or from the dilatation of those which already exist;\
their walls are composed of fibro-areolar tissue lined by endothelium\
and strengthened by non-striped muscle. They are rarely provided with a\
definite capsule, and frequently send prolongations of their substance\
between and into muscles and other structures in their vicinity. They\
are of congenital origin and usually make their appearance at or shortly\
after birth. When the tumour is made up of a meshwork of caverns and\
channels, it is called a _cavernous lymphangioma_; when it is composed\
of one or more cysts, it is called a _cystic lymphangioma_. It is\
probable that the cysts are derived from the caverns by breaking down\
and absorption of the intervening septa, as transition forms between the\
cavernous and cystic varieties are sometimes met with.\
\
The _cavernous lymphangioma_ appears as an ill-defined, soft swelling,\
presenting many of the characters of a subcutaneous haemangioma, but it\
is not capable of being emptied by pressure, it does not become tense\
when the blood pressure is raised, as in crying, and if the tumour is\
punctured, it yields lymph instead of blood. It also resembles a lipoma,\
especially the congenital variety which grows from the periosteum, and\
the differential diagnosis between these is rarely completed until the\
swelling is punctured or explored by operation. If treatment is called\
for, it is carried out on the same lines as for haemangioma, by means of\
electrolysis, igni-puncture, or excision. Complete excision is rarely\
possible because of the want of definition and encapsulation, but it is\
not necessary for cure, as the parts that remain undergo cicatrisation.\
\
[Illustration: FIG. 76.--Congenital Cystic Tumour or Hygroma of Axilla.\
\
(From a photograph lent by Dr. Lediard.)]\
\
The _cystic lymphangioma_, _lymphatic cyst_, or _congenital cystic\
hygroma_ is most often met with in the neck--_hydrocele of the neck_; it\
is situated beneath the deep fascia, and projects either in front of or\
behind the sterno-mastoid muscle. It may attain a large size, the\
overlying skin and cyst wall may be so thin as to be translucent, and it\
has been known to cause serious impairment of respiration through\
pressing on the trachea. In the axilla also the cystic tumour may attain\
a considerable size (Fig. 76); less frequent situations are the groin,\
and the floor of the mouth, where it constitutes one form of ranula.\
\
The nature of these swellings is to be recognised by their situation, by\
their having existed from infancy, and, if necessary, by drawing off\
some of the contents of the cyst through a fine needle. They are usually\
remarkably indolent, persisting often for a long term of years without\
change, and, like the haemangioma, they sometimes undergo spontaneous\
cicatrisation and cure. Sometimes the cystic tumour becomes infected and\
forms an abscess--another, although less desirable, method of cure.\
Those situated in the neck are most liable to suppurate, probably\
because of pyogenic organisms being brought to them by the lymphatics\
taking origin in the scalp, ear, or throat.\
\
If operative interference is called for, the cysts may be tapped and\
injected with iodine, or excised; the operation for removal may entail a\
considerable dissection amongst the deeper structures at the root of the\
neck, and should not be lightly undertaken; parts left behind may be\
induced to cicatrise by inserting a tube of radium and leaving it for a\
few days.\
\
Lymphangiomas are met with in the abdomen in the form of _omental\
cysts_.\
\
\
DISEASES OF LYMPH GLANDS\
\
#Lymphadenitis.#--Inflammation of lymph glands results from the advent\
of an irritant, usually bacterial or toxic, brought to the glands by the\
afferent lymph vessels. These vessels may share in the inflammation and\
be the seat of lymphangitis, or they may show no evidence of the passage\
of the noxa. It is exceptional for the irritant to reach the gland\
through the blood-stream.\
\
A strain or other form of trauma is sometimes blamed for the onset of\
lymphadenitis, especially in the glands of the groin (bubo), but it is\
usually possible to discover some source of pyogenic infection which is\
responsible for the mischief, or to obtain a history of some antecedent\
infection such as gonorrhoea. It is possible for gonococci to lie latent\
in the inguinal glands for long periods, and only give rise to\
lymphadenitis if the glands be subsequently subjected to injury. The\
glands most frequently affected are those in the neck, axilla, and\
groin.\
\
The characters of the lymphadenitis vary with the nature of the\
irritant. Sometimes it is mild and evanescent, as in the glandular\
enlargement in the neck which attends tonsillitis and other forms of\
sore throat. Sometimes it is more persistent, as in the enlargement\
that is associated with adenoids, hypertrophied tonsils, carious teeth,\
eczema of the scalp, and otorrhoea; and it is possible that this indolent\
enlargement predisposes to tuberculous infection. A similar enlargement\
is met with in the axilla in cases of chronic interstitial mastitis, and\
in the groin as a result of chronic irritation about the external\
genitals, such as balanitis.\
\
Sometimes the lymphadenitis is of an acute character, and the tendency\
is towards the formation of an abscess. This is illustrated in the\
axillary glands as a result of infected wounds of the fingers; in the\
femoral glands in infected wounds or purulent blisters on the foot; in\
the inguinal glands in gonorrhoea and soft sore; and in the cervical\
glands in the severer forms of sore throat associated with diphtheria\
and scarlet fever. The most acute suppurations result from infection\
with streptococci.\
\
Superficial glands, when inflamed and suppurating, become enlarged,\
tender, fixed, and matted to one another. In the glands of the groin the\
suppurative process is often remarkably sluggish; purulent foci form in\
the interior of individual glands, and some time may elapse before the\
pus erupts through their respective capsules. In the deeply placed\
cervical glands, especially in cases of streptococcal throat infections,\
the suppuration rapidly involves the surrounding cellular tissue, and\
the clinical features are those of an acute cellulitis and deeply seated\
abscess. When this is incised the necrosed glands may be found lying in\
the pus, and on bacteriological examination are found to be swarming\
with streptococci. In suppuration of the axillary glands the abscess may\
be quite superficial, or it may be deeply placed beneath the strong\
fascia and pectoral muscles, according to the group of glands involved.\
\
The _diagnosis_ of septic lymphadenitis is usually easy. The indolent\
enlargements are not always to be distinguished, however, from\
commencing tuberculous disease, except by the use of the tuberculin\
test, and by the fact that they usually disappear on removing the\
peripheral source of irritation.\
\
_Treatment._--The first indication is to discover and deal with the\
source of infection, and in the indolent forms of lymphadenitis this\
will usually be followed by recovery. In the acute forms following on\
pyogenic infection, the best results are obtained from the hyperaemic\
treatment carried out by means of suction bells. If suppuration is not\
thereby prevented, or if it has already taken place, each separate\
collection of pus is punctured with a narrow-bladed knife and the use of\
the suction bell is persevered with. If there is a large periglandular\
abscess, as is often the case, in the neck and axilla, the opening may\
require to be made by Hilton's method, and it may be necessary to insert\
a drainage-tube.\
\
[Illustration: FIG. 77.--Tuberculous Cervical Gland with abscess\
formation in subcutaneous cellular tissue, in a boy aet. 10.]\
\
#Tuberculous Disease of Glands.#--This is a disease of great frequency\
and importance. The tubercle bacilli usually gain access to the gland\
through the afferent lymph vessels, which convey them from some lesion\
of the surface within the area drained by them. Tuberculous infection\
may supervene in glands that are already enlarged as a result of chronic\
septic irritation. While any of the glands in the body may be affected,\
the disease is most often met with in the cervical groups which derive\
their lymph from the mouth, nose, throat, and ear.\
\
_The appearance of the glands on section_ varies with the stage of the\
disease. In the early stages the gland is enlarged, it may be to many\
times its natural size, is normal in appearance and consistence, and as\
there is no peri-adenitis it is easily shelled out from its\
surroundings. On microscopical examination, however, there is evidence\
of infection in the shape of bacilli and of characteristic giant and\
epithelioid cells. At a later stage, the gland tissue is studded with\
minute yellow foci which tend to enlarge and in time to become\
confluent, so that the whole gland is ultimately converted into a\
caseous mass. This caseous material is surrounded by the thickened\
capsule which, as a result of peri-adenitis, tends to become adherent to\
and fused with surrounding structures, and particularly with layers of\
fascia and with the walls of veins. The caseated tissue often remains\
unchanged for long periods; it may become calcified, but more frequently\
it breaks down and liquefies.\
\
#Tuberculous disease in the cervical glands# is a common accompaniment\
or sequel of adenoids, enlarged tonsils, carious teeth, pharyngitis,\
middle-ear disease, and conjunctivitis. These lesions afford the bacilli\
a chance of entry into the lymph vessels, in which they are carried to\
the glands, where they give rise to disease.\
\
The enlargement may affect only one gland, usually below the angle of\
the mandible, and remain confined to it, the gland reaching the size of\
a hazel-nut, and being ovoid, firm, and painless. More commonly the\
disease affects several glands, on one or on both sides of the neck.\
When the disease commences in the pre-auricular or submaxillary glands,\
it tends to spread to those along the carotid sheath: when the posterior\
auricular and occipital glands are first involved, the spread is to\
those along the posterior border of the sterno-mastoid. In many cases\
all the chains in front of, beneath, and behind this muscle are\
involved, the enlarged glands extending from the mastoid to the\
clavicle. They are at first discrete and movable, and may even vary in\
size from time to time; but with the addition of peri-adenitis they\
become fixed and matted together, forming lobulated or nodular masses\
(Fig. 78). They become adherent not only to one another, but also to the\
structures in their vicinity,--and notably to the internal jugular\
vein,--a point of importance in regard to their removal by operation.\
\
At any stage the disease may be arrested and the glands remain for long\
periods without further change. It is possible that the tuberculous\
tissue may undergo cicatrisation. More commonly suppuration ensues, and\
a cold abscess forms, but if there is a mixed infection, the pyogenic\
factor being usually derived from the throat, it may take on active\
features.\
\
[Illustration: FIG. 78.--Mass of Tuberculous Glands removed from Axilla\
(cf. Fig. 79).]\
\
The transition from the solid to the liquefied stage is attended with\
pain and tenderness in the gland, which at the same time becomes fixed\
and globular, and finally fluctuation can be elicited.\
\
If left to itself, the softened tubercle erupts through the capsule of\
the gland and infects the cellular tissue. The cervical fascia is\
perforated and a cold abscess, often much larger than the gland from\
which it took origin, forms between the fascia and the overlying skin.\
The further stages--reddening, undermining of skin and external rupture,\
with the formation of ulcers and sinuses--have been described with\
tuberculous abscess. The ulcers and sinuses persist indefinitely, or\
they heal and then break out again; sometimes the skin becomes infected,\
and a condition like lupus spreads over a considerable area. Spontaneous\
healing finally takes place after the caseous tubercle has been\
extruded; the resulting scars are extremely unsightly, being puckered or\
bridled, or hypertrophied like keloid.\
\
While the disease is most common in childhood and youth, it may be met\
with even in advanced life; and although often associated with impaired\
health and unhealthy surroundings, it may affect those who are\
apparently robust and are in affluent circumstances.\
\
_Diagnosis._--The chief importance lies in differentiating tuberculous\
disease from lympho-sarcoma and from lymphadenoma, and this is usually\
possible from the history and from the nature of the enlargement. Signs\
of liquefaction and suppuration support the diagnosis of tubercle. If\
any doubt remains, one of the glands should be removed and submitted to\
microscopical examination. Other forms of sarcoma, and the enlargement\
of an accessory thyreoid, are less likely to be confused with\
tuberculous glands. Calcified tuberculous glands give definite shadows\
with the X-rays.\
\
Enlargement of the cervical glands from secondary cancer may simulate\
tuberculosis, but is differentiated by its association with cancer in\
the mouth or throat, and by the characteristic, stone-like induration of\
epithelioma.\
\
The cold abscess which results from tuberculous glands is to be\
distinguished from that due to disease in the cervical spine,\
retro-pharyngeal abscess, as well as from congenital and other cystic\
swellings in the neck.\
\
_Prognosis._--Next to lupus, glandular disease is of all tuberculous\
lesions the least dangerous to life; but while it is the rule to recover\
from tuberculous disease of glands with or without an operation, it is\
unfortunately quite common for such persons to become the subjects of\
tuberculosis in other parts of the body at any subsequent period of\
life.\
\
_Treatment._--There is considerable difference of opinion regarding the\
treatment of glandular tuberculosis. Some authorities, impressed with\
the undoubted possibility of natural cure, are satisfied with promoting\
this by measures directed towards improving the general health, by the\
prolonged administration of tuberculin, and by repeated exposures to the\
X-rays and to sunlight. Others again, influenced by the risk of\
extension of the disease and by the destruction of tissue and\
disfigurement caused by breaking down of the tuberculous tissue and\
mixed infection, advocate the removal of the glands by operation.\
\
The conditions vary widely in different cases, and the treatment should\
be adapted to the individual requirements. If the disease remains\
confined to the glands originally infected and there are no signs of\
breaking down, "expectant measures" may be persevered with.\
\
[Illustration: FIG. 79.--Tuberculous Axillary Glands (cf. Fig. 78).]\
\
If, on the other hand, the disease exhibits aggressive tendencies, the\
question of operation should be considered. The undesirable results of\
the breaking down and liquefaction of the diseased gland may be avoided\
by the timely withdrawal of the fluid contents through a hollow needle.\
\
_The excision of tuberculous glands_ is often a difficult operation,\
because of the number and deep situation of the glands to be removed,\
and of the adhesions to surrounding structures. The skin incision must\
be sufficiently extensive to give access to the whole of the affected\
area, and to avoid disfigurement should, whenever possible, be made in\
the line of the natural creases of the skin. In exposing the glands the\
common facial and other venous trunks may require to be clamped and\
tied. Care must be taken not to injure the important nerves,\
particularly the accessory, the vagus, and the phrenic. The\
inframaxillary branches of the facial, the hypoglossal and its\
descending branches, and the motor branches of the deep cervical plexus,\
are also liable to be injured. The dissection is rendered easier and is\
attended with less risk of injury to the nerves, if the patient is\
placed in the sitting posture so as to empty the veins, and, instead of\
a knife, the conical scissors of Mayo are employed. When the glands are\
extensively affected on both sides of the neck, it is advisable to allow\
an interval to elapse rather than to operate on both sides at one\
sitting. (_Op. Surg._, p. 189.)\
\
If the tonsils are enlarged they should not be removed at the same time,\
as, by so doing, there is a risk of pyogenic infection from the throat\
being carried to the wound in the neck, but they should be removed,\
after an interval, to prevent relapse of disease in the glands.\
\
_When the skin is broken_ and caseous tuberculous tissue is exposed,\
healing is promoted by cutting away diseased skin, removing the\
granulation tissue with the spoon, scraping sinuses, and packing the\
cavity with iodoform worsted and treating it by the open method and\
secondary suture if necessary. Exposure to the sunshine on the seashore\
and to the X-rays is often beneficial in these cases.\
\
#Tuberculous disease in the axillary glands# may be a result of\
extension from those in the neck, from the mamma, ribs, or sternum, or\
more rarely from the upper extremity. We have seen it from an infected\
wound of a finger. In some cases no source of infection is discoverable.\
The individual glands attain a considerable size, and they fuse together\
to form a large tumour which fills up the axillary space. The disease\
progresses more rapidly than it does in the cervical glands, and almost\
always goes on to suppuration with the formation of sinuses.\
Conservative measures need not be considered, as the only satisfactory\
treatment is excision, and that without delay.\
\
#Tuberculous disease in the glands of the groin# is comparatively rare.\
We have chiefly observed it in the femoral glands as a result of\
inoculation tubercle on the toes or sole of the foot. The affected\
glands nearly always break down and suppurate, and after destroying the\
overlying skin give rise to fungating ulcers. The treatment consists in\
excising the glands and the affected skin. The dissection may be\
attended with troublesome haemorrhage from the numerous veins that\
converge towards the femoral trunk.\
\
Tuberculous disease in the _mesenteric_ and _bronchial glands_ is\
described with the surgery of regions.\
\
#Syphilitic Disease of Glands.#--Enlargement of lymph glands is a\
prominent feature of acquired syphilis, especially in the form of the\
indolent or bullet-bubo which accompanies the primary lesion, and the\
general enlargement of glands that occurs in secondary syphilis.\
Gummatous disease in glands is extremely rare; the affected gland\
rapidly enlarges to the size of a walnut, and may then persist for a\
long period without further change; if it breaks down, the overlying\
skin is destroyed and the caseated tissue of the gumma exposed.\
\
#Lymphadenoma.#--_Hodgkin's Disease_ (Pseudo-leukaemia of German\
authors).--This is a rare disease, the origin of which is as yet\
unknown, but analogy would suggest that it is due to infection with a\
slowly growing micro-organism. It is chiefly met with in young subjects,\
and is characterised by a painless enlargement of a particular group of\
glands, most commonly those in the cervical region (Fig. 80).\
\
[Illustration: FIG. 80.--Chronic Hodgkin's Disease in a boy aet. 11.]\
\
The glands are usually larger than in tuberculosis, and they remain\
longer discrete and movable; they are firm in consistence, and on\
section present a granular appearance due to overgrowth of the\
connective-tissue framework. In time the glandular masses may form\
enormous projecting tumours, the swelling being added to by lymphatic\
oedema of the overlying cellular tissue and skin.\
\
The enlargement spreads along the chain of glands to those above the\
clavicle, to those in the axilla, and to those of the opposite side\
(Fig. 81). Later, the glands in the groin become enlarged, and it is\
probable that the infection has spread from the neck along the\
mediastinal, bronchial, retro-peritoneal, and mesenteric glands, and has\
branched off to the iliac and inguinal groups.\
\
Two clinical types are recognised, one in which the disease progresses\
slowly and remains confined to the cervical glands for two or more\
years; the other, in which the disease is more rapidly disseminated and\
causes death in from twelve to eighteen months.\
