OF HYSIOLOGY Ritchie UC-NRLF GIFT OF BIOLOGY UBftAJtY 6 NEW- WORLD HEALTH BOOK //A,'' PRIMER OF PHYSIOLOGY BEING A PRACTICAL TEXTBOOK OF PHYSIOLOGICAL PRINCIPLES AND THEIR APPLICATIONS TO PROBLEMS OF HEALTH BY JOHN W. RITCHIE EDITOR OF NEW-WORLD SCIENCE SERIES; JOINT AUTHOR OF NEW-WORLD HEALTH SERIES Illustrated by EARL HORTER HERMANN HEYER HARRY FREEMAN 1920 REVISION YONKERS-ON-HUDSON, NEW YORK WORLD BOOK COMPANY 1920 WORLD BOOK COMPANY THElHOCJSE OF APPLIED KNOWLEDGE gjQLOGY Established, 1905, by Caspar W. Hodgson YONKERS-ON-HUDSON, NEW YORK 2126 PRAIRIE AVENUE, CHICAGO " Our national health is physically our greatest asset. To prevent any possible deterioration of the American stock should be a national ambition." These words of Theodore Roosevelt express the idea that has actuated authors and publisher of New- World Health Series. The texts explain the means by which young Americans can lay the foundations for sane and vigorous lives. They stand preeminent among Books That Apply the World's Knowledge to the World's Needs. This, the third book, com- pletes the series for elementary schools and teaches health conservation through prac- tical applications to daily life of modern hygiene based on physiological principles. The conservation of individual and national health is the purpose of the series Gift KWHSIRP OF P-I? Copyright, 1913, 1917, 1920, by World Book Company Copyright in Great Britain All lights reserved PREFACE IN this last volume of a series of elementary school texts, the author has attempted to give the pupil a general idea of the plan and working of his body ; to make plain to him the pos- sibilities of health ; and to point out the paths that lead to the realization of these possibilities. In how far the attempt has been successful, the contents of the book itself must decide ; a preface can neither make nor mar that which is already written. On three points, however, the writer will venture a word that may make clear the point of view of both this volume and the series of which it is a part. In the preparation of the series the matter relating to in- fectious diseases has been given a separate volume, Primer of Sanitation, but only to a measured extent has it seemed advisable to attempt a division of topics between the present volume and the first book of the series, Primer of Hygiene. The fact that many children leave school at an early age seems to demand that an elementary course, including that which is of most value in the field of personal hygiene and complete within itself, be given in the lower grades. The fact that this arrange- ment is necessary is no misfortune, however ; for in the teaching of physiology and hygiene, as in the teaching of arithmetic, grammar, and geography, the best results are obtained by making a general study of the whole subject before more detailed work is taken up in any particular field. It is believed that the introduction of new and different subject-matter and the treatment from the physiological point of view will prevent any feeling of repetition when topics that have been studied in Primer of Hygiene are again taken up in this volume. The author believes that hygiene is best taught by giving a solid basis of structure and function for it. He has little confi- dence in get-wise-quick methods in any subject, and he has not hesitated to include in this volume sufficient physiology, with the anatomy that is needed to make it intelligible, to give an outline knowledge of the human mechanism. At the same time, the attempt has been made to select for treatment, from the vast field of physiology, topics that have direct and vital 515607 iv ' '" '.';". ' /. '^PREFACE hygienic applications, to teach hygiene through the modern physiology that lies behind it, rather than to teach hygiene by rule-of-thumb methods or to teach physiology for its own sake. It has been thought best at times to go somewhat far afield with the hope of widening the pupil's hygienic horizon ; for the world is filled with people who for lack of a few large ideas are unable to use the many small ones that they have accumulated. With the idea that children ought not to be taught the matter that is in a book of this kind because it may bring into their minds thoughts of sickness, the author is, of course, not in agreement. The real and vivid ideas of disease that are in the minds of children come not from books, but from personal ex- perience on beds of sickness ; from first-hand knowledge of the suffering of disease-stricken parents, brothers, and sisters ; and from the sudden vanishing of playmates and friends. As long as disease is in the lives of children, it will be in their minds, and the way to put it out of their minds is to banish it from their lives. The author has done his part in the writing of this series of books with the hope that they would do something to bring sunshine and happiness into the lives of the children that now are and are yet to be. He believes that modern hygienic knowledge is able to free our people from most of their illnesses, and that, this knowledge ought to be given to the people by the schools that have been founded for their instruction. The author wishes to thank all those who have assisted him during the preparation of this work and to acknowledge specifi- cally his obligation to the following gentlemen, each of whom has read all or part of the proof: Professor J. S. Caldwell, Dr. F. B. Dresslar, Dr. Graham Lusk, and especially, Dr. Martin H. Fischer. For the point of view of the book, how- ever, and for any errors that may be in it, the author alone is responsible. CONTENTS CHAPTER PAGE I. THE POSSIBILITIES OF GOOD HEALTH . . i II. THE HUMAN BODY AND THE CELLS OF WHICH IT is BUILT 7 III. THE FRAMEWORK OF THE BODY . . . 16 IV. THE MUSCLES AND THE CARRIAGE OF THE BODY 26 V. THE HEART AND THE CIRCULATION OF THE BLOOD 39 VI. RESPIRATION 53 VII. VENTILATION 60 VIII. ADENOIDS AND COLDS 70 IX. CLOTHING AND THE BODY HEAT ... 83 X. THE NERVOUS SYSTEM 91 XI. THE CARE OF THE NERVOUS SYSTEM . . 102 XII. THE EYE . .109 XIII. THE EAR 122 XIV. THE ORGANS OF TOUCH, TASTE, AND SMELL . 129 XV. FOODS AND WHY WE NEED THEM . . .135 XVI. THE DIGESTIVE ORGANS AND THEIR WORK . 145 XVII. THE FOODS WITHIN THE BODY . . . .158 XVIII. FOODS AND HEALTH 166 XIX. THE TEETH 183 XX. TOBACCO 197 XXI. ALCOHOL . . . . . . . .210 XXII. ACCIDENTS 221^ XXIII. REALIZING HEALTH POSSIBILITIES . . . 233 APPENDIX .243 PRONOUNCING GLOSSARY 246 INDEX . 247 We suffer from disease because of ignorance 5 we escape it through knowledge. RICHARDS. CHAPTER ONE THE POSSIBILITIES OF GOOD HEALTH FIG. i. The length of time a top will spin depends on the conditions under which the spinning is done. THREE boys at the same time threw their tops into a ring drawn on the earth. One top struck a pebble, bounded into the air, and fell motionless on its side. Another top worked its way into a little sandy hollow in the earth, and in thirty seconds its spinning was over. The third top settled down on the smooth earth and continued to spin steadily and quietly for more than a minute. How long will a top spin ? It is not possible to answer this question definitely because the length of time it will spin depends on the conditions under which the spinning is done. Length of human life dependent on the care that is given the body. In Europe three hundred years ago, the average human life was twenty years ; today it is PRIMER OF PHYSIOLOGY Sweden Massachusetts Europe India forty years. At the present time it is in India twenty- four years and in Sweden fifty-two years. In New York City twelve years have been added to the average life since 1866, and in Indiana from 1900 to 1910 human life lengthened at the rate of six months each year. During this period, therefore, the people of Indiana may be said to have won back one-half the time that the passage of the years took from them. There is a common idea that the body has a certain " nat- ural " lifetime. , The facts show that this idea is incor- rect. The engine of an auto- mobile wears out in a month if it is neglected, and it lasts for years if it is given proper care. The human machine likewise has no definite length of life. It may be destroyed in its first month by impure milk ; it may suddenly be wrecked by the germs of typhoid fever after it has been running smoothly for twenty-five years ; or, if properly cared for, it may give good service for sixty, seventy, or even eighty years. A top spins longer on a smooth than on a rough surface ; an automobile lasts longer when it is given proper care than when it receives rough treatment; and human life is longer when the body lives and works under favor- 52yrs. 45yrs. 4oyrs. 24 yrs. FlG. 2. A diagram showing the average length of life in different parts of the world." The length of time the human body lasts depends on the care that it receives. THE POSSIBILITIES OF GOOD HEALTH Spain able conditions than it is when the body is neglected and abused. The possibilities of preventing sickness. In India, where the people live under bad sanitary conditions, there is a daily average of India eighty-four sick persons for each one thousand of popula- tion. In Spain, for each one thousand inhabitants the daily average is fifty-six ; in the United States it is thirty ; and in New Zealand it is nineteen. In five of the largest Euro- pean cities, in the year 1880, the daily average of sick persons was fifty-five for each one thousand inhabitants; by 1909 this average had fallen to thirty-one. In the United States there is still much pre- ventable illness, but the sick- ness among us decreased 23 per ' cent between the years 1890 and 1909. United States I New Zealand 84 5 6 30 19 FIG. 3. A diagram showing the average daily number of sick per- sons per looo inhabitants in dif- These facts prove that the ferent countries. The amount of ... . ,.._ sickness in any country depends amount of Sickness in differ- to a great extent on the degree of ent countries depends on the intelligence its people use in deal- degree Of intelligence that the ^g with matters of health. people use in dealing with matters of health. They show that each community has it largely in its own power to decide how many of its people shall each day be sick and how many of them shall be in health. PRIMER OF PHYSIOLOGY Disease prevails because of ignorance. In our own country there are at all times 1,500,000 persons seriously ill with preventable diseases. This means that each year we have 1,500,000 years of unnecessary sickness among us. Why do people undergo all this suffering if it is possible to escape it ? It is because there still lin- gers in the common mind the age-old idea that disease is an unes- 6 capable thing sent upon 34 us by the Fates, and that health comes be- 2 7 26 cause of good fortune and not because it is deserved or earned. We now know that this belief is incorrect ; that if men are willing to work for health and to earn it, they may, in the great majority of o II } t f . J J 1906 1907 1908 1909 1910 1911 1912 1913 FIG. 4. A diagram showing the number of typhoid fever cases in Williamsburg, Virginia, from 1906 to 1913. In 1911 the closets were real Causes of most dlS- screened, so that flies could not carry typhoid gaSCS have been dis- germs about the town. covered; the methods of preventing them have been worked out. Some of these discoveries we are taking advantage of, but many of them are not understood by the people, and as yet there is not a community in the world that will allow its health officers and physicians to use all their knowl- edge in the prevention of disease. The ancient Greeks THE POSSIBILITIES OF GO&D HEALTH 5 taught that knowledge is virtue and ignorance is sin. The great sin in the hygienic world today is ignorance, and we are punished for this ignorance by the prevent- able illness that is among us. Learning to keep the laws of life. Cut your finger and you will suffer ; burn your hand and you will smart for it. Observe the laws under which your body lives and you FIGS. 5 and 6. Louis Cornaro and Alexander the Great. Alexander, a daring and all-conquering warrior of the ancient world, died at the age of 33 because he paid no attention to his health. Cornaro, who was an Italian nobleman, lived from 1464 to 1566 102 years. When he was 40 years old he was told by his physicians that he would die, but he gave great attention to hygiene, regained his health, and lived to enjoy a life of profit to himself and others. will enjoy health; break them and you must bear the punishment. Whether you like these laws or not has nothing to do with the question. You did not make them ; you cannot change them. All that you can do is to find out what they are and then obey them. As you go through life, you will doubtless find certain persons who do not wish to recognize the existence of these laws and who are trying to find some means of escaping from them. This is impossible ; for Nature's decrees are un- yielding and unchangeable. The sensible course, there- 6 PRIMER OF PHYSIOLOGY fore, is to listen to the commands of Nature, to learn her laws and give obedience to them. In this book we shall study the human body and the laws of its life. QUESTIONS What was the average length of life in Europe 300 years ago? What is the average length of life at the present time in India? in Sweden? In New York City how much has been added to the average life since 1866 ? How rapidly was life lengthened in Indiana from 1900 to 1910 ? Is there a " nat- ural " lifetime for the body? Give a reason for your answer. How many persons are sick each day for each 1000 inhabitants in India? in Spain? in the United States? in New Zealand? How much has sickness decreased in certain European cities during the last 30 years? in the United -States during the last 20 years? How much preventable illness is there in the United States each year? Why do people allow this sickness among them? What result follows the keeping of Nature's laws? What is the result of breaking these laws ? What course should we pursue with regard to them ? SUGGESTIONS TO THE TEACHER Keep before the class at all times the idea that health is the nor- mal condition of the body and that disease is in the main prevent- able. Make the pupils realize that health conservation has ceased to be a scientific problem and has become a social and educational prob- lem ; that science has pointed out how to save annually in the United States 600,000 lives and how to prevent most of the sickness from which we suffer. Secure from local city and state boards of health whatever vital statistics are available and point out the great number of deaths occurring locally from preventable diseases. For suggestions as to additional material that may be used with this chapter, see page 15. CHAPTER TWO THE HUMAN BODY AND THE CELLS OF WHICH IT IS BUILT HAVE you ever watched a little plant push its way out of a seed, thrust its roots downward into the earth, and unfold its leaves to the light ? And have you seen such a plant grow larger day by day, until finally it blos- somed and bore seeds like the parent seed from which it grew ? If you have worked in a garden and un- derstand plants, you must often have thought that they are very much like the people about us in the way they grow , . . FIG. 7. The life cycle of the bean. and go through the cycle of their lives. This is indeed the truth, and, in order that you may better understand your own bodies, we shall begin this chapter by learning something of the structure of a plant and of how a plant grows. A plant composed of cells. If you could examine a small portion of a leaf or other living part of a plant under a microscope, you would find that it is composed of little parts built together, as stones are built together to make a wall. The little parts of which the plant is built are called cells. Each cell is composed of a half-liquid living material, which is inclosed by a cell wall. In the center of the living matter is a denser portion, which is called 7 8 PRIMER OF PHYSIOLOGY the nucleus. All the living parts of a plant are com- posed of cells. How the young plant starts from a cell called the egg. Break open a seed and you will find in it a young plant. Where did it come from ? It grew from a cell called the egg. This cell at first is like the other cells of which the seed is built, but at a certain time it increases FIG. 8. Cells from the liver, as seen under a microscope, highly magnified. FIG. 9. Cells drawn diagrammat- ically to show the spaces among them, highly magnified. in size and gathers to itself a rich food supply. It then begins to divide, and from it the new plant comes. Be- fore we begin the story of its growth, however, there are some .other things that it is well for us to understand. The parts of a flower. Examine almost any common flower, and you will have no trouble in recognizing the parts shown in Figure n. First come the little green sepals, then the bright- colored petals, next the stamens, and in the center one or more pistils. The lower part of the pistil contains the young seeds and becomes the seed pod. In the heads of the stamens is a fine, powdery substance called pollen. When we ex- amine pollen under a microscope, we see that it is composed of a great number of little grains. Each FIG. 10. A pine seed cut open to show the young plant in it. THE HUMAN BODY AND ITS CELLS stamen petal pistil sepal little grain is, in reality, a cell; each contains living matter and a nucleus, as do other cells. The egg fertilized by the pollen. Bees visit flowers for the nectar that is in the blossoms and for the pollen, which they gather and mix with honey in mak- ing " bee bread " for their young. In pass- ing into a flower and out of it, a bee often leaves pollen on the sticky outer end of the pistil. When a pollen grain is thus left On a FIG. n. The parts of a flower. To the pistil, a long, thread. ?5g2T**^" like tube grows out from it, makes its way down through the pistil to a young seed, enters the seed, and finds the egg (Fig. 13). Then a nucleus from the pollen grain passes out of the tube and unites with the nucleus of the egg. The uniting of the nucleus of the pollen grain with the nucleus of the egg is called fertilization, and \ is said to be fertilized, be- is shown growing out cause in some way it is given the power to grow and make a new plant. 1 The growth of the egg into a new plant. After the egg is fertilized, it begins to grow. In a very short time 1 When the pollen is washed away by rains, or when the spring is so cold and wet that bees and other insects cannot visit the flowers, the straw- berry, plum, peach, and cherry crops fail. Without the pollen the eggs in the young seeds do not grow, the seeds die, and the fruit drops off. FlG. 12. Pollen grains. , On the left a pollen tube t IO PRIMER OF PHYSIOLOGY pollen grain pollen tube it divides into two cells. Each of these again divides, making four cells, and the process goes on until there is a group of many cells, which have come from the dividing of the egg. From these cells are formed the roots, the stem, the leaves, and the other parts of the new plant. The outer ones change into skin or bark to protect the delicate living cells within. Some change into long wooden vessels to carry water from the earth up to the leaves ; some form vessels for carrying food throughout the plant ; and other cells take up all the different kinds of work that must be done within the plant. Usually the little plant FIG. 13. Diagram show- ing how the pollen tube passes down through the pistil to the egg. stops at a certain stage of growth and rests within the seed until the warmth of the next spring stirs the cells into renewed activity and calls the plant forth to a new life. c D FlG. 14. Four stages in the development of the young plant from the egg. A represents the egg, B shows the division into two cells, and C and D are later stages. In two of the cells in C, the nuclei have divided, but the new cell walls have not yet been formed. THE HUMAN BODY AND ITS CELLS II The growth of the human body from a single cell. The human body, like the body of a plant, starts from one cell. This cell divides and re-divides until it forms a great cluster of thousands of cells. Of these cells all the organs and parts of the body are built. Some cells build lime around themselves and form the bones. Some build a great network of tough fibers, called con- nective tissue fibers, which hold all the body together. Other cells make up the muscles ; certain cells form organs for digesting the food ; the outermost ones make for the body a tough covering which we call the skin; a great group in the FlGS ; and l6> In ' its first stage head and along the back connective tissue is a group of cells become the brain and nerv- ous system ; and still other 15. cells become fitted for doing all the Other kinds of Work framework of connective tissue runs, that must be done in the body. Thus we see that the human body, like the bodies of all living things, whether they be plants or animals, starts with a single cell ; and that when the body is grown, all its parts are composed of cells, or of supporting substances, like bone or connective tissue fibers, that the cells have built. The cells alive. You will now understand that if you could examine with a microscope a small portion of the heart, the liver, or the brain, you would find it com- This material hardens into the cells> rans ' and tissues 12 PRIMER OF PHYSIOLOGY posed "of a multitude of small cells. You will under- stand also that each of the four hundred thousand million cells that are estimated to be in the human body is alive; that each must have food and oxygen and all the things that the body as a whole needs ; that the life of the body is the sum of the life of all its cells. When we study how to keep the body in health, therefore, we are only study- ing how to keep the cells in health ; for health means that the cells are in good condition, and sickness i^j / means that there is trouble among / ; ^^JL^/ the delicate little parts of which the body is built. The cells bathed by lymph. We have said that the cells of the body are built together as stones are built FIGS. 17 and 18. On the a walL Y OU Would not, how- right is shown a nerve cell from the brain; on the ever, have a correct idea of the left, a muscle cell from structure of the body if you did not the stomach. J understand that all among our cells there are spaces and openings, and that these crevices are filled with a liquid which escapes from the blood. This liquid is called the lymph, and the cells are sur- rounded by it and bathed in it, as a fish is bathed in the water in which it swims. Only to a very limited extent is it true that we are dry-land animals ; for the living parts of our bodies spend their lives under water as truly as do the fishes of the sea. Pure lymph necessary to the health of the cells. If you had hundreds of small fish in a pail of water, you would be compelled to take great care in keeping the THE HUMAN BODY AND ITS CELLS 13 water fresh and^in feeding them, lest they should die. So with the cells crowded together as they are in our bodies, it is necessary to keep the lymph pure and clean and to supply it with the food and oxygen that the cells need. We therefore have a stomach and other organs for preparing food for the cells ; we have lungs for taking in oxygen and for breathing out the waste car- FlG. 19. As clean water is necessary for the health of the fish, so is pure lymph necessary for the health of the cells. bon dioxid; we have kidneys for taking other poison- ous wastes out of the body ; and we have many other organs, each of which does its part in keeping the lymph rich and pure for the cells. When these organs do their work, our cells are like fishes living in pure, clean water where there is an abundance of food, and we are strong and well. If any organ fails in its work, either the cells will lack something that they need or the lymph in which they live will become impure, and the body will fall ill. Pure and rich lymph is necessary for the health of the cells. 14 PRIMER OF PHYSIOLOGY Keeping the human machine in repair. From what you have now learned, you will understand that your body is a machine of many parts. You will understand also that you are in charge of this machine, and that the length of time it will last and the amount of time it will be laid up for repairs depend on the care that you give it. In this book we shall study how the body is built and how it works ; for no one can care intelligently for a machine that he does not understand. QUESTIONS Of what is a plant composed? Describe a cell. Where does the young plant within a seed come from? Name the parts of a flower. What is pollen? Why do bees visit flowers? What do they do for flowers? What grows from the pollen grain when it is placed on the pistil? What is fertilization? Describe the growth of the egg. From what does the human body start? Of what are all the organs of the body built ? Name some of the different kinds of cells and tissues in the body. What do the cells of the body need in order that they may live? What is meant by health? by sickness? What fills the crevices among the cells? What is lymph? What kind of lymph is necessary to keep the cells in health? What organs prepare food for the cells? What organs take in oxygen? What organs give off wastes ? What happens if any of these organs fail in their work ? SUGGESTIONS TO THE TEACHER If possible, secure a compound microscope and allow the pupils to examine cells. Cells scraped from the inside of the cheek or lip, or the living skin from an inner layer of an onion, may be used in demonstrating cell structure. Prepared longitudinal sections of a growing root or stem tip show not only the cells, but their differentia- THE HUMAN BODY AND ITS CELLS 15 tion into tissues. Make clear the point that bone, cartilage, and connective tissue are built by the cell depositing dead materials about themselves, and that the living cells constitute only a small part of these supporting tissues. Identify parts in a simple flower; demonstrate pollen under a microscope. The pollen grains may be made to germinate by placing them in a solution of sugar and water (a 5 per cent to 40 per cent solution, according to the kind of pollen used). Have the pupils plant sunflower seeds in pots. Select two equally vigorous plants ; give one plenty of light and water, and set the other in a dark corner of the room and allow the soil to become dry. Note the difference in the appearance of the plants and call attention to the fact that the human body, like plants, is dependent on environment. Statistics show that for each death in a community there are on an average about two years of sickness. From local vital statistics have the pupils compute how many years of sickness are annually ex- perienced by the people of your city and state. The economic loss from preventable disease is estimated at $16 per year for each inhabitant of the United States ; compute the yearly loss to your city and state from this cause. Borrow compound interest tables from a bank and have members of the class find what sum the average American citizen would have to his credit at 20 and 60 years of age if this waste could be stopped and the money in- vested at 5 per cent compound interest. CHAPTER THREE THE FRAMEWORK OF THE BODY ANY one looking at the solid walls of a tall building would naturally suppose that these walls carried the weight of the great structure above them. As a matter of fact, the building has a steel framework which sup- ports it and braces it in time of storm, and the walls do not bear even their own weight. This is shown by the fact that the workmen often finish a portion of the wall many stories above the ground, before they build in the parts that connect it with the earth. The important thing in sup- porting the building, therefore, is the hidden framework which out- lines the shape of the building and carries its weight ; it is not the walls, which are a mere covering hanging on the framework. The skeleton. The human body, F,G. =0. The weigh, of Hke a g r6at Aiding. haS a frai e- the building is carried by work which gives the body its shape the steel framework/ and prov id eS Support for it. This framework is composed of 206 bones. All the bones taken together are called the skeleton. In addition to supporting the body, the bones protect delicate organs like the brain and heart, and make it possible for the muscles to move the different body parts. Feel your wrists, your sides, your cheeks, or almost any part of your body, and you will find the bones under the skin and soft flesh. We shall now 16 THE FRAMEWORK OF THE BODY IJ cranium skull clavicle sternum humerus spinal column pelvic bone sacrum coccyx carpal bones metacarpals phalanges tarsal bones metatarsals ^phalanges FIG. 21. The skeleton. 1 8 PRIMER OF PHYSIOLOGY study the more important bones of the skeleton and the way in which these bones are joined to make a framework for the body as a whole. The spinal column the center of the skeleton. The backbone, or spinal column, is the center around which the whole skeleton is built. Not only does it run up the back and stiffen and support the trunk, but it also carries the head on its top, and it has the bones of the chest and the bones of the hips attached to it. It is composed of many short bones, an arrangement which gives it a great number of joints and enables it to bend freely and easily in any direction. Each bone of the spinal column is called a vertebra (plural, vertebra}. Five of the lower vertebrae are joined to make one large, solid bone which is called the sacrum. Below the sacrum there are three or four small vertebrae which form a little tail-like structure, the coccyx, on the end of the spinal column. FIG. 22. The skeleton of the The gkull The skeleton of the head and trunk. head, or skull, is composed of the fourteen bones of the face and of eight bones which make a strong box (the cranium) to protect the brain. In the skull of a little baby there are places where the bones THE FRAMEWORK OF THE BODY 19 have not completely covered the brain. A baby's head, therefore, needs to be protected carefully from blows. The ribs and sternum. The ribs are twelve pairs of slender bones which curve around the chest and protect the heart and lungs. At the back they are attached to the spinal column. In front, the seven upper pairs are joined to the breast-bone, or sternum, and the next three pairs are hung from the ribs above. The two lower pairs have their front ends free, and are called floating ribs. The bones of the shoulder. The shoulder has two bones, the collar-bone, or clavicle, and the shoulder blade, or scapula. The scapula is a flat bone which lies oh the back of the shoulder. It is fastened to the spinal column and ribs, and at its outer end has a socket for the head of the arm bone. The clavicle has its inner end attached to the sternum ; its outer end is propped against the point of the scapula, which it supports. When the clavicle is broken, as by a fall, the shoulder drops forward and downward. The pelvis. The pelvic or hip bones are two large, widespreading, flat bones that can easily be felt in the sides. They are firmly joined to the sacrum at the back and to each other in front. With the sacrum, these bones form the bowl-shaped pelvis, which gives support to the organs that lie in the lower part of the cavity of the abdomen and also furnishes a solid framework to which the legs are attached. The bones of the limbs. Each limb has in it thirty bones, and the bones of the arm and leg are very similar. The thigh has in it a great bone called the femur, and the arm has in it a corresponding bone called the humerus. In the leg below the knee there are two 20 PRIMER OF PHYSIOLOGY FlG. 23. From an X-ray photograph of a broken forearm and a wrist. The crosses show where the bones are broken. long bones, the tibia and the fibula, and in the forearm there are two similar bones, the ulna and the radius. In the wrist we find a group of small bones (the carpal bones), and in the ankle is another group of small bones (the tarsal bones). In the hand are five bones (metacarpals\ each bear- ing a finger, and in the foot are five bones (metatarsals), each bearing a toe. Finally, the fingers of each hand have in them fourteen bones {phalanges), and the toes have the same number of bones arranged in the same way. The arms and legs are built on the same general plan, but the wrist has one more bone than the ankle, and the elbow has no bone correspond- ing to the kneecap (patella) on the front of the knee. Bones composed of animal and mineral matter. A bone is composed of animal matter and mineral matter. The mineral matter is lime. The animal matter consists chiefly of tough fibers buried in the mineral groundwork of the bone. The animal matter gives the bone its toughness and keeps it from breaking. The mineral matter stiffens it and makes it able to bear the weight of the body. These statements you can prove for yourself by burn- ing one bone in the fire and soaking another in a weak acid. The first bone has the animal matter burned out of it and becomes brittle like chalk. The mineral matter is eaten out of the other bone by the acid, and the bone becomes limber like a piece of rubber tubing. You can easily imagine the difficulties you would be THE FRAMEWORK OF THE BODY 21 in if your skeleton lacked either the mineral matter which stiffens it or the animal matter which toughens it. Joints. Close your hand and watch your fingers as they bend. The bending is not in the bones themselves, but at the joints between the bones, and the advantage of having a jointed skeleton is that it makes movement possible. There are two principal kinds of joints in the body, ball-and-socket ; . . FIGS. 24 and 25. On the left is joints and Ilinge JOintS. I he shown the shoulder joint, an exam- former allow motion freely P le of a ball-and-socket joint. On the right is the elbow joint, an ex- m any direction; the latter ample of a hinge joint, allow motion only in two op- posite directions, as does a hinge. Good examples of ball- and-socket joints are found in the shoulder and the hip ; of hinge joints at the elbow, at the knee, and in the fingers. Cartilage and ligaments. The ends of the bones at the joints are covered with a smooth, white material called cartilage, which is kept moist by an oil that is secreted in the joints. This keeps down friction in the joints. Around the joints are many strong bands and cords of connective tissue called liga- ments. Their chief function is to tie the bones together, but they also inclose the joints so that the oil cannot escape. FIG. 26. The ligaments of the wrist. 22 PRIMER OF PHYSIOLOGY The treatment of sprains. When a joint is bent too far, the ligaments about it are either torn loose from the bones or broken. An injury of this kind is called a sprain, and a bad sprain is often more serious than a broken bone. The best way to prevent a sprained joint from becoming swollen and painful is to bathe it in hot water and to massage it, rubbing and stroking it in the right direction to send the blood and lymph back up the limb to the heart. Driving the lymph on in this way will lessen the swelling ; it will take the pressure off the nerve endings and so help to relieve the pain ; it will carry away the parts that die because of the break- ing and tearing of the ligaments ; and the fresh blood and lymph will bring a supply of oxygen and food that will hasten the building up of new ligaments. There is a widespread idea that a sprained joint heals most rapidly when it is given complete rest, but many who are skilled in treating sprains and dislocations insist that, if the joint can be properly supported, the injured member should be used as soon as possible, even when movement causes pain. The reason given for this treatment is that exercise helps to keep up a good circulation through the part and also lessens the danger of the new ligaments being formed so short that the joint will be left stiff after the injured tissues have healed. Dislocations. When a bone is thrown out of place, it is said to be dislocated. A few persons have joints so loosely tied together that a dislocation is possible with little or no injury to the ligaments, but usually in a case of dislocation the ligaments are badly torn and broken. In such a case, no one but a physician should be allowed THE FRAMEWORK OF THE* BODY 23 to try to put the bones back in place ; for an unskilled person may cause much pain and do great damage by pulling and twisting at an injured limb. Broken bones. When an arm or a leg is broken, it should be kept stretched out straight so that the sharp, broken ends of the bone will not cut the muscles, nerves, and blood vessels of the limb. If the person must be moved, wrap a pillow, coat, or blanket about the injured member, Vising; Sticks Or FlG ' 27 ' A broken limb banda S ed for moving the patient. something else stiff enough to keep it from bending, as shown in Figure 27. An injured person may be carried in a blanket, but a door, a cot, or other solid support is better. In lifting the person, take the greatest .care to keep the injured limb from bending sharply at the break. The two parts of a fractured bone are cemented sol- idly together by a jelly-like white substance which ap- pears on the broken ends and hardens. If the broken ends are not brought together, the fracture cannot heal ; and if the injured part is not properly bandaged, there is always great danger that the bone will be crooked or deformed after it has healed. The skeletons of old persons and of children. The bones of old persons have very little of the living animal matter in them. They therefore break easily, and be- cause they contain little living matter, a fracture in an old person heals very slowly or refuses to heal at all. 24 PRIMER OF PHYSIOLOGY Old persons, therefore, should be saved as much as pos- sible from climbing stairs and from doing other things that may cause them to fall. In little children, on the other hand, there is a small quantity of the mineral matter in the skeleton, and the bones can easily be bent into almost any shape. During the growing years, large amounts of lime are needed for building and hardening the skeleton, and in most cases of defects and deformities of the skeleton, the real trouble is caused by a lack of proper building materials or of other necessary substances in the food (pages 140, 141). Importance of caring for the skeleton in youth. Heavy lifting will cause the shoulders of a child to droop for- ward, making him round-shouldered ; making children sit with the feet hanging over the edge of a seat will cause the legs to be bowed; tight clothing may bend in the ribs and cramp the organs within the body ; habitually sitting or standing in a stooped position will cause the skeleton to harden in an incorrect shape ; and many persons have the face and head slightly one-sided because when they were babies they were allowed to lie on one side more than on the other. The skeleton should have especial care in youth; for after the bones have hardened, it is difficult to change their shape. QUESTIONS Give three functions of the skeleton. Of how many bones is the skeleton composed? What is the function of the spinal column? What is one of the bones of the spinal column called? What is the sacrum, and of what is it composed? the coccyx? How many bones are in the skull? What is the cranium ? Why should a baby's head be protected from blows ? THE FRAMEWORK OF THE BODY 2$ How many ribs are there in the body? What is their use? How are they attached at the back? in front? Name and de- scribe the two bones of the shoulder. Describe the hip bones. To what are they attached at the back? in front? How many bones are there in each limb? Name the bones of the arm. Name the bones of the leg. Of what is a bone composed ? What is the use of the animal matter? of the mineral matter? How can this be proved? Name the two principal kinds of joints in the skeleton. Explain the kinds of movements they allow and give examples of them. What is cartilage? How is friction in the joints prevented? Give two functions of ligaments. What is a sprain ? What treatment should be given a sprain? Why? Why should a sprained joint be exercised? What is a dislocation ? Why should a broken arm or leg be kept from bending? How can this be done while moving an injured person? How does a broken bone heal? Why do the bones of old persons break easily and heal with difficulty? Why are the bones of little children easily bent? What mineral should be abundantly supplied in the diet of a child? Name six things that may cause the skeleton of a child to take an incorrect shape. SUGGESTIONS TO THE TEACHER Show the supporting skeleton of a leaf, using either an old leaf from which the softer tissues have fallen away, or one that has been skeletonized by boiling it in a 10 per cent potassium hydroxid (KOH) solution and gently scraping away the soft tissues. Use the dry bones of animals in teaching the skeleton ; decalcify the drumstick of a chicken, or any other slender bone, by soaking it in water to which acid (hydrochloric, sulfuric, or nitric) has been added. Such a bone, as well as a skeletonized leaf, may be preserved in alcohol or in a 50 per cent aqueous solution of glycerin. CHAPTER FOUR THE MUSCLES AND THE CARRIAGE OF THE BODY IT is a law of physics that a body at rest will remain at rest forever, unless some force sets it in motion by pushing or pulling on it. For ex- ample, it is the pulling and pushing of the hand that sends a thrown ball upward into the air. It is the pull of the earth that brings the ball down. It is the push of the gases that come from the explosion of the powder that sends the pro- jectile from a great gun. It is the pressure of the steam in the cylin- ders of an engine that sets the ma- chinery in motion and gives it the power to do work. Everywhere about us we see objects set in mo- tion, and in every case this is done by a push or a pull from an outside source. You can lift your arms; you can extend your legs; you can move your whole body from place to place. Something must be push- ing or pulling the different parts of the body to cause these move- ments. What is it that does this FIG. 28. The muscles. WO rk ? It is the muscles that are stretched upon the framework of the body. There are more than five hundred of these muscles, and they make up two fifths of the body weight. You are famil- 26 MUSCLES AND THE CARRIAGE OF THE BODY 27 iar with the lean meat in the body of an animal, and as this is muscle, you already know something of the appear- ance and texture of this " master tissue " of the body. The structure of a muscle. A muscle is composed of long, slender, fiber-like cells, which have the power of contracting, or shortening and thickening themselves. This action of the muscle fibers may be illustrated by allowing a stretched rubber band to come back to its natural condition; or you can get an idea of how the muscle cells change their shape by watching an earth- worm shorten and thicken its body as it crawls. The long, slender cells lie lengthwise in a muscle, and among them is a great network of connective tissue fibers, which ties the whole muscle together and attaches it to the skeleton. When the muscle fibers contract, they cause the whole muscle to shorten and thicken, as you can feel by laying your hand on your upper arm while the muscle draws itself together and lifts the forearm. How the muscles move the different parts of the body. The muscles stretch across the joints of the skeleton,, and when a muscle con- tracts, it pulls the bones together and causes a bending at the joint. Exactly how this is done you can best understand by a study of Figure 29. Tendons. In many parts Of the body long FlcT^. Showing how the muscles of cords of connective tissue the arm lift the forearm - called tendons attach the muscles to bones that are at a distance from them. This plan of placing muscles 28 PRIMER OF PHYSIOLOGY at a distance from the parts that they move, keeps mem- bers like the hand from being covered with large muscles, which would be in the way when delicate work is to be done ; at the same time it gives these members great strength and enables them to make many different move- ments. How the muscles move the body as a whole. You can- not stand on a ladder and pull the ladder up after you. muscle . FIG. 30. The muscles of the forearm and the tendons that move the fingers. You cannot sit on a chair and lift it. Yet you can move your whole body by muscles that are a part of your body. This is possible because you have a jointed skele- ton that allows you to thrust out parts of the body and push against outside objects. How this is done you can test understand through an experiment. Stand close to the wall, place your hands against the wall, and straighten out your arms. This pushes you away from the wall and moves your whole body. It is by this same method of pushing against some- thing that all the different kinds of locomotion in the animal kingdom are brought about. The fish, in swim- ming, pushes itself forward by striking its tail and fins against the water. The bird, in flying, forces itself onward and upward by beating against the air with its MUSCLES AND THE CARRIAGE OF THE BODY 29 wings. In walking and running, we drive ourselves forward by pushing with the feet against the ground. The muscles that support the body. Not only do the muscles move the body, but they support it when it is held erect. Muscles on the front and the back of the neck keep the head 'balanced on top of the spinal column. When we stand upright, other mus- cles hold the skeleton from bending at the ankles, knees, and hips, and at the joints of the spinal column. The most powerful muscles of the whole body are those of the back, which lie both in front of the spinal column and behind it. They are so impor- tant in the carriage of the body, that we shall study them in some detail. Muscles that support the head. The head is held from drooping forward by muscles which rise from the verte- brae of the trunk, from the ribs, and from the bones of the shoulder; they are attached to the bones of the neck and to the back of the skull. The action of these muscles can be illus- trated by attaching a string to the first joint of the finger, as is shown in Figure 32. Other muscles on the r f ^ , , , t 1 1 r FlG - 3 1 ' The front of the neck keep the head from that lie a i ong the bac k being drawn too far backward. of the spinal column. The muscles that support the trunk. The trunk is kept erect by muscles along the back of the spinal PRIMER OF PHYSIOLOGY column, by heavy muscles that brace the spinal column in front in the region of the waist, and by muscles in the walls of the abdomen. The action of these muscles we shall now take up separately. The muscles along the back of the spinal column rise from the sacrum and pelvic bones and run up the -back as high as the base of the neck (Fig. 31). Their func- tion is to keep the trunk from falling forward. Their action may be illustrated by attach- ing a cord to the finger and drawing it down the back of the hand, as is shown in Figure 32. The abdominal muscles are stretched between the pelvic bones and the ribs and sternum. When they contract, they draw the trunk forward and cause it to stoop, and they keep the body from being drawn over backward by the muscles of the back. By examin- / ing Figures 21 and 22, you will FIG. 32. illustrating the see h ow t h es e muscles are at- attachment and action of the muscles that support the tached and you Will readily Under- head and trunk, stand how they work in opposi- tion to the muscles of the back. The pull of the muscles along the back causes a forward curve in the spinal column at the waist. The spinal column is therefore supported in front in this region by strong muscles that brace it against the back muscles and keep it from bending too far forward. The lower ends of these muscles are attached to the femurs, which they lift in walking and running (Fig. 33). MUSCLES AND THE CARRIAGE OF THE BODY 31 The body balanced over the feet in standing. If, in stand- ing or walking, part of the body is too far forward or back- ward, some other part must be thrust out in the opposite direction to keep the balance over the feet. If the head droops forward, the spinal column between the shoulders will sink backward in a balancing curve. The same effect is produced by the shoulders fall- ing forward so that the weight of the arms pulls forward instead of downward at the sides. If the back bends inward at the waist, thrust- ing the abdomen forward, the up- per part of the body will be bent backward, throwing the chest up in front. Each part must be held in correct position, for one part out of position is sure to force other parts out of position also. The following rules may be helpful in keeping the body in correct posi- % tion in standing and walking : " Stand tali;' thrusting up the top of the head as high as possible. Walk as if you were hung by the top ofyozir head. FlG - 33 ' View from the front of one of the muscles Hold the Chin close to the neck. that keep the spinal column Press the back of the neck against from bending too far forward .j j, j at the waist. the collar button. Keep tJie abdomen in. If the upper part of the body leans too far backward, so that the heels pound in walking, sway the body for- ward at the ankles zintil the chest is over the toes. PRIMER OF PHYSIOLOGY In walking turn the toes in. Health and vigor are most important in acquiring a correct carriage, for if the muscles that hold the body upright lie weak and slack on the skeleton, they must all the time be forced to do the work that they ought to do naturally and without effort. Mistakes made in trying to secure an erect carriage. When the head droops forward, the mistake is often made of trying to bring it to an upright position by pulling the shoulders back. The true remedy is to tighten the muscles along the back of the neck and bring to an upright position the upper part of the spinal column, on which the head rests. Another mistake commonly made is to throw the head and chest back, and at the same time allow the back to be bent in at the waist and the abdomen FIG. 34 . The vertical line pos- to be thrust forward. In this turetest. (After chart supplied case, again, the remedy is to ^courtesy of American Posture straighten the curye in the spinal column. The muscles that lie along the front of the spinal column in the abdominal region are attached by their lower ends to the bones of the thighs, and one of the exercises that is practiced in strengthening them is to lie flat on the back and draw the legs up toward the body. Walking, running, and hill climbing also exercise and strengthen these muscles. MUSCLES AND THE CARRIAGE OF THE BODY 33 A third mistake often made is to try to bring the shoulders back by throwing the entire upper part of the body backward. The shoulders should be drawn back without moving any other part of the body, by pulling the scapulas flat down on the back. The vertical line test of posture. One test of posture FIGS. 35, 36, 37. The figure in the center shows correct posture ; the head, neck, and trunk form one continuous vertical line. On the left, the head is too far forward, which causes the spinal column to bend backward between the shoulders and forward at the waist. On the right, the shoulders have been drawn up, the back bent inward at the waist, and the whole upper part of the body thrown too far backward. In the figures on the left and right the head, neck, and trunk form a zigzag line. (After chart supplied by courtesy of Ameri- can Posture League.} that is in use in many schools is called the vertical line test. If a vertical line is dropped from in front of the ear to the forward part of the foot, 1 the long axis of 1 By forward part of the foot is meant any point from the ball of the foot back to the middle of the arch. The place where the line falls on the foot varies somewhat in different persons. 34 PRIMER OF PHYSIOLOGY the head, neck, and trunk will, in correct standing position, be parallel to it (Fig. 34). If the position is incorrect, the line through the axis of the body will be zigzag and not a straight vertical line. The test can be made by holding a pole in the upright position, as is shown in Figure 34. The vertical line should pass just in front of the knee and in front of the shoulder. When the trunk, head, and neck are held upright, a vertical line drawn through the middle of the tip of the shoulder should pass through the ear or behind the ear. If this line passes in front of the ear, the shoulder is too far forward. The foot and the carriage of the body. Of the first million drafted men who appeared at our army canton- ments in the World War, more than 175,000 had flat feet, and in 1917 more men were discharged from the service for flat feet than for any other cause, except pulmonary tuberculosis. Since deformed or painful feet make a good carriage of the body impossible, and since most foot troubles are due to shoes, we shall take up in this chapter the question of how the foot carries the body weight, and of fitting the foot with a correctly shaped shoe. The structure of the foot. The skeleton of the foot is composed of 26 bones which are held to- gether by muscles and ligaments. FIG. 38. The United States Army shoe. Improper shoes cause so much foot trouble that one United States Army surgeon has suggested that as a measure of military pre- paredness all shoes should be manufactured over lasts ap- proved by the government. It is especially important that the feet of children be not deformed. MUSCLES AND THE CARRIAGE OF THE BODY 35 FIGS. 39, 40, and 41. From X-ray photographs taken during investigations made by the United States Army. Figure 39 shows a foot in a shoe supposed to follow the lines of the foot, and commonly regarded as sensible. Note how the bones of the third and fourth toes are curled under, and how the great toe is bent in toward the other toes. Figure 40 shows the unshod foot of a soldier standing on one leg and bearing his 4o-pound marching equipment. Note how the foot expands and lengthens under pressure. Figure 41 shows a foot in the United States Army shoe (Fig. 38). Note the free play of the toes. Lengthwise from the heel to the ball of the foot, the bones are built together in the form of an arch. There is also a cross arch in the foot behind the toes, similar to the arch in the knuckles of a closed hand. In walk- ing, the foot is moved through tendons that run down along the ankle from the muscles below the knee and are attached to the bones of the foot. The foot is also to a considerable extent supported and held from tipping over sidewise by the pull of these tendons from the mus- cles of the leg. Shoes that interfere with the work of the foot. The weight of the foot falls on the heel, on the great toe and the ball of the foot behind the great toe, and along the outside of the foot behind the little toe. The foot is, therefore, a tripod, and if anything interferes with PRIMER OF PHYSIOLOGY any one of its three points of support, it becomes very unsteady. FIGS. 42 and 43. Showing the arch of the foot, and how a high-heeled shoe props it up on end. A high-heeled shoe props the arch of the foot up on end, instead of allowing it to stand in its natural position. Shoes with heels that slant forward move the back point of support from the heel toward the middle of the foot and make walking very insecure and difficult. Shoes with pointed toes bend the great toe outward and interfere with the inner front point of support, causing the wearer to turn the toes out and tending to cause the arch of the foot to be turned over on its inner edge. 1 Tight shoes interfere with the outer point of support of the foot by keeping the bones back of the toes from springing down and spreading apart in a natural mariner and thus throwing part of the weight on the outside of the foot. All this causes tired and painful feet, and makes walking difficult and fatiguing. 1 In the heel, the point of support is toward the outside, and the inner side of the ankle is in a great measure held up by tendons from the muscles in the calf of the leg. If for any reason the muscles of the leg are weak, the inner side of the ankle is not sufficiently supported by them and the arch of the foot is allowed to turn over on the inside. A wide, low heel built forward and out under the inner side of the ankle supports the foot at this weak point. MUSCLES AND THE CARRIAGE OF THE BODY 37 The points of a good shoe. A good shoe should have a wide, low heel, or for a natural foot, no heel at all. It should be straight along the inside so that it will not bend the great toe around toward the other toes. It should be long enough not to cramp the toes, and it should have a box in it high enough not to press on the toes and cause corns and ingrowing nails. The sole should be flat across, only slightly turned up at the toe, and wide enough that the outer border of the foot will not overhang it. It is especially important that shoes be roomy enough to permit the feet to spread and the toes to move in walking ; for if these movements are not allowed, the muscles of the feet will not develop and will lack the strength necessary to support the arches under the body weight. The position of the foot in standing and walking. In walking, the feet should be carried pointing straight for- ward ; for when the toes are turned outward, there is a tendency for the arch of the foot to be turned over so that it lies on its inner side. In standing, the toes may be turned outward somewhat, but only to a moderate degree. A person who " toes out " should practice turn- ing his toes inward as he walks. This position of the foot is very important in securing a correct carriage of the body. QUESTIONS How many muscles are there in the body ? What part of the body weight is muscle ? Describe the cells of a muscle. What is the function of the connective tissue in a muscle ? How does a muscle cause the skeleton to bend at a joint ? What is a tendon ? Of what 38 PRIMER OF PHYSIOLOGY advantage is it to have tendons in the body ? Explain how the muscles move the body in walking and in running. What function have the muscles in addition to that of mov- ing the body? What muscles support the head? Describe the three sets of muscles that support the trunk. What happens if in standing or walking any part of the body is too far backward or forward ? Give seven rules that may help in securing a good carriage of the body. Why is health important in securing a good carriage ? Explain three mistakes that are commonly made in trying to hold the body erect. Explain how exercising the legs keeps the spinal column from bending too far forward at the waist. Explain the vertical line test of posture. Is your own posture correct by this test? What test shows when the shoulders are in correct position ? How may they be pulled backward and what mistake should be avoided in attempting 'to do this ? How common were foot troubles among the drafted men during the recent war ? How many bones are there in the foot? How are the bones held together? Where are the arches in the foot ? Where are the muscles that move the feet in walking? Why are high-heeled shoes objectionable ? On what three points of the foot does the body weight fall ? What is the objection to narrow heels ? to heels that point forward ? to shoes with pointed toes ? to tight shoes ? Describe a good shoe. What is the correct position for the foot in standing ? in walking? SUGGESTIONS TO THE TEACHER Bancroft's The Posture of School Children (Macmillan) will be most helpful to the teacher. The American Posture League, No. I Madison Avenue, New York City, issues charts and literature on posture and gives the address of manufacturers of clothing, shoes, .furniture, and other articles that have been designed to meet the standards approved by the League. CHAPTER FIVE THE HEART AND THE CIRCULATION OF THE BLOOD IN New York City the street cars, automobiles, and wagons fill the streets ; the elevated trains roar over- head ; and deep in the earth the trains in the subway rush on and on in a procession that never ends. Nor is this all of the transportation sys- tem of the city ; for water and gas are piped underneath the streets to the homes of the people ; most of the wastes of the city are carried away by underground sewer pipes ; and the electricity which lights the city and runs much Transportation in New York City. of its machinery passes FlG - 44 silently along wires to the places of its use. In these and in many other ways the carrying problem of the city is solved. The carrying problem in the body. As a city is com- posed of a multitude of people, so is the body composed of a multitude of cells 4OO,cx)O,ooo,ooo, according to one estimate. Each of these cells must have food and oxygen, and each must get rid of its wastes. There must, therefore, be a transportation system in the body, and it must be one that is always in working order not one that breaks down and fails in its work from time to time. Transportation by water is more reliable than any other method that has yet been devised, and this is the method we find used in the body. 39 40 PRIMER OF PHYSIOLOGY The carrying in the body done by the blood. All through the body there is a great system of tubes, or pipes, called blood vessels. Night and day the heart pumps the blood through these vessels. Everything that the cells need is dissolved in the blood and carried to them in the blood stream. Into this stream each cell gives off its wastes to be carried away. Thus all the carrying within the body is done by the blood, and the blood is kept in constant motion through the body by the heart. Arteries and veins. The blood in its movement, or circulation, through the body flows through the same channels again and again, always returning to the starting point, the heart. We have, therefore, two sets of blood vessels in the body, the arteries, which carry the blood from the heart, and the veins, which bring the blood to the heart. The large arteries which leave the heart send branches to the different 'parts. of the body. These branches divide into finer and finer branches, called capillaries, which run in among all the cells. Then the capillaries unite into small veins. The veins, like the creeks that form a river, keep coming together, until finally all of them are united into the great veins which carry the bkfod back to the heart. To understand how the blood passes from an artery into a vein, think of two trees standing with their trunks close together and their tops touching each other. Then imagine that the blood flows up the trunk of one tree, out into its branches and twigs, then on into the twigs and branches of the other tree, and down its trunk. If the blood should make a circuit of this kind through the trees, its journey would be like the one that it makes THE HEART AND THE CIRCULATION liver left auricle valves lung left ventricle intestine artery to leg FIG. 45. Diagram showing the circulation of the blood. Note the valves be- tween the auricles and ventricles and at the mouths of the great arteries that open out of the ventricles. 4 2 PRIMER OF PHYSIOLOGY when it passes out from the heart through an artery and returns to the heart through a vein. The heart. The heart lies in the chest with its point to the left of the center. Its walls are made of strong muscles, and within the heart are four chambers, or cavi- ties, two on each side. The two upper cavities are called auricles ; the two lower cavities are called ventricles. The action of the heart. The veins pour the blood into the auri- cles. Then the walls of the auri- cles contract and force the blood down into the ventricles. Next, the strong walls of the ventricles close in on the blood, and drive it out into the arteries and all through the body. After forcing FIG. 46. The heart. 11,1- . i the blood into th9 arteries, the walls of the ventricles relax, and for a moment the heart rests. Then again the auricles, contracting on the blood that has flowed in from the veins, .fill 'the ventricles, and the ventricles pump t'he blood on into the arteries. Place your hand on the left side of -your chest, and you will feel your heart move as its walls /close in on the blood and force it onward through the vessels. The valves of the heart. In every pump there must be valves to keep the liquid from flowing backward. The heart, like other pumps, is provided with these valve's;' 1; two 7 between the ^auricles arid % trYe v Vebtflcles, and two at the 'mouths of tne arteries to kee,p the blood THE HEART AND THE CIRCULATION" 43 from flowing backward into the ventricles when their walls relax and the chambers open after each beat. In VALVE CLOSED FlG. 47. A diagram of the right side of the heart showing the working of the valves. When the blood flows into the auricles and the ventricles relax, the valves of the heart are as shown in A. When the ventricles contract and the blood flows out into the arteries, the valves are as shown in B. Figure 45 you can study out where the valves are placed, and from Figure 47 you can understand how they prevent a backward flow of the blood in the vessels and in the heart. Tracing the circulation of the blood. Trace the circulation of the blood in Figure 45, and you will see that the heart is a double organ ; that the right side sends the blood on a short journey through the lungs and back to the left side ; and that the left side drives the blood into the arteries for a long journey through all the body and back again to the right side of the heart. The blood flows through the vessels very swiftly, making the journey through the lungs in about fifteen seconds, and the long journey through the body in less than a minute. FIG. 48. A diagram of a pump. Locate the valves and explain how they work. 44 PRIMER OF PHYSIOLOGY The blood composed of plasma and corpuscles. The blood is composed of a liquid part called plasma, and of millions of little cells called corpuscles, which float in the plasma. About nine tenths of the plasma is water. The remainder is composed of dissolved food and other materials that are needed by the cells, and of the wastes that come from the cells. The corpuscles are of two kinds, the red and the white. The red corpuscles are so abundant that there are millions of them in the smallest drop of blood. It is the red corpuscles that give the red color to the blood. The function of the corpuscles. As the blood passes through the lungs, it takes oxygen from the air that is breathed into the lungs. The oxygen is then carried through all the body and given up to the cells. ' This carry- ing of the oxygen is done by the red corpuscles. Like little boats floating in the blood stream, they take up their FIG. 49 Red blood loads o f oxy g en m t h e lungs, carry the corpuscles (A) and J & white blood corpuscles oxygen out through the body, unload ^- it for the hungry cells, and hasten back to the lungs for more of the oxygen which the cells must have. The importance of this work is shown by the fact that when the heart ceases to beat, or when a person is under water so that the oxygen is cut off from the lungs, the life of the body quickly comes to an end. The white corpuscles are larger than the red ones and are fewer in number. Their work is to kill the disease THE HEART AND THE CIRCULATION 45 germs that get into the body. This subject we shall discuss in a later chapter (page 237). The lymph. The blood capillaries are so small and so abundant among the cells that you cannot stick a pin into your tissues anywhere without breaking many of them and letting the blood escape. The capillaries have very thin walls, and as the blood flows through them some of the plasma es- capes and passes out into the spaces among the cells. This escaped plasma is the lymph, about which you have already studied in the chapter on the Cells (pages 12 is plasma that escapes through the thin walls of the small blood vessels. (Diagrammatic.) and 13). The lymph a middleman between the cells and the blood. In Figure 50 you can see how the cells lie among the capillaries, and how they are bathed in the lymph that escapes through the thin walls of these vessels. The cells, therefore, are not in the blood stream, but this stream, so to speak, merely passes by the house, and the cells must find some way of getting their supplies from the stream into the house. This is done through the lymph. As the red corpuscles pass along in the capillaries, the lymph plasma while corpusde .red, corpusde FIG. 50. The cells are bathed in lymph, which 46 PRIMER OF PHYSIOLOGY oxygen breaks loose from the corpuscles, passes out through the walls of the vessels into the lymph, and so reaches the cells. In the same way, the foods that are dissolved in the plasma make their way out into the lymph that surrounds the cells, and the wastes that the cells give off pass through the lymph into the blood and are carried away. The lymph acts as a middleman between the cells and the blood, passing the oxygen and food from the blood to the cells, and the wastes from the cells to the blood. The lymphatic vessels. Among the cells of the body there is, besides the blood capillaries, a system of fine, thin-walled lymphatic capilla- ries. These unite and form larger vessels, which finally empty into the veins of the shoulders. The lymphatic vessels act as a drainage sys- FIG. 51. Lymphatic vessels in tem f or fa the fingers. -....-, , , function ts to gather up and drain off the stale, impure lymph from among the cells and empty it into the blood. This allows fresh lymph to escape .among the cells, bringing with it sup- plies of food and oxygen. The lymphatic vessels of the greater part of the body unite in one great vessel called the thoracic duct. This runs up the back of the cavities of the abdomen and chest, and empties into the large vein in the left shoulder. The importance of caring for the heart. The respon- sibility of keeping the whole transportation system of the body in operation falls on the heart, which is usually about the size of the fist of the person to whom it be- THE HEART AND THE CIRCULATION 47 longs. Night and day, from birth until death, this little organ pumps away, giving a stroke oftener than once a second. We cannot replace an injured valve in it with a new one ; it could not stop long enough for that, even if we knew how to do it. If it be- comes overworked, or if it is poisoned by disease germs, there is no second pump to take its place while it rests and gets into good condition again. It is such a wonderful organ that usu- FIG. 52. Valves in an ally it gives us little cause for com- ^\^ K ^^ plaint; yet there are certain things three valves attached that injure the heart, and for our own h ' ke ^pockets to J the wall of the artery. good We OUght to know of these things When the blood starts and avoid them. We shall therefore to flow backward into . . the heart, it catches in mention at this time some of the points the pockets, which then that are important in the care of the swing out and close the opening into the heart. heart. The heart injured by disease germs. By far the most common cause of trouble in the heart is disease germs. In diphtheria and scarlet fever the nerves and the muscle cells of the heart are so damaged by the poisons produced by the germs, that even in the mildest cases of these diseases, physicians frequently forbid the patient to sit up in bed, because they fear the effect of the strain on the heart. Furthermore, the heart is often so poisoned by an attack of one of these diseases that the nerves and muscle cells never recover, and the heart is left weak for life. In other diseases, such as pneumonia, rheumatism, and influenza, the germs themselves attack the valves and cause them to shrivel and harden, so that they allow the blood to leak back- 4 8 PRIMER OF PHYSIOLOGY ward, and again the heart is damaged for life. As much as possible, therefore, we ought to avoid all these germ diseases, the catching diseases which are so com- mon, and which people often carelessly give to each other. After an attack of one of these dis- eases, hard exercise should be avoided until the heart has had time to regain its strength. Too much exercise injurious to the heart. When the muscles are working, they need more food and oxygen and give off more FIG. 53. A wastes than when they are at rest. The valve in a heart must therefore pump the blood more veins have swiftly through the body when we use the muscles. This you can prove for yourself ward when pres sure valves in them to prevent the blood from by noting how much harder and faster your flowing back- heart beats after running or after doing other hard work. Indeed, when we take hard and comes on the long-continued exercise, it is -usually the your 5 finger heart that becomes tired first of all, although down a vein we may not feel it. There is danger, therefore, of overworking the heart, especially at that time of life when the boy or girl is entering manhood or on your fore- arm, and little knots will stand out on the vein at the points where womanhood and the body rapidly increases "* in size. When overworked, the heart, like any other muscle, at first enlarges, and then, if the overworking is kept up, becomes weak and flabby. This condition of the heart is called "athletic heart." If a person whose heart has been injured by overexercise takes a long rest, going to bed, if neces- sary, his heart usually recovers. He ought, however, to take care not to force his heart into this condition. THE HEART AND THE CIRCULATION 49 Proper and improper exercise. Do not keep on at any heavy work or hard game until you are exhausted. Do not play tennis all day. Do not spend a whole Saturday afternoon playing football. Remember that a baseball pitcher needs a stout heart as well as a strong arm, and that, for the sake of both your arm and your heart, you should not stay in the pitcher's box a whole half-day at a time. Do not enter long Mara- thon races that are intended for men and not for boys, and do not get on your bicycle and ride at a fast pace, hour after hour, up hill and down. You should under- stand, however, that it is only overwork that you are being cautioned against, and that both moderate exercise and severe exercise taken for short periods, are bene- ficial to the heart, as well as to other parts of the body. Tobacco injurious to the heart. Tobacco sometimes damages the heart until it has a quick, weak, and flut- tery beat. This is a serious ailment, but usually, if the tobacco is given up, the heart seems in time to recover. Coaches and trainers will not allow athletes to smoke, because smoking weakens both the heart and the other muscles. The question of the effects of tobacco on the body we shall discuss in more detail in a later chapter (page 197). The heart injured by headache remedies. A number of drugs commonly used (among them phenacetin, ace- tanilid, and antipyrin) will check a headache. The prac- tice of taking these drugs for headaches and colds is dangerous ; for they all weaken the action of the heart, and their continued use will bring on heart disease. They should be taken only when prescribed by a physi- cian, and no good physician will prescribe them often 50 PRIMER OF PHYSIOLOGY for the same person; for treating a headache in this way is not finding and removing the cause of the trouble, but drugging the body so that the pain will not be felt. The effects of alcohol on the heart and blood vessels. Alcohol causes the walls of the blood vessels to become weak and brittle. For this reason, apoplexy, which is caused by the bursting of a blood vessel in the brain, is more common among users of alcohol than among abstainers. Alcohol often weakens the heart by caus- ing its muscle cells to change to fat. In many beer drinkers there is the additional trouble that the work- ing cells of the heart are buried in a great mass of fat that must be lifted and moved every time the heart beats. When one realizes that in germ diseases every- thing depends on the heart's keeping at work until the body has had time to overcome the germs that are attacking it, the disastrous effects of alcohol are more easily understood. In pneumonia, especially, when it is a great task for the heart to drive the blood through the congested lungs, and in diseases in which the heart is weakened by the poisons from the germs, it is most important that the full power of this organ be saved for the ordeal which it must undergo. Statistics from a hospital in a city where excessive beer drink- ing is very common, show that 1 6 per cent of all deaths in the hospital were due to "beer-drinker's heart." Digestive troubles and the heart. When the digestive organs are out of order, the stomach sometimes becomes filled with gas and presses on the heart, causing a most uncomfortable feeling and a pounding and irregular beating. The digestive system, of course, should be THE HEART AND THE CIRCULATION- 51 given proper treatment in cases of this kind, but if this is done, there need be no alarm about the heart itself. QUESTIONS What must be carried to the cells and away from them? How is this carrying done? What is the movement of the blood through the body called? What is an artery? What is a vein? What is a capillary? How does the blood pass from an artery into a vein? Describe the heart. Explain how the heart forces the blood through the body. Where are the valves in the heart and what is their use? Trace the circulation of the blood from the right auricle back again to the right auricle. Of what is the blood composed? Of what is the plasma composed? What is the function of the red corpuscles? of the white corpuscles? What is the source of the lymph? Ex- plain how the lymph acts as a middleman between the cells and the blood. Describe the lymphatic vessels. What is their function ? What and where is the thoracic duct ? Why is the care of the heart so important? What is the most common cause of injury to the heart? How does over- exercise affect the heart? At what age is the heart especially likely to be injured by overexercise ? Name some games that put a great strain on the heart. What effect has tobacco on the heart? Name some drugs that are commonly used as headache remedies. What effect have these drugs on the heart? How do they relieve a head- ache? What effect has alcohol on the blood vessels? What causes of death are especially common among drinkers on account of this effect of alcohol on the vessels? What effect has alcohol on the heart? When is the bad effect of alcohol on the heart especially likely to show itself ? What effect does indigestion sometimes have on the heart ? 52 PRIMER OF PHYSIOLOGY SUGGESTIONS TO THE TEACHER If possible, secure a glass model of a pump, such as is commonly found among the equipment of an elementary physical laboratory, and demonstrate the action of the valves. Allow the pupils to ex- amine a drop of blood under the microscope. Additional matter on the topics discussed in this chapter and in many of the other chapters in this book will be found in Human Physiology, the most advanced book of the series. An examination of the diagram on page 234 will show that heart disease is one of the great causes of death. It is now generally accepted that practically all cases of heart disease (as well as cases of rheumatism, Bright's disease, and disease of the arteries) are caused by germs. Usually these germs are slow-growing races of streptococci, and often they have a permanent breeding ground in the tonsils, at the roots of teeth, in the bones of the face, or in some other part of the body, and are carried from these " foci of infec- tion " to the heart and other organs. In overcoming these slow infections, a hygienic life is of great importance, but treatment of the teeth or other infected part is often necessary. The relation of these chronic infections to the general health should be brought to the attention of the class during the study of later chapters. CHAPTER SIX RESPIRATION FILL a bottle with boiled water and one with unboiled water, and arrange growing beans in them, as is shown in Figure 54. The bean with its roots in unboiled water will grow for a consid- erable time as long as the mineral mat- ter in the water will provide it with food materials. The roots of the plant in the boiled water will quickly die and the whole plant will then wither, because the roots no longer send the water up to the leaves. Why is it that the roots in the boiled vvater die ? The answer is simple. The boiling of the water drives the oxygen out of it, and without oxygen the cells of neither plants nor animals can remain alive. The object of respiration. The first object of respiration is to take oxygen into the body. Of food, we have enough stored in the body to maintain life for a number of days, or, in some cases, even for several weeks. As to oxygen, however, the body leads a hand-to-mouth existence ; for though the air is more than one fifth oxygen, there is not enough of this gas in the body to keep us alive for more than two or three minutes after breathing has stopped. While we sleep, there- fore, "we must keep on breathing in oxygen; sit as quiet as we may, we must still keep on taking it in ; and when we walk or run, we do it taking in oxygen as we go. The second object of respiration is to give off carbon 53 F1G ' 54 PRIMER OF PHYSIOLOGY dioxidfrom the body. Carbon dioxid is a waste gas that is all the time being formed in the cells and carried by the blood to the lungs, to be breathed out into the air. It is formed not only in the body, but where wood, coal, oil, or gas is burned, and it is sometimes found in coal mines, where it is known to the miners as "choke damp." FIG. 55. The chest, showing the position of The Cavity Of the the heart and lungs. the chest contains the heart and the lungs. This cavity is inclosed by the ribs and sternum, and is separated from the abdominal cavity below by a thin cross-parti- tion called the diaphragm. In breathing, the chest cav- ity is enlarged by lifting the ribs upward and outward, and by pulling the diaphragm downward. The trachea and the lungs. The trachea has in its walls stiff rings of cartilage that hold it open so that the air can pass freely through it to and from the lungs. At its base the trachea divides and sends a great branch to each lung. Within the lungs these branches divide again and again, until finally they end in little, thin- walled air sacs. The branches of the trachea are called the bronchial tubes, and the lungs have a light, spongy texture because they are composed chiefly of these tubes and of the air sacs in which the tubes end. The changes in the air in the lungs. The walls of the RESPIRATION' 55 air sacs are very thin, and great numbers of small blood streams constantly flow through the capillaries in them. The oxygen of the air that we take into the lungs passes into the blood through the walls of the sacs, and trachea lung air sacs bronchial tube FIG. 56. The lungs. the carbon dioxid that is in the blood passes out into the air that is in the sacs, and is then breathed out of the lungs. The air in the lungs, therefore, loses oxygen and gains carbon dioxid, and the blood takes in oxygen and gives up its carbon dioxid. PRIMER OF PHYSIOLOGY These changes take place very rapidly in the lungs, for the capillaries are so numerous that they cover more than one third of the surface of the air sacs, and all the blood in the body goes through them in a little over a minute. Injury done to the respiratory organs by dust. Nearly all the diseases of the air passages and lungs are caused by germs. Dust wounds and injures the FIG. 57. A s m a 1 1 delicate lining of these parts, and makes bronchial tube and the . air sacs in which it it easy for germs to gain an entrance ends - into the tissues. The majority of work- men in certain industries, such as metal grinders, pot- ters, and workers in cotton and woolen mills, die of pneumonia, tuberculosis, and other respiratory diseases. This is due to the multitude of tiny wounds continually being made in the walls of the air passages by the sharp dust and fine fibers with which the air of many factories and mills is laden. Much can be done to make dusty trades more healthful by using water in operations where dust is formed, by hoods and air blasts that suck up the dust from machines, and by the FlG - 58. A workman wearing a mouthpiece to protect himself workmen wearing appliances from dust . (From a photograph tO protect themselves from the % the Massachusetts State Board dust. Sweeping without raising a dust. In many states RESPIRATION' 57 IJIfl illlSSStl dry sweeping of school buildings and of other public buildings is forbidden by law, because it stirs up great quantities of dust, which then remains floating in the air for hours. The best method of cleaning public buildings, as well as private homes, is the vacuum pro- cess. When this cannot be used, wet sawdust, a sweep- ing compound, or something else effective should be em- ployed to keep down the dust. One device that is sometimes used is a can attached to the handle of a broom and so ar- ranged that it keeps the broom moist with kerosene or water. FlG. 59. A dustless brush. The The floor brush shown in Fig- bac k of the brush is hollow and ure 59 is very satisfactory for is filled with kerosene, which ~. rc .. . slowly trickles down and keeps sweeping, and pararhn oil is the bristles moist while the sweep, extensively used in making up ing is being done, floor dressings and sweeping compounds. This oil may be purchased for ten cents a quart, or at a lower price in larger quantities, and it gives an excellent polish . to floors and furniture. Sawdust moistened with it makes a very satisfactory sweeping compound, and a cloth dampened with it is the best thing for removing dust from furniture and for cleaning doors. Gaseous impurities in the air. In many houses small quantities of gas are constantly escaping from the pipes, and often this leaking of gas is allowed to run on for weeks and months before the pipes are repaired. Breathing this gas, especially if it is water gas, is most injurious to the health. Another most harmful practice is the use of gas and oil stoves that have no pipes to 58 PRIMER OF PHYSIOLOGY carry away the fumes ; for it is ruinous to the health to breathe the poisonous gases that come from them. The effect of tobacco on the respiratory organs. To- bacco smoke is hot and irritating and often causes sore tongue and " smoker's sore throat." Undoubtedly these diseases sometimes lead to cancer, because any part of the tissues that is constantly irritated may develop into a cancer. When the smoke is inhaled into the lungs a sooty deposit which must certainly be injurious is left on the walls of the bronchial tubes. 1 When smoke is ex- haled through the nose it has a tendency to cause ca- tarrh and injures the sense of smell. The nicotin that is taken into the blood, either by partially paralyzing the nerve centers that control the breathing muscles, or by its effect on the muscles themselves, causes the shortness of breath with which every smoker who has tried to take part in athletic sports is familiar. QUESTIONS Why will a plant die if its roots are in boiled water? What is the first object of respiration? Why can a person live a long time without eating, but only a few minutes without breathing? What is the second object of respiration? What organs are in the cavity of the chest ? By what is the chest inclosed? How is the chest cavity enlarged in breath- ing? Describe the trachea and its branches. How do the bronchial tubes end ? Explain the changes that take place in the air in the lungs. 1 " Surely smoke becomes a kitchen far better than a dining chamber, and yet it makes a kitchen oftentime in the inward parts of man, soyling and infecting them with an oyly kind of soote as hath been found in some great tobacco takers, that after their death were opened." KING JAMES I. RESPIRATION 59 Why is breathing dust dangerous? What may be done to keep down dust in factories? How may buildings be swept without raising a dust? Why should leaks in gas pipes in houses be carefully looked after? Why is it injurious to use gas or oil stoves that have no pipes to carry away the gases? SUGGESTIONS TO THE TEACHER Have a pupil breathe through a glass tube into limewater. The white precipitate is calcium carbonate, which is formed by the union of the carbon dioxid with the calcium in the limewater. Call attention to the dust particles which may be seen floating in the air when a beam of sunlight penetrates a darkened room. Use all possible influence to have the school building swept and dusted in a sanitary manner. Call attention to the importance of hygienic industrial conditions and to the fact that, in selecting an occupation, the effect of the work on the health is as deserving of consideration as the wages that may be earned. CHAPTER SEVEN VENTILATION FIG. 60. Move your bed out into the open air if it is possible for you to do so. IN 1/58, during a rebellion of the native soldiers in India, one hundred and forty-six Englishmen were shut up overnight in a room that had but a single window. When morning came, only twenty-three of them re- mained alive. After the battle of Austerlitz, three hundred prisoners were crowded into a cavern. In a few hours two thirds of them were dead. Many other instances are on record of people who have perished when shut up in closets, vaults, or the holds of ships. Most persons have read of some of these instances, and practically every one takes care to keep out of places where he is likely to perish because his supply of air fails. 