\
[Illustration: FIG. 81.--Lymphadenoma (Hodgkin's Disease) affecting left\
side of neck and left axilla, in a woman aet. 44. Three years' duration.]\
\
In the acute form, the health suffers, there is fever, and the glands\
may vary in size with variations in the temperature; the blood presents\
the characters met with in secondary anaemia. The spleen, liver, testes,\
and mammae may be enlarged; the glandular swellings press on important\
structures, such as the trachea, oesophagus, or great veins, and symptoms\
referable to such pressure manifest themselves.\
\
_Diagnosis._--Considerable difficulty attends the diagnosis of\
lymphadenoma at an early stage. The negative results of tuberculin tests\
may assist in the differentiation from tuberculous disease, but the more\
certain means of excising one of the suspected glands and submitting it\
to microscopical examination should be had recourse to. The sections\
show proliferation of endothelial cells, the formation of numerous giant\
cells quite unlike those of tuberculosis and a progressive fibrosis.\
Lympho-sarcoma can usually be differentiated by the rapid assumption of\
the local features of malignant disease, and in a gland removed for\
examination, a predominance of small round cells with scanty protoplasm.\
The enlargement associated with leucocythaemia is differentiated by the\
characteristic changes in the blood.\
\
_Treatment._--In the acute form of lymphadenoma, treatment is of little\
avail. Arsenic may be given in full doses either by the mouth or by\
subcutaneous injection; the intravenous administration of neo-salvarsan\
may be tried. Exposure to the X-rays and to radium has been more\
successful than any other form of treatment. Excision of glands,\
although sometimes beneficial, seldom arrests the progress of the\
disease. The ease and rapidity with which large masses of glands may be\
shelled out is in remarkable contrast to what is observed in tuberculous\
disease. Surgical interference may give relief when important structures\
are being pressed upon--tracheotomy, for example, may be required where\
life is threatened by asphyxia.\
\
#Leucocythaemia.#--This is a disease of the blood and of the\
blood-forming organs, in which there is a great increase in the number,\
and an alteration of the character, of the leucocytes present in the\
blood. It may simulate lymphadenoma, because, in certain forms of the\
disease, the lymph glands, especially those in the neck, axilla, and\
groin, are greatly enlarged.\
\
\
TUMOURS OF LYMPH GLANDS\
\
#Primary Tumours.#--_Lympho-sarcoma_, which may be regarded as a sarcoma\
starting in a lymph gland, appears in the neck, axilla, or groin as a\
rapidly growing tumour consisting of one enlarged gland with numerous\
satellites. As the tumour increases in size, the sarcomatous tissue\
erupts through the capsule of the gland, and infiltrates the surrounding\
tissues, whereby it becomes fixed to these and to the skin.\
\
[Illustration: FIG. 82.--Lympho-Sarcoma removed from Groin. It will be\
observed that there is one large central parent tumour surrounded by\
satellites.]\
\
The prognosis is grave in the extreme, and the only hope is in early\
excision, followed by the use of radium and X-rays. We have observed a\
case of lympho-sarcoma above the clavicle, in which excision of all that\
was removable, followed by the insertion of a tube of radium for ten\
days, was followed by a disappearance of the disease over a period which\
extended to nearly five years, when death resulted from a tumour in the\
mediastinum. In a second case in which the growth was in the groin, the\
patient, a young man, remained well for over two years and was then lost\
sight of.\
\
#Secondary Tumours.#--Next to tuberculosis, _secondary cancer_ is the\
most common disease of lymph glands. In the neck it is met with in\
association with epithelioma of the lip, tongue, or fauces. The glands\
form tumours of variable size, and are often larger than the primary\
growth, the characters of which they reproduce. The glands are at first\
movable, but soon become fixed both to each other and to their\
surroundings; when fixed to the mandible they form a swelling of\
bone-like hardness; in time they soften, liquefy, and burst through the\
skin, forming foul, fungating ulcers. A similar condition is met with in\
the groin from epithelioma of the penis, scrotum, or vulva. In cancer of\
the breast, the infection of the axillary glands is an important\
complication.\
\
In _pigmented_ or _melanotic cancers_ of the skin, the glands are early\
infected and increase rapidly, so that, when the primary growth is still\
of small size--as, for example, on the sole of the foot--the femoral\
glands may already constitute large pigmented tumours.\
\
[Illustration: FIG. 83.--Cancerous Glands in Neck secondary to\
Epithelioma of Lip.\
\
(Mr. G. L. Chiene's case.)]\
\
The implication of the glands in other forms of cancer will be\
considered with regional surgery.\
\
_Secondary sarcoma_ is seldom met with in the lymph glands except when\
the primary growth is a lympho-sarcoma and is situated in the tonsil,\
thyreoid, or testicle.\
\
\
\
\
CHAPTER XVI\
\
THE NERVES\
\
\
Anatomy--INJURIES OF NERVES: Changes in nerves after division;\
    Repair and its modifications; Clinical features; _Primary and\
    secondary suture_--SUBCUTANEOUS INJURIES OF\
    NERVES--DISEASES: _Neuritis_; _Tumours_--Surgery of\
    the individual nerves: _Brachial neuralgia_; _Sciatica_;\
    _Trigeminal neuralgia_.\
\
#Anatomy.#--A nerve-trunk is made up of a variable number of bundles of\
nerve fibres surrounded and supported by a framework of connective\
tissue. The nerve fibres are chiefly of the medullated type, and they\
run without interruption from a nerve cell or _neuron_ in the brain or\
spinal medulla to their peripheral terminations in muscle, skin, and\
secretory glands.\
\
Each nerve fibre consists of a number of nerve fibrils collected into a\
central bundle--the axis cylinder--which is surrounded by an envelope,\
the neurolemma or sheath of Schwann. Between the neurolemma and the axis\
cylinder is the medullated sheath, composed of a fatty substance known\
as myelin. This medullated sheath is interrupted at the nodes of\
Ranvier, and in each internode is a nucleus lying between the myelin and\
the neurolemma. The axis cylinder is the essential conducting structure\
of the nerve, while the neurolemma and the myelin act as insulating\
agents. The axis cylinder depends for its nutrition on the central\
neuron with which it is connected, and from which it originally\
developed, and it degenerates if it is separated from its neuron.\
\
The connective-tissue framework of a nerve-trunk consists of the\
_perineurium_, or general sheath, which surrounds all the bundles; the\
_epineurium_, surrounding individual groups of bundles; and the\
_endoneurium_, a delicate connective tissue separating the individual\
nerve fibres. The blood vessels and lymphatics run in these\
connective-tissue sheaths.\
\
According to Head and his co-workers, Sherren and Rivers, the afferent\
fibres in the peripheral nerves can be divided into three systems:--\
\
1. Those which subserve _deep sensibility_ and conduct the impulses\
produced by pressure as well as those which enable the patient to\
recognise the position of a joint on passive movement (joint-sensation),\
and the kinaesthetic sense, which recognises that active contraction of\
the muscle is taking place (active muscle-sensation). The fibres of this\
system run with the motor nerves, and pass to muscles, tendons, and\
joints. Even division of both the ulnar and the median nerves above the\
wrist produces little loss of deep sensibility, unless the tendons are\
also cut through. The failure to recognise this form of sensibility has\
been largely responsible for the conflicting statements as to the\
sensory phenomena following operations for the repair of divided nerves.\
\
2. Those which subserve _protopathic_ sensibility--that is, are capable\
of responding to painful cutaneous stimuli and to the extremes of heat\
and cold. These also endow the hairs with sensibility to pain. They are\
the first to regenerate after division.\
\
3. Those which subserve _epicritic_ sensibility, the most highly\
specialised, capable of appreciating light touch, _e.g._ with a wisp of\
cotton wool, as a well-localised sensation, and the finer grades of\
temperature, called cool and warm (72 o-104 o F.), and of discriminating\
as separate the points of a pair of compasses 2 cms. apart. These are\
the last to regenerate.\
\
A nerve also exerts a trophic influence on the tissues in which it is\
distributed.\
\
The researches of Stoffel on the minute anatomy of the larger nerves,\
and the disposition in them of the bundles of nerve fibres supplying\
different groups of muscles, have opened up what promises to be a\
fruitful field of clinical investigation and therapeutics. He has shown\
that in the larger nerve-trunks the nerve bundles for special groups of\
muscles are not, as was formerly supposed, arranged irregularly and\
fortuitously, but that on the contrary the nerve fibres to a particular\
group of muscles have a typical and practically constant position within\
the nerve.\
\
In the large nerve-trunks of the limbs he has worked out the exact\
position of the bundles for the various groups of muscles, so that in a\
cross section of a particular nerve the component bundles can be\
labelled as confidently and accurately as can be the cortical areas in\
the brain. In the living subject, by using a fine needle-like electrode\
and a very weak galvanic current, he has been able to differentiate the\
nerve bundles for the various groups of muscles. In several cases of\
spastic paralysis he succeeded in picking out in the nerve-trunk of the\
affected limb the nerve bundles supplying the spastic muscles, and, by\
resecting portions of them, in relieving the spasm. In a case of spastic\
contracture of the pronator muscles of the forearm, for example, an\
incision is made along the line of the median nerve above the bend of\
the elbow. At the lateral side of the median nerve, where it lies in\
contact with the biceps muscle, is situated a well-defined and easily\
isolated bundle of fibres which supplies the pronator teres, the flexor\
carpi radialis, and the palmaris longus muscles. On incising the sheath\
of the nerve this bundle can be readily dissected up and its identity\
confirmed by stimulating it with a very weak galvanic current. An inch\
or more of the bundle is then resected.\
\
\
INJURIES OF NERVES\
\
Nerves are liable to be cut or torn across, bruised, compressed,\
stretched, or torn away from their connections with the spinal medulla.\
\
#Complete Division of a Mixed Nerve.#--Complete division is a common\
result of accidental wounds, especially above the wrist, where the\
ulnar, median, and radial nerves are frequently cut across, and in\
gun-shot injuries.\
\
_Changes in Structure and Function._--The mere interruption of the\
continuity of a nerve results in degeneration of its fibres, the myelin\
being broken up into droplets and absorbed, while the axis cylinders\
swell up, disintegrate, and finally disappear. Both the conducting and\
the insulating elements are thus lost. The degeneration in the central\
end of the divided nerve is usually limited to the immediate proximity\
of the lesion, and does not even involve all the nerve fibres. In the\
distal end, it extends throughout the entire peripheral distribution of\
the nerve, and appears to be due to the cutting off of the fibres from\
their trophic nerve cells in the spinal medulla. Immediate suturing of\
the ends does not affect the degeneration of the distal segment. The\
peripheral end undergoes complete degeneration in from six weeks to two\
months.\
\
The physiological effects of complete division are that the muscles\
supplied by the nerve are immediately paralysed, the area to which it\
furnishes the sole cutaneous supply becomes insensitive, and the other\
structures, including tendons, bones, and joints, lose sensation, and\
begin to atrophy from loss of the trophic influence.\
\
#Nerves divided in Amputation.#--In the case of nerves divided in an\
amputation, there is an active, although necessarily abortive, attempt\
at regeneration, which results in the formation of bulbous swellings at\
the cut ends of the nerves. When there has been suppuration, and\
especially if the nerves have been cut so as to be exposed in the wound,\
these bulbous swellings may attain an abnormal size, and are then known\
as "amputation" or "stump neuromas" (Fig. 84).\
\
When the nerves in a stump have not been cut sufficiently short, they\
may become involved in the cicatrix, and it may be necessary, on account\
of pain, to free them from their adhesions, and to resect enough of the\
terminal portions to prevent them again becoming adherent. When this is\
difficult, a portion may be resected from each of the nerve-trunks at a\
higher level; and if this fails to give relief, a fresh amputation may\
be performed. When there is agonising pain dependent upon an ascending\
neuritis, it may be necessary to resect the corresponding posterior\
nerve roots within the vertebral canal.\
\
[Illustration: FIG. 84.--Stump Neuromas of Sciatic Nerve, excised forty\
years after the original amputation by Mr. A. G. Miller.]\
\
#Other Injuries of Nerves.#--_Contusion_ of a nerve-trunk is attended\
with extravasation of blood into the connective-tissue sheaths, and is\
followed by degeneration of the contused nerve fibres. Function is\
usually restored, the conducting paths being re-established by the\
formation of new nerve fibres.\
\
When a nerve is _torn across_ or badly _crushed_--as, for example, by a\
fractured bone--the changes are similar to those in a divided nerve, and\
the ultimate result depends on the amount of separation between the ends\
and the possibility of the young axis cylinders bridging the gap.\
\
_Involvement of Nerves in Scar Tissue._--Pressure or traction may be\
exerted upon a nerve by contracting scar tissue, or a process of\
neuritis or perineuritis may be induced.\
\
When terminal filaments are involved in a scar, it is best to dissect\
out the scar, and along with it the ends of the nerves pressed upon.\
When a nerve-trunk, such as the sciatic, is involved in cicatricial\
tissue, the nerve must be exposed and freed from its surroundings\
(_neurolysis_), and then stretched so as to tear any adhesions that may\
be present above or below the part exposed. It may be advisable to\
displace the liberated nerve from its original position so as to\
minimise the risk of its incorporation in the scar of the original wound\
or in that resulting from the operation--for example, the radial nerve\
may be buried in the substance of the triceps, or it may be surrounded\
by a segment of vein or portion of fat-bearing fascia.\
\
_Injuries of nerves resulting from_ #gun-shot wounds# include: (1) those\
in which the nerve is directly damaged by the bullet, and (2) those in\
which the nerve-trunk is involved secondarily either by scar tissue in\
its vicinity or by callus following fracture of an adjacent bone. The\
primary injuries include contusion, partial or complete division, and\
perforation of the nerve-trunk. One of the most constant symptoms is the\
early occurrence of severe neuralgic pain, and this is usually\
associated with marked hyperaesthesia.\
\
#Regeneration.#--_Process of Repair when the Ends are in Contact._--_If\
the wound is aseptic_, and the ends of the divided nerve are sutured or\
remain in contact, they become united, and the conducting paths are\
re-established by a regeneration of nerve fibres. There is a difference\
of opinion as to the method of regeneration. The Wallerian doctrine is\
that the axis cylinders in the central end grow downwards, and enter the\
nerve sheaths of the distal portion, and continue growing until they\
reach the peripheral terminations in muscle and skin, and in course of\
time acquire a myelin sheath; the cells of the neurolemma multiply and\
form long chains in both ends of the nerve, and are believed to provide\
for the nourishment and support of the actively lengthening axis\
cylinders. Another view is that the formation of new axis cylinders is\
not confined to the central end, but that it goes on also in the\
peripheral segment, in which, however, the new axis cylinders do not\
attain maturity until continuity with the central end has been\
re-established.\
\
_If the wound becomes infected_ and suppuration occurs, the young nerve\
fibres are destroyed and efficient regeneration is prevented; the\
formation of scar tissue also may constitute a permanent obstacle to new\
nerve fibres bridging the gap.\
\
_When the ends are not in contact_, reunion of the divided nerve fibres\
does not take place whether the wound is infected or not. At the\
proximal end there forms a bulbous swelling, which becomes adherent to\
the scar tissue. It consists of branching axis cylinders running in all\
directions, these having failed to reach the distal end because of the\
extent of the gap. The peripheral end is completely degenerated, and is\
represented by a fibrous cord, the cut end of which is often slightly\
swollen or bulbous, and is also incorporated with the scar tissue of\
the wound.\
\
#Clinical Features.#--The symptoms resulting from division and non-union\
of a nerve-trunk necessarily vary with the functions of the affected\
nerve. The following description refers to a mixed sensori-motor trunk,\
such as the median or radial (musculo-spiral) nerve.\
\
_Sensory Phenomena._--Superficial touch is tested by means of a wisp of\
cotton wool stroked gently across the skin; the capacity of\
discriminating two points as separate, by a pair of blunt-pointed\
compasses; the sensation of pressure, by means of a pencil or other\
blunt object; of pain, by pricking or scratching with a needle; and of\
sensibility to heat and cold, by test-tubes containing water at\
different temperatures. While these tests are being carried out, the\
patient's eyes are screened off.\
\
After division of a nerve containing sensory fibres, there is an area of\
absolute cutaneous insensibility to touch (anaesthesia), to pain\
(analgesia), and to all degrees of temperature--_loss of protopathic\
sensibility_; surrounded by an area in which there is loss of sensation\
to light touch, inability to recognise minor differences of temperature\
(72 o-104 o F.), and to appreciate as separate impressions the contact of\
the two points of a compass--_loss of epicritic sensibility_ (Head and\
Sherren) (Figs. 91, 92).\
\
_Motor Phenomena._--There is immediate and complete loss of voluntary\
power in the muscles supplied by the divided nerve. The muscles rapidly\
waste, and within from three to five days, they cease to react to the\
faradic current. When tested with the galvanic current, it is found that\
a stronger current must be used to call forth contraction than in a\
healthy muscle, and the contraction appears first at the closing of the\
circuit when the anode is used as the testing electrode. The loss of\
excitability to the interrupted current, and the specific alteration in\
the type of contraction with the constant current, is known as the\
_reaction of degeneration_. After a few weeks all electric excitability\
is lost. The paralysed muscles undergo fatty degeneration, which attains\
its maximum three or four months after the division of the nerve.\
Further changes may take place, and result in the transformation of the\
muscle into fibrous tissue, which by undergoing shortening may cause\
deformity known as _paralytic contracture_.\
\
_Vaso-motor Phenomena._--In the majority of cases there is an initial\
rise in the temperature of the part (2 o to 3 o F.), with redness and\
increased vascularity. This is followed by a fall in the local\
temperature, which may amount to 8 o or 10 o F., the parts becoming pale\
and cold. Sometimes the hyperaemia resulting from vaso-motor paralysis is\
more persistent, and is associated with swelling of the parts from\
oedema--the so-called _angio-neurotic oedema_. The vascularity varies with\
external influences, and in cold weather the parts present a bluish\
appearance.\
\
_Trophic Phenomena._--Owing to the disappearance of the subcutaneous\
fat, the skin is smooth and thin, and may be abnormally dry. The hair is\
harsh, dry, and easily shed. The nails become brittle and furrowed, or\