60 VENTILATION 6 1 It would seem, however, that many persons are like the kind-hearted old gentleman who could not bring himself to cut his dog's tail off all at once, and so cut off an inch each morning until the tail was gone ; for while these people object most decidedly to killing their bodies all at once with bad air, they do not seem to mind killing them a little at a time. Perhaps they do not realize what they are really doing, but the damage is constantly being done, nevertheless ; for they go to churches, lecture halls, and theaters where the air is so foul that it gives them headaches; many persons sleep in rooms with windows and doors so tightly closed that the sleepers must breathe the same air again and again ; children often cover their heads with the bedclothes and do not get a breath of fresh air all night long; and many schools and factories are so badly ventilated that the health and the working power of those in them are continually being undermined. The whole subject of ventilation is, therefore, of the very greatest importance, and in this chapter we shall take up the study of why we need fresh air and how to get it. Enough oxygen usually in the air. About one fifth (21 per cent) of the air is oxygen, and the remainder is nearly all nitrogen. The nitrogen is not used in the body, but is simply breathed into the lungs and breathed out again unchanged. The oxygen is taken into the blood and carried through the body to the cells. Air that has been breathed once has lost about one fourth of its oxygen, and where people are crowded together as the English were in the " Black Hole of Calcutta," the oxygen in the air becomes exhausted. We can live, 62 PRIMER OF PHYSIOLOGY however, on 15 or even on 12 per cent of oxygen, and under any ordinary conditions the trouble with the air we breathe is not with the amount of oxygen in it. The carbon dioxid problem. Carbon dioxid is given off into the air from the lungs, and too much of it in FIG. 61. An outdoor lesson in geography. (After 'Ayres.) the air is poisonous to us. It was long supposed that this was the chief trouble with indoor air, that the paleness and lack of strength noticed in those who lived without .good ventilation were due to carbon dioxid poisoning. All our rules for ventilating buildings have been laid down with the idea that we must bring in large quantities of fresh air (3000 cubic feet per hour for each person) to keep the carbon dioxid from be- coming too abundant in the air that we breathe. This is still a good rule to follow ; for it has not yet been proved that breathing large amounts of carbon dioxid week after week is not injurious to the health. Re- cently, however, it has been proved that in ventilation VENTILATION other questions besides the amount of carbon dioxid in the air must be considered. Dry air injurious. In rooms heated by stoves, radi- ators, or hot-air, systems, the atmosphere becomes too dry, unless special arrangements are made for moistening it, drier, in fact, than is the air in the Desert of Sahara. Since dry air quickly evaporates the sweat from the skin and cools the body, people often heat such rooms up to 75 or 80 de- grees, because they feel cold at lower temperatures. Living in a hot, dry atmosphere of this kind is injurious to the eyes, and it makes people subject to colds; it FIG. 62. A home-made causes nervousness, also, and a child humidifier - a P aii with a strip of cloth arranged in a dry, overheated schoolroom is for feeding the water up h eva P rate restless and has difficulty in keeping his mind on his work. Vessels of water should therefore be kept in furnaces and on stoves and radiators; and in school buildings heated with hot air, arrangements should be made to moisten the air be- fore it is discharged into the rooms. It is economy to give attention to this point ; for moist air feels as warm at 65 degrees as dry air at 75 degrees ; in some school buildings as much as a 10 per cent saving in fuel has followed the installation of devices for moistening the air. A moist atmosphere and overheating. When the tem- perature of moist air rises much above 70 degrees, it gives us a hot, suffocating feeling, similar to that 64 PRIMER OF PHYSIOLOGY which one has on a warm, sultry summer morning. The explanation of this is that the moisture in the air keeps the sweat from evaporating, and there is a layer of hot, wet air surrounding the body like a shell. In crowded buildings, therefore, where the air is wet from many people breathing it, a proper temperature is very im- portant. It ought not to fall below 65 degrees, for then the people will be chilly ; and it ought not to run above 70 degrees, for then the people will become hot and un- comfortable, some of them will develop headaches, and many of them will catch cold when they step out into the cool outside air. The necessity for motion in the air. In hot weather, and in warm and wet indoor atmospheres, it is most important that there be air currents to break up and blow away the hot, moist air blankets that surround us. How important such air currents are, is shown by an experiment that was carried out in England. In this experiment, a group of students were closed in a small room and watched through a glass in the door. At first they were laughing and joking, but soon they began to show signs of distress. Formerly it would have been concluded that they were suffering from a lack of oxygen or were being poisoned by carbon dioxid. The real trouble, however, was the overheating and the mois- ture in the air, as was proved by the fact that when an electric fan was started in the room, the students be- came comfortable again without the introduction of fresh air. Setting indoor air in motion. In public buildings the air often becomes close and the temperature rises after meetings have been in progress for some time. In such VENTILATION cases a great deal can be done towards keeping the audience comfortable by opening a few windows, so that part of the heated air will escape and currents will be set up through the building. In the Chicago schools, every window in every schoolroom is thrown wide open three times a day to allow the wind to sweep out the stale air in the buildings and to break up and blow away the envelopes of moist air from about the bodies of the pupils. Practices like this should be followed every- where. A few minutes de- __ \ voted to flushing out a school- // / / / / // room and going through a few FIG 63. A window board helps resting and stretching exer- to ventilate a room, cises are by no means to be counted as lost, for the pupils return to their work with new vigor and zeal. It is well to understand also that the health of many workers could be improved and their working power greatly increased by providing them with electric fans during the hot summer weather. Many factory owners who have put in ventilating systems have found "that the increased amount of work accomplished by the laborers in the factory far more than paid the cost of putting in and operating the system. This is what we should ex- pect, for every one knows the difficulty of working in an overheated, stifling atmosphere, and how bracing and invigorating a current of air is on a hot, oppres- sive day. 66 PRIMER OF PHYSIOLOGY Disagreeable odors in crowded rooms. In crowded and heated rooms, odors always arise that cause head- ache and a feeling of faintness in persons who are sen- sitive to them. A low temperature makes these odors much less noticeable, and a cur- rent of fresh air through the room not only sweeps away the FIG. 64. An open-air schoolroom in Sacra- odors themselves, but mento, California. The inclosed room is a i crk v^fr-^cV^c fl->^ used only in bad weather. people and destroys the effects of the odors on them. Persons who are troubled with symptoms of illness when they attend public meetings can sometimes escape the difficulty by arranging for a seat near a ventilator or window, or where a current of air from an open doorway will blow across them. It is probable that "crowd poisoning" is nothing but the effect of the overheating and of the odors that are usual in buildings where many people are assembled. Open-air schools. In Oakland, California, during the winter of 1910191 1, an open-air school was in operation. In this School the children did regular work, and they had no special feeding or rest periods. Yet during the first half year no child in the school failed to gain in weight, and the average gain was 3.70 pounds; in the regular school building the average gain was 2.36 pounds. The children in the open-air school were free from colds, while, as usual, the children in the indoor school at times suffered from them. Most noticeable of all, however. VENTILATION- 67 was the wide-awake, energetic way in which the open-air pupils kept at their work. Day after day they finished their tasks without becoming tired, and by the end of the year all of them had advanced one grade, several of FlG. 65. An outdoor classroom at Williamsburg, Virginia. When the children become tired indoors, classes are taken to this building for a recitation. There were only 20 days during the winter of 1911-1912 on which this outdoor classroom was not used. them had advanced two grades, and one boy had done two and one half years' work in the one year. In many places open-air schools have been established for sick children, with the idea of nursing them back to health rather than of advancing them in their school work. In these schools the pupils are fed and have long rest periods, and only light school work is done. Experience has shown, however, that in the open air the children throw themselves into the work so eagerly and their minds are so clear that even in outdoor schools that give only half the usual time to study, the pupils advance as rapidly as they do in an indoor school where they spend the whole day over their books. 68 PRIMER OF PHYSIOLOGY the Horace Mann Elementary School, Teachers College, New York. Why, then, should not boys and girls who are in good health, as well as those who are sick, be in schools where they can master their work with the greatest ease and at the same time build up their bodies by breathing out- door air ? The time has come when each community must an- swer this question. In mild climates and in warm weather, there is certainly no reason for going to the great expense of FIG. 66. Open-air classes held on the roof of trying to get the right kind of air indoors, when nature has filled all outdoors with exactly the kind of invigorating air that we need. Outdoor sleeping. In recent years thousands of out- door sleeping porches have been built in our country. Without a doubt the health is greatly benefited by passing in the open air the many hours that we spend in sleep. The only point that needs to be re- membered in moving outdoors is that the warmth of the body must be kept up ; that man moved into houses to protect himself from the cold and wet, and when he moves out of them again he must have clothing that will keep him warm and dry. If this point is looked after, the more time we spend outdoors the better. Therefore, move out into the outdoor air to sleep if you can, and if you cannot do this, open wide the windows of your bedroom and let the outdoor air come to you. VENTILATION" 69 QUESTIONS What two gases make up the greater part of the air ? Which of these gases is used by the body? Under what conditions may the oxygen supply of the air become exhausted ? What is carbon dioxid ? How much fresh air is supposed to be needed by each person in a building ? Why does dry air cause a sensation of chilliness ? What bad effects follow living in a dry atmosphere? Is there any method of moisten- ing the air used in your school building or in your home? Explain how it works. Why does one easily become overheated in a moist atmos- phere? Describe an experiment that proved the importance of keeping the air in motion. Mention some ways by which air currents may be set up in buildings. In what way have factory owners been repaid for the cost of installing and operating ventilating systems? What effects have the odors of crowded rooms on certain persons? What may be done to make these odors less notice- able ? Give an account of the open-air school at Oakland, Califor- nia. For what purpose are open-air schools used in many places? What advancement do the pupils in these schools make in their school work? In outdoor life what point must be kept in mind ? SUGGESTIONS TO THE TEACHER Give gymnastic exercises while the schoolroom windows are opened. Insist on the importance of the pupils putting their knowl- edge of ventilation into practical use in their home life. Perform for the class experiments with wet- and dry-bulb ther- mometers (consult Appendix of Human Physiology}. Bring out that because the skin is kept moist by the perspiration the body is com- parable to a wet-bulb thermometer, and that it is the wet-bulb rather than the dry-bulb temperature that is important in regulating the temperature of rooms. CHAPTER EIGHT ADENOIDS AND COLDS FIG. 67. Adenoids sap the strength so that any one who is suffering from them has very little chance of being the best athlete in the school ; they dull the mind so that the victim of them rarely stands at the head of his class. AMONG the most common of all the ailments that afflict the inhabitants of the temperate and frigid re- gions of the earth, are colds and certain other troubles of the nose and throat. These maladies, of course, are not so severe as many other diseases, but certainly they cause more inconvenience than all our other lesser sick- nesses combined. It is true also that they often weaken the body and lay the foundations for other serious diffi- culties. People lack the general understanding of these diseases that they ought to have, and in this chapter we shall therefore make a study of them. In order that we may do so more intelligently, we shall first consider the structure of the nose and throat. The chambers of the nose. The air passes through the nostrils into the nasal chambers. These long, nar- row passages are about three quarters of an inch wide ; 70 ADENOIDS AND COLDS -I FIG. 68. A cross-section of the nasal chambers, showing the bones (a, b, and c) that stand out in the pathway of the air. The mucous membrane lining the chambers is shown in white. they extend up into the head about as high as the level of the eyes, and they run back and open into the throat behind the mouth. They are separated from each other by a very thin, bony partition. On the outer wall of each chamber are three curved and rolled-up bones that stand out in the pathway of the air (Fig. 68). The whole interior of the nasal chambers is lined by the same skin-like mucous membrane that is found in the mouth and throat. This is kept moist by a sticky sub- stance called mucus. The air warmed and cleansed in the nose. The air in the nose comes in contact with the lining of the chambers, and is drawn in among the bones that stand out in the nasal passages. In this way the air is warmed, and the dust and germs in it are caught on the moist, sticky mucous membrane that lines the cavities and covers the bones. The function of the nose in respiration is to protect the throat and lungs from cold and from dust and germs. Troubles in the nose. Sometimes the thin partition between the two sides of the nose becomes bent so that it closes one of the nasal chambers; sometimes the bones in the nose enlarge until they interfere with the breathing and prevent the proper drainage of the nose; and in a considerable number of persons, swollen and over- grown portions of the mucous membrane, called nasal polyps, block the air passages. In all such cases, the PRIMER OF PHYSIOLOGY Eustachian tube soft palate position of adenoids tonsil obstruction in the nose ought to be removed by a physi. cian who understands how to do the work. If this is not done, the breathing will be interfered with continually, and colds and chronic catarrh are likely to be the result. The throat. The throat is a funnel-shaped cavity which curves backward and downward around the base of the tongue. At its bottom are two openings, one leading to the stomach and one leading to the lungs. In front, a little flap-like structure, the soft palate, hangs down from above and partly sepa- rates the throat from the mouth. Above and behind the soft palate are two openings which lead into the nose, and high up in the walls on either side of the throat are the mouths of the two Eustachian tubes, which are small passageways that lead to the middle ears (Fig. 69). In the walls of the throat are four tonsils, which we shall describe in some detail. The tonsils. One small tonsil lies in the back of the tongue ; one is high up in the back wall of the throat ; and the other two lie in the side walls of the throat. FlG. 69. The nasal passages, mouth, and throat. ADENOIDS AND COLDS Fi3. 70. A ton- sil. A part of the These structures are composed of loose, spongy tissue, and leading down into them are small openings, or crypts, which are formed by folding the mucous membrane down into deep little pockets (Fig. 70). Germs grow in these pockets and cause tonsillitis, a disease in which the tonsils are swollen and have matter in them like that found in boils. In many persons the tonsils are always infected with germs and become so swollen and enlarged that they block the throat and interfere with the breathing. The tonsil which is most commonly en- tonsil is cut away , , , ,, r to show a crypt. larged is the one in the back wall of the throat, and the spongy, swollen, whitish mass of soft tissue into which this tonsil changes is called adenoids, or adenoid growths. Usually, when adenoids are present, the other tonsils also are enlarged, but this is not always the case. The 'symptoms of adenoids. In moist climates one fourth of all the children may have adenoids. The most easily recognized symptom of them is mouth breathing. If the throat is entirely blocked by them and the tonsils also are enlarged, the mouth will be kept open so wide that any one will notice that the child is a mouth breather. If the throat is only partly filled, the child may keep his mouth open only a little, and the mouth breathing may not be noticed * all, except when the child has a \After Wingravc.) cold or is asleep. After the adenoids 74 PRIMER OF PHYSIOLOGY have been growing for some time, the upper teeth begin to turn forward ; the face is puffed out under the eyes ; the eyes have a strained look and are drawn down at the inner corners ; the lips thicken ; the upper lip shortens and is turned out; there is often a white line running down from the corner of the nose marking off the division between the cheek and lip; and the whole face has a dull, stupid look. FIG. 7 Adenoid In man y CaSeS f aden id growths, growth that has been the germs work their way up the Eusta- removed. One half ch j an tubes and cause earacne , which natural size. {After 1S an almost certain symptom of them. They also interfere with speech, and any one who " talks through his nose " or has difficulty in pronouncing his words clearly, probably has his nasal passages blocked by them. A child with this trouble usually snores, and in bad cases sometimes gasps and struggles for breath during sleep. Besides these symptoms of adenoid growths, there are certain other effects that often go with them. Sometimes children who have them are very restless and nervous, and are unable to keep their attention fixed on any one thing. Often they are stupid at their books and fall behind in their school work. Usually the digestion is disordered from swallowing the multitudes of germs that come, from the adenoid and tonsils. Often the chest is narrow and the child is undersized, some- times two or three years smaller than he should be. Another effect of adenoids, very noticeable in some cases, is a fretful, quarrelsome, and seemingly perverse disposition, a lack of self-control and a tendency to ADENOIDS AND COLDS 75 fly into a rage at the slightest provocation. This causes the victim to make trouble for his parents, for his teacher, and for all who have anything to do with him. The remedy for adenoid growths and infected tonsils. The only thing to do for adenoids and infected tonsils is to have them out at once. When performed by a skilled FIG. 73. Typical adenoid faces. surgeon this operation is not severe, and in thousands of cases it has resulted in an improvement in the condition of the child that is almost miraculous. One sixteen-year- old boy gained fourteen pounds in three weeks after hav- ing his adenoids and tonsils removed ; and it is a common thing for a child whose adenoid growths have been taken out to make a sudden increase in height and weight and to renew his interest in his school work. The evil consequences of waiting to outgrow adenoids. Usually, but not always, adenoids disappear by the time 76 PRIMER OF PHYSIOLOGY a person is grown. 1 It must not be thought, however, that their evil effects disappear with them ; for if the nostrils are not used in breathing, the nasal chambers and the upper part of the face do not grow as they should, and the person is left with narrow air passages, protruding upper teeth, a short, thick upper lip, and often with a catarrh and a swollen condition of the nasal mucous membrane that will remain with him for life. Neglected adenoids spoil the beauty of the face for all time, and it is estimated that three fourths of all deaf- ness is due to them. Any one who advises waiting to outgrow adenoids is giving the worst advice possible. They ought to be removed, and this ought to be done be- fore they interfere with the growth of the bones of the nose and face. Colds. Colds are caused by germs that live on the mucous membrane of the nose and throat. They may be divided into two classes, epidemic colds and chronic colds. Epidemic colds are caused by germs of a particu- larly virulent strain that are handed from one person to another until the disease sweeps the community. Most of us must either endure these colds or find a way to escape the germs that cause them no easy thing to do when people who have colds insist on shaking hands with us and leaving with us a few millions of the germs with which they are so bountifully supplied. Spraying the nose with something that will kill the germs often helps to check a cold in its early stages. 1 A case of adenoids has been reported in a child six weeks old and one in a man of seventy years. They are by no means to be thought of as a disease of children only, for many cases are found in persons up to forty years of age. ADENOIDS AND COLDS 77 A hot foot bath cannot kill the germs in the nasal pas- sages, but it helps to draw the blood away from the congested parts and assists in correcting the disturbances of the circulation that accompany a cold. It may also relieve to some extent the headache from which the victim of a violent cold suffers. A hot bath taken be- fore going to bed is even better than a foot bath for drawing the blood away from the congested parts. In chronic colds, the germs remain with the person all the time, growing only a little when he is in good health and offers a vigorous resistance to them, and springing into greater activity whenever the person gets his feet wet, becomes chilled, loses sleep, or does any- thing else that weakens his body and lowers its resist- ance to germs. A person with a cold of this kind is like a country invaded, but not conquered, by an enemy. At one time the inhabitants of the country drive back the foe and give themselves a breathing spell ; at an- other time the advantage is with those who make the attack. The patient's only hope of victory over his germ enemies is to build up his health until his body has suf- ficient fighting powers to drive them out completely. The following practices have been found important in giving the body strength for this work : Clearing out the nose and throat. Adenoids, enlarged tonsils, bent and enlarged bones in the nose, and any- thing else that prevents a free passage of the air through the nose and a free drainage of the mucus from it, turn the nasal chambers into splendid homes for countless germs. The battle against colds is a battle against germs, and we cannot hope to succeed if the enemy is intrenched behind fortifications. 78 PRIMER OF PHYSIOLOGY Getting enough fresh air. Experience with both consumptives and well persons shows that no one thing is so important as fresh air in giving the body the power to kill germs. Many persons suffer continually from colds because they live and work in buildings where the air is dry and overheated, and any one who wishes to free himself from a chronic cold must include fresh air in his plans. Keeping the bowels open. When refuse matter does not pass promptly through the intestines, it putrefies and produces poisons that break down the health of the whole body (pages 177-179). These poisons destroy the power of the body to resist germs, and they injure the nervous system so that the blood vessels are not prop- erly controlled. The feet of persons who are in this condition are therefore often cold while other parts of the body are congested with blood, and the circulation in general is not regulated as it should be. This disturb- ance of the circulation is in itself favorable to the growth of germs and makes the cure of a cold difficult. The remedy is to get the digestive system into good working order, and many persons recover from chronic colds when they do this (page 170). Taking cold baths. The practice of taking cold baths helps to give freedom from colds. Probably one way that it does this is by bringing out the white blood corpuscles that kill germs; for it is found that the white corpuscles are more abundant in the blood after a cold bath than before it. Another way that a cold bath helps is by teaching the blood vessels in the skin to open and close promptly. When cold strikes the body, these vessels ought to close and thus keep the ADENOIDS AND COLDS 79 blood in the inner parts where the heat of the body will not be lost. Then, when the cold is removed from the skin, the vessels ought to open and allow the blood to come to the surface ofNthe body. In some persons who are in bad health, the nervous system which governs these vessels does not control them properly, and the vessels in the skin may not close promptly enough to prevent the escape of the heat from the body; or, at the slightest feeling of cold on the skin, the blood vessels may shut up tight and gorge the inner parts of the body with hot blood, while the skin is left cold and shivering. 1 Cold baths help to train the vessels of the skin to open and close properly, and to keep the right amount of heat within the body. In beginning to take baths of this kind, intelligence and care are necessary ; otherwise much harm may be done (page 88). Drafts and colds. People are sometimes advised to pay no attention to drafts and to open the windows, no matter how cold the weather may be, because it is germs and not drafts that cause colds. Yet many persons know from their own, experience that sitting in a cold draft does cause them to sneeze, to feel chilly, and often to become actually sick. How can the idea that it is beneficial to the health to sleep where the wind will blow over you, be reconciled with the idea that a draft of cold air is dangerous ? If motion in the air is desirable, why not have as much of it as possible ? 1 It should be understood that in chills, such as we have in malaria, or at the onset of grip or pneumonia, the difficulty is that the blood has been driven to the inner parts of the body, and the skin, where our sense of feeling is, no longer is warmed by the blood flowing through it. There is no lack of heat in the body, for often a person has several degrees of fever at the same time that he is having a chill. X 80 PRIMER OF PHYSIOLOGY In the first place, it must be understood that drafts of cold air take the heat out of the skin, and that a person who is- exposed to them should have sufficient extra clothing to enable him to keep up his body heat. This keeping up of the body temperature is fundamental in the preservation of the health, for the resistance of the body to germs is weakened at once by the loss of too much heat. Much damage may be done by compelling school children who have been accustomed to hot rooms to sit in their ordinary clothing with the windows wide open on a cold day. In the second place, it must be recognized that persons who have chronic colds those who are carrying a host of germs just ready to break through their resist- ance and put them to bed are already sick. It must also be recognized that what is safe for a well person or for one accustomed to it, may be neither safe nor wise for a sick person or for one not accustomed to it. When cold air strikes a person who is in a half-sick condition, the vessels in the skin close more than they should. The result is that the blood is driven inward, so that in a few minutes the person can feel the mucous membrane in his nose swelling from the great supply of blood in it. This gorging of the membrane of the nose with blood causes a great quantity of lymph to escape among the cells, and it weakens the resistance of the mucous membrane so that the germs on it multiply more rapidly. Cold drafts may thus cause a cold in a person who is in ill health by disturbing the circulation and the dis- tribution of the blood ; or perhaps it is better to say that cold drafts make a chronic cold worse in this way. It ADENOIDS AND COLDS 8 1 is not advisable, therefore, for a person who is weak or half-sick to expose himself suddenly to severe conditions. Training the body to endure ordinary exposure. A person who suffers from chronic colds needs to build up the strength of the body gradually; to accustom the vessels of the skin to cold baths gradually so that they will act properly instead of throwing him into a chill when a blast of cold air is felt ; to clear the nasal passages and trie throat of obstructions ; to stop the poisoning of the body by decaying intestinal wastes ; and, in general, by degrees to bring the body back to where it will be able to stand ordinary exposure without injury and to kill the germs that are causing the cold. Any one who is always having colds ought, therefore, to begin to build up his health, and if he is wise he will get a good physician to guide him in this task. Catarrh and bronchitis. Catarrh is a chronic cold in the head. Bronchitis is a chronic cold in the bron- chial tubes. In both cases the body is kept poisoned by the germs that are growing in it. Recently it has been discovered that in most cases of these diseases, the germs spread from permanent breeding places in the tonsils or the nasal sinuses, 1 and that treatment is use- less until the homes of the germs are broken up. There is often no swelling or pain in the infected parts, and many persons who are greatly in need of medical attention go for years without it. Since infections of these kinds are believed to cause many cases of rheuma- tism, heart and kidney disease, and other serious ail- ments, they should be given prompt medical care. 1 The nasal sinuses are cavities in the bones that open off from the 'chambers of the nose. 82 PRIMER OF PHYSIOLOGY QUESTIONS Describe the nasal passages. What effect has the mucous membrane upon the air that passes over it ? Name three troubles that may occur in the nose, and the remedy for them. Describe the throat. What is the soft palate? What and where are the Eustachian tubes? How many tonsils are there? Where are they? Of what kind of tissue are the tonsils composed? What is the cause of tonsillitis ? What are adenoid growths? Give five symptoms of adenoids that show in the face. Give other symptoms and effects of adenoids. What is the remedy for adenoids and enlarged tonsils ? Mention some bad effects of allowing children to wait to outgrow adenoids. By what are colds caused ? Distinguish between epidemic and chronic colds. Give three ways by which the body resist- ance to the germs of colds may be raised. How does the practice of taking cold baths protect one from colds? Explain how a cold draft may be injurious. What should a person who has chronic colds_do to bring his body back into normal con- dition ? What is catarrh? What is bronchitis? What bad effects have they upon the body ? SUGGESTIONS TO THE TEACHER In every school that is without medical inspection many undis- covered cases of adenoids and enlarged tonsils may be found. It is a simple matter to learn to recognize the symptoms of these troubles, and the teacher can do no greater service than to call the attention of parents to the children who are suffering from them. Among the arguments that may be advanced in asking that the afflicted children be given medical attention are : The wasting of the school opportunities of the child ; the fixing for life of habits of idleness ; the danger of injury to the hearing ; the permanent catarrhal effects ; and the marring of the regularity of the teeth and the beauty and symmetry of the face. CHAPTER NINE CLOTHING AND THE BODY HEAT FIGS. 74 and 75. The object of clothing is to keep up the body heat. A MAN in the cold arctics loses much more heat than does a man in the warm tropics. Yet the temperature of the human body all over the world is the same. A man who is exercising violently produces five or six times as much heat as a resting man produces. Yet the temperature of the human body during exercise and rest is practically the same. Cold-blooded animals become warm or cold according to the temperature of their surroundings, but the warm-blooded animals, including man, keep their heat near a certain point whether the weather is hot or cold. In health the temperature of the human body varies from 98.8 degrees to about one and one half degrees below this point. The object of clothing. We take our clothing so much as a matter of course, that we often forget that the one great purpose in wearing it is to protect us from cold. It is true that it protects the body from wounds also, and we pay great attention to it because of its effect on our appearance ; but yet the fact that the inhabitants of the 8 4 PRIMER OF PHYSIOLOGY hair epidermis touch corpuscle frigid regions are clad from head to foot in furs, while those who live in the tropics are often very scantily clad, shows that man put on clothing, just as he built houses, to protect himself from the weather. We ought not, therefore, to become so interested in the colors and the appearance of our clothing that we forget the real reason why it is worn. The necessity for a regulator of the body heat. To a certain extent we can regulate the heat of the body by wearing heavy clothes in winter and lighter clothing when the weather is hot. Yet we cannot regulate the loss of heat from the body by clothing alone ; for the temperature of the body must be kept constantly at one point, while the thermometer often runs up and down 20 or 30 degrees in a single day. There must, therefore, be some deli- cate regulator that will govern the loss of heat from the body according to the changes in the temperature of the air. This work is done by the skin. The skin is composed of a dermis sweat fat ne gland A section of the skin. FIG. 76. The structure of the Skin, tough outer layer called the epidermis, and of a deeper layer of connective tissue called the dermis. The outer CLOTHING AND THE BODY HEAT 85 cells of the epidermis are dead and are continually scaling off, but the cells in the lower part multiply and grow to take the places of those that are lost. The dermis contains the nerves of touch and great numbers of small blood vessels. Below the dermis is a layer of loose connective tissue in which a considerable quantity of fat is stored. This layer of fat helps to retain the body heat. Hair follicles and sweat glands. At certain points the epidermis is folded down into deep pockets called hair follicles, from the bottom of which the hairs grow. At other points sweat glands run down from the outer sur- face of the epidermis and lie coiled in the dermis. The sweat glands are hollow tubes, the lower ends of which are surrounded by lymph. Water from the lymph soaks through the walls into the tubes and flows out of the mouths of the glands as sweat. The body heat regulated by the sweat glands and vessels of the skin. The temperature of the body is regulated by the sweat glands and the small arteries of the skin. During hot weather and when we do hard work, the sweat glands assist in cooling the body by pouring out sweat on the surface of the skin. The evaporation of the sweat cools the skin, just as alcohol cools it when allowed to evaporate from it. The ar- teries do their part of this work by controlling the amount of blood that comes into the skin. When the body is exposed to cold, these small arteries contract and keep the blood in the warm inner or- gans. When the body is heated, they relax and allow the blood to come to the surface, where it will be cooled. 86 PRIMER OF PHYSIOLOGY The danger of chilling the body. Chilling the body disturbs the circulation by driving the blood from the skin and congesting the inner parts of the body. This makes us especially liable to be attacked by the germs of pneumonia, influenza, and colds, all of them germs that are often in the air passages waiting for a favorable op- portunity to set up their growth. Wet footwear takes the heat out of the feet, thus causing the mucous membrane of the air passages .and lungs to be gorged with the blood that ought to be in the lower limbs, and interfering with the germ-killing function of the white corpuscles. The wearing of rubbers when they are needed to keep the feet dry is a most important precau- tion in guarding against colds. Danger of overheating the body. Working in a hot, moist atmosphere is very exhausting, and it is almost impossible to keep up the health during the summer months unless we can have air currents to blow away the hot air from about the body. Often these can be secured by sleeping and working outdoors, by opening windows, and by the use of ventilators and electric fans. Some persons do not yet realize that from the standpoint of health it is as important to keep cool in summer as to keep warm in winter. Accordingly, they are willing to pay large sums to heat the rooms in which they live and work in winter, but are not willing to spend a small sum for ventilators and electric fans to be used during the heat of the summer. Just as being chilled in winter makes us liable to attacks of influenza and pneumonia, so overheating in summer lowers our resistance to germs and makes us liable to attacks of diarrhea, dysentery, and other summer diseases. CLOTHING AND THE BODY HEAT Suiting the clothing to the weather. Men who are brought into hospitals suffering with sunstroke are often found to be wearing heavy coats and undershirts, and thick woolen trousers. Little babies in hot summer weather are often covered with "nettle rash" and " heat rash," be- cause they are dressed in such heavy clothing that the skin is kept in an overheated condi- tion. On the other hand, we often see people going without wraps and overcoats when the weather is so cold that the body heat can scarcely be kept up with the heaviest clothing. What we need to remember is that the object of dress is to keep the proper amount of heat in the body. In the spring and fall, especially when the weather is changeable, it is important that the weight of the clothing correspond to the needs of the body. Bathing. One object of bathing is to cleanse the body. This we need not discuss. Bathing as it relates to health is mainly a question of the temperature of the water. Cold baths educate the vessels of the skin so that they learn to open and close quickly and thus regu- late the body heat properly. The importance of having the blood vessels trained to do this is better appreciated when we remember that animals in the FIG. 77. A Filipina wearing a costume that is attractive and well suited to a warm climate. The material of which the clothing is made is thin, and the large sleeves and open neck allow the heated air to escape from around the body. 88 PRIMER OF PHYSIOLOGY natural state must adapt themselves only to changes in the weather, while man often passes in a few seconds from an artificially heated building into an outdoor at- mosphere that is 30 or 40 degrees colder. When these quick changes from warm to cold air are made, the ves- sels ought to contract promptly and shut the blood off from the skin before too much heat is lost from the body. The training of the blood vessels through cold baths is of course mainly a work of training the nervous sys- tem which controls the vessels, and if a person is weak and out of condition, a cold bath may have about the same effect on his nervous system that a long race would have on the muscles of a person not accustomed to taking exercise. In beginning to take cold baths, therefore, we must use care. They ought to be begun with water that is only cool, the bath should be short, and after the bath the skin should be rubbed briskly with a rough towel. Colder water may be used as the skin becomes accustomed to it, but in no case should the water be so cold or the bath so prolonged that the reaction fails to come promptly; for when this is the case, the blood congests the inner organs and a head- ache is the usual result. It is the opinion of some physicians that certain delicate persons are never able to take cold baths without injury ; that baths of this kind are injurious to any one who is in poor health or in a nervous con- dition, and that only those who are strong and in robust health can bear the shock of such a bath with- out injury. Others think that any one can train him- self to take them with safety. This question we must leave to the physicians to decide. CLOTHING AND THE BODY HEAT 8 9 Alcohol and the body heat. In cold weather, taking alcohol causes a feeling of warmth, and men often take a drink to enable them better to endure cold. The feeling of warmth that is given by alcohol is deceptive. We feel cold when the blood has been shut off from the skin and warm when the hot blood from the inner parts FIG. 78. Captain Roald Amundsen, who discovered the South Pole. Because alcohol lessens both the endurance of the muscles and the power of the body to resist cold, none of it was used on the Amundsen expedition. of the body is flowing through the skin. Alcohol temporarily paralyzes the arteries of the skin and leaves them expanded. This allows the skin to become flushed with blood, and causes a sensation of warmth, but at the same time it allows the blood to be cooled and the body heat to be lost. When we are exposed to cold, the vessels ought to be contracted and we ought to feel cold. Hence to bring the blood into the skin so that the body heat will be lost is an unnatural and unsafe thing to do. Persons who use alcohol cannot endure cold so well as persons who do not use it, as the ex- perience of polar explorers proves. 90 PRIMER OF PHYSIOLOGY QUESTIONS What is the temperature of the body? What is the purpose of clothing? Why must the body have some means of regu- lating its heat? Name the two layers of the skin. Describe each. Describe a hair follicle. Describe a sweat gland. What is the source of the sweat ? Explain how the heat of the body is regulated. In what two ways does chilling the body injure it? How may wet feet injure the health? What is the effect upon the health of overheating the body ? Why are air currents especially important in summer? How may they be secured? Discuss the subject of suiting the clothing to the weather. At what seasons of the year should we be especially careful to change clothing according to the weather ? What do cold baths do for the vessels of the skin ? How should one unaccustomed to cold baths begin to take them ? Why does taking alcohol give a sensation, of warmth? What has. been the experience of polar explorers in regard to the power of drinkers and of abstainers to withstand cold ? SUGGESTIONS TO THE TEACHER Have the pupils explain why an athlete throws a sweater over his shoulders when the game stops for a few minutes. Insist that cloth- ing should be adapted to the weather and not to the season. Bring out the difference between cold-blooded and warm-blooded animals and point out that practically all warm-blooded animals are protected by feathers or by hair. CHAPTER TEN THE NERVOUS SYSTEM THE work of the nervous system has always been a mystery to mankind. The ancient Greeks thought that the brain distilled some kind of vital spirit, or essence, which flowed out through the body in the form of a gas. If the brain were in- jured so that the supply of this spirit was cut off, or if the body were deeply wounded so that the vital spirit escaped, life came to an end. Today we know a great deal more than the Greeks knew about the nervous system, but our knowledge of it is yet far from complete. We know enough, however, to help us greatly in the care Of the body, and in FlG ' 79 ' The nervous system. this chapter we shall take up some of the facts concern- ing the nervous system that it is most important for us to understand. 91 92 PRIMER OF PHYSIOLOGY The parts of the nervous system. "The nervous sys- tem is composed mainly of the brain, the spinal cord, and forty-three pairs of nerves that run out from the brain and the spinal cord to all parts of the body. It includes also many little masses of gray tissue, called ganglia (singular, ganglion), that are found among the inner organs of the body, and a great network of nerve fibers that run among these organs. The function of the nervous system. The first func- tion of the nervous system is to control all the organs and parts of the body. If the heart should beat fast when we lie down to rest and slow when we run ; if the sweat glands should pour out water on the skin when we are already freezing and stop work on the hot days of sum- mer; if the muscles moved how and when they pleased, so that they jerked the body aimlessly about; if all the organs worked without system or plan, so that each part of the body carried on its activities without regard to the rest of the body, we should not have a working machine at all, but only a collection of organs and parts. A ruler must, therefore, be set over the whole body to keep all the parts working together properly. This ruler is the nervous system. The second function of the nervous system is to act as the organ of the mind. This function we shall discuss when we take up the study of the brain. The nervous system composed of cells and fibers. The nervous system is made up of nerve cells and of nerve fibers. The nerve cells are larger than most of the body cells, and have a gray color. Most of the nerve cells are found in the brain and spinal cord, but a few of them are found in the ganglia, which are little balls of nerve cells. THE NERVOUS SYSTEM 93 The nerve fibers connect the nerve cells with the other parts of the body. They have a glistening white color, but each fiber has a gray central part which carries messages to and from the spinal cord and brain. This gray core of the fiber is a branch of a nerve cell, and we may think of the nerve fibers as long branches of the cells which run out to all parts of the body. The white nerves that we see in the body of an animal are bundles of nerve fibers. The finest nerves contain but a few fibers, and can be seen only with a microscope. The sciatic nerve, which runs to the leg, is the largest nerve in the human body. This is a flattened cord three fourths of an inch across. Motor and sensory nerve fibers. Some of the nerve fibers carry mes- sages from the brain and spinal cord that cause our muscles to move. These FlG - 8o - A nerve ceil ,, , ~, s-\ i fi and nerve fiber. At the are called motor fibers. Other fibers lower end the attach . carry messages from the skin, the eye, ment of the fibe r *> the . , j , i r , , , i muscle cells is shown. the ear, and other parts of the body to the brain. These messages cause us to feel, to see, to hear, and to understand the condition of all the parts of the body. They cause sensations in the brain, and the fibers over which they pass to reach the brain are called sensory fibers. The brain. The brain is a mass of very soft tissue weighing about fifty ounces and filling the cavity of the cranium (Fig. 21). It has three principal divisions, the 94 PRIMER OF PHYSIOLOGY cerebrum, the cerebellum, and the medulla oblongata. A general idea of the appearance of the different parts of the brain may be gained from Figure 81. conwlutions medulla oblongata ^IP' cerebellum FlG. 81. The brain seen from the side, showing the three principal divisions. The cerebrum. The cerebrum makes up more than three fourths of the entire brain. It is divided by a deep groove into right and left hemispheres. The outside layer of the cerebrum is composed of nerve cells, and therefore has a gray color. To make more room for these cells the whole surface of the cerebrum is thrown into folds, or wrinkles, that are called convolutions. From the cells of the cerebrum a great network of fibers runs in all directions through the brain, and connects all its different parts with each other. Other fibers run down through the medulla into the spinal cord and connect the cerebrum with all parts of the body. Most of the motor fibers from the cerebrum are crossed in the medulla, so that the right side of the cerebrum is connected with the muscles of the left side of the body, and the left side of the cerebrum is con- nected with the muscles of the right side of the body. The function of the cerebrum. The gray outer layer of the cerebrum is the seat of all intelligence. Without THE NERVOUS SYSTEM 95 it all sensations of light, sound, taste, smell, touch, heat, and hunger are lost. When it is removed, all power of moving the voluntary muscles is gone. The cerebrum, therefore, is the part of the brain that thinks and feels. It is the part that causes us to remember and to know, to love and to hate, to be glad and to be sad. The cere- brum decides what we shall do ; it sends out the mes- sages to the muscles when we wish to move; and it governs the whole body. With- out its cerebrum an animal can live, but all its intelligence is gone. It still breathes and its heart continues to beat, but it is only a machine, knowing nothing of its own needs and of the world about it. The cerebellum. The cerebel- lum lies under the back lobes of the cerebrum. Its function is to FlG 82 Cause all the muscles to keep the from above, showing the hemi- proper tension, and to assist in governing the muscles of locomotion. In walking, more than two hundred muscles are used in holding the body upright and in moving the different parts that are brought into action. Each of these muscles must contract with exactly the right force and at exactly the right time, or they will work against each other and the right movements will not be made. When the cerebellum is injured, all the muscles are weakened and relaxed, and the person loses control of the muscles that support the body and move the legs. This causes him to stagger and reel like a drunken man. cerebrum seen 96 PRIMER OF PHYSIOLOGY The medulla and the spinal cord. The spinal cord is about half an inch in diameter and eighteen inches long. Without the roots of the nerves that rise from it, it weighs about an ounce. It lies in the canal in the center of the spinal column and is securely protected by the bones about it. The enlarged upper end of the cord is the medulla. Both the spinal cord and the medulla are composed in large part of fibers that connect the brain with the different body parts. Some of these are sensory fibers, through which messages from the body are passed up to the brain. Others are motor fibers, over which commands from the brain pass down on their way to the different parts of the body. In addition, the medulla contains the centers which govern the heart and lungs. When the cerebrum of an animal is removed, the intel- ligence is lost; when the cerebellum is injured, control of the muscles is lost; but when the medulla is injured, life at once ceases, because the beating of the heart and the breathing stop. Reflex action. Much of the governing of the body by the nervous system is done without thought. The messages, or nerve impulses, pass through the sensory nerve fibers into the nerve cells, pass on through the branches of these cells into other cells that are touching them, and come out again by way of a motor nerve. An action that is caused in this way is called a reflex action, and it can best be explained by an example. Cross your legs, and strike yourself just below the kneecap with the edge of your hand. If you strike the right place, you will start messages to the spinal cord. These, without any thought whatsoever on your part, will THE NERVOUS SYSTEM 97 pass into the motor nerves and down into the muscles of the leg. The muscles of the leg will then contract and cause the foot to jerk. A reflex action is an involuntary action caused by an impulse that starts in a sensory nerve. It is very different from the voluntary actions that are caused by im- pulses which start in the cere- brum and pass out to the muscles when we wish to move some part of the body. Practically all the governing of the internal organs of the body is carried on by re- flexes. Reflexes acquired through practice. The reflexes that we have been discussing are natural a i i .. i reflexes ; we are born with them. There is another Set of reflexes that comes to us through prac- tice. The Skilled Swimmer does not think how he shall move his arms and legs ; in boxing, the hands move without thought and almost faster than the eye can follow; the telegrapher does not think about the combination of dots and dashes that spell out a word, but reads the message he is sending, and his hand does the rest. In the same way, all of us every day do a great part of our work without thought. We walk without giving attention to the muscles and parts which we must move ; we open our mouths to take in food without thinking ; we chew our food without noticing that we FlG< 83> The ball starts from the hand and comes back to it again. The impulse that causes a s reflex action p starts from the outer end of a sensory nerve action. // does not start from the brain ' 98 PRIMER OF PHYSIOLOGY are chewing ; we write without conscious thought as to the shape of the letters. All these things we have repeated so often that we have learned to do them without thought. Acquired reflexes and education. A very important part of education consists in establishing the right re- flexes, so that without thought we shall do the more common things of life properly. A young person who is learning to write ought to learn to hold his pen in the right way and to shape the letters correctly, so that the right reflexes will be formed and the writing question settled for life. He ought to learn to group his words properly and to give the right inflection in reading, so that these matters will attend to themselves thereafter. He ought to take great care to say " please " and " thank you " ; to modulate his voice so that it will not become loud and strident when he is talking eagerly ; to take off his hat and to rise to his feet when he should do so; 'and to do all the other things that go to make up pleasant manners; for no one will ever have good manners who has not established reflexes that will make him able to do what he ought to do naturally and with- out thought of his actions. When you are learning to do anything, the great thing is to do it right, so that you will form a reflex action of the right kind. Then as long as you live the part of your conduct and work that depends on this reflex will take care of itself and you will be free to expend your energy on the new problems that arise day by day. The object of the training that you are receiving at home and in school is to make for you a set of tools with which to carry on the work THE NERVOUS SYSTEM 99 of your life. If you wish to be a good workman, you must, first of all, manufacture for yourself a good set of tools. Habits. Habits are really reflexes that we form by repeating acts, and just as physical habits can be formed, so can moral habits, and habits of the mind, be formed. All kinds of habits are formed most readily in youth, and it is seldom that long-established habits are broken after the age of twenty-five or thirty. Indeed, it is dif- ficult at any time of life to break a habit that has once been thoroughly established. It is because this is true that young people are so constantly urged to form habits of honesty, neatness, accuracy, and cleanliness. An investigation at Harvard University has shown that the students who do high-grade work in the schools of law, medicine, and engineering are students who did their work well before entering these schools ; that it makes little difference what subjects they have studied previ- ously, but that it makes a great deal of difference whether they have formed the habit of learning their lessons regularly and thoroughly, or of going through them in a lazy and careless way. The trifler in the lower grades of school is usually a trifler still in the high school, and very few high-school drones ever become capable and industrious college students. Just what it is that makes the nervous system want to keep on doing things in the same way, we shall not attempt to explain, but it is a well-known fact that what a man does in youth determines very largely what kind of person he will be in later life. If in youth he forms habits of dishonesty and laziness, he is almost certain to develop into an unreliable and unsuccessful man. 100 PRIMER OF PHYSIOLOGY If in youth he forms habits of honesty, industry, and promptness, he will probably become a trusted and a successful man. Rip Van Winkle was always intending to stop drinking, but when a glass was offered him, he would say : " We won't count this time " ; so the time to begin his new life never came. There are many persons who have good intentions and are meaning to get down to work in the future, but their habits keep them loiter- ing on in the same old ways. The importance, therefore, of forming correct habits in youth can hardly be over- estimated. QUESTIONS Name the principal parts of the nervous system. Give two functions of the nervous system. Of what is the nervous system ' composed? Describe a nerve fiber. What are ganglia? What are motor nerve fibers ? sensory nerve fibers ? Describe the brain. Describe the cerebrum. How is the cerebrum connected with the other parts of the brain? with all the parts of the body? What is the function of the cerebrum? What part of the cerebrum is the seat of intelligence? Can an animal live if its cerebrum is removed? Where is the cerebellum? What is its function? What effect upon a person has an injury to the cerebellum? Describe the spinal cord and the medulla. Why does injury to the medulla cause death? What is a reflex action? Give an example. Describe the course of the impulse in a reflex action. Describe the course of the impulse in a voluntary action. What is an acquired re- flex? How may right reflexes be established? Why is it im- portant to establish this kind of reflexes ? What is a habit? Why is it so important to establish, right habits in youth? What did the investigation at Harvard University show in regard to the foundation of good scholarship ? THE NERVOUS SYSTEAf >'. \ IOI SUGGESTIONS TO THE TEACHER Secure if possible prepared microscopic mounts that will show nerve cells, nerve fibers, and the cross-section of a nerve, and have the pupils examine them. For demonstrating the gross structure of the brain, the brain of a sheep is very commonly used. If a sheep's head is not easily available, the head of a cat, rabbit, or fowl may be used. A pair of bone forceps will be needed for breaking away the skull, and after removal the brain should be hardened in alcohol or five per cent solution of formalin. Make clear that a reflex action is always involuntary^ but may or may not be unconscious. A good example of an unconscious reflex is the expansion and contraction of the pupil that follows shading the eye and then exposing it to the light. With the aid of a mirror the pupil can observe this in his own eye by facing the light, cover- ing his eye with his hand, and then removing the hand. If no mirror is at hand, the experiment may easily be performed on an- other person. To a great extent the internal organs are governed by reflexes of this class. The winking or dodging reflex may be used to illustrate conscious reflexes. Emphasize the physical aspects of habit. Bring out the fact that in the doing of our daily work and the living of our daily lives it is inevitable that we shall form either correct habits or wrong habits. The late Professor James' discussion of habit, which may be found in either his 7^alks to Teachers or his Textbook of Psychology (pub- lished by Henry Holt and Co., New York), is a masterly and inspir- ing piece of writing. Every teacher may with profit read it himself, and selections from it may be read to the class. In teaching this and the following chapter, the teacher should bear in mind the importance of fixing quiet, orderly habits of mental work in order that there may be no waste of nervous energy through excitement and overeagerness. Some teachers who are very successful in imparting information fatigue their pupils unduly through the tense, nervous atmosphere of the school. This is com- ing to be recognized as an important point in school hygiene. CHAPTER ELEVEN THE CARE OF THE NERVOUS SYSTEM FlG. 84. There is no truth in the idea that a person can have too much natural sleep. SUPPOSE that you decide to raise your hand. The hand comes up. Can you explain exactly what made it rise ? It is in reality a very complicated action, and to make sure that you understand it we will go through the different steps in it with you. First of all, you decided to raise your hand. This was an act of the mind. Then nerve impulses, whatever they may be, were started out from the brain. These impulses traveled down through the medulla and spinal cord, passed out into the nerves of the arm, and finally entered the muscle cells. This caused the muscle cells to contract and lift the arm. The muscle did the work, but the nervous system decided what was to be done and caused the muscle to do it. In all our other activities we find that the nervous system plays a guiding and controlling part. The regu- lation of the body heat ; the secretion of the digestive 102 THE CARE OF THE NERVOUS 3 SYSTEM 103 juices ; the excretion of the wastes ; all these processes, as well as every movement that we make, are under the control of the nervous system. We must, therefore, keep the nervous system in health ; for when it goes wrong in its work, the whole body suffers. Fortunately for us, our nervous systems are splendidly built, and on the whole they do their work faithfully and well. There are, however, certain points in the care of them in which many persons fail, and we ought to have an understand- ing of these points. Sleep necessary for the nervous system. The cells of the nervous system must have sleep to build themselves up for further work, and so far as we know they are the only part of the body that needs sleep. The amount of sleep needed varies greatly in different persons and in persons of different ages. A little baby may sleep as much as twenty-two out of the twenty-four hours. At six months of age he sleeps about sixteen hours. At seven years of age a child should sleep eleven or twelve hours ; at ten or twelve years of age, at least ten hours. Older persons should take the amount of sleep that they find best for them. Occasionally a per- son is found who keeps in good health on four, five> or six hours of sleep. Other persons must have eleven or twelve hours. Each one should go to bed early enough not to feel sleepy when getting-up time comes ; for there is no truth in the idea that one can have too much healthy sleep. 1 Are you still tired and sleepy when you waken in 1 Illness and poisons absorbed from the intestines cause drowsiness. When a person is sleepy from one of these causes, the condition is, of course, an unnatural one. 104 OF PHYSIOLOGY the morning ? Are you pale and languid and do you drag yourself through your work ? If you are, it may be because you are cutting your sleep short ; for there are thousands of people who are starving for sleep as truly as other people are starving for food and fresh air. If you have fallen into a habit of staying up late in the FIGS. 85 and 86. A change for a time to a different kind of occupation is rest- ful to the nervous system. evenings, break this habit and go to bed early. A runner or a baseball team that has been losing sleep has not. the slightest chance of winning from others of equal ability who have had a sufficient amount of it. This is because the nervous system, when it lacks sleep, is out of condition and cannot control the muscles as it should. Rest necessary to the health of the nervous system. A great amount of nervous energy is required to drive the more than five hundred muscles of the body, and when we study or do other brain work, it is the nervous system that is called into action. In either physical or THE CARE OF THE NERVOUS SYSTEM 105 mental work, therefore, we tire the nervous system, and we ought not to continue either until our cells are poi- soned with the "fatigue toxins " that appear in the body in cases of exhaustion. Factory workers who are forced to speed themselves up to machines, and little children in schools where the recitation periods and the school days are too long, suffer from fatigue and cannot do their best work. Many earnest, ambitious individuals who are trying to do the very best work of which they are capable, injure themselves and lower their working power by keeping their nervous systems exhausted. 1 In general, it has been found best to work hard during regular working hours, and then to have rest periods when something entirely different is done. In schools there should, therefore, be rest and play periods for young children, and older persons ought to work certain hours every day and then for a time have a different kind of occupation. Fresh air helpful in resting the nervous system. A nerve fiber from a frog will carry impulses all day without fatigue if it is exposed to the air so that it can take in the oxygen that it needs. If the supply of oxygen be cut off from it, however, it soon becomes ex- hausted. Undoubtedly children in open-air schools can do more work without becoming tired than can children in indoor schools, and it is the belief of those who sleep 1 In some factories it has been found that the workmen can accomplish more when they work eight hours than when they work ten hours, be- cause when they work the longer hours they are always tired and never in good condition. The number of hours that is best for a working day must, of course, vary with the kind of work and with the kind of people who are doing the work. io6 PRIMER OF PHYSIOLOGY in the open air that they need about an hour's less sleep than they require if they sleep indoors. These facts in- dicate that fresh air is an aid in preventing exhaustion, and that tired nerve cells are more quickly rested and built up when the body is given plenty of outdoor air. A peaceful mind necessary for health. In our study of the nervous system we must always keep in mind FIG. 87. Both the child's pleasure at seeing the toy and the man's pleasure at seeing the child's happiness affect the mind, and through the mind affect the body. that it has the double function of governing the body and of acting as the organ of the mind. It is perhaps economical to have these two different kinds of work done by the same system, but this plan has its drawbacks as well as its advantages; for the condition of the mind greatly affects and sometimes interferes with the proper regulation of the body. Good news or bad news may greatly change the beat- ing of the heart. A toy that pleases a child will cause his whole body to tingle with pleasure, and will cause impulses to pass out to his muscles that will make him THE CARE OF THE NERVOUS SYSTEM 107 laugh and clap his hands. Food that is pleasing to the taste, or even the sight or smell of food, will cause the " -mouth to water," which is another way of saying that it causes the digestive juice to flow from the salivary glands. Experiments on a dog have shown that the sight and smell of food, even though the food does not reach the stomach at all, causes an abundant flow of the digestive juices in the stomach; while in a dog that was made angry by having a cat placed near it when it was eating, the flow of the juice in the stomach was inter- fered with for two whole days. All these facts show that anger, sorrow, and worry interfere with the proper action of the body; that the mind greatly affects the body; and that a cheerful, quiet, hopeful mind is neces- sary for health. At the same time, we must realize that sickness is a real thing, and that when it comes upon us we cannot depend upon the mind alone to restore us to health. When a child has diphtheria, only antitoxin will save its heart from being poisoned, and when tuberculosis attacks the lungs, good food, fresh air, ancl rest, as well as cheerfulness and hope, are needed if the body is to make a winning fight against the germs. When the kidneys have been poisoned by scarlet fever or by the use of alcoholic drinks, nothing that we can think about them will make them able to throw the wastes out of the body as a pair of sound kidneys are able to do. The mind cannot take poisons out of the body ; it can- not kill germs that get into the body. These things the body must do for itself, and all that the mind and the nervous system can do is to help to keep each or- gan of the body at work at its particular task. IO8 PRIMER OF PHYSIOLOGY Nevertheless, it is true that the nervous system rules the whole body; that when the nervous system goes wrong, the whole body goes wrong; and that just as food, fresh air, exercise, and rest are necessary to the health of the body, so a peaceful, hopeful mind is necessary in order that the nervous system may remain in health and regulate all the body parts properly. QUESTIONS What part of the body needs sleep? How much sleep should a baby have ? a child seven years old ? a child twelve years old ? an adult ? Why is rest necessary for the nervous system ? Under what conditions of work and rest can a person do the best and most work? Give three facts indicating that open-air life pre- vents exhaustion of the nerve cells. What is the effect of joy, hope, and other pleasant emotions on the nervous system? What is the effect of anger, sorrow, or worry ? What mental state is necessary to the health of the body? Mention some experiments with animals that prove this. Can the mind take poison out of the body ? Can it kill germs? How can the mind help the body to do these things? SUGGESTIONS TO THE TEACHER Emphasize the fact that nerve cells have the same needs as the other cells and that any trouble in other parts of the body is bound to damage the nervous system. Dr. Thomas D. Wood of Columbia University estimates that " 15,000,000 out of the 20,000,000 children in the schools of the United States need attention for physical de- fects which are partially or completely remediable." Insist on the evil effects of pain and ill-health on the nervous system, and use this as an argument for avoiding infections and for giving attention to adenoids, decayed teeth, painful feet, defective eyes, and other physical defects. CHAPTER TWELVE THE EYE MANY of the messages which travel up the nerves to the brain are started within the body itself, and cause sensations that tell us about the condition of the body. Examples of sensations of this kind are sleepiness, fatigue, weakness, faintness, hunger, thirst, and nausea. Others of the messages that come to the brain are started in the nerves by things that are outside the body, and these messages bring us information about the out- side world. The nerves that carry these messages are the nerves of sight, hearing, touch, taste, and smell. Seeing, hearing, touching, tasting, and smelling are the five special senses, and the eye, the ear, the nose, the mucous membrane of the mouth, and the skin are the special sense organs. The brain dependent on the sense organs for informa- tion. Through the special sense organs we learn all that we know of the world about us, and when anything in- terferes with the proper working of these organs, much information that ought to come to the brain fails to reach it. Many children who are thought to be stupid 'are dull, not because they have slow brains, but because their eyes and their ears are not quick in gathering the information that is necessary to make them intelligent. We must learn to care for our sense organs, especially for our eyes and ears, for without them the brain sits in idleness, and is no more certain of what is the right thing to be done than is the commander of an army whose scouts bring him no news of the enemy's movements. The nerves in the eye stimulated by light. Light is waves in the ether which fills all space, and the eye 109 1 10 PRIMER OF PHYSIOLOGY is an instrument so constructed that when light enters it the nerves of sight are stimulated and messages are started to the brain. These messages give us a series of pictures of the world about us, from which we learn about the color and the form of ob- gland jects, about their movements nasal cavity and their nearness to us. From these pictures much of our FIG. 88. The tear gland and the knowledge comes. Much of duct that carries the tears to the the pleasure also that we have nose. .. in the world comes from them ; for just as music starts messages from the ear that give pleasure to the mind, so beautiful objects start messages from the eye that are pleasing to us. Years ago, a great man of science suggested that we should have concerts of beautiful colors for the eyes as well as concerts of music for the ears. Such concerts have already been attempted. The protection of the eyes. The eyes are protected from blows by the deep sockets in which they lie, and by cushions of fat on which they rest and turn. They are protected from dust and sweat, and screened from light, by the eyelids, the eyelashes, and the eyebrows. In the outer corner of each of the upper eyelids is a small, gland which secretes the tears. These flow across the eyes to the inner corners, and run down a little duct into the nose. In their passage across the eye, the tears wash away dust and germs. In the eyelids are glands, very similar to the glands that oil the hair, which pour out oil along the edges of the eyelids. Sometimes these glands become diseased, and the secretion from them THE EYE III dries and forms scales around the roots of the eyelashes. The trouble in cases of this kind is that germs are grow- ing in the gland. Dropping a solution of boracic acid (as much as will dissolve in water) into the eyes will help to kill the germs. The muscles of the eye. The eye is moved about by six muscles. The back ends of these muscles are at- tached to the eye sockets. The front ends are at- tached to the ball of the eye. These muscles can turn the eye in, out, up, or down. It is not nec- essary always to turn the optic nerve head toward an object FlG - 8 9- The muscles that move the eye. which we wish to see ; for the eye muscles can turn the eye toward it while the head is at rest. In some persons from birth the sight of one eye is better than that of the other eye. Such a person may fall into the habit of using only his good eye, and the muscles of the weak eye will not turn it toward the objects he looks at. A person whose eyes behave in this way is said to squint, or to be cross-eyed. Usually the trouble can be remedied if it is taken in time, but if it is not attended to in very early life the sight of the defec- tive eye will be lost. A little child with this trouble should, therefore, have proper treatment at the earliest possible date. The structure of the eye. The eye has a tough, white outer coat called the sclerotic coat ; a dark middle coat called the choroid coat ; and lining the back two thirds of the eye, a delicate inner coat called the retina. The 112 PRIMER OF PHYSIOLOGY front part of the sclerotic coat, which is called the cornea, is transparent like glass, and we look out, or rather the light comes in, through a little window that is like a small round watch crystal on the front of the eye. sclerotic coat ins muscles FIG. 90. A diagram showing the structure of thfe eye. Inside the eye is found a circular, clear structure called the lens, which is fastened by ligaments to the choroid coat. The lens and the ligaments that sup- port it divide the eye into a small front chamber and a large back chamber. The front chamber is filled with a watery liquid, called the aqueous humor. The back chamber contains a clear jelly-like substance called the vitreous humor. The nerves of sight enter at the back of the eye and spread out in the retina. The light reaches these nerves and starts messages in them by passing in through the cornea, the aqueous humor, the THE EYE 113 lens, and the vitreous humor, and striking against the retina. The iris and the pupil. The front part of the choroid coat is called the iris. This shows through the clear cornea, and the person is black-eyed, brown-eyed, or blue-eyed according to the color of his iris. In the center of the iris is a circular opening called the pupil. Through this the light passes into the eye. Muscles in the iris regulate the size of the pupil ac- cording to the brightness of the light, Examine your own eyes after being in a bright light and again after being in a weak light, and you will have no trouble in seeing the differ- ence in the size of the pupils. The image formed by the lens on _ - . ' the retina. If you were to focus a camera on a group of objects, as for example a house with trees surrounding it, and then look at the ground glass in the back of the camera, you would see an image of the scene that lies before the camera. The image would be upside down, and the right and left sides would be reversed, but the house and the trees would be there, each with its own colors, and each in the right position in the group. The lens in the front of the camera forms this image by gathering up all the light that comes into the camera from each of the objects, and bringing the rays together so as to form a picture of all the objects. In the same way, the lens of the eye forms on the FlG - 1. The iris and the pupil. 114 PRIMER OF PHYSIOLOGY retina images of the objects that we see. In the eye, as in the camera, the images are upside down, but they are there in their proper col- ors, and the different objects have the right, sizes and the right positions in regard to each other. This picture of whatever we are looking at starts impulses in the nerves of sight to the brain, and when these messages are re- ceived by the brain, we form judgments about the size, color, and form of the ob- jects, and say that we see the objects. By means of the images in the eyes we can judge also of the dis- tances of objects from us, of their movements, and of their smoothness or roughness. The shape of the lens changed in looking at far and near objects. In looking at FlG. 92. The lens in the camera forms inverted images on the ground glass in the back of the camera. a near object the lens of the eye must be rounded up, and in -looking at a far object it must be flattened. This rounding and flattening of the lens is done by little mus- cles in the eye which loosen and tighten the ligament that supports the lens. If you should fill a small sack with water and then pull on the ends of the sack, you would flatten it; and if you should then stop pulling on the ends of the sack, the sack would of itself round THE EYE 115 up. So in the eye, when the ligament is loosened, the lens becomes rounder. This change in the shape of the lens is called the accommodation of the eye, be- cause by it the eye is accommodated to the nearness or farness of the object. Near-sightedness, far-sightedness, and astigmatism. In a camera, if you move the lens too far forward or back- ward, the image becomes blurred. So in the eye the image will not be clear and the vision will not be dis- tinct, unless the lens is the right distance from the retina. The eyes of some persons are too long from front to back. In such eyes the lens is too far from the retina and the image is indistinct. These persons see near objects better than far objects, and they are therefore said to be near-sighted. Any one who bends over his book in reading, or who holds his book less than twelve inches from his eyes, is near-sighted. The far-sighted eye, on the other hand, is too short from front to back, and the lens is too close to the retina. 1 Persons with eyes of this kind see distant ob- jects best, and they are said, therefore, to be far-sighted. In other eyes, the curvature of the cornea is not the same in all its parts ; that is, some parts of it are flatter than other parts. Rays of light that pass through this uneven cornea cannot all be brought to a focus at one point, and a clear image is impossible in such an eye. This trouble is called astigmatism. It is a very com- mon defect in the eye and may be found alone, or along with either near-sightedness or far-sightedness. Necessity for a clear image in the eye. If a sharp, 1 In some cases of near-sightedness and far-sightedness the trouble may be in the shape or the refracting power of the lens. 116 PRIMER OF PHYSIOLOGY clear image is not formed on the retina of the eye, seri- ous troubles follow. The muscles in the eye keep pull- ing and working to try to change the shape of the lens so that the vision will be clear ; in reading it is a strain on the attention to tell what letters are in the words, and, in general, it makes all work that requires close attention more difficult. This overworks and deranges the nervous system, and soon the health of the whole FIGS. 93 and 94. There are 5,000,000 school children in the United States who need glasses. body is injured. Two of the most common symptoms of eyestrain are headache and trouble with the digestion, often accompanied by dizziness and vomiting. The importance of spectacles. It is often said that the great amount of close work that people now do injures their eyes, and it is insisted that the eyes of school children in particular are damaged by the work that they are required to do. There is doubtless some truth in this statement, but it is also true that many eyes are naturally defective. Examination of the eyes of the Indians who come direct from the plains to Hampton Normal School, in Virginia, shows that 34.6 per cent THE EYE II/ of them are in need of glasses to improve their vision or to relieve eyestrain. It is estimated that there are 5,000,000 school children in the United States who have defective eyes. Nothing can be done for these eyes except to put glasses before CUFF p n T r 3 O U D 3 FlG. 95. You should be able to read the upper line at a distance of 30 feet, and the two lower lines at a distance of 20 feet. them that will cause clear images to fall upon the retinas. We shall not attempt to explain the kinds of glasses that are used to correct the different kinds of eye trouble, but it is an easy matter for a good oculist to select the kind of lens that each eye needs. Test your vision with the letters given on this page, and if you have reason to believe that you need glasses, try to get them ; for if glasses are put on in time, many cases Il8 PRIMER OF PHYSIOLOGY of astigmatism and near-sightedness will be outgrown, while if these troubles are neglected, the shape of the eye may be so spoiled that the person will be compelled to wear glasses all his life. The eyes injured by disease germs. In measles, scarlet fever, and smallpox, the germs grow in the eyes. During the progress of these diseases the eyes should be rested and shielded from a bright light, and when the eyes have been severely attacked, they should not be used until recovery is complete. " Pink eye " is a highly infectious disease that often leaves the eyes red and inflamed for life. It is spread by germs that are passed from one person to another, and a child with "pink eye" ought not to be in school. Trachoma, or "granulated lids," is another germ disease of the eyes that is greatly to be feared. It is infectious, and it is unsafe to be around a person who is suffering from it. Do not wash your eyes in a public wash basin ; do not touch a public towel ; do not touch your eyes with dirty hands ; and do not touch the hands, the pencil, or the books of any one who has sore eyes. Importance of a good light while working. To read or to work by a dim light is very injurious to the eyes. Too bright a light also is injurious, especially if one faces it, and a flickering light of any kind is bad. In writing one ought to sit so that the light comes over the left shoulder ; for then the shadow of the hand will not interfere with the work. Facing a window in the day- time, or a lamp at night, is hard on the eyes. Reading on into the twilight is a great strain on the eyesight, and one ought not to seat himself carelessly too far from the light when doing close work at night. THE EYE 119 One difficulty when the light is too dim is that the work is kept so close to the eyes that there is a great strain on the muscles that turn the eyes inward ; for the closer an object is to the eyes, the more must the eyes be turned inward to focus both of them on it at the same time. Keeping the work close to the eyes is FIG. 96. A good light while reading is important. especially injurious in the case of little children; for their eyes are soft and easily pulled out of shape, and the muscles tugging at the eyes to turn them inward spoil the shape of the globe of the eye and cause astig- matism. To prevent this, school books for young chil- dren ought to be printed in type large enough so that the children will not have to keep the books close to their eyes while studying, and schoolrooms should be well lighted. The rule in erecting modern school build- ings is to allow from one sixth to one fourth as much space for windows as there is floor space in the room. Ribbed glass used in the upper sashes assists very greatly in spreading the light evenly over the room. 120 PRIMER OF PHYSIOLOGY Resting the eyes helpful and overtaxing them injuri- ous. When we have been reading or doing other close work for some time, it benefits the eyes greatly to stop for a few moments and look at a distant object, or to gaze into the distance without looking at anything in particular. Reading on a moving train or a street car quickly tires the eyes, because the distance between the book and the eye is constantly changing, and the muscles in the eye are kept busy changing the shape of the lens. Reading while lying down is also hard on the eyes, because the book or paper is often held in such a position that the eyes must be strained to see it. If you read while traveling or while lying down, rest your eyes occasionally and stop the reading be- fore the eyes have become fatigued. QUESTIONS How are the eyes protected from blows? from light and dirt? Where are the glands which secrete the tears? Of what use are the tears? What is the cause of scales on the edges of the eyelids? Explain how the eye is moved. What causes a person to squint? Name the coats of the eye. De- scribe the cornea ; the lens ; the aqueous humor ; the vitreous humor ; the iris ; the pupil. In what part of the eye are the nerves- of sight? Explain how images are formed in a camera and in the eye. In what do the images in the eye start messages? What judgments does the brain form from these messages ? How is the eye accommodated to near and far objects? What causes near-sightedness? far-sightedness? astigmatism? What is the effect on one's health of a blurred image on the retina? How many school children in the United States need THE EYE 121 glasses? Why is it important, aside from improving the health, that glasses be worn by children who need them ? In what germ diseases are the eyes infected ? How should the eyes be cared for in these diseases? What is " pink-eye " ? " granulated lids " ? Name some things that should be avoided because they may allow germs to enter the eyes. From what direction should the light come when one is working? Why is it harmful to read or work by a dim light? Why is work that is held close to the eyes especially harmful to little children? How much window space should a school- room have ? Why is it harmful to read on a moving train ? while lying down? SUGGESTIONS TO THE TEACHER When medical inspection is lacking, the school should have a vision chart for examining the eyes. This is usually furnished free by city and state superintendents, or a copy may be purchased for ten cents from World Book Company, Yonkers, New York. The following directions will allow a rough test to be made with the let- ters on page 117: Have a good light on the letters that are to be read. Seat the pupil at a distance of 20 feet from them. Test persons wearing glasses with their glasses on. Cover one eye with a card (but do not press on it) while the other is being tested. The upper line should be read at a distance of 30 feet and the lower lines at a distance of 20 feet. In case either eye fails to- meas- ure up to this standard, glasses are needed. Persons who cannot read may be tested by asking them whether the letter E in the chart is open at the right, left, top, or bottom. In case the pupil knows the chart by heart, cut a small opening in a piece of cardboard and expose only one character at a time while the test is being made. Failure to read the letters by children under seven years of age does not necessarily mean that glasses are required. There may be defects of the eye that will not be revealed by this test. When there are symptoms of eyestrain, an oculist should be consulted. CHAPTER THIRTEEN THE EAR FlG. 97. The light waves start impulses in the nerve of sight, and we see the lightning; the sound waves start impulses in the nerve of hearing, and we hear the thunder. DOUBTLESS you have seen a flash of lightning fall from the sky, and! have stood and waited until the roll- ing of the thunder came to your ears. What was it that came to your eyes and caused you to see the lightning? It was waves in the ether. 1 What was it that came to your ears and caused you to hear the thunder ? It was waves in the air. Why can you not see the thunder ? It is because the eye is not af- fected by waves in the air; only ether waves can stimu- late the nerves of sight. Why is it that you do not hear the lightning ? It is because ether waves do not affect the ear ; only air waves stimulate the nerves of hearing. 1 Ether is an invisible, elastic fluid that fills all space. Light, the elec- tric waves that are used in wireless telegraphy, and the X-ray are waves in the ether. They run with almost incredible speed, light traveling at the rate of 186,000 miles a second. Air waves are very much slower than ether waves, sound waves traveling only about 1120 feet a second. 122 THE EAR 123 mastoid cavity inner ear Through the ear the confusion of air waves that comes from the instruments of an orchestra is trans- formed into music ; through it we are able to under- stand the thoughts of a friend when he, by speaking, sends a series of air waves to us across a room. In the whole body chere is nothing more wonderful than this instrument that has been given us to catch the waves in the air and carry their motion to the nerves of hear- ing, which lie deep in the bones of the skull. There are three main divisions of this organ, the outer, the middle, and the inner ear. The outer ear. The outer ear is composed of carti- lage covered with skin. It catches the sound waves and turns them down a winding canal to the middle ear. When a dog, a horse, or a rabbit is listening, it holds up its ears to catch the sound waves, and a man sometimes puts his hand behind his ear to help in catching the sound and turning it into the ear. The middle ear. The middle ear is a little drum- shaped cavity in the bone of the skull. It is filled with air, and is connected with the throat by the Eustachian tube. At the inner end of the canal that leads inward middle ear Eusta- \ chian tube FIG. 98. Diagram of the ear. 124 PRIMER OF PHYSIOLOGY from the outer ear is a little membrane called the tym- panic membrane. This stretches like a thin skin across the bottom of the canal and separates the outer ear from the middle ear. The bone of the skull behind the middle ear is spongy and has a cavity in it which is called the mastoid cavity. This opens out, like a little chamber, from the middle ear, and when germs infect the middle ear they often reach the mastoid cavity also. This trouble is called mastoiditis. In cases of this disease there is always danger that the germs will find their way to the brain and cause meningitis. The bones of the ear. Across the middle ear a chain of three small bones stretches from the tympanic membrane to the inner ear. These bones are called from their shape the malleus (hammer), the incus (anvil), and the stapes (stirrup). The malleus tympanic -HjP i s fastened to the tympanic mem- membrane W brane ; the stapes fits into an opening .., that leads into the inner ear ; and the FlG. 99. The chain of bones of the ear incus is between the malleus and the connecting with the gta ( Fi gg ^ After we tympanic membrane. ,. , , , f , studied the plan of the whole ear, we shall learn how these bones carry the motion of the sound waves from the tympanic membrane to the inner ear. The inner ear. The inner ear lies deep in the bone of the skull. It is exceedingly complicated in structure and we shall not attempt to explain it further than to say that it has three parts, a central part called the vestibule, a coiled part called the cochlea, and three semicircular canals at the back that wind through the THE EAR 125 opening for stapes vestibule cochlea bone of the skull. The entire inner ear is filled with a fluid, and the fibers of the nerve of hearing end in such a way that when waves . . are set up in the fluid, the cular nerve endings are stimulated and messages are started in them to the brain. How a sound wave starts a message to the brain. When a sound wave strikes the outer ear, it is turned down the canal leading to the inner ear; it then strikes against the tympanic mem- FIG. too. The inner ear. The brane and starts it to swing- Iower fi & ure shows the natural size of , . ,. . the inner ear. ing out and in. This puts the malleus, the incus, and the stapes in motion, and the stapes is pushed in against the liquid in the inner ear. This sets up waves in the liquid, and the beat- ing of these waves stimulates the nerves of hearing and starts messages to the brain. When these messages reach the brain, we hear the sound. If the waves in the air are large and strike violently against the tympanic membrane, so that large waves are set up in the fluid in the ear, we say that the sound is loud. If the waves are small, so that the tympanic membrane and the chain of bones swing gently to and fro, the nerves are stimulated only a little, and the sound is soft. Within the inner ear is a wonderful mechanism which is so arranged that a sound having one pitch will start messages in one set of nerves, and a sound having a different pitch will start messages in another set of 126 PRIMER OF PHYSIOLOGY nerves. By this arrangement the brain is able to tell the pitch of the different sounds that come to it. Earache and running ear. Practically all ear troubles are in the middle ear and are caused by germs. These germs work their way from the throat into the ear through the Eustachian tube, and they grow in the lining of the middle ear and about the little bones, much as they grow in the nose when we have catarrh. Frequently, in diseases like colds, grip, scarlet fever, measles, and diphtheria, the ears become infected, and in these cases it is most important that a physician give them early and proper care. Often it is adenoids that start ear trouble, and in chronic cases of earache or running ears, adenoids should be looked for. It is not right to allow children to suffer needless pain from ear troubles, and they ought not to be left to out- grow them ; for a running ear already has a hole through the tympanic membrane, and the hearing is in danger of being lost. Nearly all deafness in older persons is due to the fact that when these persons were children, germs were allowed to grow in the ears until they dam- aged the tympanic membrane or the bones that carry the motion of the sound waves to the inner ear. Some- times the membrane or the chain of bones is broken down, or destroyed. Sometimes the trouble is that the membrane is thickened and stiffened, or the chain of bones is stiffened at the joints until the movement in it is wholly or partly lost. Among grown persons about one third have the hearing affected in one or both ears. This could be prevented by attending to the ears at the proper time. Other points in the care of the ear. Quinine, if taken THE EAR 127 for a considerable time, may cause deafness, and this medicine, like other medicines, should be used only when prescribed by a physician. A blow on the side of the head is dangerous to the hearing ; for it may send so strong an air wave down the canal of the ear that the FlG. 101. Testing the hearing. tympanic membrane may be broken. Live insects in the ear cause great distress by buzzing and moving about. They should be drowned by pouring warm water into the ear. No one but a physician should attempt to remove objects from the ear, because an unskilled person in attempting to do so may injure the lining of the canal, or break the tympanic membrane. In the canal of the ear there is a bitter wax secreted to protect the ear from insects. Children sometimes form a habit of picking at their ears with the head of a pin or other object. This causes the lining to become inflamed and the wax to be secreted too abundantly. One physician has said, "You should never thrust anything smaller than your elbow into your ear," and another has added, " Before you thrust your elbow into your ear you should wrap your coat around it." If wax accumulates until it be- comes troublesome, a physician should be consulted. 