thick and curved, and the ends of the fingers become club-shaped. Skin\
eruptions, especially in the form of blisters, occur, or there may be\
actual ulcers of the skin, especially in winter. In aggravated cases the\
tips of the fingers disappear from progressive ulceration, and in the\
sole of the foot a perforating ulcer may develop. Arthropathies are\
occasionally met with, the joints becoming the seat of a painless\
effusion or hydrops, which is followed by fibrous thickening of the\
capsular and other ligaments, and terminates in stiffness and fibrous\
ankylosis. In this way the fingers are seriously crippled and deformed.\
\
#Treatment of Divided Nerves.#--The treatment consists in approximating\
the divided ends of the nerve and placing them under the most favourable\
conditions for repair, and this should be done at the earliest possible\
opportunity. (_Op. Surg._, pp. 45, 46.)\
\
#Primary Suture.#--The reunion of a recently divided nerve is spoken of\
as primary suture, and for its success asepsis is essential. As the\
suturing of the ends of the nerve is extremely painful, an anaesthetic is\
required.\
\
When the wound is healed and while waiting for the restoration of\
function, measures are employed to maintain the nutrition of the damaged\
nerve and of the parts supplied by it. The limb is exercised, massaged,\
and douched, and protected from cold and other injurious influences. The\
nutrition of the paralysed muscles is further improved by electricity.\
The galvanic current is employed, using at first a mild current of not\
more than 5 milliamperes for about ten minutes, the current being made\
to flow downwards in the course of the nerve, with the positive\
electrode applied to the spine, and the negative over the affected nerve\
near its termination. It is an advantage to have a metronome in the\
circuit whereby the current is opened and closed automatically at\
intervals, so as to cause contraction of the muscles.\
\
_The results_ of primary suture, when it has been performed under\
favourable conditions, are usually satisfactory. In a series of cases\
investigated by Head and Sherren, the period between the operation and\
the first return of sensation averaged 65 days. According to Purves\
Stewart protopathic sensation commences to appear in about six weeks and\
is completely restored in six months; electric sensation and motor power\
reappear together in about six months, and restoration is complete in a\
year. When sensation returns, the area of insensibility to pain steadily\
diminishes and disappears; sensibility to extremes of temperature\
appears soon after; and last of all, after a considerable interval,\
there is simultaneous return of appreciation of light touch, moderate\
degrees of temperature, and the points of a compass.\
\
A clinical means of estimating how regeneration in a divided nerve is\
progressing has been described by Tinel. He found that a tingling\
sensation, similar to that experienced in the foot, when it is\
recovering from the "sleeping" condition induced by prolonged pressure\
on the sciatic nerve from sitting on a hard bench, can be elicited on\
percussing over _growing_ axis cylinders. Tapping over the proximal end\
of a _newly divided nerve_, _e.g._ the common peroneal behind the head\
of the fibula, produces no tingling, but when in about three weeks\
axis cylinders begin to grow in the proximal end-bulb, local tingling is\
induced by tapping there. The downward growth of the axis cylinders can\
be traced by tapping over the distal segment of the nerve, the tingling\
sensation being elicited as far down as the young axis cylinders have\
reached. When the regeneration of the axis cylinders is complete,\
tapping no longer causes tingling. It usually takes about one hundred\
days for this stage to be reached.\
\
Tinel's sign is present before voluntary movement, muscular tone, or the\
normal electrical reactions reappear.\
\
In cases of complete nerve paralysis that have not been operated upon,\
the tingling test is helpful in determining whether or not regeneration\
is taking place. Its detection may prevent an unnecessary operation\
being performed.\
\
Primary suture should not be attempted so long as the wound shows signs\
of infection, as it is almost certain to end in failure. The ends should\
be sutured, however, as soon as the wound is aseptic or has healed.\
\
#Secondary Suture.#--The term secondary suture is applied to the\
operation of stitching the ends of the divided nerve after the wound has\
healed.\
\
_Results of Secondary Suture._--When secondary suture has been performed\
under favourable conditions, the prognosis is good, but a longer time is\
required for restoration of function than after primary suture. Purves\
Stewart says protopathic sensation is sometimes observed much earlier\
than in primary suture, because partial regeneration of axis cylinders\
in the peripheral segment has already taken place. Sensation is\
recovered first, but it seldom returns before three or four months.\
There then follows an improvement or disappearance of any trophic\
disturbances that may be present. Recovery of motion may be deferred for\
long periods--rather because of the changes in the muscles than from\
want of conductivity in the nerve--and if the muscles have undergone\
complete degeneration, it may never take place at all. While waiting for\
recovery, every effort should be made to maintain the nutrition of the\
damaged nerve, and of the parts which it supplies.\
\
When suture is found to be impossible, recourse must be had to other\
methods, known as nerve bridging and nerve implantation.\
\
#Incomplete Division of a Mixed Nerve.#--The effects of partial division\
of a mixed nerve vary according to the destination of the nerve bundles\
that have been interrupted. Within their area of distribution the\
paralysis is as complete as if the whole trunk had been cut across. The\
uninjured nerve-bundles continue to transmit impulses with the result\
that there is a _dissociated paralysis_ within the distribution of the\
affected nerve, some muscles continuing to act and to respond normally\
to electric stimulation, while others behave as if the whole nerve-trunk\
had been severed.\
\
In addition to vasomotor and trophic changes, there is often severe pain\
of a burning kind (_causalgia_ or _thermalgia_) which comes on about a\
fortnight after the injury and causes intense and continuous suffering\
which may last for months. Paroxysms of pain may be excited by the\
slightest touch or by heat, and the patient usually learns for himself\
that the constant application of cold wet cloths allays the pain. The\
thermalgic area sweats profusely.\
\
Operative treatment is indicated where there is no sign of improvement\
within three months, when recovery is arrested before complete\
restoration of function is attained, or when thermalgic pain is\
excessive.\
\
#Subcutaneous Injuries of Nerves.#--Several varieties of subcutaneous\
injuries of nerves are met with. One of the best known is the\
compression paralysis of the nerves of the upper arm which results from\
sleeping with the arm resting on the back of a chair or the edge of a\
table--the so-called "drunkard's palsy"; and from the pressure of a\
crutch in the axilla--"crutch paralysis." In some of these injuries,\
notably "drunkard's palsy," the disability appears to be due not to\
damage of the nerve, but to overstretching of the extensors of the wrist\
and fingers (Jones). A similar form of paralysis is sometimes met with\
from the pressure of a tourniquet, from tight bandages or splints, from\
the pressure exerted by a dislocated bone or by excessive callus, and\
from hyper-extension of the arm during anaesthesia.\
\
In all these forms there is impaired sensation, rarely amounting to\
anaesthesia, marked muscular wasting, and diminution or loss of voluntary\
motor power, while--and this is a point of great importance--the normal\
electrical reactions are preserved. There may also develop trophic\
changes such as blisters, superficial ulcers, and clubbing of the tips\
of the fingers. The prognosis is usually favourable, as recovery is the\
rule within from one to three months. If, however, neuritis supervenes,\
the electrical reactions are altered, the muscles degenerate, and\
recovery may be retarded or may fail to take place.\
\
Injuries which act abruptly or instantaneously are illustrated in the\
crushing of a nerve by the sudden displacement of a sharp-edged fragment\
of bone, as may occur in comminuted fractures of the humerus. The\
symptoms include perversion or loss of sensation, motor paralysis, and\
atrophy of muscles, which show the reaction of degeneration from the\
eighth day onwards. The presence of the reaction of degeneration\
influences both the prognosis and the treatment, for it implies a lesion\
which is probably incapable of spontaneous recovery, and which can only\
be remedied by operation.\
\
The _treatment_ varies with the cause and nature of the lesion. When,\
for example, a displaced bone or a mass of callus is pressing upon the\
nerve, steps must be taken to relieve the pressure, by operation if\
necessary. When there is reason to believe that the nerve is severely\
crushed or torn across, it should be exposed by incision, and, after\
removal of the damaged ends, should be united by sutures. When it is\
impossible to make a definite diagnosis as to the state of the nerve, it\
is better to expose it by operation, and thus learn the exact state of\
affairs without delay; in the event of the nerve being torn, the ends\
should be united by sutures.\
\
#Dislocation of Nerves.#--This injury, which resembles the dislocation\
of tendons from their grooves, is seldom met with except in the ulnar\
nerve at the elbow, and is described with injuries of that nerve.\
\
\
DISEASES OF NERVES\
\
#Traumatic Neuritis.#--This consists in an overgrowth of the\
connective-tissue framework of a nerve, which causes irritation and\
pressure upon the nerve fibres, sometimes resulting in their\
degeneration. It may originate in connection with a wound in the\
vicinity of a nerve, as, for example, when the brachial nerves are\
involved in scar tissue subsequent to an operation for clearing out the\
axilla for cancer; or in contusion and compression of a nerve--for\
example, by the pressure of the head of the humerus in a dislocation of\
the shoulder. Some weeks or months after the injury, the patient\
complains of increasing hyperaesthesia and of neuralgic pains in the\
course of the nerve. The nerve is very sensitive to pressure, and, if\
superficial, may be felt to be swollen. The associated muscles are\
wasted and weak, and are subject to twitchings. There are also trophic\
disturbances. It is rare to have complete sensory and motor paralysis.\
The disease is commonest in the nerves of the upper extremity, and the\
hand may become crippled and useless.\
\
_Treatment._--Any constitutional condition which predisposes to\
neuritis, such as gout, diabetes, or syphilis, must receive appropriate\
treatment. The symptoms may be relieved by rest and by soothing\
applications, such as belladonna, ichthyol, or menthol, by the use of\
hot-air and electric baths, and in obstinate cases by blistering or by\
the application of Corrigan's button. When such treatment fails the\
nerve may be stretched, or, in the case of a purely sensory trunk, a\
portion may be excised. Local causes, such as involvement of the nerve\
in a scar or in adhesions, may afford indications for operative\
treatment.\
\
#Multiple Peripheral Neuritis.#--Although this disease mainly comes\
under the cognizance of the physician, it may be attended with phenomena\
which call for surgical interference. In this country it is commonly due\
to alcoholism, but it may result from diabetes or from chronic poisoning\
with lead or arsenic, or from bacterial infections and intoxications\
such as occur in diphtheria, gonorrhoea, syphilis, leprosy, typhoid,\
influenza, beri-beri, and many other diseases.\
\
It is, as a rule, widely distributed throughout the peripheral nerves,\
but the distribution frequently varies with the cause--the alcoholic\
form, for example, mainly affecting the legs, the diphtheritic form the\
soft palate and pharynx, and that associated with lead poisoning the\
forearms. The essential lesion is a degeneration of the conducting\
fibres of the affected nerves, and the prominent symptoms are the result\
of this. In alcoholic neuritis there is great tenderness of the muscles.\
When the legs are affected the patient may be unable to walk, and the\
toes may droop and the heel be drawn up, resulting in one variety of pes\
equino-varus. Pressure sores and perforating ulcer of the foot are the\
most important trophic phenomena.\
\
Apart from the medical _treatment_, measures must be taken to prevent\
deformity, especially when the legs are affected. The bedclothes are\
supported by a cage, and the foot maintained at right angles to the leg\
by sand-bags or splints. When the disease is subsiding, the nutrition of\
the damaged nerves and muscles should be maintained by massage, baths,\
passive movements, and the use of the galvanic current. When deformity\
has been allowed to take place, operative measures may be required for\
its correction.\
\
\
NEUROMA[5]\
\
[5] We have followed the classification adopted by Alexis Thomson in his\
work _On Neuroma, and Neuro-fibromatosis_ (Edinburgh: 1900).\
\
Neuroma is a clinical term applied to all tumours, irrespective of their\
structure, which have their seat in nerves.\
\
A tumour composed of newly formed nerve tissue is spoken of as a #true\
neuroma#; when ganglionic cells are present in addition to nerve fibres,\
the name _ganglionic neuroma_ is applied. These tumours are rare, and\
are chiefly met with in the main cords or abdominal plexuses of the\
sympathetic system of children or young adults. They are quite\
insensitive, and their removal is only called for if they cause pain or\
show signs of malignancy.\
\
A #false neuroma# is an overgrowth of the sheath of a nerve. This\
overgrowth may result in the formation of a circumscribed tumour, or may\
take the form of a diffuse fibromatosis.\
\
_The circumscribed or solitary tumour_ grows from the sheath of a nerve\
which is otherwise healthy, and it may be innocent or malignant.\
\
_The innocent_ form is usually fibrous or myxomatous, and is definitely\
encapsulated. It may become cystic as a result of haemorrhage or of\
myxomatous degeneration. It grows very slowly, is usually elliptical in\
shape, and the solid form is rarely larger than a hazel-nut. The nerve\
fibres may be spread out all round the tumour, or may run only on one\
side of it. When subcutaneous and related to the smaller unnamed\
cutaneous nerves, it is known as a _painful subcutaneous nodule_ or\
_tubercle_. It is chiefly met with about the ankle, and most often in\
women. It is remarkably sensitive, even gentle handling causing intense\
pain, which usually radiates to the periphery of the nerve affected.\
When related to a deeper, named nerve-trunk, it is known as a\
_trunk-neuroma_. It is usually less sensitive than the "subcutaneous\
nodule," and rarely gives rise to motor symptoms unless it involves the\
nerve roots where they pass through bony canals.\
\
A trunk-neuroma is recognised clinically by its position in the line of\
a nerve, by the fact that it is movable in the transverse axis of the\
nerve but not in its long axis, and by being unduly painful and\
sensitive.\
\
[Illustration: FIG. 85.--Amputation Stump of Upper Arm, showing bulbous\
thickening of the ends of the nerves, embedded in scar tissue at the\
apex of the stamp.]\
\
_Treatment._--If the tumour causes suffering it should be removed,\
preferably by shelling it out from the investing nerve sheath or\
capsule. In the subcutaneous nodule the nerve is rarely recognisable,\
and is usually sacrificed. When removal of the tumour is incomplete, a\
tube of radium should be inserted into the cavity, to prevent recurrence\
of the tumour in a malignant form.\
\
_The malignant neuroma_ is a sarcoma growing from the sheath of a nerve.\
It has the same characters and clinical features as the innocent\
variety, only it grows more rapidly, and by destroying the nerve fibres\
causes motor symptoms--jerkings followed by paralysis. The sarcoma tends\
to spread along the lymph spaces in the long axis of the nerve, as well\
as to implicate the surrounding tissues, and it is liable to give rise\
to secondary growths. The malignant neuroma is met with chiefly in the\
sciatic and other large nerves of the limbs.\
\
The _treatment_ is conducted on the same lines as sarcoma in other\
situations; the insertion of a tube of radium after removal of the\
tumour diminishes the tendency to recurrence; a portion of the\
nerve-trunk being sacrificed, means must be taken to bridge the gap. In\
inoperable cases it may be possible to relieve pain by excising a\
portion of the nerve above the tumour, or, when this is impracticable,\
by resecting the posterior nerve roots and their ganglia within the\
vertebral canal.\
\
The so-called _amputation neuroma_ has already been referred to (p. 344).\
\
_Diffuse or Generalised Neuro-Fibromatosis--Recklinghausen's\
Disease._--These terms are now used to include what were formerly known\
as "multiple neuromata," as well as certain other overgrowths related to\
nerves. The essential lesion is an overgrowth of the endoneural\
connective tissue throughout the nerves of both the cerebro-spinal and\
sympathetic systems. The nerves are diffusely and unequally thickened,\
so that small twigs may become enlarged to the size of the median, while\
at irregular intervals along their course the connective-tissue\
overgrowth is exaggerated so as to form tumour-like swellings similar to\
the trunk-neuroma already described. The tumours, which vary greatly in\
size and number--as many as a thousand have been counted in one\
case--are enclosed in a capsule derived from the perineurium. The\
fibromatosis may also affect the cranial nerves, the ganglia on the\
posterior nerve roots, the nerves within the vertebral canal, and the\
sympathetic nerves and ganglia, as well as the continuations of the\
motor nerves within the muscles. The nerve fibres, although mechanically\
displaced and dissociated by the overgrown endoneurium, undergo no\
structural change except when compressed in passing through a bony\
canal.\
\
The disease probably originates before birth, although it may not make\
its appearance till adolescence or even till adult life. It is sometimes\
met with in several members of one family. It is recognised clinically\
by the presence of multiple tumours in the course of the nerves, and\
sometimes by palpable enlargement of the superficial nerve-trunks\
(Fig. 86). The tumours resemble the solitary trunk-neuroma, are usually\
quite insensitive, and many of them are unknown to the patient. As a\
result of injury or other exciting cause, however, one or other tumour\
may increase in size and become extremely sensitive; the pain is then\
agonising; it is increased by handling, and interferes with sleep. In\
these conditions, a malignant transformation of the fibroma into sarcoma\
is to be suspected. Motor disturbances are exceptional, unless in the\
case of tumours within the vertebral canal, which press on the spinal\
medulla and cause paraplegia.\
\
[Illustration: FIG. 86.--Diffuse enlargement of Nerves in generalised\
Neuro-fibromatosis.\
\
(After R. W. Smith.)]\
\
Neuro-fibromatosis is frequently accompanied by _pigmentation of the\
skin_ in the form of brown spots or patches scattered over the trunk.\
\
The disease is often stationary for long periods. In progressive cases\
the patient becomes exhausted, and usually dies of some intercurrent\
affection, particularly phthisis. The treatment is restricted to\
relieving symptoms and complications; removal of one of the tumours is\
to be strongly deprecated.\
\
In a considerable proportion of cases one of the multiple tumours takes\
on the characters of a malignant growth ("secondary malignant neuroma,"\
Garre). This malignant transformation may follow upon injury, or on an\
unsuccessful attempt to remove the tumour. The features are those of a\
rapidly growing sarcoma involving a nerve-trunk, with agonising pain\
and muscular cramps, followed by paralysis from destruction of the\
nerve fibres. The removal of the tumour is usually followed by\
recurrence, so that high amputation is the only treatment to be\