128 PRIMER OF PHYSIOLOGY QUESTIONS Describe the outer ear. What is its use? Describe the middle ear. What separates the middle ear from the outer ear? What is the mastoid cavity? What causes mastoiditis? Name and describe the three bones of the middle ear. Where is the inner ear? Name its parts. With what is the inner ear filled? Where do the nerves of hearing end? Explain how a sound wave stimulates the nerves of hearing. What is the difference between a loud sound and a soft sound? Explain how it is possible for the brain to understand the pitch of a sound. How do germs enter the ear? In what parts of the ear do they grow ? What is the most common cause of earache and running ears? What is the cause of nearly all cases of deaf- ness in grown persons? What per cent of adults have im- paired hearing? What bad effects have excessive doses of quinine? Why is a blow on the side of the head dangerous ? What damage may be done when an unskilled person attempts to remove objects from the ear? What is the use of the bitter wax in the ear ? What damage may be done by picking at the wax in the ears? SUGGESTIONS TO THE TEACHER In schools that do not have medical inspection the teacher should test the hearing. This may be done either with a watch (Fig. 101) or by requiring the pupil to repeat words that have been whispered to him. Each ear should be tested separately. It should be im- pressed upon the pupils that deafness is rarely curable and that any ear trouble demands medical attention at once. CHAPTER FOURTEEN THE ORGANS OF TOUCH, TASTE, AND SMELL THE sight and the hearing are especially important because they give us knowledge not only of near ob- jects, but also of objects that are far away. The sense of smell may also give us information of an object when it is at a distance; but in the main this sense, as well as the sense of taste and the sense of touch, is valuable because it enables us to judge of objects that are near at hand. There is not much that we can learn about any of these senses that is important from the stand- point of health. It is in- teresting, however, to know something of the way in which the messages that cause the sensations of touch, taste, and smell are started in the nerves, and to understand something of what we learn through these senses. In this chapter we shall therefore study the organs of touch, taste, and smell. Touch. The sense of touch is the most widely dis- tributed of all the senses, for we can feel through the skin on every part of the body. Through the sense of touch, even better than through the eye, we can learn the form of objects ; through it we can tell whether ob- jects are smooth or rough, whether they are hot or cold. 129 FlG. 102. A blind girl reading by sense of touch. 130 PRIMER OF PHYSIOLOGY Blind persons learn to read by passing the finger tips over raised letters, and persons who are both blind and deaf gain through the touch much of the information that comes to others of us through the eye and ear. The touch, therefore, is a sense that is not only at all times highly useful to us, but one that can be fur- ther educated and in time of need called into use to take the place of other senses. The endings of the nerves of touch in the skin. The dermis, or lower layer of the skin, is thrown up into little peaks called papilla (singular, FIG. zo3. A ne'rve fiber ending P a P illa ~) tha ' Stand P Under around the bases of the cells in the the epidermis. Some papillae epidermis. contain a great network of little blood vessels. Others contain a touch corpuscle, which is a little group of cells with a nerve fiber wind- ing about through it and ending in it (Fig. 76). Other fibers of the nerve of touch divide at the outer end into many little branches which end freely among the lower cells of the epidermis, or spread out into little saucer- like structures around the bases of some- of these cells (Fig. 103). The nerves of touch are especially abundant in the fingers, lips, tongue, and tip of the nose, and in these places the sense of feeling is most acute. You can perform some interesting ex- periments by thrusting two or three pins through a piece of cork or wood FIG. 104. TOUCH, TASTE, AND SMELL 131 (Fig. 104) and trying how far apart you must place them on different parts of the body to enable you to feel the points of the pins separately. Messages started by pressure in the nerves of touch. When we touch anything, the epidermis is pressed down on the ends of the nerves of touch. This starts impulses to the brain, and when these impulses arrive in the brain they cause us to feel. If all the nerve endings that are being stimulated have the same amount of pressure on them, we know that we are feeling a smooth surface. If some of them are being pressed harder than others, we know that the surface is rough. When we are touching an object, we know where the object is, be- cause we know from what part of the body the messages are coming. We know whether the object is large or small by the extent of skin surface that is touching it, and by the distance that we must move our hands to pass them over it. If you lay your hand against the wall, messages come in from the whole front of the hand, and you judge that you are touching one large object. If you feel two objects, like the points of two pencils, you know that there are two of them because the messages come from two places in the skin with a space between them in which the nerves are not being stimulated. Mistaken judgments concerning objects that we touch. The mind can make mistakes in judging of the messages that come in through the nerves of touch as well as in forming judgments from the messages that come in through the eye. Cross your fingers and rub them across the tip of your nose so that the nose is between, the two fingers. Can you explain why you seem to feel two noses ? 132 PRIMER OF PHYSIOLOGY Taste. The nerves of taste are in the mucous mem- brane of the tongue and of the back part of the mouth. Before anything can be tasted, it must first be dissolved. Then it works its way down among the cells and starts impulses in the nerves of taste. When these impulses reach the brain, we learn whether the object has a sweet, sour, bitter, or salt taste. Many of the supposed tastes of foods are in reality odors, and when because of a cold or for other reasons the sense of smell is dull, many foods are practically tasteless. The continual use of tobacco, alcoholic drinks, and strong condiments like pepper and tabasco sauce, permanently diminishes the sense of taste. The sense of smell. The sense of smell is probably the keenest of all our senses. It is likely that it is of use chiefly to judge whether or not our food is in proper condition to be eaten, and to tell whether air is fit to be breathed. Lower animals, like the dog, have this sense so highly developed that they can follow the track of a man or other animal many hours FIG. 105. The nerve of smell end- after the trail has been ing in the mucous membrane of made> Among men individ- the nasal chamber. uals differ greatly in the sharpness of their sense of smell. The nerve of smell stimulated by particles in the air. What we call an odor, or a smell, is in reality little particles of matter floating in the air. These particles come from a rose, from our food, or from anything that we smell, TOUCH, TASTE, AND SMELL 133 and are drawn up into the nasal chambers with the air. In the mucous membrane that lines the upper part of these chambers are found the olfactory cells, from which nerve fibers run to the brain. When odors come in con- tact wij:h the olfactory cells, impulses are started that cause the sensation of smell. Care of the organ of smell. When the delicate olfactory cells are destroyed, they are not renewed, and the sense of smell is permanently lost. They may be destroyed by inflammation, which is often brought on by inhaling dust or by working among the fumes of acids or other chemicals. Exhaling cigarette smoke through the nose is also very injurious to the cells, and many ciga- rette smokers have little or no sense of smell. Another common cause of the loss of the sense of smell is catarrh, which ought always to be treated by a good physician and not allowed to run on from year to year. When the throat is blocked by adenoids, the odors of foods cannot enter the nose as they should, and the pleasure of eating is to a considerable extent lost. The sense of smell is valuable to us both because of the pleasure that we receive from agreeable odors and because of the warnings that come to us in the way of disagree- able odors, and we ought to try to keep it in as good working condition as possible. QUESTIONS What do we learn through the touch? What is a papilla? Explain how the nerves of touch end in the skin. Where are the nerves of touch most abundant? When we touch an object, how are the impulses started in the nerves? How do we judge whether an object is .rough or 134 PRIMER OF PHYSIOLOGY smooth ? How do we know where it is ? How do we judge of its size ? Where are the nerves of taste ? How does the food reach the nerves of taste ? Why can we not taste certain foods when we have a cold? How may the sense of taste be injured? What purpose does the sense of smell serve? What is an odor? Where are the nerves of smell? How are messages started in them? How may the sense of smell be injured? SUGGESTIONS TO THE TEACHER If the class has time for them, it will add interest to the work to perform a few simple experiments in touch, taste, and smell. Direc- tions may be found in any text of experimental psychology. Optical illusions also are interesting and they bring to the attention of the pupil the part played by the brain in sensation. In Figure 91 the iris may appear to be seen from either front or back, and other optical illusions may be found in texts of psychol- ogy or more advanced physiology. Common illusions that may be called to the pupil's attention are : the fact that the letter s and the figure 8 must be made larger at the bottom to prevent their seeming heavier at the top; that the sun and moon appear larger on the horizon than when high in the sky ; that from a railway train the landscape seems to be moving ; and that when one looks at the moon through the treetops while running, the moon seems to run with him. CHAPTER FIFTEEN FOODS AND WHY WE NEED THEM FlGS. 106 and 107. The windmill gets its power to work from the wind which blows against it ; the man gets his strength from the food that he eats. FROM my window I can see a windmill standing with its arms outlined against the sky. A little while ago it was whirling rapidly about and pumping water into the tank that it keeps supplied. Now it is standing motionless in the sunshine, as if overcome by the morn- ing heat. Is the windmill broken ? Or has anything happened to it that will keep it from any longer pump- ingVater for its owner ? Not at all. The only trouble is that the wind which supplied the power to run the mill has for the time failed. Wherever there is motion and whenever work is done, power to cause the motion and to do the work must come from somewhere. We think of a swift and heavy automobile as a powerful machine, but in reality the power comes from the gasoline that is exploded in the cylinders, and when the supply of gasoline gives out, an automobile can no more move itself than can a stone. Every other machine, whether it be run by US 136 PRIMER OF PHYSIOLOGY steam, gasoline, electricity, water, wind, or in any other way, must draw the power that runs it from some source outside itself. The windmill cannot run itself ; it must stand and wait until the wind comes to give it motion and make it able to do its work. Food as a source of power. The human body has strength. It moves and does work. It cannot furnish itself with power, however, so we must have some source FIGS. 108 and 109. Food is necessary to furnish material for the repair and growth of the cells, and to keep up the body heat. from which to draw the strength that is in our muscles. This source of power is the food that we eat. Food is necessary to give strength to the body. Without it the muscle cells cannot contract and cause the movements of the body parts. Food as fuel. A locomotive as it thunders past us glows with warmth. It gets its warmth from the fuel that is burned under its boiler. A stove with a fire in it gives off heat to all the room. This heat comes not from the stove itself, but from the fuel that is burned in the stove. Your own body is warm, as you know from FOODS AND WHY WE NEED THEM 137 feeling it. The heat of the body comes from the food that is burned within the cells. Food is necessary to keep up the body heat. Without it the temperature of the body would quickly fall to that of the air about it, and this would be fatal to the cells ; for, as you already know, the cells can live and be in health only when the temperature of the body is close to 98 degrees (page 83). Food as building material. The human body is more wonderful than any machine made by man in that it builds its own parts and keeps them in repair. The body starts as a single cell, which is composed of protoplasm, or living material. This cell builds more protoplasm, increases in size, and divides, and this process is kept up until the full-grown body is finally built of living cells which have come from the first cell. Even after the body is grown, new cells must be built ; for as long as life continues, the outer cells of the skin, the red blood corpuscles, and some of the other cells are dying and being replaced by new cells. New protoplasm is also constantly needed to repair the cells ; for within all the cells the living protoplasm is constantly breaking down and new protoplasm is being built to take its place. The material that is used in all this building of living matter comes from the food that we eat. Food is necessary to furnish material for the growth and repair of the cells. Elements found in the body. The living matter of the body is composed of at least five different elements, all built together into a material that is very different from any of them. The black solid called carbon makes up over one half of the whole. The two gases of the air, oxygen and nitrogen, together with another 138 PRIMER OF PHYSIOLOGY very light and highly explosive gas, called hydrogen, make up nearly all the remainder. In addition, some sulfur is built into protoplasm, and in the nucleus of the cell a little phosphorus is found. Among other elements that are present in the body are chlorin and five minerals, potassium, sodium, calcium, magnesium, and iron. It is not intended that you shall remember the names of all these elements, but it is intended that you shall understand that the body is made of perfectly definite materials, and that if these materials are not supplied in our foods, the body must suffer. The three classes of foods. Foods are divided into three classes, according to the elements of which they are composed. These classes are the proteins, the carbohydrates, which include the starches and sugars, and the fats. Lean meats, eggs, milk, peas, beans, and all foods made from grains are rich in protein. Potatoes, turnips, cabbage, and other vegetables are valuable mainly for their starch. Grains also contain large amounts of starch. Fruits, sweet potatoes, honey, molasses, and milk contain sugar, and we add great quantities of sugar to our foods to make it more pleasant to the taste. Fats and oils we get in butter, lard, fat meat, eggs, cheese, chocolate, nuts, and olive and cottonseed oil. In general, we get proteins and fats from animals, while from plants we get proteins and carbohydrates. From the table on page 244 you can learn the relative amounts of carbohydrates, fats, and proteins in different foods. Proteins the building foods. All three classes of foods give heat and strength to the body. The proteins fur- nish building materials in addition. They contain the FOODS AND WHY WE NEED THEM 139 same five elements that are found in the living matter of the body, carbon, hydrogen, oxygen, nitrogen, and sulfur. Since they are used for building up the cells, we should expect them to contain these elements ; for we use leather to patch a leather shoe, steel to replace a worn-out part in a machine, and to repair the body, the materials of which the body is built must be used. Minerals necessary to the body. A man excretes from his body nearly an ounce of mineral salts daily, 1 and it is FIG. no. Wild animals often travel long distances to salt-licks. Man supplies himself with salt, but he often lacks other minerals. necessary that certain amounts of the different minerals found in the body be supplied to make good this loss. In our food we always get small quantities of these min- erals, and little attention has been given to making sure that diets include a sufficient supply of them. Recent experiments show that this trusting to chance for the right amount of minerals is not always satisfactory. Not counting common salt, with which we all supply ourselves, the three minerals that may be lacking in our 1 The greater part of this mineral matter is common salt, of which the average man uses daily from one third to two thirds of an ounce. This is more than is necessary for the health, for experiments indicate that one tenth of this amount is sufficient to keep the body in good condition. 140 PRIMER OF PHYSIOLOGY food are iron, calcium (lime), and phosphorus. We shall discuss the need for each of these separately. Iron needed to build red blood corpuscles. Iron is used in the body mainly in building hemoglobin, the sub- stance in the red blood corpuscles that carries the oxy- gen. If the supply of iron falls too low, the person becomes pale and weak because of a lack of red cor- puscles and because of a lack of hemoglobin in the cor- puscles that he has. In cases of this kind the patient is given iron in liquid form as a medicine, and a little of this seems to be used by the body ; but all physicians agree that for building hemoglobin the iron in food is far more valuable than iron in other forms. The green parts of vegetables, especially spinach, are rich in iron; and, in general, eggs, vegetables, and grains, when the outer portion of the grain is used, give a rich supply of this mineral. Milk is low in iron, and in ani- mals that feed their young on milk a large surplus store of iron is laid up in the .body before birth. It is esti- mated that fifteen milligrams of iron are needed daily by a healthy man, and that the average diet contains from twelve to nineteen milligrams. 1 This indicates that it would be very easy to select a diet that would be defi- cient in this important mineral. Lime needed by the body. Careful investigation has shown that growing animals require about 1.2 per cent as much calcium as they gain in weight. When this amount of calcium is not provided, the bones are frail and the teeth are soft and defective. There must also be a certain amount of calcium dissolved in the 1 An ounce of iron would furnish the body with 15 milligrams a day for five years. FOODS AND WHY WE NEED THEM 141 fymph to keep the cells in health, and if the supply of lime be cut off entirely, life cannot continue. It is claimed that one half the people of the United States are suffering from lime starvation, and it is certainly true that many young children are not supplied with enough of this mineral. Adding a little limewater to artificial foods does not provide enough lime to be of much importance in building the skeleton and the teeth ; for a pint of limewater as strong as it can be made contains slightly less lime than is contained in a pint of cow's milk. Milk, eggs, vegetables (especially leaf vegetables), and whole grains hold the first place among the foods that are rich in lime (page 244). Lack of phosphorus in the body. Experiments indicate that from 65 to 90 milligrams of phosphorus are needed daily in the body, an amount greater than many diets will supply. The yolk of egg, the outer layer of grains, peas, beans, chocolate, and nuts are especially rich in phosphorus. Meats also supply considerable quantities of this element to the body. Larger amounts of phos- phorus are needed during the growing period than in adult life, and if this is not supplied the bones are likely to become soft. Foods rich in minerals. It is perhaps worth while to call attention at this time to the fact that the foods on which young animals live while starting in the world supply minerals as well as protein and energy-yielding substances to the body. Milk has in it all the elements, except iron, that are necessary to nourish a young animal, and an egg has in it everything necessary to build a chick, including the iron for the blood corpuscles and the lime for the skeleton. 142 PRIMER OF PHYSIOLOGY Foods which are rich in minerals ought to form a great part of our diet and be eaten by young people especially. Vegetables, also, because of the large quan- tities of them that can be eaten, furnish a rich supply of minerals to the body. In the body of an animal the lime is in the skeleton, and when we eat the meat we FIGS, ni and 112. Eggs and milk contain all the elements necessary to start a young animal on its life. get little of this mineral. 1 In wheat the mineral mat- ter is mainly 'near the surface of the grains and is not found in white flour. 2 A diet, therefore, that is com- posed chiefly of meat and white bread is low in the minerals needed by the body. Whole wheat bread, oatmeal, breakfast foods, and, in general, vegetables and fruits, are rich in minerals. Children who are fed too long on milk suffer because of a lack of iron, and a meat diet supplies less mineral to the body than a vegetable diet. The diet of children in particular needs 1 When a wolf or a fox eats a bird or a hare, it makes sure of a supply of calcium for itself by eating the bones as well as the flesh. Puppies fed only on lean meat and fat meat showed weakness of the bones, while other puppies of the same litter that were given bones to gnaw, in addi tion to the meat, developed normally. 2 The laxative effect of whole wheat bread is now believed to be due to the rich supply of phosphorus in it, and not to the irritating effects of the bran, as was formerly supposed, FOODS AND WHY WE NEED THEM 143 care to make sure that the right minerals are contained in it, for there is a special need for mineral matter when the body is growing rapidly. Generally speaking, the mineral income of the body can be increased by cutting down the amounts of meat and white bread eaten and using milk and vegetables more freely. Vitamins. Within the last few years it has been dis- covered that certain substances called vitamins are necessary for health. We do not know exactly what vitamins are, but small amounts of them are found in our foods, and a good diet must contain them. They are destroyed by cooking with alkalis, and are therefore not found in corn bread or in biscuit made with soda. We are not sure how many vitamins there are, but two are definitely known to exist. One is present in whole grains, in beans, peas, potatoes, turnips, and other vegetables, and in milk and eggs. In our country almost every one secures enough of this vitamin, but the lack of it causes a disease of the nervous system called beriberi, which is responsible for many deaths among peoples who live chiefly on rice. The second vitamin is found in milk and butter, the yolk of eggs, and the green parts of vegetables. When animals are given a diet that con- tains none of this vitamin, growth does not take place and there is soreness of the eyes ; and when the supply of vitamin is low, growth is slow and the health is poor. Many persons in our country do not get enough of this vitamin, and one of the chief reasons for the use of leaf vegetables and milk is to secure an abundant supply of it. Selecting foods. Of all the hygienic problems that confront mankind, that of selecting a proper diet is one 144 PRIMER OF PHYSIOLOGY of the most difficult. Since the health of the digestive organs must be kept in mind as well as the needs of the body for certain materials, the whole subject can be entered into more intelligently after the digestive system has been studied. In the next chapter, therefore, we shall discuss the digestive organs and their work, and shall then take up the more difficult subject of selecting a diet that will keep the human body in health. QUESTIONS Give three uses of foods in the body. Name the five ele- ments that make up most of the body tissues. Name some other elements which are present in the body. Name the three classes of foods. What foods are rich in protein ? in starch ? in sugar ? in fat ? Which classes of foods give heat and strength to the body ? Which class furnishes building material ? For what is iron used in the body ? In what foods is iron abundant ? Why is lime necessary to the body ? What foods are rich in lime ? What foods are rich in phosphorus ? Why are milk and eggs complete foods ? Why is a diet of meat and white bread deficient in minerals ? What are vitamins ? What diseases are due to a lack of them ? In what foods is each vitamin found ? SUGGESTIONS TO THE TEACHER Sherman's Chemistry of Food and Nutrition (Macmillan) gives tables of food analyses, an excellent general treatment of nutrition, and a particularly full treatment of the mineral constituents of the diet. McCollum's The Newer Knowledge of Nutrition (Macmillan) is a new book treating the subject from a very practical point of view. CHAPTER SIXTEEN THE DIGESTIVE ORGANS AND THEIR WORK ROBINSON CRUSOE on his island had plenty of goats, and from goat hair a fine waterproof cloth is woven that is used as a covering for the tops of automobiles. Yet, because Crusoe had no way of turning the hair of his goats into cloth, he was forced to wear clothes made of stiff, heavy skins and to carry an absurdly heavy and awkward skin umbrella. There were trees in abun- dance on the island, but it required much labor to con- vert them into baskets, furniture, and boats. There was clay from which all kinds of dishes and vessels could have been made, but he went for years without tasting soup or boiled food, and he counted it one of the happy hours of his life when he succeeded in making a rude vessel that would stand the fire. There were tons of sand to be had from which glass might easily have been manufactured, but he had no windows in his dwellings. All about Crusoe were materials from which a thousand articles could have been made that would have added to his comfort and enjoyment, but until these materials were worked over and changed, he could not put them to use. The meats, grains, and vegetables that we eat contain the materials that are needed for the nourishment of our bodies, but the form of these foodstuffs must be changed before we can use them. As ice must be melted before the elements that are in it can be used by the body, so must our foods be digested before they can be taken into the blood and used by the cells. Digestion is the process of breaking up nnd changing our foods into 146 PRIMER OF PHYSIOLOGY substances that can be dissolved and taken into the blood. Until this is done, our solid food is as useless to us as were most of the materials on his island to Robinson Crusoe. The digestive system. The digestive system includes the alimentary canal, the teeth, the salivary glands, the liver, and the pan- creas. The ali- mentary canal is the long passage- way through the body into which the food is taken and in which it stays while it is being digested. It is lined with a smooth mucous membrane, and in its walls are mus- cles to force the food onward intestine througn t he canal. The teeth are a mill set at the mouth of the alimentary canal to crush and grind the food into small pieces so that it will be easier to digest. The other digestive organs are glands that pour juices into the alimentary canal to assist in the digestion of the food. The whole process of preparing the food for the use of the body is a most large intestine vermiform appendix FIG. 113. The digestive system. THE DIGESTIVE ORGANS AND THEIR WORK 147 important one, and the great set of organs that carry it on fill nearly the whole abdominal cavity. The digestive glands. The digestive glands are formed by the folding of the mucous membrane that lines the alimentary canal into deep little pockets. The juices that digest the food flow out of the mouths of these glands. The liquid part of the juices is composed of water that passes through the walls of the glands from the lymph, as water passes into a sweat gland (page 85). Some glands are simple, like little wells sunk in the walls of the digestive tract. Others, FlG ' II4 ' Diagram of a simple gland " like the salivary glands and the pancreas, are branched like a tree, and the juices that come from them are se- creted by hundreds of little tubules, all of which flow into the main duct of the gland.- The glands are said to secrete when the liquid flows from them, and the liquid itself is called the secretion of the gland. The work of digestion done by enzymes. Dissolved in the secretions of the digestive glands are certain substances called enzymes. These are built up by the cells that compose the walls of the glands and are dis- solved by the liquid which passes through the cells when the glands secrete. The work of digesting the foods is done by the enzymes. An enzyme digests only artery 148 PRIMER OF PHYSIOLOGY one kind of food, so there are different enzymes secreted for breaking up the protein, fat, starch, and each of the different kinds of sugars that we eat. As we study the work of the different digestive juices, we shall speak of them as digesting the foods. You will understand, how- ever, that it is the enzymes in these juices that do the actual work of digestion. The salivary glands. There are three pairs of sali- vary glands. One pair lies under the tongue ; one pair is found under the corners of the lower jaw ; and the other pair is found in front of and below the ears (Fig. 115). These glands secrete the saliva, which is carried to the mouth by ducts 'leading from the glands. The saliva moistens the food and makes it possible to swallow food like crackers, which in a dry state would become dust in the mouth. Dissolved in the saliva is an enzyme which begins the process of digestion by attacking the starch that is in the food and breaking it up into malt sugar. The esophagus and stomach. The esophagus is the tube connecting the throat and the stomach. Food and drink do not fall down the esophagus, but are forced down it by the contraction of the muscles in the walls of the esophagus. This you can prove by drinking with your head lower than your body. The stomach stands almost on its end on the left side FIG. 115. Tne salivary glands. THE DIGESTIVE ORGANS AND THEIR WORK 149 of the body close up under the diaphragm. It holds about three pints, and when full is about a foot long. When empty, its walls are drawn together and it occupies little space. It has a double function to serve as a storehouse for food so that enough can be eaten at one time to supply the body for several hours, and to secrete gastric juice for the digestion of the food. The gastric juice. From two and one half to five quarts of gastric juice are secreted a day. It comes from the many hundreds of little glands which lie in the stomach wall and open into the stomach. The gastric juice contains an enzyme called pepsin that digests protein. It contains also an acid which kills many of the bacteria in the foods and so keeps these bacteria from causing trouble in the intestine. The acid in the gastric juice stops the action of the saliva on the starch, but in the upper part of the stomach the food may lie from one to two hours before the gastric juice works its way through it. The saliva, therefore, has a considerable time in which to digest the starch before the acid reaches it. The heat in the stomach melts the fat in the food, which assists in reducing the whole food mass to a liquid condition. The small intestine. The small intestine is coiled and folded upon itself in the abdominal cavity. It is about twenty-two feet in length and its walls are lined with thousands of little glands. These glands secrete an intestinal juice which contains several enzymes that are important in the digestion of the food. On the intestinal wall are many little finger-like projections called villi (singular, villus). These contain many blood vessels, and they absorb the digested food ; that is, they 150 PRIMER OF PHYSIOLOGY take it into the blood through the intestinal wall. So abundant are the villi that they give the entire inner surface of the intestinal wall the appearance of velvet. The liver and the pancreas. The liver weighs nearly four pounds and is the largest gland in the body. It lies on the right side of the body under the diaphragm. It secretes a greenish yellow liquid called bile, which is poured into the small intestine when food passes into the intestine for digestion. The bile assists in destroy- ing acids that come from the stomach, in making more active the enzyme that digests the fats, and in dissolv- ing the fatty foods. In the next chapter, we shall study other important functions of the liver. The pancreas is a long, light-colored gland which lies along the lower border of the stomach. It secretes and empties into the small intestine great quantities of thin, watery pancreatic juice. This liquid contains enzymes for digesting the three most important foodstuff s, pro- teins, starches, and fats. The pancreatic and intestinal juices along with the bile are thoroughly mixed with the food in the small intestine, and they are even more im- portant than the gastric juice in preparing the food to be carried to all parts of the body. The large intestine. The large intestine begins low down in the right side of the abdominal cavity, passes up the right side of the body, then across under the dia- phragm, and down the left side of the body. Just below where the small intestine opens into it, there is a small, worm-like structure called the vermiform appendix. The walls of the vermiform appendix contain much loose spongy tissue of the same kind that is found in the ton- sils, and just as tonsillitis is caused by germs growing in THE DIGESTIVE ORGANS AND THEIR WORK 151 the tonsils, so appendicitis is caused by germs growing in the walls of the appendix. the food masticated and mixed with saliva starch digested by the saliva food mixed with gastric juice ; pepsin digests proteins; fats melted and food liquefied food mixed with bile, pancreatic juice^ and intestinal juice ; pancreatic juice digests proteins, starches, and fats; sugars digested to grape sugar by en- zymes in intestinal juice food continually cut into segments and mixed with digestive juices; digestion goes on, and digested food absorbed and carried away; a few bacteria present in refuse liquids being absorbed; mucus and wastes excreted by glands ; abundant growth of bacteria continued growth of bacteria; wastes contain poisonous siibstances and should be removed from the body to prevent the poisons from being ab- sorbed into the blood FIG. 116. A diagram illustrating the changes that take place in the food during its journey through the different parts of the alimentary canal. The story of digestion. Let us now trace the history of a meal by imagining that we can see the food after it has been eaten, and that we can watch it while it is being digested. In the mouth we find that the teeth slide over 152 PRIMER OF PHYSIOLOGY each other, crush the food into small pieces, and mix it with saliva. The enzyme in the saliva at once begins the process of digestion by attacking the starch that is in bread, potatoes, and many other of our foods, and changing it to sugar. After the food has been chewed, the tongue draws it back into the opening of the pharynx. The walls of the pharynx then grasp it and press it backward and down- ward into the esophagus, through which it is carried to the stomach. When the food reaches the stomach, the gastric juice trickles in on it from the glands in the walls all about, and the pepsin attacks the meats and other pro- tein foods. Under the action of the gastric juice the outer layer of the food mass dissolves and slides on into the lower part of the stomach, where the stomach walls con- tract on it and squeeze it about to mix the gastric juice thoroughly with it. From time to time the ring of muscle that closes the gateway between the stomach and the intestine opens, and a portion of the food from the lower part of the stom- ach is forced on into the intestine in the form of a thick liquid. 1 Here a flood of digestive juices is poured in upon it. Greenish yellow bile comes from the liver ; great quantities of juice rich in enzymes for digesting proteins, starches, and fats are secreted by the pancreas ; and all along the small intestine, juices containing enzymes are poured out by the thousands of little glands that are in 1 It should be understood that during stomach digestion the food is continuously being worked downward from the upper part of the stomach, and that from time to time it passes on into the intestine in rather small amounts. It takes about six hours for the stomach to be emptied after an ordinary meal. THE DIGESTIVE ORGANS AND THEIR WORK 153 the wall. The circular muscles in the walls of the intes- tine keep contracting on the food and cutting it up into little sausage-like segments which are continually being made, combined, remade, and moved about, thus mixing the digestive juices thoroughly with the food. 1 All the time the food is gradually being worked along the in- testine and the enzymes are bringing about the following changes in it : The pancreatic juice attacks the protein and splits that which has escaped the pepsin of the stomach ; it breaks up the starch and completes the digestion of this part of the food; and it digests the fat, changing it into glycerin and other substances that will dissolve in the intestine. The enzymes in the intestinal juice assist in digesting the protein and in changing all the different sugars into the one particular sugar (grape sugar) that the body can use. And now as we follow the food in its course through the intestine, we notice that the liquid becomes less and less in amount ; that only the solid wastes remain. As some desert rivers run out over the sand and lose them- selves in their own channels, so the stream of liquid food in the intestine disappears. Where is it going? It is soaking into the wall of the intestine and passing into the millions of little capillaries that run in the wall. What will be done with it? It will be car- ried through all the body to furnish heat and strength, and to be built into bone and muscle and nerve ; for as the waterfall, even though it keep the same form, 1 The segments into which the food is cut are about an inch long, and the contractions of the muscle rings come as often as thirty times a minute. 154 PRIMER OF PHYSIOLOGY blood vessel is made up of rapidly passing water, so our bodies, that seem to us to be the same year by year, are composed of materials that are ever shifting. The skin that we have today will, in a short while, be dead and gone, and the food that we eat today will be built into a new skin. The flesh and heart and brain of an ox are built of grass, and the intestine FlG. 117. Showing the vessels which carry the food from the small intestine. human body is built of the food that we eat. The refuse matter in the large intestine. In all food there is some indigestible material likfe the woody, fibrous parts of potatoes and cabbages, the skins of fruits, and the tough fibers of meat. This matter passes from the small intestine into the large intestine, where its bulk is very considerably increased by mucus and other wastes that are secreted by the glands in the wall of the large intestine. In this waste material, millions of bacteria grow and cause decay, and in the process of decay poisonous substances are formed. Nothing is more important to the health than that this refuse ma- terial be cleared out of the intestine before the poisons are absorbed into the body. This question we shall discuss in the next chapter. Scurvy, rickets, and pellagra. The causes of these diseases are not definitely known, but they are in some way connected with the nutrition of the body, and we shall discuss them in this chapter. THE DIGESTIVE ORGANS AND THEIR WORK 155 Scurvy is a disease in which the joints are swollen and tender and there is bleeding of the gums. It is found in infants that have been improperly fed and among sailors and others who lack fresh food. It can be prevented by fresh meats and fresh vege- tables and fruits, and is relieved in a wonderful way by orange juice. Some investigators have thought scurvy to be due to the lack of a vitamin. Others be- lieve it is caused by a bacterium that is able to enter the body when it is not properly nour- ished. Whatever the cause, the disease can FlG - II8 - A milch oat - easily be prevented by proper feeding. Rickets is a disease of children in which the bones are soft. The head grows larger than is natural and be- comes somewhat square, and there are knots on the ribs on either side of the breastbone where the bone and cartilage meet. It has been suggested that rickets is due to lack of a vitamin or to a lack of calcium, but neither of these explanations seems to be correct. It is in some way connected with bad feeding and is prevented and benefited by a properly selected diet. 156 PRIMER OF PHYSIOLOGY Pellagra is common in Italy, and it is estimated that in the United States there were 165,000 cases in 1917. Most of these cases are found in the Southern states. The disease seems to spread only where the sanitary conditions are bad, and it is probably caused by a germ. At the same time, it has been proved that it is brought on by a faulty diet and that an abundant and varied diet with plenty of fresh foods will prevent it, even when sanitary conditions are bad. It seems most probable, therefore, that pellagra is caused by a germ that can attack the body only when it is in a weakened condition because of improper food. In our Southern states pellagra is a serious problem. A great number of the persons attacked by it live, during the winter months especially, chiefly on corn bread, salt pork, and molasses ; and it is very necessary that milk, eggs, and fresh vegetables be added to this diet. The garden and poultry club movements, therefore, deserve every encouragement, and the keeping of milch goats might go far toward solving the diet problem of many families. Dried milk, which seems to have all the food value of fresh milk, is now being prepared. It may be that this will prove of great value in warm regions where providing a supply of fresh milk is especially difficult. Meats will not take the place of vegetables, eggs, and milk in providing minerals and vitamins for the body (page 141). QUESTIONS What change must be made in foods before the body can use them ? What is digestion ? Name the parts of the digestive system. Describe the alimentary canal. What is the function of the teeth ? THE DIGESTIVE ORGANS AND THEIR WORK 157 Describe a gland and explain where the secretion of the gland comes from. What is an enzyme ? By what is the work of digestion done ? How many salivary glands are there and where are they ? What is the function of the saliva ? What food is digested by the saliva ? Into what is it changed ? What is the esophagus ? Describe the stomach. What is the function of the gastric juice ? What enzyme does it con- tain and what is the function of this enzyme ? How are the bacteria killed in the stomach ? Describe the small intestine. What are villi ? What is their function ? Describe the liver. What does it secrete ? What is the use of the bile ? Describe the pancreas. What food- stuffs does the pancreatic juice digest ? Describe the large intestine. What causes appendicitis ? Tell the story of the digestion and absorption of food. Where is the food taken after it is absorbed ? Of what are the wastes in the large intestine composed ? Why is it important that these wastes be promptly cleared out of the body ? Name three diseases that are due to an improper diet. What foods will prevent scurvy ? Whaf foods will prevent pellagra ? SUGGESTIONS TO THE TEACHER Additional information concerning the structure of the digestive organs and the processes of digestion may be found in Ritchie's Human Physiology (World Book Company, Yonkers, New York). A fable by John W. Ritchie called The Adventures of the Starch Family will be found helpful in giving the pupils a concrete idea of the changes undergone by the foods during the digestive and metabolic processes. Application to the World Book Company will bring a copy of the pamphlet if four cents in stamps is enclosed. Howell's Textbook of Physiology (W. B. Saunders Co., Philadel- phia) is an advanced text that will furnish a wealth of physiological information on almost any subject discussed in this book. Lusk's Science of Nutrition (Saunders) gives a very thorough treatment of nutrition. CHAPTER SEVENTEEN THE FOODS WITHIN THE BODY WE have now traced the food through its digestion. We have explained how it is taken into the blood and carried to the cells. What do the cells do with it ? W T hat becomes of it after the cells have fin- ished with it? Why, when we keep eating all the time, does not the body become so full of food that we cannot take in FIG. 119. When the candle burns tne elements in more? Perhaps it it are not destroyed. mav star t you to thinking about this subject in the right way if we go back for a few minutes to something else that you have seen. Long ago in your Mother Goose book you read : " Little Nanny Etticoat, In a white petticoat And a red nose. The longer she stands, The shorter she grows." Why does a lighted candle grow shorter the longer it stands? What becomes of the candle when it is burned ? You must study chemistry before you will have a really clear idea of what happens in the process of burning. At present we can only explain to you 158 THE FOODS WITHIN THE BODY 159 that the oxygen of the air unites with the elements of which the wax is composed and forms carbon dioxid and water, which pass off into the air. The materials in the candle, therefore, are not destroyed. They are merely changed to vapor and gas. The fate of the carbohydrates and the fats. The cells of the body take in the sugar and fats of the foods. They also take in oxygen. Within the cells the oxygen and the food unite slowly and without smoke or flame, and the food is oxidized, or burned as truly as the wax of a lighted candle is burned. This oxida- tion of the foods furnishes heat to the body and strength to the muscle cells ; and, as in the burning of the candle the wax is changed to carbon dioxid and water, so within the cells the fats and carbohydrates are changed 4 to carbon dioxid and water. The carbon dioxid is breathed out of the body through the lungs. The water is excreted by the lungs, the kidneys, and the skin. Thus the fuel foods are burned in the cells and the wastes which are formed from them are cast out of the body. The profit which the body receives from these foods is the heat and the power to do work which are given to the body when they are burned. The fate of the protein foods in the body. The living protoplasm of the body is continually breaking down and being oxidized. The protein food is used to build new protoplasm to take the place of that which is broken down. 1 In time this protoplasm will also be broken down and oxidized, so that the proteins are as 1 It should be understood that only a part of protein food is built into living tissue. Surplus protein and even part of the protein that seems to be necessary for life is oxidized as described on page 162. i6o PRIMER OF PHYSIOLOGY truly burned in the body as are the carbohydrates and fats. The difference is that they are built into living material before the oxidation takes place. Carbon di- oxid and water are among the waste products that come from the burning of the proteins, but there are other wastes also, uric acid and other similar sub- stances. These wastes are in- jurious to the cells, and the liver does a very important work in gathering up and con- verting a great part of them into urea, which is excreted from the body. 1 We shall now describe the organs that elimi- nate the protein wastes. The kidneys. Fastened to the back wall of the abdomi- nal cavity are two bean-shaped organs, called the kidneys. Each kidney has in it many thousands of little tubes which all drain into a larger tube, the ureter (Fig. 120). The little FlG. 120. The kidneys and the , -, . , . -, 1M ,, bladder seen from behind. tubes m the kidneys, like the sweat glands, are surrounded by lymph, and the water of the lymph passes into them and flows out of their mouths, as water passes 1 About 92.5 per cent of all the protein wastes excreted by the kidneys is in the form of urea. About 2 per cent of the whole is excreted in the form of uric acid, and it is estimated that an equal amount of uric acid is converted into urea by the liver. The uric acid part of the wastes comes from the nuclei of the cells and from the muscle cells when they work. THE FOODS WITHIN THE BODY i6l into a sweat gland and flows out on the skin. The urea and other protein wastes are dissolved in the lymph, and they leave the body by passing with the water through the kidney tubes into the ureter and draining off to the bladder. The function of the kidneys is to excrete water, salts, and protein wastes. Storage of the foods within the body. When more carbohydrate is eaten than is needed for immediate use in the body, it is changed to a starch-like substance called glycogen, and is stored within the cells of the liver and to a certain extent in the fibers of the muscles. When the supply of sugar in the blood runs low, this reserve store of glycogen is broken up again into sugar and given off into the blood to feed the cells. When more fat is eaten than can be used in the body, certain cells take it in and store it within themselves until they become little more than bags of oil. These cells, massed together, form the fat that you see in the body of an animal. When a person is sick and does not eat, the body uses this fat for food. A small amount of protein is dis- solved in the blood, but the great storehouse of the protein in the body is the muscles. The muscles are built up when we eat a diet that is rich in protein, and when for any FIG. 121. Fat ceils. They reason we are deprived of food, the are little more than bags of muscle fibers are broken down and used to nourish the cells of the heart, the brain, and other vital organs. Famine sufferers and persons who 162 PRIMER OF PHYSIOLOGY have come through long sicknesses are little more than skeletons because their muscles have been used to sus- tain the organs necessary for life and the fat has been used to give the body heat and strength. Surplus food in the body. When we eat more carbo- hydrate than can be stored in the liver and muscles, it is converted into fat and stored in this form. Usually we lose our appetite for carbohydrates and fats when we have had enough to furnish a reasonable supply of fat in the body. We can, therefore, in most cases trust our appetites to tell us when we have had enough bread, potatoes, fat meat, butter, or other starchy or fatty foods (page 175). There are, however, a few persons whose cells oxidize these foods very slowly, and such persons become too heavy and fleshy if they eat freely of foods of this kind. When more protein is eaten than can be used or stored in the body, it is broken up, and excreted through the kidneys. 1 From this protein the same wastes are formed that are formed from the breaking down of the protein of the body cells. A heavy diet of meat, or of other foods that are high in protein, therefore, gives the liver large amounts of protein wastes to change into urea, and sometimes more of these wastes are thrown into the blood than the kidneys can excrete. This subject we shall discuss in more detail in the next chapter. Alcohol as food. Alcohol in small quantities can be 1 In the breaking up of the excess protein, the carbon and hydrogen in it are converted into either sugar or fat and used to give the body heat and strength. It is not to be understood, therefore, that surplus proteins are entirely useless to the body. The point is that they yield only energy, and this can be obtained much more cheaply from carbohydrates and fats without filling the body with poisonous wastes. THE FOODS WITHIN THE BODY 163 used to furnish strength to the muscles. In quantities up to two ounces a day it is oxidized within the cells and gives heat to the body. Because it can be used in these ways, it is often stated that it is a food. The modern idea of a food, however, is that it must not only furnish building material or energy to the body, but that it must also be harmless when it is broken up within the cells. This definition of a food is, we think, a correct one ; for certainly the toxin of the tetanus or the diphtheria germ is not a food, opium is not a food, and strychnin is not a food. 1 Yet all these poisons are taken into the cells and are broken up in them, and they must furnish a small amount of heat to the cells. We cannot, therefore, say that alcohol is a food be- cause it is used by the cells, but before making our decision on this point we must know whether in being broken up within the cells it damages them whether it interferes with those wonderful processes that keep the protoplasm alive. When we view the question in this light, we must decide that alcohol acts as a drug rather than as a food ; for, as a drunken man shows, the action of the mind is dulled and made very uncertain by alcohol; under its influence the muscles are weak- 1 Alcohol is composed of carbon, hydrogen, and oxygen. It is made from sugar, has in it the same elements that are found in sugar, and it would seem reasonable to expect it to act as a food toward the cells. We must, however, recognize that not only what elements are in foods and drugs, but also the way they are built together, is important ; for carbolic acid is built of the same materials and is closely related to sugar and alcohol, and strychnin and cocain are composed of carbon, hydrogen, oxygen, and nitrogen, the same elements that are most abundant in protein foods. Just why substances that are composed of the same ele- ments should affect the cells so differently is hard to explain, but it is one of the facts of chemistry that we must accept. 164 PRIMER OF PHYSIOLOGY ened and their control is lost; and its whole effect on the body is that of a drug and not of an ordinary food. Even in small amounts, amounts far too small to produce signs of intoxication, there is good reason to believe that alcohol interferes with the enzymes that break up the food within the cells and throws the life processes of the protoplasm out of their natural course. 1 QUESTIONS What becomes of the materials in a candle when the candle is burned ? What happens to the carbohydrates and fats within the cells of the body ? What becomes of the carbon dioxid that is formed in the body? What becomes of the water? What does the body gain by the oxidation of the fuel foods ? What is constantly happening to the protoplasm of the body ? What happens to the protein food before it is oxidized? What 1 In the Hygienic Laboratory of the United States Government at Washington, an experiment was performed with mice and guinea pigs that gives reason for believing that alcohol does not act like ordinary foods within the cells. In this experiment, the animals were given acetonitrile, a drug that is not itself a poison but which breaks up into poisonous com- pounds within the body. When an animal was given along with the ace- tonitrile the smallest quantities of alcohol, the acetonitrile was broken up much faster than is natural and the animal was poisoned by a dose too small to have any appreciable effect when alcohol was not given. This proves that the alcohol changes the processes that go on -within the cells. It does ndt, of course, prove that they are changed in a way that is injurious when acetonitrile is not given with the alcohol, but there is a quite wide- spread belief that even small quantities of alcohol have an evil effect on the changes that *.he protein foods undergo within the cells. Until we know that this is not the case, it is unreasonable to include alcohol in our list of foods. It should be understood that the above results followed the administration of alcohol in amounts " far too small ever to cause indica- tions of intoxication and in doses which almost certainly cause no anatomi- cal lesions which could be detected by present methods." THE FOODS WITHIN THE BODY 165 wastes are formed from the proteins ? Describe the structure of a kidney. What is the function of the kidneys ? How is carbohydrate stored in the body ? Under what con- ditions will the glycogen be changed again to sugar ? How are excess sugar and fat stored in the body ? Of what use is the fat in the body ? Where in the body is protein stored ? What happens to the muscles and fat of famine sufferers ? What happens if more protein is eaten than can be used or stored in the body ? In what way is a heavy protein diet inju- rious to the body ? Define a food. Why is alcohol sometimes classed as a food ? What reason is there for not including it among our foods ? SUGGESTIONS TO THE TEACHER Review the reasons why the body needs food. Have the pupils distinguish clearly between matter and energy. Emphasize the fact that except in the building foods it is the energy and not the matter that is valuable to the body, and that the useless matter has to be thrown out of the body as wastes. The books referred to on pages 144 and 157 give full accounts of the chemical reactions within the cells and of the wastes resulting from these reactions, and Chittenden's Nutrition of Man (Frederick A. Stokes Company, New York) treats especially the question of the protein requirements of the body. Locke's Food Values (D. Appleton & Co.) gives in convenient form the chemical and energy values of average helpings of prepared foods, and Gephart and Lusk's Analysis and Cost of Ready-to-Serve Foods (Journal American Medi- cal Association, Chicago, price 1 5 cents) is of especial value to those who eat in restaurants. The teacher should write to the Child Health Organization, 156 Fifth Avenue, New York City, for table's showing the proper weights for boys and for girls of given ages and heights. Attention should be called to the fact that the weight of the body represents the food that has been taken in by the body but not oxidized the excess of income over outgo and that the weight can be increased or decreased by regulating the intake of food. CHAPTER EIGHTEEN FOODS AND HEALTH How shall we know what foods we ought to eat and how much of each is best for us ? Occasionally the idea is advanced that in selecting a diet the best plan is to follow the appetite, that the lower animals keep in health by eating the food they like, and that when the body calls for anything it does so because it needs it. It would be fortunate for us if by following this simple rule we could always be sure of keeping our digestive organs in order and of supplying our bodies with the materials that they need. But as a matter of fact this is not the case. Young rats that were allowed to eat freely of 23 different grains and vegetable foods failed to grow to more than half normal size, while other rats, compelled to live entirely on a mixture of rolled oats and dry alfalfa leaves, reached their full size. Certainly many persons crave foods that they know will be injuri- ous to them, and in the selection of foods, rules and prin- ciples must be followed as well as the appetite, if the diet is to be adapted to the body's needs. The amount of protein needed by the body has in the past been one of the most disputed of all the questions pertaining to diet,' and we shall begin this chapter by a discussion of that question. Quantity of protein needed by the body. When men are given an abundance of food and are allowed to select the kinds that they like, it is found that the average man consumes daily from four to four and one half ounces of dry protein. Some individuals eat far more and a 166 FOODS AND HEALTH I6 7 few persons take much less than this amount, but a little over four ounces is the quantity of protein eaten by the average prosperous American or European. But many persons keep in health when eating much less than this amount of protein, and recent investiga- tions have shown that proteins differ from each other and that the amount of protein needed by the body depends upon the one that is taken. In digestion the pro- teins are split into amino-acids. These are absorbed into the blood and are used as the building stones with which the body repairs its wastes and grows. Nearly twenty amino-acids are now known, which differ- ent proteins yield in different amounts; some proteins lack certain amino-acids altogether, while others they furnish only in small amounts. For its building purposes the body picks out from the blood as much of each of the different amino-acids as it needs, using the remainder for fuel as it uses sugar and fats. Meat, fish, milk, and egg proteins are complete ; they supply in large amounts all the amino-acids that the body needs. The proteins of grains, beans, and peas are low in certain amino-acids and must be eaten in large FIGS. 122 and 123. A Roman and a Japanese soldier. They made their reputations as fighters on a low-protein diet. 1 68 PRIMER OF PHYSIOLOGY amounts if they are the sole source of protein supply. Potato protein seems to be of good quality, although it is supplied in only small amounts. When a number of different kinds of foods are eaten, the amino-acids lack- ing in one food may be furnished by another, and thus all the needs of the body will be met. All the protein needs of the body can be met with vegetables, but in- cluding meat, milk, or eggs makes it much easier to plan a satisfactory diet. The proteins of soy beans and of peanuts are of better quality than most vegetable pro- teins. Gelatin is a protein of very low grade. The muscular endurance of low-protein subjects. All vegetarians live on a low protein diet. That it is pos- sible to maintain the body in health and strength on such a diet is shown by the muscular endurance of vege- tarians. In one seven-day walking race of 372 miles, two vegetarians won first and second places, beating the fastest flesh eater by 22 hours. In another great walking race of 124^ miles, in which there were thirty-two competitors, the first six men who arrived were vegetarians, the seventh and eighth were meat eaters, and the ninth, tenth, eleventh, and twelfth were vegetarians. In January, 1912, the Edinburgh Marathon race (25 miles) was won by the Finnish runner, Kolehmainen, who is a vegetarian. This same man in the 1912 Olympic games at Stockholm went to the post on six successive days against the best runners of all the world, and six times he defeated them all so easily that he is declared to be " the greatest of all Olympic heroes the best long distance runner who ever wore spiked shoes." Many other athletic contests have been won, and are FOODS AND HEALTH 169 IO minutes FIG. 124. The low-pro- being won, by vegetarians, but since in all cases of this kind much depends upon the individual, we shall give some average endurance tests that have been tried on a number of in- dividuals at the same time. Professor Irving Fisher of Yale University se- lected fifteen athletes who were living on a high-protein diet and tested their endurance. He found that on the average they were able to hold their arms extended for ten minutes. One man, who was a baseball pitcher and had powerful shoulder muscles, was able to hold his arm extended for 22 minutes. The endurance of thirty- two young men, vegetarians and low- tein subjects held their . . i . i ., -, ^ arms extended for 49 protein subjects, but not athletes, was minutes on an average . then tested by the same method, the high-protein subjects These men were able to keep their forl minutes ' arms extended on an average for 49 minutes, practically five times as long as their meat-eating competitors. One of them made a record of 200 minutes, more than nine times as long as the best high-protein athlete. Nine of the Yale athletes were then given the deep knee-bending test. On an average they were able to go through with this exercise 383 times. Twenty-one low-protein subjects were given the same test and their average record was 833 times. At a later time one of the low-protein subjects, a young man twenty-two years old, who had lived on a vegetable diet for two years, made the deep knee-bend 5002 times, 1555 times more than it was made by all the nine high-protein athletes. 1 70 PRIMER OF PHYSIOLOGY Objections to a heavy meat diet. Because meat is rich in protein, much of the discussion as to the protein needs of the body has centered about the advisability of eating meat. Some persons have insisted that it is injurious to the body and that it should not be used at all as an article of food. As we have shown, it is possible to keep the body in health with a vegetable diet, provided milk is also used, but there is no proof that a moderate amount of meat is harmful to the average person. But because meats are pleasant to the taste, very large amounts of them are sometimes eaten. This is objec- tionable for the following reasons : 1 i) Meat does not supply the minerals and the vitamins that the body needs. If large amounts of meat are eaten, small quantities of other foods will be taken and some of. the needs of the body may not be supplied. (2) Large amounts of meat in tJie diet cause poisonous substances to be formed in tJie intestine)- When more protein is eaten than the pepsin and trypsin can digest in a reasonable time, part of it passes undigested into the large intestine. Here bacteria cause it to decay, and in the process of decay poisonous substances are formed. These poisons are then absorbed into the body, and they cause headaches and other disturbances by poisoning the cells. (3) Meat does not supply the bulk that is needed in the 1 Individuals differ enormously in the kinds of bacteria that grow in the intestines and in the amount of poison formed by them, and these sub- stances are often abundant in the intestines of animals that live on a vegetable diet as well as in the intestines of meat -eating animals. Never- theless, it is true that in the average person a diet of vegetables and milk causes small quantities of the poisons to be formed, and a diet of meat and eggs causes an increased quantity of them to be formed. FOODS AND HEALTH I/I diet. The lack of bulky material causes the wastes to lie for a long time in the intestine, and this causes more of the poisons to be absorbed from these wastes than would be absorbed if they were promptly removed from the body. (4) A heavy meat diet loads tJie system with protein wastes. This is probably injurious, in some cases at least. It has long been believed by many physicians that an excess of substances of the uric acid class is the cause of gout and other serious ailments. Part of the trouble, at least, seems to lie somewhere in the protein wastes, and the patients are benefited by cutting the protein to a low point. Because of these facts it is wise to eat only moder- ately of meats and to use other articles of food more liberally than they are used when meat is taken in large amounts. The energy needs of the body. The body must have enough food to provide it with heat and with strengtJi for the work tJiat it does. A certain amount of food is burned in the body, even when the body is completely at rest. After eating, the amount of food burned by the cells is greater. When work is done by the muscles, the amount of food used is increased, enormously in- creased if hard work is done. 1 Exposure to cold causes the muscles to have a greater tension, and thus increases the amount of food burned in the body and the amount 1 The energy content of food is measured by the heat it yields when burned. The unit of measurement is the calorie, which is the amount of heat required to raise a liter of water one degree Centigrade. Roughly, it is the amount of heat required to raise one quart of water two degrees Fahrenheit. The body gets the equivalent of about 4 calories of heat for each gram of dry carbohydrate or protein eaten, and about 9 calories from 1/2 PRIMER OF PHYSIOLOGY of heat released. Cold also causes a person to move about more, and to swing the arms and stamp the feet, which increases the heat production of the body ; it may cause shivering, which brings still other muscles into use. In young persons the food is burned very rapidly in the cells, a boy or girl of ten or twelve years requiring as much food as a man or woman, and young persons of 16 and 17 years much more than middle-aged persons. Women require somewhat less food than men, and in old persons the food is not used so rapidly by the cells. Effects of a diet that does not yield enough energy. A group of young men placed on a diet that yielded in- sufficient energy continued to grow thinner until they had lost a little more than 10 per cent of their weight. After that their bodies burned less food, and they con- tinued to live on this low level without further loss of weight. They did not become ill, but they lacked vigor, and when they attempted severe muscular exercise they found that they lacked strength for it. During the recent war many millions of persons were each gram of fat. An average-sized man needs enough food to yield the following numbers of calories : Absolute rest in bed without food 1680 calories Absolute rest in bed with food 1840 calories Office work or other light work, about 2500 calories Light muscular work 2700 calories Moderately active muscular work, as work of farmer or mechanic 34 calories Hard muscular work 4000 calories Very hard muscular work 6000 calories In a boys' school where most of the pupils were from 13^ to 16 years of age, the food used had a value of almost 5000 calories for each pupil. FOODS AND HEALTH 173 forced to live on this low plane, and at all times great numbers of persons in all countries are undernourished. This is especially true of children ; among both the rich and the poor great numbers of boys and girls are under- fed. Sometimes this is because not enough food is provided. More often it is because the child is not hungry and eats only certain of the articles of food that are placed on the table. 1 Such children are in a low state of vigor, they do not grow fast enough, and it is believed that they have less resistance to infections than they would have if they were well nourished. The best indication as to whether enough food is being provided is the weight. Food for energy. Bread, grains, potatoes, butter, sugar, and fat meats are the foods on which we mainly depend for our energy. The body can use for fuel purposes any protein that is not needed for building material ; but proteins are expensive foods, and, as we have seen above, it is not wise to eat too heavily of them. The thing to do, therefore, is to eat the proteins that we need for building material and then take enough fats, starches, and sugars to give us plenty of heat and strength. Usu- ally we can trust our appetites to tell us when we have had enough of these foods. Taking food into the body increases the amount that is burned in the cells, and the amount of body heat produced. Carbohydrates in- crease the heat production least, fats increase it more, 1 The sensation of hunger is due to the contraction of the muscles of the stomach, and these muscles do not necessarily contract when the body needs food. It is generally supposed that children overeat, but far more of them do not eat enough. The trouble comes from the fact that they eat too much of sweets or other foods that gratify the appetite and refuse many articles of ordinary food. 174 PRIMER OF PHYSIOLOGY and proteins increase it most of all. A winter diet, therefore, should be higher in fats and protein than a summer diet. Meat helps to keep up the body heat in winter, and a diet consisting largely of fruits and vege- tables is advisable on hot summer days. The mineral supply of the body. This subject has already been discussed (Chapter 16). In general, eat- ing large amounts of meat and sugar causes a lack of minerals, and a diet of vegetables and milk supplies minerals. Of all the minerals, the one most commonly lacking is calcium, which can be supplied by the free use of leaf vegetables and milk. The vitamin supply. Whole grains, peas, beans, and vegetables contain abundant supplies of the vitamin that prevents beriberi. Milk is moderately rich in this sub- stance. Practically all of our population have enough of this material. The other vitamin is found in the leaves of plants, in the yolk of eggs, and in milk and butter. An animal like the cow or rabbit can eat enough grass or leaves to supply it with this vitamin, but a human being cannot do this. Milk and butter should therefore be used. The livers and kidneys of animals supply this second vitamin (it is found in cod-liver oil), and it is reported to be present in the fat of fish. General dietary principles. The seeds of plants are our chief source of food ; wheat and corn bread, break- fast foods, oatmeal, rice, macaroni, peas, beans, and nuts make up the greater part of the diet of the people in temperate climates. Fruits and vegetables like pota- toes, turnips, and carrots furnish about the same elements to the body as grains. A diet composed of these foods is likely to lack certain of the needed amino-acids, FOODS AND HEALTH 175 calcium, and the vitamin found in leaf vegetables, eggs, and milk. Meat will make good the lack in the protein, but it will not supply the calcium or the vitamin, and to make the diet complete eggs or milk, or leaf vegetables, must be used. As we have already seen, it is difficult for man to eat enough green vegetables to supply the lacking substances, and for this reason eggs and milk, especially milk, should be used. Grains, vegetables like the potato, fruits, and meat do not make a complete diet. Leaf vegetables, milk, or eggs also are necessary. The importance of milk in the diet. All who under- stand the food needs of the body are agreed that it is a great misfortune that many families are using less milk than formerly because of an increase in its price. Milk is still one of the cheapest of our foods ; a quart of it con- tains almost as much energy as a pound of steak, and it contains minerals and vitamins that can be supplied in an ordinary diet by nothing else. A certain organiza- tion that has long been at work to improve the diets of poor persons says that a quart of milk should be provided each day for a child and a pint for an adult. A noted authority on foods has stated that good ffiilk is worth whatever it costs to produce it, and that no meat should be bought until each member of the family has been provided with a pint of milk. Another authority on foods reports that in his own family from 25 to 30 per cent of all the money expended for food is used in the purchase of milk. The most serious mistake made by our people in the purchase of food is in not buying enough milk. In the southern part of the United States it is especially important that the people in small villages and in the country provide a supply for themselves. 176 PRIMER OF PHYSIOLOGY Large quantities of sugar injurious to the digestive organs. In his wild state man secured most of his sugar by eating starchy foods and digesting them to malt sugar. Now he prepares great quantities of sugar and uses it in his food, but the sugar that comes from cane and beets is cane sugar and not malt sugar. This sugar, when taken in large quantities, is very irritating to the stomach, and because in large amounts it is not a natural food for man we have but a small quantity of the enzyme that digests it. When a large amount of sugar is eaten, therefore, it may remain for a long time undi- gested in the small intestine, and when this occurs the sugar is likely to be fermented by bacteria and injurious acids formed from it. Sugar should be taken in moder- ate quantities, and it should be mixed with other foods and not eaten at a time when it will form a thick, sirupy solution in an otherwise empty stomach. A moderate quantity of candy eaten at the close of a meal has a very different effect on the digestive system from that of a large quantity taken before a meal. Fats. Fats hinder stomach digestion, and except in very cold wdather few persons can take a daily ration of more than three and a half ounces of fat without bad results. Persons who suffer from acid stomach are ad- vised to eat liberally of fatty foods, and about two ounces of fat should be included in the average daily diet. Certain individuals who refuse to eat butter, fat meat, olive oil, or other fatty foods, live on very small quanti- ties of fat, and get their energy almost entirely from carbohydrates. This leaves the lipase without any work to do and throws a heavy task on the starch-digesting enzymes, and it is not so likely to give a well-ordered FOODS AND HEALTH 177 digestion as a mixed diet. It is also believed that the cells of the body keep in better health when part of their nourishment is supplied in the form of fat ; that persons who eat little fat are more subject to germ diseases, especially tuberculosis, than are those who eat reason- able quantities of fatty foods. 1 During the war more hardship seems to have been caused by a lack of fats than by a shortage of any other class of foods. Eating vegetables beneficial to the health. Coarse vegetable foods like string beans, cabbage, cauliflower, carrots, turnips, potatoes, beets, radishes, asparagus, let- tuce, celery, and spinach are very necessary to the health. They furnish minerals to the body and after they are digested there remains much bulky refuse matter that causes the wastes to be moved rapidly along the intes- tine. These are the foods that are least palatable to most persons, and they are the ones that are most fre- quently left out of the diet. One difficulty in getting enough of these vegetables into the diet is that in the country the family garden is often neglected and a suffi- cient variety of them is not produced. Another difficulty is that in towns and cities these vegetables are often needlessly allowed to wilt in stores and markets, and their tenderness is lost before they are cooked. The chief difficulty, however, is that only a few persons un- 1 Fat is considered the most important part of the diet in tuberculosis. Outdoor life in this disease is more beneficial in cold climates than in warm climates and more beneficial in winter than in summer. Some physicians think that this is because in winter the exposure to the cold increases the appetite for fat. Milk and eggs have always been used as a source of much of the fat in the treatment of tuberculosis, and it is possible that a part of the benefits that are supposed to come from the fats in the diet is due to an abundant supply of the vitamin that is found in these foods. 1/8 PRIMER OF PHYSIOLOGY derstand how to cook vegetables so that they will come to the table with the attractive flavors and odors that an expert vegetable cook can bring out. Because it is a difficult art to do this, many housewives give their atten- tion to the easier and simpler tasks of cooking meats and of making pies, cakes, and desserts, and serve on their tables vegetables cooked in an unappetizing way. It is very, important that the proper attention be given to the raising and preparation of these foods, and every young person should learn to eat all the different kinds of vegetables that are served in his home. A plan for getting a proper diet. Since the very life of the body centers around the food from which the cells build their living substances and from which they get their energy, it is easy to understand that the question of diet is the most important problem of all hygiene. It is not possible to give any simple rules that will always be a complete guide in eating, but the following suggestions may be helpful: (1) Eat enough food. Only the energy needs of the body are increased by work, and laborers who eat large quantities of food are not nearly so likely to suffer from a lack of protein, minerals, and vitamins as those who take little exercise and eat only small amounts of food. Enough should be eaten to keep up the weight and vigor of the body. (2) Eat many different kinds of foods. As far as it is possible to do so, make it a rule to eat at each meal one food rich in protein, like lean meat, eggs, beans, or cheese ; one or more starchy foods like breakfast foods, bread, macaroni, or potatoes ; some fatty food like butter, fat meat, or nuts ; some coarse vegetable food like cab- FOODS AND HEALTH 179 bage, asparagus, turnips^ or beets ; a moderate amount of some sweet food like sugar, sirup, preserves, jelly, honey, cake, or a sweet dessert. Follow this plan, and you will probably not be tempted to eat too heavily of any one FIGS. 125, 126, and 127. Healthful sports and games do much to prevent constipation. kind of food and will supply your body with all the dif- ferent materials that it needs. (3) Include milk and butter in the diet. If this third rule is followed in connection with the two rules pre- viously given, the food needs of the body will be met. It is very important to follow some plan that will cause enough food to be eaten and all the different ma- terials that are needed to be supplied ; for experience has proved that persons who simply follow their appe- tites or eat the foods that can be most conveniently secured frequently fail to supply their bodies with some of the materials that they need. Constipation a deadly enemy to health. No matter what diet is eaten, unless the wastes are rapidly moved along the intestine and promptly cleared out of the body, ill-smelling gases and poisons will be formed in the refuse matter in the large intestine. These will be absorbed into the bloocl and cause bad breath, headaches, ISO PRIMER OF PHYSIOLOGY and other evil consequences. In selecting a diet, enough coarse food should be chosen to give large amounts of bulky refuse matter. This will assist in causing the wastes to be moved rapidly along the intestine. Other important points in the prevention and cure of constipation are vigorous exercise, especially bendings of the body and movements of the legs that will press the digestive organs about and help the circulation of the blood through them ; massage of the abdomen, which also helps the circulation of the blood through the stomach, liver, and intestines ; a daily cool or cold bath ; attending to emptying the bowels regularly at a certain hour each day 1 ; eating foods like fruits, corn meal, and graham flour, which have a natural laxative effect; drink- ing large quantities of water, especially at bedtime ; and keeping the nervous system in good condition so that the digestive organs will be properly regulated. A few physicians now understand how to treat successfully pa- tients suffering from constipation, and any one who suf- fers ill health month after month because of poisons produced in his own body should, if possible, put himself in charge of a physician who is especially qualified to treat this trouble. The cost of food. The object of eating is to supply the body with building material, heat, and strength. To 1 An X-ray examination of animals shows that before the bowels are emptied the part of the large intestine which runs across the body is raised up partially on end and the part which runs up the right side of the body is dragged across to take the place of the transverse portion. It takes about 20 minutes for these changes in the position of the large intestine to be brought about. It is possible to train the nerves that control the intes- tine until they will set the muscles of the intestine in action at regular times, and it is exceedingly important to do this. FOODS AND HEALTH l8l make sure that all the needs of the body are supplied, we must eat foods of different kinds ; we cannot live on corn meal and beans, no matter how cheap they may be. It is often possible, however, to supply the needs of the body either with high-priced foods or with other foods that may be purchased at a much lower rate. For ex- ample, the same amount of energy that can be purchased in wheat flour for four cents costs ninety-five cents in oysters, and protein costs nine times as much in canned corn as in corn meal. The average family is not wealthy, and according to the best statistics available it is slightly undernourished. We cannot go into the question of food costs further than to point out that in our country millions of dollars might be saved each year and the health of millions of people greatly improved, if the persons purchasing the food supplies of families understood how to secure the most nourishment for the money that they have to ex- pend. The average American family spends about one third of the money used for the purchase of foods for meats, fish, and poultry and less than one tenth of it for milk. Undoubtedly the diet would be improved by spending more for milk and less for meat. QUESTIONS How much protein is eaten daily by the average prosper- ous American or European ? Into what are the proteins split in digestion ? For what special purpose are ammo-acids used by the cells ? How do proteins differ as to the amino- acids they supply? Name some foods that furnish protein of high grade ; some foods that furnish less valuable protein. Give some arguments for a low-protein diet based on the 1 82 PRIMER OF PHYSIOLOGY muscular endurance of vegetarians and other low-protein sub- jects. Give four objections to a heavy meat diet. How much food does the body need? At what time of life is most food required ? What is the result of living on a diet that does not supply enough energy? What shows whether enough food is being provided ? Is your weight what it ought to be ? What foods furnish an abundance of minerals to the body? What foods are rich in each of the vitamins ? Name some of the chief energy-yielding foods. What class of foods most increases the heat production of the body ? What foods can be used to increase the heat production of the body in winter ? What foods will keep the amount of body heat produced lowest in hot weather ? What other classes of foods supply the same materials as seeds ? What needed substances are lacking in these foods ? Explain how each of these substances may be supplied. Why is it important that milk be used freely? Why is sugar injurious to the stomach and intestines when eaten in large quantities ? When is the proper time to eat candy ? How much fat should be included in the daily ration? Why is it unwise to depend entirely upon carbohydrate foods for energy and to exclude fatty foods from the diet? Why are coarse vegetable foods necessary for the health ? Give some of the reasons why these foods are often omitted from the diet. Give three rules for eating that will help in giving the body a proper food supply. Why is it important that some plan be followed in supplying the body with food ? Why is it necessary for the wastes to be promptly removed from the intestines ? How do coarse, bulky foods assist in this ? Give some important points in the prevention and cure of constipation. How does a knowledge of foods help in se- curing a satisfactory diet at a moderate cost ? .CHAPTER NINETEEN THE TEETH THE teeth are composed of the hardest tissues in the body, but decay of the teeth is the most common bacte- rial disease of man. Unlike many other infections, this disease runs on and on, and can be checked only by a surgical operation that removes the infected tissues and the germs that are in them. We have therefore a whole class of surgeons (dental surgeons) who give their entire time to the treatment and prevention of infections of the teeth and their surrounding parts. In recent years it has been proved that defective teeth are more injurious to the health than had been suspected, and the importance of keeping the teeth sound can hardly be exaggerated. How bad teeth injure the health. Bad teeth cause the food to be swallowed in large pieces and thus greatly delay digestion. They also allow germs to gain entrance to the bones of the jaw and establish centers of infection in these parts. These germs are usually slow-growing races of streptococci that live in the bones for years, and often the health is greatly injured by the toxins that are absorbed from them. Frequently the germs are carried from the teeth to other parts of the body and by grow- ing in these parts cause rheumatism, heart disease, kid- ney disease, and other ailments. This subject will be discussed in a later chapter (pages 233 and 242). The structure of a tooth. A tooth is composed of a crown, a neck, and one or more roots. The main bulk of the tooth is composed of dentine, or ivory, a substance harder than the most compact bone. The crown is cov- ered by a coat of enamel. This substance is very hard, 183 1 84 PRIMER OF PHYSIOLOGY enamel dentine bone but brittle like glass. The enamel can easily be broken by biting on hard objects, and it may be cracked by very hot food or drink taken into the mouth. If it is once broken off it is never replaced, and without the covering of enamel over it the den- tine soon decays. The roots of the teeth stand in sockets in the jaw-bones and are covered by a layer of bone-like cement. Lining the socket in which the root stands is a layer of connective tissue that fastens together the root and the bone of the jaw. In the center of the tooth is the pulp cavity, a bundle of nerves, veins, and arter- little chamber containing iesfor pulp nerves an d blood vessels. FIG. 128. A section through a tooth Break open, the tooth of showing its structure and how it is fas- an an i ma l an d you will tened into the jaw-bone. easily find the enamel, the dentine, the pulp cavity, and the little root canals through which the nerves and blood vessels enter from the jaw-bone. Why a tooth decays. Decay of the teeth is caused by bacteria that grow in the materials that stick to the teeth and lodge between them. It is thought that the bacteria start the decay by forming acids that eat away the enamel. Then other kinds of bacteria enter the cavity and destroy the dentine. If the decay is allowed to go on until the pulp is reached, this is killed and the THE TEETH 1 85 germs not only grow in the dead pulp but enter the jaw- bone through the root canal and set up their growth about the end of the root. When the decay is reaching the pulp, but when the nerve endings in the pulp are not yet dead, the tooth may ache. A gum boil is due to infection at the root of a tooth. The teeth preserved by keeping them clean. The way to preserve the teeth is to keep them clean, so that bacteria cannot find a home around them. The teeth should be brushed both inside and outside after each meal, and food that is lodged between them should be carefully removed. This point is important because decay nearly always begins between the teeth. Some dentists recommend that the food be removed with den- tal floss, but in the hands of the average person a tooth- pick is more effective. A quill pick is less likely to injure the gums than a wooden or metal one. Rinsing water about vigorously in the mouth and driving it be- tween the teeth removes many small food particles, and this should always be done after the teeth have been brushed. A good tooth powder or paste is an aid in cleaning the teeth. Prepared powders or pastes may be used, or a good powder made of precipitated chalk and powdered orris root, which may be pur- chased from any drug- gist. Charcoal, pumice stone, or other gritty substances should not , , , , FIG. 129. A curved brush with the bristles be used, as they scratch longer at the ends cleans ^ teeth lieMKr than the teeth and leave a straight brush. 