recommended. Metastasis to internal organs is exceptional.\
\
[Illustration: FIG. 87.--Plexiform Neuroma of small Sciatic Nerve, from\
a girl aet. 16.\
\
(Mr. Annandale's case.)]\
\
There are other types of neuro-fibromatosis which require brief mention.\
\
_The plexiform neuroma_ (Fig. 87) is a fibromatosis confined to the\
distribution of one or more contiguous nerves or of a plexus of nerves,\
and it may occur either by itself or along with multiple tumours of the\
nerve-trunks and with pigmentation of the skin. The clinical features\
are those of an ill-defined swelling composed of a number of tortuous,\
convoluted cords, lying in a loose areolar tissue and freely movable on\
one another. It is rarely the seat of pain or tenderness. It most often\
appears in the early years of life, sometimes in relation to a pigmented\
or hairy mole. It is of slow growth, may remain stationary for long\
periods, and has little or no tendency to become malignant. It is\
usually subcutaneous, and is frequently situated on the head or neck in\
the distribution of the trigeminal or superficial cervical nerves. There\
is no necessity for its removal, but this may be indicated because of\
disfigurement, especially on the face or scalp or because its bulk\
interferes with function. When involving the ophthalmic division of the\
trigeminus, for example, it may cause enlargement of the upper lid and\
proptosis, with danger to the function of the globe. The results of\
excision are usually satisfactory, even if the removal is not complete.\
\
[Illustration: FIG. 88.--Multiple Neuro-fibromas of Skin (Molluscum\
fibrosum, or Recklinghausen's disease).]\
\
_The cutaneous neuro-fibroma_ or _molluscum fibrosum_ has been shown by\
Recklinghausen to be a soft fibroma related to the terminal filaments of\
one of the cutaneous nerves (Fig. 88). The disease appears in the form\
of multiple, soft, projecting tumours, scattered all over the body,\
except the palms of the hands and soles of the feet. The tumours are of\
all sizes, some being no larger than a pin's head, whilst many are as\
big as a filbert and a few even larger. Many are sessile and others are\
distinctly pedunculated, but all are covered with skin. They are mobile,\
soft to the touch, and of the consistence of firm fat. In exceptional\
cases one of the skin tumours may attain an enormous size and cause a\
hideous deformity, hanging down by its own weight in lobulated or folded\
masses (pachy-dermatocele). The treatment consists in removing the\
larger swellings. In some cases molluscum fibrosum is associated with\
pigmentation of the skin and with multiple tumours of the nerve-trunks.\
The small multiple tumours rarely call for interference.\
\
[Illustration: FIG. 89.--Elephantiasis Neuromatosa in a woman aet. 28]\
\
_Elephantiasis neuromatosa_ is the name applied by Virchow to a\
condition in which a limb is swollen and misshapen as a result of the\
extension of a neuro-fibromatosis to the skin and subcutaneous cellular\
tissue of the extremity as a whole (Fig. 89). It usually begins in early\
life without apparent cause, and it may be associated with multiple\
tumours of the nerve-trunks. The inconvenience caused by the bulk and\
weight of the limb may justify its removal.\
\
\
SURGERY OF THE INDIVIDUAL NERVES[6]\
\
[6] We desire here to acknowledge our indebtedness to Mr. James\
Sherren's work on _Injuries of Nerves and their Treatment_.\
\
#The Brachial Plexus.#--Lesions of the brachial plexus may be divided\
into those above the clavicle and those below that bone.\
\
In the #supra-clavicular injuries#, the violence applied to the head or\
shoulder causes over-stretching of the anterior branches (primary\
divisions) of the cervical nerves, the fifth, or the fifth and sixth\
being those most liable to suffer. Sometimes the traction is exerted\
upon the plexus from below, as when a man in falling from a height\
endeavours to save himself by clutching at some projection, and the\
lesion then mainly affects the first dorsal nerve. There is tearing of\
the nerve sheaths, with haemorrhage, but in severe cases partial or\
complete severance of nerve fibres may occur and these give way at\
different levels. During the healing process an excess of fibrous tissue\
is formed, which may interfere with regeneration.\
\
_Post-anaesthetic paralysis_ occurs in patients in whom, during the\
course of an operation, the arm is abducted and rotated laterally or\
extended above the head, causing over-stretching of the plexus,\
especially of the fifth, or fifth and sixth, anterior branches.\
\
A _cervical rib_ may damage the plexus by direct pressure, the part\
usually affected being the medial cord, which is made up of fibres from\
the eighth cervical and first dorsal nerves.\
\
When a lesion of the plexus complicates a _fracture of the clavicle_,\
the nerve injury is due, not to pressure on or laceration of the nerves\
by fragments of bone, but to the violence causing the fracture, and this\
is usually applied to the point of the shoulder.\
\
Penetrating _wounds_, apart from those met with in military practice,\
are rare.\
\
In the #infra-clavicular injuries#, the lesion most often results from\
the pressure of the dislocated head of the humerus; occasionally from\
attempts made to reduce the dislocation by the heel-in-the-axilla\
method, or from fracture of the upper end of the humerus or of the neck\
of the scapula. The whole plexus may suffer, but more frequently the\
medial cord is alone implicated.\
\
_Clinical Features._--Three types of lesion result from indirect\
violence: the whole plexus; the upper-arm type; and the lower-arm type.\
\
_When the whole plexus is involved_, sensibility is lost over the entire\
forearm and hand and over the lateral surface of the arm in its distal\
two-thirds. All the muscles of the arm, forearm, and hand are paralysed,\
and, as a rule, also the pectorals and spinati, but the rhomboids and\
serratus anterior escape. There is paralysis of the sympathetic fibres\
to the eye and orbit, with narrowing of the palpebral fissure, recession\
of the globe, and the pupil is slow to dilate when shaded from the\
light.\
\
The _upper-arm type_--Erb-Duchenne paralysis--is that most frequently\
met with, and it is due to a lesion of the fifth anterior branch, or, it\
may be, also of the sixth. The position of the upper limb is typical:\
the arm and forearm hang close to the side, with the forearm extended\
and pronated; the deltoid, spinati, biceps, brachialis, and supinators\
are paralysed, and in some cases the radial extensors of the wrist and\
the pronator teres are also affected. The patient is unable to supinate\
the forearm or to abduct the arm, and in most cases to flex the forearm.\
He may, however, regain some power of flexing the forearm when it is\
fully pronated, the extensors of the wrist becoming feeble flexors of\
the elbow. There is, as a rule, no loss of sensibility, but complaint\
may be made of tickling and of pins-and-needles over the lateral aspect\
of the arm. The abnormal position of the limb may persist although the\
muscles regain the power of voluntary movement, and as the condition\
frequently follows a fall on the shoulder, great care is necessary in\
diagnosis, as the condition is apt to be attributed to an injury to the\
axillary (circumflex) nerve.\
\
The _lower-arm type_ of paralysis, associated with the name of Klumpke,\
is usually due to over-stretching of the plexus, and especially affects\
the anterior branch of the first dorsal nerve. In typical cases all the\
intrinsic muscles of the hand are affected, and the hand assumes the\
claw shape. Sensibility is usually altered over the medial side of the\
arm and forearm, and there is paralysis of the sympathetic.\
\
_Infra-clavicular injuries_, as already stated, are most often produced\
by a sub-coracoid dislocation of the humerus; the medial cord is that\
most frequently injured, and the muscles paralysed are those supplied by\
the ulnar nerve, with, in addition, those intrinsic muscles of the hand\
supplied by the median. Sensibility is affected over the medial surface\
of the forearm and ulnar area of the hand. Injury of the lateral and\
posterior cords is very rare.\
\
_Treatment_ is carried out on the lines already laid down for nerve\
injuries in general. It is impossible to diagnose between complete and\
incomplete rupture of the nerve cords, until sufficient time has elapsed\
to allow of the establishment of the reaction of degeneration. If this\
is present at the end of fourteen days, operation should not be delayed.\
Access to the cords of the plexus is obtained by a dissection similar to\
that employed for the subclavian artery, and the nerves are sought for\
as they emerge from under cover of the scalenus anterior, and are then\
traced until the seat of injury is found. In the case of the first\
dorsal nerve, it may be necessary temporarily to resect the clavicle.\
The usual after-treatment must be persisted in until recovery ensues,\
and care must be taken that the paralysed muscles do not become\
over-stretched. The prognosis is less favourable in the supra-clavicular\
lesions than in those below the clavicle, which nearly always recover\
without surgical intervention.\
\
In the _brachial birth-paralysis_ met with in infants, the lesion is due\
to over-stretching of the plexus, and is nearly always of the\
Erb-Duchenne type. The injury is usually unilateral, it occurs with\
almost equal frequency in breech and in vertex presentations, and the\
left arm is more often affected than the right. The lesion is seldom\
recognised at birth. The first symptom noticed is tenderness in the\
supra-clavicular region, the child crying when this part is touched or\
the arm is moved. The attitude may be that of the Erb-Duchenne type, or\
the whole of the muscles of the upper limb may be flaccid, and the arm\
hangs powerless. A considerable proportion of the cases recover\
spontaneously. The arm is to be kept at rest, with the affected muscles\
relaxed, and, as soon as tenderness has disappeared, daily massage and\
passive movements are employed. The reaction of degeneration can rarely\
be satisfactorily tested before the child is three months old, but if it\
is present, an operation should be performed. After operation, the\
shoulder should be elevated so that no traction is exerted on the\
affected cords.\
\
#The long thoracic nerve# (nerve of Bell), which supplies the serratus\
anterior, is rarely injured. In those whose occupation entails carrying\
weights upon the shoulder it may be contused, and the resulting\
paralysis of the serratus is usually combined with paralysis of the\
lower part of the trapezius, the branches from the third and fourth\
cervical nerves which supply this muscle also being exposed to pressure\
as they pass across the root of the neck. There is complaint of pain\
above the clavicle, and winging of the scapula; the patient is unable to\
raise the arm in front of the body above the level of the shoulder or to\
perform any forward pushing movements; on attempting either of these the\
winging of the scapula is at once increased. If the scapula is compared\
with that on the sound side, it is seen that, in addition to the lower\
angle being more prominent, the spine is more horizontal and the lower\
angle nearer the middle line. The majority of these cases recover if the\
limb is placed at absolute rest, the elbow supported, and massage and\
galvanism persevered with. If the paralysis persists, the sterno-costal\
portion of the pectoralis major may be transplanted to the lower angle\
of the scapula.\
\
The long thoracic nerve may be cut across while clearing out the axilla\
in operating for cancer of the breast. The displacement of the scapula\
is not so marked as in the preceding type, and the patient is able to\
perform pushing movements below the level of the shoulder. If the\
reaction of degeneration develops, an operation may be performed, the\
ends of the nerve being sutured, or the distal end grafted into the\
posterior cord of the brachial plexus.\
\
#The Axillary (Circumflex) Nerve.#--In the majority of cases in which\
paralysis of the deltoid follows upon an injury of the shoulder, it is\
due to a lesion of the fifth cervical nerve, as has already been\
described in injuries of the brachial plexus. The axillary nerve itself\
as it passes round the neck of the humerus is most liable to be injured\
from the pressure of a crutch, or of the head of the humerus in\
sub-glenoid dislocation, or in fracture of the neck of the scapula or of\
the humerus. In miners, who work for long periods lying on the side, the\
muscle may be paralysed by direct pressure on the terminal filaments of\
the nerve, and the nerve may also be involved as a result of disease in\
the sub-deltoid bursa.\
\
The deltoid is wasted, and the acromion unduly prominent. In recent\
cases paralysis of the muscle is easily detected. In cases of long\
standing it is not so simple, because other muscles, the spinati, the\
clavicular fibres of the pectoral and the serratus, take its place and\
elevate the arm; there is always loss of sensation on the lateral aspect\
of the shoulder. There is rarely any call for operative treatment, as\
the paralysis is usually compensated for by other muscles.\
\
When the _supra-scapular nerve_ is contused or stretched in injuries of\
the shoulder, the spinati muscles are paralysed and wasted, the spine of\
the scapula is unduly prominent, and there is impairment in the power of\
abducting the arm and rotating it laterally.\
\
The _musculo-cutaneous nerve_ is very rarely injured; when cut across,\
there is paralysis of the coraco-brachialis, biceps, and part of the\
brachialis, but no movements are abolished, the forearm being flexed, in\
the pronated position, by the brachio-radialis and long radial extensor\
of the wrist; in the supinated position, by that portion of the\
brachialis supplied by the radial nerve. Supination is feebly performed\
by the supinator muscle. Protopathic and epicritic sensibility are lost\
over the radial side of the forearm.\
\
#Radial (Musculo-Spiral) Nerve.#--From its anatomical relationships this\
trunk is more exposed to injury than any other nerve in the body. It is\
frequently compressed against the humerus in sleeping with the arm\
resting on the back of a chair, especially in the deep sleep of\
alcoholic intoxication (drunkard's palsy). It may be pressed upon by a\
crutch in the axilla, by the dislocated head of the humerus, or by\
violent compression of the arm, as when an elastic tourniquet is applied\
too tightly. The most serious and permanent injuries of this nerve are\
associated with fractures of the humerus, especially those from direct\
violence attended with comminution of the bone. The nerve may be crushed\
or torn by one of the fragments at the time of the injury, or at a later\
period may be compressed by callus.\
\
_Clinical Features._--Immediately after the injury it is impossible to\
tell whether the nerve is torn across or merely compressed. The patient\
may complain of numbness and tingling in the distribution of the\
superficial branch of the nerve, but it is a striking fact, that so long\
as the nerve is divided below the level at which it gives off the dorsal\
cutaneous nerve of the forearm (external cutaneous branch), there is no\
loss of sensation. When it is divided above the origin of the dorsal\
cutaneous branch, or when the dorsal branch of the musculo-cutaneous\
nerve is also divided, there is a loss of sensibility on the dorsum\
of the hand.\
\
The motor symptoms predominate, the muscles affected being the extensors\
of the wrist and fingers, and the supinators. There is a characteristic\
"drop-wrist"; the wrist is flexed and pronated, and the patient is\
unable to dorsiflex the wrist or fingers (Fig. 90). If the hand and\
proximal phalanges are supported, the second and third phalanges may be\
partly extended by the interossei and lumbricals. There is also\
considerable impairment of power in the muscles which antagonise those\
that are paralysed, so that the grasp of the hand is feeble, and the\
patient almost loses the use of it; in some cases this would appear to\
be due to the median nerve having been injured at the same time.\
\
[Illustration: FIG. 90.--Drop-wrist following Fracture of Shaft of\
Humerus.]\
\
If the lesion is high up, as it is, for example, in crutch paralysis,\
the triceps and anconeus may also suffer.\
\
_Treatment._--The slighter forms of injury by compression recover under\
massage, douching, and electricity. If there is drop-wrist, the hand and\
forearm are placed on a palmar splint, with the hand dorsiflexed to\
nearly a right angle, and this position is maintained until voluntary\
dorsiflexion at the wrist returns to the normal. Recovery is sometimes\
delayed for several months.\
\
In the more severe injuries associated with fracture of the humerus and\
attended with the reaction of degeneration, it is necessary to cut down\
upon the nerve and free it from the pressure of a fragment of bone or\
from callus or adhesions. If the nerve is torn across, the ends must be\
sutured, and if this is impossible owing to loss of tissue, the gap may\
be bridged by a graft taken from the superficial branch of the radial\
nerve, or the ends may be implanted into the median.\
\
Finally, in cases in which the paralysis is permanent and incurable, the\
disability may be relieved by operation. A fascial graft can be employed\
to act as a ligament permanently extending the wrist; it is attached to\
the third and fourth metacarpal bones distally and to the radius or ulna\
proximally. The flexor carpi radialis can then be joined up with the\
extensor digitorum communis by passing its tendon through an aperture in\
the interosseous membrane, or better still, through the pronator\
quadratus, as there is less likelihood of the formation of adhesions\
when the tendon passes through muscle than through interosseous\
membrane. The palmaris longus is anastomosed with the abductor pollicis\
longus (extensor ossis metacarpi pollicis), thus securing a fair amount\
of abduction of the thumb. The flexor carpi ulnaris may also be\
anastomosed with the common extensor of the fingers. The extensors of\
the wrist may be shortened, so as to place the hand in the position of\
dorsal flexion, and thus improve the attitude and grasp of the hand.\
\
_The superficial branch of the radial_ (radial nerve) _and the deep\
branch_ (posterior interosseous), apart from suffering in lesions of the\
radial, are liable to be contused or torn is dislocation of the head of\
the radius, and in fracture of the neck of the bone. The deep branch may\
be divided as it passes through the supinator in operations on old\
fractures and dislocations in the region of the elbow. Division of the\
superficial branch in the upper two-thirds of the forearm produces no\
loss of sensibility; division in the lower third after the nerve has\
become associated with branches from the musculo-cutaneous is followed\
by a loss of sensibility on the radial side of the hand and thumb. Wounds\
on the dorsal surface of the wrist and forearm are often followed by\
loss of sensibility over a larger area, because the musculo-cutaneous\
nerve is divided as well, and some of the fibres of the lower lateral\
cutaneous branch of the radial.\
\
[Illustration: FIG. 91.--To illustrate the Loss of Sensation produced by\
Division of the Median Nerve. The area of complete cutaneous\
insensibility is shaded black. The parts insensitive to light touch and\
to intermediate degrees of temperature are enclosed within the dotted\
line.\
\
(After Head and Sherren.)]\
\
#The Median Nerve# is most frequently injured in wounds made by broken\
glass in the region of the wrist. It may also be injured in fractures of\
the lower end of the humerus, in fractures of both bones of the forearm,\
and as a result of pressure by splints. After _division at the elbow_,\
there is impairment of mobility which affects the thumb, and to a less\
extent the index finger: the terminal phalanx of the thumb cannot be\
flexed owing to the paralysis of the flexor pollicis longus, and the\
index can only be flexed at its metacarpo-phalangeal joint by the\
interosseous muscles attached to it. Pronation of the forearm is feeble,\
and is completed by the weight of the hand. After _division at the\
wrist_, the abductor-opponens group of muscles and the two lateral\
lumbricals only are affected; the abduction of the thumb can be feebly\