1 86 PRIMER OF PHYSIOLOGY little grooves in the surface where food and bacteria collect. A curved brush with the bristles longer at the FlG. 130. One half of the permanent set of teeth. ends cleans the teeth better than a straight brush ; a medium-sized brush with moderately stiff bristles should be used. Deposits on the teeth. The mucus of the saliva forms a film over the teeth, and in many mouths patches of gummy material collect on the teeth where they are not cleaned in chewing the food and by brushing. These deposits are called dental plaques, and they are filled with living bacteria that produce acid and start decay beneath the plaques. Tartar is a hard mineral deposit that usually forms most abundantly along the edge of the 'gums. It is often stained brown by the escape of blood into it and may become bluish, green, or almost black from changes in the coloring matter of the blood in it. Thorough brushing of the teeth helps to keep them free from dental plaques and tartar, but these may ap- pear on places where the brush cannot reach them or THE TEETH 187 even, in spite of the most careful cleans : ng, where the brush does reach. It is important, therefore, to visit a dentist from time to time to have any deposits on the teeth removed. The care of the gums. In many persons the gums are slightly inflamed along the margins and bleed easily when they are brushed. To keep them in health it is very important that tartar on the teeth be removed, for the tartar irritates the gums and causes them to shrink, leaving the roots of the teeth bare. This inflammation and receding of the gums may allow germs to work down about the roots of the teeth and form pus about them, thus causing them to become loose in their sockets. When the teeth are cleaned, the gums should also be thoroughly brushed with a light, quick stroke that will stimulate the circulation in them but will not injure them. One dental authority states that inflamed gums can be surely restored to health if the gums and teeth are brushed in the proper manner for two minutes four times a day. Some writers advise that in cleaning the back teeth the brush be given a twisting movement, and that the brushing be always from the gums toward the crowns of the teeth. Others believe that the outer surfaces of the back teeth can be best cleansed by giving the brush a circular or rotatory motion. All authorities are agreed that the brushing should not be crosswise on the teeth. The purpose of brushing is to prevent cavities from forming in the teeth and to keep the gums in health, and the brushing should be frequent enough and thorough enough to accomplish this purpose. It is best to have, two tooth brushes, as a brush becomes soft when too frequently used. 1 88 PRIMER OF PHYSIOLOGY The importance of visiting the dentist frequently. It is very important that the teeth be inspected by a den- tist at regular intervals and be given any treatment they may need. If the dental plaques are not removed, decay may start beneath them. Tartar that is not re- moved irritates the gums and causes them to become inflamed and to shrink. A most necessary part of the care of the teeth, therefore, is to have any deposits on them removed promptly, and a dentist should exam- ine the teeth every three months to see if this needs to be done. It is also important that cavities be filled while they are yet small, both because this plan preserves the teeth and because it is more economical and less painful than waiting until the cavities have enlarged and a great part of the tooth has been eaten away. All over the land people are suffering with toothaches and paying for ex- pensive X-ray work, root fillings, and crown and bridge work when they could have preserved their teeth by spending a mere fraction of the same money at an earlier date for small fillings. If the pulp of the tooth dies and the germs gain entrance into the bones of the jaw, it is exceedingly difficult to eradicate them and sometimes it is impossible to do so. It is not considered safe to fill a dead tooth unless the X-ray is used to make sure that the filling extends to the end of the root canals ; even after the roots are filled it is considered advisable to put a tem- porary filling in the tooth, and after a time to examine it again with the X-ray to make sure that no infection has developed in the bone at the tips of the roots. Dental work of this kind is very expensive, and it is much more satisfactory to have the teeth attended to when only THE TEETH 189 cleaning and small fillings are required. Unless decayed teeth can be so treated that they will be free from germs, it is better to have them extracted, and there are not a few dentists who believe that a dead tooth is better out of the mouth than in it. The temporary teeth. The jaws are too small in child- hood to hold the large teeth that we need in later life. In early life we have, therefore, a set of twenty small temporary teeth. This set is composed of four incisors, two canines, and four molars in each jaw (Fig. 132). The incisors are flat and chisel-like for biting off the food. The canines are more round and pointed, and in the dog and other carnivorous animals they are used as weapons and for tearing flesh. The molars are broad, square teeth with square cusps, or points, and wide sur- faces for crushing and grinding the food. About the sixth year the temporary teeth begin to drop out, and by the twelfth or fourteenth year they have all been replaced by permanent teeth. The permanent teeth. There are thirty-two perma- nent teeth. In each jaw there are four incisors and two canines that replace the incisors and canines of the temporary teeth ; four bicuspids in place of the temporary molars ; and Six molars that Come FIG. 131. The tooth on the right de- in behind the Space OCCU- ca y ed . the roots were not absorbed, and . , . the tooth had to be pulled to make room pied by the temporary for the permanent tooth. The tooth in teeth. The first perm a- the middle shows the roots partly ab- nent molars appear about f /*- J he roots f * e < ooth ! r _ left have been completely absorbed and the sixth year. The third the tooth has dropped out. 1 90 PRIMER OF PHYSIOLOGY incisors 5~8 canine molars molars, or wisdom teeth, usually appear from the six- teenth to the twenty-first year, but in some persons these teeth never make their way through the gums. 1 The importance of caring for the temporary teeth. The first reason for caring for the temporary teeth is that they themselves are nec- essary for the health ; for if they are allowed to de- cay, the child will form the habit of bolting his food ; the digestion will be deranged by the germs that are swallowed ; and FIG. 132. The upper temporary teeth of a child about three years old with the tne nerVOUS System and average time of eruption given in months, the disposition will be weeks earlier than the upper. The first permanent molars, which at trlis time are being formed in the jaws, are. shown be- hind the temporary teeth. 20-32 j j > .-, dama g ec b Y from the toothache that {-foe child will be COm- - ._, pelled to endure. For the sake of the health during the years of -childhood and to prevent the forming of wrong eating habits, the tem- porary teeth should have the best of care. The second reason for caring for the temporary teeth is to prevent the permanent teeth from coming in irreg- ularly. The permanent teeth begin to form long before 1 Sometimes when the wisdom teeth or other teeth fail to appear at the normal time it is because they have turned sideways in the jaw or have become tightly wedged among the roots of the other teeth. Teeth that are lodged in the jaw in this way are called impacted teeth, and there are many cases on record of persons who suffered greatly from nervous troubles because of the pressure such teeth were exerting. If the teeth do not ap- pear at the proper time and there is any trouble with the health, impacted teeth should be looked for. The X-ray is used in making the examination. THE TEETH birth at the roots of the temporary teeth, and by the end of the third year even the wisdom teeth are formed in the jaws. These teeth then gradually grow and harden, and the roots of the temporary teeth disappear before them (Fig. 131). Finally, the roots of the temporary teeth are entirely absorbed and the first teeth drop out, leaving the places they occupied to the permanent teeth. If the temporary "" 7-9 incisors canine bicuspids molars FIG. 133. The upper permanent teeth of a man twenty-six years old, with the average time of eruption given in years. The lower teeth usu- ally appear two or three months earlier than the corresponding upper ones. teeth are allowed to decay, their roots are not absorbed before the permanent teeth. The second teeth, therefore, either re- main buried in the jaws or appear in an irregular line, some inside and some out- side of the line of the first teeth. Another difficulty caused by decay and loss of the temporary molars is that when the first permanent molars come in they move forward and take positions that belong to the bicuspids and there is then not enough room for the per- manent bicuspids. For the sake of the permanent teeth, therefore, the temporary set should have the best dental care, and if for any reason they have been allowed to de- cay, a dentist should be consulted when it is time for the second teeth to appear. Permanent fillings and not cement fillings should be used in the temporary teeth, for some of these teeth remain in the mouth until the child is 10 or 12 years of age. 192 PRIMER OF PHYSIOLOGY canine incisors incisors bicuspids first molar canine first molar bicuspids FIG. 134. The jaws of a child four years old. The jaw-bones have been cut away to show the permanent teeth growing at the roots of the temporary set. The importance of caring for the first permanent molars. The first permanent teeth, which come in about the sixth year, behind the tem- porary molars, are of- ten mistaken for tem- porary teeth. These molars have deep grooves in their sur- faces in which the food lodges, and they come into the mouths of many children before the habit of washing the teeth has been formed. They are therefore especially liable to decay. They should be filled at once if cavities appear in them, because they are not replaced when lost, and without them the jaws do not grow in length as they should. Count the double teeth in the mouth of a six- or seven- year-old child, and if there are three of them on one side of the jaw, the back one is a permanent molar. Other points in the care of the teeth. Sticky foods like oatmeal and mashed potatoes cling to the teeth and cause them to decay. Hard foods like apples, cornbread, and bacon clean the teeth and give the gums the exercise that is needed to keep up the circulation through them. Every diet, therefore, should contain some tough, solid material into which the eater can set his teeth. Sugar left among the teeth ferments easily and causes decay. For this reason eating candy at all hours of the day, so that the crevices among the teeth are kept filled with it, is almost sure to cause decay. THE TEETH 193 Straightening irregular teeth. Often the permanent teeth come in irregularly and are turned forward in front because the temporary teeth have been allowed to decay or because adenoids or nasal growths have kept the bones of the jaws and of the roof of the mouth from growing enough to make room for the teeth. When for these or any other reasons the teeth are ir- regular, a dentist who understands how to straighten them should at once be consulted. By putting pressure on the teeth the bones may be made to grow larger and the arch of the jaw ex- panded until the teeth have sufficient room. Figure 136 gives an idea of the changes that a good dentist % FIG. 135. This shows how the upper teeth Can make in the ap- should close on the lower teeth. (After a Of a person photograph from " The Practical Ortho- , , , dentist") whose mouth is spoiled by irregular or protruding teeth. The work of straightening the permanent teeth ought to be begun as soon as they appear, and not delayed until all of them are in the mouth, as is often advised. A tooth that has been crowded out of line ought not to be pulled, but the circle of the teeth should be widened until there is room for all. Defective teeth due to illness and to lack of calcium in the diet. A tooth is first built up by the growth of a "bud," or little group of cells of the mucous mem- brane which covers the jaw. It is then hardened by having calcium deposited in it. This hardening of the teeth is going on all through childhood, and severe cases 194 PRIMER OF PHYSIOLOGY of scarlet fever, measles, diphtheria, and other illnesses may interfere with the deposition of lime and cause the teeth to be soft and ilHormed when they come through the gums months or years later. Defective teeth may also be caused by lack of cal- cium in the diet, as we have already pointed out (page 140). It is therefore especially important to the teeth FlG. 136. Two cases in which the teeth needed and received the care of a good dentist. {After a photograph from " The Practical Orthodontist.") that children be guarded from disease and that an abun- dance of lime be supplied in the food during the early years of life. The question of lime in the diet should be given special care when babies are brought up on any food other than milk. Care of the mouth of an infant. Little babies often suffer from sore mouth. This disease is caused by germs and is usually brought on by lack of cleanliness. It should be promptly attended to by a physician, be- cause it not only causes suffering and nervousness in the child but also fills the alimentary canal with germs THE TEETH 195 and ruins the digestion. When the teeth are making their way through the gums, the mouth should be ex- amined to see that there are no little ulcers on the gums when the teeth are cutting through. If these are found a physician or a dentist should be consulted ; for it is very unwise to allow a child to go on swallowing the many thousands of pus-forming germs that come from the ulcers. One of the best means of preventing trouble in the mouth of a baby is to wipe out the mouth, after feeding, with a clean cloth that has been dipped in a sat- urated solution of borax or boric acid. Decayed teeth very common. Among the 846 children examined in a school in Cleveland, Ohio, only three had perfect teeth. Examinations of many thousands of other children show that often as many as 95 per cent of them are in need of dental care. The great majority of young persons lose their first permanent molars before they are twenty years of age, and it is undoubtedly true that no other part of the body is so often defective as the teeth. You should be on guard, therefore, to pre- serve the precious heritage which nature has given you in the form of your teeth ; for your chances of health in later years depend very largely on the care that you give your teeth now. Keep them clean by all means, and if there are small cavities in them, have them filled at once. v QUESTIONS In what two ways do bad teeth injure the health ? Name the parts of a tooth. Of what is the body of a tooth com- posed? With what is the crown covered? How may the enamel be injured? What results usually follow breaking 196 PRIMER OF PHYSIOLOGY the enamel ? How are the teeth fastened in the sockets ? Where is the pulp cavity ? What does it contain ? What causes decay of the teeth ? What happens if the decay continues until the pulp is reached ? How may decay be pre- vented? Why should particles of food that lodge between the teeth be removed? How may a good tooth powder be made ? Why should gritty substances not be used to clean the teeth ? What kind of brush is best for cleaning the teeth ? What are dental plaques ? What is tartar ? Give two important points in keeping the gums in health. How should the brush be used in cleaning the teeth ? How often should the teeth be brushed ? Why is it important to visit the dentist regularly ? Why should dental plaques be removed? Why should tartar be removed ? Explain why it is important to have all cavities filled while they are small. How many teeth are there in the temporary set ? Name and describe the different kinds. How many teeth are there in the permanent set ? When does the first permanent molar appear ? Give two reasons for caring for the temporary teeth. Why are the first permanent molars especially liable to decay ? Why is their loss harmful ? Why are hard foods better for the teeth than sticky foods ? Why is constant candy eating injurious ? How do adenoids and nasal growths affect the teeth ? What should be done when the teeth are crooked ? How may illness during child- hood injure the teeth ? What element needed for building the teeth is sometimes lacking in the diet of children ? When babies have sore mouth, what is usually the cause ? What trouble should be guarded against while the teeth are coming through the gums? HOW can trouble in a baby's mouth be prevented? Cite some facts to show how common defective teeth are. CHAPTER TWENTY TOBACCO FIG. 137. The peace pipe. WHEN Columbus returned from the West Indies, he reported that the natives carried with them to kindle fires a brand made by rolling in corn husks the leaves of a certain herb which they cultivated. He also reported that they perfumed themselves with the leaves of this herb, and that no treaty of peace could be ratified among the Indians without smoking the herb in a pipe, because they believed that when the smoke of its burning as- cended to heaven the Great Spirit smelled a sweet savor and was pleased. The use of this Indian herb became popular in England through the influence of Sir Walter Raleigh, and the custom of using it spread rapidly through Europe in the seventeenth century. At first it was thought to have medicinal value, but in a short time men of intelligence and high position came to think of it as a dangerous drug and became alarmed as to the consequences that 197 198 PRIMER OF PHYSIOLOGY would follow its widespread use. 1 A great movement against the new custom then sprang up over all the known world. In Turkey the pipes of smokers were thrust through their noses ; in Russia the noses of smokers were cut off, and those who repeated the offense were put to death ; the church threatened the users of the weed with excommunication ; and King James of England issued a protest against its use, in which he declared it to be " a custom loathsome to the eye, hate- ful to the nose, harmful to the brain, dangerous to the lungs, and in the black, stinking fume thereof nearest resembling the horrible Stygian smoke of the pit that is bottomless." Why the habit of using tobacco is so widespread. In spite of all the opposition that has been offered to it, tobacco is now used over practically the whole world. In the United States the people spend for it more than four hundred millions of dollars yearly. Of course, if people spend their money in this way, it means that they will be compelled to go without-food, clothing, furniture, books, music, and other things that for their health, comfort, and richness of life they ought to have ; it means millions of extra years of labor for a people who are already overworked. In India all ages and both sexes are constant smokers, and in China many of the workmen carry with them as their constant compan- 1 During the seventeenth century the plague, or " Black Death," ravaged Europe, and it was generally believed that smoking was a safe- guard against this disease. It is possible that there was some foundation for this belief ; for the plague is spread by fleas that come from plague- infected rats, and it may be that fleas dislike the odor of tobacco that is present on the clothes and skin of tobacco users. TOBACCO 199 ions a supply of tobacco and a pipe. Yet in Inch* a and in China the great mass of the people toil for a miserable wage that will hardly keep them alive, and in years of crop failure hundreds of thousands of them actually perish for lack of food. Why do men put this extra burden on themselves ? Why did the Indians that Columbus saw perfume them- selves with the odor of tobacco ? Why do men now engage in the seemingly foolish custom of drawing smoke into the mouth and puffing it out again ? Let us search out the answer to this problem. Nicotin. There are certain drugs that produce such pleasurable effects on the mind that people form the habit of taking them to experience these effects. Among these drugs may be mentioned hasheesh, which comes from Indian hemp and is used by the people of India. It produces a kind of intoxication and fills the mind with the most brilliant ideas of grandeur and power, causing the most pitiful specimen of humanity to feel himself a very king among men. Alcohol has something of this same effect, for it deadens the judgment and the critical powers of the mind and causes a person to regard his own efforts as brilliant, even when there is no ground for a high opinion of what he has done. Opium deadens the sensibilities to pain and produces sensations of de- licious ease and luxury. Cocain, chloral, and a few other drugs produce effects that are pleasant to the mind, and men fall into the habit of taking them. The most widely used of all these drugs, however, is nicotin, which is present in tobacco. The sensations produced by it will be discussed in a later paragraph. Nicotin a narcotic. Physicians speak of certain drugs 200 PRIMER OF PHYSIOLOGY as stimulants and of certain others as narcotics. Stimu- lants quicken the action of the protoplasm of the cells ; they make the muscles contract more strongly and cause the nervous system to conduct impulses better and to control the body with a firmer hand. Narcotics deaden the nervous system and weaken its action ; they slacken the muscles and lessen their strength. Strych- nin is a good example of a stimulant. It is given by physicians when the heart action flags and when there is general weakness and collapse. Opium is an example of a narcotic. It is given by physicians to dull the senses to pain and to quiet those whose nervous sys- tems have been overwrought. The nicotin that is in tobacco is a narcotic, and it is so strong that a few drops of it introduced into the mouth will paralyze the nervous system and stop the beating of the heart. 1 We shall now discuss some of the more important effects of nicotin on the body. The influence of tobacco on growth. There are many indications that the processes within the cells that cause growth differ from the processes that go on during the repair of the protoplasm. That is, in cells and in young people that are growing, there are processes going on that are not going on in cells and in persons 1 Tobacco is from I to 4 per cent nicotin. In chewing, only a small part of the nicotin in the tobacco is absorbed into the body, and in smoking, most of the nicotin is broken into other compounds. It is probable that these other compounds produce a large part of the effect that follows smoking. That men smoke to obtain the drug effects of nicotin and of the compounds that come from the nicotin, and not for the physical and mental pleasure of the smoking, is shown by the fact that a smoker is not satisfied with tobacco from which the nicotin has been extracted. TOBACCO 201 that have reached their full size. 1 Tobacco seems to have an especially evil effect on the processes of growth ; for without doubt it is most injurious to the young. Two young guinea pigs that were made to inhale tobacco smoke from the fourth day after birth, on the forty-fourth day weighed 174 and 169 grams respectively instead of 330 grams, which is the normal weight for a guinea pig of this age. One of them died on the forty-fourth day, and the other was not subjected to further inhalations. At the end of the third month this animal weighed only 295 grams. The normal weight at that age is 485 grams, so the animal was still stunted and far below its normal size. So generally is it known that cigarette smoking inter- feres with the processes of growth and stunts the young that most of our states have laws forbidding the sale of cigarettes to boys below a certain age. In 1889 the Japanese government became alarmed because of the small size of some of its citizens, and after an investi- gation of the effects of tobacco passed a law which was worded thus : " Smoking of tobacco by persons under the age of twenty is prohibited." Professor Seaver of Yale University found that of the young men entering Yale during a period of ten years, the smokers averaged 15 months older than the non-smokers, and that notwithstanding their greater age they were one third of an inch shorter and had slightly less lung capac- ity. The boy who wishes to become large and strong 1 By experiments on animals it has been found possible to feed them in a way that will keep them alive, but will not cause growth in them. This indicates that the processes of growth and of maintenance are different. 202 PRIMER OF PHYSIOLOGY should let cigarettes alone during his growing years, for there is every reason to believe that young smokers fail to reach their full development either of body or of mind. The effect of tobacco on the muscles. As we should expect, tobacco weakens and relaxes the muscles. Pro- fessor Lombard of the University of Michigan tested the strength and endurance of his finger muscles on four days on which he smoked five cigars daily; then on four days on which he abstained from smoking; then again on four days when he smoked as on the first days. He found that on the days he smoked, his muscles had lost on an average 41 per cent of their working power. The fact that tobacco softens and slackens the muscles was so well known before the days of chloro- form that patients were prepared for certain surgical operations by giving them tobacco to bring about a relaxed condition of the muscles. At the present time, it is well known among athletes that smoking lowers the strength, and athletes who are in training are not allowed to indulge in tobacco. Cigarettes will surely kill the baseball pitcher's speed ; they shorten the flight of the football player's punt ; and- the tobacco user's muscles weaken and fail when the crowning effort of the race comes. The effect of tobacco on the nervous system. The most serious effects of tobacco are on the nervous sys- tem. It interferes with the control of the muscles, and it damages the mind, as we should expect a narcotic to do. The trembling that may be seen in the hands of almost any one who smokes cigarettes to excess shows in a very marked way how tobacco interferes with TOBACCO 203 the control of the muscles. Because of this effect, tobacco users are not good marksmen with the rifle, and many of them are unable to do delicate work. The following statement by Luther Burbank, the great plant breeder and nurseryman of California, illustrates this point: " To assist me in my work of budding work that is as accurate and exacting as watch making I have a force of some twenty men. I discharge men from this force at the first show of incompetency. Some time ago my foreman asked me if I took pains to inquire into the habits of my men. On being answered in the nega- tive, he surprised me by saying that the men I found unable to do the delicate work of budding invariably turned out to be smokers and drinkers. These men, while able to do the rough work of farming, call budding and other delicate work ' puttering ' and have to give it up, owing to inability to concentrate their nerve force. Even men who smoke one cigar a day I cannot intrust with some of my delicate work." The effect of tobacco on the mind is even more notice- able than its effect on muscular control. A study of the grades of 500 boys in private schools shows that the grades of smokers were on an average 12 to 15 per cent lower than the grades of non-smokers. Another set of statistics covering sixteen schools in different parts of the country and including 800 boys showed that the smokers had fallen on an average 17 to 28 per cent behind those who did not use the drug. A comparison of 50 smokers and 50 non-smokers chosen at random in Kansas State Agricultural College showed that the smokers had averaged 28 per cent lower in grades and 204 PRIMER OF PHYSIOLOGY that they had made 74 per cent of all the failures that were made by the 100 boys. Many other comparisons of the scholarship records of tobacco users and non-tobacco users have been made, and in every case the tobacco users stand far below the others in scholarship. So well known is it that tobacco interferes with good intellectual work that many large corporations absolutely refuse to take into their employ young men who use cigarettes. Judge Stubbs of Indiana gives a list of twenty-two great employers who follow this rule. The list includes Marshall Field & Co., John Wanamaker, and seven great railroads. How tobacco affects the mind. Tobacco undoubtedly injures the mind, so that the person using it learns less rapidly and thinks less clearly. Those who have used it for some time have a tendency to become nervous, restless, unable to remain still for any length of time, and unable to keep their minds concentrated on any one subject. As one writer expresses it, " The mind of a tobacco user seems to lose its grasp of -things." It is probable, however, that the main reason why tobacco users fall behind other men in intellectual work is that nicotin steals away ambition. Its first effect on the mind is to lull it to rest ; to make one contented with himself and his achievements ; to make one satisfied to sit and watch the smoke curl upward while other things take care of themselves. 1 This feeling of ease, comfort, and freedom from responsibility is very pleasurable, and the tobacco habit is the most common of all the drug habits to which man is addicted. In summing up the 1 "Under the influence of tobacco, thought becomes reverie." VICTOR HUGO. TOBACCO 205 good or the evil which comes from a habit of this kind, however, we must always remember that the world's work must be done, and that when a drug .for any rea- son interferes with the working powers of a man, some one else will probably be compelled to do the work which he ought to have done. We must also remember in connection with all drug habits that it is important to know whether we are to be forced to pay with the health of our cells for the pleasurable sensation that the drug gives. Other effects of tobacco on the body. Dyspepsia is very common among tobacco chewers who swallow small quantities of the juice and among those who damage their nervous systems by excessive smoking. Another effect of the continued use of tobacco is to raise the blood pressure^ which greatly increases the work of the heart. Smoking also has a bad effect on the air passages ; for the hot ammonia and other compounds in the smoke frequently cause "smoker's sore throat," and cancer of the tongue and throat is more common among smokers than among non-smokers. Besides all these effects on separate organs of the body, the nicotin has a depressing and weakening effect on the body as a whole, just as it has an enfeebling and quieting effect on the mind. The effect of a moderate use of tobacco. In reading this chapter you must bear in mind that not all the evil effects of tobacco that have been described come at once, nor is it possible to observe all of them in every person who is a tobacco user. Small doses of any drug produce proportionately smaller effects than do larger doses, so persons who use tobacco moderately suffer 206 PRIMER OF PHYSIOLOGY less from it than do persons who use large amounts. The superintendent of the reform school at Westboro, Massachusetts, says, " All boys sent here have been users of tobacco." The chief probation officer of the juvenile court of Washington, D.C., says, " In dealing with more than 16,000 delinquent children of this city during the last eight years, I find as a rule that the user of cigarettes is a stunt, a weakling in body, mind, and morals." In Chicago, of 2402 cigarette smokers in the grades below the high school, only 6 per cent were doing their school work well enough to pass. These are the effects of tobacco when used to excess or when used by the young, and persons who have experience with cases of this kind naturally regard tobacco as one of the worst enemies of mankind. Others who see men all about them smoking and yet attending to their work day by day often take the view that after all the tobacco habit is of little consequence. The truth is that some men are born with more health, strength, ambition, and intelligence than others, and that one of these strong men, even after using tobacco for a long time, may still have more strength and brain power than the man who lacked these qualities from his birth. The question is not, however, whether the strongest tobacco user has more strength than the weakest man who does not use tobacco. The question is whether the strong man is able to use tobacco and at the same time realize the. full strength of his body and of his mind. Everything that we know about the effect of nicotin indicates that it is not possible to do this ; that it is a violent poison to the cells ; that if taken into the body TOBACCO 207 in large amounts, it will cause death ; that if constantly taken during the growing years, it has a very disastrous effect on development ; that in any amount whatsoever it has a narcotic effect on the muscles and on the delicate cells of the brain ; and that any one who uses it will be damaged by it. Why a boy should not use tobacco. " Your first duty in life is toward your afterself- the man you ought to be. So live that he in his time may be possible and actual. " Far away in the years he is waiting his turn. His body, his brain, his soul, are in your boyish hands. He cannot help himself. " What will you leave for him ? " Will it be a brain unspoiled by lust or dissipation, a mind trained to think and act, a nervous system true as a dial in its response to the truth about you ? Will you, Boy, let him come as a man among men in his time ? Or will you throw away his inheritance before he has had the chance to touch it ? Will you turn over to him a brain distorted, a mind diseased, a will untrained to action ? " Will you let him come, taking your place, gaming through your experiences, hallowed through your joys ; building on them his own ? " Or will you fling away his hope, decreeing wanton- like that the man you might have been shall never be ? " This is your problem in life ; the problem of more importance to you than any or all others. How will you meet it, as a man or as a fool ? " When you answer this, we shall know- what use the world can make of you." DAVID STARR JORDAN. 208 PRIMER OF PHYSIOLOGY QUESTIONS Tell of the discovery of tobacco and its introduction into Europe. What different opinions were at first held about to- bacco? Name some drugs that are commonly used for their pleasant effects. What effect has a stimulant? a narcotic? Is nicotin a stimulant or a narcotic ? At what time of life is tobacco especially injurious? De- scribe the experiment in which young guinea pigs were made to inhale tobacco smoke. Why do most of our states prohibit the sale of cigarettes to young persons ? Give the results of Professor Seaver's observations on students in Yale University. What effect has tobacco on the muscles? Describe the experiment performed by Professor Lombard. For what pur- pose was tobacco used by physicians before chloroform was known? Why are athletes in training not allowed to use tobacco? What effect has tobacco on the nervous system? Why are users of tobacco not good marksmen ? Repeat what Luther Burbank said about his workmen. Give statistics showing mental progress made in schools by smokers and by non- smokers. What rule have many great employers made regard- ing cigarette smokers? How does tobacco affect the mind? the digestive system? the arteries? Discuss the effect upon the body of a moderate use of tobacco. SUGGESTIONS TO THE TEACHER If possible, teach this chapter in an informal manner, discussing local conditions when it is possible to do so. Statistics as to the use of tobacco by the athletes and high scholarship students of the school may quickly be gathered, and the attitude of local employers may sometimes be mentioned. The continued use of cigarettes by the young can only be ascribed to ignorance concerning the results of their use, and the question will form an excellent subject for dis- cussion at a parents' meeting. The Scientific Temperance Journal, TOBACCO 209 Boston, Massachusetts, prints much information on this subject that is of value to the teacher. The price of this journal is 60 cents a year. Emphasize again the importance of forming correct habits and how tobacco interferes with the formation of habits of industry. In case a good student has recently begun the use of tobacco, call his attention to the fact that his previously formed habits of study are still keeping his class standing high, but that he should be on the alert for signs of the drop in his scholarship record that will in all probability come if the use of tobacco is continued. An interesting side topic is the early history of the use of tobacco in Europe. The securing of the concessions for its sale by Sir Walter Raleigh and his efforts to extend its use so that his revenues from it might be increased, have much of human interest in them. CHAPTER TWENTY-ONE ALCOHOL A STANDARD text on hygiene that was used in many of our medical colleges as late as 1890 taught that malaria was due to miasma from swamps ; that typhoid fever was connected with the rise and fall of ground water; that cholera seemed to be related to the tem- perature of the soil from four to six feet below the surface ; that erysipelas was due to impurities in the iir ; that diphtheria was caused by sewer gas ; and that yellow fever was an air-borne disease. These ideas seem strange to us today, but the fact that they were current so recently even among medical men emphasizes the fact that in the past men have looked upon disease as something that comes upon us from without ; that they have thought of the causes of sickness as lying in the world about us. Now we have come to understand that the causes of ill health are to be sought for, not in the swamps and forests and changes of weather, but within the body itself ; that it is what goes into the body rather than the distant outside world that is important in hygiene. We have learned that the great secret of health is to keep the lymph in which the cells are bathed free from poisons and impurities and to allow the cells to live their own lives in a natural way. Along with this new knowledge there has come a truer understanding of the uses of medicines and a greater care about taking into the lymph strong drugs whose effects on the delicate cells are not fully under- stood. The best physicians now realize that all medi- cines are foreign and unnatural substances in the lymph, which ought to be given only when there is good reason 210 ALCOHOL 211 to believe that the body will be benefited by them; and they are continually amazed at the reckless and ignorant way people pour patent medicines and other strong drugs in upon their cells. In this chapter we shall study the effects on the body of the use of alcohol, a powerful drug that is extensively used by the people of our country. Where alcohol comes from. Yeast is a small plant that lives on the skins of fruits and in very rich earth, and that often blows about in the air. The favorite food of this small plant is sugar, and when it falls into a liquid that contains sugar, it grows and multiplies very rapidly. In doing this it uses the sugar for food and breaks it up into water, carbon dioxid, and alcohol. This process is called fermentation. The alcohol in all the different kinds of intoxicating drinks that are used by man comes from the fermentation of sugar by yeast. Different kinds of alcoholic drinks. The natives of the tropics cut off the flower clusters of palm trees and col- lect the juice that pours out from the cut ends. This contains much sugar, and after it has been fermented it contains great quantities of alcohol. The Mexicans collect the juice of the agave, or century plant, in the same way and manufacture an intoxicating drink from it. % Fruit juices are rich in sugar, and in temperate countries the people make wine by allowing them to ferment. Grapes, apples, currants, and blackberries are the fruits that are most commonly used for this purpose. In the manufacture of beer, grain is soaked in water until it sprouts, and the starch in it is digested to sugar and dissolved out in water. Yeast is then allowed to change the sugar in the liquid to alcohol. 212 PRIMER OF PHYSIOLOGY Rum is made by fermenting molasses and distilling off the alcohol; whisky is made by distilling the fer- mented liquid from sprouting grains ; and brandy is made by distilling fermented fruit juice. 1 Alcoholic drinks have different tastes, according to the substances from which they are made, and some are stronger than others, but in all of them it is the alcohol itself that is the important thing. The use of alcohol injurious to the body. Is alcohol injurious to the body ? In the past there has been a division of opinion on this point. Today we have come into an age of science, and we are substituting knowledge for guesswork in all fields of human thought. What are the facts in this case ? Does taking alcohol among the cells cause the body machine to run a longer or a shorter time, and is it laid up for repairs more days or fewer days in a year when alcohol is used ? The following statistics will give us some information on the question. The effect of alcohol on health and length of life. In Australia the workmen have benefit societies that pay wages for time lost on account of sickness. The records of these societies show that the members of societies that admit only abstainers lose but little over half as much time on account of illness as do the members of societies that admit drinkers. This indicates that the use of alcohol increases sickness. A number of life in- 1 In distilling liquors, the liquid (the fruit juice or the water in which the grain has been soaked) that contains the fermented sugar is heated, and the vapor that comes from it is caught and condensed. The alcohol in the liquid is changed to vapor more easily than water, and the liquors that are manufactured in this way are strong in alcohol. ALCOHOL 213 surance companies have kept records of the deaths of the abstainers and drinkers among their policy holders separately. When these records are examined, the results are always the same, the death rate among the drinkers is higher than it is among the abstainers. The following examples taken from recent reports of insur- ance companies will illustrate the point. In the ten-year period from September 30, 1900, to September 30, 1910, the experience of the Australasian Temperance and General Life Insurance Society showed that where there were 100 deaths among drinkers there were only 62 deaths among abstainers. The Manu- facturers' Life Insurance Company during the nine-year period from 1902 to 1910 inclusive had a death rate of 56 among abstainers as against 100 deaths among an equal number of drinkers. For a twenty-eight-year period, ending in 1911, the Sceptre Life Insurance Association had 67 deaths among its non-drinking policy holders, where it had 100 deaths among its non-abstain- ing members. All other records that have been kept show that there are more deaths among drinkers than among an equal number of abstainers of the same age. 1 1 "There may be some actuary in the world who believes that total abstainers do not live as long as non-abstainers, but I never heard of one, and I have never seen any figures showing an advantage in favor of abstainers of less than 21 per cent. Certainly, adding one fifth to a man's life makes it worth while to forego one class of food or drink. " Some years ago I secured an opinion of an actuary on the expectation of life of a young man of twenty who was a total abstainer and of one who was a drinking man at that age. The expectation of the abstainer was 42.2 years; of the drinking man, 15 years." EDWARD A. WOODS, an insurance manager, quoted in Dr. Henry Smith Williams' Alcohol: How it affects the Individual, the Community, and the Race. 214 PRIMER OF PHYSIOLOGY We can therefore decide that alcohol used as men ordi- narily use it causes sickness and shortens life ; and since this is true, it must also be true that it is injurious to the cells. The effects of alcohol on the structure of the cells. Alcohol causes fatty degeneration and fibroid degenera- tion of certain of the tissues. 1 In fatty degeneration little droplets of oil begin to collect within the cell, and gradually the living protoplasm of the cell is replaced by fat, until sometimes the cells become mere bags of oil. When the cells of the gastric glands are changed in this way, they lose their power to secrete ; when the muscle cells of the heart are changed to fat, they lose their strength ; when the walls of the arteries are affected, they are, of course, weakened ; and when there is fatty degeneration of the liver, kidneys, or nerve fibers, we must expect these organs to fail in their work. The tissues most commonly affected by fibroid degen- eration are those of the liver, kidneys, arteries, heart, and brain. In this kind of degeneration there is an overgrowth of the connective tissue elements, while the working cells degenerate and die. * Often in the arteries the elastic muscle coat is not only changed to connective tissue, but lime is deposited in the walls. These changes make " pipe-stem " arteries, which are brittle and often have the opening in them narrowed until it is with great difficulty that the blood makes its way through them. 1 As we have already explained (page 155), there is good reason to believe that in some of these changes in the tissues it is intestinal toxins rather than the alcohol that really causes the trouble, but since it is the drinking of the alcohol that causes the toxins to be formed, the fault in the end goes back to the alcohol. ALCOHOL 21$ Some diseases that may be caused by alcohol. In the United States each year there are about 4,000 deaths that are directly due to the use of alcohol. Certain diseases, moreover, are more common among drinkers than among abstainers, and it is believed that much sick- ness and many deaths are due to accidents and diseases that are brought on by the use of alcoholic drinks. Prominent among the causes of death that are con- nected with the use of alcohol are : hardening of the liver, in which the liver turns to connective tissue and shrinks into a small, hard organ utterly incapable of doing the work which it is supposed to do ; diseases of the kidneys, in which these organs degenerate and fail in their work of excreting the poisonous wastes ; heart disease, which may take many forms ; hardening of the arteries ; apoplexy and paralysis, which are due to the bursting of blood vessels in the brain ; insanity and other diseases of the nervous system ; tuberculosis, pneu- monia, and other germ diseases, to which the user of alcohol falls a victim because he has weakened the defenses of his body ; and accidents that would never have occurred had not some one been under the influ- ence of drink. It will be noticed that the chief effects of alcohol, aside from those on the nervous system, are on the heart, blood vessels, lungs, stomach, liver, and kidneys, the great internal organs that supply the body with food and oxygen and dispose of its wastes. When we re- member how the life of the whole body requires that the work of these organs be efficiently performed, it is easy for us to understand that anything that injures them is of first importance in the realm of health. 