imitated by the short extensor and the long abductor (ext. ossis\
metacarpi pollicis), while opposition may be simulated by contraction of\
the long flexor and the short abductor of the thumb; the paralysis of\
the two medial lumbricals produces no symptoms that can be recognised.\
It is important to remember that when the median nerve is divided at the\
wrist, deep touch can be appreciated over the whole of the area\
supplied by the nerve; the injury, therefore, is liable to be over\
looked. If, however, the tendons are divided as well as the nerve, there\
is insensibility to deep touch. The areas of epicritic and of\
protopathic insensibility are illustrated in Fig. 91. The division of\
the nerve at the elbow, or even at the axilla, does not increase the\
extent of the loss of epicritic or protopathic sensibility, but usually\
affects deep sensibility.\
\
[Illustration: FIG. 92.--To illustrate Loss of Sensation produced by\
complete Division of Ulnar Nerve. Loss of all forms of cutaneous\
sensibility is represented by the shaded area. The parts insensitive to\
light touch and to intermediate degrees of heat and cold are enclosed\
within the dotted line.\
\
(Head and Sherren.)]\
\
#The Ulnar Nerve.#--The most common injury of this nerve is its division\
in transverse accidental wounds just above the wrist. In the arm it may\
be contused, along with the radial, in crutch paralysis; in the region\
of the elbow it may be injured in fractures or dislocations, or it may\
be accidentally divided in the operation for excising the elbow-joint.\
\
When it is injured _at or above the elbow_, there is paralysis of the\
flexor carpi ulnaris, the ulnar half of the flexor digitorum profundus,\
all the interossei, the two medial lumbricals, and the adductors of the\
thumb. The hand assumes a characteristic attitude: the index and middle\
fingers are extended at the metacarpo-phalangeal joints owing to\
paralysis of the interosseous muscles attached to them; the little and\
ring fingers are hyper-extended at these joints in consequence of the\
paralysis of the lumbricals; all the fingers are flexed at the\
inter-phalangeal joints, the flexion being most marked in the little and\
ring fingers--claw-hand or _main en griffe_. On flexing the wrist, the\
hand is tilted to the radial side, but the paralysis of the flexor carpi\
ulnaris is often compensated for by the action of the palmaris longus.\
The little and ring fingers can be flexed to a slight degree by the\
slips of the flexor sublimis attached to them and supplied by the median\
nerve; flexion of the terminal phalanx of the little finger is almost\
impossible. Adduction and abduction movements of the fingers are lost.\
Adduction of the thumb is carried out, not by the paralysed adductor\
pollicis, but the movement may be simulated by the long flexor and\
extensor muscles of the thumb. Epicritic sensibility is lost over the\
little finger, the ulnar half of the ring finger, and that part of the\
palm and dorsum of the hand to the ulnar side of a line drawn\
longitudinally through the ring finger and continued upwards.\
Protopathic sensibility is lost over an area which varies in different\
cases. Deep sensibility is usually lost over an area almost as extensive\
as that of protopathic insensibility.\
\
When the nerve is _divided at the wrist_, the adjacent tendons are also\
frequently severed. If divided below the point at which its dorsal\
branch is given off, the sensory paralysis is much less marked, and the\
injury is therefore liable to be overlooked until the wasting of muscles\
and typical _main en griffe_ ensue. The loss of sensibility after\
division of the nerve before the dorsal branch is given off resembles\
that after division at the elbow, except that in uncomplicated cases\
deep sensibility is usually retained. If the tendons are divided as\
well, however, deep touch is also lost.\
\
Care must be taken in all these injuries to prevent deformity; a splint\
must be worn, at least during the night, until the muscles regain their\
power of voluntary movement, and then exercises should be instituted.\
\
#Dislocation of the ulnar nerve# at the elbow results from sudden and\
violent flexion of the joint, the muscular effort causing stretching or\
laceration of the fascia that holds the nerve in its groove; it is\
predisposed to if the groove is shallow as a result of imperfect\
development of the medial condyle of the humerus, and by cubitus valgus.\
\
The nerve slips forward, and may be felt lying on the medial aspect of\
the condyle. It may retain this position, or it may slip backwards and\
forwards with the movements of the arm. The symptoms at the time of the\
displacement are some disability at the elbow, and pain and tingling\
along the nerve, which are exaggerated by movement and by pressure. The\
symptoms may subside altogether, or a neuritis may develop, with severe\
pain shooting up the nerve.\
\
The dislocated nerve is easily replaced, but is difficult to retain in\
position. In recent cases the arm may be placed in the extended position\
with a pad over the condyle, care being taken to avoid pressure on the\
nerve. Failing relief, it is better to make a bed for the nerve by\
dividing the deep fascia behind the medial condyle and to stitch the\
edges of the fascia over the nerve. This operation has been successful\
in all the recorded cases.\
\
#The Sciatic Nerve.#--When this nerve is compressed, as by sitting on a\
fence, there is tingling and powerlessness in the limb as a whole, known\
as "sleeping" of the limb, but these phenomena are evanescent. _Injuries\
to the great sciatic nerve_ are rare except in war. Partial division is\
more common than complete, and it is noteworthy that the fibres destined\
for the peroneal nerve are more often and more severely injured than\
those for the tibial (internal popliteal). After complete division, all\
the muscles of the leg are paralysed; if the section is in the upper\
part of the thigh, the hamstrings are also paralysed. The limb is at\
first quite powerless, but the patient usually recovers sufficiently to\
be able to walk with a little support, and although the hamstrings are\
paralysed the knee can be flexed by the sartorius and gracilis. The\
chief feature is drop-foot. There is also loss of sensation below the\
knee except along the course of the long saphenous nerve on the medial\
side of the leg and foot. Sensibility to deep touch is only lost over a\
comparatively small area on the dorsum of the foot.\
\
#The Common Peroneal (external popliteal) nerve# is exposed to injury\
where it winds round the neck of the fibula, because it is superficial\
and lies against the unyielding bone. It may be compressed by a\
tourniquet, or it may be bruised or torn in fractures of the upper end\
of the bone. It has been divided in accidental wounds,--by a scythe, for\
example,--in incising for cellulitis, and in performing subcutaneous\
tenotomy of the biceps tendon. Cases have been observed of paralysis of\
the nerve as a result of prolonged acute flexion of the knee in certain\
occupations.\
\
When the nerve is divided, the most obvious result is "drop-foot"; the\
patient is unable to dorsiflex the foot and cannot lift his toes off the\
ground, so that in walking he is obliged to jerk the foot forwards and\
laterally. The loss of sensibility depends upon whether the nerve is\
divided above or below the origin of the large cutaneous branch which\
comes off just before it passes round the neck of the fibula. In course\
of time the foot becomes inverted and the toes are pointed--pes\
equino-varus--and trophic sores are liable to form.\
\
#The Tibial (internal popliteal) nerve# is rarely injured.\
\
#The Cranial nerves# are considered with affections of the head and neck\
(Vol. II.).\
\
\
NEURALGIA\
\
The term neuralgia is applied clinically to any pain which follows the\
course of a nerve, and is not referable to any discoverable cause. It\
should not be applied to pain which results from pressure on a nerve by\
a tumour, a mass of callus, an aneurysm, or by any similar gross lesion.\
We shall only consider here those forms of neuralgia which are amenable\
to surgical treatment.\
\
#Brachial Neuralgia.#--The pain is definitely located in the\
distribution of one of the branches or nerve roots, is often\
intermittent, and is usually associated with tingling and disturbance of\
tactile sensation. The root of the neck should be examined to exclude\
pressure as the cause of the pain by a cervical rib, a tumour, or an\
aneurysm. When medical treatment fails, the nerve-trunks may be injected\
with saline solution or recourse may be had to operative measures, the\
affected cords being exposed and stretched through an incision in the\
posterior triangle of the neck. If this fails to give relief, the more\
serious operation of resecting the posterior roots of the affected\
nerves within the vertebral canal may be considered.\
\
_Neuralgia of the sciatic nerve_--#sciatica#--is the most common form of\
neuralgia met with in surgical practice.\
\
It is chiefly met with in adults of gouty or rheumatic tendencies who\
suffer from indigestion, constipation, and oxaluria--in fact, the same\
type of patients who are liable to lumbago, and the two affections are\
frequently associated. In hospital practice it is commonly met with in\
coal-miners and others who assume a squatting position at work. The\
onset of the pain may follow over-exertion and exposure to cold and wet,\
especially in those who do not take regular exercise. Any error of diet\
or indulgence in beer or wine may contribute to its development.\
\
The essential symptom is paroxysmal or continuous pain along the course\
of the nerve in the buttock, thigh, or leg. It may be comparatively\
slight, or it may be so severe as to prevent sleep. It is aggravated by\
movement, so that the patient walks lame or is obliged to lie up. It is\
aggravated also by any movement which tends to put the nerve on the\
stretch, as in bending down to put on the shoes, such movements also\
causing tingling down the nerve, and sometimes numbness in the foot.\
This may be demonstrated by flexing the thigh on the abdomen, the knee\
being kept extended; there is no pain if the same manoeuvre is repeated\
with the knee flexed. The nerve is sensitive to pressure, the most\
tender points being its emergence from the greater sciatic foramen, the\
hollow between the trochanter and the ischial tuberosity, and where the\
common peroneal nerve winds round the neck of the fibula. The muscles of\
the thigh are often wasted and are liable to twitch.\
\
The clinical features vary a good deal in different cases; the affection\
is often obstinate, and may last for many weeks or even months.\
\
In the sciatica that results from neuritis and perineuritis, there is\
marked tenderness on pressure due to the involvement of the nerve\
filaments in the sheath of the nerve, and there may be patches of\
cutaneous anaesthesia, loss of tendon reflexes, localised wasting of\
muscles, and vaso-motor and trophic changes. The presence of the\
reaction of degeneration confirms the diagnosis of neuritis. In\
long-standing cases the pain and discomfort may lead to a postural\
scoliosis (_ischias-scoliotica_).\
\
_Diagnosis._--Pain referred along the course of the sciatic nerve on one\
side, or, as is sometimes the case, on both sides, is a symptom of\
tumours of the uterus, the rectum, or the pelvic bones. It may result\
also from the pressure of an abscess or an aneurysm either inside the\
pelvis or in the buttock, and is sometimes associated with disease of\
the spinal medulla, such as tabes. Gluteal fibrositis may be mistaken\
for sciatica. It is also necessary to exclude such conditions as disease\
in the hip or sacro-iliac joint, especially tuberculous disease and\
arthritis deformans, before arriving at a diagnosis of sciatica. A\
digital examination of the rectum or vagina is of great value in\
excluding intra-pelvic tumours.\
\
_Treatment_ is both general and local. Any constitutional tendency, such\
as gout or rheumatism, must be counteracted, and indigestion, oxaluria,\
and constipation should receive appropriate treatment. In acute cases\
the patient is confined to bed between blankets, the limb is wrapped in\
thermogene wool, and the knee is flexed over a pillow; in some cases\
relief is experienced from the use of a long splint, or slinging the leg\
in a Salter's cradle. A rubber hot-bottle may be applied over the seat\
of greatest pain. The bowels should be well opened by castor oil or by\
calomel followed by a saline. Salicylate of soda in full doses, or\
aspirin, usually proves effectual in relieving pain, but when this is\
very intense it may call for injections of heroin or morphin. Potassium\
iodide is of benefit in chronic cases.\
\
Relief usually results from bathing, douching, and massage, and from\
repeated gentle stretching of the nerve. This may be carried out by\
passive movements of the limb--the hip being flexed while the knee is\
kept extended; and by active movements--the patient flexing the limb at\
the hip, the knee being maintained in the extended position. These\
exercises, which may be preceded by massage, are carried out night and\
morning, and should be practised systematically by those who are liable\
to sciatica.\
\
Benefit has followed the injection into the nerve itself, or into the\
tissues surrounding it, of normal saline solution; from 70-100 c.c. are\
injected at one time. If the pain recurs, the injection may require to\
be repeated on many occasions at different points up and down the nerve.\
Needling or acupuncture consists in piercing the nerve at intervals in\
the buttock and thigh with long steel needles. Six or eight needles are\
inserted and left in position for from fifteen to thirty minutes.\
\
In obstinate and severe cases the nerve may be _forcibly stretched_.\
This may be done bloodlessly by placing the patient on his back with the\
hip flexed to a right angle, and then gradually extending the knee until\
it is in a straight line with the thigh (Billroth). A general anaesthetic\
is usually required. A more effectual method is to expose the nerve\
through an incision at the fold of the buttock, and forcibly pull upon\
it. This operation is most successful when the pain is due to the nerve\
being involved in adhesions.\
\
#Trigeminal Neuralgia.#--A severe form of epileptiform neuralgia occurs\
in the branches of the fifth nerve, and is one of the most painful\
affections to which human flesh is liable. So far as its pathology is\
known, it is believed to be due to degenerative changes in the semilunar\
(Gasserian) ganglion. It is met with in adults, is almost invariably\
unilateral, and develops without apparent cause. The pain, which occurs\
in paroxysms, is at first of moderate severity, but gradually becomes\
agonising. In the early stages the paroxysms occur at wide intervals,\
but later they recur with such frequency as to be almost continuous.\
They are usually excited by some trivial cause, such as moving the jaws\
in eating or speaking, touching the face as in washing, or exposure to a\
draught of cold air. Between the paroxysms the patient is free from\
pain, but is in constant terror of its return, and the face wears an\
expression of extreme suffering and anxiety. When the paroxysm is\
accompanied by twitching of the facial muscles, it is called _spasmodic\
tic_.\
\
The skin of the affected area may be glazed and red, or may be pale and\
moist with inspissated sweat, the patient not daring to touch or wash\
it.\
\
There is excessive tenderness at the points of emergence of the\
different branches on the face, and pressure over one or other of these\
points may excite a paroxysm. In typical cases the patient is unable to\
take any active part in life. The attempt to eat is attended with such\
severe pain that he avoids taking food. In some cases the suffering is\
so great that the patient only obtains sleep by the use of hypnotics,\
and he is often on the verge of suicide.\
\
_Diagnosis._--There is seldom any difficulty in recognising the disease.\
It is important, however, to exclude the hysterical form of neuralgia,\
which is characterised by its occurrence earlier in life, by the pain\
varying in situation, being frequently bilateral, and being more often\
constant than paroxysmal.\
\
_Treatment._--Before having recourse to the measures described below, it\
is advisable to give a thorough trial to the medical measures used in\
the treatment of neuralgia.\
\
_The Injection of Alcohol into the Nerve._--The alcohol acts by\
destroying the nerve fibres, and must be brought into direct contact\
with them; if the nerve has been properly struck the injection is\
followed by complete anaesthesia in the distribution of the nerve. The\
relief may last for from six months to three years; if the pain returns,\
the injection may be repeated. The strength of the alcohol should be 85\
per cent., and the amount injected about 2 c.c.; a general, or\
preferably a local, anaesthetic (novocain) should be employed\
(Schlosser); the needle is 8 cm. long, and 0.7 mm. in diameter. The\
severe pain which the alcohol causes may be lessened, after the needle\
has penetrated to the necessary depth, by passing a few cubic\
centimetres of a 2 per cent. solution of _novocain-suprarenin_ through\
it before the alcohol is injected. The treatment by injection of alcohol\
is superior to the resection of branches of the nerve, for though\
relapses occur after the treatment with alcohol, renewed freedom from\
pain may be obtained by its repetition. The ophthalmic division should\
not, however, be treated in this manner, for the alcohol may escape into\
the orbit and endanger other nerves in this region. Harris recommends\
the injection of alcohol into the semilunar ganglion.\
\
_Operative Treatment._--This consists in the removal of the affected\
nerve or nerves, either by resection--_neurectomy_; or by a combination\
of resection with twisting or tearing of the nerve from its central\
connections--_avulsion_. To prevent the regeneration of the nerve after\
these operations, the canal of exit through the bone should be\
obliterated; this is best accomplished by a silver screw-nail driven\
home by an ordinary screw-driver (Charles H. Mayo).\
\
When the neuralgia involves branches of two or of all three trunks, or\
when it has recurred after temporary relief following resection of\
individual branches, the _removal of the semilunar ganglion_, along with\
the main trunks of the maxillary and mandibular divisions, should be\
considered.\
\
The operation is a difficult and serious one, but the results are\
satisfactory so far as the cure of the neuralgia is concerned. There is\
little or no disability from the unilateral paralysis of the muscles of\
mastication; but on account of the insensitiveness of the cornea, the\
eye must be protected from irritation, especially during the first month\
or two after the operation; this may be done by fixing a large\
watch-glass around the edge of the orbit with adhesive plaster.\
\
If the ophthalmic branch is not involved, neither it nor the ganglion\
should be interfered with; the maxillary and mandibular divisions should\
be divided within the skull, and the foramen rotundum and foramen ovale\
obliterated.\
\
\
\
\
CHAPTER XVII\
\
THE SKIN AND SUBCUTANEOUS TISSUE\
\
\
Structure of skin--_Blisters_--_Callosities_--_Corns_--_Chilblains_\
    --_Boils_--_Carbuncle_--_Abscess_--_Veldt sores_--Tuberculosis of\
    skin: _Inoculation tubercle_--_Lupus_: _Varieties_--Sporotrichosis\
    --Elephantiasis--Sebaceous cysts or wens--Moles--Horns--New growths:\
    _Fibroma_; _Papilloma_; _Adenoma_; _Epithelioma_; _Rodent cancer_;\
    _Melanotic cancer_; _Sarcoma_--AFFECTIONS OF CICATRICES--_Varieties\
    of scars_--_Keloid_--_Tumours_--AFFECTIONS OF NAILS.\
\
#Structure of Skin.#--The skin is composed of a superficial cellular\
layer--the epidermis, and the corium or true skin. The _epidermis_ is\
differentiated from without inwards into the stratum corneum, the\
stratum lucidum, the stratum granulosum, and the rete Malpighii or\
germinal layer, from which all the others are developed. The _corium_ or\
_true skin_ consists of connective tissue, in which ramify the blood\
vessels, lymphatics, and nerves. That part of the corium immediately\
adjoining the epidermis is known as the papillary portion, and contains\
the terminal loops of the cutaneous blood vessels and the terminations\