2l6 PRIMER OF PHYSIOLOGY The effects of a continued moderate use of alcohol It should be understood that, except for certain effects on the brain, we are discussing in this chapter the effects of what is called moderate drinking on the body ; for when alcohol is used day after day, even though it be used very moderately, there is a piling up of its effects on the tissues. Indeed, the cells of the man who drinks a moderate amount of beer or wine daily are never free from the influence of alcohol. Beer drinkers suffer most of all from fatty degeneration of the tissues, and one need never become intoxicated to experience the evil effects from alcohol that have been described above. 1 The shortening of life given on page 2 1 3 is in moderate drinkers and not in drunkards ; for the death-rate among those who habitually drink to intoxication is so high that no insurance company will accept them. 2 The effects of alcohol on the mind. Because alcohol causes a person to seem lively and to talk more easily, it is commonly believed that it is a stimulant. This is a mistake. Alcohol is a narcotic, and it produces its seemingly stimulating effect by paralyzing the higher 1 " Alcoholic diseases are certainly not limited to persons recognized as drunkards. Instances have been recorded in increasing numbers in iccent' years of the occurrences of diseases of the circulatory, renal, and nervous systems, reasonably or positively attributable to the use of alco- holic liquors in persons who never became really intoxicated and were regarded by themselves and others as ' moderate drinkers.' " DR. WILLIAM WELCH. 2 A few of those classed as drinkers may have become heavy drinkers after they were insured, but insurance companies reject not only drunkards, but also those who seem likely to become drunkards. The comparison is, therefore, in the main between abstainers and moderate drinkers. ALCOHOL 217 centers of the brain and allowing the person to do and say things that, ordinarily his good sense keeps him from doing and saying. In one set of experiments it was found that 20 to 40 grams of alcohol (the amount in from one to two quarts of beer) taken on twelve suc- cessive days lessened the capacity to add numbers 40 per cent and the ability to memorize poetry 70 per cent. Other experiments show that the capacity to think clearly and to judge correctly is greatly influenced by even small quantities of alcohol. Typesetters who were given only a little over an ounce of alcohol a day did 10 per cent less work and made 25 per cent more mis- takes than on days when no alcohol was taken, and the effect of these small doses of alcohol continued 48 hours. After taking a drink, a man feels that his mind is working better and that his ideas come more easily and freely. The truth is that his mind is slower and his ideas are less sensible than usual, but the powers of his mind by which he judges of these things have been deadened by the alcohol, and he is no longer capable of forming a correct opinion of his own acts. The effect of alcohol on the strength and control of the muscles. The man who has taken alcohol always feels that he is stronger and has more endurance because of it. In this case, again, the alcohol user is mistaken as to his real condition, as facts like the following prove : About sixteen years ago, Professor Durig, a chemist and an expert mountain climber, carried on a series of experiments by repeatedly climbing a peak in the Alps. On certain days he drank alcohol equal to the amount in two glasses of beer ; on other days no al- cohol was taken. He was accustomed to use moderate 2l8 PRIMER OF PHYSIOLOGY amounts of alcohol, and he felt that he worked more easily on alcohol days, but to his surprise he found that on those days he expended 15 per cent more energy and required more than one fifth longer to climb the mountain. Other tests carried on for ten days in the laboratory showed that two glasses of beer taken at dinner reduced the working power of the muscles 10 per cent. " Alcohol gives, not strength, but only a feeling of strength, to the muscles." It deadens the ability to feel fatigue, but does not relieve fatigue. It is probable that the weakening effect of alcohol on the muscles is mainly due to its interference with their control by the nervous system. The movements are made awkwardly, and the muscles work against each other, and so much of their power is lost. This lack of fineness of control in alcohol users is shown at once in a baseball pitcher, a bowler, a rifleman, or any one who does work that requires each muscle to work exactly the right amount and at exactly the right moment. Why alcoholic drinks have been banished from the United States. When the Great War came and nations were put to the test, practically all those that were called on to put forth all their effort restricted the manufacture and sale of alcoholic drinks. No argu- ment was needed to convince the peoples that the manu- facture of intoxicating drinks was a waste of foodstuffs and their use a hindrance in the prosecution of the war ; deep within their consciousness they knew that alcohol was an evil. They were shaking off everything that would hinder them in the great fight and they knew that the use of intoxicating drinks would sap the ALCOHOL 219 strength and becloud the minds of those who needed clear intellects and strong bodies for the struggle. Now that the war is over the people of our own country have decided that intoxicating drinks shall be sold in it no more. Some of the reasons that moved them to this decision have been set forth in this chapter. The majority of them were convinced that alcohol is injurious to health, morals, and efficiency, and they saw no reason why in times of peace any more than in times of war an unnecessary burden should be imposed on our land. After seventy-five years of discussion of the question our people, through their representatives, have declared that the time when intoxicating drinks can be sold in the United States has passed. This de- cision is doubtless wise; the combined judgment of an intelligent people on any question with which they have long been familiar is usually correct. Once again America has led the way, and in time the other great nations of the earth will doubtless follow the example she has set. QUESTIONS How is alcohol produced ? How is alcohol made in the tropics ? How is wine made ? How is beer made ? Name some distilled liquors. What effect has the use of alcohol on the-health ? Give statistics showing its effect on the death-rate. Explain what is meant by fatty degeneration. What organs may be affected in this way ? What changes take place in fibroid degeneration ? What organs are commonly affected in this way ? Explain the result of fibroid degeneration of the arteries. In the United States how many deaths each year are due to 220 PRIMER OF PHYSIOLOGY alcohol ? How many are directly caused by alcohol ? Name some diseases that are often caused by the use of alcohol. What organs of the body are most affected by the use of alcohol ? What effects has moderate drinking on the body ? Why is it commonly believed that alcohol stimulates the mind ? What effect have small amounts of alcohol on the power to add numbers ? to memorize ? Describe the experi- ment in which typesetters were given small amounts of alcohol. Explain the effects of alcohol on the muscles. SUGGESTIONS TO THE TEACHER In teaching this chapter, nothing is so important as to get the facts before the pupils. The two most easily accessible sources of facts in regard to the effects of alcohol are Dr. Henry Smith Williams' Alcohol: How it Affects the Individual, the Community, and the Race (The Century Company, New York) and the numbers of the Scientific Temperance Journal (see page 208). This journal gives, through summaries and abstracts, the results of scientific ex- periments in this field and translates articles dealing with the very important work that is now being carried on in different European countries CHAPTER TWENTY-TWO ACCIDENTS " IN time of peace prepare for war." In every house there should be kept in a small box or drawer certain articles for use in case of accident. Among these arti- cles should be soft, worn-out towels ; cotton or linen cloths three to six inches square; rolls of bandages varying from one half inch to three inches in width and from one to two yards in length ; a bar of green soap ; threaded needles, scis- sors, and safety pins ; borated vaselin ; bichlorid or biniodid of mercury disks ; powdered boracic acid ; and a bottle of collodion. Accidents come without warning, and having these supplies ready may save suffering or even life. Bandages. Since many small hurts are treated with- out the aid of a physician, it is well to understand how to put on a bandage neatly, comfortably, and securely. When the part that is to be bandaged is of nearly the same circumference throughout, the bandage should simply be rolled around the part from below upward, each turn of the cloth covering two thirds of the one below. When the part that is to be.bandaged is thicker in one part than in another, as the forearm or leg, the bandage may be made to lie smooth and flat by revers- ing each turn after the first few turns. To reverse a bandage, hold it at its lower edge and turn it one half 221 FlGS. 138 and 139. Showing a circular bandage and the method of reversing a bandage. 222 PRIMER OF PHYSIOLOGY over towards you. To give a neat appearance, make each reverse directly above the one preceding it. The figure-of-eight bandage is useful about joints. The best way to get an understanding of the dif- ferent bandages here described is to study the illustrations in Fig- ures 138 to 143. After two turns have been put on, the bandage should be firmly stitched, and, after the bandage is completed, the end should be securely sewed. A row of stitches from top to bottom, one in each turn of the bandage, is of great advantage in preventing slipping. Always bandage firmly, but never too tightly, and use an equal pressure throughout the bandage. Wounds. It is well that a cut should bleed freely, as the blood assists in washing out and killing any germs that may be in the wound. If the cut has been made with a clean instrument, it may be FIGS. '140, 141, 142, and 143. bandaged without any treatment A reversed bandage and a t n bandaged after being figure-of-eight bandage on tlje hand; a figure-of-eight band- dusted with powdered boracic age and a reversed bandage ^ A wound made by an on the foot. J unclean instrument should be washed with soap and water and treated with powdered boracic acid or borated vaselin. If the person must use ACCIDENTS 223 the injured part in attending to his work, two bandages should be put on. The outer one may be changed when it is soiled, but unless the wound becomes red and pain- ful and has matter in it, the inner bandage should be left undisturbed until the injury has healed. Deep wounds, such as are made by rusty nails that have become soiled by lying about barnyards, are dan- gerous, because frequently tetanus germs get into them. A puncture or other wound that is so deep that it can- not be thoroughly cleansed ought to be treated by a physician, who will know whether it is advisable to use tetanus antitoxin as a safeguard against danger from tetanus germs. Bleeding. When blood flows in jets and has a bright red color, an artery has been cut. If the blood flows in a steady stream, it is a vein that has been severed. In either case, a physician should be called at once. In the mean- time, control the bleeding by pressing on the vessel with the thumbs. The pressure should be applied between the wound and the heart if the cut vessel is an artery ; beyond the wound, if the bleeding is from a vein. If the physician is long in coming, or if the bleeding can- not be controlled by pressure with the thumbs, twist a handkerchief about the limb, as shown in Figure 144. The blood should not be shut off from the limb for longer than an hour, as much damage may be done by FIG. 144. Checking bleeding from a wound. 224 PRIMER OF PHYSIOLOGY depriving the cells of their supply of blood for too long a time. Blows on the head. A blow on the head sometimes ruptures a blood vessel within the cranium and causes a blood clot to form on the brain. If, a person becomes sleepy after such a blow, a physician should be called at once. It is well to wake the person occasionally during the night after such an injury; for otherwise he may sink into unconsciousness without its being discovered. Burning clothing. If your clothing should take fire, do not start to run. If possible, remove the burning garment at once. If this cannot be done, remember that a fire cannot burn without air, and that the quickest way to put out burning clothing is to lie down and wrap your- self in a blanket or rug, or in anything else that you can lay hands on. If nothing is at hand that can be used as a covering to smother the fire, lie down and roll over and over. In any case, lie down so that the flames will not come up about your face ; for inhaling a flame is often followed by very serious consequences. In passing close to a fire, as in a burning building, the face should be pro- tected if possible by something held before it. The treatment of burns. A burn in which the skin is only reddened, or in which the blistering is slight, may be treated by simply shutting the air away from it. A paste made of baking soda and water, or of flour or starch mixed with water, is good for this purpose. White of egg, vaselin, olive oil, castor oil, fresh lard, or cream may also be used to cover a burn. Wet cloths wrung out of cold water will help to allay the pain. Burns which cover much surface, or small, deep burns, should be shown to a physician; for it is not always ACCIDENTS 22$ possible to tell at first how much damage has been done, and the injury may be more severe than it appears to be. A burn made by an acid should be washed and treated with limewater, baking soda, or soapsuds. A burn made by an alkali (such as lime, lye, etc.) may be treated, after thoroughly washing off the alkali, with weak vinegar, lemon juice, sour milk, or buttermilk. Apparent drowning. Drain the water from the pa- tient's lungs by catching him under the waist and hold- ing him for a few seconds with the head hanging down. Then quickly lay him in the position shown in Figure 145, with a folded coat or blanket under his chest. Place the hands on either Side Of the back FlG " I4S ' Carrying on artificial respiration. over the lower ribs. Throw the weight of the body steadily downward on the hands and drive the air out of the lungs. Take the pressure off the body without lifting the hands, and allow the air to come into the lungs. Repeat about fifteen times a minute. This method sends more air through the lungs than any of the methods in which the patient is laid on his back, and it has the additional advantage that the tongue does not fall back and block the throat. Rubbing the limbs along the veins toward the heart causes the blood to circulate and should be kept up if there is a second person to attend to it. Keep the 226 PRIMER OF PHYSIOLOGY patient as warm as possible by covering him with a blanket and pouring warm water over him, or by laying hot-water bottles about him. A hot-water bottle at the head is especially important, but nothing hotter than can be borne comfortably by the skin of the elbow should be brought into contact with an unconscious per- son. When the patient begins to revive, give strong hot coffee, or fifteen drops of ammonia in a glass of water. Artificial respiration should be kept up for an hour or longer if the person does not recover sooner. Suffocation. Suffocation may be produced by hanging, by choking, or by gas or smoke poisoning. Sprinkle cold water on the face; carry on artificial respiration as in cases of apparent drowning ; and, when the person is able to swallow, give stimulants as directed above. Fainting. Lay the patient flat on his back, so that the blood will flow easily to the head. Sprinkle cold water on the face, and give him fresh air. Give strong coffee or ammonia as directed above. Dangers from electricity. As the use of electricity becomes more common, it is more and more frequently a source of accidents. Even now many people do not seem to know that highly charged electric wires and third rails are deadly affairs, and that those who do not understand their workings ought not to take chances with, them. Where a notice is posted warning the public not to cross the track of an electric line, there is a reason for the warning, and you should keep off the track. When a trolley wire or an electric wire breaks and faMs to the ground, keep away from it. It is in- teresting to experiment with electricity, but you cannot afford to begin in this way. ACCIDENTS 227 Rescuing a person from an electric wire or a third rail. A live wire lying on a person may be safely flipped off with a dry board or stick. If the person is lying on the wire, the wire may safely be cut with an ax or hatchet that has a dry wooden handle. Cut between the person and the source of the electricity ; on both sides, if the source of the electricity is unknown. In trying to pull a person off a live wire or third rail, great care is necessary or the rescuer will be injured. In attempting to do this, unless the ground is very dry, one should stand on a dry board, a folded coat, or several thicknesses of folded newspapers. A rubber mat is better than the articles just mentioned, but it is not often at hand. If possible, take hold of the per- son through dry cloth or paper, and catch him by the clothing without allowing the hand to come into contact with his body. Pull him off the rail or wire with one quick, firm motion, and if he is not breathing, carry on artificial respiration as in cases of apparent drowning. A doctor should be sent for as quickly as possible. Foreign bodies in the eye. If a cinder or other foreign body gets into the eye, do not rub the eye. Keep it closed and the tears will often wash the dirt out into view so that it may easily be removed. Sometimes stretching the upper lid down over the lower lid two or three times, or closing the nostril on the opposite side and blowing the nose hard, will change the position of the object and make it possible to remove it. The inner surface of the lower lid may be examined by pressing the lid down, and some persons are skillful enough to turn the upper lid back over a match or small stick so that the offending particle can be wiped off. Only 228 PRIMER OF PHYSIOLOGY clean fingers, clean handkerchiefs, or other clean objects should be allowed to touch the eye. After the foreign body has been removed, a few drops of boracic acid solution is soothing and is useful in safeguarding against possible infection with germs. Foreign bodies in the nose and throat. Little children sometimes push beans, peas, beads, or other objects into their noses. Having the child blow the nose will often bring these objects out, but if they cannot be removed in this way a physician should be called. Do not try to remove them with a hairpin or other sharp instru- ment. When a button, coin, or other object sticks in the throat, the child should be seized by the feet, suspended head downward, and energetically shaken and slapped on the back. Usually this will cause the object in the throat to drop out. Treatment for swallowed pins and needles. When a pin or needle has been swallowed, a large meal of bread, potatoes, cabbage, or other coarse foods shpuld be eaten, as they will leave a large amount of undigested matter to coat the foreign object during its passage through the alimentary canal. Never give a laxative under suck conditions. No anxiety need be felt over swallowed but- tons, coins, and other similar objects. Frostbite. Keep away from the fire and thaw the "bitten" part out very gradually by rubbing it with snow, or by keeping it bathed in ice water until the blood begins to circulate through it again. Suddenly thawing the frozen tissues is far more injurious than the freezing, and every care should be taken to keep in a cool atmosphere until the thawing process is completed. ACCIDENTS 229 Ivy poisoning. Dissolve a level teaspoonful of potas- sium permanganate crystals in a pint of water and bathe the affected parts. Before the skin is broken FIGS. 146 and 147. The poison ivy is often mistaken for the Virginia creeper. The Virginia creeper has five leaves, while the poison ivy has only three. the poisgnous oil may be partially removed at least by thorough washing with strong soap or with alcohol. In severe cases a physician should be consulted. Poisoning. Bottles that contain poisons should not be kept among medicines, and it is well to paste strips of sandpaper on such bottles, so that they can be recog- nized even in the dark. When a poison is taken by accident, a physician should be called immediately. If possible, have the messenger tell him what poison has been taken, so that the proper antidote may be brought. A card with a list of the different poisons and their antidotes should be written out, and placed with the other articles that are kept for use in case of accident. The sooner the antidote is given, the less time will the poison have to damage the body, and when one is thus prepared, a case of poisoning can often be treated be- fore the doctor arrives. 230 PRIMER OF PHYSIOLOGY While waiting for the doctor, give an emetic at once to produce profuse vomiting, if the poison is not an acid. Good emetics are : mustard and water ; salt and water ; lukewarm water alone and in large quantities ; and ipecac. Tickling the throat with a feather or thrust- ing the finger into the throat will help to cause vomiting. The following list of antidotes for some of the more common poisons may be found useful : Acids. Give soda, chalk, old mortar, or soap. Oil and milk are useful. For carbolic acid use alcohol (whisky or brandy will do). Oil or milk should be used if no alcohol is at hand. Arsenic. This is the poison in Fowler's Solution, Paris Green, and Rough on Rats. Give any medicine that contains iron. Mercuric chlorid. This is also called bichlorid of mercury and corrosive sublimate. Give milk, white of egg, or both. Flour or starch with milk and egg is good. Phosphorus. Magnesia and chalk in water, and white of egg are good remedies. Do not give oil or milk. Phosphorus is the poisonous substance on the end of matches, and is often found in rat poison. Opium, laudanum, nightshade, and jimson weed. Give strong coffee or ammonia. Keep the patient awake by walking him about, slapping him, or throwing cold water over him, if necessary. Give stimulants as di- rected under Fainting, on page 226. Strychnin. Inhaling chloroform or ether will quiet the patient. Give five grains of sodium bromid every half hour. Keep the patient away from cold drafts and noises, and allow nothing to touch him, as any stimulus makes the spasms more violent. ACCIDENTS 231 Preventing accidents. The first step in preventing accidents is so to arrange the conditions under which we live and work that it will be difficult for mishaps to occur. In machine shops and factories and on railroads, this is rapidly being done. The causes of accidents in private homes and on farms should also be removed ; for many houses are built with dangerously steep cellar stairs ; many barn lofts can be entered only by climbing rickety ladders; stairways and openings in floors that are left unprotected by railings are the cause of many falls ; and farm machinery is constantly being operated in a dangerous and careless way. All these and other conditions that cause accidents should be remedied, and when this is done the number of accidents is at once greatly reduced. The other important factor in the prevention of acci- dents is the use of intelligence and reasonable care when it is possible for carelessness to cause an accident to happen. In our cities children are continually run- ning directly in the way of automobiles and street cars ; drownings occur because of a lack of care in handling boats and because persons who cannot swim venture into water beyond their depth ; clothing is set ablate by standing too near an open fire ; and automobile acci- dents occur because of recklessness in driving these machines. Accidents of this kind can only be pre- vented by intelligence and watchfulness, and you should constantly educate yourself in those habits that prevent them. More people are injured by falling than in any other way, and the most common cause of falls is carelessly placed ladders. An ordinary ladder should not be set 232 PRIMER OF PHYSIOLOGY too straight or too slanting, and a three-legged stepladder stands more securely than a four-legged one. The problem of accidents is more important than is generally understood (Fig. 148), as in addition to the killed, hundreds of thousands of persons are injured in them each year. QUESTIONS Name some articles that should be kept for use in case of accident. Name three kinds of bandages and tell how each is put on. Describe the treatment for cuts. Why is a deep wound made by an unclean instrument dangerous ? When blood is flowing from a wound, how can you tell whether it comes from a vein or an artery ? How can the bleeding be checked until a physician arrives? Why should a person not be allowed to sleep uninterruptedly after a blow on the head ? If your clothing were to catch fire, what should you do ? Describe the treatment of burns. De- scribe artificial respiration. When should it be used ? In addition to carrying on artificial respiration, what else may be done in cases of apparent drowning? What should be done in cases of suffocation ? What should be done for a person who has fainted ? Tell how a person may be rescued from a live wire or a third rail. How may foreign bodies be removed from the eye ? from the nose ? from the throat ? What is the treatment for swallowed pins and needles ? for frostbite ? for ivy poisoning ? Give antidotes for the following poisons : carbolic acid ; arsenic ; mercuric chlorid ; phosphorus. Give the treatment for a case of strychnin poison. In what two ways can accidents be prevented. CHAPTER TWENTY-THREE REALIZING HEALTH POSSIBILITIES WHEN a farmer begins to study how to increase his harvests, one of the first facts he learns is that it is the -'limiting factor" that determines what the growth of his crops shall be. An exact definition of what a limit- ing factor is would mean little either to the average farmer or to you, but an illustration makes it easy to understand the meaning of the phrase. Suppose that in an acre of land there is enough nitro- gen to raise 75 bushels of corn, enough phosphorus to raise 20 bushels, enough potassium and other needed elements to raise 100 bushels, and that the season is favorable and there are rain and sunshine enough to make 100 bushels. What will the crop be? It will be 20 bushels. The phosphorus is the limiting factor that makes it impossible for the yield to rise above that point. A chain is no stronger than its weakest link, and it is not the half dozen favorable factors, but the one unfavor- able one, that determines what the harvest shall be. The important thing for the farmer to do, therefore, is to find the factor that is limiting his crop and strengthen the weak point. Otherwise the abundant supply of water and of nitrogen and other plant foods in the soil is of no value to him. The limiting factor in health. The health of the hu- man body is dependent on many different things. All of these are necessary, and if any one of them is lacking, it will be the limiting factor that will make health im- possible no matter how many other conditions may be favorable. One person may have good food, fresh air, 233 OTHER CONSTITU TIONAL DISEASES 25,334 CANCER ,41,039 DISEASES OF STOMACH PYOGENIC FECTIONS 26,959 ENINGITIS 7.169 OTHER GERM ISEASES 54,527 ENTERITIS (DIARRHEA) 63,160 DISEASES OF OTHER DIGESTIVE 8,122 10.029 ORGANS MEASLES 6,596 SCARLET FEVER 6.255 DISEASES OF NERVOUS SYSTEM 15,365 DISEASES OF ARTERIES 11,657 APOPLEXY 39.701 BRIGHTS DISEASE 47.665 DYSENTERY 3.446 TYPHOID FEVER 12,673 TUBERCULOSIS 66309 HEART DISEASE 60,047 ALCOHOLISM OLD AGE 2 ' 909 13,604 CHRONIC POISONINGS PNEUMONIA 79,524 INFLUENZA 7J74 BRONCHITIS 12.620 DEATHS DURING EARLY INFANCY 47,386 SUICIDE HOMICIDE 6.590 3,190 FIG. 148. Causes of deaths in 1910 estimated from Census reports. Exact figures cannot always be given. Pyogenic infections are blood-poisonings and other inflammations. This estimate covers 58.35 per cent of the population in sections where the best conditions prevail and proper death records are kept. The rate is higher for the rest of the country. Estimates give 1,450,000 deaths in the U.S.A. yearly, 600,000 of which are considered preventable. REALIZING HEALTH POSSIBILITIES 235 and everything else necessary to health except sufficient sleep. In other cases the limiting factor may be the condition of the teeth, adenoids, lack of exercise, lack of fresh air, alcohol, overwork, or improper food. With many persons everything necessary for health is present if only disease germs could be kept out of the body. In some cases more than one difficulty must, of course, be removed before health can be achieved, but often only one factor makes the difference between illness and health. In our quest for health, it is, therefore, most important that we neglect none of the factors that are necessary for a realization of our health pos- sibilities. To give you some wider ideas that may serve as guiding principles in your search for limiting hygienic factors in your own life, we shall in this final chapter discuss in a more general way the causes of sickness and how they may be avoided. Two classes of diseases. Diseases may be divided into two great classes, germ diseases and what may be called physiological diseases. In those of the first class, the difficulty is that germs are growing in the body and poisoning the cells. In diseases of the second class, the trouble is in the body itself. Some organ like the heart or the liver fails in its work and. the body is like an engine with a broken part. Germ diseases are in the main diseases of early and middle life, while physiological diseases usually come on only in later life when the organs and tissues begin to wear out. Figure 148 will give you an idea of some of the more important of the diseases belonging to each of these classes. The cause of germ diseases. Disease germs are 236 PRIMER OF PHYSIOLOGY either bacteria, which are very small plants, or they are little animals that live in the body. Like other living things, germs must have food, and they grow in the body because in it they can find the food supply and the warmth that they need. Unfortunately for both them and us, however, disease germs produce toxins in their bodies that poison our cells. These toxins throw out of order all the life processes of the cells, and in some diseases like diphtheria and scarlet fever the cells in vital organs like the kidneys and the heart may in a very few days become soft and. mucilage-like, and many of them may undergo fatty degeneration (page 214). From the diagram on page 233 you will see that germ diseases are responsible for practically one half of all the deaths in the United States, and they do even more damage than this indicates ; for an attack of diphtheria at ten years of age may weaken the heart until it will fail when the person reaches fifty years of age, scarlet fever in childhood may start trouble in the kidneys that will lead to Bright's disease in later life, and it is a com- mon thing for typhoid fever to wreck the health for all time. Insurance companies that have tried issuing policies on the lives of reformed drunkards have found the death rates exceedingly heavy. Even when the drinking is stopped, the effects of the alcohol that has been consumed in years past cannot be removed. So even though a person is not killed outright by an attack of germ disease, it is nevertheless true that his cells are often damaged by the toxins until they never re- cover. Germ diseases, therefore, are of far more impor- tance than the mere number of deaths caused by them shows. REALIZING HEALTH POSSIBILITIES 237 How the body resists disease germs. For our resist- ance to many germs, we depend on the white corpuscles of the blood, which swallow the germs and destroy them. At times the corpuscles are very active ; at others they seem to lose all interest in germs and lie inactive when the germs are growing all about them. It has been found that this difference in the activity of the cor- puscles depends on whether or not there are opsonins in the blood. What these are or where they come from is not known exactly, but in some way they seem to make the germs more appetizing to the corpuscles and cause the corpuscles to take them in. There is a differ- ent opsonin for each different kind of germ, so that one may have plenty of opsonin for the tuberculosis germ, and little opsonin for the pneumonia or the grip germ. In other diseases the germs are killed in the body by a germicidal substance which is formed in the cells and appears in the lymph and the plasma of the blood. This dissolves and kills the germs, and is even more important as a defender of the body than are the white corpuscles. As in the case of the opsonins, there is a different germicidal substance for each different kind of germ that is killed in this way. After certain diseases the germicida*! substances remain in the blood for years or even for life, and we usually suffer from these diseases only once. The relation of good health to disease germs. The power to resist germs depends on having in the blood opsonins and germicidal substances for the germs. These are naturally present in the blood of the average person only in very small amounts, and merely being in good health does not seem to increase these amounts. 238 PRIMER OF PHYSIOLOGY If, however, germs are introduced into the body, the presence of the germs causes the body to begin the manu- facture of opsonins and germicidal substances to com- bat them. The way to secure immunity to a disease, therefore, is to have the disease, or to introduce into the body weak or dead germs of the kind that causes it. This is what is done in vaccination for smallpox, typhoid fever, plague, boils, catarrh, and a number of other diseases. We cannot secure this immunity through good health alone, as is proved by the fact that diseases like measles, typhoid fever, cholera, plague, smallpox, and diphtheria attack the strong as readily as they do the weak. 1 It must not be concluded from the above, however, that care of the body is of no importance in dealing with germ diseases. It is true that we cannot depend on good health to keep us from taking these diseases, but after we have them the body has the task of manu- facturing enough opsonins and germicidal substances to kill the germs. It is. reasonable to suppose that a vigorous, healthy body can do this more rapidly than can a feeble body, 1 There is a widespread notion, even araong physicians, that if one will keep himself in good condition he will be able to " throw off " any dangerous germs that may get into his body. Unfortunately, this theory does nqt seem to be in accordance with the facts. Studies made on the soldiers who contracted typhoid fever in the camp at Chickamauga during the Spanish-American war showed that these men were no weaker than those who escaped the disease, nor were they sick or out of condition before the fever came upon them. Laboratory tests show that only about one fourth of the rats of San Francisco are susceptible to plague. There is no reason to believe that the animals that take the disease differ in any way from those that escape it, except in their lack of the germicidal sub- stance which kills the plague germ. REALIZING HEALTH POSSIBILITIES 239 and even though a strong body does not protect us from acute infections, it ought to withstand the strains of illness better than a body that has been weakened through lack of care. Moreover, in slow diseases like tuberculosis, catarrh, bronchitis, chronic colds, ma- laria, and chronic infections of many kinds, the body has plenty of time to manufacture its protecting sub- stances, and a vigorous condition of the health is of the highest importance in helping us combat ailments of this kind. Nevertheless, it remains true that the way to avoid germ diseases is to keep the germs out of the body; that as long as germs are allowed to be scattered about they will find millions of victims who cannot resist them ; that the great victories for health that have been won in recent years have been won mainly by prevent- ing the spread of infectious diseases, and that more can yet be done for the health of the world by fighting germs than in all other ways combined. Physiological diseases. The causes of many of the ailments classed as physiological diseases on page 233 are not well understood ; some of them, like cancer, may yet prove to be germ diseases ; others are due to wrong chemical changes in the body that as yet we cannot remedy ; a third great group of the most important of them are connected with the degenerative changes in the tissues described on page 214, and with other kinds of degeneration which we shall not attempt to explain. These degenerative changes take place most fre- quently of all in the walls of the arteries and in the tissues of the kidneys and heart. Because of their great importance and because there is hope that in a 240 PRIMER OF PHYSIOLOGY measure at least they can be prevented, we shall discuss the causes of these diseases. The causes of degeneration of the tissues. The de- generative changes in the tissues are to be looked on as the wear and tear that takes place in the machine. They are the same changes that are found in old age in fact, they are old age. It is probable that anything that injures the health of the body in any way hastens these changes, and hurries us into old age faster than we otherwise should go. The following causes, how- ever, are agreed on by most medical men as being di- rectly responsible for many of these tissue changes : Ac2ite infectious diseases. After severe cases of diph- theria, scarlet fever, measles, pneumonia, grip, meningitis, typhoid fever, and other infections, degenerative changes have been found in the arteries of even young children. With the knowledge that we now have it is possible to prevent practically all of our acute diseases, and every one ought to be protected from them. Chronic infectious diseases. In the diagram on page 234, heart disease, Bright's disease, and diseases of the arteries are shown as physiological diseases. It would perhaps be better to call them germ diseases ; for in recent years it has been found that nearly all cases of them are caused by slow-growing varieties of germs. The two great methods of defending ourselves against these diseases are to give attention to the teeth, tonsils, nasal sinuses, or other parts where the germs have made a permanent home, and to live a hygienic life so that the resistance to the germs will be built up. Intestinal toxins. These toxins when injected into the blood of animals cause the degenerative changes in REALIZING HEALTH POSSIBILITIES 241 the tissues which we have described. There is little doubt that when they are absorbed into the blood from the intestines they have the same effects, and that they are one of the greatest of all causes of the diseases that we are discussing. Alcohol. Users of alcohol suffer exceedingly from these changes in the arteries, kidneys, and heart. The effect of the alcohol often shows itself but little until middle life, when the drinker suddenly finds that the organs which must keep up the circulation of his blood and excrete the poisons from his body have already reached old age (see footnote, page 213). The possibilities of health and long life. Ninety-five per cent of all human beings come into the world with sound and healthy bodies. Is it necessary that these bodies shall suffer from disease ? There are prophets of health who look forward to the day when men shall pass from birth to old age without sickness or pain. Is it necessary that our cells and tissues shall grow old and wear out ? Probably, yes, but with proper care of the body the passage of time works comparatively slight changes in the tissues and with the knowledge that we now have it would be possible to extend the average life far beyond the limit that it has yet reached in the most advanced countries in the world. Within the lifetime of men and women who are now at middle age, more has been done to free mankind from the bondage of disease than was accomplished in all the previous history of the world. Still greater hygienic discoveries are almost in sight ahead of us, and no one can estimate the health possibilities that lie before the boys and girls of today. Three hundred years ago the 242 PRIMER OF PHYSIOLOGY average human machine in Europe lasted twenty years today it lasts forty years ; intelligently cared for accord- ing to the knowledge that we now have it would prob- ably last seventy years. To what limit new hygienic dis- coveries and careful hygienic living will extend the life of this wonderful machine, the future alone can reveal QUESTIONS Explain what is meant by the limiting factor in crop raising. Discuss the limiting factor in health. Into what two classes may diseases be divided ? What is the trouble in each case ? Name some of the more important diseases belonging to each class. What are disease germs ? How do they injure the body ? What proportion of the deaths in the United States is due to germ diseases ? What additional damage is often done by them? In what two ways are we protected against germs ? What are opsonins? How may the amount of an opsonin or of a germicidal substance in the blood be increased ? What is done in vaccination ? Is good health sufficient to protect against germ diseases ? Give some facts supporting your answer. Why does a strong condition of the body assist in recovery from germ diseases ? In what kind of germ diseases is the general health of the body especially important ? What is the only method of avoiding germ diseases ? What organs of the body are most often affected by degen- erative changes in the tissues ? Give four causes of these changes. SUGGESTIONS TO THE TEACHER How to Live (Funk & Wagnalls), authorized by the Hygiene Ref- erence Board of the Life Extension Institute, Inc., and prepared by Fisher and Fisk, gives the best available discussion of the topic- treated in this chapter. APPENDIX The values appearing in the last column of the table on page 244 have been secured by the use of the formula given in Murray's Economy of Nutrition (Appleton). This author finds that on an average a pound of protein costs about 20 times as much as a pound of carbohydrate. The value of a food may therefore be said to be equal to the protein x 20 -f f at x 4 -f carbohydrates. The method of making the computations will be understood from the following sample problem in which the relative values of pecans and of an equal weight of dried figs are calculated. Pecans (as purchased) contain 5.1 per cent protein, 37.9 per cent fat, and 8.2 per cent carbohydrates. Dried figs contain 4.3 per cent protein, .3 per cent fat, and 74.2 per cent carbohydrates. The rela- tive values of these two foods may therefore be expressed by the equation 5.1 X 20 + 37-9 X 4 + 8.2 = 261.8 = 4.3 x 20 + .3 X 4 + 74-2 "" 161.4 ~ That is, a pound of pecans ought, theoretically, to sell in the market for 1.62 times as much as a pound of figs. In the table on page 244 the value of bread is taken as i, and the other foods are compared with it. The value of any two foods can be compared in this way, and it can then be deter- mined which is the cheaper at current market prices. The teacher will understand, however, that in determining the real value of an article of food there may be many factors not taken into account in the above formula. Bulletin No. 28 of the United States Department of Agriculture contains a very complete list of analyses showing the chemical composition of American foodstuffs. It is sold by the Superintendent of Public Documents, Washington, D.C., for five cents. 243 244 PRIMER OF PHYSIOLOGY l avaag dO XHOI3AV ivnbg KV HJ.IAV aaavawoD aasvHDana sv aooj do f^ l^N O CO O ON M O N CO O O * CO ON rfco -> f> O O VO "O ON ON -i ~ UOJJ m vo o co O -i t^ ro 8 888 O O O o 'd) sruoqdsoqj ON O O fO N O OOO C5OM (0*51) fOD) UIUIDIB3 CO Tj- N Ll-l O ^t" ^" O 1 - 1 O ON ooo <-> o- ooo 3BJ ^ o\ 1 1 T^- fO CS LT> 6 Ot^O-itv. O-iO^^O O ^O CO CO M ^ ^^ ^ N 6 UI3JOJJ rj-oo ON O O l^ LOCO *H H- CO-iCO-t^ COtOCO-iON ONfOfO u-> 1 r^ 1 06 *^oo $,^e r i '^p^^ fo32,s 8 1! -^TS$i ^s^'ss ^1^^ Q-. rtU 1-33 (JJ JT^ ^C ^C _1-^ O O ^ ^JO <^p3CQnQpQ PQP5PQPQCQ UUUUU UUQW APPENDIX 245 ?^ t-i COVO \O Lr> O LO N Tj- O< u-> i VO o ON co r>. COONCOCO o t^ o O Iv O M OO ONOO ON co to ^-O c^ ci ^t **"* ON O O O on 88 8 8 8 888 8 888 888 ci co O OO M ro T(- LT> - OM- O M Nn*>O i tr> ^3- ON ir> ^ O roc t i O O^ O*^ ^^ ^^OC^ C^C^^^OO %$<&. HLO vOrhcOl^.O OOOThLr>Lor(- CSOO OCO>-OTJ-M OOONQCO-^- O\ w >-< N O fvO M C^ covO vOO ^- MvO OO ON N O O nooo o o-o o-oo- -oooo OOOON- M ON O 00 I ^ N ^nvC - ^ - T^CO ONOONHH CO ^ covO OO 6 6 v6 - od I ON co n Nconvo q "*>! f ? r ? r ?..- |t^66od -ONO6| roOOOO") CO CO co ON- VO VO-VOOOOO vOconoO"< vOO-"* ONvO O vO -i O n oo n O vO oo vq t^. "t co r] vq od ri co r^ 6 06 t> OO VO 1^ 't HH rj- LorOco fO vqcococOco^> \ o>6o6o>N ^NcJooTJ-cJ 00 oo vo t^vo cs HH HH ONOO ON M3 N M N i- o t^ 4- I co o o 1 1 ^ ^ G p ^ en y. L* o en tn ^^ / ) 3 ^"^ ^ ^ flj fl SoCG cn^rtrtG *t/5 necessity for, 60,* 61,* 64; open-air schools, 65,* 66,* 67,* 68; open-air sleeping, 60,* 68. Ventricles, 41,* 42, 43.* Vermiform appenolix, 146,* 150. Vertebra, 18.* Vim, 149. Vision, testing, 117,* 121; defects of, 115, 116. See also Eye. Vitamins, 143-144. Windows, in schools, 119. Wounds, care of, 223, 224.* Yeast, 211. 51,569? QP3? UNIVERSITY OF CALIFORNIA LIBRARY