of the cutaneous nerves. The deeper portion of the true skin is known as\
the reticular portion, and is largely composed of adipose tissue.\
\
#Blisters# result from the exudation of serous fluid beneath the horny\
layer of the epidermis. The fluid may be clear, as in the blisters of a\
recent burn, or blood-stained, as in the blisters commonly accompanying\
fractures of the leg. It may become purulent as a result of infection,\
and this may be the starting-point of lymphangitis or cellulitis.\
\
The skin should be disinfected and the blisters punctured. When\
infected, the separated horny layer must be cut away with scissors to\
allow of the necessary purification.\
\
#Callosities# are prominent, indurated masses of the horny layer of the\
epidermis, where it has been exposed to prolonged friction and pressure.\
They occur on the fingers and hand as a result of certain occupations\
and sports, but are most common under the balls of the toes or heel. A\
bursa may form beneath a callosity, and if it becomes inflamed may cause\
considerable suffering; if suppuration ensues, a sinus may form,\
resembling a perforating ulcer of the foot.\
\
The _treatment_ of callosities on the foot consists in removing pressure\
by wearing properly fitting boots, and in applying a ring pad around the\
callosity; another method is to fit a sock of spongiopilene with a hole\
cut out opposite the callosity. After soaking in hot water, the\
overgrown horny layer is pared away, and the part painted daily with a\
saturated solution of salicylic acid in flexile collodion.\
\
[Illustration: FIG. 93.--Callosities and Corns on the Sole and Plantar\
Aspect of the Toes in a woman who was also the subject of flat-foot.]\
\
#Corns.#--A corn is a localised overgrowth of the horny layer of the\
epidermis, which grows downwards, pressing upon and displacing the\
sensitive papillae of the corium. Corns are due to the friction and\
pressure of ill-fitting boots, and are met with chiefly on the toes and\
sole of the foot. A corn is usually hard, dry, and white; but it may be\
sodden from moisture, as in "soft corns" between the toes. A bursa may\
form beneath a corn, and if inflamed constitutes one form of bunion.\
When suppuration takes place in relation to a corn, there is great pain\
and disability, and it may prove the starting-point of lymphangitis.\
\
The _treatment_ consists in the wearing of properly fitting boots and\
stockings, and, if the symptoms persist, the corn should be removed.\
This is done after the manner of chiropodists by digging out the corn\
with a suitably shaped knife. A more radical procedure is to excise,\
under local anaesthesia, the portion of skin containing the corn and\
the underlying bursa. The majority of so-called corn solvents consist of\
a solution of salicylic acid in collodion; if this is painted on daily,\
the epidermis dies and can then be pared away. The unskilful paring of\
corns may determine the occurrence of senile gangrene in those who are\
predisposed to it by disease of the arteries.\
\
[Illustration: FIG. 94.--Ulcerated Chilblains on Fingers of a Child.]\
\
#Chilblains.#--Chilblain or _erythema pernio_ is a vascular disturbance\
resulting from the alternate action of cold and heat on the distal parts\
of the body. Chilblains are met with chiefly on the fingers and toes in\
children and anaemic girls. In the mild form there is a sensation of\
burning and itching, the part becomes swollen, of a dusky red colour,\
and the skin is tense and shiny. In more severe cases the burning and\
itching are attended with pain, and the skin becomes of a violet or\
wine-red colour. There is a third degree, closely approaching\
frost-bite, in which the skin tends to blister and give way, leaving an\
indolent raw surface popularly known as a "broken chilblain."\
\
Those liable to chilblains should take open-air exercise, nourishing\
food, cod-liver oil, and tonics. Woollen stockings and gloves should be\
worn in cold weather, and sudden changes of temperature avoided. The\
symptoms may be relieved by ichthyol ointment, glycerin and belladonna,\
or a mixture of Venice turpentine, castor oil, and collodion applied on\
lint which is wrapped round the toe. Another favourite application is\
one of equal parts of tincture of capsicum and compound liniment of\
camphor, painted over the area night and morning. Balsam of Peru or\
resin ointment spread on gauze should be applied to broken chilblains.\
The most effective treatment is Bier's bandage applied for about six\
hours twice daily; it can be worn while the patient is following his\
occupation; in chronic cases this may be supplemented with hot-air\
baths.\
\
#Boils and Carbuncles.#--These result from infection with the\
staphylococcus aureus, which enters the orifices of the ducts of the\
skin under the influence of friction and pressure, as was demonstrated\
by the well-known experiment of Garre, who produced a crop of pustules\
and boils on his own forearm by rubbing in a culture of the\
staphylococcus aureus.\
\
A #boil# results when the infection is located in a hair follicle or\
sebaceous gland. A hard, painful, conical swelling develops, to which,\
so long as the skin retains its normal appearance, the term "blind\
boil" is applied. Usually, however, the skin becomes red, and after a\
time breaks, giving exit to a drop or two of thick pus. After an\
interval of from six to ten days a soft white slough is discharged; this\
is known as the "core," and consists of the necrosed hair follicle or\
sebaceous gland. After the separation of the core the boil heals\
rapidly, leaving a small depressed scar.\
\
Boils are most frequently met with on the back of the neck and the\
buttocks, and on other parts where the skin is coarse and thick and is\
exposed to friction and pressure. The occurrence of a number or a\
succession of boils is due to spread of the infection, the cocci from\
the original boil obtaining access to adjacent hair follicles. The\
spread of boils may be unwittingly promoted by the use of a domestic\
poultice or the wearing of infected underclothing.\
\
While boils are frequently met with in debilitated persons, and\
particularly in those suffering from diabetes or Bright's disease, they\
also occur in those who enjoy vigorous health. They seldom prove\
dangerous to life except in diabetic subjects, but when they occur on\
the face there is a risk of lymphatic and of general pyogenic infection.\
Boils may be differentiated from syphilitic lesions of the skin by\
their acute onset and progress, and by the absence of other evidence of\
syphilis; and from the malignant or anthrax pustule by the absence of\
the central black eschar and of the circumstances which attend upon\
anthrax infection.\
\
_Treatment._--The skin of the affected area should be painted with\
iodine, and a Klapp's suction bell applied thrice daily. If pus forms,\
the skin is frozen with ethyl-chloride and a small incision made, after\
which the application of the suction bell is persevered with. The\
further treatment consists in the use of diluted boracic or resin\
ointment. In multiple boils on the trunk and limbs, lysol or boracic\
baths are of service; the underclothing should be frequently changed,\
and that which is discarded must be disinfected. In patients with\
recurrence of boils about the neck, re-infection frequently takes place\
from the scalp, to which therefore treatment should be directed.\
\
Any impaired condition of health should be corrected; when, there is\
sugar or albumen in the urine the conditions on which these depend must\
receive appropriate treatment. When there are successive crops of boils,\
recourse should be had to vaccines. In refractory cases benefit has\
followed the subcutaneous injection of lipoid solution containing tin.\
\
#Carbuncle# may be looked upon as an aggregation of boils, and is\
characterised by a densely hard base and a brownish-red discoloration of\
the skin. It is usually about the size of a crown-piece, but it may\
continue to enlarge until it attains the size of a dinner-plate. The\
patient is ill and feverish, and the pain may be so severe as to prevent\
sleep. As time goes on several points of suppuration appear, and when\
these burst there are formed a number of openings in the skin, giving it\
a cribriform appearance; these openings exude pus. The different\
openings ultimately fuse and the large adherent greyish-white slough is\
exposed. The separation of the slough is a tedious process, and the\
patient may become exhausted by pain, discharge, and toxin absorption.\
When the slough is finally thrown off, a deep gap is left, which takes a\
long time to heal. A large carbuncle is a grave disease, especially in a\
weakly person suffering from diabetes or chronic alcoholism; we have on\
several occasions seen diabetic coma supervene and the patient die\
without recovering consciousness. In the majority of cases the patient\
is laid aside for several months. It is most common in male adults over\
forty years of age, and is usually situated on the back between the\
shoulders. When it occurs on the face or anterior part of the neck it is\
especially dangerous, because of the greater risk of dissemination of\
the infection.\
\
A carbuncle is to be differentiated from an ulcerated gumma and from\
anthrax pustule.\
\
[Illustration: FIG. 95.--Carbuncle of seventeen days' duration in a\
woman aet. 57.]\
\
_Treatment._--Pain is relieved by full doses of opium or codein, and\
these drugs are specially indicated when sugar is present in the urine.\
Vaccines may be given a trial. The diet should be liberal and easily\
digested, and strychnin and other stimulants may be of service. Locally\
the treatment is carried out on the same lines as for boils.\
\
In some cases it is advisable to excise the carbuncle or to make\
incisions across it in different directions, so that the resulting wound\
presents a stellate appearance.\
\
#Acute Abscesses of the Skin and Subcutaneous Tissue in Young\
Children.#--In young infants, abscesses are not infrequently met with\
scattered over the trunk and limbs, and are probably the result of\
infection of the sebaceous glands from dirty underclothing. The\
abscesses should be opened, and the further spread of infection\
prevented by cleansing of the skin and by the use of clean under-linen.\
Similar abscesses are met with on the scalp in association with eczema,\
impetigo, and pediculosis.\
\
#Veldt Sore.#--This sore usually originates in an abrasion of the\
epidermis, such as a sun blister, the bite of an insect, or a scratch. A\
pustule forms and bursts, and a brownish-yellow scab forms over it. When\
this is removed, an ulcer is left which has little tendency to heal.\
These sores are most common about the hands, arms, neck, and feet, and\
are most apt to occur in those who have had no opportunities of washing,\
and who have lived for a long time on tinned foods.\
\
#Tuberculosis of the Skin.#--Interest attaches chiefly to the primary\
forms of tuberculosis of the skin in which the bacilli penetrate from\
without--inoculation tubercle and lupus.\
\
#Inoculation Tubercle.#--The appearances vary with the conditions under\
which the inoculation takes place. As observed on the fingers of adults,\
the affection takes the form of an indolent painless swelling, the\
epidermis being red and glazed, or warty, and irregularly fissured.\
Sometimes the epidermis gives way, forming an ulcer with flabby\
granulations. The infection rarely spreads to the lymphatics, but we\
have seen inoculation tubercle of the index-finger followed by a large\
cold abscess on the median side of the upper arm and by a huge mass of\
breaking down glands in the axilla.\
\
In children who run about barefooted in towns, tubercle may be\
inoculated into wounds in the sole or about the toes, and although the\
local appearances may not be characteristic, the nature of the infection\
is revealed by its tendency to spread up the limb along the lymph\
vessels, giving rise to abscesses and fungating ulcers in relation to\
the femoral glands.\
\
#Tuberculous Lupus.#--This is an extremely chronic affection of the\
skin. It rarely extends to the lymph glands, and of all tuberculous\
lesions is the least dangerous to life. The commonest form of\
lupus--_lupus vulgaris_--usually commences in childhood or youth, and is\
most often met with on the nose or cheek. The early and typical\
appearance is that of brownish-yellow or pink nodules in the skin, about\
the size of hemp seed. Healing frequently occurs in the centre of the\
affected area while the disease continues to extend at the margin.\
\
When there is actual destruction of tissue and ulceration--the so-called\
"_lupus excedens_" or "_ulcerans_"--healing is attended with\
cicatricial contraction, which may cause unsightly deformity. When the\
cheek is affected, the lower eyelid may be drawn down and everted; when\
the lips are affected, the mouth may be distorted or seriously\
diminished in size. When the nose is attacked, both the skin and mucous\
surfaces are usually involved, and the nasal orifices may be narrowed or\
even obliterated; sometimes the soft parts, including the cartilages,\
are destroyed, leaving only the bones covered by tightly stretched scar\
tissue.\
\
The disease progresses slowly, healing in some places and spreading at\
others. The patient complains of a burning sensation, but little of\
pain, and is chiefly concerned about the disfigurement. Nothing is more\
characteristic of lupus than the appearance of fresh nodules in parts\
which have already healed. In the course of years large tracts of the\
face and neck may become affected. From the lips it may spread to the\
gum and palate, giving to the mucous membrane the appearance of a\
raised, bright-red, papillary or villous surface. When the disease\
affects the gums, the teeth may become loose and fall out.\
\
[Illustration: FIG. 96.--Tuberculous Elephantiasis in a woman aet. 35.]\
\
On parts of the body other than the face, the disease is even more\
chronic, and is often attended with a considerable production of dense\
fibrous tissue--the so-called _fibroid lupus_. Sometimes there is a\
warty thickening of the epidermis--_lupus verrucosus_. In the fingers\
and toes it may lead to a progressive destruction of tissue like that\
observed in leprosy, and from the resulting loss of portions of the\
digits it has been called _lupus mutilans_. In the lower extremity a\
remarkable form of the disease is sometimes met with, to which the term\
_lupus elephantiasis_ (Fig. 96) has been applied. It commences as an\
ordinary lupus of the toes or dorsum of the foot, from which the\
tuberculous infection spreads to the lymph vessels, and the limb as a\
whole becomes enormously swollen and unshapely.\
\
Finally, a long-standing lupus, especially on the cheek, may become the\
seat of epithelioma--_lupus epithelioma_--usually of the exuberant or\
cauliflower type, which, like other epitheliomas that originate in scar\
tissue, presents little tendency to infect the lymphatics.\
\
The _diagnosis_ of lupus is founded on the chronic progress and long\
duration, and the central scarring with peripheral extension of the\
disease. On the face it is most liable to be confused with syphilis and\
with rodent cancer. The syphilitic lesion belongs to the tertiary\
period, and although presenting a superficial resemblance to\
tuberculosis, its progress is more rapid, so that within a few months it\
may involve an area of skin as wide as would be affected by lupus in as\
many years. Further, it readily yields to anti-syphilitic treatment. In\
cases of tertiary syphilis in which the nose is destroyed, it will be\
noticed that the bones have suffered most, while in lupus the\
destruction of tissue involves chiefly the soft parts.\
\
Rodent cancer is liable to be mistaken for lupus, because it affects the\
same parts of the face; it is equally chronic, and may partly heal. It\
begins later in life, however, the margin of the ulcer is more sharply\
defined, and often presents a "rolled" appearance.\
\
_Treatment._--When the disease is confined to a limited area, the most\
rapid and certain cure is obtained by _excision_; larger areas are\
scraped with the sharp spoon. The _ray treatment_ includes the use of\
luminous, Rontgen, or radium rays, and possesses the advantage of being\
comparatively painless and of being followed by the least amount of\
scarring and deformity.\
\
Encouraging results have also been obtained by the application of carbon\
dioxide snow.\
\
#Multiple subcutaneous tuberculous nodules# are met with chiefly in\
children. They are indolent and painless, and rarely attract attention\
until they break down and form abscesses, which are usually about the\
size of a cherry, and when these burst sinuses or ulcers result. If the\
overlying skin is still intact, the best treatment is excision. If the\
abscess has already infected the skin, each focus should be scraped and\
packed.\
\
#Sporotrichosis# is a mycotic infection due to the sporothrix Shenkii.\
It presents so many features resembling syphilis and tubercle that it is\
frequently mistaken for one or other of these affections. It occurs\
chiefly in males between fifteen and forty-five, who are farmers, fruit\
and vegetable dealers, or florists. There is usually a history of trauma\
of the nature of a scratch or a cut, and after a long incubation period\
there develop a series of small, hard, round nodules in the skin and\
subcutaneous tissue which, without pain or temperature, soften into\
cold abscesses and leave indolent ulcers or sinuses. The infection is\
of slow progress and follows the course of the lymphatics. From the\
gelatinous pus the organism is cultivated without difficulty, and this\
is the essential step in arriving at a diagnosis. The disease yields in\
a few weeks to full doses of iodide of potassium.\
\
#Elephantiasis.#--This term is applied to an excessive enlargement of a\
part depending upon an overgrowth of the skin and subcutaneous cellular\
tissue, and it may result from a number of causes, acting independently\
or in combination. The condition is observed chiefly in the extremities\
and in the external organs of generation.\
\
_Elephantiasis from Lymphatic or Venous Obstruction._--Of this the\
best-known example is _tropical elephantiasis_ (E. arabum), which is\
endemic in Samoa, Barbadoes, and other places. It attacks the lower\
extremity or the genitals in either sex (Figs. 97, 98). The disease is\
usually ushered in with fever, and signs of lymphangitis in the part\
affected. After a number of such attacks, the lymph vessels appear to\
become obliterated, and the skin and subcutaneous cellular tissue, being\
bathed in stagnant lymph--which possibly contains the products of\
streptococci--take on an overgrowth, which continues until the part\
assumes gigantic proportions. In certain cases the lymph trunks have\
been found to be blocked with the parent worms of the filaria Bancrofti.\
Cases of elephantiasis of the lower extremity are met with in this\
country in which there are no filarial parasites in the lymph vessels,\
and these present features closely resembling the tropical variety, and\
usually follow upon repeated attacks of lymphangitis or erysipelas.\
\
The part affected is enormously increased in size, and causes\
inconvenience from its bulk and weight. In contrast to ordinary dropsy,\
there is no pitting on pressure, and the swelling does not disappear on\
elevation of the limb. The skin becomes rough and warty, and may hang\
down in pendulous folds. Blisters form on the surface and yield an\
abundant exudate of clear lymph. From neglect of cleanliness, the skin\
becomes the seat of eczema or even of ulceration attended with foul\
discharge.\
\
Samson Handley has sought to replace the blocked lymph vessels by\
burying in the subcutaneous tissue of the swollen part a number of stout\
silk threads--_lymphangioplasty_. By their capillary action they drain\
the lymph to a healthy region above, and thus enable it to enter the\
circulation. It has been more successful in the face and upper limb than\
in the lower extremity. If the tissues are infected with pus organisms,\
a course of vaccines should precede the operation.\
\
[Illustration: FIG. 97.--Elephantiasis in a woman aet. 45.]\
\
A similar type of elephantiasis may occur after extirpation of the lymph\
glands in the axilla or groin; in the leg in long-standing standing\
varix and phlebitis with chronic ulcer; in the arm as a result of\
extensive cancerous disease of the lymphatics in the axilla secondarily\
to cancer of the breast; and in extensive tuberculous disease of the\
lymphatics. The last-named is chiefly observed in the lower limb in\
young adult women, and from its following upon lupus of the toes or foot\
it has been called _lupus elephantiasis_. The tuberculous infection\
spreads slowly up the limb by way of the lymph vessels, and as these are\
obliterated the skin and cellular tissues become hypertrophied, and the\
surface is studded over with fungating tuberculous masses of a livid\
blue colour. As the more severe forms of the disease may prove dangerous\
to life by pyogenic complications inducing gangrene of the limb, the\
question of amputation may have to be considered.\
\
[Illustration: FIG. 98.--Elephantiasis of Penis and Scrotum in native of\
Demerara.\
\
(Mr. Annandale's case.)]\
\
Belonging to this group also is a form of _congenital elephantiasis_\
resulting from the circular constriction of a limb _in utero_ by\
amniotic bands.\
\
_Elephantiasis occurring apart from lymphatic or venous obstruction_ is\
illustrated by _elephantiasis nervorum_, in which there is an overgrowth\
of the skin and cellular tissue of an extremity in association with\
neuro-fibromatosis of the cutaneous nerves (Fig. 89); and by\
_elephantiasis Graecorum_--a form of leprosy in which the skin of the\
face becomes the seat of tumour-like masses consisting of leprous\
nodules. It is also illustrated by _elephantiasis involving the scrotum_\
as a result of prolonged irritation by the urine in cases in which the\
penis has been amputated and the urine has infiltrated the scrotal\
tissues over a period of years.\
\
#Sebaceous Cysts.#--Atheromatous cysts or wens are formed in relation to\
the sebaceous glands and hair follicles. They are commonly met with in\
adults, on the scalp (Fig. 99), face, neck, back, and external genitals.\
Sometimes they are multiple, and they may be met with in several members\
of the same family. They are smooth, rounded, or discoid cysts, varying\
in size from a split-pea to a Tangerine orange. In consistence they are\
firm and elastic, or fluctuating, and are incorporated with the\
overlying skin, but movable on the deeper structures. The orifice of the\
partly blocked sebaceous follicle is sometimes visible, and the contents\
of the cyst can be squeezed through the opening. The wall of the cyst is\
composed of a connective-tissue capsule lined by stratified squamous\
epithelium. The contents consist of accumulated epithelial cells, and\
are at first dry and pearly white in appearance, but as a result of\
fatty degeneration they break down into a greyish-yellow pultaceous and\
semi-fluid material having a peculiar stale odour. It is probable that\
the decomposition of the contents is the result of the presence of\
bacteria, and that from the surgical point of view they should be\
regarded as infective. A sebaceous cyst may remain indefinitely without\
change, or may slowly increase in size, the skin over it becoming\
stretched and closely adherent to the cyst wall as a result of friction\
and pressure. The contents may ooze from the orifice of the duct and dry\
on the skin surface, leading to the formation of a sebaceous horn\
(Fig. 100). As a result of injury the cyst may undergo sudden\
enlargement from haemorrhage into its interior.\
\
Recurrent attacks of inflammation frequently occur, especially in wens\
of the face and scalp. Suppuration may ensue and be followed by cure of\
the cyst, or an offensive fungating ulcer forms which may be mistaken\
for epithelioma. True cancerous transformation is rare.\
\
Wens are to be _diagnosed_ from dermoids, from fatty tumours, and from\
cold abscesses. Dermoids usually appear before adult life, and as they\
nearly always lie beneath the fascia, the skin is movable over them. A\
fatty tumour is movable, and is often lobulated. The confusion with a\
cold abscess is most likely to occur in wens of the neck or back, and it\
may be impossible without the use of an exploring needle to\
differentiate between them.\
\
[Illustration: FIG. 99.--Multiple Sebaceous Cysts or Wens; the larger\
ones are of many years' duration.]\
\
_Treatment._--The removal of wens is to be recommended while they are\
small and freely movable, as they are then easily shelled out after\
incising the overlying skin; sometimes splitting the cyst makes its\
removal easier. Local anaesthesia is to be preferred. It is important\
that none of the cyst wall be left behind. In large and adherent wens an\
ellipse of skin is removed along with the cyst. When inflamed, it may be\
impossible to dissect out the cyst, and the wall should be destroyed\
with carbolic acid, the resulting wound being treated by the open\
method.\
\
#Moles.#--The term mole is applied to a pigmented, and usually hairy,\
patch of skin, present at or appearing shortly after birth. The colour\
varies from brown to black, according to the amount of melanin pigment\
present. The lesion consists in an overgrowth of epidermis which often\
presents an alveolar arrangement. Moles vary greatly in size: some are\
mere dots, others are as large as the palm of the hand, and occasionally\
a mole covers half the face. In addition to being unsightly, they bleed\
freely when abraded, are liable to ulcerate from friction and pressure,\
and occasionally become the starting-point of melanotic cancer. Rodent\
cancer sometimes originates in the slightly pigmented moles met with on\
the face. Overgrowths in relation to the cutaneous nerves, especially\
the plexiform neuroma, occasionally originate in pigmented moles. Soldau\
believes that the pigmentation and overgrowth of the epidermis in moles\
are associated with, and probably result from, a fibromatosis of the\
cutaneous nerves.\
\
_Treatment._--The quickest way to get rid of a mole is to excise it; if\
the edges of the gap cannot be brought together with sutures, recourse\
should be had to grafting. In large hairy moles of the face whose size\
forbids excision, radium or the X-rays should be employed. Excellent\
results have been obtained by refrigeration with solid carbon dioxide.\
In children and women with delicate skin, applications of from ten to\
thirty seconds suffice. In persons with coarse skin an application of\
one minute may be necessary, and it may have to be repeated.\
\
#Horns.#--The _sebaceous_ horn results from the accumulation of the\
dried contents of a wen on the surface of the skin: the sebaceous\
material after drying up becomes cornified, and as fresh material is\
added to the base the horn increases in length (Fig. 100). The _wart_\
horn grows from a warty papilloma of the skin. _Cicatrix_ horns are\
formed by the heaping up of epidermis in the scars that result from\
burns. _Nail_ horns are overgrown nails (keratomata of the nail bed),\
and are met with chiefly in the great toe of elderly bedridden patients.\
If an ulcer forms at the base of a horn, it may prove the starting-point\
of epithelioma, and for this reason, as well as for others, horns should\
be removed.\
\
[Illustration: FIG. 100.--Sebaceous Horn growing from Auricle.\
\
(Dr. Kenneth Maclachan's case.)]\
\
#New Growths in the Skin and Subcutaneous Tissue.#--The _Angioma_ has\
been described with diseases of blood vessels. _Fibroma._--Various types\
of fibroma occur in the skin. A soft pedunculated fibroma, about the\
size of a pea, is commonly met with, especially on the neck and trunk;\
it is usually solitary, and is easily removed with scissors. The\
multiple, soft fibroma known as _molluscum fibrosum_, which depends upon\
a neuro-fibromatosis of the cutaneous nerves, is described with the\
tumours of nerves. Hard fibromas occurring singly or in groups may be\
met with, especially in the skin of the buttock, and may present a local\
malignancy, recurring after removal like the "recurrent fibroid" of\
Paget. The "painful subcutaneous nodule" is a solitary fibroma related\
to one of the cutaneous nerves. The hard fibroma known as _keloid_ is\
described with the affections of scars.\
\
#Papilloma.#--The _common wart_ or verruca is an outgrowth of the\
surface epidermis. It may be sessile or pedunculated hard or soft. The\
surface may be smooth, or fissured and foliated like a cauliflower, or\
it may be divided up into a number of spines. Warts are met with chiefly\
on the hands, and are often multiple, occurring in clusters or in\
successive crops. Multiple warts appear to result from some contagion,\
the nature of which is unknown; they sometimes occur in an epidemic form\
among school-children, and show a remarkable tendency to disappear\
spontaneously. The solitary flat-topped wart which occurs on the face\
of old people may, if irritated, become the seat of epithelioma. A warty\
growth of the epidermis is a frequent accompaniment of moles and of that\
variety of lupus known as _lupus verrucosus_.\
\
_Treatment._--In the multiple warts of children the health should be\
braced up by a change to the seaside. A dusting-powder, consisting of\
boracic acid with 5 per cent. salicylic acid, may be rubbed into the\
hands after washing and drying. The persistent warts of young adults\
should be excised after freezing with chloride of ethyl. When cutting is\
objected to, they may be painted night and morning with salicylic\
collodion, the epidermis being dehydrated with alcohol before each\
application.\
\
_Venereal warts_ occur on the genitals of either sex, and may form large\
cauliflower-like masses on the inner surface of the prepuce or of the\
labia majora. Although frequently co-existing with gonorrhoea or\
syphilis, they occur independently of these diseases, being probably\
acquired by contact with another individual suffering from warts\
(C. W. Cathcart). They give rise to considerable irritation and\
suffering, and when cleanliness is neglected there may be an offensive\
discharge.\
\
In the female, the cauliflower-like masses are dissected from the labia;\
in the male, the prepuce is removed and the warts on the glans are\
snipped off with scissors. In milder cases, the warts usually disappear\
if the parts are kept absolutely dry and clean. A useful dusting-powder\
is one consisting of calamine and 5 per cent. salicylic acid; the\
exsiccated sulphate of iron, in the form of a powder, may be employed in\
cases which resist this treatment.\
\
#Adenoma.#--This is a comparatively rare tumour growing from the glands\
of the skin. One variety, known as the "tomato tumour," which apparently\
originates from _the sweat glands_, is met with on the scalp and face in\
women past middle life. These growths are often multiple; the individual\
tumours vary in size, and the skin, which is almost devoid of hairs, is\
glistening and tightly stretched over them. A similar tumour may occur\
on the nose. The _sebaceous adenoma_, which originates from the\
sebaceous glands, forms a projecting tumour on the face or scalp, and\
when the skin is irritated it may ulcerate and fungate. The treatment\
consists in the removal of the tumour along with the overlying skin.\
\
The exuberant masses on the nose known as "rhinophyma," "lipoma nasi,"\
or "potato nose" are of the nature of sebaceous adenoma, and are removed\
by shaving them off with a knife until the normal shape of the nose is\
restored Healing takes place with remarkable rapidity.\
\
#Cancer.#--There are several types of primary cancer of the skin, the\
most important being squamous epithelioma, rodent cancer, and melanotic\
cancer.\
\
[Illustration: FIG. 101.--Paraffin Epithelioma.]\
\
#Epithelioma# occurs in a variety of forms. When originating in a small\
ulcer or wart-for example on the face in old people--it presents the\
features of a chronic indurated ulcer. A more exuberant and rapidly\
growing form of epithelial cancer, described by Hutchinson as the\
_crateriform ulcer_, commences on the face as a small red pimple which\
rapidly develops into an elevated mass shaped like a bee-hive, and\
breaks down in the centre. Epithelioma may develop anywhere on the body\
in relation to long-standing ulcers, especially that resulting from a\
burn or from lupus; this form usually presents an exuberant outgrowth of\
epidermis not unlike a cauliflower. An interesting example of\
epithelioma has been described by Neve of Kashmir. The natives in that\
province are in the habit of carrying a fire-basket suspended from the\
waist, which often burns the skin and causes a chronic ulcer, and many\
of these ulcers become the seat of epithelioma, due, in Neve's opinion,\
to the actual contact of the sooty pan with the skin.\
\
The term _trade epithelioma_ has been applied to that form met with in\
those who follow certain occupations, such as paraffin workers and\
chimney-sweeps. The most recent member of this group is the _X-ray\
carcinoma_, which is met with in those who are constantly exposed to the\
irritation of the X-rays; there is first a chronic dermatitis with warty\
overgrowth of the surface epithelium, pigmentation, and the formation of\
fissures and warts. The trade epithelioma varies a good deal in\
malignancy, but it tends to cause death in the same manner as other\
epitheliomas.\
\
Epithelial cancer has also been observed in those who have taken arsenic\
over long periods for medicinal purposes.\
\
[Illustration: FIG. 102.--Rodent Cancer of Inner Canthus.]\
\
#Rodent Cancer# (Rodent Ulcer).--This is a cancer originating in the\
sweat glands or sebaceous follicles, or in the foetal residues of\
cutaneous glands. The cells are small and closely packed together in\
alveoli or in reticulated columns; cell nests are rare. It is remarkably\
constant in its seat of origin, being nearly always located on the\
lateral aspect of the nose or in the vicinity of the lower eyelid\
(Fig. 102). It is rare on the trunk or limbs. It commences as a small\
flattened nodule in the skin, the epidermis over it being stretched and\
shining. The centre becomes depressed, while the margins extend in the\
form of an elevated ridge. Sooner or later the epidermis gives way in\
the centre, exposing a smooth raw surface devoid of granulations.\
\
[Illustration: FIG. 103.--Rodent Cancer of fifteen years' duration,\
which has destroyed the contents of the Orbit.\
\
(Sir Montagu Cotterill's case)]\
\
The margin, while in parts irregular, is typically represented by a\
well-defined "rolled" border which consists of the peripheral portion of\
the cancer that has not broken down. The central ulcer may temporarily\
heal. There is itching but little pain, and the condition progresses\
extremely slowly; rodent cancers which have existed for many years are\
frequently met with. The disease attacks and destroys every structure\
with which it comes in contact, such as the eyelids, the walls of the\
nasal cavities, and the bones of the face; hence it may produce the most\
hideous deformities (Fig. 103). The patient may succumb to haemorrhage or\
to infective complications such as erysipelas or meningitis.\
\
Secondary growths in the lymph glands, while not unknown, are extremely\
rare. We have only seen them once--in a case of rodent cancer in the\
groin.\
\
_Diagnosis._--Lupus is the disease most often mistaken for rodent\
cancer. Lupus usually begins earlier in life, it presents apple-jelly\
nodules, and lacks the rounded, elevated border. Syphilitic lesions\
progress more rapidly, and also lack the characteristic margin. The\
differentiation from squamous epithelioma is of considerable importance,\
as the latter affection spreads more rapidly, involves the lymph glands\
early, and is much more dangerous to life.\
\
_Treatment._--In rodent cancers of limited size--say less than one inch\
in diameter--free excision is the most rapid and certain method of\
treatment. The alternative is the application of radium or of the\
Rontgen rays, which, although requiring many exposures, results in cure\
with the minimum of disfigurement. If the cancer already covers an\
extensive area, or has invaded the cavity of the orbit or nose, radium\
or X-rays yield the best results. The effect is soon shown by the\
ingrowth of healthy epithelium from the surrounding skin, and at the\
same time the discharge is lessened. Good results are also reported from\
the application of carbon dioxide snow, especially when this follows\
upon a course of X-ray treatment.\
\
#Paget's disease# of the nipple is an epithelioma occurring in women\
over forty years of age: a similar form of epithelioma is sometimes met\
with at the umbilicus or on the genitals.\
\
#Melanotic Cancer.#--Under this head are included all new growths which\
contain an excess of melanin pigment. Many of these were formerly\
described as melanotic sarcoma. They nearly always originate in a\
pigmented mole which has been subjected to irritation. The primary\
growth may remain so small that its presence is not even suspected, or\
it may increase in size, ulcerate, and fungate. The amount of pigment\
varies: when small in amount the growth is brown, when abundant it is a\
deep black. The most remarkable feature is the rapidity with which the\
disease becomes disseminated along the lymphatics, the first evidence of\
which is an enlargement of the lymph glands. As the primary growth is\
often situated on the sole of the foot or in the matrix of the nail of\
the great toe, the femoral and inguinal glands become enlarged in\
succession, forming tumours much larger than the primary growth.\
Sometimes the dissemination involves the lymph vessels of the limb,\
forming a series of indurated pigmented cords and nodules (Fig. 104).\
Lastly, the dissemination may be universal throughout the body, and this\
usually occurs at a comparatively early stage. The secondary growths are\
deeply pigmented, being usually of a coal-black colour, and melanin\
pigment may be present in the urine. When recurrence takes place in or\
near the scar left by the operation, the cancer nodules are not\
necessarily pigmented.\
\
[Illustration: FIG. 104.--Diffuse Melanotic Cancer of Lymphatics of Skin\
secondary to a Growth in the Sole of the Foot.]\
\
To extirpate the disease it is necessary to excise the tumour, with a\
zone of healthy skin around it and a somewhat large zone of the\
underlying subcutaneous tissue and deep fascia. Hogarth Pringle\
recommends that a broad strip of subcutaneous fascia up to and including\
the nearest anatomical group of glands should be removed with the tumour\
in one continuous piece.\
\
#Secondary Cancer of the Skin.#--Cancer may spread to the skin from a\
subjacent growth by direct continuity or by way of the lymphatics. Both\
of these processes are so well illustrated in cases of mammary cancer\
that they will be described in relation to that disease.\
\
#Sarcoma# of various types is met with in the skin. The fibroma, after\
excision, may recur as a fibro-sarcoma. The alveolar sarcoma commences\
as a hard lump and increases in size until the epidermis gives way and\
an ulcer is formed.\
\
[Illustration: FIG. 105.--Melanotic Cancer of Forehead with Metastases\
in Lymph Vessels and Glands.\
\
(Mr. D. P. D. Wilkie's case.)]\
\
A number of fresh tumours may spring up around the original growth.\
Sometimes the primary growth appears in the form of multiple nodules\
which tend to become confluent. Excision, unless performed early, is of\
little avail, and in any case should be followed up by exposure to\
radium.\
\
\
AFFECTIONS OF CICATRICES\
\
A cicatrix or scar consists of closely packed bundles of white fibres\
covered by epidermis; the skin glands and hair follicles are usually\
absent. The size, shape, and level of the cicatrix depend upon the\
conditions which preceded healing.\
\
A healthy scar, when recently formed, has a smooth, glossy surface of a\
pinkish colour, which tends to become whiter as a result of obliteration\
of the blood vessels concerned in its formation.\
\
_Weak Scars._--A scar is said to be weak when it readily breaks down as\
a result of irritation or pressure. The scars resulting from severe\
burns and those over amputation stumps are especially liable to break\
down from trivial causes. The treatment is to excise the weak portion of\
the scar and bring the edges of the gap together.\
\
_Contracted scars_ frequently cause deformity either by displacing\
parts, such as the eyelid or lip, or by fixing parts and preventing the\
normal movements--for example, a scar on the flexor aspect of a joint\
may prevent extension of the forearm (Fig. 63). These are treated by\
dividing the scar, correcting the deformity, and filling up the gap with\
epithelial grafts, or with a flap of the whole thickness of the skin.\
When deformity results from _depression of a scar_, as is not uncommon\
after the healing of a sinus, the treatment is to excise the scar.\
Depressed scars may be raised by the injection of paraffin into the\
subcutaneous tissue.\
\
_Painful Scars._--Pain in relation to a scar is usually due to nerve\
fibres being compressed or stretched in the cicatricial tissue; and in\
some cases to ascending neuritis. The treatment consists in excising the\
scar or in stretching or excising a portion of the nerve affected.\
\
_Pigmented or Discoloured Scars._--The best-known examples are the blue\
coloration which results from coal-dust or gunpowder, the brown scars\
resulting from chronic ulcer with venous congestion of the leg, and the\
variously coloured scars caused by tattooing. The only satisfactory\
method of getting rid of the coloration is to excise the scar; the edges\
are brought together by sutures, or the raw surface is covered with\
skin-grafts according to the size of the gap.\
\
_Hypertrophied Scars._--Scars occasionally broaden out and become\
prominent, and on exposed parts this may prove a source of\
disappointment after operations such as those for goitre or tuberculous\
glands in the neck. There is sometimes considerable improvement from\
exposure to the X-rays.\
\
_Keloid._--This term is applied to an overgrowth of scar tissue which\
extends beyond the area of the original wound, and the name is derived\
from the fact that this extension occurs in the form of radiating\
processes, suggesting the claws of a crab. It is essentially a fibroma\
or new growth of fibrous tissue, which commences in relation to the\
walls of the smaller blood vessels; the bundles of fibrous tissue are\
for the most part parallel with the surface, and the epidermis is\
tightly stretched over them. It is more frequent in the negro and in\
those who are, or have been, the subjects of tuberculous disease.\
\
[Illustration: FIG. 106.--Recurrent Keloid in scar left by operation for\
tuberculous glands in a girl aet. 7.]\
\
Keloid may attack scars of any kind, such as those resulting from\
leech-bites, acne pustules, boils or blisters; those resulting from\
operation or accidental wounds; and the scars resulting from burns,\
especially when situated over the sternum, appear to be specially\
liable. The scar becomes more and more conspicuous, is elevated above\
the surface, of a pinkish or brownish-pink pink colour, and sends out\
irregular prolongations around its margins. The patient may complain of\
itching and burning, and of great sensitiveness of the scar, even to\
contact with the clothing.\
\
There is a natural hesitation to excise keloid because of the fear of\
its returning in the new scar. The application of radium is, so far as\
we know, the only means of preventing such return. The irritation\
associated with keloid may be relieved by the application of salicylic\
collodion or of salicylic and creosote plaster.\
\
_Epithelioma_ is liable to attack scars in old people, especially those\
which result from burns sustained early in childhood and have never\
really healed. From the absence of lymphatics in scar tissue, the\
disease does not spread to the glands until it has invaded the tissues\
outside the scar; the prognosis is therefore better than in epithelioma\
in general. It should be excised widely; in the lower extremity when\
there is also extensive destruction of tissue from an antecedent chronic\
ulcer or osteomyelitis, it may be better to amputate the limb.\
\
\
AFFECTION OF THE NAILS\
\
_Injuries._--When a nail is contused or crushed, blood is extravasated\
beneath it, and the nail is usually shed, a new one growing in its\
place. A splinter driven underneath the nail causes great pain, and if\
organisms are carried in along with it, may give rise to infective\
complications. The free edge of the nail should be clipped away to allow\
of the removal of the foreign body and the necessary disinfection.\
\
_Trophic Changes._--The growth of the nails may be interfered with in\
any disturbance of the general health. In nerve lesions, such as a\
divided nerve-trunk, the nails are apt to suffer, becoming curved,\
brittle, or furrowed, or they may be shed.\
\
_Onychia_ is the term applied to an infection of the soft parts around\
the nail or of the matrix beneath it. The commonest form of onychia has\
already been referred to with whitlow. There is a superficial variety\
resulting from the extension of a purulent blister beneath the nail\
lifting it up from its bed, the pus being visible through the nail. The\
nail as well as the raised horny layer of the epidermis should be\
removed. A deeper and more troublesome onychia results from infection at\
the nail-fold; the infection spreads slowly beneath the fold until it\
reaches the matrix, and a drop or two of pus forms beneath the nail,\
usually in the region of the lunule. This affection entails a\
disability of the finger which may last for weeks unless it is properly\
treated. Treatment by hyperaemia, using a suction bell, should first be\
tried, and, failing improvement, the nail-fold and lunule should be\
frozen, and a considerable portion removed with the knife; if only a\
small portion of the nail is removed, the opening is blocked by\
granulations springing from the matrix. A new nail is formed, but it is\
liable to be misshapen.\
\
_Tuberculous onychia_ is met with in children and adolescents. It\
appears as a livid or red swelling at the root of the nail and spreading\
around its margins. The epidermis, which is thin and shiny, gives way,\
and the nail is usually shed.\
\
[Illustration: FIG. 107.--Subungual Exostosis growing from Distal\
Phalanx of Great Toe, showing Ulceration of Skin and Displacement of\
Nail.\
\
_a._ Surface view.   _b._ On section.]\
\
_Syphilitic_ affections of the nails assume various aspects. A primary\
chancre at the edge of the nail may be mistaken for a whitlow,\
especially if it is attended with much pain. Other forms of onychia\
occur during secondary syphilis simultaneously with the skin eruptions,\
and may prove obstinate and lead to shedding of the nails. They also\
occur in inherited syphilis. In addition to general treatment, an\
ointment containing 5 per cent. of oleate of mercury should be applied\
locally.\
\
_Ingrowing Toe-nail._--This is more accurately described as an\
overgrowth of the soft tissues along the edge of the nail. It is most\
frequently met with in the great toe in young adults with flat-foot\
whose feet perspire freely, who wear ill-fitting shoes, and who cut\
their toe-nails carelessly or tear them with their fingers. Where the\
soft tissues are pressed against the edge of the nail, the skin gives\
way and there is the formation of exuberant granulations and of\
discharge which is sometimes foetid. The affection is a painful one and\
may unfit the patient for work. In mild cases the condition may be\
remedied by getting rid of contributing causes and by disinfecting the\
skin and nail; the nail is cut evenly, and the groove between it and the\
skin packed with an antiseptic dusting-powder, such as boracic acid. In\
more severe cases it may be necessary to remove an ellipse of tissue\
consisting of the edge of the nail, together with the subjacent matrix\
and the redundant nail-fold.\
\
_Subungual exostosis_ is an osteoma growing from the terminal phalanx of\
the great toe (Fig. 107). It raises the nail and may be accompanied by\
ulceration of the skin over the most prominent part of the growth. The\
soft parts, including the nail, should be reflected towards the dorsum\
in the form of a flap, the base of the exostosis divided with the\
chisel, and the exostosis removed.\
\
_Malignant disease_ in relation to the nails is rare. Squamous\
epithelioma and melanotic cancer are the forms met with. Treatment\
consists in amputating the digit concerned, and in removing the\
associated lymph glands.\
\
\
\
\
CHAPTER XVIII\
\
THE MUSCLES, TENDONS, AND TENDON SHEATHS\
\
\
INJURIES: _Contusion_; _Sprain_; _Rupture_--Hernia of\
    muscle--Dislocation of tendons--Wounds--Avulsion of tendon.\
    DISEASES OF MUSCLE AND OF TENDONS: _Atrophy_; _"Muscular\
    rheumatism"_--_Fibrositis_; _Contracture_; _Myositis_;\
    _Calcification and Ossification_; _Tumours_. DISEASES OF TENDON\
    SHEATHS: _Teno-synovitis_.\
\
\
INJURIES\
\
#Contusion of Muscle.#--Contusion of muscle, which consists in bruising\
of its fibres and blood vessels, may be due to violence acting from\
without, as in a blow, a kick, or a fall; or from within, as by the\
displacement of bone in a fracture or dislocation.\
\
The symptoms are those common to all contusions, and the patient\
complains of severe pain on attempting to use the muscle, and maintains\
an attitude which relaxes it. If the sheath of the muscle also is torn,\
there is subcutaneous ecchymosis, and the accumulation of blood may\
result in the formation of a haematoma.\
\
Restoration of function is usually complete; but when the nerve\
supplying the muscle is bruised at the same time, as may occur in the\
deltoid, wasting and loss of function may be persistent. In exceptional\
cases the process of repair may be attended with the formation of bone\
in the substance of the muscle, and this may likewise impair its\
function.\
\
A contused muscle should be placed at rest and supported by cotton wool\
and a bandage; after an interval, massage and appropriate exercises are\
employed.\
\
#Sprain and Partial Rupture of Muscle.#--This lesion consists in\
overstretching and partial rupture of the fibres of a muscle or its\
aponeurosis. It is of common occurrence in athletes and in those who\
follow laborious occupations. It may follow upon a single or repeated\
effort--especially in those who are out of training. Familiar examples\
of muscular sprain are the "labourer's" or "golfer's back," affecting\
the latissimus dorsi or the sacrospinalis (erector spinae); the\
"tennis-player's elbow," and the "sculler's sprain," affecting the\
muscles and ligaments about the elbow; the "angler's elbow," affecting\
the common origin of the extensors and supinators; the "sprinter's\
sprain," affecting the flexors of the hip; and the "jumper's and\
dancer's sprain," affecting the muscles of the calf. The patient\
complains of pain, often sudden in onset, of tenderness on pressure, and\
of inability to carry out the particular movement by which the sprain\
was produced. The disability varies in different cases, and it may\
incapacitate the patient from following his occupation or sport for\
weeks or, if imperfectly treated, even for months.\
\
The _treatment_ consists in resting the muscle from the particular\
effort concerned in the production of the sprain, in gently exercising\
it in other directions, in the use of massage, and the induction of\
hyperaemia by means of heat. In neglected cases, that is, where the\
muscle has not been exercised, the patient shrinks from using it and the\
disablement threatens to be permanent; it is sometimes said that\
adhesions have formed and that these interfere with the recovery of\
function. The condition may be overcome by graduated movements or by a\
sudden forcible movement under an anaesthetic. These cases afford a\
fruitful field for the bone-setter.\
\
#Rupture of Muscle or Tendon.#--A muscle or a tendon may be ruptured in\
its continuity or torn from its attachment to bone. The site of rupture\
in individual muscles is remarkably constant, and is usually at the\
junction of the muscular and tendinous portions. When rupture takes\
place through the belly of a muscle, the ends retract, the amount of\
retraction depending on the length of the muscle, and the extent of its\
attachment to adjacent aponeurosis or bone. The biceps in the arm, and\
the sartorius in the thigh, furnish examples of muscles in which the\
separation between the ends may be considerable.\
\
The gap in the muscle becomes filled with blood, and this in time is\
replaced by connective tissue, which forms a bond of union between the\
ends. When the space is considerable the connecting medium consists of\
fibrous tissue, but when the ends are in contact it contains a number of\
newly formed muscle fibres. In the process of repair, one or both ends\
of the muscle or tendon may become fixed by adhesions to adjacent\
structures, and if the distal portion of a muscle is deprived of its\
nerve supply it may undergo degeneration and so have its function\
impaired.\
\
Rupture of a muscle or tendon is usually the result of a sudden, and\
often involuntary, movement. As examples may be cited the rupture of\
the quadriceps extensor in attempting to regain the balance when falling\
backwards; of the gastrocnemius, plantaris, or tendo-calcaneus in\
jumping or dancing; of the adductors of the thigh in gripping a horse\
when it swerves--"rider's sprain"; of the abdominal muscles in vomiting,\
and of the biceps in sudden movements of the arm. Sometimes the effort\
is one that would scarcely be thought likely to rupture a muscle, as in\
the case recorded by Pagenstecher, where a professional athlete, while\
sitting at table, ruptured his biceps in a sudden effort to catch a\
falling glass. It would appear that the rupture is brought about not so\
much by the contraction of the muscle concerned, as by the contraction\
of the antagonistic muscles taking place before that of the muscle which\
undergoes rupture is completed. The violent muscular contractions of\
epilepsy, tetanus, or delirium rarely cause rupture.\
\
The _clinical features_ are usually characteristic. The patient\
experiences a sudden pain, with the sensation of being struck with a\
whip, and of something giving way; sometimes a distant snap is heard.\
The limb becomes powerless. At the seat of rupture there is tenderness\
and swelling, and there may be ecchymosis. As the swelling subsides, a\
gap may be felt between the retracted ends, and this becomes wider when\
the muscle is thrown into contraction. If untreated, a hard, fibrous\
cord remains at the seat of rupture.\
\
_Treatment._--The ends are approximated by placing the limb in an\
attitude which relaxes the muscle, and the position is maintained by\
bandages, splints, or special apparatus. When it is impossible thus to\
approximate the ends satisfactorily, the muscle or tendon is exposed by\
incision, and the ends brought into accurate contact by catgut sutures.\
This operation of primary suture yields the most satisfactory results,\
and is most successful when it is done within five or six days of the\
accident. Secondary suture after an interval of months is rendered\
difficult by the retraction of the ends and by their adhesion to\
adjacent structures.\
\
_Rupture of the biceps of the arm_ may involve the long or the short\
head, or the belly of the muscle. Most interest attaches to rupture of\
the long tendon of origin. There is pain and tenderness in front of the\
upper end of the humerus, the patient is unable to abduct or to elevate\
the arm, and he may be unable to flex the elbow when the forearm is\
supinated. The long axis of the muscle, instead of being parallel with\
the humerus, inclines downwards and outwards. When the patient is asked\
to contract the muscle, its belly is seen to be drawn towards the\
elbow.\
\
The _adductor longus_ may be ruptured, or torn from the pubes, by a\
violent effort to adduct the limb. A swelling forms in the upper and\
medial part of the thigh, which becomes smaller and harder when the\
muscle is thrown into contraction.\
\
The _quadriceps femoris_ is usually ruptured close to its insertion into\
the patella, in the attempt to avoid falling backwards. The injury is\
sometimes bilateral. The injured limb is rendered useless for\
progression, as it suddenly gives way whenever the knee is flexed.\
Treatment is conducted on the same lines as in transverse fracture of\
the patella; in the majority of cases the continuity of the quadriceps\
should be re-established by suture within five or six days of the\
accident.\
\
The _tendo calcaneus_ (Achillis) is comparatively easily ruptured, and\
the symptoms are sometimes so slight that the nature of the injury may\
be overlooked. The limb should be put up with the knee flexed and the\
toes pointed. This may be effected by attaching one end of an elastic\
band to the heel of a slipper, and securing the other to the lower third\
of the thigh. If this is not sufficient to bring the ends into\
apposition they should be approximated by an open operation.\
\
The _plantaris_ is not infrequently ruptured from trivial causes, such\
as a sudden movement in boxing, tennis, or hockey. A sharp stinging pain\
like the stroke of a whip is felt in the calf; there is marked\
tenderness at the seat of rupture, and the patient is unable to raise\
the heel without pain. The injury is of little importance, and if the\
patient does not raise the heel from the ground in walking, it is\
recovered from in a couple of weeks or so, without it being necessary to\
lay him up.\
\
#Hernia of Muscle.#--This is a rare condition, in which, owing to the\
fascia covering a muscle becoming stretched or torn, the muscular\
substance is protruded through the rent. It has been observed chiefly in\
the adductor longus. An oval swelling forms in the upper part of the\
thigh, is soft and prominent when the muscle is relaxed, less prominent\
when it is passively extended, and disappears when the muscle is thrown\
into contraction. It is liable to be mistaken, according to its\
situation, for a tumour, a cyst, a pouched vein, or a femoral or\
obturator hernia. Treatment is only called for when it is causing\
inconvenience, the muscle being exposed by a suitable incision, the\
herniated portion excised, and the rent in the sheath closed by sutures.\
\
#Dislocation of Tendons.#--Tendons which run in grooves may be displaced\
as a result of rupture of the confining sheath. This injury is met with\
chiefly in the tendons at the ankle and in the long tendon of the\
biceps.\
\
Dislocation of the _peronei tendons_ may occur, for example, from a\
violent twist of the foot. There is severe pain and considerable\
swelling on the lateral aspect of the ankle; the peroneus longus by\
itself, or together with the brevis, can be felt on the lateral aspect\
or in front of the lateral malleolus; the patient is unable to move the\
foot. By a little manipulation the tendons are replaced in their\
grooves, and are retained there by a series of strips of plaster. At the\
end of three weeks massage and exercises are employed.\
\
In other cases there is no history of injury, but whenever the foot is\
everted the tendon of the peroneus longus is liable to be jerked\
forwards out of its groove, sometimes with an audible snap. The patient\
suffers pain and is disabled until the tendon is replaced. Reduction is\
easy, but as the displacement tends to recur, an operation is required\
to fix the tendon in its place. An incision is made over the tendon; if\
the sheath is slack or torn, it is tightened up or closed with catgut\
sutures; or an artificial sheath is made by raising up a quadrilateral\
flap of periosteum from the lateral aspect of the fibula, and stitching\
it over the tendon.\
\
Similarly the _tibialis posterior_ may be displaced over the medial\
malleolus as a result of inversion of the foot.\
\
The _long tendon of the biceps_ may be dislocated laterally--or more\
frequently medially--as a result of violent or repeated rotation\
movements of the arm, such as are performed in wringing clothes. The\
patient is aware of the displacement taking place, and is unable to\
extend the forearm until the displaced tendon has been reduced by\
abducting the arm. In recurrent cases the patient may be able to\
dislocate the tendon at will, but the disability is so inconsiderable\
that there is rarely any occasion for interference.\
\
#Wounds of Muscles and Tendons.#--When a muscle is cut across in a\
wound, its ends should be brought together with sutures. If the ends are\
allowed to retract, and especially if the wound suppurates, they become\
united by scar tissue and fixed to bone or other adjacent structure. In\
a limb this interferes with the functions of the muscle; in the\
abdominal wall the scar tissue may stretch, and so favour the\
development of a ventral hernia.\
\
Tendons may be cut across accidentally, especially in those wounds so\
commonly met with above the wrist as a result, for example, of th\
}